PHY605 notes Semiconductor Materials.docx

8/18/2019 PHY605 notes Semiconductor Materials.docx

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MATERIALS,SEMICONDUCTOR MATERIALS,and MICROELECTRONICS

Materials science..

..is primarily concerned with the search of basic knowledge about the internalstructure, properties, and processing of materials.

Materials engineering..

..is mainly concerned with the use of fundamental and applied knowledge of

materials so that the materials can be converted into products needed or desired by

society.

Materials science and engineering..

..combines both materials science and materials engineering.

Types of aterials

Most engineering materials are divided into three main or fundamental classes;

Metallic materials

Polymeric materials

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Ceramic materials

Additional application classes;

Composite materials

Electronic materials

Metallic materials..

..metals and metal alloys! are inorganic materials that are characteri"ed by high

thermal and electrical conductivities. E#amples are iron, steel, aluminum, copper.

Polymeric materials..

..are materials consisting of long molecular chains or network of low weight elements

such as carbon, hydrogen, o#ygen, and nitrogen. Most polymeric materials have low

electrical conductivities. E#amples are polyethylene, polyvinyl chloride pvc!.

Ceramic materials..

..are materials consisting of compounds of metals and nonmetals. Ceramic materials

are usually hard and brittle. E#amples are clay products, glass, and pure aluminum

o#ide that has been compacted and densified.

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Composite materials..

.. are materials that are mi#tures of two or more materials. E#amples are fiberglass

reinforcing material in a polyester or epo#y matri#.

Electronic materials..

..are materials used in electronics especially microelectronics. E#amples are silicon,

gallium arsenide.

Nanomaterials..

..are materials with a characteristic length scale smaller than $%% nm.

Assignent !

Consider a lig"t#$l#.

%a& Identify 'ario$s critical coponents of a lig"t#$l#.

%#& Deterine t"e aterial selected for eac" critical coponent.

%c& Rationali(e )"y t"e aterial )as selected for eac" coponent.

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Seicond$ctor aterials..

..are nearly perfect crystalline solids with small amount of iperfections, such as

impurity atoms, lattice vacancies, or dislocations, which are sometimes intentionally

introduced to alter their electrical characteristics

A summary of the chemical elements involved in the formation of semiconductors.

&he semiconductors can be eleental, such as Si, *e, and other chemical

elements from gro$p I+.

&hey can be also copo$nd, a combination between elements from gro$p III and

gro$p +, or respectively, fro gro$p II and gro$p +I.

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E#amples for such combinations are the binary compounds *aAs and nS.

&here are also several combinations of practical importance, which involve two or

more elements from the same chemical group.

'uch alloy seicond$ctors can be #inary e.g. 'i(e !, ternary e.g. Al(aAs !,

-$aternary e.g. )n(aAsP!, and even pentanary (a)nP'bAs! materials.

Electronic aterials include insulators, semiconductors, conductors, andsuperconductors.

&his family of materials has truly revolutionali"ed the world. *rom spark plugs made

from alumina, and copper wires for electrical transmission to components for

wireless communications, high powered magnets used in magnetic resonance

imaging, capacitors, inductors, solar cells, active matri# displays, silicon, and gallium

arsenide based computer chips, electronic materials are found in countless numbers

of applications.

+ew advances in the materials sciences have led to several breakthroughs in the

developement of new electronic materials. e now have ceramics that are not -ust

e#cellent insulators, but also semiconductors and superconductors. 'imilarly, we

now have polymers that are semiconductive and, more recently, a superconductive

polymer has also been discovered.

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©2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™ is a trademark sed herein nder lic

Classification of technologically useful electronic materials.

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y alloying multiple compounds, some semiconductor materials are t$na#le, e.g., in

band gap or lattice constant.

&he result is ternary, /uaternary, or even /uinary compositions.

Band gap..

&ernary compositions allow ad-usting the band gap within the range of the involved

binary compounds; however, in case of combination of direct and indirect band gap

materials there is a ratio where indirect band gap prevails, limiting the range usable

for optoelectronics; e.g. Al(aAs 0E1s are limited to 22% nm by this.

Lattice constant..

0attice constants of the compounds also tend to be different, and the lattice

mismatch against the substrate, dependent on the mi#ing ratio, causes defects in

amounts dependent on the mismatch magnitude; this influences the ratio of

achievable radiative3nonradiative recombinations and determines the luminous

efficiency of the device.

