Review Article O -andSnO -Based Thin Film Ozone...

Review ArticleIn2O3- and SnO2-Based Thin Film Ozone Sensors Fundamentals

G Korotcenkov1 V Brinzari2 and B K Cho1

1Gwangju Institute of Science and Technology Gwangju 500-712 Republic of Korea2State University of Moldova 2009 Chisinau Moldova

Correspondence should be addressed to G Korotcenkov ghkoroyahoocom and B K Cho chobkgistackr

Received 22 December 2015 Accepted 11 February 2016

Academic Editor Eduard Llobet

Copyright copy 2016 G Korotcenkov et alThis is an open access article distributed under the Creative CommonsAttribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The paper considers SnO2and In

2O3thin films as materials for the design of solid-state conductometric ozone sensors in depth

In particular the present review covers the analysis of the fundamentals of SnO2- and In

2O3-based conductometric ozone sensor

operationThemain focus is on the description of mechanisms of ozone interaction withmetal oxides the influence of air humidityon sensor response and processes that control the kinetics of sensor response to ozone

1 Introduction

Ozone is a highly reactive form of oxygen The moleculesof ozone contain three oxygen atoms (O

3) and are unstable

with respect to O2 A certain amount of ozone is produced

in the troposphere in a chain of chemical reactions involv-ing hydrocarbons and nitrogen-containing gases Thoughozone is a minor atmospheric constituent with an averageconcentration of about 3 ppmv (parts per million volume)this gas plays great role in our life The ozone layer pro-tects life on Earth from ultraviolet solar radiation and isa significant contributor to the radiative energy balance ofthe atmosphere Most of the atmospheric ozone (90) islocated in the stratosphere with a maximum concentrationbetween 17 and 25 kmThismeans that ground concentrationof ozone is considerably smaller than in the stratosphereHowever this situation started to change during last decadesThe increased level of ozone in the atmosphere is a resultfrom the interaction between sunlight and various chemicalsemitted into the environment by industrial means Automo-biles can significantly affect ozone measurements as wellThe oxides of nitrogen emissions can be catalyzed by thesummer sun resulting in ozone alerts Thus ozone near theground is a product of industrial and urban pollution Inaddition in the last decade considerable interest was shownin ecologically clean ldquoozonerdquo technologies [1ndash3] (see alsohttpwwwio3aorg and httpwwwioa-ea3gorg) It wasestablished that ozone can be widely used in medicine as

well as in different technological processes [4ndash10] Due toits special characteristics ozone can be applied in industriessuch as pharmaceuticals food textiles and chemicals as wellas in water preparation medical treatment deodorizing andthe purification of gases (Figure 1) For example ozonationwhich is an effective technique for sanitizing ultrapure waterand treatment systems was introduced in the semiconductorindustry over 30 years ago Unlike other agents such aschlorine or chromic acid ozone oxidation is not accompaniedby the appearance of toxic waste since this process generatesonly oxidation products and oxygen Ozone can be usedfor the improvement of organoleptic qualities bleachingiron and manganese elimination from water the reductionof organic substances in suspensions and the eliminationof toxic compounds Because of its relatively short half-life ozone is always generated on-site by ozone generatorswhich usually use UV light and corona discharge for ozonegeneration

However it has been established that high concentrationsof this powerful oxidizing gas in the ambient atmosphere arehazardous to human health [11ndash13] A high level of ozonegas in the atmosphere is harmful to the human respiratorysystem causing inflammation and congestion of the respira-tory tract An individual who remains in a 01 ppm O

3

environment for two hours will sustain a loss of 20breathing capacity and after remaining in 1 ppm O

3for six

hours will suffer an attack of bronchitis A mouse kept in10 ppm O

3will not survive It is necessary to note that

Hindawi Publishing CorporationJournal of SensorsVolume 2016 Article ID 3816094 31 pageshttpdxdoiorg10115520163816094

2 Journal of Sensors

Ozonersquos advantages

Ozone is nativeecology clean oxidizer

Ozone annihilatesbiologically active

components in air and waterPreservation

of food

Cleaning and airdeodorization

Prevention of boththe mold and fungi

appearance

In contrast to chloride the useof ozone is not accompanied

by generation of thecarcinogenic substances

Ozone oxidizes heavy metalsand transforms sulphides and

nitrides in insoluble state

Annihilationof bad odor

Ozone therapy

Purification and disinfectionof air water and food

Possible fields of application

Food industry Environment control

Pharmaceutical industry

Water treatment

Chemical industry

Medicine

Figure 1 Advantages and possible fields of ozone applications

ozone due to its relatively short half-life (minutes in con-fined spaces) does not instantly diffuse in air to create auniform concentration for easy measurement Thereforein order to control the ozone concentration in the atmo-sphere and surrounding environment it is necessary todevelop both effective and economical methods and devicesfor the continuous monitoring of ozone concentrations atmultiple locations including technological processes withincorporated ozone treatments These methods are alsoneeded to determine attenuation of the ozone layer by man-made gases to validate model estimations of changes inozone layer and to confirm the efficiency of the MontrealProtocol on Substances that deplete the ozone Layer (httpozoneuneporgpdfsMontreal-Protocol2000pdf) As is wellknown in recent decades there has been the depletion of theozone layer which can negatively affect the life on EarthTheincrease in the number of articles devoted to the developmentand research of ozone sensors (see Figure 2) confirms theimportance of this issue Experiments have shown that ana-lytical techniques developed to solve these problems shouldbe capable of measuring ozone concentrations in the rangeof 001ndash10 ppm for these purposes For example ambient airmeasuring at the ground requires instruments with little ppbaccuracy in a range 20ndash200 ppb whereas in industrial andcommercial applications the precision is not so stringent andthe expected concentrations are higher (up to 10 ppm)

Num

ber o

f pub

licat

ions

120

110

100

90

80

70

60

50

402000 2005

Year2010 2015

Figure 2 The growth in the number of publications devoted to thedesign of ozone sensors Data extracted from Scopus

At present a number of conventional analytical methodssuch as UV absorbance optochemical optical chemilumi-nescence fluorescence and electrochemical methods areavailable for the accurate analysis of ozone concentration inthe air [14ndash17] However these sophisticated high accuracytechniques are advisable for application in both metropolitan

Journal of Sensors 3

Table 1 Comparison of main types of sensors which can be used for ozone detection

Type of sensors Detectionlimit ppb Advantages Disadvantages

OpticalUV absorbanceUV-LIDAR technique

1ndash3020ndash200

Absolute measurements reliability RToperation good selectivity high accuracyquick response high resolution highmeasuring range long life time acceptablefor stationary instruments

Need UV source interference from some organicsand mercury rather large size fairly expensiveper unit This makes it very difficult if notimpossible to design cheap portable device for insitu monitoring in real-time distribution of ozoneconcentrations within large geographic areas

Optochemicalchemiluminescencefluorescence 7ndash10 High sensitivity RT operation

Need fuel and light source fairly expensive perunit the broadband character of luminescencespectra as well as the ubiquitous presence ofnaturally fluorescent compounds leadsluminescence sensors to suffer from a critical lackof selectivity sensitive to temperature fluctuationsand other environmental factors that quenchfluorescence

Electrochemical 50ndash100

Low-power consumption RT operationresponse is relatively quick high accuracymonitoring is continuous high sensitivityinexpensive and compact device acceptablefor portable and fixed instruments

Less selective than optical technologies sensitiveto toxic gases and oxygen have limitations inconditions of exploitation (temperature pressureand humidity) short life time at highconcentration of ozone drift is possible needcalibration not fail-safe

Chemicalchemical titrationdiffusive and pumpedozone badges

20ndash200Inexpensive simple easy to use RToperation

Low sensitivity it is not selective it is not acontinuous monitoring process tapes havelimited life span and must be stored properly incontrol conditions

Polymer-based gt1000Small size RT operation low consumablepower good sensitivity acceptable forportable instruments

Commonly not selective some polymers reactstrongly to water vapor degradation under UVirradiation and ozone influence drift is possibleneed regular calibration

Conductometricmetal oxide (MeOx)heated

5ndash10

High sensitivity to ozone fast responselow-cost robust small size wide operatingtemperature range resistant to corrosiveenvironments long operating life compactand durable acceptable for portableinstruments

Commonly not selective drift of operatingcharacteristics is possible need regularcalibration nonlinear response need oxygenhigh enough power consumption not fail-safe

and industrial urban areas under conditions of relativelyhigh atmospheric pollutant concentration that are close toWHO guidelines Moreover as a rule these methods arebased on periodic air sampling and analysis of the sampleswith rather large and expensive stationary analytical devicesTherefore it is very difficult or even impossible to track thedistribution of ozone concentrations within large geographicareas in real time In addition the conventional analyticalmethods do not provide enough sensitivity for the detectionof small concentrations of ozone inmany cases [14 16] Solid-state conductometric gas sensors discussed in the presentpaper were designed especially for these purposes Resultsof comparative analysis of the methods used for ozonemonitoring are shown in Table 1

2 Solid-State Conductometric Gas Sensors

The main advantages of solid-state conductometric gas sen-sors are ease of fabrication by using thin and thick film

technologies simple operation and low production costsbecause the materials and manufacturing techniques easilylend themselves to batch fabrication [18] This means thatwell-engineered metal oxide conductometric sensors canbe mass-produced at a reasonable cost Reversibility rapidresponse longevity and robustness are other merits of metaloxide gas sensors Moreover these sensors are compact anddurable therefore they have very good suitability for thedesign of portable devices [18 19] This compensates fortheir disadvantages such as low selectivity and temporaldrift and opens great opportunities for using them inalarm systems and portable instruments including devicesfor balloon-borne atmospheric O

3profile-sounding [20]

electronic noises [21 22] and sensor networks for air pol-lution monitoring with wireless communication [23] Thuscompared to the reference methods discussed in the previoussection the use of low-cost conductometric ozone sensors formonitoring ambient air and technological processes wouldreduce air pollution monitoring costs and would also allow


Table 2 Conductometric-type ozone sensors and sensing materials used for their design

Sensor type or principle of operation 119879oper∘C Sensing materials

Pseudo-Schottky diode RTndash100 Pd (15 nm)Ge (20 nm)Pd (45 nm) on the p-type InP

Conductometric MeOx (heated) 200ndash400 In2O3 WO

3 SnO

2 ZnO MoO

3-In2O3 In2O3-ZnO-SnO

2 ITO NiO SmFeO

3

Ga2O3In2O3

RT conductometric MeOx RT CuCrO2 CuAlO

2 In2O3ZnOSnO

2 SnO

2-In2O3

Conductometric MeOx(UV photoreductionreoxidation) RT In

2O3 ZnO PtTiO

2-SnO2

Conductometric MeOx(UV assistance) RT In

2O3 SnO

2SWNTs

Conductometric (polymer-based) RTndash150 Copper phthalocyanine (CuPc) polypyrrole (PPy) InAcAc

Conductometric (I-D structures) RTndash300 Carbon nanotubes network In2O3 ZnO SnO

2

larger spatial coverage especially in remote areas wheremonitoring with traditional facilities is cumbersome Oneshould note that solid-state conductometric gas sensors canbe also used for controlling ozone concentration in waterThey can take advantage of the gas permeability of polymeror another suitable membrane to separate the heart of thesensor from the water This separation enables providing acontrolled environment for sensor operation while allowingozone to enter from the sample and react with metal oxidesurface General descriptions of conductometric gas sensorfabrication and operation can be found in review papers[18 24ndash32]

As shown in Table 2 at present many materials [1532ndash41] have been tested for the design of conductometricozone sensors and many various technologies such as sol-gel [42] laser ablation [35] sputtering [38] spray pyrolysis[43ndash45] RGTO [46] successive ionic layer deposition [47]vacuum evaporation [48] and solvothermal synthesis [49]have been applied for preparing gas-sensing layers basedon these materials Comparative evaluation of developedconductometric ozone sensors based on various metal oxidesis shown in Table 3 It is seen that many of the above sensorshave parameters suitable for practical use However in oursurveywe analyze conductometric ozone sensors designed onthe base of SnO

2and In

2O3thin films

21 Advantages of In2O3 and SnO2 for Ozone Sensor DesignOne should note that the first ozone sensors based on theoxides mentioned above were designed by Takada et al [7677] at the end of the 80s SnO

2and In

2O3are wide-band-

gap semiconductors which typically crystallize in the rutileand cubic structures correspondingly and they are by far themost studied and most successful semiconductor materialsfor gas sensors [19] including development of ozone sensors(see Figure 3) These sensing materials have advantages suchas high sensitivity fast response and good thermal and tem-poral stability Furthermore In

2O3- and SnO

2-based ozone

sensors also show very low cross sensitivity An experimenthas shown that sensitivity to O

3 even in the ppb range

was much larger than the response to NO2 CO H

2 SO2

and NH3in the tens of ppm range In

2O3and SnO

2also

provide the opportunity for miniaturization and integrationat micromachined substrates [14]

In2O3and SnO

2are gas-sensing materials since they are

conductive and possess the ability to donate electron densityto the adsorbed oxygenmolecules which arises primarily dueto bulk nonstoichiometry firstly within the oxygen lattice Ofcourse the reactivity of the metal oxide surface is criticallydependent on its doping the defect structure and the oper-ating temperature Possible oxygen anion states of adsorbedoxygen at the surface of SnO

2and their transformations can

be presented by the following scheme

O2(g) larrrarr O

2(ad)

eminuslarr997888rarr O

2

minus(ad)

VOlarr997888997888rarr Ominus (ad)

eminuslarr997888rarr O2minus (ad) larrrarr O2minus (lat) (1)

In this scheme (g) is gas (ad) is adsorbed and (lat) is latticeAll these transformations are thermally activated processesand as a rule are accompanied by charge transfer betweenadsorbed species and the conduction band of metal oxides(see Figure 4) [24 78 79] Thus the gas-sensing effectstrongly points to an intrinsic defect reaction such as oxygenvacancy (VO) or the cation interstitial (Sni Ini) mechanism

[80] As applied to the tin dioxide these reactions can bedescribed by the following schemes

O 999445999468 VO2++

1

2

O2+ 2eminus (2)

Sn 999445999468 Sni4++ 4eminus (3)


Table3Th

ebestp

aram

eterso

fcon

ductom

etric

heated

ozon

esensorsdesig

nedon

theb

aseo

fmetaloxides

Techno

logicalrou

teparam

eterso

fsensin

glayer

Maxsensorrespo

nse

Con

ditio

nsof

measurements

Respon

setim

eRe

covery

times

References

In2O3

Thickfilmdsim100n

mtsim12nm

sim3sdot102

85∘C

250p

pbdry

25ndash4

5sna

[35]

Thickfilmdmdashnatsim8n

msim15

sdot103

300∘C

100p

pbdry

sim1m

insim10min

[5051]


msim(4ndash6

)sdot103

350∘C

76pp

bna

na

[33]

Thickfilmdsim20

120583mtsim20

nm120

270∘C

1ppm

dry

na

na

[52]

Thin

filmsdsim

30ndash50n

mtsim10ndash15n

m103ndash104

200ndash

300∘C

1ppm

lt2s

(280∘C)

sim20

s(280∘C)

[4344

5354]

Thin

filmsdmdash

natmdash

na

sim102

400∘C

60pp

b100m

in(250∘C)

60ndash80m

in(250∘C)

[46]

Thin

filmsdmdash

natmdash

na

sim3sdot102

370∘C

230p

pbna

na

[55]

SnO2

Thickfilmdsim100n

mtsim15nm

sim(3-4)sdot

102

120∘C

250p

pbdry

40ndash6

0sTens

ofminutes

[35]

Thin

filmsdsim

30ndash50n

mtsim10ndash15n

m103ndash104

200ndash

300∘C

1ppm

lt2s

(280∘C)

sim15min

(280∘C)

[455657]

Thin

filmsdsim

260n

mtmdashna

sim102

350∘C

135p

pbSeveralm

inutes

Severalm

inutes

[5859]

Thin

filmsdsim

300n

mtmdashna

sim10

350∘C

60pp

bna

na

[6061]

Thin

filmsdsim

20ndash30n

mtsim6ndash

8nm

sim103

320∘C

1ppm

lt2-3s

sim15min

[47]

Thin

filmsdsim

40ndash50n

m119905lt6ndash8

nmsim105

150∘C

1ppm

3-4s

(200∘C)

sim17min

(200∘C)

[62]

WO3

Thickfilmdmdashnatsim15nm

sim60

0180∘C

1ppm

sim15s

sim2m

in[35]

Thickfilmdmdashnatmdash

na

sim35

400∘C

80pp

bna

na

[63]

Thin

filmsdsim

100n

mtmdashna

sim6sdot102ndash7

sdot103

120∘C

90pp

bsim12s

1ndash3m

in[64]

Thin

filmsdsim

35ndash50n

mtsim20ndash100

nm5ndash300

250∘C

08p

pm05ndash2m

in2-3m

in[65ndash69]

Thin

filmsdsim

300n

mtmdashna

sim20

300∘C

200p

pbMinutes

Minutes

[63]

Thin

filmsdmdash

natsim20

nm15

sdot103

300∘C

500p

pbna

na

[70]

ZnO


msim8

250∘C

01p

pm14s

9s[71]

Thickfilmdsim275n

m119905mdashna

sim10ndash30

200∘C

300p

pbsim10s

sim2m

in[72]

MoO3-TiO2

Thickfilmdmdashna119905mdashna

17370∘C

100p

pbsim20

sna

[73]

Fe2O3

Thin

films119889sim500n

m119905mdashna

sim20

200∘C

05p

pm50

na

na

[74]

SmFeO3


sim102

285∘C

04p

pmsim1m

insim10min

[75]

dfilm

thickn

esstgrainsiz

esensor

respon

se(119877

ozon

e119877air)con

ditio

nsof

measurements

temperature

ofop

eration

gasc

oncentratio

nandhu

midity


Other oxides

WO3

ZnO SnO2

In2O3

Figure 3The percentage distribution of the number of articles devoted to the study of metal oxide-based ozone sensors Data extracted fromScopus

Molecular-ionic species Atomic-ionic species

Ominus O2minus

O2

0 200 300 400 500

Temperature (∘C)

O2minus

100

Ominus + erarrO2minus

O2(gas) + SrarrO2(phys)

O2(phys) + erarrO2minus

O2 + erarr2Ominus

Figure 4 Literature survey of oxygen species detected at different temperatures on SnO2surfaces with infrared analysis (IR) temperature-

programmed desorption (TPD) and electron paramagnetic resonance (EPR) Data extracted from [24]

Analysis of the literature indicates that gas sensors are fab-ricated mainly using either ceramic or thick film technology[18] These sensors typically have a thickness of gas-sensitivelayer of more than 10 120583m However experiments have shownthat sensitivity to ozone in these sensors usually considerablyconcedes sensitivity to the ozone of the sensorsmanufacturedon the base of thin film technologies when the thicknessof gas-sensitive layer is not more than 300ndash500 nm [34 4260 81] At present the limited sensitivity of SnO

2- and

In2O3-based thin film ozone sensors is less than 5ndash10 ppb

Thin film sensors also have a faster response in comparisonwith thick film devices having a thickness exceeding a fewmicrometers [43 44 82] This is the reason that this reviewis devoted to ozone sensors with thin gas-sensitive layersSuch sensors can be fabricated using both the thin film andthick film technologies Studies have shown that after properoptimization of thick film technology this technology allowsforming such thin films

In [16] we began analyzing ozone sensors based on In2O3

and SnO2and carried out a detailed comparison of their

parameters In the present paper we continue consideringSnO2and In

2O3as materials for ozone sensor design In

particular the present review covers the analysis of the fun-damentals of ozone sensor operation including a descriptionof the mechanisms of ozone interaction with metal oxidesthe influence of air humidity on sensor response and theprocesses that control the kinetics of sensor response toozone One should note that the results of the analysisconducted in this review can also be used when consideringozone sensors developed on the basis of other metal oxides

22 In2O3- and SnO2-Based Conductometric Ozone SensorsAs indicated previously the conductometric ozone sensorsanalyzed in the present paper are the most used andstudied type of devices designed for the control of toxicand inflammable gases [83ndash89] In

2O3- and SnO

2-based


conductometric ozone sensors are usually planar devicesPlanar conductometric sensors have a simple structure [18]They consist of two elements a sensitive conducting layer andcontact electrodes Contact electrodes are often interdigitatedand embedded in the sensitive layerThe sensing layer (in ourcase In

2O3or SnO

2films) and electrodes can be fabricated

by a number of microelectronic protocols as ldquosingle-sidedrdquoor ldquodouble-sidedrdquo designs using thin and thick film tech-nologiesThe basis of conductometric sensor operation is thechange in resistance under the effect of reactions (adsorptionchemical reactions diffusion and catalysis) that take placeon the surface of the sensing layer [18 24ndash31] Chemicalspecies (ozone in our case) interact with the sensitive layerand due to the electron exchange between adsorbed speciesand the metal oxide modulate its electrical conductivity Thechange in conductivity is correlated to the concentration ofthe chemical species (ozone in air) and can be measuredusing DC voltage applied to the device Sensor response toozone is as a rule calculated as the ratio of the resistancesmeasured in the atmospheres containing and not containingozone (119878 = 119877ozone119877air)

For the activation of surface reactions that take placeduring gas detection conductometric ozone sensors operateat a high temperature as a rule [18] For this purpose gassensors have incorporated a resistive heater made usuallyin the form of a meander which dissipates the Joule powerPlanar sensors are very robust the temperature homogeneityover the sensing layer is good It is necessary to note thatthick film and thin film technologies are frequently combinedto produce planar ozone sensors especially in laboratoryinvestigations For example gas-sensing polycrystalline SnO

2

and In2O3layers may be prepared via thin film technologies

(eg spray pyrolysis magnetron sputtering laser ablationor chemical vapor deposition) while the heaters are formedwith thick film technology [18]

3 General Characterization ofIn2O3- and SnO2-Based ConductometricHeated Ozone Sensors

It was found that appreciable responses of both SnO2- and

In2O3-based ozone sensors arise at 119879oper gt 100∘C (see

Figure 5) [44 45]These responses were kept at an acceptablelevel in a wide temperature range of up to 400ndash450∘C Inmost cases the maximal response to O

3was observed at

119879oper = 200ndash350∘C This temperature range of maximumsensor response is typical for practically all SnO

2- and

In2O3-based ozone sensors developed independently from

fabrication technology used [33 34 41 51 55 58 90 91] It isimportant that other metal oxides such as n-ZnO p-CuOp-SrTi

1minus119909Fe119909O3 120572-Ag

2WO4 and Fe

2O3 have maximum

response to ozone in the same temperature range [74 92ndash94]For comparison the maximal response of undoped SnO

2-

and In2O3-based sensors to reducing gases (CO and H

2)

takes place at appreciably higher temperaturesmdash119879oper gt 400ndash450∘C (see Figure 5)

One should note that for the best In2O3samples (grain

size sim5ndash8 nm) the response to ozone can achieve 105ndash106

In2O3

Ozone

CO

40nm

70nm60nm

200nm

200100 400 500300

Temperature (∘C)

100

101

102

103

Sens

or re

spon

se

RH sim 45

Figure 5 Film thickness influence on temperature dependences ofIn2O3response to ozone (1 ppm) 119879pyr = 475∘C Data extracted from

[43 44 90]

even for 60 ppb of ozone [51] Of course such sensitivity isexcessive for real applications Sensorswith an extremely highresponse usually have a narrow range of detectable ozoneconcentration and poor stability due to strong sensitivityto the influence of outside factors such as air humiditytemperature interference and poisoning Experience hasshown that responsesim102ndash103 at 1 ppmO

3is the sufficient one

for market of ozone sensorsWe admit that there are also some papers that report

a maximum response to ozone in the range of 100ndash200∘C[33 35 42] However we cannot explain such a strongdistinction There is an assumption that the changing of thegrain crystallographic structure with corresponding changesof facets and point defect concentration could affect thisdistinction [37 97 98] In particular our experiments haveshown that the temperature of themaximum sensor response(119879oper(max)) depends strongly on the grain size depositiontemperature [45] and film thickness [57] In other words119879oper(max) depends on the parameters that influence theshape of the crystallites (ie crystallographic planes par-ticipated in gas-sensing reactions) The results of the XRDand TEM measurements confirm this fact [96 99ndash103] Inparticular the data presented in Table 4 show that thereare many crystallographic planes which can form facetsin crystallites and can therefore participate in gas-sensingeffects Models of several of the most stable SnO

2and In

2O3

crystallographic planes are shown in Figure 6 It can be seenthat every crystallographic plane is characterized by a spe-cific concentration and configuration of surface atoms (ieevery plane has its own specific electronic thermodynamicadsorption and catalytic properties) [80 97 103ndash105] Forexample according to the results of the theoretical simulationcarried out byAgoston [80] for In

2O3 (1) the surface stability

of stoichiometric In2O3surfaces increases in the order (111) gt

(011) gt (211) gt (001) (2) most stable surfaces ((111) and (011))do not exhibit significant stoichiometric variations whereas


Table 4 Crystallographic planes which can participate in gas-sensing effects

Metal oxide Planes which can form facets in crystallites ReferencesIn2O3 (010) (100) (111) (110) (001) (001) (101) (011) (111) (111) (111) (211) [110ndash112]

SnO2

(111) (200) (020) (112) (120) (110) (101) (011) (011) (101) (010) (001) (100)(110) (010) (010) (110) (100) (221) (221) (221) [99 112 113]

surfaces with polarity such as (001) can be significantlyoff-stoichiometric The largest stoichiometry variations takeplace for the (001) surfaces which partially resemble thechemistry of the (211) surfaces and step edges of the (111)surfaces (3) the chemistry of In

2O3surfaces depends on

orientation While most stable surfaces (111) and (011) arecharacterized by their chemical inertness up to low oxygenchemical potentials close to the material stability limit the(001) surfaces exhibit various surface phase transitions whichare sensitive to experimental boundary conditions In otherwords gas surrounding (4) hydroxylation of the polar (001)surface is effective in reducing the surface energy to valuescomparable to or even lower than those of other faces Thisis because water adsorption is relatively weak on the morestable (011) and (111) surfaces and locally restricted to a smallfraction of the total surface area Nevertheless dissociativewater absorption is still possible on those surfaces also Thesame can be said of the various crystallographic planes ofSnO2[37 97] These results indicate that an explanation

of the sensing properties of the oxide nanocrystals cannotbe simply provided in terms of the grain size effect [24106ndash109] but must also refer to the specific transducingproperties of the nanocrystal surface [37 51 97 98]Howevera large number of crystallographic planes which can besimultaneously present in the faceting of the crystallites thestrong dependence of crystallite faceting on the crystallitesize and the technological route used for crystallite synthesisor deposition complicate this task considerably [99 102 110ndash114] Perhaps only epitaxial films and nanobelts can be usedfor designing sensors in which only one crystallographicplane will work [97 104]

A distinctive feature of ozone sensors is the essential dif-ference in response (120591res) and recovery (120591rec) times observedfor dry atmosphere (see Figure 7) [43 56] Experimentshave shown that the response of In

2O3and SnO

2thin films

deposited by spray pyrolysis is very fast Even at 119879oper sim

200∘b the response time of sensors with optimal thickness(119889 lt 60ndash80 nm) in a dry atmosphere does not exceed 1-2 sec One should note that in a wet atmosphere the responsetime changes substantially [43 56 115] It was found thatthe influence of water increases strongly with the decrease ingrain size [109] and this influence depends on the operatingtemperature [56] In low temperature range the influence ofthe water vapors on the kinetics of sensor response intensifies[54]

Recovery ismuch slower (120591rec ≫ 120591res) and 120591rec is consider-ably weaker depending on the humidity of the tested gasFor comparison during the detection of reducing gases suchas CO and H

2 120591rec asymp 120591res [116] According to [117] the

indicated behavior (120591rec ≫ 120591res) is peculiar for the adsorp-tiondesorptionmechanism of gas sensitivity As is known in

(110)

(100)

(001)

(101)

SnO2

(a)

(111)

(100)

(110)

In2O3

(b)

Figure 6 Models of (a) unrelaxed (110) (100) (001) and (101) rutileSnO2surfaces and (b) relaxed (100) (110) and (111) bixbyite In

2O3

surfaces The large light balls represent tin or indium atoms andthe dark small balls oxygen atoms (a) Reprinted with permissionfrom [95] Copyright IOP (b) Reprinted with permission from [96]Copyright 2010 Royal Soc of Chemistry

Resp

onse

and

reco

very

tim

e (se

c)

Response

Recovery

Temperature of S(max)

103

102

101

100100 200 300 400

In2O3

SnO2

SnO2

∘C)Operating temperature (

Figure 7 The influence of operating temperatures on the responseand recovery times of In

2O3- and SnO

2-based sensors during ozone

detection in dry atmosphere Tested films were deposited at 119879pyr= 475ndash520∘C and had thickness 119889 sim 30 nm Data extracted fromKorotcenkov et al [53 56]


the case of reducing gas detection the response is controlledmainly by the catalytic reaction of oxidationThe necessity ofboth the time desorption increase and the time adsorptiondecrease of chemisorbed particles is one of the importantconditions for achieving the maximum response of solid-state gas sensors predicted in the frame of the adsorptionmechanism of gas sensitivity [117]The short adsorption timeand long desorption time correspond to the condition forhigher surface coverage of the adsorbed species of target gasand hence the maximum change in the electrical properties(ie resistance) at a given concentration of the target analyteIn full correspondence with this statement for both In

2O3

and SnO2ozone sensors we observe the fulfilment of the

following correlation

119878 sim (

120591rec120591res

)

119898

(4)

where 119898 = 10ndash15 [43 45] The bigger the 120591rec120591res ratio isthe greater the sensor response is However it is necessary totake into account that the increase in film thickness reducesthe difference between response and recovery times indicatedabove Additionally for thick films we have the trend of120591res rarr 120591rec [53] This means that the processes that controlthe kinetics of sensor response depend on the film thicknessand can be changed

Regarding the dependence between sensor signal andozone concentration we can say that as a rule thesedependences (see Figure 8) can be described with the powerequation [26]

119878 =

119877

1198770

= 119870119862119883 (5)

where 119883 and 119870 are constants 119862 is the ozone concentrationin the air and 119877

0and 119877 are stationary sensor signals in the

air without ozone and in the presence of ozone respectivelyUnfortunately the values of 119883 and 119870 are not constantfor various sensors For example in the literature on 119883one can find that values have varied from 02 to 15 [5055 123 124] Experimental studies and phenomenologicalmodeling have shown that the power exponent 119883 canin principle be derived from the mass action laws andrate constants of the respective surface reactions and therelationship between the sensor resistance and the trappedcharge density of chemisorbed species [25ndash27 125ndash127] Inpractice however this derivation is complicated because therelationship between the resistance and gas concentrationdepends not only on the surface chemical reaction butalso on the morphology of the sensor such as a compact(nonporous) thin film or porous thick layer and on itsmicrostructure (the grain size the neck area between partiallysintered grains the inhomogeneous distribution of the grainsize the pore size and other microstructural features) [2430 128ndash130] Thus the present situation with a great rangein 119883 values means that firstly the metal oxides studiedin different laboratories as ozone-sensing materials have asignificant difference in structure and second the responseof sensors fabricated in different labs can be limited by variousprocesses

11

8

3

2

6

4

9

12

107

13

1

5

001 01 10 10Concentration (ppm)

Ozone

100

101

102

103

104

105

Sens

or re

spon

se

Figure 8 Sensor signal dependences on the O3concentration

determined for devices designed in different labs 1 In2O3(sol-gel

+ drop coating technologies 119905 sim 35ndash8 nm 119879oper = 300∘C) [50] 2In2O3(sol-gel + spin coating technologies 119879oper = 235∘C) [33] 3

In2O3(laser ablation 119889 sim 20ndash50 nm 119879oper = 330∘C) [34] 4 In

2O3

(sol-gel 119905 sim 12 nm 119879oper = 235∘C) [118] 5 In2O3(mesoporous UV

illumination 119879oper = RT) [119] 6 In2O3(sol-gel + screen-printing

technologies 119879oper = 235∘C) [33] 7 SnO2Pt (2) (laser ablation

119879oper = 120∘C) [35] 8 In2O3Fe (3) (CVD 119879oper = 370∘C) [120]

9 In2O3(MOCVD 119905 sim 7ndash12 nm UV illumination 119879oper = RT)

[121] 10 In2O3(laser ablation 119879oper = 84∘C) [35] 11 In

2O3(sol-

gel 119879oper = 200ndash300∘C) [14] 12 In2O3(MOCVD UV illumination

119879oper = RT) [15] 13 ITO (3 Sn) (sol-gel + dip-coating technologies119889 sim 01ndash02 120583m 119879oper = 360∘C) [122]

4 Mechanism of Ozone Interaction with MetalOxide Surface in Heated Ozone Sensors

One should note that until now the sensing mechanism ofoxidizing gases such as O

3 has been a matter of debate

[53 54 58 123 131ndash134] Due to the acceptor character ofthe surface state induced by the O

3chemisorption (these

states can trap significant amounts of electrons from theconduction band) ozone ionosorption is accompanied byan increase in negative charge at the surface of an n-typesemiconductor and an increase in band-bending (119902Δ119881

119878gt 0)

For an n-type semiconductor this results in the creation ofa depletion layer at the surface of the metal oxide grainsand a decrease in the conductance of intercrystallite barrierswhich control the conductivity of polycrystalline materials[1198660sim exp(119902119881

119878119896119879)] In this case the sensor response can

be expressed as

119878 =

119866

1198660

sim exp (119902Δ119881119878

119896119879

) lt 1 (6)


O

O

+

minus

O O O

O

+

minus

Figure 9 Resonance Lewis structures of the ozone molecule

where 1198660and 119866 denote the surface conductance before and

during oxygen ionosorption respectively The mobility ofcharge carries changes slightly in comparison with concen-tration [52]

The analysis of possible chemical reactions of In2O3and

SnO2with ozone [55 58 60 123] allows the proposal of the

following reactions which give the clearly expressed acceptorcharacter of ozone interaction with metal oxide

O3(g) 997888rarr O

3(s) + eminus 997888rarr O

3

minus(s) (7)

O3(g) 997888rarr O


2(g) +Ominus (s) (8)

In this reaction eminus is a conduction electron in the oxidefilm Ominus(s) and O

3

minus(s) are surface oxygen ions and O3(g)

and O2(g) are the adsorbing ozone and desorbing oxygen

molecules respectivelyHowever by analogy with O

2 which has a larger dis-

sociation energy than O3[123 135] but already adsorbs

dissociatively at the surface of SnO2at 119879 gt 150ndash180∘C [86

136] we believe that at 119879oper gt 100ndash150∘C reaction (8) (iedissociative O

3absorption) is preferred [60 123] The same

statement can be found in [42 123] It is known that ozone is ahighly unstablemolecule that readily donates its extra oxygenatom to free radical species The geometry of the ozonemolecule is such that it has a significant dipole moment andthe central oxygen atom has a lone pair of electrons In otherwords the central atom possesses a positive charge and oneof the side atoms possesses a negative charge (see Figure 9)Therefore it is quite reasonable to assume that this atominteracts with the metal oxide surface and forms an acceptorwhereas the other two atoms form an oxygen molecule thatreturns to the gas phase as shown in reaction (8)

This statement finds confirmation in the results reportedin [123 136 137] which demonstrate that molecular O

3was

observed at the surface of metal oxides at 119879 lt 300K only Ata higher temperature O

3was not stable As is known ozone

has significantly lower dissociation energy than oxygendissociation energies for ozone and oxygen are 11ndash13 eV and51 eV respectively [138 139] There is only one investigation[140] that has shown the formation of O

3

minus on the metal oxidesurface (CeO

2) interacting with ozone at temperatures below

65∘CMoreoverO3adsorption in the formofO

3

minus should leadto the formation of localized dipoles on the surface [91 141]However additional signals derived from directed dipolelayers adsorbed at surface states were not observed in In

2O3

interacting with O3 even at 130∘C [91 141] One can assume

that similar to oxygen ozone dissociatively adsorbs on thereduced surface cations of Sn (Sn2+) and In (In2+) [78 142]As is known [31 143] the active sites of adsorption on ametaloxide surface are coordinatively unsaturated metal cationsand oxygen anions Metal cations as electron-deficient atomswith vacant orbitals exhibit Lewis acid properties whileoxygen anions act as a base A schematic diagram illustrating

Sn Sn Sn

O

O O

O + O2O3

Figure 10 Schematic diagram illustrating process of O3dissociative

adsorption at the surface of SnO2in dry air Idea from Bulanin et al

[136]

this process for SnO2is shown in Figure 10 It is important

to note that in addition to Lewis acidity metal oxides alsopossess Broslashnsted acidity which is defined as the ability toprotonate bases (H+-transfer) [31] This type of acidity is theresult of the dissociative adsorption of watermolecules on theoxide surface for forming protons (H+) and hydroxyl groups(OHminus) The driving force of these processes is the interactionbetween a Lewis acid (cation on the metal surface) and itsconjugate base (the oxygen atom in a molecule of H

2O) A

proton (Lewis acid) formed as a result of this dissociation iscaptured and tightly binds the surface lattice oxygen atom ofthe metal oxide (Lewis base) while a hydroxyl group (base)is fixed to the metal cation (acid)

Of course the process of oxygen incorporation in themetal oxide lattice can also be involved in the reaction ofozone detection For example this reaction can be presentedusing the Kroger-Vink notation as the pathway

O3+ VO∙∙+ 2e 999445999468 OO +O

2uarr (9)

Equation (9) represents the exchange reaction of oxygenbetween the gas phase and the metal oxide lattice in whichthe predominant defects are oxygen vacancies As is knownoxygen vacancies are the main point defects in metal oxidesIn general as shown in (9) oxygen adsorption and incor-poration into the lattice decrease the free carrier (electron)concentration in n-type metal oxides However one shouldtake into account that reaction (9) for SnO

