OFET sensors
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Transcript of OFET sensors
Introduction
OFET Sensors : IIT Bombay 2
Sensors
Transducer Conversion into signals
Applications
Organic conducting polymers
Discovery
Applications
Organic Thin Film Transistor (OTFT)
[1] H. Shirakawa et al. , “Synthesis of electrically conducting organic polymers: halogen derivatives of
polyacetylene, (ch),”, 1977
[2] P. Lin and F. Yan, “Organic thin-film transistors for chemical and biological sensing,” 2012
[2]
[1]
More about OTFTs
OFET Sensors : IIT Bombay 3
Internal amplification and noise correction
Compatibility with existing VLSI Technology
Sensors could be
Biodegradable Flexible Cost effective
More information than any other sensor
OTFT OECT
OFET
Device Structure & Working
OFET Sensors : IIT Bombay 4
OECT
Source & Drain electrodes
OFET
OSC channel
Electrolytic layer on top
Similar to OECT
Direct interaction with analyte
Two configurations [1]
[1] P. Lin and F. Yan, “Organic thin-film transistors for chemical and biological sensing,”, 2012
OFETs in detail
OFET Sensors : IIT Bombay 5
Two configurations
[1]
[1] H. Ma, et al., “Multifunctional phosphoric acid self-assembled monolayers on metal oxides as
dielectrics, interface modification layers and semiconductors for low-voltage high-performance organic
field-effect transistors,”, 2012
Top contact
Bottom contact
Follows standard MOSFET equations
Lower mobility in the channel
OFET Sensors in detail
OFET Sensors : IIT Bombay 6
OFET Sensors
Bio-Sensors
DNA
Proteins
Glucose
Others
Gas Sensors Chemical Sensors
Ions
Humidity
pH
Others
Other sensors
X-ray
Others
Bio-sensors : DNA
OFET Sensors : IIT Bombay 7
[1]
[1]http://www.intechopen.com/books/biosensors/design-and-fabrication-of-nanowire-based-
conductance-biosensor-using-spacer-patterning-techniq
[2] Q. Zhang and V. Subramanian, 2012 [3] F. Yan, S. M. Mok, J. Yu, H. L. Chan, and M. Yang, 2009
Zhang et al. used pentacene as the OSC channel
DNA adsorption VT shift Electron extraction by DNA
[2]
[2]
Improvement suggestions
Reducing film thickness or
current
Increase substrate
temperature
Yan et al. proposed another device using P3HT [3]
OFET Sensors : IIT Bombay 8
Bio-sensors : Glucose & Others J.Liu et al. proposed PEDOT-PSS organic channel with GOx
entrapped
GOx entrapped during polymerization
Redox reaction channel and glucose with Gox
catalysis
Sensor based on Ta2O5 and P3HT , by Bartic et al.
GOx anchored on surface
Cyanopropyltrichlorosilane treatment
Roberts et al. OFET to detect glucose, cystein, and MPA by
DDFTTF as the OSC channel
[1]
[2]
[3]
[1] J. Liu, M. Agarwal, and K. Varahramyan, “Glucose sensor based on organic thin film transistor using glucose oxidase and conducting polymer,” , 2008 [2] C. Bartic, A. Campitelli, and S. Borghs, “Field-effect detection of chemical species with hybrid organic/inorganic transistors,” , 2003 [3] M. E. Roberts, S. C. B. Mannsfeld, N. Queralt, C. Reese, J. Locklin, W. Knoll, and Z. Bao, “Water-stable organic transistors and their application in chemical and biological sensors,”
Chemical Sensors : Ions & pH
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Ji et al. P3HT as the OSC, with Ta2O5 and valinomycin subsequently deposited on top
Detects K , H ions and pH levels + +
Scarpa et al. used P3HT as channel
K , Na, Ca ions and pH levels even at 0.001% + + 2+
Maddalena et al. had a sulfate receptor with incorporated
thiol group, coupled polystyrene layer
Detects sulphate ions with 1mM
[1]
[2]
[3]
[1] T. Ji, P. Rai, S. Jung, and V. K. Varadan, “In vitro evaluation of flexible ph and potassium ion-sensitive organic field effect transistor sensors,” 2008 [2] G. Scarpa, A.-L. Idzko, A. Yadav, and S. Thalhammer, “Organic ISFET based on poly (3-hexylthiophene),” 2010 [3] F. Maddalena, M. J. Kuiper, B. Poolman, F. Brouwer, J. C. Hummelen, D. M. de Leeuw, B. De Boer, and
P. W. M. Blom, “Organic field-effect transistor-based biosensors functionalized with protein receptors,” , 2010
OFET Sensors : IIT Bombay 11
Chemical Sensors : Ions & pH Bartic et al. reported a P3HT OSC OFET
Indicates the pH values after in-situ amplification
Coating with arachidic acid improves the sensitivity
Pentacene OSC based OFET proposed by Loi et al.
