OFET sensors

OFET Sensors Titto Thomas

133079015

M.Tech Seminar

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


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


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


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

Bio-Sensors

DNA

Proteins

Glucose

Others

Gas Sensors Chemical Sensors

Ions

Humidity

pH

Others

Other sensors

X-ray

Others

Bio-sensors : DNA


[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]


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,”

Bio-sensors : Overview


Chemical Sensors : Ions & pH


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


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

Chemical sensors : Overview


Gas Sensors


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]

Gas sensors : overview


Explosive vapor sensor


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


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


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


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


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

Thank You

20 OFET Sensors : IIT Bombay

OFET sensors

Technology

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