2is valid for

the bulk of the metal oxide only It was found that oxygenincorporation in the surface vacancies of the SnO

2lattice

is not accompanied by the capture of electrons from theconduction band [105 144]Thismeans that for the indicatedelectron exchange the process of oxygen incorporationshould be accompanied by bulk diffusion However exper-iments related to the study of metal oxides such as SnO

2

TiO2 and SrTiO

3 have shown that in the temperature range

below 500∘C the incorporation reaction of the adsorbedoxygen atoms into the lattice (ie bulk diffusion) is veryslow therefore the oxygen exchange reaction is effectivelyblocked [145ndash149] As a result the oxygen vacancies in thebulk are unable to equilibrate with oxygen from the gas phaseTherefore for most metal oxide conductometric gas sensorsthat operate in the temperature range between 100∘C and500∘C chemisorption is the dominant effect that controls thesensing mechanism as a rule Only at higher temperatures(typically above 500ndash700∘C) does the incorporation into thelattice of metal oxides become the dominant mechanismresponsible for the change of their resistance which takesplace due to the bulk oxygen diffusion DFT calculations of


the SnO2(101) surface support this conclusion suggesting a

self-limiting mechanism for the oxygen exchange reaction attemperatures below 400∘C [150] In this temperature rangeSnO2sensors show the maximum response to ozone

However it is important to note that the surface sto-ichiometry of metal oxides during interaction with a sur-rounding gas can be changed despite the invariance ofthe bulk stoichiometry In particular Korotcenkov et al[53 54] have used this approach based on surface reduc-tionreoxidation processes to gain an understanding of gas-sensing effects in In

2O3-based ozone sensors Korotcenkov et

al [53] believe that at 119879oper gt 119879th sim 120ndash150∘C the surfacestoichiometry and thus the electronic and surface propertiesof In2O3grains can be changed under the influence of the

surrounding atmosphere The threshold temperature (119879th)corresponds to the temperature below which the oxygen canonly be adsorbed on the surface of indium oxide withoutincorporation into the lattice These results are in agreementwith the data reported byHimmerlich [151]Himmerlich [151]did not observe oxygen incorporation in the In

2O3lattice at

room temperature either Moreover he has shown that theIn2O3band gap in the surface layer can be changed under

reductionreoxidation reactionsOne should note that the maximal sensitivity of SnO

2-

and In2O3-based sensors to ozone is observed in a tem-

perature range when the surface of metal oxides is freefrom molecular water (119879 gt 100∘C) and the concentration ofchemisorbed atomic oxygen at the surface of metal oxide isstill low [45 56] A diagram illustrating the change of thesurface species concentration on the SnO

2surface is shown

in Figure 11 Such a situation seems natural to us becausemolecular water apparently blocks the sites for dissociativeozone absorption or transforms ozone into another form Forexample earlier in [152] it was reported that SnO

2surface

dehydroxylation is required to obtain an increase in thesurface coverage of charged oxygen species adsorbed at thespecific surface sites Bulanin et al [136] also found thatthe adsorption of water in the case of a totally hydratedCeO2surface completely poisoned the sites of molecular

O3chemisorption It is also known that the interaction

between the oxygen of water and the central oxygen of ozoneproduces a stable H

2O-O3complex [153] The necessity of

a low initial concentration of chemisorbed oxygen is alsounderstandable because this value determines the possiblerange of the surface charge change (ie the change of surfacepotential (119881

119878) during interaction with ozone) As is known

the concentration of chemisorbed oxygen controls the initialband-bending of metal oxides In addition the presence ofinitial chemisorbed oxygen at the surface of metal oxides caninitiate reaction (10) which also reduces a sensor responsethrough the consumption of the ozone part involved insurface reactions Consider the following

O3(g) +Ominus (s) 997888rarr 2O

2uarr + eminus (10)

We believe that increased operation temperature alsoresolves the problem of the surface carbon Certainly in realconditions black carbon [the energetic position of the C1s

OH

R(air)

Con

cent

ratio

n (a

u)

Ozone

S

O2

H2O

O

100

101

102

103

Sens

or re

spon

se

100 200 300 400 5000Operation temperature (∘C)

105

107

109

Resis

tanc

e (O

hm)

Figure 11 Diagram illustrating processes taking place at the SnO2

surface during ozone detection (1) film resistance in air (2) filmresistance in atmosphere containing ozone (3)ndash(5) surface con-centrations of molecular water molecular oxygen and OH-groupscorrespondingly (6) initial surface concentration of chemisorbedoxygen (Ominus) determined by oxygen dissociative adsorption (7) pos-sible addition of chemisorbed oxygen due to dissociative adsorptionof ozone 119877(119879oper) measurements were carried out for SnO

2films

deposited at 119879pyr = 320∘C Adapted with permission from [116]Copyright 2004 Elsevier

peak corresponds to the highly ordered pyrolytic graphitephase of carbon] is present in high concentrations at thesurface of metal oxides According to [154 155] the surfaceconcentration of carbon at room temperature correspondsto 05ndash08 of monolayer Annealing in a vacuum decreasesthe surface concentration of carbon However in the air theinitial concentration of carbon is restored even at room tem-perature The correlation established by Brinzari et al [154]between carbon surface concentration and peak intensities(Sn3d and O1s) corresponding to SnO

2lattice atoms has

shown that the intensity of the Sn3d peak has a strongerdependence on the surface concentration of carbon species incomparison with O1s (see Figure 12) Such different behaviorallows the assumption that the carbon on the SnO

2surface is

bonded predominantly to SnSn which is also the adsorptionsite for the dissociative adsorption of ozone This means thatcarbon is also a poison for O

3dissociative adsorption Ozone

exposure removes C-related contamination from the metaloxide surface including SnO

2and In

2O3[155 156] Inter-

action with ozone changes C-related compounds adsorbedonto themetal oxide surface into volatile species such as CO

2

or CO However at RT this process is comparatively slowExperiments have shown that even at a high concentrationof ozone (up to several vol) an equilibrium state can beachieved during several tens of minutes [156 157] Thusoperation at higher temperatures either increases the rate ofcarbon oxidation (ie its removal) or increases the rate ofCO2catalytic decomposition (ie the restoration of initial


O1s

Sn3d

(a)

(b)

30 40 50 60 70Surface concentration of carbon (au)

Inte

nsity

of X

PS (O

1s C

1s a

nd S

n3d)

pea

ks (a

u)

500

400

300

200

x 5

C1s

Vacuum Air15

10

5

0

O(ads)

100 300 500 A BTreatments (∘C)

SnO2

Figure 12 (a) Dependencies of intensities of lattice Sn3d and O1sXPS peaks on surface carbon concentration and (b) influence ofvarious thermal treatments on the intensities of O1s andC1s peaks ofSnO2X-ray photoelectron spectra (120593 = 90

∘) A dry air 119879an = 300∘C

119905 = 10min B humid air 119879an = 300∘C 119905 = 10min Data extractedfrom [154]

carbon coverage) and thus reduces the influence of theseprocesses on the kinetics of sensor response Himmerlich etal [158] have concluded that desorption of carbon speciesfrom the In

2O3surface activates existing defect sites for

interaction with gases such as ozone They have also foundthat this effect has a strong influence on the performance andsensitivity of indium oxide-based gas sensors

Regarding the recovery process during ozone detectionthis process is not as simple as it seems at the first glanceRecovery processes during interaction with ozone are usuallyconsidered the reaction of associate oxygen desorption

Ominus (s) +Ominus (s) 997904rArr O2(g) uarr + 2eminus (11)

It is clear that this process has the activation nature becausethe surface migration of oxygen atoms and electron exchangeare required for this reaction As is known the ionizedchemisorption is limited by the upper band-bending on thematerial surface [159 160] (often referred to as the Weiszlimitation in the sensor literature) Therefore the concen-tration of chemisorbed species cannot exceed 1 from thenumber of sites possible for adsorption In other words thechance of finding chemisorbed oxygen at the nearest surfacesites is very low This means that the rate of this reactionshould increase with increasing operating temperature anddecreasing band-bending However as shown in Figure 13the temperature dependences on recovery time especiallyfor SnO

2-based ozone sensors have at least two sections

with specific behavior At 120591rec = 119891(119879oper) the dependenceshave the activation character only at high temperatures Thismeans that the recovery processes in various temperatureranges have different natures We assume that in addition

1

2

3

4

Recovery

ResponseDry air

Wet air

qkT (eVminus1)

15 17 19 21 23 25 27 29

100

101

102

103

Resp

onse

and

reco

very

tim

es (s

ec)

450 350 250 150Operating temperature (∘C)

+ ozone (1ppm)Air

Figure 13 Influence of air humidity on response and recoverytimes (120591

05) during ozone detection by SnO

2thin film sensors (films

deposited at 119879pyr = 520∘C 119889 sim 30 nm) 1 and 2 wet atmosphere(sim35ndash40 RH) 3 and 4 dry atmosphere (sim1-2 RH) Adapted withpermission from [56] Copyright 2007 Elsevier

to the oxygen desorption described by reaction (11) thereactions such as (12) and (13)ndash(15) can also take place andcontrol the recovery time As is known the surroundingatmosphere contains sim05 ppm of H

2and sim2 ppm of CH

4

Ominus (s) +H2(s) 997904rArr H

2O uarr + eminus (12)

2Ominus (s) + CH4(s) 997904rArr C + 2H

2O uarr + 2eminus or (13)

Ominus (s) + CH4(s) 997904rArr CO uarr + 2H

2uarr + eminus (14)

Ominus (s) + CH4(s) 997904rArr CH

3+OH120575minus (15)

Data presented in [79 136 161 162] demonstrate thatreactions (12)ndash(15) are possible In particular Gatin et al [162]have studied the adsorption of oxygen and hydrogen at thesurface of a film consisting of SnO

2nanoparticles and have

found that molecular hydrogen even at room temperatureinteracted with adsorbed atomic (chemisorbed) oxygen withformation of watermolecules and band-bending changeThismeans that this reaction does not have a strong limitation inthe low temperature range Bulanin et al [136] have shownthat the atomic oxygen at the surface of TiO

2appeared due

to O3decomposition being able to interact with CO with

formingCO2even at 77K Tabata et al [79] have analyzed the

interaction of CH4with the SnO

2surface and found that Ominus

was consumed through the exposure of CH4at 200∘C The

effect of water which is present in the atmosphere cannotalso be excluded [45 54 56] According to reaction (16) theinitial state (the particle balance) can be recovered throughthe O

119878

minus transformation into hydroxyl groups

O119878

minus+H2O 997888rarr 2OH120575 + eminus (16)


1

2

6

2

4

0

39 36 33 30 27 24Photon energy (eV)

350 400 450 500 550300Wavelength (nm)

2

4

6

8

EL p

ower

at40

mA

(mW

)

Sens

or re

spon

seR

ozon

eR

air

Figure 14 1 Influence of photon energy on the response of In2O3-

based RT ozone sensors 2 spectral characteristics of GaInN QWLED The layer is irradiated by UV light in vacuum followed by anoxidation to the original state by means of exposure to O

3 Adapted

with permission from [177] Copyright 2010 Wiley-VCH

5 Room Temperature Ozone SensorsOperated under the Influence ofUV Illumination

At present there have been attempts to design SnO2- and

In2O3-based ozone sensors for operation at room temper-

ature (RT) [141 163ndash167] This type of ozone sensor hasrecently attracted great interest due to its advantages such aslow energy consumption and the possibilities of integrationinto plastic packages and portable devices [168] Howeverone should note that such sensors usually have very lowsensitivity slow response poor recovery features and highsensitivity to air humidity For example Epifani et al [165]reported that the response time of In

2O3-based ozone sensors

at room temperature can exceed 50min The involvementof UV illumination in the gas-sensing process considerablyimproves the operating characteristics of RT ozone sensors[15 169ndash172] Typical parameters of SnO

2- and In

2O3-based

ozone sensors operated at room temperature under influenceof UV illumination are listed in Table 5 For comparison thesame table contains information related to the parameters ofRT ozone sensors developed based on other metal oxides

Experiment has shown that indicated improvement of RTozone sensors takes place due to the strong decrease in theldquoinitialrdquo sensor resistance under the influence of UV illumi-nation As it is seen in Figure 14 to obtain a maximum valueof ozone sensitivity by In

2O3-based sensor a photon energy

higher than sim29 eV is required At photon energy largerthan 32 eV the ozone sensitivity remains nearly constantThus the photon energy of UV light from GaN-based LEDis acceptable for application in RT ozone sensors as shownin Figure 14 The similar situation is observed for SnO

2 For

significant photoconductivity effect the wavelength of theillumination should not exceed 400 nm [186]

50 200150 3000 100 350250

Time (min)

10minus5

10minus4

10minus3

10minus2

10minus1

100

101

102

Spec

con

duct

ivity

(Ωminus1

cmminus1)

Figure 15 Photoreduction in vacuum and oxidation in oxygen of a60 nm thick InO

119909film deposited by magnetron sputtering at room

temperature Reprinted with permission from [173] Copyright 2001American Institute of Physics

According to general model of photoreduction UVillumination with ℎ] gt 119864

119892(30ndash37 eV) generates electron-

hole pars in metal oxides The holes generated in the space-charge region are attracted to the surface and can be capturedby chemisorbed surface species such asO

2

minusThis process canbe described by the following schemes

ℎ] 997904rArr e119878

minus+ h119878

+ (17)

h119878

++O2119878

minus997904rArr O

2119878997904rArr O

2uarr (18)

In this scheme ℎ] represents an absorbed photon withenergy ℎ] The indicated process transforms oxygen speciesin the neutral form and thus facilitates their desorption (iethe photoreduction of the metal oxide) This process due toan increase of the bulk charge carriers because the electronof the hole-electron pair remains in the conduction band anda decrease of the height of the intergrain potential barrier isaccompanied by a strong decrease of metal oxide resistance[171] The magnitudes of photoreduction are proportional tothe UV light intensity As shown in Figure 15 the reduction atRT in the vacuum is fast This situation was expected firstlybecause the hole injection into the chemisorption states isan exothermic process and secondly the oxygen desorptiondoes not require additional reactions

As mentioned above the change in the resistance ofpolycrystalline metal oxide films is ascribed to the changein the barrier height at the intergrain interface Underthese circumstances the ratio of the resistance measured inthe dark and after UV illumination can be approximatelyexpressed in the form

119877dark119877UV

sim exp(119902ΔB119896119879

) (19)

where ΔB is the barrier height change Taking into accountpossible changes in the film resistance particularly datapresented in Figure 15 one can find that the reduction of


Table5Ty

picalp

aram

eterso

fRTozon

esensorsop

erated

usingUVph

otoreductio

neffect

Metaloxide

Techno

logyfilm

parameters

UVsourcecon

ditio

nsof

photoreductio

nMax119878

Con

ditio

nsof

measurements

Respon

setim

eRe

covery

time

References

In2O3

Thin

filmdsim20ndash110nm

tsim8ndash25

nmUVHglamp(254

nm)vacuum

sim105ndash106

RTsim

30ndash9

0ppb

na

na

[170171173174]

Thickfilm

(mesop

orou

s)dmdashnatsim30

nmUVLE

Dair(100∘C)

sim130ndash

350

PretreatmentRT

02ndash12

ppmdry

Minutes

25ndash53m

in[119175]

Thin

filmdmdashnatmdash

na

UVLE

D(375

nm)air(01P

a)sim4

RT25pp

msim10min

na

[169]

Thin

filmdsim20

nmtsim7n

mUVLE

D(375

nm)na

sim105

RT104p

pmMinutes

Minutes

[176]

Thin

filmdmdashnatsim7n

mUVLE

D(375

nm)air

sim5ndash12

RT03ndash1

ppm

Minutes

Minutes

[121163177]

SnO2

Thin

filmdsim450n

mtmdashna

UVLE

D(370

nm)air

13ndash14

RT10p

pm60

Minutes

Tens

ofminutes

[178]

Thin

filmdsim6ndash

9nmtmdashna

UVLE

D(385

nm)air

sim11

RT100

ppbdry

Tens

ofminutes

Tens

ofminutes

[179]


na

UVlight

(366

nm)air

26RT

25pp

msim50

min

sim4-5m

in[180]

PtSnO2


na

UVlight

(366

nm)air

885

RT25pp

msim6m

insim15

min

[180]

ZnO

Thin

filmdsim150ndash

1000

nmtsim5ndash11nm

UVHglamp(254

nm)vacuum

sim103ndash108

RTn

aTens

ofminutes

Minutes

[38181]

Thin

filmdmdashnatsim40ndash100

nmUVlamp(366

nm)air

UVlampair(580∘C)

sim12

sim103

RT25pp

m10min

1min

Minutes

5s(580∘C)

[182]

Thickfilmdmdashnatsim40

nmUVLE

D(400

nm)air

sim2ndash25

RT70p

pb50

5ndash10min

Minutes

[183]

ZnO-SnO2

Thickfilmdmdashnatsim20nanm

UVlight

(366

nm)air

39RT

25pp

msim2m

insim7m

in[180]

InGaZ

nOTh

infilmdsim65

nmtmdashna

UVLE

D(370

nm)air

14RT

2pp

m10min

gt30

min

[184]

TiO2


UVlight

(366

nm)air

64RT

25pp

msim1m

insim2m

in[180]


LED(460

nm)air

2RT

25pp

msim15

min

sim1m

in[185]

TiO2-SnO2


UVlight

(366

nm)air

327

RT25pp

msim3m

insim15s

[180]

Pt(TiO2-SnO2)(14)


UVlight

(366

nm)air

103

RT25pp

msim3m

insim1m

in[180]

WO3

Thickfilmdmdashnatsim16ndash20n

mLE

D(460

nm)air

64RT

25pp

msim1m

insim1m

in[185]

TiO2-W

O3


mLE

D(460

nm)air

1400

RT25pp

msim3m

insim8m

in[185]

Pt(TiO2-W

O3)(14)


mLE

D(460

nm)air

2700

RT25pp

m15min

15min

[185]

dfilm

thickn

esstgrainsiz

eSsensor

respon

se(119877

ozon

e119877air)con

ditio

nsof

measurements

temperature

ofop

eration

gasc

oncentratio

nandairh

umidity


the barrier height in the In2O3films under UV illumination

can reach sim03ndash04 eVAnother reason for increasing the RT sensor response

under the influence of UV illumination is related to theUV effect on O

3decomposition For example Chen et al

[187] established that the activity of metal oxides towardO3decomposition depends greatly on the surface properties

of the oxide the presence of irradiation and the relativehumidity They have shown that while 120572-Fe

2O3can catalyt-

ically decompose O3in the dark the TiO

2surface is deacti-

vated by O3exposure Under dark conditions the presence

of atmospheric water inhibits O3decomposition at room

temperature through the competitive adsorption of watermolecules and ozone for active surface sites In the presenceof UV radiation under dry conditions photoenhancementin O3decomposition was observed for both 120572-Fe

2O3and

TiO2 The presence of both water and UV radiation leads to

more complicated behavior In particular it was found thatthe UV irradiation of TiO

2leads to an initial increase and a

subsequent decrease in ozone uptake coefficients as the RH isincreased

It should also be taken into account that the joint actionof UV illumination and ozone stimulates the removal ofcarbon species [157 158] which contributes to the activationof the metal oxide surface As previously described thisprocess also occurs in the dark but is relatively slow andineffective as in the presence of UV illumination [156] In anozone atmospherewithoutUV light efficient surface cleaningrequires temperatures of approximately 200∘C

There are also suggestions that the effect of photoreduc-tionreoxidation on InO

119909films is related to the formation and

annihilation of oxygen vacancies in the film [188] Accordingto this mechanism UV irradiation transfers oxygen from abound to the gaseous state In the resulting vacancies the twoelectrons of the oxygen ion are left in the vacant site and cancontribute to the increase in the density of free carriers Thesubsequent oxidation in an ozone atmosphere contributesto the incorporation of oxygen into the film diminishesthe density of oxygen vacancies and therefore leads to adrastic decrease of the available charge carrier concentrationHowever for the implementation of this mechanism inpolycrystalline materials it is necessary to assume that fastoxygen lattice diffusion occurs even at room temperaturewhich is unlikely Therefore the majority of researchers areinclined to believe that the photoreductionreoxidation is asurface effect [170]

For UV illumination different UV Hg lamps [170] orGaN-based LEDs [163] can be used A typical photoreduc-tionoxidation cycle for the In

2O3minus119909

films is shown in Figures15 and 16(a) The processes of photoreduction and oxidationwere fully reversibleThedescription of themechanismof thisinteraction can be found in [119 131 172]

However experiments have shown that the sensitiv-ity comparable with that of conventional ozone sensorswas achieved only for sensors based on the photoreduc-tionreoxidation principles which operated using UV pho-toreduction in a vacuum or an atmosphere of inert gas Inthis case the photoreduction is carried out in vacuum butthe measurement of sensor response to ozone is conducted

001 01 1 10

100

10

100

(a)

UV

16012080400Time (min)

Resp

onse

tim

e (m

in)

(b)

15ppb

200ppb

25ppm

22ppm

92ppm

In2O3

O3 concentration (ppm)

O3

50

40

30

20

10

0

Resis

tanc

e (kO

hm)

Figure 16 (a) Room temperature resistance change in air of In2O3

films deposited by MOCVD (119889 sim 700ndash800 nm) at different ozoneconcentrations (b) Response times at different O

3-concentrations

For UV illumination InGaN-LED (120582 sim 375 nm) was used Dataextracted from [169]

in an atmosphere containing ozone at ordinary pressureSuch sensors based on films with thicknesses of less than100 nm had extremely high sensitivity to ozone of up to 105ndash106 even for the ppb range [15 170 171] It is important tonote that the maximum response was observed for the filmsdeposited at low temperatures Increasing both the depositiontemperature (see Figure 17) and the temperature of subse-quent annealing significantly reduced this response Sensorresponse strongly decreased also with increasing operationtemperature (see Figure 18) In all cases the decrease insensor response was due to the increase in the conductivitymeasured in the atmosphere of ozone

It is clear that the cycle of measurement mentionedabove is not convenient for real applications In addition theresponse in the low concentration range is especially slow (seeFigure 16) One should also note that when using this methodit is difficult to distinguish the influence of ozone and oxygenbecause reoxidation also occurs in normal atmosphere (seeFigure 15) albeit at a slower rate This approach also doesnot take into account the change in conductivity due tonet electron-hole generation which can be several orders ofmagnitude

For sensors operated in the usual atmosphere theresponse is subject to the same regularities that have beenestablished for photoreduction in the vacuum but the mag-nitude of the response did not exceed 6ndash10 for the ppm levelof ozone concentration [163 166 172 178] Only Wagner etal [119] reported the extremely high sensitivity of In

2O3-

based ozone sensors at RT (119878 sim 350 at 12 ppm O3) A

high sensitivity to ozone was observed in both dry andhumid atmospheres Typical characteristics of these sensorsare shown in Figure 19We cannot explain this result becausethere are some papers that report an opposite effect For


After UV irradiation in vacuum

1

2

After exposure to ozone

0 50 100 150 200 250 300 350

Substrate temperature (∘C)

10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Con

duct

ivity

(Ωminus1

cmminus1)

Figure 17 Maximum and minimum conductivities of InO119909films

prepared at different substrate temperatures during photoreduc-tionreoxidation process Films were deposited by DC-magnetronsputtering Photoreduction was carried out in vacuum using UVHg lamp Adapted with permission from [173] Copyright 2001American Institute of Physics

0 50 100 150 200

Operation temperature (∘C)

103

104

105

106

107

Sens

or re

spon

seR

ozon

eR

air

Figure 18 Sensitivity of a 100 nm thick InO119909film versus operation

temperature Films were deposited by DC-magnetron sputteringPhotoreduction was carried out in vacuum using UV Hg lampAdapted with permission from [170] Copyright 2001 Wiley-VCH

example Wang et al [121] have shown that the sensitivity toozone of UV-assisted In

2O3sensors strongly decreased in a

humid atmosphere at RT They observed that the increase ofair humidity from 0 to 12 RH was accompanied by a dropof sensor response from 119878 sim 100 to 119878 sim 13 In additionMunuera et al [132] have shown in the example of TiO

2

that UV photodesorption from fully hydroxylated surfaceis a complicated process because the ldquophotodesorption ofwaterrdquo which can be activated by reaction (20) with forming

24ppm ozone LED on

24ppm ozoneLED off

15 30 45 600

Time (min)

Resp

onse

[RR

0]

In2O3

24ppm ozoneLED off

50 100 1500

150

0

02

04

06

(k)

0

04 k

08 k

12 k

16 k

Figure 19 Response of In2O3sensor at room temperature to

24 ppm ozone in dry atmosphere with and without illumination bya blue LED (120582 = 460 nm) (119889 sim 5 120583m) Data extracted from [119]

OH∙ radicals can be accompanied by the photoadsorptionof oxygen on these ldquofully hydrated surfacesrdquo Consider thefollowing

OHminus + h-e 997904rArr OH∙ + eminus (free) (20)

Only the thermal removal of water and hydroxyl groupsreduced the photoadsorption of oxygen Munuera et al[132] assumed that the reduction from Ti4+ to Ti3+ underirradiation produced a weakening of the bond to the pointof desorbing H

2O from the surface During the diffusion

of ldquoexcitonsrdquo from the ldquoporthole sitesrdquo to the trapping sitesdesorption of water molecules may occur with each excitonbeing responsible for desorption of a certain number of watermolecules before oxygen adsorption takes place This meansthat the UV photoreduction of the metal oxide surface inhumid air is not as effective as in dry air

Thus it is possible that the high RT sensitivity of thesensors designed by Wagner et al [119] in humid air wasachieved due to the specific technology used for the In

2O3

synthesis and therefore specific surface properties of gas-sensitive material mesoporous In

2O3used as gas-sensitive

material was synthesized by a nanocasting procedure Inaddition the authors did not use the high temperaturetreatment (119879 gt 500∘C) to stabilize the properties of thefilms Moreover before each measurement the samples weresubjected to specific pretreatment The same situation wasobserved in [182] Chien et al [182] have found that a sharpincrease in the sensitivity of RT ZnO-based sensors to ozonetook place only in that case if the photoreduction was carriedout at temperatures above 500∘C

As for the results presented in [176] (see Table 5)there is also some uncertainty about the conditions of theexperiment because the same authors in later articles [121163 177] for the same films provided data on sensitivity toozone which at 4 orders of magnitude were lower than datareported in [176] Apparently these differences are relatedto differences in the measurement methodologies used inthese articles In [176] theUVphotoreductionwas conducted


under synthetic air without ozone but the measurement ofsensor response to ozone was performed at off UV lightIn this case we have a situation close to that which wasobserved during UV photoreduction in vacuum when itwas not possible to separate the contributions of ozone andoxygen presented in the atmosphere in the change of filmconductivity while in [121 163 177] UV light was switchedon during the whole measurement cycle

Unfortunately we have a very limited amount of researchin the field of UV assistance RT ozone sensors and verylimited information about In

2O3and especially SnO

2films

used for the fabrication of these sensorsTherefore we do nothave the opportunity to conduct a detailed consideration ofthese devices We can only say that the main requirements ofmetal oxides aimed toward application in RT ozone sensors[15 171 173] coincide with the requirements that have beenestablished for conventional sensors The response to ozoneincreased with decreasing grain size [163 176] and filmthickness [174] For example Wang et al [176] reported thatan increase in grain size from 7 to 10 nmwas accompanied bythe decrease in the sensor response from 105 to 10

6 Water Influence on OperatingCharacteristics of Heated Ozone Sensors

It is necessary to say that water seems to play an importantrole in the reactions of ozone detection As is known metaloxide surfaces can be characterized by their ability to formstrong chemical and hydrogen bonds with water molecules[24] Korotcenkov et al [53 54 56] have shown that waterinfluenced the magnitude of sensor response to ozoneresponse and recovery times and the activation energies ofprocesses that control the kinetics of gas-sensing effects Thismeans that the presence of humidity in the surroundingatmosphere adds complexity to the sensing process and pos-sible surface reactions should be more complicated becausewater can interact with both lattice atoms of metal oxidesand adsorbed species including oxygen and ozone [53 56116 166] For example Caldararu et al [189] concluded thatthe presence of hydroxyl groups at the surface of this oxidelimited the oxygen adsorption at temperatures of 320ndash340∘Ceven under exposure to pure oxygen In addition processessuch as water dissociation the protonation of surface groupsand ion surface complexation should be taken into accountA schematic illustration of the behavior of water at the surfaceof SnO

2is shown in Figure 20

However admittedly the role of water is not completelyunderstood yet For example we are not able to suggest anexperimentally confirmed mechanism which could explainthe growth of response in humid air observed for both In

2O3-

[33] and SnO2-based ozone sensors [56] operated in the

temperature range of 200ndash400∘C It is important to note thatfor RT In

2O3ozone sensors operated under the influence of

UV illumination the response to ozone decreases with airhumidity increases [121] For comparison the response ofthe In

2O3and SnO

2sensors to reducing gases also decreases

in humid air as a rule [33 190] We believe that onlythe mentioned effects are connected to the specific role ofwater both in the reactions of ozone detection and in the

mechanism of ozone dissociation at the hydroxylated surfaceof SnO

2 For example hydroxyl groups are known to catalyze

ozone decomposition [55] It is also known that the reactionof hydroxylation has a clear donor-like character [191ndash193]and causes an increase in conductivity and a decrease ofband-bending According to general conceptions [191ndash193]the water molecules interact dissociatively with defect-freetin oxide by forming a terminal OH-group situated at theSn5c Lewis acid site while the proton forms the bridging

OH-group with the twofold coordinated O atoms on thenext ridge One of the possible reactions that can explainthe above-mentioned behavior of conductivity is presentedbelow

(SnSn120575+-OH120575minus) +O

3+ (OO-H

+) + 2eminus

997904rArr (SnSn-Ominus) +OO +O

2uarr +H

2O uarr

(21)

Here water desorption results from the ozone-OH interac-tion We assume that ozone can form intermediates suchas HO

2or HO

3[194ndash196] during the interaction with the

hydrated surface In this reaction we did not take intoaccount molecular oxygen and water because as shown inFigure 20 at119879 gt 200∘COH-groups and chemisorbed oxygenwere dominant at the surface of the metal oxides [56 116 197198] Molecular water desorbs from the surface of SnO

2at

119879 sim 100∘C while molecular oxygen desorbs at 119879 gt 180ndash

200∘C As shown in the right part of (21) the state of the SnO2

surface after interaction with ozone is the same as the stateof the surface after reaction with ozone in a dry atmospherein this case This means that hydroxyl groups participate inthe reaction of ozone detection therefore dissociative wateradsorptiondesorption can control the kinetics of sensorresponse to ozone in humid air (read the next section)

When the operation temperature exceeds 350∘C theinfluence of water vapors on the operating characteristics ofozone sensors is being considerably decreased As shown inFigure 21 at 119879oper gt 350∘C the influence of RH becomesinsignificant In principle this effect is expected because itwas observed many times for the SnO

2and In

2O3sensors

during reducing gas detection Moreover this observation isconsistent with the results of the temperature-programmeddesorption (TPD) and Fourier transform infrared (FTIR)spectroscopic studies of OH-desorption from the SnO

2sur-

face [197 199] These reports show that hydroxyl groups startto desorb at 119879 gt 200ndash250∘C and are virtually absent at 119879 gt

400∘CThus if there are no limitations in consumable powerand we do not have strict requirements of selectivity (in thehigh temperature range sensors are sensitive to reducinggases) 119879oper sim 350ndash400∘C would be optimal for ozonesensor operation in an environment with variable humidityCertainly sensitivity in this temperature range decreases butthis reduction is not critical for ozone detection

7 Processes That Control the Kinetics ofResponse of Metal Oxide Ozone Sensors

71 Heated Ozone Sensors Theprevious sections describe themechanism of ozone interaction with the metal oxide surface


H2O (cond) H2O (phys)

Bonded viahydrogen bridge

Physisorbed Chemisorbed hydroxyl groups

Different OH-groups

100 200 300 400 5000Temperature (∘C)

Figure 20 Literature survey of water-related species formed at different temperatures on SnO2surfaces Data extracted from [24]

Sens

or re

spon

se

100 200 300 400 500

Sens

or re

spon

se

300 400 500 600

Sens

itivi

ty to

air h

umid

ityTh

e rat

io S

(wet

)S(

dry)

SnO2

100

101

102

100

101

102

103

100

101

102

103

104

Pyrolysis temperature (∘C)

100 200 300 400 500∘C)Operating temperature (


RH sim 45

RH sim 1-2

RH sim 45

RH sim 1-2

Figure 21 Influence of deposition temperature on the sensitivity toair humidity of SnO

2sensor response to ozone (sim1 ppm) Sensitivity

to air humiditywas calculated as a ratio of responsesmeasured in dry(1-2 RH) and wet (sim45 RH) atmospheres at 119879oper correspondingto maximum response in humid atmosphere (119889 sim 30ndash50 nm)Adapted with permission from [56] Copyright 2007 Elsevier

but do not answer the question of how this interaction affectsthe properties of themetal oxide gas-sensingmatrix andwhatprocesses control the kinetics of these changes It is clearthat the change in conductivity of metal oxides (Δ119866 sim Δ119899

119887

where 119899119887is the concentration of free charge carriers in the

metal oxide) induced by their interaction with ozone can becontrolled by surface and bulk processes [54]

As shown in [57] In2O3and SnO

2films deposited

using thin film technologies are compact and in spite of aconsiderably smaller thickness they do not have the porosityfound in sensors fabricated by thick or ceramic technologies[86] Experiments have shown that films deposited usingsputtering technologies had an especially dense structure[86 200] This means that these films are less gas-permeablein comparison with films prepared using thick film tech-nologies Typical cross sections of such films are shown inFigure 22 These SEM images show a clear interface betweencrystallites This fact points to the absence of necks betweengrains whose overlap is usually used to explain the high

Thick film technology Thin film technology

Grain

Grain

SubstrateIntergrain pores

Knudsengas diffusion

Surfaceintercrystallite

diffusion

(a) (b)

Figure 22 Diagram illustrating difference in structures of the filmsprepared using ldquothickrdquo and ldquothinrdquo film technologies Reprinted withpermission from [57] Copyright 2009 Elsevier

sensitivity of ceramics-based gas sensors This means thatfilms deposited by thin film technology have larger contactareas between crystallites In addition due to the columnarstructure in which grains can grow through the full filmthickness (see Figure 23) the area of the indicated contactsis considerably increased with the film growth For the thickfilm sensors the grain size and the area of intergrain contactsdo not depend on the film thickness Taking into accountsuch a situation Korotcenkov et al [54] concluded thatintercrystallite (surface) diffusion should be involved in theexplanation of the gas-sensing characteristics of thin filmgas sensors in addition to commonly used surface and bulkprocesses

According to Korotcenkov et al [54] four processescontrol the magnitude and kinetics of response to ozone (seeFigure 24) They are as follows (1) adsorptiondesorptionprocesses and catalytic reactions at the metal oxide surface(Δ119899119887sim Δ119873

119878sim 119881119878 where 119899

119887is the concentration of free charge

electrons in the bulk of grains 119873119878is the total concentration

of chemisorbed chemical species and 119881119878is the rate of

surface chemical reactions and Δ119866 sim Δ120601119878sim Δ119876

119878sim Δ119873

119878

where 120601119878is the height of the intergrain potential barrier

and 119876119878is the charge on the interface surface states) (2)

chemical reactions with lattice (O119871) oxygen participation

(reductionreoxidation) (Δ119899119887sim 998779(MeO)

119887sim Δ(MeO)

119904


Intergrain interface

Figure 23 SEM images of the SnO2films deposited at 119879pyr = 520∘C (119889 sim 120 nm) Reprinted with permission from [57] Copyright 2009

Elsevier

Intergrain (surface) diffusion

Reductionreoxidation

Bulk oxygendiffusion

Surface unstoichiometric

layerBulk region

Interface region

Grains

Change of the thickness of unstoichiometric surface layerchange of bulk conductivitychange of the thickness ofspace-charge region

at the intergrain interfacechange of the height of intergrain potential barrierchange of intergrain resistance

Adsorptiondesorption

Change of surface chargechange of surface potential change of the concentration ofchemisorbed oxygen participatedin ldquoredoxrdquo and diffusion

Change of surface stoichiometry

change of surface potential change of surface conductivity

change of the concentration ofchemisorbed oxygen

change of surface reactivity

Change of MeOx stoichiometry

Figure 24 Diagram illustrating surface and bulk processes taking place inmetal oxidematrix during ozone detection and their consequencesfor polycrystalline material properties Reprinted with permission from [54] Copyright 2007 Elsevier

where (MeO)119887and (MeO)

119904are the bulk and surface

stoichiometry of metal oxides correspondingly) (3) surfaceand intercrystallite oxygen diffusion influencing the 120601

119878

and (MeO)119904 (4) the bulk diffusion of oxygen (diffusion of

oxygen vacancies) which influences the concentrations ofionized centers and the mobility of charge carriers throughthe change of the concentration of point defects (119873

119901) in

metal oxides ((Δ119899119887 Δ120583119887) sim 998779119873

119901sim 998779(MeO)

119887)

If all the four processes listed above participate in thegas-sensing to a greater or lesser extent then the transientcharacteristics of sensor response should be represented asthe superposition of the four components related to theseprocesses [54] that is

Δ119866 (119905)

= 119870119889(119905) Δ119866

1(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905)

(22)

where 1198661(119905) is the change of conductivity connected to the

adsorptiondesorption processes on the surface of the metaloxide 119866

2(119905) is the change of conductivity conditioned by

the processes of reductionreoxidation 1198663(119905) is the change

of conductivity controlled by the intercrystallite (grain)diffusion of oxygen and 119866

4(119905) is the change of conductivity

connected to bulk oxygen diffusion Taking into account thegeneral character of the discussion to obtain a full picturewe have introduced in (22) an additional component 119870