Band gap and lattice constant..

4uaternary and higher compositions allow ad-usting simultaneously the band gap

and the lattice constant, allowing increasing radiant efficiency at wider range of

wavelengths; for e#ample Al(a)nP is used for 0E1s .

Materials transparent to the generated wavelength of light are advantageous, as this

allows more efficient e#traction of photons from the bulk of the material. &hat is, in

such transparent materials, light production is not limited to -ust the surface.

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Silicon %Si& and *erani$ %*e&

)n solid state electronics, either pure silicon or germanium may be used as the

intrinsic semiconductor which forms the starting point for fabrication. Each has four

valence electrons, but germanium will at a given temperature have more free

electrons and a higher conductivity.

Silicon is by far the more widely used semiconductor for electronics, partly because

it can be used at much higher temperatures than germanium.

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http://hyperphysics.phy-astr.gsu.edu/hbase/solids/sili.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/solids/intrin.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/solids/sili.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/solids/sili.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/solids/intrin.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/solids/sili.html


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Si vs *aAs

Compound semiconductors have both advantages and disadvantages.

*or e#ample, galli$ arsenide (aAs! has si# times higher electron mobility thansilicon, which allows faster operation; wider band gap, which allows operation of

power devices at higher temperatures, and gives lower thermal noise to low power

devices at room temperature.

1irect band gap gives compound semiconductors more favorable optoelectronic

properties than the indirect band gap of silicon; it can be alloyed to ternary and

/uaternary compositions, with ad-ustable band gap width, allowing light emission at

chosen wavelengths, and allowing e.g. matching to wavelengths with lowest losses

in optical fibers.

(aAs can be also grown in a semi5insulating form, which is suitable as a lattice5

matching insulating substrate for (aAs devices.

Conversely..

Silicon is robust, cheap, and easy to process.

whereas..

*aAs is brittle and e#pensive, and insulation layers cannot be created by -ust

growing an o#ide layer; (aAs is therefore used only where silicon is not sufficient.

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Silicon %Si& vs Silicon Car#ide %SiC&

'iC devices belong to the so5called wide band gap semiconductor group,

hen compared to commonly used silicon 'i!, 'iC offers a number of attractivecharacteristics for high voltage power semiconductors.

Much higher breakdown field strength

Much higher thermal conductivity

thus allow creating devices which outperform by far the corresponding 'i ones, and

enable reaching otherwise unattainable efficiency levels.

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Indi$ Arsenide %InAs&

http://www.azom.com/article.aspx?ArticleI!"#$$

Description

)ndium arsenide is a semiconductor material made of arsenic and indi$.

&he semiconductor has a melting point of 678 9C and appears in the form of grey

crystals with a cubic structure.

)t is very similar to gallium arsenide and is a material having a direct bandgap.

)ndium arsenide is popular for its narrow energy bandgap and high electron mobility.

Applications

&he applications of indium arsenide are listed below:

)ndium arsenide is used to construct infrared detectors for a wavelength range

of $ ?m. &he detectors are normally photovoltaic photodiodes.

1etectors that are cryogenically cooled have low noise but )nAs detectors can

be used in high5power applications at room temperature also.

1iode lasers are also made using indium arsenide.

)ndium arsenide and gallium arsenide are similar and it is a direct bandgap

material.

)t is used as a terahert" radiation source.

)t is possible to form /uantum dots in a monolayer of indium arsenide on

gallium arsenide or indium phosphide

)t is also possible to form /uantum dots in indium gallium arsenide in the form

of indium arsenide dots arranged in the gallium arsenide matri#.

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Toicity of indi$ arsenide, galli$ arsenide, and al$ini$ galli$ arsenide.ana!a ".%ource: #epartment o$ %ygiene& 'ra()ate *c+ool o$ Me(ical *ciences& ,y)s+) -niersity& %igas+i/!)& )!)o!a 812/8582& apan. atana!aeisei.me(.!y)s+)/).ac.p

(allium arsenide (aAs!, indium arsenide )nAs!, and aluminium gallium arsenideAl(aAs! are semiconductor applications. Although the increased use of these

materials has raised concerns about occupational e#posure to them, there is little

information regarding the adverse health effects to workers arising from e#posure to

these particles. @owever, available data indicate these semiconductor materials can

be to#ic in animals.

