Catalytic effect of Ag embedded with ZnO prepared by Co-sputtering on H2S gas sensing MEMS device

Abstract

Ag doped ZnO thin films are deposited on a micro electromechanical systems (MEMS) device incorporating a microheater and sensing electrodes using a co-sputtering system. Structural properties and sensing properties were tested with pure Zn alongside with 0.15%, 0.3%, 0.5%, 1% and 2% Ag doping concentrations. The H2S gas sensing performance of the MEMS-based devices is evaluated for H2S concentrations in the range of 0.2–1.0 ppm and heating temperatures of 150–300 °C. The optimal sensing performance is obtained with a Ag concentration of 0.5% and a working temperature of 250 °C. For an H2S gas concentration of 1 ppm, the sensor achieves a sensing response of 16% and a response time of 3 s. The sensor additionally shows good selectivity for H2S gas compared to that for CO, NO2, NH3 and SO2, respectively. Finally, different response time phenomenon is explained due to the formation of Ag+ on doped ZnO surface.