CuO/ZnO Heterojunction Nanostructured Sensor Prepared on MEMS Device for Enhanced H2S Gas Detection

Gas sensing properties of pure ZnO and CuO layered ZnO nanostructures prepared on Micro Electro Mechanical system (MEMS) devices has been investigated. ZnO nanostructure is prepared using hydrothermal process and the structure deposited has rough surface with number of pores. CuO films (25 nm and 50 nm) are deposited on the ZnO nanostructure using RF sputtering process and the total thickness of 25 nm CuO layered ZnO is recorded about 3.30 μm. For the sake of gas sensing working conditions, MEMS microheater thermal properties are also studied. CuO coated ZnO MEMS device is tested for H2S gas at 200 °C temperature. Gas sensing properties of 25 nm thickness CuO on ZnO MEMS device sensor shown 42.5% of enhanced sensing response at 1 ppm when compared to pure ZnO sensor which only showed 23.2% response. The enhanced sensing response is due to the formation of CuO and ZnO heterojunctions. The sensor exhibited good sensitivity towards H2S gas than other gases (SO2, CO, NH3 and ethanol) at the operating temperature of 200 °C. A random repeatability test at 800 ppb H2S gas concentration is done with 25 nm CuO layered ZnO which showed good repeating sensing results.