Although acute and chronic to#icity of the lung, reproductive organs, and kidney are

associated with e#posure to these semiconductor materials, in particular, chronic

to#icity should pay much attention owing to low solubility of these materials.

etween )nAs, (aAs, and Al(aAs, InAs was the most to#ic material to the lung

followed by (aAs and Al(aAs when given intra5tracheally. &his was probably due to

difference in the to#icity of the counter5element of arsenic in semiconductor

materials, such as indium, gallium, or aluminium, and not arsenic itself. )t appeared

that indium, gallium, or aluminium was to#ic when released from the particles,

though the physical character of the particles also contributes to to#ic effect.

Although there is no evidence of the carcinogenicity of )nAs or Al(aAs, (aAs and

)nP, which are semiconductor materials, showed the clear evidence of carcinogenic

potential. )t is necessary to pay much greater attention to the human e#posure of

semiconductor materials.

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http://www.ncbi.nlm.nih.gov/pubmed?term=Tanaka%20A%5BAuthor%5D&cauthor=true&cauthor_uid=15276420http://www.ncbi.nlm.nih.gov/pubmed?term=Tanaka%20A%5BAuthor%5D&cauthor=true&cauthor_uid=15276420


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Direct and Indirect /andgap Seicond$ctor

)n a direct #andgap semiconductor, an electron can be promoted from the

conduction band to the valence band without changing the momentum of theelectron. An e#ample of a direct bandgap semiconductor is (aAs. hen the e#ited

falls back into the valence band, electrons and holes combine to produce light.

&hus, electron 0 "ole hν

&his is known as radiati'e reco#ination. &hus, direct bandgap materials such as

(aAs and solid solutions of these e.g. (aAs5AlAs! are used to make light5emitting

diodes 0E1s! of different colours. &he bandgap of semiconductors can be tuned

using solid solutions. &he change in bandgap produces a change in the wavelength

i.e. the fre/uency of the colour ν) is related to the bandgap E gas E g = hν, where h is

the Planks constant!. 'ince an optical effect is obtained using an electronic material,

often the direct bandgap materials are known as optoelectronic materials. Many

lasers and 0E1s have been developed using these materials. 0E1s that emit light in

the infrared range are used in optical5fiber communication systems to convert light

waves into electrical pulses. 1ifferent coloured lasers, such as the newest blue laser

using (a+, have been developed using direct bandgap materials.

)n an indirect #andgap semiconductor e.g. 'i, (e, (aP! the electron5hole

recombination is very efficient and the electrons cannot be promoted to the valence

band without a change in momentum. As a result, in materials that have an indirect

bandgap, we cannot get light emission. )nstead, electrons and holes combine to

produce heat that is dissipated within the material. &hus, electron 0 "ole "eat.

&his is known as non1radiati'e reco#ination.

+ote that both direct and indirect bandgap materials can be doped to form n5type or

p5type semiconductors.

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Organic Lig"t Eitting Diode %OLED&

B0E1 Brganic 0ight Emitting 1iodes! is a flat light emitting technology, made by

placing a series of organic thin films between two conductors. hen electrical

current is applied, a bright light is emitted. B0E1s can be used to make displays and

lighting. ecause B0E1s emit light they do not re/uire a backlight and so are thinner

and more efficient than 0C1 displays which do re/uire a white backlight!.

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OLED 's LCD

OLED displays "a'e t"e follo)ing ad'antages o'er LCD displays2

0ower power consumption

*aster refresh rate and better contrast

(reater brightness 5 &he screens are brighter, and have a fuller viewing

angle

E#citing displays 5 new types of displays, that we do not have today,

like ultra5thin, fle#ible or transparent displays

etter durability 5 B0E1s are very durable and can operate in a

broader temperature range

0ighter weight 5 the screen can be made very thin, and can even be

printed on fle#ible surfaces

3lei#le and transparent OLED displays

)t turns out that because B0E1s are thin and simple 5 they can be used to create

fle#ible and even transparent displays.

&his is pretty e#citing as it opens up a whole world of possibilities: Curved B0E1 displays, placed on non5flat surfaces

earable B0E1s

&ransparent B0E1s embedded in windows

B0E1s in car windshields

+ew designs for lamps

And many more we cannot even imagine today...

