(Color online) A dipole interacting with the image charge at the metal contact interface and with a charge (hole) at the grain boundaries of a p-type organic semiconductor in the field effect transistor configuration with a silicon substrate, SiO2 gate dielectric, and gold (Au) electrodes.
The sensing response of a P3HT device with a channel length of 7 nm exposed to 1-pentanol with currents simultaneously recorded at the drain (top) and side guarding electrodes (bottom). The side electrodes were held at the same potential as the drain, V G = −20V and V DS = V side= − 1.5 V. The side current represents the large area around the nanoscale channel (behaving similar to a large channel device), eliminating the spreading currents. The elimination of the spreading current allows the sensing behavior of the nanoscale device to be truly represented. Reprinted with permission from L. Wang, D. Fine., S. I. Khondaker, T. Jung, and A. Dodabalapur, Sens Actuators B 113, 539 (2006). Copyright 2005, Elsevier.
(Color online) Effect of a polar analyte at the contact/semiconductor interface. Upon exposure of an injection limited device to a polar analyte, the dipole aligns itself to interact with the interface dipole. The electrostatic interaction shifts the metal work function to enhance charge injection.
(Color online) Polar analyte (ethanol) interacting with charge carriers at the grain boundaries. This interaction shifts the carriers into deeper trap states and pushes the Fermi level further away from the band edge.
(Color online) Time-resolved sensing response (normalized I DS) of a copper phthalocyanine OTFT exposed to allyl propionate (top) and ethanol (bottom). The blocked region for both plots represents analyte exposure.
(Color online) Time-resolved sensing response (normalized I DS) of two pentacene based nanometer scale devices exposed to 1-pentanol with a channel length of 1 μm (top) and 450 nm (bottom) with an average grain size of 250 nm. The blocked region represents analyte exposure.
(Color online) Modification of carrier energy levels through molecular polaronic effects, disorder, and polar analyte effects. Reprinted with permission from D. Duarte, D. Sharma, B. Cobb, and A. Dodabalapur, Appl. Phys. Lett. 98, 133302 (2011). Copyright 2011, American Institute of Physics.
Activation energy shifts with increasing ethanol concentration in nitrogen 0 ppm (pure N2) to 500 ppm for two pentacene based OFETs with mobilities of 1 × 10−3 cm2/V s (top) and 0.1 cm2/V s (bottom). Reprinted with permission from D. Duarte, D. Sharma, B. Cobb, and A. Dodabalapur, Appl. Phys. Lett. 98, 133302 (2011). Copyright 2011, American Institute of Physics.
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