119889(119905)

which characterizes the rate of delivery of both analyte gasand oxygen to the place where indicated reactions occurThelast process as is well known is controlled by the diffusionof analyte gas and oxygen from the surface region of the gas-sensing material into its internal region

From (22) one can see that two extreme scenarioscould occur in ozone sensors depending on the correlationbetween the rate of gas diffusion and the rates of processestaking place on the surface and in the bulk of the metal oxidegrains In the first case the kinetics of sensor response iscontrolled by the gas diffusion inside the metal oxide matrix

Δ119866 (119905) = 119870119889(119905) Δ119866 (23)

Such an approach for analyzing the gas-sensing proper-ties of solid-state sensors was developed in [142 201ndash210]


It is referred to as a diffusion-reaction model According tothis model the gas molecules diffuse inside the sensing layerwhile they are consumed at a certain rate during diffusion bythe surface reaction This means that the gas-sensing processis considered a phenomenon in which the diffusion andreaction are coupled Because of this coupling the responsebehavior is strongly influenced by the catalytic and micro-porous properties (gas penetrability) of the sensor materialused As a rule the diffusion-reaction model describes goodkinetics of response of sensors fabricated by ceramics or thickfilm technology and uses a gas-sensing layer with thickness inthe micrometer range

In the second case the kinetics of sensor response hasbeen controlled by the processes taking place either on thesurface or in the bulk of the grains [54]

Δ119866 (119905) = Δ1198661(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905) (24)

The last statementmeans that the process of gas diffusion intothemetal oxidematrix is fast and does not limit the rate of thefilm conductivity change during the replacement of the gassurroundings Such an approach to the analysis of gas-sensingeffects was considered in [116 117 211ndash213] As a rule such anapproach has been used for the description of the gas-sensingcharacteristics of thin film sensors

It is significant that during the measurement of thesensor response rate through the estimation of response andrecovery times at the level of 05 and even 09 from the steady-state value of film conductivity the time constants of responseand recovery could not be controlled by the slowest processunder certain conditions They could be controlled by themost influential process (ie the one providing the maximalcontribution to the conductivity change of the gas-sensingmaterial)

No doubt the suggested approach to the considerationof gas response kinetics is simplified enough While makingsuch a consideration we did not take into account that theanalyzed processes are multistage ones [24 214ndash216] andas a rule comprise electron exchange between adsorbedspecies and the bulk of the metal oxide It is known thatthe adsorption of chemical species without electron exchange(physisorption) cannot be responsible for the change inconductivity of the metal oxide [24 83] This means thatunder certain conditions the time of sensor response andrecovery during the process of gas detection could be limitedby the rate of electron exchange However research on SnO

2-

and In2O3-based CO and H

2sensors conducted in [53 116

211] has shown that at 119879oper gt 100∘C the electron transferof delocalized conduction band electrons to localized surfacestates took place quite quickly and this process was not afactor that limited the rate of sensor response

The experiment and simulation have shown that surfacechemical reactions (reductionreoxidation) may also takeplace via a precursor state the occupancy of which is con-trolled by adsorptiondesorption (119886119889) processes [117 214ndash216] In this case the change of conductivity Δ119866

3(119905) could be

presented as follows [116]

Δ1198663(119905) = 119870

119886119889(119905) Δ119866

119888(119905) (25)

1-2 RH

Resp

onse

tim

e (se

c)

100

101

102

103

In2O3

20 40 60 10010Grain size (nm)

120591 sim t2

Figure 25 Dependencies of response time during ozone detection(119879oper sim 270

∘C) on the grain size of In2O3films deposited from

02M InCl3-water solution Reprinted with permission from [43]

Copyright 2004 Elsevier

This means that the adsorptiondesorption (119886119889) processescould exactly determine the kinetics of those reactions asthe slowest in this sequence of events Such a conclusion wasmade in [116 117 211 212] while analyzing the gas sensitivityof SnO

2-based solid-state sensors to reducing gases It was

established that the kinetics of sensor responses to CO andH2was controlled by the processes of oxygen and water

adsorptiondesorptionIt is significant that if the shape of transient curves

119866(119905) depends on the mechanism of the surface and bulkprocessesrsquo influence on the metal oxide conductivity [24212] the absolute value of the time constants used for thedescription of observed changes in metal oxide conductivityand activation energies determined from the temperaturedependences of response and recovery times are specificparameters for those surface and bulk processes As is known[28 117 146 201 202 212] processes that control the kineticsof sensor response are activation ones which have someactivation energy specific for each process

A detailed study of the kinetics of solid-state sensorresponse to ozone was conducted by Korotcenkovrsquos groupfor In

2O3-based devices The results of this research were

reported in [54 56 116] It was found that in a dryatmosphere (1-2 RH) the response time showed a cleardependence on film thickness (Figure 5) and grain size (seeFigure 25) which can be described by the equation 120591res sim

(119889 119905)119898 with index 119898 close to 2 [43] As is known such

dependence is specific for the diffusion processTaking into account the features of the structural prop-

erties of thin films [43 45 47 98ndash102 109 114] Korot-cenkov et al [54] have assumed that the above-mentioneddiffusion process is intergrain (surface) oxygen diffusion


0 100 200 300 400Thickness (nm)

Activ

atio

n en

ergy

(eV

)

20

16

12

08

04

0

OzoneResponse

Recovery

Dry

Dry

Wet

Wet

1

2

3

E sim 15 eV

E sim 06 eV

Figure 26 Influence of the film thickness on the activation energiesof transient characteristics during ozone detection (1) response(2 and 3) recovery (1 and 2) dry atmospheres (RH sim 1ndash3) (3)wet atmosphere (RH sim 45ndash60) 119879pyr = 475∘C Reprinted withpermission from [54] Copyright 2007 Elsevier

Korotcenkov et al [54] believe that the driving force of thisdiffusion process (gradient in oxygen chemical potential)may occur due to the change in oxygen concentration (OIn)

119878

in the surface nonstoichiometric layer This conclusion wasbased on the following facts (1) the In

2O3and SnO

2surfaces

are nonstoichiometric with compositions sensitive to chem-ical environment changes (2) only oxygen participates in thereaction of O

3detection in a dry atmosphere and (3) 120591 =

119891(119864119896119879) dependencies determined for In2O3-based sensors

with thicknesses exceeding 100 nm during the response toozone in a dry atmosphere at operating temperatures higherthan 200ndash250∘C have activation energy equal to 12ndash18 eV(see Figures 26 and 27(a)) [54] Analysis of the literaturedata confirms that such activation energies correspond to theactivation energy of oxygen diffusion in polycrystallinemetaloxides which is controlled by surface or intergrain diffusionand does not exceed 15ndash18 eV [217] For comparison forbulk oxygen diffusion in metal oxides including In

2O3 one

can find activation energies in the range from 26 to 50 eV[200 218] As is known surface diffusion ismuch faster (sim105)than bulk oxygen diffusion

At the same time the recovery time depends weakly onthe film thickness (see Figure 25) and the grain size evenat relatively low air humidity (1-2 RH) In addition in awet atmosphere the influence of In

2O3grain size on the

time constants of gas response to ozone dropped sharplyand the activation energies of 120591 = 119891(119864119896119879) dependencieswere changed (Figure 27(a)) Such behavior of the timeconstants indicates that the kinetics of sensor response in awet atmosphere and the kinetics of recovery processes arecontrolled by several processes most of which are relatedto the surface reactions Analysis of the transient curves

of conductivity response to ozone carried out in [53 54]has shown that the kinetics of recovery processes had twocharacteristic activation energies (119864act) for 120591 = 119891(119864119896119879)

dependencies [54] (1) 025ndash03 eV and (2) 05ndash06 eV The119864act sim 05ndash06 eV is peculiar to transient processes of theconductivity response of ldquoporousrdquo films As a rule theseprocesses were dominant at 119879oper gt 100∘C when a dryatmosphere was used Processes with the activation energy025ndash03 eV were generally observed during ozone detectionin a wet atmosphere Taking into account that processeswith 119864act sim 03 eV were dominant in ozone detection ina wet atmosphere and processes with the activation energyof sim06 eV were dominant in a dry atmosphere it wasassumed that the first one is related to water participationand the second is associated with oxygen participation inthese reactions [54] This is a real assumption since onlyoxygen and water participate in reactions of ozone detectionand only dissociative oxygen adsorptiondesorption in adry atmosphere should control the kinetics of equilibriumachievement between the stoichiometry of the surface layerand the surrounding atmosphere during the recovery processof ozone detection Regarding the processes with activa-tion energies between 025ndash03 and 06 eV which are oftenobserved in experiments one can say that their appearanceis quite ordinary In a real reaction of ozone detectionboth H

2O and oxygen participate simultaneously therefore

in many cases the reaction of ozone detection can runthrough two different but interrelated paths Temperatureprogrammed desorption (TPD) measurements [219] haveshown that both chemisorbed oxygen and water were ratherstrongly bound to the In

2O3surface According toYamaura et

al [219] after exposure to O2 significant oxygen desorption

from the In2O3surface begins only at 119879 gt 500∘C In similar

experiments H2O began desorbing from the In

2O3surface

at 119879 sim 210ndash230∘C reaching the maximum at 119879 = 400∘CHowever even at 119879 sim 600

∘C a sufficient quantity of H2O

perhaps in the form ofOH-groups remains on the In2O3sur-

face Thus the surface species (O2and H

2O) in chemisorbed

forms (Ominus andOH) can exert an influence on the gas-sensingcharacteristics of In

2O3gas sensors over the whole analyzed

temperature rangeAs shown in Figures 26 and 27(b) in ultrathin films

(119889 lt 50 nm) with a small grain size processes with activationenergies of 025ndash03 eV are already dominant at RH sim 1ndash3 This observation is important and indicates that with agrain size decrease into the nanometer range (119905 lt 10 nm)the change of energetic parameters of adsorptiondesorptionprocesses at the In

2O3surface or the increase of the water

role in surface reactions occurs The change of grain shapeis confirmation of the first mechanism As established in[102] at a thickness of less than 40ndash60 nm the In

2O3

grains lose crystallographic faceting and obtain the shapeof spherulite The increase of water influence both on thegas sensitivity of In

2O3films with a small grain size [53]

and on NO119909conversion by an In

2O3-Al2O3catalyst with the

smallest In2O3particles [220] is confirmation of the second

mechanismIt should be noted that the diffusion nature of the kinetics

of sensor response in a dry atmosphere and the surface


1

2

34

5

6035 eV

055 eV

13

eV

100

101

102

103

Tim

e con

stant

s (se

c)

450 350 250Operating temperature (∘C)

16 qkT (eVminus1)

18 20 22

Esim115

eV

(a)

1

2

34

5

Response

Recovery (wet air)

Dry airWet air

Wet02

8 eV

In2O3

18 20 22 24 26 28 30

400 300 200 150

qkT (eVminus1)

100

101

102

103

Tim

e con

stant

s (se

c)

Operating temperature (∘C)

E sim 033 eV

(b)

Figure 27 (a) Influence the air humidity on temperature dependencies of (1ndash3) response and (4ndash6) recovery times during ozone detectionby In2O3-based sensors (119879pyr = 475∘C 119889 sim 200 nm 10M InCl

3-solution) 1 4 sim05 RH 2 5 sim25ndash30 RH (3 6) sim60 RH (b) temperature

dependencies of the time constants during ozone detection by In2O3ultrathin films in wet (35ndash40 RH) and dry (1-2 RH) atmospheres

(119879pyr = 475∘C) 1 2 005M InCl3-solution 119889 sim 20ndash40 nm 3 4 and 5 10M InCl

3-solution 119889 sim 40 nm Adapted with permission from [54]


nature of the reactions responsible for kinetics of both therecovery process and sensor response in a humid atmosphereare not contradictory Korotcenkov et al [54] believe thatdiffusion also participates in processes occurring in a humidatmosphere However in this case diffusion is controlledby surface reactions This means that the concentration ofoxygen capable of diffusing and affecting the conductivityof metal oxides via influence on the intercrystallite potentialbarrier is controlled by the rate of surface reactions [221]particularly in a humid atmosphere by dissociative wateradsorptiondesorption processes These processes controlthe time of equilibrium establishment between the surfacestoichiometry of In

2O3and the surrounding gas The above-

mentioned statement that the surface stoichiometry of In2O3

can control the surface diffusion processes is very importantSuch a conception gives us an understanding of the natureof other effects observed during the In

2O3sensor response

kinetics study For example this conception explains theabsence of transient processes controlled by the bulk oxygendiffusion in In

2O3even for the transient sensor response

measured at 119879oper gt 350∘C when diffusion processes shouldoccur No doubt further research is required for understand-ing in detail the role of diffusion and water in reactionsof ozone detection The question regarding oxygen vacancyparticipation in the reactions of ozone detection also requiresan answer Namely is there a change in the concentration ofsurface oxygen vacancies during ozone chemisorption

One should note that the approach used for explaining thekinetics of the In

2O3ozone sensor response can be applied to

SnO2ozone sensors as well In particular Korotcenkov and

Cho [57] have shown that diffusion in the gas phase includingKnudsen diffusion [222] (the approach used for ldquothick filmrdquoand ceramic gas sensors [81 206 223]) could not limit

the kinetics of response of SnO2thin film gas sensors For

films with a thickness of 40ndash70 nm it is difficult to imaginethe existence of a structure in which the sensitivity is limitedby gas diffusion along the pores Korotcenkov et al [56]believe that similarly to In

2O3 the kinetics of SnO

2based

gas sensors is controlled by intergrain (surface) diffusion andsurface reactions such as the adsorptiondesorption of waterand oxygen in various forms

Analyzing the kinetics of SnO2thin film ozone sensor

response Korotcenkov et al [56] have established that forSnO2response and recovery processes there were several

characteristic activation energies as well It was found thattransient processes with activation energies of sim06ndash075 eVwere typical in a wet atmosphere in the region of maximumsensitivity (119879oper sim 200ndash300∘C) (see Figure 28) The tem-perature dependence of the time constants for the recoveryprocess generally showed activation energies in the rangeof 075ndash11 eV In a dry atmosphere the activation energiesfor dependence 120591 = 119891(1119896119879) increased and attained 095ndash11 eV and 11ndash16 eV for the response and recovery processesrespectively For some samples in 120591 = 119891(1119896119879) dependencesthere were regions with activation energies of sim026ndash04 eVAs shown in Figure 28 processes with activation energies of025ndash04 eV were observed at temperatures of 119879oper lt 200∘Ccorresponding to the region of low sensitivity while processeswith activation energies of gt10 eV generally appeared inthe region of 119878(119879oper) dependency (119879oper gt 300∘C) whichcorresponds to a drop in sensor response to ozone It isnecessary to note that the change of activation energies of 120591 =119891(1119896119879) dependencies in the wide range from 025 to 16 eVdemonstrates that even for reactions of ozone detection oneshould take into account the presence of various processesand reaction steps in a complexmechanismof response [224]


0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV

Operating temperature (∘C)500

Figure 28 Diagram illustrating interrelation between temperaturedependence of SnO

2response to ozone and activation energies

determined from the temperature dependence of time constantsfor the transient response observations Reprinted with permissionfrom [56] Copyright 2007 Elsevier

It is interesting that the activation energies reportedherein are similar to those obtained during the analysisof the kinetics of SnO

2sensor response to reducing gases

[116 211 212] According to [123] the processes with acti-vation energies of 025ndash04 eV are the consequence of theadsorptiondesorption of molecular oxygen while the pro-cesses with activation energies of sim06ndash07 eV are connectedto the adsorptiondesorption of water and processes withactivation energies of sim10ndash15 eV are related to the adsorp-tiondesorption of chemisorbed oxygen [141 199]

72 RT Ozone Sensors Activated by UV Illumination Regard-ing the kinetics of the response of sensors operating at roomtemperature the available information is not enough for anyreliable conclusionsThe differences in film thicknesses con-ditions of experiments and the wavelengths and intensitiesof the illumination used to activate the low temperaturesensitivity to ozone do not allow comparing the resultsobtained by different teams and making any generalizationsIn addition the presence of water greatly complicates themechanism of ozone interaction with the surface of metaloxides We can only refer to the results presented in [176]which showed that the effect of film thickness on thetime constants of transient processes is very similar to theregularities previously established for heated sensors workingin dry air [43 44] As for the heated sensor the response timeincreases with increasing film thickness and the recoverytime does not depend on the thickness (see Figure 29) Theseresults suggest that similar to heated sensors the responseof RT sensors activated by UV radiation is controlled bydiffusion processes whereas some kind of surface reactionscontrolled by the rate of charge carrier generation by UVlight is responsible for the rate of recovery processes Inmostcases when the UV illumination has a sufficient power and

Recovery time

Response time

100 100010Thickness (nm)

0

100

200

300

Tim

e con

stant

(sec

)

Figure 29 Response and recovery times of RT sensor response toozone in dependence on the layer thickness Nanoparticle In

2O3

layerwas grown at a substrate temperature of 200∘C Photoreductionwas carried out using UV LED (375 nm) Adapted with permissionfrom [176] Copyright 2007 American Institute of Physics

100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2

Power density (mWcm2)

Figure 30 Dependences of the ldquolight onrdquo conductivity response ofSnO2nanowires on incident power density and wavelength at room

temperature Data extracted from [186]

film is thin the recovery is fast and the recovery time does notexceed several tens of seconds [169 177] If the rate of chargecarrier generation is low the time for ozone desorption byUV irradiation can reach tens of minutes or more [177]As a rule this situation occurs when the film is thick orillumination with nonoptimal wavelength (120582 gt 400 nm) isused for activation In this case to achieve a noticeable effectthe intensity of illumination should be much greater (seeFigure 30)


According toWang et al [176] in case of sensor responsethe surface effect becomes dominant only when the filmthickness decreases to 10 nm Wang et al [176] believe thatdiffusion process which was mentioned above is the dif-fusion of oxygen molecules into the layer From our pointof view the intergrain diffusion which was discussed in theprevious section is a more probable diffusion process Withregard to the reduction of response time with increasingozone concentration (see Figure 16) the process is quitenatural because the rate of oxidation is directly related to theconcentration of the oxidizing agent involved in the process

8 Conclusions

This paper presents a critical assessment of the recent lit-erature on ozone measurement with conductometric metaloxide gas sensors The pertinent literature analysis revealsthat SnO

2and In

2O3metal oxides are promising materials

for ozone detection in various applications It has been shownthat SnO

2- and In

2O3-based ozone sensors can achieve

excellent detection limits down to a few ppb of ozone and fastresponse times of approximately several seconds at optimaloperation temperatures Therefore we believe that thesemetal oxides especially In

2O3 which has a shorter recovery

time are good choices for fabricating low-cost low-powerhighly sensitive and fast ozone sensors aimed for the sensormarket

This work also demonstrated that ozone sensors basedon SnO

2and In

2O3are complex devices and understanding

their operation requires the consideration of all factors thatinfluence final sensor performance including surface chem-ical reactions various diffusion processes and the associatedcharge transfers In the present review we discussed theseprocesses However it should be recognized that the level ofunderstanding of these processes (ie the nature and originof the mechanism that takes place between SnO

2and In

2O3

surfaces and ozone) is still insufficient and further research inthis area is required

We hope that the present overview of the present state ofthe SnO

2and In

2O3response to ozone will be of interest to

gas sensor developers and persuade them to carry out muchmore systematic research in order to better understand SnO

2

and In2O3chemistry the adsorptiondesorption processes

taking place at the surface of SnO2and In

2O3films with dif-

ferent crystallographic structures and stoichiometry and themetal oxide-ozone interaction in atmospheres with differentair humidity Certainly some precise theoretical calculationsand computational modeling of ozone interactions with theSnO2and In

2O3surfaces and the subsequent changes in

the electronic band structure of gas-adsorbed metal oxidenanostructures are required as well We believe that deeperknowledge of physical and chemical phenomena that takeplace at the surface of SnO

2and In

2O3can improve the

sensing capabilities of these sensing materials for real appli-cations

Competing Interests

The authors declare that they have no competing interests

Acknowledgments

This work was supported by the Ministry of Science ICTand Future Planning of Korea via KOFST and NRF Programsand Grants (nos 2011-0028736 and 2013-K000315) and partlyby the Moldova Government under Grant 158170229F andASM-STCU Project no 5937

References

[1] R G Rice and A Netzer Handbook of Ozone Technology andApplications Ann Arbor Science Ann Arbor Mich USA 1984

[2] P Siesverda ldquoA review of ozone applications in public aquariardquoin Proceedings of the 9th Ozone World Congress pp 246ndash295New York NY USA 1989

[3] V Camel and A Bermond ldquoThe use of ozone and associ-ated oxidation processes in drinking water treatmentrdquo WaterResearch vol 32 no 11 pp 3208ndash3222 1998

[4] M Horvath L Bilitzky and J Huttner Ozone Elsevier Ams-terdam The Netherlands 1985

[5] G A Cook ldquoIndustrial uses of ozonerdquo Journal of ChemicalEducation vol 59 no 5 pp 392ndash394 1982

[6] Applications and uses for ozone httpo3ozonecomqampa info-rmedozone applicationshtm

[7] Ozone applications Ozone solutions Inc httpwwwozone-solutionscom

[8] V BocciOzone A NewMedical Drug Springer DordrechtTheNetherlands 2005

[9] C Gottschak J A Libra and A SaupeOzonation of Water andWaste Water A Practical Guide to Understanding Ozone andits Applications John Wiley amp Sons Weinheim Germany 2ndedition 2010

[10] C OrsquoDonnell B K Tiwari P J Cullen and R G Rice EdsOzone in Food Processing John Wiley amp Sons Chichester UK2012

[11] M D Rowe K M Novak and P D Moskowitz ldquoHealth effectsof oxidantsrdquo Environment International vol 9 no 6 pp 515ndash528 1983

[12] N Alexis C Barnes I L Bernstein et al ldquoHealth effects of airpollutionrdquo Journal of Allergy and Clinical Immunology vol 114no 5 pp 1116ndash1123 2004

[13] WHO Air Quality GuidelinesmdashGlobal Update 2005 WHORegional Publications European Series World Health Orga-nization Regional Office for Europe Copenhagen Denmark2006

[14] D Sauter U Weimar G Noetzel J Mitrovics and W GopelldquoDevelopment of modular ozone sensor system for applicationin practical userdquo Sensors and Actuators B Chemical vol 69 no1 9 pages 2000

[15] C Wang Metal organic chemical vapor deposition of indiumoxide for ozone sensing [PhD thesis] Albert-Ludwigs-Uni-versitat Freiburg Freiburg Germany 2009

[16] G Korotcenkov and B K Cho ldquoOzone measuring what canlimit application of SnO

2-based conductometric gas sensorsrdquo

Sensors and Actuators B Chemical vol 161 no 1 pp 28ndash442012

[17] M David M H Ibrahim S M Idrus et al ldquoProgress in ozonesensors performance a reviewrdquo Jurnal Teknologi vol 73 no 6pp 23ndash29 2015


[18] G Korotcenkov and V Sysoev ldquoConductometric metal oxidegas sensorsrdquo in Chemical Sensors Comprehensive Sensor Tech-nologies G Korotcenkov Ed vol 4 of Solid State Devices pp39ndash186 Momentum Press New York NY USA 2011

[19] G Korotcenkov ldquoMetal oxides for solid-state gas sensors whatdetermines our choicerdquo Materials Science and Engineering Bvol 139 no 1 pp 1ndash23 2007

[20] G M Hansford R A Freshwater R A Bosch et al ldquoA lowcost instrument based on a solid state sensor for balloon-borneatmospheric O

3profile soundingrdquo Journal of Environmental

Monitoring vol 7 no 2 pp 158ndash162 2005[21] F Rock N Barsan and U Weimar ldquoElectronic nose current

status and future trendsrdquo Chemical Reviews vol 108 no 2 pp705ndash725 2008

[22] G Korotcenkov and J R Stetter ldquoChemical gas mixtureanalysis and the electronic nose current status future trendsrdquoin Chemical Sensors Comprehensive Sensor Technologies GKorotcenkov Ed vol 6 of Chemical Sensors Applications pp1ndash56 Momentum Press New York NY USA 2011

[23] M Bart D E Williams B Ainslie et al ldquoHigh density ozonemonitoring using gas sensitive semi-conductor sensors in thelower Fraser valley British Columbiardquo Environmental Scienceand Technology vol 48 no 7 pp 3970ndash3977 2014

[24] N Barsan and U Weimar ldquoConduction model of metal oxidegas sensorsrdquo Journal of Electroceramics vol 7 no 3 pp 143ndash1672001

[25] D E Williams ldquoConduction and gas response of semiconduc-tor gas sensorsrdquo in Solid State Gas Sensors P T Moseley and BC Tofield Eds pp 71ndash123 Taylor and Francis Bristol Pa USA1987

[26] M J Madou and S R Morrison Chemical Sensing with SolidState Devices Academic Press New York NY USA 1989

[27] S R MorrisonThe Chemical Physics of Surfaces Plenum NewYork NY USA 2nd edition 1990

[28] V Brynzari G Korotchenkov and S Dmitriev ldquoTheoreticalstudy of semiconductor thin film gas sensitivity attempt toconsistent approachrdquo Journal of Electronic Technology vol 33pp 225ndash235 2000

[29] N Barsan and U Weimar ldquoUnderstanding the fundamentalprinciples of metal oxide based gas sensors the example of COsensing with SnO

2sensors in the presence of humidityrdquo Journal

of Physics Condensed Matter vol 15 no 20 pp R813ndashR8392003

[30] I-D Kim A Rothschild and H L Tuller ldquoAdvances and newdirections in gas-sensing devicesrdquo Acta Materialia vol 61 no3 pp 974ndash1000 2013

[31] V Krivetskiy M Rumyantseva and A Gaskov ldquoDesign syn-thesis and application of metal oxide based sensing elementsa chemical principles approachrdquo inMetal Oxide Nanomaterialsfor Chemical Sensors M A Carpenter S Mathur and AKolmakov Eds pp 69ndash118 Springer Science Business MediaNew York NY USA 2013

[32] G Korotcenkov Handbook of Gas Sensor Materials vol 1-2Springer New York NY USA 2013

[33] T Sahm A Gurlo N Barsan and U Weimar ldquoProperties ofindium oxide semiconducting sensors deposited by differenttechniquesrdquo Particulate Science and Technology vol 24 no 4pp 441ndash452 2006

[34] T V Belysheva G N Gerasimov V F Gromov L I Trachten-ber and T V Belysheva ldquoThe sensor properties of Fe

2O3-In2O3

films ozone detection in air in the range of low concentrationrdquo

Russian Journal of Physical Chemistry A Focus on Chemistryvol 82 no 10 pp 1721ndash1725 2008

[35] T K H Starke and G S V Coles ldquoHigh sensitivity ozonesensors for environmental monitoring produced using laserablated nanocrystallinemetal oxidesrdquo IEEE Sensors Journal vol2 no 1 pp 14ndash19 2002

[36] M Ivanovskaya ldquoCeramic and film metaloxide sensorsobtained by sol-gel method structural features and gas-sensitive propertiesrdquo Electron Technology vol 33 no 1 pp108ndash113 2000

[37] G Korotcenkov ldquoGas response control through structural andchemical modification of metal oxide films state of the art andapproachesrdquo Sensors and Actuators B Chemical vol 107 no 1pp 209ndash232 2005

[38] N Katsarakis M Bender V Cimalla and E GagaoudakisldquoOzone sensing properties of DC-sputtered c-axis orientedZnO films at room temperaturerdquo Sensors and Actuators BChemical vol 96 no 1-2 pp 76ndash81 2003

[39] S R Utembe GMHansfordMG Sanderson et al ldquoAn ozonemonitoring instrument based on the tungsten trioxide (WO

3)

semiconductorrdquo Sensors and Actuators B Chemical vol 114 no1 pp 507ndash512 2006

[40] A Labidi E Gillet R Delamare M Maaref and K AguirldquoEthanol and ozone sensing characteristics of WO

3based

sensors activated by Au and Pdrdquo Sensors and Actuators BChemical vol 120 no 1 pp 338ndash345 2006

[41] L A Obvintseva ldquoMetal oxide semiconductor sensors fordetermination of reactive gas impurities in airrdquo Russian Journalof General Chemistry vol 78 no 12 pp 2545ndash2555 2008

[42] M Ivanovskaya A Gurlo and P Bogdanov ldquoMechanism of O3

andNO2detection and selectivity of In

2O3sensorsrdquo Sensors and

Actuators B Chemical vol 77 no 1-2 pp 264ndash267 2001[43] G Korotcenkov V Brinzari A Cerneavschi et al ldquoThe influ-

ence of film structure on In2O3gas responserdquoThin Solid Films

vol 460 no 1-2 pp 315ndash323 2004[44] G Korotcenkov A Cerneavschi V Brinzari et al ldquoIn

2O3films

deposited by spray pyrolysis as amaterial for ozone gas sensorsrdquoSensors and Actuators B Chemical vol 99 no 2-3 pp 297ndash3032004

[45] G Korotcenkov I Blinov M Ivanov and J R Stetter ldquoOzonesensors on the base of SnO

2films deposited by spray pyrolysisrdquo


[46] C Baratto M Ferroni G Faglia and G Sberveglieri ldquoIron-doped indium oxide by modified RGTO deposition for ozonesensingrdquo Sensors and Actuators B Chemical vol 118 no 1-2 pp221ndash225 2006

[47] G Korotcenkov V Macsanov V Tolstoy V Brinzari JSchwank and G Fagila ldquoStructural and gas response charac-terization of nano-size SnO

2films deposited by SILD methodrdquo


[48] OKorostynska K ArshakGHickey andE Forde ldquoOzone andgamma radiation sensing properties of In

2O3ZnOSnO

2thin

filmsrdquo Microsystem Technologies vol 14 no 4-5 pp 557ndash5662008

[49] J-B Sun J Xu B Wang P Sun F-M Liu and G-Y Lu ldquoUV-enhanced room temperature ozone sensor based on hierarchi-cal SnO

2-In2O3rdquo Chemical Research in Chinese Universities vol

28 no 3 pp 483ndash487 2012


[50] M Epifani E Comini J Arbiol et al ldquoChemical synthesis ofIn2O3nanocrystals and their application in highly performing

ozone-sensing devicesrdquo Sensors and Actuators B Chemical vol130 no 1 pp 483ndash487 2008

[51] M Epifani S Capone R Rella et al ldquoIn2O3thin films obtained

through a chemical complexation based sol-gel process andtheir application as gas sensor devicesrdquo Journal of Sol-GelScience and Technology vol 26 no 1ndash3 pp 741ndash744 2003

[52] A Oprea A Gurlo N Barsan and U Weimar ldquoTransport andgas sensing properties of In

2O3nanocrystalline thick films a

Hall effect based approachrdquo Sensors and Actuators B Chemicalvol 139 no 2 pp 322ndash328 2009

[53] G Korotcenkov M Ivanov I Blinov and J R Stetter ldquoKineticsof indium oxide-based thin film gas sensor response the roleof lsquoredoxrsquo and adsorptiondesorption processes in gas sensingeffectsrdquoThin Solid Films vol 515 no 7-8 pp 3987ndash3996 2007

[54] G Korotcenkov V Brinzari J R Stetter I Blinov and VBlaja ldquoThe nature of processes controlling the kinetics ofindium oxide-based thin film gas sensor responserdquo Sensors andActuators B Chemical vol 128 no 1 pp 51ndash63 2007

[55] T Takada K Suzuki and M Nakane ldquoHighly sensitive ozonesensorrdquo Sensors and Actuators B Chemical vol 13 no 1-3 pp404ndash407 1993

[56] G Korotcenkov I Blinov V Brinzari and J R Stetter ldquoEffect ofair humidity on gas response of SnO

2thin film ozone sensorsrdquo


[57] G Korotcenkov and B K Cho ldquoThin film SnO2-based gas

sensors film thickness influencerdquo Sensors and Actuators BChemical vol 142 no 1 pp 321ndash330 2009

[58] L Berry and J Brunet ldquoOxygen influence on the interactionmechanisms of ozone on SnO

2sensorsrdquo Sensors and Actuators

B Chemical vol 129 no 1 pp 450ndash458 2008[59] V Demarne and A Grisel ldquoA new SnO

2low temperature

deposition technique for integrated gas sensorsrdquo Sensors andActuators B Chemical vol 15 no 1ndash3 pp 63ndash67 1993

[60] Th Becker L Tomasi C B-V Braunmuhl et al ldquoOzone detec-tion using low-power-consumption metal-oxide gas sensorsrdquoSensors and Actuators A Physical vol 74 no 1ndash3 pp 229ndash2321999

[61] WHellmich C B-V Braunmuhl GMuller G Sberveglieri MBerti and C Perego ldquoThe kinetics of formation of gas-sensitiveRGTO-SnO

2filmsrdquoThin Solid Films vol 263 no 2 pp 231ndash237

1995[62] G Korotcenkov B K Cho L Gulina and V Tolstoy ldquoOzone

sensors based on SnO2films modified by SnO

2-Au nanocom-

posites synthesized by the SILDmethodrdquo Sensors andActuatorsB Chemical vol 138 no 2 pp 512ndash517 2009

[63] C Cantalini W Wlodarski Y Li et al ldquoInvestigation on theO3sensitivity properties ofWO

3thin films prepared by solndashgel

thermal evaporation and rf sputtering techniquesrdquo Sensors andActuators B Chemical vol 64 no 1ndash3 pp 182ndash188 2000

[64] O Berger T Hoffman W-J Fischer and V Melev ldquoTungsten-oxide thin films as novel materials with high sensitivity andselectivity to NO

2 O3 and H2S Part II application as gas

sensorsrdquo Journal of Materials Science Materials in Electronicsvol 15 no 7 pp 483ndash493 2004

[65] W Belkacem A Labidi J Guerin N Mliki and K AguirldquoCobalt nanograins effect on the ozone detection by WO

3

sensorsrdquo Sensors and Actuators B Chemical vol 132 no 1 pp196ndash201 2008

[66] J Guerin M Bendahan and K Aguir ldquoA dynamic responsemodel for theWO

3-based ozone sensorsrdquo Sensors andActuators

B Chemical vol 128 no 2 pp 462ndash467 2008[67] R BoulmaniM Bendahan C Lambert-MauriatM Gillet and

K Aguir ldquoCorrelation between rf-sputtering parameters andWO3sensor response towards ozonerdquo Sensors and Actuators B

Chemical vol 125 no 2 pp 622ndash627 2007[68] A Labidi M Gaidi J Guerin A Bejaoui M Maaref and

K Aguir ldquoAlternating current investigation and modeling ofthe temperature and ozone effects on the grains and the grainboundary contributions to the WO

3sensor responsesrdquo Thin

Solid Films vol 518 no 1 pp 355ndash361 2009[69] A Labidi C Jacolin M Bendahan et al ldquoImpedance spec-

troscopy on WO3gas sensorrdquo Sensors and Actuators B Chemi-

cal vol 106 no 2 pp 713ndash718 2005[70] J Guerin K Aguir M Bendahan and C Lambert-Mauriat

ldquoThermal modelling of a WO3ozone sensor responserdquo Sensors

and Actuators B Chemical vol 104 no 2 pp 289ndash293 2005[71] A C Catto L F da Silva C Ribeiro et al ldquoAn easy method

of preparing ozone gas sensors based on ZnO nanorodsrdquo RSCAdvances vol 5 no 25 pp 19528ndash19533 2015

[72] M Acuautla S Bernardini M Bendahan and E Pietri ldquoThick-ness effects of ZnO thin films on flexible ozone sensorsrdquo inProceedings of 10th Conference on Research in Microelectronicsand Electronics (PRIME rsquo14) pp 1ndash4 IEEE Grenoble FranceJune 2014

[73] K Galatsis Y X Li W Wlodarski et al ldquoComparison of singleand binary oxide MoO

3 TiO

2and WO

3sol-gel gas sensorsrdquo

Sensors and Actuators B Chemical vol 83 no 1ndash3 pp 276ndash2802002

[74] M Debliquy C Baroni A Boudiba J-M Tulliani M Olivierand C Zhang ldquoSensing characteristics of hematite and bariumoxide doped hematite films towards ozone and nitrogen diox-iderdquo Procedia Engineering vol 25 pp 219ndash222 2011

[75] Y Hosoya Y Itagaki H Aono and Y Sadaoka ldquoOzonedetection in air using SmFeO

3gas sensorrdquo Sensors andActuators

B Chemical vol 108 no 1-2 pp 198ndash201 2005[76] T Takada and K Komatsu ldquoOzone detection by In

23thin

films gas sensorrdquo in Proceedings of the 4th International Confer-ence on Solid State Sensors and Actuators pp 693ndash696 TokyoJapan June 1987

[77] T Takada ldquoOzone detection by In23thin films gas sensorrdquo in

Chemical Sensor Technology Kodansha T Seiyama Ed vol 2pp 59ndash70 Elsevier Tokyo Japan 1989

[78] D F Cox T B Fryberger and S Semancik ldquoOxygen vacanciesand defect electronic states on the SnO

2(110)-1 times 1 surfacerdquo

Physical Review B vol 38 pp 2072ndash2083 1988[79] K Tabata T Kawabe Y Yamaguchi and Y Nagasawa ldquoChemi-

sorbed oxygen species over the (110) face of SnO2rdquo Catalysis

Surveys from Asia vol 7 no 4 pp 251ndash259 2003[80] P Agoston Point defect and surface properties of In

2O3and

SnO2 a comparative study by first-principles methods [PhD the-

sis] Technische Universitat Darmstadt Darmstadt Germany2011

[81] Th Becker S Ahlers C Bosch-v Braunmuhl G Muller and OKiesewetter ldquoGas sensing properties of thin- and thick-film tin-oxide materialsrdquo Sensors and Actuators B Chemical vol 77 no1-2 pp 55ndash61 2001

[82] S-R Kim H-K Hong C H Kwon D H Yun K Leeand Y K Sung ldquoOzone sensing properties of In

