Electrical and ammonia gas sensing properties of poly (3, 3‴- dialkylquaterthiophene) based organic thin film transistors fabricated by floating-film transfer method

Abstract

Electrical and ammonia gas sensing properties of a poly (3, 3‴- dialkylquaterthiophene) (PQT-12) based organic thin film transistor (OTFT) fabricated by floating-film transfer method (FTM) on a highly doped p-type silicon substrate has been presented possibly for the first time in this paper. The OTFT is also fabricated using conventional spin coating method for the comparison with our FTM coated devices. The field effect mobility, threshold voltage, on/off current ratio and sub-threshold swing have been found as ∼8.77 × 10−3 cm2/V-s, −13.9 V, 843 and −8.5 V/dec, respectively for FTM coated devices. The drain current measured for different ammonia gas concentrations varying from 10 ppm to 80 ppm is observed to be decreased with increased ammonia concentration. A gas response of ∼56.4%, response time and recovery time of ∼45 s and ∼85 s, respectively at 80 ppm has been measured with a detection limit of 404 ppb for FTM coated devices. Significant changes in the values of field effect mobility, threshold voltage and on/off current ratio have been achieved at 80 ppm of ammonia gas with respect to their corresponding values measured prior to exposing the device to the ammonia gas. Both the electrical and ammonia gas sensing properties of FTM coated device are superior than spin coated devices.