B0E1 video

+ttps::.yo)t)e.com:atc+;y?9(*00

4+ideo %5yo$t$#e&1/enda#le sartp"onehttp:33ceramics.org3ceramic5tech5today3video5new5smartphone5prototype5bends5to5

meet5consumers5needs

1t"e 'erge

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https://www.youtube.com/watch?v=QqyW9vdS0x0https://www.youtube.com/watch?v=QqyW9vdS0x0


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4uantum dot

A /uantum dot is a seicond$ctor nanostr$ct$re that confines t"e otion of

conduction band electrons, valence band holes, or e#citons bound pairs of

conduction band electrons and valence band holes! in all three spatial directions.

&he confinement can be due to..

5 electrostatic potentials generated by e#ternal electrodes, doping, strain,

impurities!

5 the presence of an interface between different semiconductor materials

e.g. in core5shell nanocrystal systems!

5 the presence of the semiconductor surface e.g. semiconductor

nanocrystal!

5 ..or a combination of these.

A /uantum dot has a discrete -$anti(ed energy spectr$.

&he corresponding wave functions are spatially locali"ed within the /uantum dot, but

e#tend over many periods of the crystal lattice.

A /uantum dot contains a small finite number of the order of $5$%%! of conduction

band electrons, valence band holes, or e#citons, i.e., a finite n$#er of eleentary

electric c"arges.

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'mall /uantum dots, such as colloidal semiconductor nanocrystals, can be as small

as 8 to $% nm, corresponding to $% to D% atoms in diameter and a total of $%% to

$%%,%%% atoms within the /uantum dot volume. 'elf5assembled /uantum dots are

typically between $% and D% nm in si"e.

4uantum dots defined by lithographically patterned gate electrodes, or by etching on

two5dimensional electron gases in semiconductor heterostructures can have lateral

dimensions e#ceeding $%% nm.

At $% nm in diameter, nearly = million /uantum dots could be lined up end to end and

fit within the width of a human thumb.

Note6 &he above te#t is e#cerpted from the ikipedia article 4uantum dot, which has been

released under the(+F *ree 1ocumentation 0icense.

Online so$rce 61

1 7$ant$ dot slides 5 http:33www.slideshare.net3mcleang$3/uantum5dots

7$ant$ dots article 61

http:33nanotechweb.org3cws3article3yournews3=GDD%

http:33nanotechweb.org3cws3article3tech37G2D=

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http://en.wikipedia.org/wiki/Quantum_dothttp://www.gnu.org/copyleft/fdl.htmlhttp://www.gnu.org/copyleft/fdl.htmlhttp://www.slideshare.net/mcleang1/quantum-dotshttp://nanotechweb.org/cws/article/yournews/37550http://nanotechweb.org/cws/article/tech/47653http://en.wikipedia.org/wiki/Quantum_dothttp://www.gnu.org/copyleft/fdl.htmlhttp://www.slideshare.net/mcleang1/quantum-dotshttp://nanotechweb.org/cws/article/yournews/37550http://nanotechweb.org/cws/article/tech/47653


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Silicon Car#ide Sc"ott8y Diodes

&he differences in material properties between 'iC and silicon limit the fabrication of

practical silicon unipolar diodes 'chottky diodes! to a range up to $%%H < $D%H, with

relatively high on5state resistance and leakage current. Bn the other hand, 'iC

'chottky barrier diodes '1! can reach a much higher breakdown voltage; )nfineon

offers products up to $8%%H as discrete and up to $G%%H in modules.

• Applications

• 'erver

• &elecom

• 'olar

• FP'

• PC 'ilverbo#

• Motor 1rives

• 0ighting

3eat$res /enefits

enchmark switching behavior

+o reverse recovery charge

&emperature independent

switching behavior

@igh operating temperature & -

ma# $GD9C!

'ystem efficiency improvement

compared to 'i diodes

Ieduced cooling re/uirements

Enabling higher

fre/uency3increased power

density

@igher system reliability due to

lower operating temperature

Ieduced EM)

• Diodes

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! " n h o m o # n c t i o n s

! $ e t e r o # n c t i o n s ! % e t a l & s e m i c o n d c t o r

# n c t i o n s

Diodes

! % e t a l & ' ( i d e & ) e m i c o n d c t o r * + T , % ' ) * + T -

! . n c t i o n * + T , . * + T -Field-efect

transistors

! $ e t e r o # n c t i o n B i " o l a r T r a n s i s t o r s

Bipolar junctiontransistor

s

! ) o l a r c e l l s ! / h o t o d e t e c t o r s ! / h o t o l m i n e s c e n c e ! + l e c t r o l m i n e s c e n c e ! L i g h t & e m i t t i n g d i o d e s ! L a s e r d i o d e s ! I m a g e s e n s o r s

Optoelectronic

Devices

Diodes

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NANOTEC9NOLO*:

Nanoaterials are defined as materials with at least one e#ternal dimension in the

si"e range from appro#imately $5$%% nanometers.