2O3-based

semiconductor thick filmsrdquo Sensors and Actuators B Chemicalvol 66 no 1 pp 59ndash62 2000


[83] W Gopel ldquoChemisorption and charge transfer at ionic semi-conductor surfaces implications in designing gas sensorsrdquoProgress in Surface Science vol 20 no 1 pp 9ndash103 1985

[84] M Egashira ldquoAn overview on semiconductor gas sensorsrdquoin Proceedings of the Symposium on Chemical Sensors andProceedings of the Electrochemical Society (ECS rsquo87) D RTurner Ed vol 87ndash89 pp 39ndash48 Pennington NJ USA 1987

[85] G Sberveglieri Ed Gas Sensors Kluwer Academic PublishersDordrecht The Netherlands 1992

[86] N Barsan M Schweizer-Berberich and W Gopel ldquoFunda-mental and practical aspects in the design of nanoscaled SnO

2

gas sensors a status reportrdquo Freseniusrsquo Journal of AnalyticalChemistry vol 365 no 4 pp 287ndash304 1999

[87] W Gopel and G Reinhardt ldquoMetal oxide sensors new devicesthrough tailoring interfaces on the atomic scalerdquo in SensorsUpdate Sensor TechnologymdashApplications Markets H Baltes WGopel and J Hesse Eds vol 1 pp 49ndash120 VCH PublishersWeinheim Germany 1996

[88] A Gurlo N Barsan and U Weimar ldquoGas sensors based onsemiconducting metal oxidesrdquo inMetal Oxides Chemistry andApplications J L G Fierro Ed Marcel Dekker New York NYUSA 2004

[89] E Comini G Faglia and G Sberveglieri Eds Solid State GasSensing Springer New York NY USA 2009

[90] G Korotcenkov V Brinzari A Cerneavschi et al ldquoIn2O3films

deposited by spray pyrolysis gas response to reducing (CO H2)

gasesrdquo Sensors and Actuators B Chemical vol 98 no 2-3 pp122ndash129 2004

[91] T Doll A Fuchs I Eisele G Faglia S Groppelli and GSberveglieri ldquoConductivity and work function ozone sensorsbased on indium oxiderdquo Sensors and Actuators B Chemical vol49 no 1-2 pp 63ndash67 1998

[92] V RMastelaro S C Zılio L F da Silva et al ldquoOzone gas sensorbased on nanocrystalline SrTi

1minus119909Fe119909O3thin filmsrdquo Sensors and

Actuators B Chemical vol 181 pp 919ndash924 2013[93] A Bejaoui J Guerin J A Zapien and K Aguir ldquoTheoretical

and experimental study of the response of CuO gas sensorunder ozonerdquo Sensors and Actuators B Chemical vol 190 pp8ndash15 2014

[94] L F da Silva A C Catto W Avansi Jr et al ldquoA novelozone gas sensor based on one-dimensional (1D) 120572-Ag

2WO4

nanostructuresrdquo Nanoscale vol 6 no 8 pp 4058ndash4062 2014[95] G Korotcenkov V Golovanov V Brinzari A Cornet J

Morante and M Ivanov ldquoDistinguishing feature of metaloxide filmsrsquo structural engineering for gas sensor applicationsrdquoJournal of Physics Conference Series vol 15 no 1 pp 256ndash2612005

[96] A Walsh and C R A Catlow ldquoStructure stability and workfunctions of the low index surfaces of pure indium oxide andSn-doped indium oxide (ITO) from density functional theoryrdquoJournal of Materials Chemistry vol 20 no 46 pp 10438ndash104442010

[97] G Korotcenkov ldquoThe role of morphology and crystallographicstructure of metal oxides in response of conductometric-typegas sensorsrdquo Materials Science and Engineering R Reports vol61 no 1ndash6 pp 1ndash39 2008

[98] G Korotcenkov and B K Cho ldquoThe role of grain size on thethermal instability of nanostructured metal oxides used in gassensor applications and approaches for grain-size stabilizationrdquoProgress in Crystal Growth and Characterization of Materialsvol 58 no 4 pp 167ndash208 2012

[99] G Korotcenkov A Cornet E Rossinyol J Arbiol V Brin-zari and Y Blinov ldquoFaceting characterization of tin dioxidenanocrystals deposited by spray pyrolysis from stannic chloridewater solutionrdquo Thin Solid Films vol 471 no 1-2 pp 310ndash3192005

[100] G Korotcenkov M Dibattista J Schwank and V BrinzarildquoStructural characterization of SnO

2gas sensing films deposited

by spray pyrolysisrdquoMaterials Science and Engineering B vol 77no 1 pp 33ndash39 2000

[101] G Korotcenkov A Cerneavschi V Brinzari et al ldquoCrystal-lographic characterization of In

2O3films deposited by spray

pyrolysisrdquo Sensors and Actuators B Chemical vol 84 no 1 pp37ndash42 2002

[102] G Korotcenkov V Brinzari M Ivanov et al ldquoStructuralstability of indium oxide films deposited by spray pyrolysisduring thermal annealingrdquo Thin Solid Films vol 479 no 1-2pp 38ndash51 2005

[103] P Agoston and K Albe ldquoThermodynamic stability stoichiom-etry and electronic structure of bcc-In

2O3surfacesrdquo Physical

Review B vol 84 no 4 Article ID 045311 2011[104] K H L Zhang A Walsh C R A Catlow V K Lazarov and

R G Egdell ldquoSurface energies control the self-organization oforiented In

2O3nanostructures on cubic zirconiardquoNano Letters

vol 10 no 9 pp 3740ndash3746 2010[105] M Batzill and U Diebold ldquoThe surface andmaterials science of

tin oxiderdquo Progress in Surface Science vol 79 no 2ndash4 pp 47ndash154 2005

[106] C Xu J Tamaki N Miura and N Yamazoe ldquoGrain size effectson gas sensitivity of porous SnO

2-based elementsrdquo Sensors and

Actuators B Chemical vol 3 no 2 pp 147ndash155 1991[107] X Wang S S Yee and W P Carey ldquoTransition between neck

controlled and grain-boundary-controlled sensitivity of metaloxide gas sensorsrdquo Sensors and Actuators B Chemical vol 25no 1ndash3 pp 454ndash457 1995

[108] A Rothschild and Y Komem ldquoThe effect of grain size on thesensitivity of nanocrystalline metal-oxide gas sensorsrdquo Journalof Applied Physics vol 95 no 11 pp 6374ndash6380 2004

[109] G Korotcenkov S D Han B K Cho and V Brinzari ldquoGrainsize effects in sensor response of nanostructured SnO

2- and

In2O3-based conductometric gas sensorrdquo Critical Reviews in

Solid State andMaterials Sciences vol 34 no 1-2 pp 1ndash17 2009[110] Y Hao G Meng C Ye and L Zhang ldquoControlled synthesis of

In2O3octahedrons and nanowiresrdquo Crystal Growth and Design

vol 5 no 4 pp 1617ndash1621 2005[111] M Shi F Xu K Yu Z Zhu and J Fang ldquoControllable synthesis

of In2O3nanocubes truncated nanocubes and symmetric

multipodsrdquo Journal of Physical Chemistry C vol 111 no 44 pp16267ndash16271 2007

[112] A Gurlo ldquoNanosensors towards morphological control of gassensing activity SnO

2 In2O3 ZnO and WO

3case studiesrdquo

Nanoscale vol 3 no 1 pp 154ndash165 2011[113] G Korotcenkov S H Han and B K Cho ldquoMaterial design

for metal oxide chemiresistive gas sensorsrdquo Journal of SensorScience and Technology vol 22 no 1 pp 1ndash17 2013

[114] V Brinzari G Korotcenkov J Schwank V Lantto S Saukkoand V Golovanov ldquoMorphological rank of nano-scale tindioxide films deposited by spray pyrolysis from SnCl

4∙5H2O

water solutionrdquo Thin Solid Films vol 408 no 1-2 pp 51ndash582002


[115] G Korotcenkov I Boris A Cornet et al ldquoThe influence ofadditives on gas sensing and structural properties of In

2O3-

based ceramicsrdquo Sensors and Actuators B Chemical vol 120 no2 pp 657ndash664 2007

[116] G Korotcenkov V Brinzari V Golovanov and Y BlinovldquoKinetics of gas response to reducing gases of SnO

2films

deposited by spray pyrolysisrdquo Sensors and Actuators B Chem-ical vol 98 no 1 pp 41ndash45 2004

[117] I Lundstrom ldquoApproaches andmechanisms to solid state basedsensingrdquo Sensors and Actuators B Chemical vol 35 no 1ndash3 pp11ndash19 1996

[118] A Gurlo N Barsan U Weimar M Ivanovskaya A Taurinoand P Siciliano ldquoPolycrystalline well-shaped blocks of indiumoxide obtained by the sol-gel method and their gas-sensingpropertiesrdquo Chemistry of Materials vol 15 no 23 pp 4377ndash4383 2003

[119] T Wagner J Hennemann C-D Kohl and M Tiemann ldquoPho-tocatalytic ozone sensor based on mesoporous indium oxideinfluence of the relative humidity on the sensing performancerdquoThin Solid Films vol 520 no 3 pp 918ndash921 2011

[120] T Takada H Tanjou T Saito and K Harada ldquoAqueous ozonedetector using In

2O3thin-film semiconductor gas sensorrdquo

Sensors and Actuators B Chemical vol 24-25 no 1ndash3 pp 548ndash551 1995

[121] C Y Wang S Bagchi M Bitterling et al ldquoPhoton stimulatedozone sensor based on indium oxide nanoparticles II ozonemonitoring in humidity and water environmentsrdquo Sensors andActuators B Chemical vol 164 no 1 pp 37ndash42 2012

[122] A Hattori H Tachibana N Yoshiike and A Yoshida ldquoOzonesensor made by dip coating methodrdquo Sensors and Actuators APhysical vol 77 no 2 pp 120ndash125 1999

[123] A Gurlo N Barsan M Ivanovskaya U Weimar and WGopel ldquoIn

2O3and MoO

3ndashIn2O3thin film semiconductor

sensors interaction with NO2and O

3rdquo Sensors and Actuators

B Chemical vol 47 no 1 pp 92ndash99 1998[124] J Frank M Fleischer M Zimmer and H Meixner ldquoOzone

sensing using In2O3-modified Ga

2O3thin filmsrdquo IEEE Sensors

Journal vol 1 no 4 pp 318ndash321 2001[125] P K Clifford andD T Tuma ldquoCharacteristics of semiconductor

gas sensors I Steady state gas responserdquo Sensors and Actuatorsvol 3 pp 233ndash254 1982

[126] S Strassler and A Reis ldquoSimple models for N-type metal oxidegas sensorsrdquo Sensors and Actuators vol 4 pp 465ndash472 1983

[127] S R Morrison ldquoMechanism of semiconductor gas sensoroperationrdquo Sensors and Actuators vol 11 no 3 pp 283ndash2871987

[128] J F McAleer P T Moseley J O W Norris and D E WilliamsldquoTin dioxide gas sensors Part 1mdashaspects of the surface chem-istry revealed by electrical conductance variationsrdquo Journal ofthe Chemical Society Faraday Transactions 1 Physical Chemistryin Condensed Phases vol 83 no 4 pp 1323ndash1346 1987

[129] D E Williams and K F E Pratt ldquoMicrostructure effects onthe response of gas-sensitive resistors based on semiconductingoxidesrdquo Sensors and Actuators B Chemical vol 70 no 1ndash3 pp214ndash221 2000

[130] G Chabanis I P Parkin and D E Williams ldquoA simpleequivalent circuit model to represent microstructure effectson the response of semiconducting oxide-based gas sensorsrdquoMeasurement Science and Technology vol 14 no 1 pp 76ndash862003

[131] V Brinzari M Ivanov B K Cho M Kamei and G Korot-cenkov ldquoPhotoconductivity in In

2O3nanoscale thin films

interrelation with chemisorbed-type conductometric responsetowards oxygenrdquo Sensors and Actuators B Chemical vol 148no 2 pp 427ndash438 2010

[132] G Munuera V Rives-Arnau and A Saucedo ldquoPhoto-adsorption and photo-desorption of oxygen on highlyhydroxylated TiO

2surfaces Part 1mdashrole of hydroxyl groups

in photo-adsorptionrdquo Journal of the Chemical Society FaradayTransactions 1 vol 75 pp 736ndash747 1979

[133] D E Williams S R Aliwell K F E Pratt et al ldquoModellingthe response of a tungsten oxide semiconductor as a gassensor for themeasurement of ozonerdquoMeasurement Science andTechnology vol 13 no 6 pp 923ndash931 2002

[134] J Guerin K Aguir and M Bendahan ldquoModeling of theconduction in a WO

3thin film as ozone sensorrdquo Sensors and

Actuators B Chemical vol 119 no 1 pp 327ndash334 2006[135] V V Lunin M P Popovich and S N Tkachenko Physical

Chemistry of Ozone Moscow State University Moscow Russia1998 (Russian)

[136] K M Bulanin J C Lavalley and A A Tsyganenko ldquoInfraredstudy of ozone adsorption on TiO

2(anatase)rdquo Journal of

Physical Chemistry vol 99 no 25 pp 10294ndash10298 1995[137] B Dhandapani and S T Oyama ldquoGas phase ozone decomposi-

tion catalystsrdquo Applied Catalysis B Environmental vol 11 no 2pp 129ndash166 1997

[138] A Banichevich S D Peyerimhoff and F Grein ldquoAb initiopotential surfaces for ozone dissociation in its ground andvarious electronically excited statesrdquo Chemical Physics Lettersvol 173 no 1 pp 1ndash6 1990

[139] M Allan K R Asmis D B Popovic M Stepanovic N JMason and J A Davies ldquoProduction of vibrationally autode-taching O

2- in low-energy electron impact on ozonerdquo Journal

of Physics B Atomic Molecular and Optical Physics vol 29 no15 pp 3487ndash3495 1996

[140] A Naydenov R Stoyanova andDMehandjiev ldquoOzone decom-position and CO oxidation on CeO

2rdquo Journal of Molecular

Catalysis A Chemical vol 98 no 1 pp 9ndash14 1995[141] T Doll J Lechner I Eisele K-D Schierbaum and W Gopel

ldquoOzone detection in the ppb range with work function sensorsoperating at room temperaturerdquo Sensors and Actuators BChemical vol 34 no 1ndash3 pp 506ndash510 1996

[142] D E Williams and K F E Patt ldquoClassification of reactivesites on the surface of polycrystalline tin dioxiderdquo Journal ofthe Chemical Society Faraday Transactions vol 94 no 23 pp3493ndash3500 1998

[143] M Calatayud A Markovits M Menetrey B Mguig and CMinot ldquoAdsorption on perfect and reduced surfaces of metaloxidesrdquo Catalysis Today vol 85 no 2ndash4 pp 125ndash143 2003

[144] F Trani M Causa D Ninno G Cantele and V BaroneldquoDensity functional study of oxygen vacancies at the SnO

2

surface and subsurface sitesrdquo Physical Review B vol 77 no 24Article ID 245410 2008

[145] A Rothschild Y Komem and F Cosandey ldquoLow temperaturereoxidation mechanism in nanocrystalline TiO

2minus120575thin films

thin filmsrdquo Journal of the Electrochemical Society vol 148 no8 pp H85ndashH89 2001

[146] J Jamnik B Kamp R Merkle and J Maier ldquoSpace chargeinfluenced oxygen incorporation in oxides in how far does itcontribute to the drift of Taguchi sensorsrdquo Solid State Ionicsvol 150 no 1-2 pp 157ndash166 2002


[147] J Fleig R Merkle and J Maier ldquoThe p(O2) dependence of

oxygen surface coverage and exchange current density of mixedconducting oxide electrodes model considerationsrdquo PhysicalChemistry Chemical Physics vol 9 no 21 pp 2713ndash2723 2007

[148] S B Adler X Y Chen and J R Wilson ldquoMechanisms and ratelaws for oxygen exchange onmixed-conducting oxide surfacesrdquoJournal of Catalysis vol 245 no 1 pp 91ndash109 2007

[149] R Merkle and J Maier ldquoHow is oxygen incorporated intooxides A comprehensive kinetic study of a simple solid-state reaction with SrTiO

3as a model materialrdquo Angewandte

ChemiemdashInternational Edition vol 47 no 21 pp 3874ndash38942008

[150] C Korber A Wachau P Agoston K Albe and A Klein ldquoSelf-limited oxygen exchange kinetics at SnO

2surfacesrdquo Physical

Chemistry Chemical Physics vol 13 no 8 pp 3223ndash3226 2011[151] M Himmerlich Surface characterization of indium compounds

as functional layers for (opto)electronic and sensoric applications[PhD thesis] Technische Universitat Ilmenau Ilmenau Ger-many 2008

[152] P G Harrison and M J Willett ldquoTin oxide surfaces Part20mdashelectrical properties of tin(IV) oxide gel nature of thesurface species controlling the electrical conductance in air asa function of temperaturerdquo Journal of the Chemical SocietyFaradayTransactions 1 Physical Chemistry inCondensed Phasesvol 85 no 8 pp 1921ndash1932 1989

[153] M Vahedpour M Tozihi and F Nazari ldquoMechanistic studyof ozone-water reaction and their reaction products with gasphase elemental mercury a computational studyrdquo ChineseJournal of Chemistry vol 28 no 7 pp 1103ndash1113 2010

[154] V Brinzari G Korotcenkov K Veltruska V Matolin N Tsudand J Schwank ldquoXPS study of gas sensitive SnO

2thin filmsrdquo in

Proceedings of the Semiconductor International Conference (CASrsquo00) vol 1 pp 127ndash130 Sinaia Romania October 2000

[155] V M Bermudez A D Berry H Kim and A Pique ldquoFunc-tionalization of indium tin oxiderdquo Langmuir vol 22 no 26 pp11113ndash11125 2006

[156] K Ip B P Gila A H Onstine et al ldquoEffect of ozone cleaning onPtAu and WPtAu Schottky contacts to n-type ZnOrdquo AppliedSurface Science vol 236 no 1 pp 387ndash393 2004

[157] M Tominaga N Hirata and I Taniguchi ldquoUV-ozone dry-cleaning process for indium oxide electrodes for protein elec-trochemistryrdquo Electrochemistry Communications vol 7 no 12pp 1423ndash1428 2005

[158] M Himmerlich C Y Wang V Cimalla O Ambacher andS Krischok ldquoSurface properties of stoichiometric and defect-rich indium oxide films grown by MOCVDrdquo Journal of AppliedPhysics vol 111 no 9 Article ID 093704 2012

[159] FWolkensteinThe ElectronTheory of Catalysis on Semiconduc-tors Macmillan Publishers New York NY USA 1963

[160] T Wolkenstein Electronic Processes on Semiconductor SurfacesDuring Chemisorption Springer New York NY USA 1991

[161] M O Conaire H J Curran J M Simmie W J Pitz and CK Westbrook ldquoA comprehensive modeling study of hydrogenoxidationrdquo International Journal of Chemical Kinetics vol 36no 11 pp 603ndash622 2004

[162] A K Gatin M V Grishin A A Kirsankin L I Trakhtenbergand B R Shub ldquoAdsorption of oxygen and hydrogen at thesurface of nanostructured SnO

2filmrdquo Nanotechnologies in

Russia vol 7 no 3-4 pp 122ndash126 2012

[163] C Y Wang R W Becker T Passow et al ldquoPhoton stim-ulated sensor based on indium oxide nanoparticles I wide-concentration-range ozone monitoring in airrdquo Sensors andActuators B Chemical vol 152 no 2 pp 235ndash240 2011

[164] EGagaoudakisM Bender EDouloufakis et al ldquoThe influenceof deposition parameters on room temperature ozone sensingproperties of InOx filmsrdquo Sensors and Actuators B Chemicalvol 80 no 2 pp 155ndash161 2001

[165] M Epifani E Comini J Arbiol et al ldquoNanocrystals as veryactive interfaces ultrasensitive room-temperature ozone sen-sors with in

2o3nanocrystals prepared by a low-temperature sol-

gel process in a coordinating environmentrdquo Journal of PhysicalChemistry C vol 111 no 37 pp 13967ndash13971 2007

[166] A Gaddari F Berger M Amjoud et al ldquoA novel way for thesynthesis of tin dioxide solndashgel derived thin films applicationto O3detection at ambient temperaturerdquo Sensors and Actuators

B Chemical vol 176 pp 811ndash817 2013[167] F Berger B Ghaddab J B Sanchez and C Mavon ldquoDevel-

opment of an ozone high sensitive sensor working at ambienttemperaturerdquo Journal of Physics Conference Series vol 307 no1 Article ID 012054 2011

[168] G Kiriakidis K Moschovis I Kortidis and R SkarvelakisldquoHighly sensitive InO

119909ozone sensing films on flexible sub-

stratesrdquo Journal of Sensors vol 2009 Article ID 727893 5 pages2009

[169] Ch Y Wang V Cimalla C-C Roehlig et al ldquoA new typeof highly sensitive portable ozone sensor operating at roomtemperaturerdquo in Proceedings of the 5th IEEE Conference onSensors pp 81ndash84 EXCO Daegu South Korea October 2006

[170] G Kiriakidis M Bender N Katsarakis et al ldquoOzone sensingproperties of polycrystalline indium oxide films at room tem-peraturerdquo Physica Status Solidi (A) vol 185 no 1 pp 27ndash322001

[171] M Suchea N Katsarakis S Christoulakis S Nikolopoulouand G Kiriakidis ldquoLow temperature indium oxide gas sensorsrdquoSensors and Actuators B Chemical vol 118 no 1-2 pp 135ndash1412006

[172] J D Prades R Jimenez-Diaz M Manzanares et al ldquoA modelfor the response towards oxidizing gases of photoactivated sen-sors based on individual SnO

2nanowiresrdquo Physical Chemistry

Chemical Physics vol 11 no 46 pp 10881ndash10889 2009[173] M Bender N Katsarakis E Gagaoudakis et al ldquoDependence

of the photoreduction and oxidation behavior of indium oxidefilms on substrate temperature and film thicknessrdquo Journal ofApplied Physics vol 90 no 10 pp 5382ndash5387 2001

[174] M Suchea N Katsarakis S Christoulakis M Katharakis TKitsopoulos and G Kiriakidis ldquoMetal oxide thin films assensing layers for ozone detectionrdquoAnalytica Chimica Acta vol573-574 pp 9ndash13 2006

[175] D Klaus D Klawinski S AmrehnM Tiemann andTWagnerldquoLight-activated resistive ozone sensing at room temperatureutilizing nanoporous In

2O3particles influence of particle sizerdquo

Sensors and Actuators B Chemical vol 217 pp 181ndash185 2015[176] Ch Y Wang V Cimalla Th Kups et al ldquoPhotoreduction and

oxidation behavior of In2O3nanoparticles by metal organic

chemical vapor depositionrdquo Journal of Applied Physics vol 102no 4 Article ID 044310 2007

[177] C Y Wang V Cimalla M Kunzer et al ldquoNear-UV LEDs forintegrated InO-based ozone sensorsrdquo Physica Status Solidi (C)vol 7 no 7-8 pp 2177ndash2179 2010

[178] C-C Jeng P J H Chong C-C Chiu et al ldquoA dynamicequilibrium method for the SnO

2-based ozone sensors using


UV-LED continuous irradiationrdquo Sensors and Actuators BChemical vol 195 pp 702ndash706 2014

[179] S Mills M Lim B Lee and V Misra ldquoAtomic layer depositionof SnO

2for selective room temperature low ppb level O

3

sensingrdquo ECS Journal of Solid State Science and Technology vol4 no 10 pp S3059ndashS3061 2015

[180] R-J Wu C-Y Chen M-H Chen and Y-L Sun ldquoPhotore-duction measurement of ozone using PtTiO

2ndashSnO

2material

at room temperaturerdquo Sensors and Actuators B Chemical vol123 no 2 pp 1077ndash1082 2007

[181] M Bender E Gagaoudakis E Douloufakis et al ldquoProductionand characterization of zinc oxide thin films for room temper-ature ozone sensingrdquoThin Solid Films vol 418 no 1 pp 45ndash502002

[182] F S-S Chien C-R Wang Y-L Chan H-L Lin M-H Chenand R-J Wu ldquoFast-response ozone sensor with ZnO nanorodsgrown by chemical vapor depositionrdquo Sensors and Actuators BChemical vol 144 no 1 pp 120ndash125 2010

[183] M C Carotta A Cervi A Fioravanti et al ldquoA novel ozonedetection at room temperature through UV-LED-assisted ZnOthick film sensorsrdquoThin Solid Films vol 520 no 3 pp 939ndash9462011

[184] K L Chen G J Jiang K W Chang J H Chen and C HWu ldquoGas sensing properties of indiumndashgalliumndashzincndashoxidegas sensors in different light intensityrdquo Analytical ChemistryResearch vol 4 pp 8ndash12 2015

[185] M-H Chen C-S Lu and R-J Wu ldquoNovel PtTiO2ndashWO

3

materials irradiated by visible light used in a photoreductiveozone sensorrdquo Journal of the Taiwan Institute of ChemicalEngineers vol 45 no 3 pp 1043ndash1048 2014

[186] M Augustin M Sommer and V V Sysoev ldquoUVndashVIS sensorsystem based on SnO

2nanowiresrdquo Sensors and Actuators A

Physical vol 210 pp 205ndash208 2014[187] H Chen C O Stanier M A Young and V H Grassian ldquoA

kinetic study of ozone decomposition on illuminated oxidesurfacesrdquo Journal of Physical Chemistry A vol 115 no 43 pp11979ndash11987 2011

[188] P Kofstad Non-Stoichiometry Diffusion and Electrical Conduc-tivity in Binary Metal Oxides Wiley New York NY USA 1972

[189] M Caldararu D Sprınceana V T Popa andN I Ionescu ldquoSur-face dynamics in tin dioxide-containing catalysts II Competi-tion between water and oxygen adsorption on polycrystallinetin dioxiderdquo Sensors and Actuators B Chemical vol 30 no 1pp 35ndash41 1996

[190] G Korotcenkov V Brinzari Y Boris M Ivanov J Schwankand J Morante ldquoInfluence of surface Pd doping on gas sensingcharacteristics of SnO

2thin films deposited by spray pirolysisrdquo

Thin Solid Films vol 436 no 1 pp 119ndash126 2003[191] D Koziej N Barsan U Weimar J Szuber K Shimanoe and

N Yamazoe ldquoWaterndashoxygen interplay on tin dioxide surfaceimplication on gas sensingrdquo Chemical Physics Letters vol 410no 4ndash6 pp 321ndash323 2005

[192] G Korotchenkov V Brynzari and S Dmitriev ldquoElectricalbehavior of SnO

2thin films in humid atmosphererdquo Sensors and

Actuators B Chemical vol 54 no 3 pp 197ndash201 1999[193] V E Henrich and P A CoxThe Surface Science ofMetal Oxides

Cambridge University Press New York NY USA 1994[194] A R Gonzalez-Elipe G Munuera and J Soria ldquoPhoto-

adsorption and photo-desorption of oxygen on highly hydrox-ylated TiO

2surfaces Part 2mdashstudy of radical intermediates by

electron paramagnetic resonancerdquo Journal of the Chemical Soci-ety Faraday Transactions 1 Physical Chemistry in CondensedPhases vol 75 pp 748ndash761 1979

[195] C Sivadinarayana TVChoudhary L LDaemen J Eckert andD W Goodman ldquoThe nature of the surface species formed onAuTiO

2during the reaction of H

2and O

2 an inelastic neutron

scattering studyrdquo Journal of the American Chemical Society vol126 no 1 pp 38ndash39 2004

[196] M Addamo V Augugliaro E Garcıa-Lopez V Loddo GMarcı and L Palmisano ldquoOxidation of oxalate ion in aqueoussuspensions of TiO

2by photocatalysis and ozonationrdquoCatalysis

Today vol 107-108 pp 612ndash618 2005[197] M Egashira M Nakashima S Kawasumi and T Selyama

ldquoTemperature programmed desorption study of water adsorbedon metal oxides 2 Tin oxide surfacerdquo The Journal of PhysicalChemistry vol 85 pp 4125ndash4130 1981

[198] V A Gercher and D F Cox ldquoWater adsorption on stoichiomet-ric and defective SnO

2(110) surfacesrdquo Surface Science vol 322

no 1ndash3 pp 177ndash184 1995[199] E Leblanc L Perier-Camby G Thomas R Gibert M Primet

and P Gelin ldquoNO119909adsorption onto dehydroxylated or hydrox-

ylated tin dioxide surface Application to SnO2-based sensorsrdquo

Sensors andActuators B Chemical vol 62 no 1 pp 67ndash72 2000[200] M Z Atashbar B Gong H T SunWWlodarski and R Lamb

ldquoInvestigation on ozone-sensitive In2O3thin filmsrdquo Thin Solid

Films vol 354 no 1 pp 222ndash226 1999[201] J W Gardner ldquoA non-linear diffusion-reaction model of elec-

trical conduction in semiconductor gas sensorsrdquo Sensors andActuators B Chemical vol 1 no 1ndash6 pp 166ndash170 1990

[202] D E Williams G S Henshaw K F E Pratt and RPeat ldquoReaction-diffusion effects and systematic design of gas-sensitive resistors based on semiconducting oxidesrdquo Journal ofthe Chemical Society Faraday Transactions vol 91 no 23 pp4299ndash4307 1995

[203] D E Williams and K F E Pratt ldquoTheory of self-diagnosticsensor array devices using gas-sensitive resistorsrdquo Journal of theChemical Society Faraday Transactions vol 91 no 13 pp 1961ndash1966 1995

[204] H Lu W Ma J Gao and J Li ldquoDiffusion-reaction theory forconductance response in metal oxide gas sensing thin filmsrdquoSensors and Actuators B Chemical vol 66 no 1 pp 228ndash2312000

[205] X Vilanova E Llobet R Alcubilla J E Sueiras and X CorreigldquoAnalysis of the conductance transient in thick-film tin oxidegas sensorsrdquo Sensors and Actuators B Chemical vol 31 no 3pp 175ndash180 1996

[206] G Sakai NMatsunaga K Shimanoe andN Yamazoe ldquoTheoryof gas-diffusion controlled sensitivity for thin film semiconduc-tor gas sensorrdquo Sensors and Actuators B Chemical vol 80 no2 pp 125ndash131 2001

[207] S Nakata K Takemura and K Neya ldquoNon-linear dynamicresponses of a semiconductor gas sensor evaluation of kineticparameters and competition effect on the sensor responserdquoSensors and Actuators B Chemical vol 76 no 1ndash3 pp 436ndash4412001

[208] E Llobet X Vilanova J Brezmes J E Sueiras R Alcubilla andX Correig ldquoSteady-state and transient behavior of thick-filmtin oxide sensors in the presence of gas mixturesrdquo Journal of theElectrochemical Society vol 145 no 5 pp 1772ndash1779 1998


[209] W Zhixiang M Fenzhu S Yiqiang Z Ming and Y GuocongldquoA method for the measurement of gas concentration distribu-tion in the adsorptive bedrdquo Chemical Engineering Science vol54 no 23 pp 5755ndash5760 1999

[210] Y Shimizu TMaekawa YNakamura andM Egashira ldquoEffectsof gas diffusivity and reactivity on sensing properties of thickfilm SnO

2-based sensorsrdquo Sensors and Actuators B Chemical

vol 46 no 3 pp 163ndash168 1998[211] G Korotchenkov V Brynzari and S Dmitriev ldquoKinetics

characteristics of SnO2thin film gas sensors for environmental

monitoringrdquo in Chemical Microsensors and Applications SBuettgenbach Ed vol 3539 of Proceedings of SPIE pp 196ndash204December 1998

[212] V Brynzari G Korotchenkov and S Dmitriev ldquoSimulationof thin film gas sensors kineticsrdquo Sensors and Actuators BChemical vol 61 no 1 pp 143ndash153 1999

[213] A Setkus ldquoHeterogeneous reaction rate based description ofthe response kinetics in metal oxide gas sensorsrdquo Sensors andActuators B Chemical vol 87 no 2 pp 346ndash357 2002

[214] V P Zhdanov ldquoImpact of surface science on the understandingof kinetics of heterogeneous catalytic reactionsrdquo Surface Sciencevol 500 pp 965ndash984 2002

[215] H J Kreuzer ldquoTheory of surface processesrdquo Applied Physics Avol 51 no 6 pp 491ndash497 1990

[216] C Xu and B E Koel ldquoAdsorption kinetics on chemically modi-fied or bimetallic surfacesrdquoThe Journal of Chemical Physics vol100 no 1 pp 664ndash670 1994

[217] U Brossmann U Sodervall R Wurschum and H Schaeferldquo 18O Diffusion in nano crystalline ZrO

2rdquo Nanostructured

Materials vol 12 no 5ndash8 pp 871ndash874 1999[218] Y Ikuma and T Murakami ldquoOxygen tracer diffusion in poly-

crystalline In2O3rdquo Journal of the Electrochemical Society vol

143 no 8 pp 2698ndash2702 1996[219] H Yamaura T Jinkawa J Tamaki K Moriya N Miura

and N Yamazoe ldquoIndium oxide-based gas sensor for selectivedetection of COrdquo Sensors and Actuators B Chemical vol 36 no1ndash3 pp 325ndash332 1996

[220] MHaneda Y Kintaichi N Bion andHHamada ldquoMechanisticstudy of the effect of coexisting H

2O on the selective reduction

of NO with propene over sol-gel prepared In2O3-Al2O3cata-

lystrdquo Applied Catalysis B Environmental vol 42 no 1 pp 57ndash68 2003

[221] J Berger I Riess and D S Tannhauser ldquoDynamic measure-ment of oxygen diffusion in indium-tin oxiderdquo Solid State Ionicsvol 15 no 3 pp 225ndash231 1985

[222] C N SatterfieldMass Transfer in Heterogeneous Catalysis MITPress Cambridge Mass USA 1970

[223] N Matsunaga G Sakai K Shimanoe and N Yamazoe ldquoFor-mulation of gas diffusion dynamics for thin film semiconductorgas sensor based on simple reactionndashdiffusion equationrdquo Sen-sors and Actuators B Chemical vol 96 no 1-2 pp 226ndash2332003

[224] J R Stetter ldquoA surface chemical view of gas detectionrdquo Journalof Colloid And Interface Science vol 65 no 3 pp 432ndash443 1978

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

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Control Scienceand Engineering

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The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

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Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014


Chemical EngineeringInternational Journal of Antennas and

Propagation




Navigation and Observation



DistributedSensor Networks



Ozonersquos advantages

Ozone is nativeecology clean oxidizer

Ozone annihilatesbiologically active

components in air and waterPreservation

of food

Cleaning and airdeodorization

Prevention of boththe mold and fungi

appearance

In contrast to chloride the useof ozone is not accompanied

by generation of thecarcinogenic substances

Ozone oxidizes heavy metalsand transforms sulphides and

nitrides in insoluble state

Annihilationof bad odor

Ozone therapy

Purification and disinfectionof air water and food

Possible fields of application

Food industry Environment control

Pharmaceutical industry

Water treatment

Chemical industry

Medicine

Figure 1 Advantages and possible fields of ozone applications

ozone due to its relatively short half-life (minutes in con-fined spaces) does not instantly diffuse in air to create auniform concentration for easy measurement Thereforein order to control the ozone concentration in the atmo-sphere and surrounding environment it is necessary todevelop both effective and economical methods and devicesfor the continuous monitoring of ozone concentrations atmultiple locations including technological processes withincorporated ozone treatments These methods are alsoneeded to determine attenuation of the ozone layer by man-made gases to validate model estimations of changes inozone layer and to confirm the efficiency of the MontrealProtocol on Substances that deplete the ozone Layer (httpozoneuneporgpdfsMontreal-Protocol2000pdf) As is wellknown in recent decades there has been the depletion of theozone layer which can negatively affect the life on EarthTheincrease in the number of articles devoted to the developmentand research of ozone sensors (see Figure 2) confirms theimportance of this issue Experiments have shown that ana-lytical techniques developed to solve these problems shouldbe capable of measuring ozone concentrations in the rangeof 001ndash10 ppm for these purposes For example ambient airmeasuring at the ground requires instruments with little ppbaccuracy in a range 20ndash200 ppb whereas in industrial andcommercial applications the precision is not so stringent andthe expected concentrations are higher (up to 10 ppm)

Num

ber o

f pub

licat

ions

120

110

100

90

80

70

60

50

402000 2005

Year2010 2015

Figure 2 The growth in the number of publications devoted to thedesign of ozone sensors Data extracted from Scopus

At present a number of conventional analytical methodssuch as UV absorbance optochemical optical chemilumi-nescence fluorescence and electrochemical methods areavailable for the accurate analysis of ozone concentration inthe air [14ndash17] However these sophisticated high accuracytechniques are advisable for application in both metropolitan





1ndash3020ndash200














5ndash10














3 SnO

2 ZnO MoO


2 ITO NiO SmFeO

3

Ga2O3In2O3


2 In2O3ZnOSnO

2 SnO

2-In2O3


2O3 ZnO PtTiO

2-SnO2


2O3 SnO

2SWNTs



2



2and In

2O3thin films


2and In

2O3are wide-band-


2O3- and SnO

2-based ozone




2 SO2


2O3and SnO

2also


In2O3and SnO





O2(g) larrrarr O

2(ad)


2

minus(ad)





O 999445999468 VO2++

1

2

O2+ 2eminus (2)

Sn 999445999468 Sni4++ 4eminus (3)


Table3Th

ebestp

aram

eterso

fcon

ductom

etric

heated

ozon

esensorsdesig

nedon

theb

aseo

fmetaloxides

Techno

logicalrou

teparam

eterso

fsensin

glayer

Maxsensorrespo

nse

Con

ditio

nsof

measurements

Respon

setim

eRe

covery

times

References

In2O3

Thickfilmdsim100n

mtsim12nm

sim3sdot102

85∘C

250p

pbdry

25ndash4

5sna

[35]


msim15

sdot103

300∘C

100p

pbdry

sim1m

insim10min

[5051]


msim(4ndash6

)sdot103

350∘C

76pp

bna

na

[33]

