Dependence of sensing performance of OTFT-based H2 sensor on channel length

Abstract

For a hydrogen sensor based on organic thin-film transistor (OTFT) with palladium (Pd) source/drain (S/D) electrodes as the sensing medium, the effects of channel length on its sensing performance are investigated. When exposed to a fixed hydrogen concentration, the device shows lower carrier mobility for smaller channel length down to 10 μm. The involved mechanism is that for the same hydrogen-induced expansion of the S/D electrodes, the resulting compressive strain in the channel region between the S/D electrodes of the OTFT increases with decreasing channel length, leading to a larger reduction in carrier mobility and thus a higher sensitivity to hydrogen. Moreover, the response and recovery times of the sensor are hardly affected by the channel length because both are mainly governed by the diffusion of hydrogen atoms in the S/D electrodes.