Nanoparticles are ob-ects with all three e#ternal dimensions at the nanoscale.

Nanotec"nology encompasses the understanding of the fundamental physics,

chemistry, biology and technology of nanometre5scale ob-ects.

Nanoparticles can eit+er e..

5 the naturally occurring

e.g., volcanic ash, soot from forest fires!

5 the incidental byproducts of combustion processes

e.g., welding, diesel engines!

5 are usually physically and chemically heterogeneous and often termed

ultrafine particles.

Engineered nanoparticles

- are intentionally produced and designed with very specific properties related

to shape, si"e, surface properties and chemistry.

- &hese properties are reflected in aerosols, colloids, or powders.

- Bften, the behavior of nanomaterials may depend more on surface area than

particle composition itself.

- Ielative5surface area is one of the principal factors that enhance its reactivity,

strength and electrical properties.

Engineered nanoparticles may be bought from commercial vendors or generated via

e#perimental procedures by researchers in the laboratory.

e.g., C+&s can be produced by laser ablation, @iPCB high5pressure carbon

mono#ide, arc discharge, and chemical vapor deposition CH1!!.

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E#amples of engineered nanomaterials include..

carbon buckeyballs or fullerenes; carbon nanotubes; metal or metal o#ide

nanoparticles e.g., gold, titanium dio#ide!; /uantum dots, among many others.

Researc" in t"e icroelectronics and nanotec"nology area includes topics such

as..

5 *abrication of new electronic materials and devices.

5 Computational studies of electronic devices.

Researc" in nanotec"nology in ot"er field of st$dies include..

iology

Medicine

Environment

Energy

Electronics 5Patterning and *abrication

Photonics

'ensors

Material 'ynthesis

Material Properties and Characteri"ation

Topics regarding nanotec"nology may cover..

+ew materials fabrications

+ew products applications

Materials Characteri"ation

Cleanrooms

@ealth )ssues

C+&

B0E1

4uantum 1ots

MEM'

'olar Cells

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@$rom articleA

Nanotec"nology6 9ealt" iss$es

Approac"es to Safe Nanotec"nology6 Managing t"e 9ealt" and Safety

Concerns Associated )it" Engineered Nanoaterials

&his document reviews what is currently known about nanoparticle toicity,

process eissions and epos$re assessent, engineering controls, and

personal protecti'e e-$ipent.

&his updated version of the document incorporates some of the latest results of

+)B'@ research, but it is only a starting point. &he document serves a dual purpose:

it is a summary of +)B'@s current thinking and interim recommendations; and it is a

re/uest from +)B'@ to occupational safety and health practitioners, researc"ers,

prod$ct inno'ators and an$fact$rers, eployers, )or8ers, interest gro$p

e#ers, and t"e general p$#lic to e#change information that will ensure that no

worker suffers material impairment of safety or health as nanotechnology develops.

;otential 9ealt" Concerns

&he potential for nanomaterials to enter the body is among several factors that

scientists e#amine in determining whether such materials may pose an occupational

health ha"ard. +anomaterials have the greatest potential to enter the body through

the respiratory system if they are airborne and in the form of respirable5si"ed

particles nanoparticles!. &hey may also come into contact with the skin or be

ingested.

ased on results from human and animal studies, airborne nanoparticles can be

inhaled and deposit in the respiratory tract; and based on animal studies,

nanoparticles can enter the blood stream, and translocate to other organs.

E#perimental studies in rats have shown that e/uivalent mass doses of insoluble

incidental nanoparticles are more potent than large particles of similar composition in

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causing pulmonary inflammation and lung tumors. Iesults from in vitro cell culture

studies with similar materials are generally supportive of the biological responses

observed in animals.

E#perimental studies in animals, cell cultures, and cell5free systems have shown that

changes in the chemical composition, crystal structure, and si"e of particles can

influence their o#idant generation properties and cytoto#icity.

'tudies in workers e#posed to aerosols of some manufactured or incidental

microscopic fine! and nanoscale ultrafine! particles have reported adverse lung

effects including lung function decrements and obstructive and fibrotic lung diseases.

&he implications of these studies to engineered nanoparticles, which may have

different particle properties, are uncertain.