Thickfilmdsim20

120583mtsim20

nm120

270∘C

1ppm

dry

na

na

[52]

Thin

filmsdsim

30ndash50n

mtsim10ndash15n

m103ndash104

200ndash

300∘C

1ppm

lt2s

(280∘C)

sim20

s(280∘C)

[4344

5354]

Thin

filmsdmdash

natmdash

na

sim102

400∘C

60pp

b100m

in(250∘C)

60ndash80m

in(250∘C)

[46]

Thin

filmsdmdash

natmdash

na

sim3sdot102

370∘C

230p

pbna

na

[55]

SnO2

Thickfilmdsim100n

mtsim15nm

sim(3-4)sdot

102

120∘C

250p

pbdry

40ndash6

0sTens

ofminutes

[35]

Thin

filmsdsim

30ndash50n

mtsim10ndash15n

m103ndash104

200ndash

300∘C

1ppm

lt2s

(280∘C)

sim15min

(280∘C)

[455657]

Thin

filmsdsim

260n

mtmdashna

sim102

350∘C

135p

pbSeveralm

inutes

Severalm

inutes

[5859]

Thin

filmsdsim

300n

mtmdashna

sim10

350∘C

60pp

bna

na

[6061]

Thin

filmsdsim

20ndash30n

mtsim6ndash

8nm

sim103

320∘C

1ppm

lt2-3s

sim15min

[47]

Thin

filmsdsim

40ndash50n

m119905lt6ndash8

nmsim105

150∘C

1ppm

3-4s

(200∘C)

sim17min

(200∘C)

[62]

WO3


sim60

0180∘C

1ppm

sim15s

sim2m

in[35]


na

sim35

400∘C

80pp

bna

na

[63]

Thin

filmsdsim

100n

mtmdashna

sim6sdot102ndash7

sdot103

120∘C

90pp

bsim12s

1ndash3m

in[64]

Thin

filmsdsim

35ndash50n

mtsim20ndash100

nm5ndash300

250∘C

08p

pm05ndash2m

in2-3m

in[65ndash69]

Thin

filmsdsim

300n

mtmdashna

sim20

300∘C

200p

pbMinutes

Minutes

[63]

Thin

filmsdmdash

natsim20

nm15

sdot103

300∘C

500p

pbna

na

[70]

ZnO


msim8

250∘C

01p

pm14s

9s[71]

Thickfilmdsim275n

m119905mdashna

sim10ndash30

200∘C

300p

pbsim10s

sim2m

in[72]

MoO3-TiO2


17370∘C

100p

pbsim20

sna

[73]

Fe2O3

Thin

films119889sim500n

m119905mdashna

sim20

200∘C

05p

pm50

na

na

[74]

SmFeO3


sim102

285∘C

04p

pmsim1m

insim10min

[75]

dfilm

thickn

esstgrainsiz

esensor

respon

se(119877

ozon

e119877air)con

ditio

nsof

measurements

temperature

ofop

eration

gasc

oncentratio

nandhu

midity


Other oxides

WO3

ZnO SnO2

In2O3



Ominus O2minus

O2

0 200 300 400 500

Temperature (∘C)

O2minus

100




O2 + erarr2Ominus




2- and









2O3- and SnO

2-based



2O3or SnO




2







3was observed at


2- and



1minus119909Fe119909O3 120572-Ag

2WO4 and Fe

2O3 have maximum


2-


2)




In2O3

Ozone

CO

40nm

70nm60nm

200nm

200100 400 500300

Temperature (∘C)

100

101

102

103

Sens

or re

spon

se

RH sim 45


[43 44 90]





2and In

2O3








SnO2

(111) (200) (020) (112) (120) (110) (101) (011) (011) (101) (010) (001) (100)(110) (010) (010) (110) (100) (221) (221) (221) [99 112 113]






2O3and SnO

2thin films






(110)

(100)

(001)

(101)

SnO2

(a)

(111)

(100)

(110)

In2O3

(b)


2O3


Resp

onse

and

reco

very

tim

e (se

c)

Response

Recovery


103

102

101

100100 200 300 400

In2O3

SnO2

SnO2



2O3- and SnO





2O3



119878 sim (

120591rec120591res

)

119898

(4)



119878 =

119877

1198770

= 119870119862119883 (5)




11

8

3

2

6

4

9

12

107

13

1

5


Ozone

100

101

102

103

104

105

Sens

or re

spon

se





2O3







2O3(sol-









119878gt 0)



be expressed as

119878 =

119866

1198660

sim exp (119902Δ119881119878

119896119879

) lt 1 (6)


O

O

+

minus

O O O

O

+

minus







O3(g) 997888rarr O


3

minus(s) (7)

O3(g) 997888rarr O




3











3was




3




3


2O3



Sn Sn Sn

O

O O

O + O2O3



[136]



2O) A



O3+ VO∙∙+ 2e 999445999468 OO +O

2uarr (9)


2is valid for


2lattice


2

TiO2 and SrTiO










2O3lattice at



2-



2surface is shown


2surface









2uarr + eminus (10)


OH

R(air)

Con

cent

ratio

n (a

u)

Ozone

S

O2

H2O

O

100

101

102

103

Sens

or re

spon

se


105

107

109

Resis

tanc

e (O

hm)



2films



2lattice atoms has


2surface is




2and In

2O3[155 156] Inter-


2



O1s

Sn3d

(a)

(b)


Inte

nsity

of X

PS (O

1s C

1s a

nd S

n3d)

pea

ks (a

u)

500

400

300

200

x 5

C1s

Vacuum Air15

10

5

0

O(ads)


SnO2


∘) A dry air 119879an = 300∘C










1

2

3

4

Recovery

ResponseDry air

Wet air

qkT (eVminus1)

15 17 19 21 23 25 27 29

100

101

102

103

Resp

onse

and

reco

very

tim

es (s

ec)


+ ozone (1ppm)Air






2and sim2 ppm of CH

4






2uarr + eminus (14)


3+OH120575minus (15)




2appeared due







119878


O119878



1

2

6

2

4

0


350 400 450 500 550300Wavelength (nm)

2

4

6

8

EL p

ower

at40

mA

(mW

)

Sens

or re

spon

seR

ozon

eR

air



3 Adapted








2- and In

2O3-based





2 For


50 200150 3000 100 350250

Time (min)

10minus5

10minus4

10minus3

10minus2

10minus1

100

101

102

Spec

con

duct

ivity

(Ωminus1

cmminus1)







2


ℎ] 997904rArr e119878

minus+ h119878

+ (17)

h119878

++O2119878

minus997904rArr O

2119878997904rArr O

2uarr (18)



119877dark119877UV

sim exp(119902ΔB119896119879

) (19)



Table5Ty

picalp

aram

eterso

fRTozon

esensorsop

erated

usingUVph

otoreductio

neffect

Metaloxide

Techno

logyfilm

parameters

UVsourcecon

ditio

nsof

photoreductio

nMax119878

Con

ditio

nsof

measurements

Respon

setim

eRe

covery

time

References

In2O3

Thin


tsim8ndash25

nmUVHglamp(254

nm)vacuum

sim105ndash106

RTsim

30ndash9

0ppb

na

na

[170171173174]

Thickfilm

(mesop

orou

s)dmdashnatsim30

nmUVLE

Dair(100∘C)

sim130ndash

350

PretreatmentRT

02ndash12

ppmdry

Minutes

25ndash53m

in[119175]

Thin

filmdmdashnatmdash

na

UVLE

D(375

nm)air(01P

a)sim4

RT25pp

msim10min

na

[169]

Thin

filmdsim20

nmtsim7n

mUVLE

D(375

nm)na

sim105

RT104p

pmMinutes

Minutes

[176]

Thin

filmdmdashnatsim7n

mUVLE

D(375

nm)air

sim5ndash12

RT03ndash1

ppm

Minutes

Minutes

[121163177]

SnO2

Thin

filmdsim450n

mtmdashna

UVLE

D(370

nm)air

13ndash14

RT10p

pm60

Minutes

Tens

ofminutes

[178]

Thin

filmdsim6ndash

9nmtmdashna

UVLE

D(385

nm)air

sim11

RT100

ppbdry

Tens

ofminutes

Tens

ofminutes

[179]


na

UVlight

(366

nm)air

26RT

25pp

msim50

min

sim4-5m

in[180]

PtSnO2


na

UVlight

(366

nm)air

885

RT25pp

msim6m

insim15

min

[180]

ZnO

Thin

filmdsim150ndash

1000

nmtsim5ndash11nm

UVHglamp(254

nm)vacuum

sim103ndash108

RTn

aTens

ofminutes

Minutes

[38181]

Thin


nmUVlamp(366

nm)air

UVlampair(580∘C)

sim12

sim103

RT25pp

m10min

1min

Minutes

5s(580∘C)

[182]


nmUVLE

D(400

nm)air

sim2ndash25

RT70p

pb50

5ndash10min

Minutes

[183]

ZnO-SnO2


UVlight

(366

nm)air

39RT

25pp

msim2m

insim7m

in[180]

InGaZ

nOTh

infilmdsim65

nmtmdashna

UVLE

D(370

nm)air

14RT

2pp

m10min

gt30

min

[184]

TiO2


UVlight

(366

nm)air

64RT

25pp

msim1m

insim2m

in[180]


LED(460

nm)air

2RT

25pp

msim15

min

sim1m

in[185]

TiO2-SnO2


UVlight

(366

nm)air

327

RT25pp

msim3m

insim15s

[180]

Pt(TiO2-SnO2)(14)


UVlight

(366

nm)air

103

RT25pp

msim3m

insim1m

in[180]

WO3


mLE

D(460

nm)air

64RT

25pp

msim1m

insim1m

in[185]

TiO2-W

O3


mLE

D(460

nm)air

1400

RT25pp

msim3m

insim8m

in[185]

Pt(TiO2-W

O3)(14)


mLE

D(460

nm)air

2700

RT25pp

m15min

15min

[185]

dfilm

thickn

esstgrainsiz

eSsensor

respon

se(119877

ozon

e119877air)con

ditio

nsof

measurements

temperature

ofop

eration

gasc

oncentratio

nandairh

umidity








2O3can catalyt-


2surface is deacti-




2O3and










2O3minus119909



001 01 1 10

100

10

100

(a)

UV

16012080400Time (min)

Resp

onse

tim

e (m

in)

(b)

15ppb

200ppb

25ppm

22ppm

92ppm

In2O3


O3

50

40

30

20

10

0

Resis

tanc

e (kO

hm)



3-concentrations





2O3-





1

2


0 50 100 150 200 250 300 350


10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Con

duct

ivity

(Ωminus1

cmminus1)



0 50 100 150 200


103

104

105

106

107

Sens

or re

spon

seR

ozon

eR

air






2


24ppm ozone LED on

24ppm ozoneLED off

15 30 45 600

Time (min)

Resp

onse

[RR

0]

In2O3

24ppm ozoneLED off

50 100 1500

150

0

02

04

06

(k)

0

04 k

08 k

12 k

16 k









2O3









2films






2O3-





2O3and SnO








3+ (OO-H

+) + 2eminus


2uarr +H

2O uarr

(21)


2or HO



2at





2and In

2O3sensors


2sur-









Different OH-groups

100 200 300 400 5000Temperature (∘C)


Sens

or re

spon

se

100 200 300 400 500

Sens

or re

spon

se

300 400 500 600

Sens

itivi

ty to

air h

umid

ityTh

e rat

io S

(wet

)S(

dry)

SnO2

100

101

102

100

101

102

103

100

101

102

103

104




RH sim 45

RH sim 1-2

RH sim 45

RH sim 1-2





119887




2films deposited



Grain

Grain




diffusion

(a) (b)




119878sim 119881119878 where 119899





119878sim Δ119873

119878





119887sim Δ(MeO)

119904




Elsevier





layerBulk region

Interface region

Grains














119878



119901) in


119901sim 998779(MeO)

119887)


Δ119866 (119905)

= 119870119889(119905) Δ119866

1(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905)

(22)








119889(119905)



Δ119866 (119905) = 119870119889(119905) Δ119866 (23)





Δ119866 (119905) = Δ1198661(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905) (24)




2-





3(119905) could be


Δ1198663(119905) = 119870

119886119889(119905) Δ119866

119888(119905) (25)

1-2 RH

Resp

onse

tim

e (se

c)

100

101

102

103

In2O3

20 40 60 10010Grain size (nm)

120591 sim t2

















0 100 200 300 400Thickness (nm)

Activ

atio

n en

ergy

(eV

)

20

16

12

08

04

0

OzoneResponse

Recovery

Dry

Dry

Wet

Wet

1

2

3

E sim 15 eV

E sim 06 eV



119878


2O3and SnO

2surfaces





2O3 one













2O3surface





2O) in chemisorbed







2O3









1

2

34

5

6035 eV

055 eV

13

eV

100

101

102

103

Tim

e con

stant

s (se

c)


16 qkT (eVminus1)

18 20 22

Esim115

eV

(a)

1

2

34

5

Response

Recovery (wet air)

Dry airWet air

Wet02

8 eV

In2O3

18 20 22 24 26 28 30

400 300 200 150

qkT (eVminus1)

100

101

102

103

Tim

e con

stant

s (se

c)


E sim 033 eV

(b)











2O3sensor response











2based






0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV









Recovery time

Response time


0

100

200

300

Tim

e con

stant

(sec

)


2O3


100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2







8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation













1ndash3020ndash200














5ndash10














3 SnO

2 ZnO MoO


2 ITO NiO SmFeO

3

Ga2O3In2O3


2 In2O3ZnOSnO

2 SnO

2-In2O3


2O3 ZnO PtTiO

2-SnO2


2O3 SnO

2SWNTs



2



2and In

2O3thin films


2and In

2O3are wide-band-


2O3- and SnO

2-based ozone




2 SO2


2O3and SnO

2also


In2O3and SnO





O2(g) larrrarr O

2(ad)


2

minus(ad)





O 999445999468 VO2++

1

2

O2+ 2eminus (2)

Sn 999445999468 Sni4++ 4eminus (3)


Table3Th

ebestp

aram

eterso

fcon

ductom

etric

heated

ozon

esensorsdesig

nedon

theb

aseo

fmetaloxides

Techno

logicalrou

teparam

eterso

fsensin

glayer

Maxsensorrespo

nse

Con

ditio

nsof

measurements

Respon

setim

eRe

covery

times

References

In2O3

Thickfilmdsim100n

mtsim12nm

sim3sdot102

85∘C

250p

pbdry

25ndash4

5sna

[35]


msim15

sdot103

300∘C

100p

pbdry

sim1m

insim10min

[5051]


msim(4ndash6

)sdot103

350∘C

76pp

bna

na

[33]

Thickfilmdsim20

120583mtsim20

nm120

270∘C

1ppm

dry

na

na

[52]

Thin

filmsdsim

30ndash50n

mtsim10ndash15n

m103ndash104

200ndash

300∘C

1ppm

lt2s

(280∘C)

sim20

s(280∘C)

[4344

5354]

Thin

filmsdmdash

natmdash

na

sim102

400∘C

60pp

b100m

in(250∘C)

60ndash80m

in(250∘C)

[46]

Thin

filmsdmdash

natmdash

na

sim3sdot102

370∘C

230p

pbna

na

[55]

SnO2

Thickfilmdsim100n

mtsim15nm

sim(3-4)sdot

102

120∘C

250p

pbdry

40ndash6

0sTens

ofminutes

[35]

Thin

filmsdsim

30ndash50n

mtsim10ndash15n

m103ndash104

200ndash

300∘C

1ppm

lt2s

(280∘C)

sim15min

(280∘C)

[455657]

Thin

filmsdsim

260n

mtmdashna

sim102

350∘C

135p

pbSeveralm

inutes

Severalm

inutes

[5859]

Thin

filmsdsim

300n

mtmdashna

sim10

350∘C

60pp

bna

na

[6061]

Thin

filmsdsim

20ndash30n

mtsim6ndash

8nm

sim103

320∘C

1ppm

lt2-3s

sim15min

[47]

Thin

filmsdsim

40ndash50n

m119905lt6ndash8

nmsim105

150∘C

1ppm

3-4s

(200∘C)

sim17min

(200∘C)

[62]

WO3


sim60

0180∘C

1ppm

sim15s

sim2m

in[35]


na

sim35

400∘C

80pp

bna

na

[63]

Thin

filmsdsim

100n

mtmdashna

sim6sdot102ndash7

sdot103

120∘C

90pp

bsim12s

1ndash3m

in[64]

Thin

filmsdsim

35ndash50n

mtsim20ndash100

nm5ndash300

250∘C

08p

pm05ndash2m

in2-3m

in[65ndash69]

Thin

filmsdsim

300n

mtmdashna

sim20

300∘C

200p

pbMinutes

Minutes

[63]

Thin

filmsdmdash

natsim20

nm15

sdot103

300∘C

500p

pbna

na

[70]

ZnO


msim8

250∘C

01p

pm14s

9s[71]

Thickfilmdsim275n

m119905mdashna

sim10ndash30

200∘C

300p

pbsim10s

sim2m

in[72]

MoO3-TiO2


17370∘C

100p

pbsim20

sna

[73]

Fe2O3

Thin

films119889sim500n

m119905mdashna

sim20

200∘C

05p

pm50

na

na

[74]

SmFeO3


sim102

285∘C

04p

pmsim1m

insim10min

[75]

dfilm

thickn

esstgrainsiz

esensor

respon

se(119877

ozon

e119877air)con

ditio

nsof

measurements

temperature

ofop

eration

gasc

oncentratio

nandhu

midity


Other oxides

WO3

ZnO SnO2

In2O3



Ominus O2minus

O2

0 200 300 400 500

Temperature (∘C)

O2minus

100




O2 + erarr2Ominus




2- and









2O3- and SnO

2-based



2O3or SnO




2







3was observed at


2- and



1minus119909Fe119909O3 120572-Ag

2WO4 and Fe

2O3 have maximum


2-


2)




In2O3

Ozone

CO

40nm

70nm60nm

200nm

200100 400 500300

Temperature (∘C)

100

101

102

103

Sens

or re

spon

se

RH sim 45


[43 44 90]





2and In

2O3








SnO2

(111) (200) (020) (112) (120) (110) (101) (011) (011) (101) (010) (001) (100)(110) (010) (010) (110) (100) (221) (221) (221) [99 112 113]






2O3and SnO

2thin films






(110)

(100)

(001)

(101)

SnO2

(a)

(111)

(100)

(110)

In2O3

(b)


2O3


Resp

onse

and

reco

very

tim

e (se

c)

Response

Recovery


103

102

101

100100 200 300 400

In2O3

SnO2

SnO2



2O3- and SnO





2O3



119878 sim (

120591rec120591res

)

119898

(4)



119878 =

119877

1198770

= 119870119862119883 (5)




11

8

3

2

6

4

9

12

107

13

1

5


Ozone

100

101

102

103

104

105

Sens

or re

spon

se





2O3







2O3(sol-









119878gt 0)



be expressed as

119878 =

119866

1198660

sim exp (119902Δ119881119878

119896119879

) lt 1 (6)


O

O

+

minus

O O O

O

+

minus







O3(g) 997888rarr O


3

minus(s) (7)

O3(g) 997888rarr O




3











3was




3




3


2O3



Sn Sn Sn

O

O O

O + O2O3



[136]



2O) A



O3+ VO∙∙+ 2e 999445999468 OO +O

2uarr (9)


2is valid for


2lattice


2

TiO2 and SrTiO










2O3lattice at



2-



2surface is shown


2surface









2uarr + eminus (10)


OH

R(air)

Con

cent

ratio

n (a

u)

Ozone

S

O2

H2O

O

100

101

102

103

Sens

or re

spon

se


105

107

109

Resis

tanc

e (O

hm)



2films



2lattice atoms has


2surface is




2and In

2O3[155 156] Inter-


2



O1s

Sn3d

(a)

(b)


Inte

nsity

of X

PS (O

1s C

1s a

nd S

n3d)

pea

ks (a

u)

500

400

300

200

x 5

C1s

Vacuum Air15

10

5

0

O(ads)


SnO2


∘) A dry air 119879an = 300∘C










1

2

3

4

Recovery

ResponseDry air

Wet air

qkT (eVminus1)

15 17 19 21 23 25 27 29

100

101

102

103

Resp

onse

and

reco

very

tim

es (s

ec)


+ ozone (1ppm)Air






2and sim2 ppm of CH

4






2uarr + eminus (14)


3+OH120575minus (15)




2appeared due







119878


O119878



1

2

6

2

4

0


350 400 450 500 550300Wavelength (nm)

2

4

6

8

EL p

ower

at40

mA

(mW

)

Sens

or re

spon

seR

ozon

eR

air



3 Adapted








2- and In

2O3-based





2 For


50 200150 3000 100 350250

Time (min)

10minus5

10minus4

10minus3

10minus2

10minus1

100

101

102

Spec

con

duct

ivity

(Ωminus1

cmminus1)







2


ℎ] 997904rArr e119878

minus+ h119878

+ (17)

h119878

++O2119878

minus997904rArr O

2119878997904rArr O

2uarr (18)



119877dark119877UV

sim exp(119902ΔB119896119879

) (19)



Table5Ty

picalp

aram

eterso

fRTozon

esensorsop

erated

usingUVph

otoreductio

neffect

Metaloxide

Techno

logyfilm

parameters

UVsourcecon

ditio

nsof

photoreductio

nMax119878

Con

ditio

nsof

measurements

Respon

setim

eRe

covery

time

References

In2O3

Thin


tsim8ndash25

nmUVHglamp(254

nm)vacuum

sim105ndash106

RTsim

30ndash9

0ppb

na

na

[170171173174]

Thickfilm

(mesop

orou

s)dmdashnatsim30

nmUVLE

Dair(100∘C)

sim130ndash

350

PretreatmentRT

02ndash12

ppmdry

Minutes

25ndash53m

in[119175]

Thin

filmdmdashnatmdash

na

UVLE

D(375

nm)air(01P

a)sim4

RT25pp

msim10min

na

[169]

Thin

filmdsim20

nmtsim7n

mUVLE

D(375

nm)na

sim105

RT104p

pmMinutes

Minutes

[176]

Thin

filmdmdashnatsim7n

mUVLE

D(375

nm)air

sim5ndash12

RT03ndash1

ppm

Minutes

Minutes

[121163177]

SnO2

Thin

filmdsim450n

mtmdashna

UVLE

D(370

nm)air

13ndash14

RT10p

pm60

Minutes

Tens

ofminutes

[178]

Thin

filmdsim6ndash

9nmtmdashna

UVLE

D(385

nm)air

sim11

RT100

ppbdry

Tens

ofminutes

Tens

ofminutes

[179]


na

UVlight

(366

nm)air

26RT

25pp

msim50

min

sim4-5m

in[180]

PtSnO2


na

UVlight

(366

nm)air

885

RT25pp

msim6m

insim15

min

[180]

ZnO

Thin

filmdsim150ndash

1000

nmtsim5ndash11nm

UVHglamp(254

nm)vacuum

sim103ndash108

RTn

aTens

ofminutes

Minutes

[38181]

Thin


nmUVlamp(366

nm)air

UVlampair(580∘C)

sim12

sim103

RT25pp

m10min

1min

Minutes

5s(580∘C)

[182]


nmUVLE

D(400

nm)air

sim2ndash25

RT70p

pb50

5ndash10min

Minutes

[183]

ZnO-SnO2


UVlight

(366

nm)air

39RT

25pp

msim2m

insim7m

in[180]

InGaZ

nOTh

infilmdsim65

nmtmdashna

UVLE

D(370

nm)air

14RT

2pp

m10min

gt30

min

[184]

TiO2


UVlight

(366

nm)air

64RT

25pp

msim1m

insim2m

in[180]


LED(460

nm)air

2RT

25pp

msim15

min

sim1m

in[185]

TiO2-SnO2


UVlight

(366

nm)air

327

RT25pp

msim3m

insim15s

[180]

Pt(TiO2-SnO2)(14)


UVlight

(366

nm)air

103

RT25pp

msim3m

insim1m

in[180]

WO3


mLE

D(460

nm)air

64RT

25pp

msim1m

insim1m

in[185]

TiO2-W

O3


mLE

D(460

nm)air

1400

RT25pp

msim3m

insim8m

in[185]

Pt(TiO2-W

O3)(14)


mLE

D(460

nm)air

2700

RT25pp

m15min

15min

[185]

dfilm

thickn

esstgrainsiz

eSsensor

respon

se(119877

ozon

e119877air)con

ditio

nsof

measurements

temperature

ofop

eration

gasc

oncentratio

nandairh

umidity








2O3can catalyt-


2surface is deacti-




2O3and










2O3minus119909



001 01 1 10

100

10

100

(a)

UV

16012080400Time (min)

Resp

onse

tim

e (m

in)

(b)

15ppb

200ppb

25ppm

22ppm

92ppm

In2O3


O3

50

40

30

20

10

0

Resis

tanc

e (kO

hm)



3-concentrations





2O3-





1

2


0 50 100 150 200 250 300 350


10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Con

duct

ivity

(Ωminus1

cmminus1)



0 50 100 150 200


103

104

105

106

107

Sens

or re

spon

seR

ozon

eR

air






2


24ppm ozone LED on

24ppm ozoneLED off

15 30 45 600

Time (min)

Resp

onse

[RR

0]

In2O3

24ppm ozoneLED off

50 100 1500

150

0

02

04

06

(k)

0

04 k

08 k

12 k

16 k









2O3









2films






2O3-





2O3and SnO








3+ (OO-H

+) + 2eminus


2uarr +H

2O uarr

(21)


2or HO



2at





2and In

2O3sensors


2sur-









Different OH-groups

100 200 300 400 5000Temperature (∘C)


Sens

or re

spon

se

100 200 300 400 500

Sens

or re

spon

se

300 400 500 600

Sens

itivi

ty to

air h

umid

ityTh

e rat

io S

(wet

)S(

dry)

SnO2

100

101

102

100

101

102

103

100

101

102

103

104




RH sim 45

RH sim 1-2

RH sim 45

RH sim 1-2





119887




2films deposited



Grain

Grain




diffusion

(a) (b)




119878sim 119881119878 where 119899





119878sim Δ119873

119878





119887sim Δ(MeO)

119904




Elsevier





layerBulk region

Interface region

Grains














119878



119901) in


119901sim 998779(MeO)

119887)


Δ119866 (119905)

= 119870119889(119905) Δ119866

1(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905)

(22)








119889(119905)



Δ119866 (119905) = 119870119889(119905) Δ119866 (23)





Δ119866 (119905) = Δ1198661(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905) (24)




2-





3(119905) could be


Δ1198663(119905) = 119870

119886119889(119905) Δ119866

119888(119905) (25)

1-2 RH

Resp

onse

tim

e (se

c)

100

101

102

103

In2O3

20 40 60 10010Grain size (nm)

120591 sim t2

















0 100 200 300 400Thickness (nm)

Activ

atio

n en

ergy

(eV

)

20

16

12

08

04

0

OzoneResponse

Recovery

Dry

Dry

Wet

Wet

1

2

3

E sim 15 eV

E sim 06 eV



119878


2O3and SnO

2surfaces





2O3 one













2O3surface





2O) in chemisorbed







2O3









1

2

34

5

6035 eV

055 eV

13

eV

100

101

102

103

Tim

e con

stant

s (se

c)


16 qkT (eVminus1)

18 20 22

Esim115

eV

(a)

1

2

34

5

Response

Recovery (wet air)

Dry airWet air

Wet02

8 eV

In2O3

18 20 22 24 26 28 30

400 300 200 150

qkT (eVminus1)

100

101

102

103

Tim

e con

stant

s (se

c)


E sim 033 eV

(b)











2O3sensor response











2based






0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV









Recovery time

Response time


0

100

200

300

Tim

e con

stant

(sec

)


2O3


100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2







8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation














3 SnO

2 ZnO MoO


2 ITO NiO SmFeO

3

Ga2O3In2O3


2 In2O3ZnOSnO

2 SnO

2-In2O3


2O3 ZnO PtTiO

2-SnO2


2O3 SnO

2SWNTs



2



2and In

2O3thin films


2and In

2O3are wide-band-


2O3- and SnO

2-based ozone




2 SO2


2O3and SnO

2also


In2O3and SnO





O2(g) larrrarr O

2(ad)


2

minus(ad)





O 999445999468 VO2++

1

2

O2+ 2eminus (2)

Sn 999445999468 Sni4++ 4eminus (3)


Table3Th

ebestp

aram

eterso

fcon

ductom

etric

heated

ozon

esensorsdesig

nedon

theb

aseo

fmetaloxides

Techno

logicalrou

teparam

eterso

fsensin

glayer

Maxsensorrespo

nse

Con

ditio

nsof

measurements

Respon

setim

eRe

covery

times

References

In2O3

Thickfilmdsim100n

mtsim12nm

sim3sdot102

85∘C

250p

pbdry

25ndash4

5sna

[35]


msim15

sdot103

300∘C

100p

pbdry

sim1m

insim10min

[5051]


msim(4ndash6

)sdot103

350∘C

76pp

bna

na

[33]

Thickfilmdsim20

120583mtsim20

nm120

270∘C

1ppm

dry

na

na

[52]

Thin

filmsdsim

30ndash50n

mtsim10ndash15n

m103ndash104

200ndash

300∘C

1ppm

lt2s

(280∘C)

sim20

s(280∘C)

[4344

5354]

Thin

filmsdmdash

natmdash

na

sim102

400∘C

60pp

b100m

in(250∘C)

60ndash80m

in(250∘C)

[46]

Thin

filmsdmdash

natmdash

na

sim3sdot102

370∘C

230p

pbna

na

[55]

SnO2

Thickfilmdsim100n

mtsim15nm

sim(3-4)sdot

102

120∘C

250p

pbdry

40ndash6

0sTens

ofminutes

[35]

Thin

filmsdsim

30ndash50n

mtsim10ndash15n

m103ndash104

200ndash

300∘C

1ppm

lt2s

(280∘C)

sim15min

(280∘C)

[455657]

Thin

filmsdsim

260n

mtmdashna

sim102

350∘C

135p

pbSeveralm

inutes

Severalm

inutes

[5859]

Thin

filmsdsim

300n

mtmdashna

sim10

350∘C

60pp

bna

na

[6061]

Thin

filmsdsim

20ndash30n

mtsim6ndash

8nm

sim103

320∘C

1ppm

lt2-3s

sim15min

[47]

Thin

filmsdsim

40ndash50n

m119905lt6ndash8

nmsim105

150∘C

1ppm

3-4s

(200∘C)

sim17min

(200∘C)

[62]

WO3


sim60

0180∘C

1ppm

sim15s

sim2m

in[35]


na

sim35

400∘C

80pp

bna

na

[63]

Thin

filmsdsim

100n

mtmdashna

sim6sdot102ndash7

sdot103

120∘C

90pp

bsim12s

1ndash3m

in[64]

Thin

filmsdsim

35ndash50n

mtsim20ndash100

nm5ndash300

250∘C

08p

pm05ndash2m

in2-3m

in[65ndash69]

Thin

filmsdsim

300n

mtmdashna

sim20

300∘C

200p

pbMinutes

Minutes

[63]

Thin

filmsdmdash

natsim20

nm15

sdot103

300∘C

500p

pbna

na

[70]

ZnO


msim8

250∘C

01p

pm14s

9s[71]

Thickfilmdsim275n

m119905mdashna

sim10ndash30

200∘C

300p

pbsim10s

sim2m

in[72]

MoO3-TiO2


17370∘C

100p

pbsim20

sna

[73]

Fe2O3

Thin

films119889sim500n

m119905mdashna

sim20

200∘C

05p

pm50

na

na

[74]

SmFeO3


sim102

285∘C

04p

pmsim1m

insim10min

[75]

dfilm

thickn

esstgrainsiz

esensor

respon

se(119877

ozon

e119877air)con

ditio

nsof

measurements

temperature

ofop

eration

gasc

oncentratio

nandhu

midity


Other oxides

WO3

ZnO SnO2

In2O3



Ominus O2minus

O2

0 200 300 400 500

Temperature (∘C)

O2minus

100




O2 + erarr2Ominus




2- and









2O3- and SnO

2-based



2O3or SnO




2







3was observed at


2- and



1minus119909Fe119909O3 120572-Ag

2WO4 and Fe

2O3 have maximum


2-


2)




In2O3

Ozone

CO

40nm

70nm60nm

200nm

200100 400 500300

Temperature (∘C)

100

101

102

103

Sens

or re

spon

se

RH sim 45


[43 44 90]





2and In

2O3








SnO2

(111) (200) (020) (112) (120) (110) (101) (011) (011) (101) (010) (001) (100)(110) (010) (010) (110) (100) (221) (221) (221) [99 112 113]






2O3and SnO

2thin films






(110)

(100)

(001)

(101)

SnO2

(a)

(111)

(100)

(110)

In2O3

(b)


2O3


Resp

onse

and

reco

very

tim

e (se

c)

Response

Recovery


103

102

101

100100 200 300 400

In2O3

SnO2

SnO2



2O3- and SnO





2O3



119878 sim (

120591rec120591res

)

119898

(4)



119878 =

119877

1198770

= 119870119862119883 (5)




11

8

3

2

6

4

9

12

107

13

1

5


Ozone

100

101

102

103

104

105

Sens

or re

spon

se





2O3







2O3(sol-









119878gt 0)



be expressed as

119878 =

119866

1198660

sim exp (119902Δ119881119878

119896119879

) lt 1 (6)


O

O

+

minus

O O O

O

+

minus







O3(g) 997888rarr O


3

minus(s) (7)

O3(g) 997888rarr O




3











3was




3




3


2O3



Sn Sn Sn

O

O O

O + O2O3



[136]



2O) A



O3+ VO∙∙+ 2e 999445999468 OO +O

2uarr (9)


2is valid for


2lattice


2

TiO2 and SrTiO










2O3lattice at



2-



2surface is shown


2surface









2uarr + eminus (10)


OH

R(air)

Con

cent

ratio

n (a

u)

Ozone

S

O2

H2O

O

100

101

102

103

Sens

or re

spon

se


105

107

109

Resis

tanc

e (O

hm)



2films



2lattice atoms has


2surface is




2and In

2O3[155 156] Inter-


2



O1s

Sn3d

(a)

(b)


Inte

nsity

of X

PS (O

1s C

1s a

nd S

n3d)

pea

ks (a

u)

500

400

300

200

x 5

C1s

Vacuum Air15

10

5

0

O(ads)


SnO2


∘) A dry air 119879an = 300∘C










1

2

3

4

Recovery

ResponseDry air

Wet air

qkT (eVminus1)

15 17 19 21 23 25 27 29

100

101

102

103

Resp

onse

and

reco

very

tim

es (s

ec)


+ ozone (1ppm)Air






2and sim2 ppm of CH

4






2uarr + eminus (14)


3+OH120575minus (15)




2appeared due







119878


O119878



1

2

6

2

4

0


350 400 450 500 550300Wavelength (nm)

2

4

6

8

EL p

ower

at40

mA

(mW

)

Sens

or re

spon

seR

ozon

eR

air



3 Adapted








2- and In

2O3-based





2 For


50 200150 3000 100 350250

Time (min)

10minus5

10minus4

10minus3

10minus2

10minus1

100

101

102

Spec

con

duct

ivity

(Ωminus1

cmminus1)







2


ℎ] 997904rArr e119878

minus+ h119878

+ (17)

h119878

++O2119878

minus997904rArr O

2119878997904rArr O

2uarr (18)



119877dark119877UV

sim exp(119902ΔB119896119879

) (19)



Table5Ty

picalp

aram

eterso

fRTozon

esensorsop

erated

usingUVph

otoreductio

neffect

Metaloxide

Techno

logyfilm

parameters

UVsourcecon

ditio

nsof

photoreductio

nMax119878

Con

ditio

nsof

measurements

Respon

setim

eRe

covery

time

References

In2O3

Thin


tsim8ndash25

nmUVHglamp(254

nm)vacuum

sim105ndash106

RTsim

30ndash9

0ppb

na

na

[170171173174]

Thickfilm

(mesop

orou

s)dmdashnatsim30

nmUVLE

Dair(100∘C)

sim130ndash

350

PretreatmentRT

02ndash12

ppmdry

Minutes

25ndash53m

in[119175]

Thin

filmdmdashnatmdash

na

UVLE

D(375

nm)air(01P

a)sim4

RT25pp

msim10min

na

[169]

Thin

filmdsim20

nmtsim7n

mUVLE

D(375

nm)na

sim105

RT104p

pmMinutes

Minutes

[176]

Thin

filmdmdashnatsim7n

mUVLE

D(375

nm)air

sim5ndash12

RT03ndash1

ppm

Minutes

Minutes

[121163177]

SnO2

Thin

filmdsim450n

mtmdashna

UVLE

D(370

nm)air

13ndash14

RT10p

pm60

Minutes

Tens

ofminutes

[178]

Thin

filmdsim6ndash

9nmtmdashna

UVLE

D(385

nm)air

sim11

RT100

ppbdry

Tens

ofminutes

Tens

ofminutes

[179]


na

UVlight

(366

nm)air

26RT

25pp

msim50

min

sim4-5m

in[180]

PtSnO2


na

UVlight

(366

nm)air

885

RT25pp

msim6m

insim15

min

[180]

ZnO

Thin

filmdsim150ndash

1000

nmtsim5ndash11nm

UVHglamp(254

nm)vacuum

sim103ndash108

RTn

aTens

ofminutes

Minutes

[38181]

Thin


nmUVlamp(366

nm)air

UVlampair(580∘C)

sim12

sim103

RT25pp

m10min

1min

Minutes

5s(580∘C)

[182]


nmUVLE

D(400

nm)air

sim2ndash25

RT70p

pb50

5ndash10min

Minutes

[183]