variations in charge at the gate-channel interface
coating the floating gate with thioaminic groups
Water stable OFET which can detect pH 3 to 11, using DFTTF
OSC channel by Roberts et al.
[1]
[2]
[3]
[1] C. Bartic, A. Campitelli, and S. Borghs, “Field-effect detection of chemical species with hybrid organic/inorganic transistors,” 2003 [2] A. Loi, I. Manunza, and A. Bonfiglio, “Flexible, organic, ion-sensitive field-effect transistor,” 2005 [3] M. E. Roberts, S. C. B. Mannsfeld, N. Queralt, C. Reese, J. Locklin, W. Knoll, and Z. Bao, “Water-stable organic
transistors and their application in chemical and biological sensors,” 2008
Gas Sensors
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Laurs et al. observed that oxygen, iodine and bromine could
vary the current through the OFET fabricated with
phthalocyanines (Pcs) as the OSC.
Torsi et al. fabricated NTCDA
based OFET, and found four
characteristic parameters to
be varying.
Someya et al. and Torsi et al.
Reported the dependancy of
sensitivity on grain size.
[1] H. Laurs and G. Heiland, “Electrical and optical properties of phthalocyanine films,” 1987 [2] L. Torsi, A. Dodabalapur, L. Sabbatini, and P. Zambonin, “Multi-parameter gas sensors based on organic thin-film-transistors,” 2000 [3] T. Someya, A. Dodabalapur, A. Gelperin, H. E. Katz, and Z. Bao, “Integration and response of organic
electronics with aqueous microfluidics,” 2002 [4] L. Torsi, A. J. Lovinger, B. Crone, T. Someya, A. Dodabalapur, H. E.Katz, and A. Gelperin, “Correlation between oligothiophene thin film transistor morphology and vapor responses,” 2002
[1]
[2]
[3] [4]
Explosive vapor sensor
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A particular type of gas sensor
Materials proposed to be
used as OSC channel
RDX TNT
OFETs as explosive sensors
Poly 3-hexylthiophene
(P3HT)
Cu tetraphenylpophyrin (CuTPP)
[1] Ravishankar S. et al. “Explosive vapor sensor using poly 3-hexylthiophene and Cu tetraphenylporphyrin composite based organic field effect transistors“ 2008 [2] http://www.aist.go.jp/aist_e/aist_laboratories/2information
[1]
[2]
II
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Device structure and fabrication
SiO2 layer grown on n silicon wafer
Au / Ti Source & Drains are patterned
CuTPP & P3HT dissolved in chloroform is spin coated
HMDS Surface enhancement
[1] Ravishankar S. et al. “Explosive vapor sensor using poly 3-hexylthiophene and Cu tetraphenylporphyrin composite based organic field effect transistors“ 2008
[1]
Device Characterization
OFET Sensors : IIT Bombay 17
Significant rise in drain current & conductance in the presence
of nitro compounds
Threshold voltage is found out by linear fit of Transfer Chara
Behavior can be modeled by using existing equations
Shift in FTIR peaks on sensor exposure to RDX
OFET explosive vapor sensor : Results & Conclusion
OFET Sensors : IIT Bombay 18
The OFET formed has high sensitivity to nitro based explosives
ION & S parameters can be evaluated to check the presence
Selectivity of
the sensor for
various vapors
Conclusions & Future Scope
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OFETs are effective sensors for detecting various types of
materials
Many materials being tried out to be used in sensors have a
promising performance
Also there is a need for new structures and modifications to
enhance the sensing abilities of sensors
Sensitivity, selectivity, stability all have to be improved before
using them in real life applications