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| Abstract Title:
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| Four Terminal Hybrid Silicon and Organic Semiconductor Field Effect Transistors for Chemical Vapor Sensing
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| Graduate Student Presenter:
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Shannon Doane Lewis
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| Name of the Author(s) and Affiliation(s):
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Shannon Doane Lewis, IGERT Trainee Atomic and Molecular Imaging of Interfaces and Defects, The University of Texas at Austin; Ananth Dodabalapur, Ashley H. Priddy Centennial Professor in Engineering, The University of Texas at Austin
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Chemical sensing has been demonstrated in a four terminal hybrid device structure, in which the electron transporting silicon channel and the hole transporting organic channel gate each other across a silicon dioxide gate dielectric [1]. In this geometry, a traditional silicon field effect transistor (FET) is fabricated, but the gate electrode is replaced by one of several types of semiconductors: small molecule organics (such as pentacene), polymer organics (such as poly-3-hexylthiophene), or granular inorganic oxides (such as tin oxide).
The sensing mechanism is related to grain boundary defects in the non-silicon semiconductor. A vapor-phase molecule adsorbs to the surface of the defect rich top layer it changes both the current traveling from source to drain and the charge trapped in the organic or inorganic oxide layer. Because the silicon and organic or inorganic oxide layers gate each other, this results in a change in the silicon source to drain current.
The four terminal structure designed at the University of Texas at Austin enables this sensor structure to be operated in several different modes. In the most powerful mode, known as chemical memory mode, the device is written, read, and erased. The writing phase consists of biasing both channels on via separate source and drain electrodes. This is followed by the read phase in which the silicon channel current at a set source to drain bias is measured. Finally, the device is erased via reverse biasing of the silicon substrate in order to drive out trapped charge. This operation mode has demonstrated sensitivity to 100 ppb ethanol in nitrogen at a 100 fold increase in silicon drain current.
[1] Liang Wang, Daniel Fine, Saiful I. Khondaker, Taeho Jung and Ananth Dodabalapur. “Sub 10 nm conjugated polymer transistors for chemical sensing.” Sensors and Actuactors B 113 (2006) 539-544.
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