ZnO-SnO2


UVlight

(366

nm)air

39RT

25pp

msim2m

insim7m

in[180]

InGaZ

nOTh

infilmdsim65

nmtmdashna

UVLE

D(370

nm)air

14RT

2pp

m10min

gt30

min

[184]

TiO2


UVlight

(366

nm)air

64RT

25pp

msim1m

insim2m

in[180]


LED(460

nm)air

2RT

25pp

msim15

min

sim1m

in[185]

TiO2-SnO2


UVlight

(366

nm)air

327

RT25pp

msim3m

insim15s

[180]

Pt(TiO2-SnO2)(14)


UVlight

(366

nm)air

103

RT25pp

msim3m

insim1m

in[180]

WO3


mLE

D(460

nm)air

64RT

25pp

msim1m

insim1m

in[185]

TiO2-W

O3


mLE

D(460

nm)air

1400

RT25pp

msim3m

insim8m

in[185]

Pt(TiO2-W

O3)(14)


mLE

D(460

nm)air

2700

RT25pp

m15min

15min

[185]

dfilm

thickn

esstgrainsiz

eSsensor

respon

se(119877

ozon

e119877air)con

ditio

nsof

measurements

temperature

ofop

eration

gasc

oncentratio

nandairh

umidity








2O3can catalyt-


2surface is deacti-




2O3and










2O3minus119909



001 01 1 10

100

10

100

(a)

UV

16012080400Time (min)

Resp

onse

tim

e (m

in)

(b)

15ppb

200ppb

25ppm

22ppm

92ppm

In2O3


O3

50

40

30

20

10

0

Resis

tanc

e (kO

hm)



3-concentrations





2O3-





1

2


0 50 100 150 200 250 300 350


10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Con

duct

ivity

(Ωminus1

cmminus1)



0 50 100 150 200


103

104

105

106

107

Sens

or re

spon

seR

ozon

eR

air






2


24ppm ozone LED on

24ppm ozoneLED off

15 30 45 600

Time (min)

Resp

onse

[RR

0]

In2O3

24ppm ozoneLED off

50 100 1500

150

0

02

04

06

(k)

0

04 k

08 k

12 k

16 k









2O3









2films






2O3-





2O3and SnO








3+ (OO-H

+) + 2eminus


2uarr +H

2O uarr

(21)


2or HO



2at





2and In

2O3sensors


2sur-









Different OH-groups

100 200 300 400 5000Temperature (∘C)


Sens

or re

spon

se

100 200 300 400 500

Sens

or re

spon

se

300 400 500 600

Sens

itivi

ty to

air h

umid

ityTh

e rat

io S

(wet

)S(

dry)

SnO2

100

101

102

100

101

102

103

100

101

102

103

104




RH sim 45

RH sim 1-2

RH sim 45

RH sim 1-2





119887




2films deposited



Grain

Grain




diffusion

(a) (b)




119878sim 119881119878 where 119899





119878sim Δ119873

119878





119887sim Δ(MeO)

119904




Elsevier





layerBulk region

Interface region

Grains














119878



119901) in


119901sim 998779(MeO)

119887)


Δ119866 (119905)

= 119870119889(119905) Δ119866

1(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905)

(22)








119889(119905)



Δ119866 (119905) = 119870119889(119905) Δ119866 (23)





Δ119866 (119905) = Δ1198661(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905) (24)




2-





3(119905) could be


Δ1198663(119905) = 119870

119886119889(119905) Δ119866

119888(119905) (25)

1-2 RH

Resp

onse

tim

e (se

c)

100

101

102

103

In2O3

20 40 60 10010Grain size (nm)

120591 sim t2

















0 100 200 300 400Thickness (nm)

Activ

atio

n en

ergy

(eV

)

20

16

12

08

04

0

OzoneResponse

Recovery

Dry

Dry

Wet

Wet

1

2

3

E sim 15 eV

E sim 06 eV



119878


2O3and SnO

2surfaces





2O3 one













2O3surface





2O) in chemisorbed







2O3









1

2

34

5

6035 eV

055 eV

13

eV

100

101

102

103

Tim

e con

stant

s (se

c)


16 qkT (eVminus1)

18 20 22

Esim115

eV

(a)

1

2

34

5

Response

Recovery (wet air)

Dry airWet air

Wet02

8 eV

In2O3

18 20 22 24 26 28 30

400 300 200 150

qkT (eVminus1)

100

101

102

103

Tim

e con

stant

s (se

c)


E sim 033 eV

(b)











2O3sensor response











2based






0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV









Recovery time

Response time


0

100

200

300

Tim

e con

stant

(sec

)


2O3


100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2







8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










Table3Th

ebestp

aram

eterso

fcon

ductom

etric

heated

ozon

esensorsdesig

nedon

theb

aseo

fmetaloxides

Techno

logicalrou

teparam

eterso

fsensin

glayer

Maxsensorrespo

nse

Con

ditio

nsof

measurements

Respon

setim

eRe

covery

times

References

In2O3

Thickfilmdsim100n

mtsim12nm

sim3sdot102

85∘C

250p

pbdry

25ndash4

5sna

[35]


msim15

sdot103

300∘C

100p

pbdry

sim1m

insim10min

[5051]


msim(4ndash6

)sdot103

350∘C

76pp

bna

na

[33]

Thickfilmdsim20

120583mtsim20

nm120

270∘C

1ppm

dry

na

na

[52]

Thin

filmsdsim

30ndash50n

mtsim10ndash15n

m103ndash104

200ndash

300∘C

1ppm

lt2s

(280∘C)

sim20

s(280∘C)

[4344

5354]

Thin

filmsdmdash

natmdash

na

sim102

400∘C

60pp

b100m

in(250∘C)

60ndash80m

in(250∘C)

[46]

Thin

filmsdmdash

natmdash

na

sim3sdot102

370∘C

230p

pbna

na

[55]

SnO2

Thickfilmdsim100n

mtsim15nm

sim(3-4)sdot

102

120∘C

250p

pbdry

40ndash6

0sTens

ofminutes

[35]

Thin

filmsdsim

30ndash50n

mtsim10ndash15n

m103ndash104

200ndash

300∘C

1ppm

lt2s

(280∘C)

sim15min

(280∘C)

[455657]

Thin

filmsdsim

260n

mtmdashna

sim102

350∘C

135p

pbSeveralm

inutes

Severalm

inutes

[5859]

Thin

filmsdsim

300n

mtmdashna

sim10

350∘C

60pp

bna

na

[6061]

Thin

filmsdsim

20ndash30n

mtsim6ndash

8nm

sim103

320∘C

1ppm

lt2-3s

sim15min

[47]

Thin

filmsdsim

40ndash50n

m119905lt6ndash8

nmsim105

150∘C

1ppm

3-4s

(200∘C)

sim17min

(200∘C)

[62]

WO3


sim60

0180∘C

1ppm

sim15s

sim2m

in[35]


na

sim35

400∘C

80pp

bna

na

[63]

Thin

filmsdsim

100n

mtmdashna

sim6sdot102ndash7

sdot103

120∘C

90pp

bsim12s

1ndash3m

in[64]

Thin

filmsdsim

35ndash50n

mtsim20ndash100

nm5ndash300

250∘C

08p

pm05ndash2m

in2-3m

in[65ndash69]

Thin

filmsdsim

300n

mtmdashna

sim20

300∘C

200p

pbMinutes

Minutes

[63]

Thin

filmsdmdash

natsim20

nm15

sdot103

300∘C

500p

pbna

na

[70]

ZnO


msim8

250∘C

01p

pm14s

9s[71]

Thickfilmdsim275n

m119905mdashna

sim10ndash30

200∘C

300p

pbsim10s

sim2m

in[72]

MoO3-TiO2


17370∘C

100p

pbsim20

sna

[73]

Fe2O3

Thin

films119889sim500n

m119905mdashna

sim20

200∘C

05p

pm50

na

na

[74]

SmFeO3


sim102

285∘C

04p

pmsim1m

insim10min

[75]

dfilm

thickn

esstgrainsiz

esensor

respon

se(119877

ozon

e119877air)con

ditio

nsof

measurements

temperature

ofop

eration

gasc

oncentratio

nandhu

midity


Other oxides

WO3

ZnO SnO2

In2O3



Ominus O2minus

O2

0 200 300 400 500

Temperature (∘C)

O2minus

100




O2 + erarr2Ominus




2- and









2O3- and SnO

2-based



2O3or SnO




2







3was observed at


2- and



1minus119909Fe119909O3 120572-Ag

2WO4 and Fe

2O3 have maximum


2-


2)




In2O3

Ozone

CO

40nm

70nm60nm

200nm

200100 400 500300

Temperature (∘C)

100

101

102

103

Sens

or re

spon

se

RH sim 45


[43 44 90]





2and In

2O3








SnO2

(111) (200) (020) (112) (120) (110) (101) (011) (011) (101) (010) (001) (100)(110) (010) (010) (110) (100) (221) (221) (221) [99 112 113]






2O3and SnO

2thin films






(110)

(100)

(001)

(101)

SnO2

(a)

(111)

(100)

(110)

In2O3

(b)


2O3


Resp

onse

and

reco

very

tim

e (se

c)

Response

Recovery


103

102

101

100100 200 300 400

In2O3

SnO2

SnO2



2O3- and SnO





2O3



119878 sim (

120591rec120591res

)

119898

(4)



119878 =

119877

1198770

= 119870119862119883 (5)




11

8

3

2

6

4

9

12

107

13

1

5


Ozone

100

101

102

103

104

105

Sens

or re

spon

se





2O3







2O3(sol-









119878gt 0)



be expressed as

119878 =

119866

1198660

sim exp (119902Δ119881119878

119896119879

) lt 1 (6)


O

O

+

minus

O O O

O

+

minus







O3(g) 997888rarr O


3

minus(s) (7)

O3(g) 997888rarr O




3











3was




3




3


2O3



Sn Sn Sn

O

O O

O + O2O3



[136]



2O) A



O3+ VO∙∙+ 2e 999445999468 OO +O

2uarr (9)


2is valid for


2lattice


2

TiO2 and SrTiO










2O3lattice at



2-



2surface is shown


2surface









2uarr + eminus (10)


OH

R(air)

Con

cent

ratio

n (a

u)

Ozone

S

O2

H2O

O

100

101

102

103

Sens

or re

spon

se


105

107

109

Resis

tanc

e (O

hm)



2films



2lattice atoms has


2surface is




2and In

2O3[155 156] Inter-


2



O1s

Sn3d

(a)

(b)


Inte

nsity

of X

PS (O

1s C

1s a

nd S

n3d)

pea

ks (a

u)

500

400

300

200

x 5

C1s

Vacuum Air15

10

5

0

O(ads)


SnO2


∘) A dry air 119879an = 300∘C










1

2

3

4

Recovery

ResponseDry air

Wet air

qkT (eVminus1)

15 17 19 21 23 25 27 29

100

101

102

103

Resp

onse

and

reco

very

tim

es (s

ec)


+ ozone (1ppm)Air






2and sim2 ppm of CH

4






2uarr + eminus (14)


3+OH120575minus (15)




2appeared due







119878


O119878



1

2

6

2

4

0


350 400 450 500 550300Wavelength (nm)

2

4

6

8

EL p

ower

at40

mA

(mW

)

Sens

or re

spon

seR

ozon

eR

air



3 Adapted








2- and In

2O3-based





2 For


50 200150 3000 100 350250

Time (min)

10minus5

10minus4

10minus3

10minus2

10minus1

100

101

102

Spec

con

duct

ivity

(Ωminus1

cmminus1)







2


ℎ] 997904rArr e119878

minus+ h119878

+ (17)

h119878

++O2119878

minus997904rArr O

2119878997904rArr O

2uarr (18)



119877dark119877UV

sim exp(119902ΔB119896119879

) (19)



Table5Ty

picalp

aram

eterso

fRTozon

esensorsop

erated

usingUVph

otoreductio

neffect

Metaloxide

Techno

logyfilm

parameters

UVsourcecon

ditio

nsof

photoreductio

nMax119878

Con

ditio

nsof

measurements

Respon

setim

eRe

covery

time

References

In2O3

Thin


tsim8ndash25

nmUVHglamp(254

nm)vacuum

sim105ndash106

RTsim

30ndash9

0ppb

na

na

[170171173174]

Thickfilm

(mesop

orou

s)dmdashnatsim30

nmUVLE

Dair(100∘C)

sim130ndash

350

PretreatmentRT

02ndash12

ppmdry

Minutes

25ndash53m

in[119175]

Thin

filmdmdashnatmdash

na

UVLE

D(375

nm)air(01P

a)sim4

RT25pp

msim10min

na

[169]

Thin

filmdsim20

nmtsim7n

mUVLE

D(375

nm)na

sim105

RT104p

pmMinutes

Minutes

[176]

Thin

filmdmdashnatsim7n

mUVLE

D(375

nm)air

sim5ndash12

RT03ndash1

ppm

Minutes

Minutes

[121163177]

SnO2

Thin

filmdsim450n

mtmdashna

UVLE

D(370

nm)air

13ndash14

RT10p

pm60

Minutes

Tens

ofminutes

[178]

Thin

filmdsim6ndash

9nmtmdashna

UVLE

D(385

nm)air

sim11

RT100

ppbdry

Tens

ofminutes

Tens

ofminutes

[179]


na

UVlight

(366

nm)air

26RT

25pp

msim50

min

sim4-5m

in[180]

PtSnO2


na

UVlight

(366

nm)air

885

RT25pp

msim6m

insim15

min

[180]

ZnO

Thin

filmdsim150ndash

1000

nmtsim5ndash11nm

UVHglamp(254

nm)vacuum

sim103ndash108

RTn

aTens

ofminutes

Minutes

[38181]

Thin


nmUVlamp(366

nm)air

UVlampair(580∘C)

sim12

sim103

RT25pp

m10min

1min

Minutes

5s(580∘C)

[182]


nmUVLE

D(400

nm)air

sim2ndash25

RT70p

pb50

5ndash10min

Minutes

[183]

ZnO-SnO2


UVlight

(366

nm)air

39RT

25pp

msim2m

insim7m

in[180]

InGaZ

nOTh

infilmdsim65

nmtmdashna

UVLE

D(370

nm)air

14RT

2pp

m10min

gt30

min

[184]

TiO2


UVlight

(366

nm)air

64RT

25pp

msim1m

insim2m

in[180]


LED(460

nm)air

2RT

25pp

msim15

min

sim1m

in[185]

TiO2-SnO2


UVlight

(366

nm)air

327

RT25pp

msim3m

insim15s

[180]

Pt(TiO2-SnO2)(14)


UVlight

(366

nm)air

103

RT25pp

msim3m

insim1m

in[180]

WO3


mLE

D(460

nm)air

64RT

25pp

msim1m

insim1m

in[185]

TiO2-W

O3


mLE

D(460

nm)air

1400

RT25pp

msim3m

insim8m

in[185]

Pt(TiO2-W

O3)(14)


mLE

D(460

nm)air

2700

RT25pp

m15min

15min

[185]

dfilm

thickn

esstgrainsiz

eSsensor

respon

se(119877

ozon

e119877air)con

ditio

nsof

measurements

temperature

ofop

eration

gasc

oncentratio

nandairh

umidity








2O3can catalyt-


2surface is deacti-




2O3and










2O3minus119909



001 01 1 10

100

10

100

(a)

UV

16012080400Time (min)

Resp

onse

tim

e (m

in)

(b)

15ppb

200ppb

25ppm

22ppm

92ppm

In2O3


O3

50

40

30

20

10

0

Resis

tanc

e (kO

hm)



3-concentrations





2O3-





1

2


0 50 100 150 200 250 300 350


10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Con

duct

ivity

(Ωminus1

cmminus1)



0 50 100 150 200


103

104

105

106

107

Sens

or re

spon

seR

ozon

eR

air






2


24ppm ozone LED on

24ppm ozoneLED off

15 30 45 600

Time (min)

Resp

onse

[RR

0]

In2O3

24ppm ozoneLED off

50 100 1500

150

0

02

04

06

(k)

0

04 k

08 k

12 k

16 k









2O3









2films






2O3-





2O3and SnO








3+ (OO-H

+) + 2eminus


2uarr +H

2O uarr

(21)


2or HO



2at





2and In

2O3sensors


2sur-









Different OH-groups

100 200 300 400 5000Temperature (∘C)


Sens

or re

spon

se

100 200 300 400 500

Sens

or re

spon

se

300 400 500 600

Sens

itivi

ty to

air h

umid

ityTh

e rat

io S

(wet

)S(

dry)

SnO2

100

101

102

100

101

102

103

100

101

102

103

104




RH sim 45

RH sim 1-2

RH sim 45

RH sim 1-2





119887




2films deposited



Grain

Grain




diffusion

(a) (b)




119878sim 119881119878 where 119899





119878sim Δ119873

119878





119887sim Δ(MeO)

119904




Elsevier





layerBulk region

Interface region

Grains














119878



119901) in


119901sim 998779(MeO)

119887)


Δ119866 (119905)

= 119870119889(119905) Δ119866

1(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905)

(22)








119889(119905)



Δ119866 (119905) = 119870119889(119905) Δ119866 (23)





Δ119866 (119905) = Δ1198661(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905) (24)




2-





3(119905) could be


Δ1198663(119905) = 119870

119886119889(119905) Δ119866

119888(119905) (25)

1-2 RH

Resp

onse

tim

e (se

c)

100

101

102

103

In2O3

20 40 60 10010Grain size (nm)

120591 sim t2

















0 100 200 300 400Thickness (nm)

Activ

atio

n en

ergy

(eV

)

20

16

12

08

04

0

OzoneResponse

Recovery

Dry

Dry

Wet

Wet

1

2

3

E sim 15 eV

E sim 06 eV



119878


2O3and SnO

2surfaces





2O3 one













2O3surface





2O) in chemisorbed







2O3









1

2

34

5

6035 eV

055 eV

13

eV

100

101

102

103

Tim

e con

stant

s (se

c)


16 qkT (eVminus1)

18 20 22

Esim115

eV

(a)

1

2

34

5

Response

Recovery (wet air)

Dry airWet air

Wet02

8 eV

In2O3

18 20 22 24 26 28 30

400 300 200 150

qkT (eVminus1)

100

101

102

103

Tim

e con

stant

s (se

c)


E sim 033 eV

(b)











2O3sensor response











2based






0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV









Recovery time

Response time


0

100

200

300

Tim

e con

stant

(sec

)


2O3


100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2







8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










Other oxides

WO3

ZnO SnO2

In2O3



Ominus O2minus

O2

0 200 300 400 500

Temperature (∘C)

O2minus

100




O2 + erarr2Ominus




2- and









2O3- and SnO

2-based



2O3or SnO




2







3was observed at


2- and



1minus119909Fe119909O3 120572-Ag

2WO4 and Fe

2O3 have maximum


2-


2)




In2O3

Ozone

CO

40nm

70nm60nm

200nm

200100 400 500300

Temperature (∘C)

100

101

102

103

Sens

or re

spon

se

RH sim 45


[43 44 90]





2and In

2O3








SnO2

(111) (200) (020) (112) (120) (110) (101) (011) (011) (101) (010) (001) (100)(110) (010) (010) (110) (100) (221) (221) (221) [99 112 113]






2O3and SnO

2thin films






(110)

(100)

(001)

(101)

SnO2

(a)

(111)

(100)

(110)

In2O3

(b)


2O3


Resp

onse

and

reco

very

tim

e (se

c)

Response

Recovery


103

102

101

100100 200 300 400

In2O3

SnO2

SnO2



2O3- and SnO





2O3



119878 sim (

120591rec120591res

)

119898

(4)



119878 =

119877

1198770

= 119870119862119883 (5)




11

8

3

2

6

4

9

12

107

13

1

5


Ozone

100

101

102

103

104

105

Sens

or re

spon

se





2O3







2O3(sol-









119878gt 0)



be expressed as

119878 =

119866

1198660

sim exp (119902Δ119881119878

119896119879

) lt 1 (6)


O

O

+

minus

O O O

O

+

minus







O3(g) 997888rarr O


3

minus(s) (7)

O3(g) 997888rarr O




3











3was




3




3


2O3



Sn Sn Sn

O

O O

O + O2O3



[136]



2O) A



O3+ VO∙∙+ 2e 999445999468 OO +O

2uarr (9)


2is valid for


2lattice


2

TiO2 and SrTiO










2O3lattice at



2-



2surface is shown


2surface









2uarr + eminus (10)


OH

R(air)

Con

cent

ratio

n (a

u)

Ozone

S

O2

H2O

O

100

101

102

103

Sens

or re

spon

se


105

107

109

Resis

tanc

e (O

hm)



2films



2lattice atoms has


2surface is




2and In

2O3[155 156] Inter-


2



O1s

Sn3d

(a)

(b)


Inte

nsity

of X

PS (O

1s C

1s a

nd S

n3d)

pea

ks (a

u)

500

400

300

200

x 5

C1s

Vacuum Air15

10

5

0

O(ads)


SnO2


∘) A dry air 119879an = 300∘C










1

2

3

4

Recovery

ResponseDry air

Wet air

qkT (eVminus1)

15 17 19 21 23 25 27 29

100

101

102

103

Resp

onse

and

reco

very

tim

es (s

ec)


+ ozone (1ppm)Air






2and sim2 ppm of CH

4






2uarr + eminus (14)


3+OH120575minus (15)




2appeared due







119878


O119878



1

2

6

2

4

0


350 400 450 500 550300Wavelength (nm)

2

4

6

8

EL p

ower

at40

mA

(mW

)

Sens

or re

spon

seR

ozon

eR

air



3 Adapted








2- and In

2O3-based





2 For


50 200150 3000 100 350250

Time (min)

10minus5

10minus4

10minus3

10minus2

10minus1

100

101

102

Spec

con

duct

ivity

(Ωminus1

cmminus1)







2


ℎ] 997904rArr e119878

minus+ h119878

+ (17)

h119878

++O2119878

minus997904rArr O

2119878997904rArr O

2uarr (18)



119877dark119877UV

sim exp(119902ΔB119896119879

) (19)



Table5Ty

picalp

aram

eterso

fRTozon

esensorsop

erated

usingUVph

otoreductio

neffect

Metaloxide

Techno

logyfilm

parameters

UVsourcecon

ditio

nsof

photoreductio

nMax119878

Con

ditio

nsof

measurements

Respon

setim

eRe

covery

time

References

In2O3

Thin


tsim8ndash25

nmUVHglamp(254

nm)vacuum

sim105ndash106

RTsim

30ndash9

0ppb

na

na

[170171173174]

Thickfilm

(mesop

orou

s)dmdashnatsim30

nmUVLE

Dair(100∘C)

sim130ndash

350

PretreatmentRT

02ndash12

ppmdry

Minutes

25ndash53m

in[119175]

Thin

filmdmdashnatmdash

na

UVLE

D(375

nm)air(01P

a)sim4

RT25pp

msim10min

na

[169]

Thin

filmdsim20

nmtsim7n

mUVLE

D(375

nm)na

sim105

RT104p

pmMinutes

Minutes

[176]

Thin

filmdmdashnatsim7n

mUVLE

D(375

nm)air

sim5ndash12

RT03ndash1

ppm

Minutes

Minutes

[121163177]

SnO2

Thin

filmdsim450n

mtmdashna

UVLE

D(370

nm)air

13ndash14

RT10p

pm60

Minutes

Tens

ofminutes

[178]

Thin

filmdsim6ndash

9nmtmdashna

UVLE

D(385

nm)air

sim11

RT100

ppbdry

Tens

ofminutes

Tens

ofminutes

[179]


na

UVlight

(366

nm)air

26RT

25pp

msim50

min

sim4-5m

in[180]

PtSnO2


na

UVlight

(366

nm)air

885

RT25pp

msim6m

insim15

min

[180]

ZnO

Thin

filmdsim150ndash

1000

nmtsim5ndash11nm

UVHglamp(254

nm)vacuum

sim103ndash108

RTn

aTens

ofminutes

Minutes

[38181]

Thin


nmUVlamp(366

nm)air

UVlampair(580∘C)

sim12

sim103

RT25pp

m10min

1min

Minutes

5s(580∘C)

[182]


nmUVLE

D(400

nm)air

sim2ndash25

RT70p

pb50

5ndash10min

Minutes

[183]

ZnO-SnO2


UVlight

(366

nm)air

39RT

25pp

msim2m

insim7m

in[180]

InGaZ

nOTh

infilmdsim65

nmtmdashna

UVLE

D(370

nm)air

14RT

2pp

m10min

gt30

min

[184]

TiO2


UVlight

(366

nm)air

64RT

25pp

msim1m

insim2m

in[180]


LED(460

nm)air

2RT

25pp

msim15

min

sim1m

in[185]

TiO2-SnO2


UVlight

(366

nm)air

327

RT25pp

msim3m

insim15s

[180]

Pt(TiO2-SnO2)(14)


UVlight

(366

nm)air

103

RT25pp

msim3m

insim1m

in[180]

WO3


mLE

D(460

nm)air

64RT

25pp

msim1m

insim1m

in[185]

TiO2-W

O3


mLE

D(460

nm)air

1400

RT25pp

msim3m

insim8m

in[185]

Pt(TiO2-W

O3)(14)


mLE

D(460

nm)air

2700

RT25pp

m15min

15min

[185]

dfilm

thickn

esstgrainsiz

eSsensor

respon

se(119877

ozon

e119877air)con

ditio

nsof

measurements

temperature

ofop

eration

gasc

oncentratio

nandairh

umidity








2O3can catalyt-


2surface is deacti-




2O3and










2O3minus119909



001 01 1 10

100

10

100

(a)

UV

16012080400Time (min)

Resp

onse

tim

e (m

in)

(b)

15ppb

200ppb

25ppm

22ppm

92ppm

In2O3


O3

50

40

30

20

10

0

Resis

tanc

e (kO

hm)



3-concentrations





2O3-





1

2


0 50 100 150 200 250 300 350


10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Con

duct

ivity

(Ωminus1

cmminus1)



0 50 100 150 200


103

104

105

106

107

Sens

or re

spon

seR

ozon

eR

air






2


24ppm ozone LED on

24ppm ozoneLED off

15 30 45 600

Time (min)

Resp

onse

[RR

0]

In2O3

24ppm ozoneLED off

50 100 1500

150

0

02

04

06

(k)

0

04 k

08 k

12 k

16 k









2O3









2films






2O3-





2O3and SnO








3+ (OO-H

+) + 2eminus


2uarr +H

2O uarr

(21)


2or HO



2at





2and In

2O3sensors


2sur-









Different OH-groups

100 200 300 400 5000Temperature (∘C)


Sens

or re

spon

se

100 200 300 400 500

Sens

or re

spon

se

300 400 500 600

Sens

itivi

ty to

air h

umid

ityTh

e rat

io S

(wet

)S(

dry)

SnO2

100

101

102

100

101

102

103

100

101

102

103

104




RH sim 45

RH sim 1-2

RH sim 45

RH sim 1-2





119887




2films deposited



Grain

Grain




diffusion

(a) (b)




119878sim 119881119878 where 119899





119878sim Δ119873

119878





119887sim Δ(MeO)

119904




Elsevier





layerBulk region

Interface region

Grains














119878



119901) in


119901sim 998779(MeO)

119887)


Δ119866 (119905)

= 119870119889(119905) Δ119866

1(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905)

(22)








119889(119905)



Δ119866 (119905) = 119870119889(119905) Δ119866 (23)





Δ119866 (119905) = Δ1198661(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905) (24)




2-





3(119905) could be


Δ1198663(119905) = 119870

119886119889(119905) Δ119866

119888(119905) (25)

1-2 RH

Resp

onse

tim

e (se

c)

100

101

102

103

In2O3

20 40 60 10010Grain size (nm)

120591 sim t2

















0 100 200 300 400Thickness (nm)

Activ

atio

n en

ergy

(eV

)

20

16

12

08

04

0

OzoneResponse

Recovery

Dry

Dry

Wet

Wet

1

2

3

E sim 15 eV

E sim 06 eV



119878


2O3and SnO

2surfaces





2O3 one













2O3surface





2O) in chemisorbed







2O3









1

2

34

5

6035 eV

055 eV

13

eV

100

101

102

103

Tim

e con

stant

s (se

c)


16 qkT (eVminus1)

18 20 22

Esim115

eV

(a)

1

2

34

5

Response

Recovery (wet air)

Dry airWet air

Wet02

8 eV

In2O3

18 20 22 24 26 28 30

400 300 200 150

qkT (eVminus1)

100

101

102

103

Tim

e con

stant

s (se

c)


E sim 033 eV

(b)











2O3sensor response











2based






0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV









Recovery time

Response time


0

100

200

300

Tim

e con

stant

(sec

)


2O3


100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2







8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











2O3or SnO




2







3was observed at


2- and



1minus119909Fe119909O3 120572-Ag

2WO4 and Fe

2O3 have maximum


2-


2)




In2O3

Ozone

CO

40nm

70nm60nm

200nm

200100 400 500300

Temperature (∘C)

100

101

102

103

Sens

or re

spon

se

RH sim 45


[43 44 90]





2and In

2O3








SnO2

(111) (200) (020) (112) (120) (110) (101) (011) (011) (101) (010) (001) (100)(110) (010) (010) (110) (100) (221) (221) (221) [99 112 113]






2O3and SnO

2thin films






(110)

(100)

(001)

(101)

SnO2

(a)

(111)

(100)

(110)

In2O3

(b)


2O3


Resp

onse

and

reco

very

tim

e (se

c)

Response

Recovery


103

102

101

100100 200 300 400

In2O3

SnO2

SnO2



2O3- and SnO





2O3



119878 sim (

120591rec120591res

)

119898

(4)



119878 =

119877

1198770

= 119870119862119883 (5)




11

8

3

2

6

4

9

12

107

13

1

5


Ozone

100

101

102

103

104

105

Sens

or re

spon

se





2O3







2O3(sol-









119878gt 0)



be expressed as

119878 =

119866

1198660

sim exp (119902Δ119881119878

119896119879

) lt 1 (6)


O

O

+

minus

O O O

O

+

minus







O3(g) 997888rarr O


3

minus(s) (7)

O3(g) 997888rarr O




3











3was




3




3


2O3



Sn Sn Sn

O

O O

O + O2O3



[136]



2O) A



O3+ VO∙∙+ 2e 999445999468 OO +O

2uarr (9)


2is valid for


2lattice


2

TiO2 and SrTiO










2O3lattice at



2-



2surface is shown


2surface









2uarr + eminus (10)


OH

R(air)

Con

cent

ratio

n (a

u)

Ozone

S

O2

H2O

O

100

101

102

103

Sens

or re

spon

se


105

107

109

Resis

tanc

e (O

hm)



2films



2lattice atoms has


2surface is




2and In

2O3[155 156] Inter-


2



O1s

Sn3d

(a)

(b)


Inte

nsity

of X

PS (O

1s C

1s a

nd S

n3d)

pea

ks (a

u)

500

400

300

200

x 5

C1s

Vacuum Air15

10

5

0

O(ads)


SnO2


∘) A dry air 119879an = 300∘C










1

2

3

4

Recovery

ResponseDry air

Wet air

qkT (eVminus1)

15 17 19 21 23 25 27 29

100

101

102

103

Resp

onse

and

reco

very

tim

es (s

ec)


+ ozone (1ppm)Air






2and sim2 ppm of CH

4






2uarr + eminus (14)


3+OH120575minus (15)




2appeared due







119878


O119878



1

2

6

2

4

0


350 400 450 500 550300Wavelength (nm)

2

4

6

8

EL p

ower

at40

mA

(mW

)

Sens

or re

spon

seR

ozon

eR

air



3 Adapted








2- and In

2O3-based





2 For


50 200150 3000 100 350250

Time (min)

10minus5

10minus4

10minus3

10minus2

10minus1

100

101

102

Spec

con

duct

ivity

(Ωminus1

cmminus1)







2


ℎ] 997904rArr e119878

minus+ h119878

+ (17)

h119878

++O2119878

minus997904rArr O

2119878997904rArr O

2uarr (18)



119877dark119877UV

sim exp(119902ΔB119896119879

) (19)



Table5Ty

picalp

aram

eterso

fRTozon

esensorsop

erated

usingUVph

otoreductio

neffect

Metaloxide

Techno

logyfilm

parameters

UVsourcecon

ditio

nsof

photoreductio

nMax119878

Con

ditio

nsof

measurements

Respon

setim

eRe

covery

time

References

In2O3

Thin


tsim8ndash25

nmUVHglamp(254

nm)vacuum

sim105ndash106

RTsim

30ndash9

0ppb

na

na

[170171173174]

Thickfilm

(mesop

orou

s)dmdashnatsim30

nmUVLE

Dair(100∘C)

sim130ndash

350

PretreatmentRT

02ndash12

ppmdry

Minutes

25ndash53m

in[119175]

Thin

filmdmdashnatmdash

na

UVLE

D(375

nm)air(01P

a)sim4

RT25pp

msim10min

na

[169]

Thin

filmdsim20

nmtsim7n

mUVLE

D(375

nm)na

sim105

RT104p

pmMinutes

Minutes

[176]

Thin

filmdmdashnatsim7n

mUVLE

D(375

nm)air

sim5ndash12

RT03ndash1

ppm

Minutes

Minutes

[121163177]

SnO2

Thin

filmdsim450n

mtmdashna

UVLE

D(370

nm)air

13ndash14

RT10p

pm60

Minutes

Tens

ofminutes

[178]

Thin

filmdsim6ndash

9nmtmdashna

UVLE

D(385

nm)air

sim11

RT100

ppbdry

Tens

ofminutes

Tens

ofminutes

[179]


na

UVlight

(366

nm)air

26RT

25pp

msim50

min

sim4-5m

in[180]

PtSnO2


na

UVlight

(366

nm)air

885

RT25pp

msim6m

insim15

min

[180]

ZnO

Thin

filmdsim150ndash

1000

nmtsim5ndash11nm

UVHglamp(254

nm)vacuum

sim103ndash108

RTn

aTens

ofminutes

Minutes

[38181]

Thin


nmUVlamp(366

nm)air

UVlampair(580∘C)

sim12

sim103

RT25pp

m10min

1min

Minutes

5s(580∘C)

[182]


nmUVLE

D(400

nm)air

sim2ndash25

RT70p

pb50

5ndash10min

Minutes

[183]

ZnO-SnO2


UVlight

(366

nm)air

39RT

25pp

msim2m

insim7m

in[180]

InGaZ

nOTh

infilmdsim65

nmtmdashna

UVLE

D(370

nm)air

14RT

2pp

m10min

gt30

min

[184]

TiO2


UVlight

(366

nm)air

64RT

25pp

msim1m

insim2m

in[180]


LED(460

nm)air

2RT

25pp

msim15

min

sim1m

in[185]

TiO2-SnO2


UVlight

(366

nm)air

327

RT25pp

msim3m

insim15s

[180]

Pt(TiO2-SnO2)(14)


UVlight

(366

nm)air

103

RT25pp

msim3m

insim1m

in[180]

WO3


mLE

D(460

nm)air

64RT

25pp

msim1m

insim1m

in[185]

TiO2-W

O3


mLE

D(460

nm)air

1400

RT25pp

msim3m

insim8m

in[185]

Pt(TiO2-W

O3)(14)


mLE

D(460

nm)air

2700

RT25pp

m15min

15min

[185]

dfilm

thickn

esstgrainsiz

eSsensor

respon

se(119877

ozon

e119877air)con

ditio

nsof

measurements

temperature

ofop

eration

gasc

oncentratio

nandairh

umidity








2O3can catalyt-


2surface is deacti-




2O3and










2O3minus119909



001 01 1 10

100

10

100

(a)

UV

16012080400Time (min)

Resp

onse

tim

e (m

in)

(b)

15ppb

200ppb

25ppm

22ppm

92ppm

In2O3


O3

50

40

30

20

10

0

Resis

tanc

e (kO

hm)



3-concentrations





2O3-





1

2


0 50 100 150 200 250 300 350


10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Con

duct

ivity

(Ωminus1

cmminus1)



0 50 100 150 200


103

104

105

106

107

Sens

or re

spon

seR

ozon

eR

air






2


24ppm ozone LED on

24ppm ozoneLED off

15 30 45 600

Time (min)

Resp

onse

[RR

0]

In2O3

24ppm ozoneLED off

50 100 1500

150

0

02

04

06

(k)

0

04 k

08 k

12 k

16 k









2O3









2films






2O3-





2O3and SnO








3+ (OO-H

+) + 2eminus


2uarr +H

2O uarr

(21)


2or HO



2at





2and In

2O3sensors


2sur-









Different OH-groups

100 200 300 400 5000Temperature (∘C)


Sens

or re

spon

se

100 200 300 400 500

Sens

or re

spon

se

300 400 500 600

Sens

itivi

ty to

air h

umid

ityTh

e rat

io S

(wet

)S(

dry)

SnO2

100

101

102

100

101

102

103

100

101

102

103

104




RH sim 45

RH sim 1-2

RH sim 45

RH sim 1-2





119887




2films deposited



Grain

Grain




diffusion

(a) (b)




119878sim 119881119878 where 119899





119878sim Δ119873

119878





119887sim Δ(MeO)

119904




Elsevier





layerBulk region

Interface region

Grains














119878



119901) in


119901sim 998779(MeO)

119887)


Δ119866 (119905)

= 119870119889(119905) Δ119866

1(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905)

(22)








119889(119905)



Δ119866 (119905) = 119870119889(119905) Δ119866 (23)





Δ119866 (119905) = Δ1198661(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905) (24)




2-





3(119905) could be


Δ1198663(119905) = 119870

119886119889(119905) Δ119866

119888(119905) (25)

1-2 RH

Resp

onse

tim

e (se

c)

100

101

102

103

In2O3

20 40 60 10010Grain size (nm)

120591 sim t2

















0 100 200 300 400Thickness (nm)

