NO2 sensing characteristics of WO3 thin film microgas sensor

WO3 thin film microgas sensor was fabricated with micro-electromechanical system (MEMS) technology and NO2 gas sensing characteristics were measured. The membrane embedded with Pt interdigitating electrodes and heater was prepared on silicon wafer, its size is 1.4 mm×1.4 mm. The device is 3 mm×3 mm in area. The power consumption to maintain the operating temperature of 300 °C is about 75 mW. WO3 thin films were prepared by magnetron sputtering on the membrane. The deposition parameters and operating temperatures were optimized to obtain the best performance of the WO3 film in the response to NO2 gas. The WO3 thin film deposited at 300 °C and then annealed in air at 600 °C for 4 h shows good sensing characteristics to NO2 gas at the operating temperature of 250 °C. The film morphology, crystalline phase and chemical composition were characterized through SEM, XRD and XPS.