Iesearch is needed to determine the key physical and chemical characteristics of

nanoparticles that determine their ha"ard potential.

;otential Safety Concerns

Although insufficient information e#ists to predict the fire and e#plosion risk

associated with powders of nanomaterials, nanoscale combustible material could

present a higher risk than coarser material with a similar mass concentration given

its increased particle surface area and potentially uni/ue properties due to the

nanoscale.

'ome nanomaterials may initiate catalytic reactions depending on their composition

and structure that would not otherwise be anticipated based on their chemical

composition.

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from website!

MEMS Tec"nology

https:33www.mems5e#change.org3MEM'3what5is.html


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Bver the past several decades MEM' researchers and developers have

demonstrated an e#tremely large number of microsensors for almost every possible

sensing modality including temperature, pressure, inertial forces, chemical species,

magnetic fields, radiation, etc. Iemarkably, many of these micromachined sensors

have demonstrated performances e#ceeding those of their macroscale counterparts.

&hat is, the micromachined version of, for e#ample, a pressure transducer, usually

outperforms a pressure sensor made using the most precise macroscale level

machining techni/ues. +ot only is the performance of MEM' devices e#ceptional,

but their method of production leverages the same batch fabrication techni/ues used

in the integrated circuit industry < which can translate into low per5device production

costs, as well as many other benefits. Conse/uently, it is possible to not only achieve

stellar device performance, but to do so at a relatively low cost level. +ot surprisingly,

silicon based discrete microsensors were /uickly commercially e#ploited and the

markets for these devices continue to grow at a rapid rate.

More recently, the MEM' research and development community has demonstrated a

number of microactuators including: microvalves for control of gas and li/uid flows;

optical switches and mirrors to redirect or modulate light beams; independently

controlled micromirror arrays for displays, microresonators for a number of different

applications, micropumps to develop positive fluid pressures, microflaps to modulate

airstreams on airfoils, as well as many others. 'urprisingly, even though these

microactuators are e#tremely small, they fre/uently can cause effects at the

macroscale level; that is, these tiny actuators can perform mechanical feats far larger than their si"e would imply. *or e#ample, researchers have placed small

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microactuators on the leading edge of airfoils of an aircraft and have been able to

steer the aircraft using only these microminiaturi"ed devices.

A surface micromachined electro5statically5actuated micromotor fabricated by the M+L. &his

device is an e#ample of a MEM'5based microactuator.

&he real potential of MEM' starts to become fulfilled when these miniaturi"ed

sensors, actuators, and structures can all be merged onto a common silicon

substrate along with integrated circuits i.e., microelectronics!. hile the electronics

are fabricated using integrated circuit )C! process se/uences e.g., CMB', ipolar,

or )CMB' processes!, the micromechanical components are fabricated using

compatible micromachining processes that selectively etch away parts of the

silicon wafer or add new structural layers to form the mechanical and

electromechanical devices. )t is even more interesting if MEM' can be merged not

only with microelectronics, but with other technologies such as photonics,

nanotechnology, etc. &his is sometimes called Jheterogeneous integration.K Clearly,

these technologies are filled with numerous commercial market opportunities.

hile more comple# levels of integration are the future trend of MEM' technology,

the present state5of5the5art is more modest and usually involves a single discrete

microsensor, a single discrete microactuator, a single microsensor integrated with

electronics, a multiplicity of essentially identical microsensors integrated with

electronics, a single microactuator integrated with electronics, or a multiplicity of

essentially identical microactuators integrated with electronics. +evertheless, as

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MEM' fabrication methods advance, the promise is an enormous design freedom

wherein any type of microsensor and any type of microactuator can be merged with

microelectronics as well as photonics, nanotechnology, etc., onto a single substrate.

A surface micromachined resonator fabricated by the M+L. &his device can be used as both

a microsensor as well as a microactuator.

&his vision of MEM' whereby microsensors, microactuators and microelectronics

and other technologies, can be integrated onto a single microchip is e#pected to be

one of the most important technological breakthroughs of the future. &his will enable

the development of smart products by augmenting the computational ability of

microelectronics with the perception and control capabilities of microsensors and

microactuators. Microelectronic integrated circuits can be thought of as the brains

of a system and MEM' augments this decision5making capability with eyes and

arms, to allow microsystems to sense and control the environment. 'ensors gather

information from the environment through measuring mechanical, thermal, biological,

chemical, optical, and magnetic phenomena. &he electronics then process the

information derived from the sensors and through some decision making capability

direct the actuators to respond by moving, positioning, regulating, pumping, and

filtering, thereby controlling the environment for some desired outcome or purpose.