Activ

atio

n en

ergy

(eV

)

20

16

12

08

04

0

OzoneResponse

Recovery

Dry

Dry

Wet

Wet

1

2

3

E sim 15 eV

E sim 06 eV



119878


2O3and SnO

2surfaces





2O3 one













2O3surface





2O) in chemisorbed







2O3









1

2

34

5

6035 eV

055 eV

13

eV

100

101

102

103

Tim

e con

stant

s (se

c)


16 qkT (eVminus1)

18 20 22

Esim115

eV

(a)

1

2

34

5

Response

Recovery (wet air)

Dry airWet air

Wet02

8 eV

In2O3

18 20 22 24 26 28 30

400 300 200 150

qkT (eVminus1)

100

101

102

103

Tim

e con

stant

s (se

c)


E sim 033 eV

(b)











2O3sensor response











2based






0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV









Recovery time

Response time


0

100

200

300

Tim

e con

stant

(sec

)


2O3


100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2







8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation












SnO2

(111) (200) (020) (112) (120) (110) (101) (011) (011) (101) (010) (001) (100)(110) (010) (010) (110) (100) (221) (221) (221) [99 112 113]






2O3and SnO

2thin films






(110)

(100)

(001)

(101)

SnO2

(a)

(111)

(100)

(110)

In2O3

(b)


2O3


Resp

onse

and

reco

very

tim

e (se

c)

Response

Recovery


103

102

101

100100 200 300 400

In2O3

SnO2

SnO2



2O3- and SnO





2O3



119878 sim (

120591rec120591res

)

119898

(4)



119878 =

119877

1198770

= 119870119862119883 (5)




11

8

3

2

6

4

9

12

107

13

1

5


Ozone

100

101

102

103

104

105

Sens

or re

spon

se





2O3







2O3(sol-









119878gt 0)



be expressed as

119878 =

119866

1198660

sim exp (119902Δ119881119878

119896119879

) lt 1 (6)


O

O

+

minus

O O O

O

+

minus







O3(g) 997888rarr O


3

minus(s) (7)

O3(g) 997888rarr O




3











3was




3




3


2O3



Sn Sn Sn

O

O O

O + O2O3



[136]



2O) A



O3+ VO∙∙+ 2e 999445999468 OO +O

2uarr (9)


2is valid for


2lattice


2

TiO2 and SrTiO










2O3lattice at



2-



2surface is shown


2surface









2uarr + eminus (10)


OH

R(air)

Con

cent

ratio

n (a

u)

Ozone

S

O2

H2O

O

100

101

102

103

Sens

or re

spon

se


105

107

109

Resis

tanc

e (O

hm)



2films



2lattice atoms has


2surface is




2and In

2O3[155 156] Inter-


2



O1s

Sn3d

(a)

(b)


Inte

nsity

of X

PS (O

1s C

1s a

nd S

n3d)

pea

ks (a

u)

500

400

300

200

x 5

C1s

Vacuum Air15

10

5

0

O(ads)


SnO2


∘) A dry air 119879an = 300∘C










1

2

3

4

Recovery

ResponseDry air

Wet air

qkT (eVminus1)

15 17 19 21 23 25 27 29

100

101

102

103

Resp

onse

and

reco

very

tim

es (s

ec)


+ ozone (1ppm)Air






2and sim2 ppm of CH

4






2uarr + eminus (14)


3+OH120575minus (15)




2appeared due







119878


O119878



1

2

6

2

4

0


350 400 450 500 550300Wavelength (nm)

2

4

6

8

EL p

ower

at40

mA

(mW

)

Sens

or re

spon

seR

ozon

eR

air



3 Adapted








2- and In

2O3-based





2 For


50 200150 3000 100 350250

Time (min)

10minus5

10minus4

10minus3

10minus2

10minus1

100

101

102

Spec

con

duct

ivity

(Ωminus1

cmminus1)







2


ℎ] 997904rArr e119878

minus+ h119878

+ (17)

h119878

++O2119878

minus997904rArr O

2119878997904rArr O

2uarr (18)



119877dark119877UV

sim exp(119902ΔB119896119879

) (19)



Table5Ty

picalp

aram

eterso

fRTozon

esensorsop

erated

usingUVph

otoreductio

neffect

Metaloxide

Techno

logyfilm

parameters

UVsourcecon

ditio

nsof

photoreductio

nMax119878

Con

ditio

nsof

measurements

Respon

setim

eRe

covery

time

References

In2O3

Thin


tsim8ndash25

nmUVHglamp(254

nm)vacuum

sim105ndash106

RTsim

30ndash9

0ppb

na

na

[170171173174]

Thickfilm

(mesop

orou

s)dmdashnatsim30

nmUVLE

Dair(100∘C)

sim130ndash

350

PretreatmentRT

02ndash12

ppmdry

Minutes

25ndash53m

in[119175]

Thin

filmdmdashnatmdash

na

UVLE

D(375

nm)air(01P

a)sim4

RT25pp

msim10min

na

[169]

Thin

filmdsim20

nmtsim7n

mUVLE

D(375

nm)na

sim105

RT104p

pmMinutes

Minutes

[176]

Thin

filmdmdashnatsim7n

mUVLE

D(375

nm)air

sim5ndash12

RT03ndash1

ppm

Minutes

Minutes

[121163177]

SnO2

Thin

filmdsim450n

mtmdashna

UVLE

D(370

nm)air

13ndash14

RT10p

pm60

Minutes

Tens

ofminutes

[178]

Thin

filmdsim6ndash

9nmtmdashna

UVLE

D(385

nm)air

sim11

RT100

ppbdry

Tens

ofminutes

Tens

ofminutes

[179]


na

UVlight

(366

nm)air

26RT

25pp

msim50

min

sim4-5m

in[180]

PtSnO2


na

UVlight

(366

nm)air

885

RT25pp

msim6m

insim15

min

[180]

ZnO

Thin

filmdsim150ndash

1000

nmtsim5ndash11nm

UVHglamp(254

nm)vacuum

sim103ndash108

RTn

aTens

ofminutes

Minutes

[38181]

Thin


nmUVlamp(366

nm)air

UVlampair(580∘C)

sim12

sim103

RT25pp

m10min

1min

Minutes

5s(580∘C)

[182]


nmUVLE

D(400

nm)air

sim2ndash25

RT70p

pb50

5ndash10min

Minutes

[183]

ZnO-SnO2


UVlight

(366

nm)air

39RT

25pp

msim2m

insim7m

in[180]

InGaZ

nOTh

infilmdsim65

nmtmdashna

UVLE

D(370

nm)air

14RT

2pp

m10min

gt30

min

[184]

TiO2


UVlight

(366

nm)air

64RT

25pp

msim1m

insim2m

in[180]


LED(460

nm)air

2RT

25pp

msim15

min

sim1m

in[185]

TiO2-SnO2


UVlight

(366

nm)air

327

RT25pp

msim3m

insim15s

[180]

Pt(TiO2-SnO2)(14)


UVlight

(366

nm)air

103

RT25pp

msim3m

insim1m

in[180]

WO3


mLE

D(460

nm)air

64RT

25pp

msim1m

insim1m

in[185]

TiO2-W

O3


mLE

D(460

nm)air

1400

RT25pp

msim3m

insim8m

in[185]

Pt(TiO2-W

O3)(14)


mLE

D(460

nm)air

2700

RT25pp

m15min

15min

[185]

dfilm

thickn

esstgrainsiz

eSsensor

respon

se(119877

ozon

e119877air)con

ditio

nsof

measurements

temperature

ofop

eration

gasc

oncentratio

nandairh

umidity








2O3can catalyt-


2surface is deacti-




2O3and










2O3minus119909



001 01 1 10

100

10

100

(a)

UV

16012080400Time (min)

Resp

onse

tim

e (m

in)

(b)

15ppb

200ppb

25ppm

22ppm

92ppm

In2O3


O3

50

40

30

20

10

0

Resis

tanc

e (kO

hm)



3-concentrations





2O3-





1

2


0 50 100 150 200 250 300 350


10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Con

duct

ivity

(Ωminus1

cmminus1)



0 50 100 150 200


103

104

105

106

107

Sens

or re

spon

seR

ozon

eR

air






2


24ppm ozone LED on

24ppm ozoneLED off

15 30 45 600

Time (min)

Resp

onse

[RR

0]

In2O3

24ppm ozoneLED off

50 100 1500

150

0

02

04

06

(k)

0

04 k

08 k

12 k

16 k









2O3









2films






2O3-





2O3and SnO








3+ (OO-H

+) + 2eminus


2uarr +H

2O uarr

(21)


2or HO



2at





2and In

2O3sensors


2sur-









Different OH-groups

100 200 300 400 5000Temperature (∘C)


Sens

or re

spon

se

100 200 300 400 500

Sens

or re

spon

se

300 400 500 600

Sens

itivi

ty to

air h

umid

ityTh

e rat

io S

(wet

)S(

dry)

SnO2

100

101

102

100

101

102

103

100

101

102

103

104




RH sim 45

RH sim 1-2

RH sim 45

RH sim 1-2





119887




2films deposited



Grain

Grain




diffusion

(a) (b)




119878sim 119881119878 where 119899





119878sim Δ119873

119878





119887sim Δ(MeO)

119904




Elsevier





layerBulk region

Interface region

Grains














119878



119901) in


119901sim 998779(MeO)

119887)


Δ119866 (119905)

= 119870119889(119905) Δ119866

1(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905)

(22)








119889(119905)



Δ119866 (119905) = 119870119889(119905) Δ119866 (23)





Δ119866 (119905) = Δ1198661(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905) (24)




2-





3(119905) could be


Δ1198663(119905) = 119870

119886119889(119905) Δ119866

119888(119905) (25)

1-2 RH

Resp

onse

tim

e (se

c)

100

101

102

103

In2O3

20 40 60 10010Grain size (nm)

120591 sim t2

















0 100 200 300 400Thickness (nm)

Activ

atio

n en

ergy

(eV

)

20

16

12

08

04

0

OzoneResponse

Recovery

Dry

Dry

Wet

Wet

1

2

3

E sim 15 eV

E sim 06 eV



119878


2O3and SnO

2surfaces





2O3 one













2O3surface





2O) in chemisorbed







2O3









1

2

34

5

6035 eV

055 eV

13

eV

100

101

102

103

Tim

e con

stant

s (se

c)


16 qkT (eVminus1)

18 20 22

Esim115

eV

(a)

1

2

34

5

Response

Recovery (wet air)

Dry airWet air

Wet02

8 eV

In2O3

18 20 22 24 26 28 30

400 300 200 150

qkT (eVminus1)

100

101

102

103

Tim

e con

stant

s (se

c)


E sim 033 eV

(b)











2O3sensor response











2based






0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV









Recovery time

Response time


0

100

200

300

Tim

e con

stant

(sec

)


2O3


100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2







8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











2O3



119878 sim (

120591rec120591res

)

119898

(4)



119878 =

119877

1198770

= 119870119862119883 (5)




11

8

3

2

6

4

9

12

107

13

1

5


Ozone

100

101

102

103

104

105

Sens

or re

spon

se





2O3







2O3(sol-









119878gt 0)



be expressed as

119878 =

119866

1198660

sim exp (119902Δ119881119878

119896119879

) lt 1 (6)


O

O

+

minus

O O O

O

+

minus







O3(g) 997888rarr O


3

minus(s) (7)

O3(g) 997888rarr O




3











3was




3




3


2O3



Sn Sn Sn

O

O O

O + O2O3



[136]



2O) A



O3+ VO∙∙+ 2e 999445999468 OO +O

2uarr (9)


2is valid for


2lattice


2

TiO2 and SrTiO










2O3lattice at



2-



2surface is shown


2surface









2uarr + eminus (10)


OH

R(air)

Con

cent

ratio

n (a

u)

Ozone

S

O2

H2O

O

100

101

102

103

Sens

or re

spon

se


105

107

109

Resis

tanc

e (O

hm)



2films



2lattice atoms has


2surface is




2and In

2O3[155 156] Inter-


2



O1s

Sn3d

(a)

(b)


Inte

nsity

of X

PS (O

1s C

1s a

nd S

n3d)

pea

ks (a

u)

500

400

300

200

x 5

C1s

Vacuum Air15

10

5

0

O(ads)


SnO2


∘) A dry air 119879an = 300∘C










1

2

3

4

Recovery

ResponseDry air

Wet air

qkT (eVminus1)

15 17 19 21 23 25 27 29

100

101

102

103

Resp

onse

and

reco

very

tim

es (s

ec)


+ ozone (1ppm)Air






2and sim2 ppm of CH

4






2uarr + eminus (14)


3+OH120575minus (15)




2appeared due







119878


O119878



1

2

6

2

4

0


350 400 450 500 550300Wavelength (nm)

2

4

6

8

EL p

ower

at40

mA

(mW

)

Sens

or re

spon

seR

ozon

eR

air



3 Adapted








2- and In

2O3-based





2 For


50 200150 3000 100 350250

Time (min)

10minus5

10minus4

10minus3

10minus2

10minus1

100

101

102

Spec

con

duct

ivity

(Ωminus1

cmminus1)







2


ℎ] 997904rArr e119878

minus+ h119878

+ (17)

h119878

++O2119878

minus997904rArr O

2119878997904rArr O

2uarr (18)



119877dark119877UV

sim exp(119902ΔB119896119879

) (19)



Table5Ty

picalp

aram

eterso

fRTozon

esensorsop

erated

usingUVph

otoreductio

neffect

Metaloxide

Techno

logyfilm

parameters

UVsourcecon

ditio

nsof

photoreductio

nMax119878

Con

ditio

nsof

measurements

Respon

setim

eRe

covery

time

References

In2O3

Thin


tsim8ndash25

nmUVHglamp(254

nm)vacuum

sim105ndash106

RTsim

30ndash9

0ppb

na

na

[170171173174]

Thickfilm

(mesop

orou

s)dmdashnatsim30

nmUVLE

Dair(100∘C)

sim130ndash

350

PretreatmentRT

02ndash12

ppmdry

Minutes

25ndash53m

in[119175]

Thin

filmdmdashnatmdash

na

UVLE

D(375

nm)air(01P

a)sim4

RT25pp

msim10min

na

[169]

Thin

filmdsim20

nmtsim7n

mUVLE

D(375

nm)na

sim105

RT104p

pmMinutes

Minutes

[176]

Thin

filmdmdashnatsim7n

mUVLE

D(375

nm)air

sim5ndash12

RT03ndash1

ppm

Minutes

Minutes

[121163177]

SnO2

Thin

filmdsim450n

mtmdashna

UVLE

D(370

nm)air

13ndash14

RT10p

pm60

Minutes

Tens

ofminutes

[178]

Thin

filmdsim6ndash

9nmtmdashna

UVLE

D(385

nm)air

sim11

RT100

ppbdry

Tens

ofminutes

Tens

ofminutes

[179]


na

UVlight

(366

nm)air

26RT

25pp

msim50

min

sim4-5m

in[180]

PtSnO2


na

UVlight

(366

nm)air

885

RT25pp

msim6m

insim15

min

[180]

ZnO

Thin

filmdsim150ndash

1000

nmtsim5ndash11nm

UVHglamp(254

nm)vacuum

sim103ndash108

RTn

aTens

ofminutes

Minutes

[38181]

Thin


nmUVlamp(366

nm)air

UVlampair(580∘C)

sim12

sim103

RT25pp

m10min

1min

Minutes

5s(580∘C)

[182]


nmUVLE

D(400

nm)air

sim2ndash25

RT70p

pb50

5ndash10min

Minutes

[183]

ZnO-SnO2


UVlight

(366

nm)air

39RT

25pp

msim2m

insim7m

in[180]

InGaZ

nOTh

infilmdsim65

nmtmdashna

UVLE

D(370

nm)air

14RT

2pp

m10min

gt30

min

[184]

TiO2


UVlight

(366

nm)air

64RT

25pp

msim1m

insim2m

in[180]


LED(460

nm)air

2RT

25pp

msim15

min

sim1m

in[185]

TiO2-SnO2


UVlight

(366

nm)air

327

RT25pp

msim3m

insim15s

[180]

Pt(TiO2-SnO2)(14)


UVlight

(366

nm)air

103

RT25pp

msim3m

insim1m

in[180]

WO3


mLE

D(460

nm)air

64RT

25pp

msim1m

insim1m

in[185]

TiO2-W

O3


mLE

D(460

nm)air

1400

RT25pp

msim3m

insim8m

in[185]

Pt(TiO2-W

O3)(14)


mLE

D(460

nm)air

2700

RT25pp

m15min

15min

[185]

dfilm

thickn

esstgrainsiz

eSsensor

respon

se(119877

ozon

e119877air)con

ditio

nsof

measurements

temperature

ofop

eration

gasc

oncentratio

nandairh

umidity








2O3can catalyt-


2surface is deacti-




2O3and










2O3minus119909



001 01 1 10

100

10

100

(a)

UV

16012080400Time (min)

Resp

onse

tim

e (m

in)

(b)

15ppb

200ppb

25ppm

22ppm

92ppm

In2O3


O3

50

40

30

20

10

0

Resis

tanc

e (kO

hm)



3-concentrations





2O3-





1

2


0 50 100 150 200 250 300 350


10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Con

duct

ivity

(Ωminus1

cmminus1)



0 50 100 150 200


103

104

105

106

107

Sens

or re

spon

seR

ozon

eR

air






2


24ppm ozone LED on

24ppm ozoneLED off

15 30 45 600

Time (min)

Resp

onse

[RR

0]

In2O3

24ppm ozoneLED off

50 100 1500

150

0

02

04

06

(k)

0

04 k

08 k

12 k

16 k









2O3









2films






2O3-





2O3and SnO








3+ (OO-H

+) + 2eminus


2uarr +H

2O uarr

(21)


2or HO



2at





2and In

2O3sensors


2sur-









Different OH-groups

100 200 300 400 5000Temperature (∘C)


Sens

or re

spon

se

100 200 300 400 500

Sens

or re

spon

se

300 400 500 600

Sens

itivi

ty to

air h

umid

ityTh

e rat

io S

(wet

)S(

dry)

SnO2

100

101

102

100

101

102

103

100

101

102

103

104




RH sim 45

RH sim 1-2

RH sim 45

RH sim 1-2





119887




2films deposited



Grain

Grain




diffusion

(a) (b)




119878sim 119881119878 where 119899





119878sim Δ119873

119878





119887sim Δ(MeO)

119904




Elsevier





layerBulk region

Interface region

Grains














119878



119901) in


119901sim 998779(MeO)

119887)


Δ119866 (119905)

= 119870119889(119905) Δ119866

1(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905)

(22)








119889(119905)



Δ119866 (119905) = 119870119889(119905) Δ119866 (23)





Δ119866 (119905) = Δ1198661(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905) (24)




2-





3(119905) could be


Δ1198663(119905) = 119870

119886119889(119905) Δ119866

119888(119905) (25)

1-2 RH

Resp

onse

tim

e (se

c)

100

101

102

103

In2O3

20 40 60 10010Grain size (nm)

120591 sim t2

















0 100 200 300 400Thickness (nm)

Activ

atio

n en

ergy

(eV

)

20

16

12

08

04

0

OzoneResponse

Recovery

Dry

Dry

Wet

Wet

1

2

3

E sim 15 eV

E sim 06 eV



119878


2O3and SnO

2surfaces





2O3 one













2O3surface





2O) in chemisorbed







2O3









1

2

34

5

6035 eV

055 eV

13

eV

100

101

102

103

Tim

e con

stant

s (se

c)


16 qkT (eVminus1)

18 20 22

Esim115

eV

(a)

1

2

34

5

Response

Recovery (wet air)

Dry airWet air

Wet02

8 eV

In2O3

18 20 22 24 26 28 30

400 300 200 150

qkT (eVminus1)

100

101

102

103

Tim

e con

stant

s (se

c)


E sim 033 eV

(b)











2O3sensor response











2based






0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV









Recovery time

Response time


0

100

200

300

Tim

e con

stant

(sec

)


2O3


100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2







8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










O

O

+

minus

O O O

O

+

minus







O3(g) 997888rarr O


3

minus(s) (7)

O3(g) 997888rarr O




3











3was




3




3


2O3



Sn Sn Sn

O

O O

O + O2O3



[136]



2O) A



O3+ VO∙∙+ 2e 999445999468 OO +O

2uarr (9)


2is valid for


2lattice


2

TiO2 and SrTiO










2O3lattice at



2-



2surface is shown


2surface









2uarr + eminus (10)


OH

R(air)

Con

cent

ratio

n (a

u)

Ozone

S

O2

H2O

O

100

101

102

103

Sens

or re

spon

se


105

107

109

Resis

tanc

e (O

hm)



2films



2lattice atoms has


2surface is




2and In

2O3[155 156] Inter-


2



O1s

Sn3d

(a)

(b)


Inte

nsity

of X

PS (O

1s C

1s a

nd S

n3d)

pea

ks (a

u)

500

400

300

200

x 5

C1s

Vacuum Air15

10

5

0

O(ads)


SnO2


∘) A dry air 119879an = 300∘C










1

2

3

4

Recovery

ResponseDry air

Wet air

qkT (eVminus1)

15 17 19 21 23 25 27 29

100

101

102

103

Resp

onse

and

reco

very

tim

es (s

ec)


+ ozone (1ppm)Air






2and sim2 ppm of CH

4






2uarr + eminus (14)


3+OH120575minus (15)




2appeared due







119878


O119878



1

2

6

2

4

0


350 400 450 500 550300Wavelength (nm)

2

4

6

8

EL p

ower

at40

mA

(mW

)

Sens

or re

spon

seR

ozon

eR

air



3 Adapted








2- and In

2O3-based





2 For


50 200150 3000 100 350250

Time (min)

10minus5

10minus4

10minus3

10minus2

10minus1

100

101

102

Spec

con

duct

ivity

(Ωminus1

cmminus1)







2


ℎ] 997904rArr e119878

minus+ h119878

+ (17)

h119878

++O2119878

minus997904rArr O

2119878997904rArr O

2uarr (18)



119877dark119877UV

sim exp(119902ΔB119896119879

) (19)



Table5Ty

picalp

aram

eterso

fRTozon

esensorsop

erated

usingUVph

otoreductio

neffect

Metaloxide

Techno

logyfilm

parameters

UVsourcecon

ditio

nsof

photoreductio

nMax119878

Con

ditio

nsof

measurements

Respon

setim

eRe

covery

time

References

In2O3

Thin


tsim8ndash25

nmUVHglamp(254

nm)vacuum

sim105ndash106

RTsim

30ndash9

0ppb

na

na

[170171173174]

Thickfilm

(mesop

orou

s)dmdashnatsim30

nmUVLE

Dair(100∘C)

sim130ndash

350

PretreatmentRT

02ndash12

ppmdry

Minutes

25ndash53m

in[119175]

Thin

filmdmdashnatmdash

na

UVLE

D(375

nm)air(01P

a)sim4

RT25pp

msim10min

na

[169]

Thin

filmdsim20

nmtsim7n

mUVLE

D(375

nm)na

sim105

RT104p

pmMinutes

Minutes

[176]

Thin

filmdmdashnatsim7n

mUVLE

D(375

nm)air

sim5ndash12

RT03ndash1

ppm

Minutes

Minutes

[121163177]

SnO2

Thin

filmdsim450n

mtmdashna

UVLE

D(370

nm)air

13ndash14

RT10p

pm60

Minutes

Tens

ofminutes

[178]

Thin

filmdsim6ndash

9nmtmdashna

UVLE

D(385

nm)air

sim11

RT100

ppbdry

Tens

ofminutes

Tens

ofminutes

[179]


na

UVlight

(366

nm)air

26RT

25pp

msim50

min

sim4-5m

in[180]

PtSnO2


na

UVlight

(366

nm)air

885

RT25pp

msim6m

insim15

min

[180]

ZnO

Thin

filmdsim150ndash

1000

nmtsim5ndash11nm

UVHglamp(254

nm)vacuum

sim103ndash108

RTn

aTens

ofminutes

Minutes

[38181]

Thin


nmUVlamp(366

nm)air

UVlampair(580∘C)

sim12

sim103

RT25pp

m10min

1min

Minutes

5s(580∘C)

[182]


nmUVLE

D(400

nm)air

sim2ndash25

RT70p

pb50

5ndash10min

Minutes

[183]

ZnO-SnO2


UVlight

(366

nm)air

39RT

25pp

msim2m

insim7m

in[180]

InGaZ

nOTh

infilmdsim65

nmtmdashna

UVLE

D(370

nm)air

14RT

2pp

m10min

gt30

min

[184]

TiO2


UVlight

(366

nm)air

64RT

25pp

msim1m

insim2m

in[180]


LED(460

nm)air

2RT

25pp

msim15

min

sim1m

in[185]

TiO2-SnO2


UVlight

(366

nm)air

327

RT25pp

msim3m

insim15s

[180]

Pt(TiO2-SnO2)(14)


UVlight

(366

nm)air

103

RT25pp

msim3m

insim1m

in[180]

WO3


mLE

D(460

nm)air

64RT

25pp

msim1m

insim1m

in[185]

TiO2-W

O3


mLE

D(460

nm)air

1400

RT25pp

msim3m

insim8m

in[185]

Pt(TiO2-W

O3)(14)


mLE

D(460

nm)air

2700

RT25pp

m15min

15min

[185]

dfilm

thickn

esstgrainsiz

eSsensor

respon

se(119877

ozon

e119877air)con

ditio

nsof

measurements

temperature

ofop

eration

gasc

oncentratio

nandairh

umidity








2O3can catalyt-


2surface is deacti-




2O3and










2O3minus119909



001 01 1 10

100

10

100

(a)

UV

16012080400Time (min)

Resp

onse

tim

e (m

in)

(b)

15ppb

200ppb

25ppm

22ppm

92ppm

In2O3


O3

50

40

30

20

10

0

Resis

tanc

e (kO

hm)



3-concentrations





2O3-





1

2


0 50 100 150 200 250 300 350


10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Con

duct

ivity

(Ωminus1

cmminus1)



0 50 100 150 200


103

104

105

106

107

Sens

or re

spon

seR

ozon

eR

air






2


24ppm ozone LED on

24ppm ozoneLED off

15 30 45 600

Time (min)

Resp

onse

[RR

0]

In2O3

24ppm ozoneLED off

50 100 1500

150

0

02

04

06

(k)

0

04 k

08 k

12 k

16 k









2O3









2films






2O3-





2O3and SnO








3+ (OO-H

+) + 2eminus


2uarr +H

2O uarr

(21)


2or HO



2at





2and In

2O3sensors


2sur-









Different OH-groups

100 200 300 400 5000Temperature (∘C)


Sens

or re

spon

se

100 200 300 400 500

Sens

or re

spon

se

300 400 500 600

Sens

itivi

ty to

air h

umid

ityTh

e rat

io S

(wet

)S(

dry)

SnO2

100

101

102

100

101

102

103

100

101

102

103

104




RH sim 45

RH sim 1-2

RH sim 45

RH sim 1-2





119887




2films deposited



Grain

Grain




diffusion

(a) (b)




119878sim 119881119878 where 119899





119878sim Δ119873

119878





119887sim Δ(MeO)

119904




Elsevier





layerBulk region

Interface region

Grains














119878



119901) in


119901sim 998779(MeO)

119887)


Δ119866 (119905)

= 119870119889(119905) Δ119866

1(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905)

(22)








119889(119905)



Δ119866 (119905) = 119870119889(119905) Δ119866 (23)





Δ119866 (119905) = Δ1198661(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905) (24)




2-





3(119905) could be


Δ1198663(119905) = 119870

119886119889(119905) Δ119866

119888(119905) (25)

1-2 RH

Resp

onse

tim

e (se

c)

100

101

102

103

In2O3

20 40 60 10010Grain size (nm)

120591 sim t2

















0 100 200 300 400Thickness (nm)

Activ

atio

n en

ergy

(eV

)

20

16

12

08

04

0

OzoneResponse

Recovery

Dry

Dry

Wet

Wet

1

2

3

E sim 15 eV

E sim 06 eV



119878


2O3and SnO

2surfaces





2O3 one













2O3surface





2O) in chemisorbed







2O3









1

2

34

5

6035 eV

055 eV

13

eV

100

101

102

103

Tim

e con

stant

s (se

c)


16 qkT (eVminus1)

18 20 22

Esim115

eV

(a)

1

2

34

5

Response

Recovery (wet air)

Dry airWet air

Wet02

8 eV

In2O3

18 20 22 24 26 28 30

400 300 200 150

qkT (eVminus1)

100

101

102

103

Tim

e con

stant

s (se

c)


E sim 033 eV

(b)











2O3sensor response











2based






0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV









Recovery time

Response time


0

100

200

300

Tim

e con

stant

(sec

)


2O3


100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2







8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation
















2O3lattice at



2-



2surface is shown


2surface









2uarr + eminus (10)


OH

R(air)

Con

cent

ratio

n (a

u)

Ozone

S

O2

H2O

O

100

101

102

103

Sens

or re

spon

se


105

107

109

Resis

tanc

e (O

hm)



2films



2lattice atoms has


2surface is




2and In

2O3[155 156] Inter-


2



O1s

Sn3d

(a)

(b)


Inte

nsity

of X

PS (O

1s C

1s a

nd S

n3d)

pea

ks (a

u)

500

400

300

200

x 5

C1s

Vacuum Air15

10

5

0

O(ads)


SnO2


∘) A dry air 119879an = 300∘C










1

2

3

4

Recovery

ResponseDry air

Wet air

qkT (eVminus1)

15 17 19 21 23 25 27 29

100

101

102

103

Resp

onse

and

reco

very

tim

es (s

ec)


+ ozone (1ppm)Air






2and sim2 ppm of CH

4






2uarr + eminus (14)


3+OH120575minus (15)




2appeared due







119878


O119878



1

2

6

2

4

0


350 400 450 500 550300Wavelength (nm)

2

4

6

8

EL p

ower

at40

mA

(mW

)

Sens

or re

spon

seR

ozon

eR

air



3 Adapted








2- and In

2O3-based





2 For


50 200150 3000 100 350250

Time (min)

10minus5

10minus4

10minus3

10minus2

10minus1

100

101

102

Spec

con

duct

ivity

(Ωminus1

cmminus1)







2


ℎ] 997904rArr e119878

minus+ h119878

+ (17)

h119878

++O2119878

minus997904rArr O

2119878997904rArr O

2uarr (18)



119877dark119877UV

sim exp(119902ΔB119896119879

) (19)



Table5Ty

picalp

aram

eterso

fRTozon

esensorsop

erated

usingUVph

otoreductio

neffect

Metaloxide

Techno

logyfilm

parameters

UVsourcecon

ditio

nsof

photoreductio

nMax119878

Con

ditio

nsof

measurements

Respon

setim

eRe

covery

time

References

In2O3

Thin


tsim8ndash25

nmUVHglamp(254

nm)vacuum

sim105ndash106

RTsim

30ndash9

0ppb

na

na

[170171173174]

Thickfilm

(mesop

orou

s)dmdashnatsim30

nmUVLE

Dair(100∘C)

sim130ndash

350

PretreatmentRT

02ndash12

ppmdry

Minutes

25ndash53m

in[119175]

Thin

filmdmdashnatmdash

na

UVLE

D(375

nm)air(01P

a)sim4

RT25pp

msim10min

na

[169]

Thin

filmdsim20

nmtsim7n

mUVLE

D(375

nm)na

sim105

RT104p

pmMinutes

Minutes

[176]

Thin

filmdmdashnatsim7n

mUVLE

D(375

nm)air

sim5ndash12

RT03ndash1

ppm

Minutes

Minutes

[121163177]

SnO2

Thin

filmdsim450n

mtmdashna

UVLE

D(370

nm)air

13ndash14

RT10p

pm60

Minutes

Tens

ofminutes

[178]

Thin

filmdsim6ndash

9nmtmdashna

UVLE

D(385

nm)air

sim11

RT100

ppbdry

Tens

ofminutes

Tens

ofminutes

[179]


na

UVlight

(366

nm)air

26RT

25pp

msim50

min

sim4-5m

in[180]

PtSnO2


na

UVlight

(366

nm)air

885

RT25pp

msim6m

insim15

min

[180]

ZnO

Thin

filmdsim150ndash

1000

nmtsim5ndash11nm

UVHglamp(254

nm)vacuum

sim103ndash108

RTn

aTens

ofminutes

Minutes

[38181]

Thin


nmUVlamp(366

nm)air

UVlampair(580∘C)

sim12

sim103

RT25pp

m10min

1min

Minutes

5s(580∘C)

[182]


nmUVLE

D(400

nm)air

sim2ndash25

RT70p

pb50

5ndash10min

Minutes

[183]

ZnO-SnO2


UVlight

(366

nm)air

39RT

25pp

msim2m

insim7m

in[180]

InGaZ

nOTh

infilmdsim65

nmtmdashna

UVLE

D(370

nm)air

14RT

2pp

m10min

gt30

min

[184]

TiO2


UVlight

(366

nm)air

64RT

25pp

msim1m

insim2m

in[180]


LED(460

nm)air

2RT

25pp

msim15

min

sim1m

in[185]

TiO2-SnO2


UVlight

(366

nm)air

327

RT25pp

msim3m

insim15s

[180]

Pt(TiO2-SnO2)(14)


UVlight

(366

nm)air

103

RT25pp

msim3m

insim1m

in[180]

WO3


mLE

D(460

nm)air

64RT

25pp

msim1m

insim1m

in[185]

TiO2-W

O3


mLE

D(460

nm)air

1400

RT25pp

msim3m

insim8m

in[185]

Pt(TiO2-W

O3)(14)


mLE

D(460

nm)air

2700

RT25pp

m15min

15min

[185]

dfilm

thickn

esstgrainsiz

eSsensor

respon

se(119877

ozon

e119877air)con

ditio

nsof

measurements

temperature

ofop

eration

gasc

oncentratio

nandairh

umidity








2O3can catalyt-


2surface is deacti-




2O3and










2O3minus119909



001 01 1 10

100

10

100

(a)

UV

16012080400Time (min)

Resp

onse

tim

e (m

in)

(b)

15ppb

200ppb

25ppm

22ppm

92ppm

In2O3


O3

50

40

30

20

10

0

Resis

tanc

e (kO

hm)



3-concentrations





2O3-





1

2


0 50 100 150 200 250 300 350


10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Con

duct

ivity

(Ωminus1

cmminus1)



0 50 100 150 200


103

104

105

106

107

Sens

or re

spon

seR

ozon

eR

air






2


24ppm ozone LED on

24ppm ozoneLED off

15 30 45 600

Time (min)

Resp

onse

[RR

0]

In2O3

24ppm ozoneLED off

50 100 1500

150

0

02

04

06

(k)

0

04 k

08 k

12 k

16 k









2O3









2films






2O3-





2O3and SnO








3+ (OO-H

+) + 2eminus


2uarr +H

2O uarr

(21)


2or HO



2at





2and In

2O3sensors


2sur-









Different OH-groups

100 200 300 400 5000Temperature (∘C)


Sens

or re

spon

se

100 200 300 400 500

Sens

or re

spon

se

300 400 500 600

Sens

itivi

ty to

air h

umid

ityTh

e rat

io S

(wet

)S(

dry)

SnO2

100

101

102

100

101

102

103

100

101

102

103

104




RH sim 45

RH sim 1-2

RH sim 45

RH sim 1-2





119887




2films deposited



Grain

Grain




diffusion

(a) (b)




119878sim 119881119878 where 119899





119878sim Δ119873

119878





119887sim Δ(MeO)

119904




Elsevier





layerBulk region

Interface region

Grains














119878



119901) in


119901sim 998779(MeO)

119887)


Δ119866 (119905)

= 119870119889(119905) Δ119866

1(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905)

(22)








119889(119905)



Δ119866 (119905) = 119870119889(119905) Δ119866 (23)





Δ119866 (119905) = Δ1198661(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905) (24)




2-





3(119905) could be


Δ1198663(119905) = 119870

119886119889(119905) Δ119866

119888(119905) (25)

1-2 RH

Resp

onse

tim

e (se

c)

100

101

102

103

In2O3

20 40 60 10010Grain size (nm)

120591 sim t2

















0 100 200 300 400Thickness (nm)

Activ

atio

n en

ergy

(eV

)

20

16

12

08

04

0

OzoneResponse

Recovery

Dry

Dry

Wet

Wet

1

2

3

E sim 15 eV

E sim 06 eV



119878


2O3and SnO

2surfaces





2O3 one













2O3surface





2O) in chemisorbed







2O3









1

2

34

5

6035 eV

055 eV

13

eV

100

101

102

103

Tim

e con

stant

s (se

c)


16 qkT (eVminus1)

18 20 22

Esim115

eV

(a)

1

2

34

5

Response

Recovery (wet air)

Dry airWet air

Wet02

8 eV

In2O3

18 20 22 24 26 28 30

400 300 200 150

qkT (eVminus1)

100

101

102

103

Tim

e con

stant

s (se

c)


E sim 033 eV

(b)











2O3sensor response











2based






0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV









Recovery time

Response time


0

100

200

300

Tim

e con

stant

(sec

)


2O3


100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2







8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










O1s

Sn3d

(a)

(b)


Inte

nsity

of X

PS (O

1s C

1s a

nd S

n3d)

pea

ks (a

u)

500

400

300

200

x 5

C1s

Vacuum Air15

10

5

0

O(ads)


SnO2


∘) A dry air 119879an = 300∘C










1

2

3

4

Recovery

ResponseDry air

Wet air

qkT (eVminus1)

15 17 19 21 23 25 27 29

100

101

102

103

Resp

onse

and

reco

very

tim

es (s

ec)


+ ozone (1ppm)Air






2and sim2 ppm of CH

4






2uarr + eminus (14)


3+OH120575minus (15)




2appeared due







119878


O119878



1

2

6

2

4

0


350 400 450 500 550300Wavelength (nm)

2

4

6

8

EL p

ower

at40

mA

(mW

)

