Fabrication, characterization, and electrical measurements of gas ammonia sensor based on organic field effect transistor

Abstract

Ammonia gas sensors were fabricated based on organic field effect transistor “OFET” with n-type Si or indium tin oxide “ITO” substrate as gate electrodes and SiO2 or polymethylmethacrylate “PMMA” as gate insulator layers, respectively. Different organic semiconductor channel “OSC” layers based on polyaniline “PANI” doped with dodecylbenzene sulfonic acid “DBSA”, polyaniline–emeraldine base “PANI:EB”, and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate “PEDOT:PSS” were created between source and drain electrodes. Confocal laser scanning microscopy “CLSM” was used to identify the OFET surface profiling and to measure the dimensions and thicknesses of OFET layers. The performance of the OFET ammonia sensor was evaluated based on the change in the electrical measurements such as the current–voltage “IDS–VDS” characteristic curve, saturation current, and threshold voltage at room temperature. Relative response “ΔR” and response/recovery time of the OFET ammonia sensors with different organic semiconductor layers were obtained from the change in the drain–source current “IDS” at zero gate voltage when the sensors were exposed to different consecutive cycles and evacuation of ammonia gas. The OFET sensor has PANI:DBSA as an active channel layer with Si or ITO gate exhibited ΔR to ammonia gas of ~ 63% and ~ 41.4% with response time of 2 and 4 s, respectively.