*urthermore, because MEM' devices are manufactured using batch fabrication

techni/ues, similar to )Cs, unprecedented levels of functionality, reliability, and

sophistication can be placed on a small silicon chip at a relatively low cost. MEM'technology is e#tremely diverse and fertile, both in its e#pected application areas, as

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well as in how the devices are designed and manufactured. Already, MEM' is

revolutioni"ing many product categories by enabling complete systems5on5a5chip to

be reali"ed.

+anotechnology is the ability to manipulate matter at the atomic or molecular level to

make something useful at the nano5dimensional scale. asically, there are two

approaches in implementation: the top5down and the bottom5up. )n the top5down

approach, devices and structures are made using many of the same techni/ues as

used in MEM' e#cept they are made smaller in si"e, usually by employing more

advanced photolithography and etching methods. &he bottom5up approach typically

involves deposition, growing, or self5assembly technologies. &he advantages of

nano5dimensional devices over MEM' involve benefits mostly derived from the

scaling laws, which can also present some challenges as well.

An array of sub5micron posts made using top5down nanotechnology fabrication methods.

'ome e#perts believe that nanotechnology promises to:

a!. allow us to put essentially every atom or molecule in the place and position

desired < that is, e#act positional control for assembly,

b!. allow us to make almost any structure or material consistent with the laws of

physics that can be specified at the atomic or molecular level; and

c!. allow us to have manufacturing costs not greatly e#ceeding the cost of the

re/uired raw materials and energy used in fabrication i.e., massive

parallelism!.

Although MEM' and +anotechnology are sometimes cited as separate and distinct

technologies, in reality the distinction between the two is not so clear5cut. )n fact,

these two technologies are highly dependent on one another.

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&he well5known scanning t$nneling1tip icroscope %STM& which is used to detect

individual atoms and molecules on the nanometer scale is a MEM' device.

A colori"ed image of a scanning5tunneling microscope image of a surface, which is a

common imaging techni/ue used in nanotechnology.

'imilarly the atoic force icroscope %A3M& which is used to manipulate the

placement and position of individual atoms and molecules on the surface of a

substrate is a MEM' device as well. )n fact, a variety of MEM' technologies are

re/uired in order to interface with the nano5scale domain.

0ikewise, many MEM' technologies are becoming dependent on nanotechnologies

for successful new products. *or e#ample, the crash airbag accelerometers that are

manufactured using MEM' technology can have their long5term reliability degraded

due to dynamic in5use stiction effects between the proof mass and the substrate. A

nanotechnology called 'elf5Assembled Monolayers 'AM! coatings are now

routinely used to treat the surfaces of the moving MEM' elements so as to prevent

stiction effects from occurring over the products life.

Many e#perts have concluded that MEM' and nanotechnology are two different

labels for what is essentially a technology encompassing highly miniaturi"ed things

that cannot be seen with the human eye. +ote that a similar broad definition e#ists in

the integrated circuits domain which is fre/uently referred to as microelectronics

technology even though state5of5the5art )C technologies typically have devices with

dimensions of tens of nanometers. hether or not MEM' and nanotechnology are

one in the same, it is un/uestioned that there are overwhelming mutual

dependencies between these two technologies that will only increase in time.

Perhaps what is most important are the common benefits afforded by these

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technologies, including: increased information capabilities; miniaturi"ation of

systems; new materials resulting from new science at miniature dimensional scales;

and increased functionality and autonomy for systems.

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Cleanroo

@$rom esiteA

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http://www.advancetecllc.com/nanotechnology_microelectronics.htmlhttp://www.advancetecllc.com/nanotechnology_microelectronics.html


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Design Approach Facility Types

rod hng T&grid ceilings

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37/39

@$rom articleA

Nanotec"nology %CNT& in Ci'il>Str$ct$ral Engineering

+anoscience and nanotechnology provide enormous opportunities to engineers theproperties of materials by )or8ing in atoic or olec$lar le'el.

)t has not only facilitated to o'ercoe any liitations of con'entional

aterials, but also treendo$sly ipro'ed t"e ec"anical, p"ysical and

c"eical properties of t"e aterials as well.

