Room Temperature Hydrogen Sensor Using Schottky Contacted Zinc Oxide Thin-Film Transistor: A Comprehensive Investigation

Abstract

A ZnO-based Schottky thin-film transistor (TFT) utilizing palladium-titanium (Pd-Ti) source/drain electrodes as a sensing medium is used to fabricate a room temperature (RT) hydrogen sensor. In the absence of any heating element, the fabricated sensor is capable of reducing the design complications and power consumption considerably. The RT sensor response was realized with respect to drain current rise owing to the Schottky barrier height reduction depending on the H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> concentration (500-4500 ppm). For 500-ppm (minimum detection level) and 4500-ppm (maximum detection level) H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gas concentrations, sensor responses of 18% and 78.2% with 65 s/35 s and 10.2 s/85 s response/recovery times are acquired, respectively. The Pd-Ti/ZnO Schottky barrier height variation is attempted to explain the incorporating energy band diagrams of the ZnO channel between source/drain electrodes at different gate and drain bias conditions. Performance analysis of the sensor in terms of repeatability, selectivity toward H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> over methane and acetone, hysteresis, reliability, and humidity exposure has also been examined.