Novel hydrogen gas sensing by palladium electrode on dielectric capacitor coupled with an amorphous InGaZnO thin-film transistor

Palladium (Pd) is well known for its capability to selectively detect hydrogen (H-2) gas, where the detection process involves absorbing hydrogen gas molecules to form compound palladium hydrides. Such Pd-H interaction leads to the increase of electrical resistance and volume of Pd, simultaneously lowering its work function. These Pd-based hydrogen sensors would be more beneficial when connected to conventional semiconductor integrated circuits. Here, we utilize the Pd film as H-sensing electrode for metal/SiO2/p(+)-Si (MIM) capacitor, since we found the H-induced chain reactions in Pd/SiO2/p(+)-Si capacitor:Pd volume expansion, Pd-SiO2 contact are change, and the capacitance change. This capacitance change is connected to the gate of an electrically stable amorphous InGaZnO (a-IGZO) thin-film transistor (TFT). As a result, H-induced output as the drain current of a-IGZO TFT was statically and dynamically measured through the capacitance signal change from Pd-MIM sensor. This output current signal was converted to voltage when a load resistor was connected to the a-IGZO TFT in series. These sensor circuit configurations are regarded promising and novel because of their simplicity and practicality. (C) 2014 Elsevier B.V. All rights reserved.