&o develop "ig" perforance, $ltif$nctional, ideal %"ig" strengt", d$ctile,

crac8 free, d$ra#le& constr$ction aterial, carbon nanotubes C+&s! show

promising role to odify>en"ance t"e c"aracteristics of t"e con'entional

constr$ction aterials s$c" as concrete and steel.

)n the paper, a brief on geometry and mechanical properties, synthesis processes,

possibilities and findings of different researchers on CNT reinforced coposites is

presented. )t is also brought out that a crac8 free d$ra#le concrete is possible if

certain issues such as uniform distribution of C+& in composite and bond behavior of

C+& modified concrete can be addressed. *inally, few pre5proof of concepts are

mentioned where C+&s can play the pivotal role to redefine the scope and ability of

civil engineering, in general, and structural engineering, in particular.

Nanoscience +as pae( t+e ay to tailor t+e properties o$ materials ase( on

partic)lar re>)irement y or!ing in atomic or molec)lar leel. n general&

nanotec+nology is not an isolate( tec+nology $or certain p)rposes& )t it is an

enaling tec+nology to ac+iee many goals y engineering a material at nano leel.

*imilar to t+e $iel(s li!e energy& me(icine& electronics& etc.& nanotec+nology s+os

remar!ale potentiality o$ its role to play y opening a ne ay to sole many o$ t+e

perennial prolems ciil engineers (o $ace eery (ay. "ggressie (eelopment o$

in$rastr)ct)res )sing conentional constr)ctional materials ill e responsile $or

appro. one/t+ir( o$ gloal arming. t is estimate( t+at per ton pro()ction o$ cement

approimately pro()ces one ton o$ C2. %ence& t+ere is an alarming nee( $or

(eeloping ne constr)ction material +ic+ is smart& e$$icient an( s)stainale. +e

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co)ntries li!e n(ia& +ere grot+ o$ in$rastr)ct)re plays a signi$icant role in t+e

grot+ o$ t+e co)ntry& engineering o$ green an( smart constr)ction material ill

enormo)sly +elp to generate p)lic& priate& strategic an( societal goo(s. "mong all

t+e nano $orms o$ metals an( non/metals& caron nanot)es @CNsA seem to +ae

t+e most promising role toar(s (eeloping an i(eal @+ig+ strengt+& ()ctile& crac!

$ree& ()raleA constr)ction material li!e concrete. +e caron nanot)es @CNsA

attract t+e researc+ers since t+eir (iscoery& eca)se o$ t+eir +ig+er strengt+ an(

relatiely lo eig+t. +ese nanot)es are )se$)l $or any application +ere

ro)stness an( $leiility are necessary. )rt+er& nanot)es are also stale )n(er

etreme c+emical enironments& +ig+ temperat)res an( moist)re as ell. -se o$

nano engineere( concrete o)l( lea( to consi(erale re()ction in t+e (imensions o$

t+e str)ct)ral memers +ic+ co)l( res)lt in m)c+ less cons)mption o$ cement an(

t+erey re()ction o$ C2 release an( ma!e t+e orl( s)stainale t+ro)g+ eco/

$rien(ly pro()cts. )rt+er& caron nanot)es can also e )se( to ma!e nano

composite steel. nitial researc+ $in(ings reeal t+at t+ey are ao)t 50 times stronger

an( 10 times lig+ter t+an conentional steel. "part $rom tec+nical intricacies an( lac!

o$ in$ormation& one o$ t+e main ostacles in )sing CNs in constr)ction is cost o$

CNs as constr)ction materials nee( to e pro()ce( in mass an( s+o)l( e

reasonaly c+eap. Eoritant cost implications in pro()ction o$ CNs are (iminis+ing

ery $ast. or eample& cost o$ in()strial CN as D27&000:l in 1992& D550:l in

2006 an( D120:l in 2011. t is also pre(icte( t+at t+e price o)l( e as lo as

D0.5:l in 201314 1F. o ring o)t t+e est $rom caron nanot)es to t+e

constr)ction in()stry& speci$ically& in )sage o$ constr)ction materials& t+e

etraor(inary geometrical s+ape& )nparallel mec+anical properties& comple )t

c+allenging synt+esis processes& an( proale areas o$ applications are essential to

e !non. +ere$ore& an oerie o$ t+ese aspects o$ caron nanot)es it+ t+e

c)rrent state o$ !nole(ge is ro)g+t o)t in t+e present paper.

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PHY605 notes Semiconductor Materials.docx

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