Sens

or re

spon

seR

ozon

eR

air



3 Adapted








2- and In

2O3-based





2 For


50 200150 3000 100 350250

Time (min)

10minus5

10minus4

10minus3

10minus2

10minus1

100

101

102

Spec

con

duct

ivity

(Ωminus1

cmminus1)







2


ℎ] 997904rArr e119878

minus+ h119878

+ (17)

h119878

++O2119878

minus997904rArr O

2119878997904rArr O

2uarr (18)



119877dark119877UV

sim exp(119902ΔB119896119879

) (19)



Table5Ty

picalp

aram

eterso

fRTozon

esensorsop

erated

usingUVph

otoreductio

neffect

Metaloxide

Techno

logyfilm

parameters

UVsourcecon

ditio

nsof

photoreductio

nMax119878

Con

ditio

nsof

measurements

Respon

setim

eRe

covery

time

References

In2O3

Thin


tsim8ndash25

nmUVHglamp(254

nm)vacuum

sim105ndash106

RTsim

30ndash9

0ppb

na

na

[170171173174]

Thickfilm

(mesop

orou

s)dmdashnatsim30

nmUVLE

Dair(100∘C)

sim130ndash

350

PretreatmentRT

02ndash12

ppmdry

Minutes

25ndash53m

in[119175]

Thin

filmdmdashnatmdash

na

UVLE

D(375

nm)air(01P

a)sim4

RT25pp

msim10min

na

[169]

Thin

filmdsim20

nmtsim7n

mUVLE

D(375

nm)na

sim105

RT104p

pmMinutes

Minutes

[176]

Thin

filmdmdashnatsim7n

mUVLE

D(375

nm)air

sim5ndash12

RT03ndash1

ppm

Minutes

Minutes

[121163177]

SnO2

Thin

filmdsim450n

mtmdashna

UVLE

D(370

nm)air

13ndash14

RT10p

pm60

Minutes

Tens

ofminutes

[178]

Thin

filmdsim6ndash

9nmtmdashna

UVLE

D(385

nm)air

sim11

RT100

ppbdry

Tens

ofminutes

Tens

ofminutes

[179]


na

UVlight

(366

nm)air

26RT

25pp

msim50

min

sim4-5m

in[180]

PtSnO2


na

UVlight

(366

nm)air

885

RT25pp

msim6m

insim15

min

[180]

ZnO

Thin

filmdsim150ndash

1000

nmtsim5ndash11nm

UVHglamp(254

nm)vacuum

sim103ndash108

RTn

aTens

ofminutes

Minutes

[38181]

Thin


nmUVlamp(366

nm)air

UVlampair(580∘C)

sim12

sim103

RT25pp

m10min

1min

Minutes

5s(580∘C)

[182]


nmUVLE

D(400

nm)air

sim2ndash25

RT70p

pb50

5ndash10min

Minutes

[183]

ZnO-SnO2


UVlight

(366

nm)air

39RT

25pp

msim2m

insim7m

in[180]

InGaZ

nOTh

infilmdsim65

nmtmdashna

UVLE

D(370

nm)air

14RT

2pp

m10min

gt30

min

[184]

TiO2


UVlight

(366

nm)air

64RT

25pp

msim1m

insim2m

in[180]


LED(460

nm)air

2RT

25pp

msim15

min

sim1m

in[185]

TiO2-SnO2


UVlight

(366

nm)air

327

RT25pp

msim3m

insim15s

[180]

Pt(TiO2-SnO2)(14)


UVlight

(366

nm)air

103

RT25pp

msim3m

insim1m

in[180]

WO3


mLE

D(460

nm)air

64RT

25pp

msim1m

insim1m

in[185]

TiO2-W

O3


mLE

D(460

nm)air

1400

RT25pp

msim3m

insim8m

in[185]

Pt(TiO2-W

O3)(14)


mLE

D(460

nm)air

2700

RT25pp

m15min

15min

[185]

dfilm

thickn

esstgrainsiz

eSsensor

respon

se(119877

ozon

e119877air)con

ditio

nsof

measurements

temperature

ofop

eration

gasc

oncentratio

nandairh

umidity








2O3can catalyt-


2surface is deacti-




2O3and










2O3minus119909



001 01 1 10

100

10

100

(a)

UV

16012080400Time (min)

Resp

onse

tim

e (m

in)

(b)

15ppb

200ppb

25ppm

22ppm

92ppm

In2O3


O3

50

40

30

20

10

0

Resis

tanc

e (kO

hm)



3-concentrations





2O3-





1

2


0 50 100 150 200 250 300 350


10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Con

duct

ivity

(Ωminus1

cmminus1)



0 50 100 150 200


103

104

105

106

107

Sens

or re

spon

seR

ozon

eR

air






2


24ppm ozone LED on

24ppm ozoneLED off

15 30 45 600

Time (min)

Resp

onse

[RR

0]

In2O3

24ppm ozoneLED off

50 100 1500

150

0

02

04

06

(k)

0

04 k

08 k

12 k

16 k









2O3









2films






2O3-





2O3and SnO








3+ (OO-H

+) + 2eminus


2uarr +H

2O uarr

(21)


2or HO



2at





2and In

2O3sensors


2sur-









Different OH-groups

100 200 300 400 5000Temperature (∘C)


Sens

or re

spon

se

100 200 300 400 500

Sens

or re

spon

se

300 400 500 600

Sens

itivi

ty to

air h

umid

ityTh

e rat

io S

(wet

)S(

dry)

SnO2

100

101

102

100

101

102

103

100

101

102

103

104




RH sim 45

RH sim 1-2

RH sim 45

RH sim 1-2





119887




2films deposited



Grain

Grain




diffusion

(a) (b)




119878sim 119881119878 where 119899





119878sim Δ119873

119878





119887sim Δ(MeO)

119904




Elsevier





layerBulk region

Interface region

Grains














119878



119901) in


119901sim 998779(MeO)

119887)


Δ119866 (119905)

= 119870119889(119905) Δ119866

1(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905)

(22)








119889(119905)



Δ119866 (119905) = 119870119889(119905) Δ119866 (23)





Δ119866 (119905) = Δ1198661(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905) (24)




2-





3(119905) could be


Δ1198663(119905) = 119870

119886119889(119905) Δ119866

119888(119905) (25)

1-2 RH

Resp

onse

tim

e (se

c)

100

101

102

103

In2O3

20 40 60 10010Grain size (nm)

120591 sim t2

















0 100 200 300 400Thickness (nm)

Activ

atio

n en

ergy

(eV

)

20

16

12

08

04

0

OzoneResponse

Recovery

Dry

Dry

Wet

Wet

1

2

3

E sim 15 eV

E sim 06 eV



119878


2O3and SnO

2surfaces





2O3 one













2O3surface





2O) in chemisorbed







2O3









1

2

34

5

6035 eV

055 eV

13

eV

100

101

102

103

Tim

e con

stant

s (se

c)


16 qkT (eVminus1)

18 20 22

Esim115

eV

(a)

1

2

34

5

Response

Recovery (wet air)

Dry airWet air

Wet02

8 eV

In2O3

18 20 22 24 26 28 30

400 300 200 150

qkT (eVminus1)

100

101

102

103

Tim

e con

stant

s (se

c)


E sim 033 eV

(b)











2O3sensor response











2based






0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV









Recovery time

Response time


0

100

200

300

Tim

e con

stant

(sec

)


2O3


100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2







8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










1

2

6

2

4

0


350 400 450 500 550300Wavelength (nm)

2

4

6

8

EL p

ower

at40

mA

(mW

)

Sens

or re

spon

seR

ozon

eR

air



3 Adapted








2- and In

2O3-based





2 For


50 200150 3000 100 350250

Time (min)

10minus5

10minus4

10minus3

10minus2

10minus1

100

101

102

Spec

con

duct

ivity

(Ωminus1

cmminus1)







2


ℎ] 997904rArr e119878

minus+ h119878

+ (17)

h119878

++O2119878

minus997904rArr O

2119878997904rArr O

2uarr (18)



119877dark119877UV

sim exp(119902ΔB119896119879

) (19)



Table5Ty

picalp

aram

eterso

fRTozon

esensorsop

erated

usingUVph

otoreductio

neffect

Metaloxide

Techno

logyfilm

parameters

UVsourcecon

ditio

nsof

photoreductio

nMax119878

Con

ditio

nsof

measurements

Respon

setim

eRe

covery

time

References

In2O3

Thin


tsim8ndash25

nmUVHglamp(254

nm)vacuum

sim105ndash106

RTsim

30ndash9

0ppb

na

na

[170171173174]

Thickfilm

(mesop

orou

s)dmdashnatsim30

nmUVLE

Dair(100∘C)

sim130ndash

350

PretreatmentRT

02ndash12

ppmdry

Minutes

25ndash53m

in[119175]

Thin

filmdmdashnatmdash

na

UVLE

D(375

nm)air(01P

a)sim4

RT25pp

msim10min

na

[169]

Thin

filmdsim20

nmtsim7n

mUVLE

D(375

nm)na

sim105

RT104p

pmMinutes

Minutes

[176]

Thin

filmdmdashnatsim7n

mUVLE

D(375

nm)air

sim5ndash12

RT03ndash1

ppm

Minutes

Minutes

[121163177]

SnO2

Thin

filmdsim450n

mtmdashna

UVLE

D(370

nm)air

13ndash14

RT10p

pm60

Minutes

Tens

ofminutes

[178]

Thin

filmdsim6ndash

9nmtmdashna

UVLE

D(385

nm)air

sim11

RT100

ppbdry

Tens

ofminutes

Tens

ofminutes

[179]


na

UVlight

(366

nm)air

26RT

25pp

msim50

min

sim4-5m

in[180]

PtSnO2


na

UVlight

(366

nm)air

885

RT25pp

msim6m

insim15

min

[180]

ZnO

Thin

filmdsim150ndash

1000

nmtsim5ndash11nm

UVHglamp(254

nm)vacuum

sim103ndash108

RTn

aTens

ofminutes

Minutes

[38181]

Thin


nmUVlamp(366

nm)air

UVlampair(580∘C)

sim12

sim103

RT25pp

m10min

1min

Minutes

5s(580∘C)

[182]


nmUVLE

D(400

nm)air

sim2ndash25

RT70p

pb50

5ndash10min

Minutes

[183]

ZnO-SnO2


UVlight

(366

nm)air

39RT

25pp

msim2m

insim7m

in[180]

InGaZ

nOTh

infilmdsim65

nmtmdashna

UVLE

D(370

nm)air

14RT

2pp

m10min

gt30

min

[184]

TiO2


UVlight

(366

nm)air

64RT

25pp

msim1m

insim2m

in[180]


LED(460

nm)air

2RT

25pp

msim15

min

sim1m

in[185]

TiO2-SnO2


UVlight

(366

nm)air

327

RT25pp

msim3m

insim15s

[180]

Pt(TiO2-SnO2)(14)


UVlight

(366

nm)air

103

RT25pp

msim3m

insim1m

in[180]

WO3


mLE

D(460

nm)air

64RT

25pp

msim1m

insim1m

in[185]

TiO2-W

O3


mLE

D(460

nm)air

1400

RT25pp

msim3m

insim8m

in[185]

Pt(TiO2-W

O3)(14)


mLE

D(460

nm)air

2700

RT25pp

m15min

15min

[185]

dfilm

thickn

esstgrainsiz

eSsensor

respon

se(119877

ozon

e119877air)con

ditio

nsof

measurements

temperature

ofop

eration

gasc

oncentratio

nandairh

umidity








2O3can catalyt-


2surface is deacti-




2O3and










2O3minus119909



001 01 1 10

100

10

100

(a)

UV

16012080400Time (min)

Resp

onse

tim

e (m

in)

(b)

15ppb

200ppb

25ppm

22ppm

92ppm

In2O3


O3

50

40

30

20

10

0

Resis

tanc

e (kO

hm)



3-concentrations





2O3-





1

2


0 50 100 150 200 250 300 350


10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Con

duct

ivity

(Ωminus1

cmminus1)



0 50 100 150 200


103

104

105

106

107

Sens

or re

spon

seR

ozon

eR

air






2


24ppm ozone LED on

24ppm ozoneLED off

15 30 45 600

Time (min)

Resp

onse

[RR

0]

In2O3

24ppm ozoneLED off

50 100 1500

150

0

02

04

06

(k)

0

04 k

08 k

12 k

16 k









2O3









2films






2O3-





2O3and SnO








3+ (OO-H

+) + 2eminus


2uarr +H

2O uarr

(21)


2or HO



2at





2and In

2O3sensors


2sur-









Different OH-groups

100 200 300 400 5000Temperature (∘C)


Sens

or re

spon

se

100 200 300 400 500

Sens

or re

spon

se

300 400 500 600

Sens

itivi

ty to

air h

umid

ityTh

e rat

io S

(wet

)S(

dry)

SnO2

100

101

102

100

101

102

103

100

101

102

103

104




RH sim 45

RH sim 1-2

RH sim 45

RH sim 1-2





119887




2films deposited



Grain

Grain




diffusion

(a) (b)




119878sim 119881119878 where 119899





119878sim Δ119873

119878





119887sim Δ(MeO)

119904




Elsevier





layerBulk region

Interface region

Grains














119878



119901) in


119901sim 998779(MeO)

119887)


Δ119866 (119905)

= 119870119889(119905) Δ119866

1(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905)

(22)








119889(119905)



Δ119866 (119905) = 119870119889(119905) Δ119866 (23)





Δ119866 (119905) = Δ1198661(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905) (24)




2-





3(119905) could be


Δ1198663(119905) = 119870

119886119889(119905) Δ119866

119888(119905) (25)

1-2 RH

Resp

onse

tim

e (se

c)

100

101

102

103

In2O3

20 40 60 10010Grain size (nm)

120591 sim t2

















0 100 200 300 400Thickness (nm)

Activ

atio

n en

ergy

(eV

)

20

16

12

08

04

0

OzoneResponse

Recovery

Dry

Dry

Wet

Wet

1

2

3

E sim 15 eV

E sim 06 eV



119878


2O3and SnO

2surfaces





2O3 one













2O3surface





2O) in chemisorbed







2O3









1

2

34

5

6035 eV

055 eV

13

eV

100

101

102

103

Tim

e con

stant

s (se

c)


16 qkT (eVminus1)

18 20 22

Esim115

eV

(a)

1

2

34

5

Response

Recovery (wet air)

Dry airWet air

Wet02

8 eV

In2O3

18 20 22 24 26 28 30

400 300 200 150

qkT (eVminus1)

100

101

102

103

Tim

e con

stant

s (se

c)


E sim 033 eV

(b)











2O3sensor response











2based






0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV









Recovery time

Response time


0

100

200

300

Tim

e con

stant

(sec

)


2O3


100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2







8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










Table5Ty

picalp

aram

eterso

fRTozon

esensorsop

erated

usingUVph

otoreductio

neffect

Metaloxide

Techno

logyfilm

parameters

UVsourcecon

ditio

nsof

photoreductio

nMax119878

Con

ditio

nsof

measurements

Respon

setim

eRe

covery

time

References

In2O3

Thin


tsim8ndash25

nmUVHglamp(254

nm)vacuum

sim105ndash106

RTsim

30ndash9

0ppb

na

na

[170171173174]

Thickfilm

(mesop

orou

s)dmdashnatsim30

nmUVLE

Dair(100∘C)

sim130ndash

350

PretreatmentRT

02ndash12

ppmdry

Minutes

25ndash53m

in[119175]

Thin

filmdmdashnatmdash

na

UVLE

D(375

nm)air(01P

a)sim4

RT25pp

msim10min

na

[169]

Thin

filmdsim20

nmtsim7n

mUVLE

D(375

nm)na

sim105

RT104p

pmMinutes

Minutes

[176]

Thin

filmdmdashnatsim7n

mUVLE

D(375

nm)air

sim5ndash12

RT03ndash1

ppm

Minutes

Minutes

[121163177]

SnO2

Thin

filmdsim450n

mtmdashna

UVLE

D(370

nm)air

13ndash14

RT10p

pm60

Minutes

Tens

ofminutes

[178]

Thin

filmdsim6ndash

9nmtmdashna

UVLE

D(385

nm)air

sim11

RT100

ppbdry

Tens

ofminutes

Tens

ofminutes

[179]


na

UVlight

(366

nm)air

26RT

25pp

msim50

min

sim4-5m

in[180]

PtSnO2


na

UVlight

(366

nm)air

885

RT25pp

msim6m

insim15

min

[180]

ZnO

Thin

filmdsim150ndash

1000

nmtsim5ndash11nm

UVHglamp(254

nm)vacuum

sim103ndash108

RTn

aTens

ofminutes

Minutes

[38181]

Thin


nmUVlamp(366

nm)air

UVlampair(580∘C)

sim12

sim103

RT25pp

m10min

1min

Minutes

5s(580∘C)

[182]


nmUVLE

D(400

nm)air

sim2ndash25

RT70p

pb50

5ndash10min

Minutes

[183]

ZnO-SnO2


UVlight

(366

nm)air

39RT

25pp

msim2m

insim7m

in[180]

InGaZ

nOTh

infilmdsim65

nmtmdashna

UVLE

D(370

nm)air

14RT

2pp

m10min

gt30

min

[184]

TiO2


UVlight

(366

nm)air

64RT

25pp

msim1m

insim2m

in[180]


LED(460

nm)air

2RT

25pp

msim15

min

sim1m

in[185]

TiO2-SnO2


UVlight

(366

nm)air

327

RT25pp

msim3m

insim15s

[180]

Pt(TiO2-SnO2)(14)


UVlight

(366

nm)air

103

RT25pp

msim3m

insim1m

in[180]

WO3


mLE

D(460

nm)air

64RT

25pp

msim1m

insim1m

in[185]

TiO2-W

O3


mLE

D(460

nm)air

1400

RT25pp

msim3m

insim8m

in[185]

Pt(TiO2-W

O3)(14)


mLE

D(460

nm)air

2700

RT25pp

m15min

15min

[185]

dfilm

thickn

esstgrainsiz

eSsensor

respon

se(119877

ozon

e119877air)con

ditio

nsof

measurements

temperature

ofop

eration

gasc

oncentratio

nandairh

umidity








2O3can catalyt-


2surface is deacti-




2O3and










2O3minus119909



001 01 1 10

100

10

100

(a)

UV

16012080400Time (min)

Resp

onse

tim

e (m

in)

(b)

15ppb

200ppb

25ppm

22ppm

92ppm

In2O3


O3

50

40

30

20

10

0

Resis

tanc

e (kO

hm)



3-concentrations





2O3-





1

2


0 50 100 150 200 250 300 350


10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Con

duct

ivity

(Ωminus1

cmminus1)



0 50 100 150 200


103

104

105

106

107

Sens

or re

spon

seR

ozon

eR

air






2


24ppm ozone LED on

24ppm ozoneLED off

15 30 45 600

Time (min)

Resp

onse

[RR

0]

In2O3

24ppm ozoneLED off

50 100 1500

150

0

02

04

06

(k)

0

04 k

08 k

12 k

16 k









2O3









2films






2O3-





2O3and SnO








3+ (OO-H

+) + 2eminus


2uarr +H

2O uarr

(21)


2or HO



2at





2and In

2O3sensors


2sur-









Different OH-groups

100 200 300 400 5000Temperature (∘C)


Sens

or re

spon

se

100 200 300 400 500

Sens

or re

spon

se

300 400 500 600

Sens

itivi

ty to

air h

umid

ityTh

e rat

io S

(wet

)S(

dry)

SnO2

100

101

102

100

101

102

103

100

101

102

103

104




RH sim 45

RH sim 1-2

RH sim 45

RH sim 1-2





119887




2films deposited



Grain

Grain




diffusion

(a) (b)




119878sim 119881119878 where 119899





119878sim Δ119873

119878





119887sim Δ(MeO)

119904




Elsevier





layerBulk region

Interface region

Grains














119878



119901) in


119901sim 998779(MeO)

119887)


Δ119866 (119905)

= 119870119889(119905) Δ119866

1(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905)

(22)








119889(119905)



Δ119866 (119905) = 119870119889(119905) Δ119866 (23)





Δ119866 (119905) = Δ1198661(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905) (24)




2-





3(119905) could be


Δ1198663(119905) = 119870

119886119889(119905) Δ119866

119888(119905) (25)

1-2 RH

Resp

onse

tim

e (se

c)

100

101

102

103

In2O3

20 40 60 10010Grain size (nm)

120591 sim t2

















0 100 200 300 400Thickness (nm)

Activ

atio

n en

ergy

(eV

)

20

16

12

08

04

0

OzoneResponse

Recovery

Dry

Dry

Wet

Wet

1

2

3

E sim 15 eV

E sim 06 eV



119878


2O3and SnO

2surfaces





2O3 one













2O3surface





2O) in chemisorbed







2O3









1

2

34

5

6035 eV

055 eV

13

eV

100

101

102

103

Tim

e con

stant

s (se

c)


16 qkT (eVminus1)

18 20 22

Esim115

eV

(a)

1

2

34

5

Response

Recovery (wet air)

Dry airWet air

Wet02

8 eV

In2O3

18 20 22 24 26 28 30

400 300 200 150

qkT (eVminus1)

100

101

102

103

Tim

e con

stant

s (se

c)


E sim 033 eV

(b)











2O3sensor response











2based






0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV









Recovery time

Response time


0

100

200

300

Tim

e con

stant

(sec

)


2O3


100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2







8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation
















2O3can catalyt-


2surface is deacti-




2O3and










2O3minus119909



001 01 1 10

100

10

100

(a)

UV

16012080400Time (min)

Resp

onse

tim

e (m

in)

(b)

15ppb

200ppb

25ppm

22ppm

92ppm

In2O3


O3

50

40

30

20

10

0

Resis

tanc

e (kO

hm)



3-concentrations





2O3-





1

2


0 50 100 150 200 250 300 350


10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Con

duct

ivity

(Ωminus1

cmminus1)



0 50 100 150 200


103

104

105

106

107

Sens

or re

spon

seR

ozon

eR

air






2


24ppm ozone LED on

24ppm ozoneLED off

15 30 45 600

Time (min)

Resp

onse

[RR

0]

In2O3

24ppm ozoneLED off

50 100 1500

150

0

02

04

06

(k)

0

04 k

08 k

12 k

16 k









2O3









2films






2O3-





2O3and SnO








3+ (OO-H

+) + 2eminus


2uarr +H

2O uarr

(21)


2or HO



2at





2and In

2O3sensors


2sur-









Different OH-groups

100 200 300 400 5000Temperature (∘C)


Sens

or re

spon

se

100 200 300 400 500

Sens

or re

spon

se

300 400 500 600

Sens

itivi

ty to

air h

umid

ityTh

e rat

io S

(wet

)S(

dry)

SnO2

100

101

102

100

101

102

103

100

101

102

103

104




RH sim 45

RH sim 1-2

RH sim 45

RH sim 1-2





119887




2films deposited



Grain

Grain




diffusion

(a) (b)




119878sim 119881119878 where 119899





119878sim Δ119873

119878





119887sim Δ(MeO)

119904




Elsevier





layerBulk region

Interface region

Grains














119878



119901) in


119901sim 998779(MeO)

119887)


Δ119866 (119905)

= 119870119889(119905) Δ119866

1(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905)

(22)








119889(119905)



Δ119866 (119905) = 119870119889(119905) Δ119866 (23)





Δ119866 (119905) = Δ1198661(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905) (24)




2-





3(119905) could be


Δ1198663(119905) = 119870

119886119889(119905) Δ119866

119888(119905) (25)

1-2 RH

Resp

onse

tim

e (se

c)

100

101

102

103

In2O3

20 40 60 10010Grain size (nm)

120591 sim t2

















0 100 200 300 400Thickness (nm)

Activ

atio

n en

ergy

(eV

)

20

16

12

08

04

0

OzoneResponse

Recovery

Dry

Dry

Wet

Wet

1

2

3

E sim 15 eV

E sim 06 eV



119878


2O3and SnO

2surfaces





2O3 one













2O3surface





2O) in chemisorbed







2O3









1

2

34

5

6035 eV

055 eV

13

eV

100

101

102

103

Tim

e con

stant

s (se

c)


16 qkT (eVminus1)

18 20 22

Esim115

eV

(a)

1

2

34

5

Response

Recovery (wet air)

Dry airWet air

Wet02

8 eV

In2O3

18 20 22 24 26 28 30

400 300 200 150

qkT (eVminus1)

100

101

102

103

Tim

e con

stant

s (se

c)


E sim 033 eV

(b)











2O3sensor response











2based






0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV









Recovery time

Response time


0

100

200

300

Tim

e con

stant

(sec

)


2O3


100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2







8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











1

2


0 50 100 150 200 250 300 350


10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

Con

duct

ivity

(Ωminus1

cmminus1)



0 50 100 150 200


103

104

105

106

107

Sens

or re

spon

seR

ozon

eR

air






2


24ppm ozone LED on

24ppm ozoneLED off

15 30 45 600

Time (min)

Resp

onse

[RR

0]

In2O3

24ppm ozoneLED off

50 100 1500

150

0

02

04

06

(k)

0

04 k

08 k

12 k

16 k









2O3









2films






2O3-





2O3and SnO








3+ (OO-H

+) + 2eminus


2uarr +H

2O uarr

(21)


2or HO



2at





2and In

2O3sensors


2sur-









Different OH-groups

100 200 300 400 5000Temperature (∘C)


Sens

or re

spon

se

100 200 300 400 500

Sens

or re

spon

se

300 400 500 600

Sens

itivi

ty to

air h

umid

ityTh

e rat

io S

(wet

)S(

dry)

SnO2

100

101

102

100

101

102

103

100

101

102

103

104




RH sim 45

RH sim 1-2

RH sim 45

RH sim 1-2





119887




2films deposited



Grain

Grain




diffusion

(a) (b)




119878sim 119881119878 where 119899





119878sim Δ119873

119878





119887sim Δ(MeO)

119904




Elsevier





layerBulk region

Interface region

Grains














119878



119901) in


119901sim 998779(MeO)

119887)


Δ119866 (119905)

= 119870119889(119905) Δ119866

1(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905)

(22)








119889(119905)



Δ119866 (119905) = 119870119889(119905) Δ119866 (23)





Δ119866 (119905) = Δ1198661(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905) (24)




2-





3(119905) could be


Δ1198663(119905) = 119870

119886119889(119905) Δ119866

119888(119905) (25)

1-2 RH

Resp

onse

tim

e (se

c)

100

101

102

103

In2O3

20 40 60 10010Grain size (nm)

120591 sim t2

















0 100 200 300 400Thickness (nm)

Activ

atio

n en

ergy

(eV

)

20

16

12

08

04

0

OzoneResponse

Recovery

Dry

Dry

Wet

Wet

1

2

3

E sim 15 eV

E sim 06 eV



119878


2O3and SnO

2surfaces





2O3 one













2O3surface





2O) in chemisorbed







2O3









1

2

34

5

6035 eV

055 eV

13

eV

100

101

102

103

Tim

e con

stant

s (se

c)


16 qkT (eVminus1)

18 20 22

Esim115

eV

(a)

1

2

34

5

Response

Recovery (wet air)

Dry airWet air

Wet02

8 eV

In2O3

18 20 22 24 26 28 30

400 300 200 150

qkT (eVminus1)

100

101

102

103

Tim

e con

stant

s (se

c)


E sim 033 eV

(b)











2O3sensor response











2based






0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV









Recovery time

Response time


0

100

200

300

Tim

e con

stant

(sec

)


2O3


100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2







8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation













2films






2O3-





2O3and SnO








3+ (OO-H

+) + 2eminus


2uarr +H

2O uarr

(21)


2or HO



2at





2and In

2O3sensors


2sur-









Different OH-groups

100 200 300 400 5000Temperature (∘C)


Sens

or re

spon

se

100 200 300 400 500

Sens

or re

spon

se

300 400 500 600

Sens

itivi

ty to

air h

umid

ityTh

e rat

io S

(wet

)S(

dry)

SnO2

100

101

102

100

101

102

103

100

101

102

103

104




RH sim 45

RH sim 1-2

RH sim 45

RH sim 1-2





119887




2films deposited



Grain

Grain




diffusion

(a) (b)




119878sim 119881119878 where 119899





119878sim Δ119873

119878





119887sim Δ(MeO)

119904




Elsevier





layerBulk region

Interface region

Grains














119878



119901) in


119901sim 998779(MeO)

119887)


Δ119866 (119905)

= 119870119889(119905) Δ119866

1(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905)

(22)








119889(119905)



Δ119866 (119905) = 119870119889(119905) Δ119866 (23)





Δ119866 (119905) = Δ1198661(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905) (24)




2-





3(119905) could be


Δ1198663(119905) = 119870

119886119889(119905) Δ119866

119888(119905) (25)

1-2 RH

Resp

onse

tim

e (se

c)

100

101

102

103

In2O3

20 40 60 10010Grain size (nm)

120591 sim t2

















0 100 200 300 400Thickness (nm)

Activ

atio

n en

ergy

(eV

)

20

16

12

08

04

0

OzoneResponse

Recovery

Dry

Dry

Wet

Wet

1

2

3

E sim 15 eV

E sim 06 eV



119878


2O3and SnO

2surfaces





2O3 one













2O3surface





2O) in chemisorbed







2O3









1

2

34

5

6035 eV

055 eV

13

eV

100

101

102

103

Tim

e con

stant

s (se

c)


16 qkT (eVminus1)

18 20 22

Esim115

eV

(a)

1

2

34

5

Response

Recovery (wet air)

Dry airWet air

Wet02

8 eV

In2O3

18 20 22 24 26 28 30

400 300 200 150

qkT (eVminus1)

100

101

102

103

Tim

e con

stant

s (se

c)


E sim 033 eV

(b)











2O3sensor response











2based






0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV









Recovery time

Response time


0

100

200

300

Tim

e con

stant

(sec

)


2O3


100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2







8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation













Different OH-groups

100 200 300 400 5000Temperature (∘C)


Sens

or re

spon

se

100 200 300 400 500

Sens

or re

spon

se

300 400 500 600

Sens

itivi

ty to

air h

umid

ityTh

e rat

io S

(wet

)S(

dry)

SnO2

100

101

102

100

101

102

103

100

101

102

103

104




RH sim 45

RH sim 1-2

RH sim 45

RH sim 1-2





119887




2films deposited



Grain

Grain




diffusion

(a) (b)




119878sim 119881119878 where 119899





119878sim Δ119873

119878





119887sim Δ(MeO)

119904




Elsevier





layerBulk region

Interface region

Grains














119878



119901) in


119901sim 998779(MeO)

119887)


Δ119866 (119905)

= 119870119889(119905) Δ119866

1(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905)

(22)








119889(119905)



Δ119866 (119905) = 119870119889(119905) Δ119866 (23)





Δ119866 (119905) = Δ1198661(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905) (24)




2-





3(119905) could be


Δ1198663(119905) = 119870

119886119889(119905) Δ119866

119888(119905) (25)

1-2 RH

Resp

onse

tim

e (se

c)

100

101

102

103

In2O3

20 40 60 10010Grain size (nm)

120591 sim t2

















0 100 200 300 400Thickness (nm)

Activ

atio

n en

ergy

(eV

)

20

16

12

08

04

0

OzoneResponse

Recovery

Dry

Dry

Wet

Wet

1

2

3

E sim 15 eV

E sim 06 eV



119878


2O3and SnO

2surfaces





2O3 one













2O3surface





2O) in chemisorbed







2O3









1

2

34

5

6035 eV

055 eV

13

eV

100

101

102

103

Tim

e con

stant

s (se

c)


16 qkT (eVminus1)

18 20 22

Esim115

eV

(a)

1

2

34

5

Response

Recovery (wet air)

Dry airWet air

Wet02

8 eV

In2O3

18 20 22 24 26 28 30

400 300 200 150

qkT (eVminus1)

100

101

102

103

Tim

e con

stant

s (se

c)


E sim 033 eV

(b)











2O3sensor response











2based






0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV









Recovery time

Response time


0

100

200

300

Tim

e con

stant

(sec

)


2O3


100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2







8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation












Elsevier





layerBulk region

Interface region

Grains














119878



119901) in


119901sim 998779(MeO)

119887)


Δ119866 (119905)

= 119870119889(119905) Δ119866

1(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905)

(22)








119889(119905)



Δ119866 (119905) = 119870119889(119905) Δ119866 (23)





Δ119866 (119905) = Δ1198661(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905) (24)




2-





3(119905) could be


Δ1198663(119905) = 119870

119886119889(119905) Δ119866

119888(119905) (25)

1-2 RH

Resp

onse

tim

e (se

c)

100

101

102

103

In2O3

20 40 60 10010Grain size (nm)

120591 sim t2

















0 100 200 300 400Thickness (nm)

Activ

atio

n en

ergy

(eV

)

20

16

12

08

04

0

OzoneResponse

Recovery

Dry

Dry

Wet

Wet

1

2

3

E sim 15 eV

E sim 06 eV



119878


2O3and SnO

2surfaces





2O3 one













2O3surface





2O) in chemisorbed







2O3









1

2

34

5

6035 eV

055 eV

13

eV

100

101

102

103

Tim

e con

stant

s (se

c)


16 qkT (eVminus1)

18 20 22

Esim115

eV

(a)

1

2

34

5

Response

Recovery (wet air)

Dry airWet air

Wet02

8 eV

In2O3

18 20 22 24 26 28 30

400 300 200 150

qkT (eVminus1)

100

101

102

103

Tim

e con

stant

s (se

c)


E sim 033 eV

(b)











2O3sensor response











2based






0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV









Recovery time

Response time


0

100

200

300

Tim

e con

stant

(sec

)


2O3


100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2







8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation












Δ119866 (119905) = Δ1198661(119905) + Δ119866

2(119905) + Δ119866

3(119905) + Δ119866

4(119905) (24)




2-





3(119905) could be


Δ1198663(119905) = 119870

119886119889(119905) Δ119866

119888(119905) (25)

1-2 RH

Resp

onse

tim

e (se

c)

100

101

102

103

In2O3

20 40 60 10010Grain size (nm)

120591 sim t2

















0 100 200 300 400Thickness (nm)

Activ

atio

n en

ergy

(eV

)

20

16

12

08

04

0

OzoneResponse

Recovery

Dry

Dry

Wet

Wet

1

2

3

E sim 15 eV

E sim 06 eV



119878


2O3and SnO

2surfaces





2O3 one













2O3surface





2O) in chemisorbed







2O3









1

2

34

5

6035 eV

055 eV

13

eV

100

101

102

103

Tim

e con

stant

s (se

c)


16 qkT (eVminus1)

18 20 22

Esim115

eV

(a)

1

2

34

5

Response

Recovery (wet air)

Dry airWet air

Wet02

8 eV

In2O3

18 20 22 24 26 28 30

400 300 200 150

qkT (eVminus1)

100

101

102

103

Tim

e con

stant

s (se

c)


E sim 033 eV

(b)











2O3sensor response











2based






0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV









Recovery time

Response time


0

100

200

300

Tim

e con

stant

(sec

)


2O3


100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2







8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










0 100 200 300 400Thickness (nm)

Activ

atio

n en

ergy

(eV

)

20

16

12

08

04

0

OzoneResponse

Recovery

Dry

Dry

Wet

Wet

1

2

3

E sim 15 eV

E sim 06 eV



119878


2O3and SnO

2surfaces





2O3 one













2O3surface





2O) in chemisorbed







2O3









1

2

34

5

6035 eV

055 eV

13

eV

100

101

102

103

Tim

e con

stant

s (se

c)


16 qkT (eVminus1)

18 20 22

Esim115

eV

(a)

1

2

34

5

Response

Recovery (wet air)

Dry airWet air

Wet02

8 eV

In2O3

18 20 22 24 26 28 30

400 300 200 150

qkT (eVminus1)

100

101

102

103

Tim

e con

stant

s (se

c)


E sim 033 eV

(b)











2O3sensor response











2based






0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV









Recovery time

Response time


0

100

200

300

Tim

e con

stant

(sec

)


2O3


100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2







8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










1

2

34

5

6035 eV

055 eV

13

eV

100

101

102

103

Tim

e con

stant

s (se

c)


16 qkT (eVminus1)

18 20 22

Esim115

eV

(a)

1

2

34

5

Response

Recovery (wet air)

Dry airWet air

Wet02

8 eV

In2O3

18 20 22 24 26 28 30

400 300 200 150

qkT (eVminus1)

100

101

102

103

Tim

e con

stant

s (se

c)


E sim 033 eV

(b)











2O3sensor response











2based






0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV









Recovery time

Response time


0

100

200

300

Tim

e con

stant

(sec

)


2O3


100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2







8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










0 100 200 300 400

Sens

or re

spon

se (a

u)

1

025ndash04 eV

06ndash075 eV

gt11 eV









Recovery time

Response time


0

100

200

300

Tim

e con

stant

(sec

)


2O3


100

1 10 100 1000

80

60

0

40

20

Resp

onse

ΔR

R(

)

120582 = 320ndash400nm

120582 = 415nm

SnO2







8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











8 Conclusions


2and In



2- and In






2and In



2and In

2O3



2and In



2



2O3films with dif-




2and In

2O3can improve the


Competing Interests


Acknowledgments


References










































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation































2O3-In2O3








3)



3based









2O3films










2O3ZnOSnO

2thin




28 no 3 pp 483ndash487 2012




















2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation




























2low temperature







2-Au nanocom-









3

















3 TiO

2and WO







23thin









2O3and





2O3-based







2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation














2














2WO4



























2- and








2 In2O3 ZnO and WO

3case studiesrdquo




4∙5H2O




2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











2O3-



2films











2O3and MoO








































2




















2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation























2thin filmsrdquo in











































3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation













3



2ndashSnO

2material







3





















2and O



















































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation





































RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









Review Article O -andSnO -Based Thin Film Ozone...

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Transcript of Review Article O -andSnO -Based Thin Film Ozone...