Surface Acoustic Wave Relative Humidity Sensor Based On Sputtering Sio2 Film

A surface acoustic wave (SAW) relative humidity (RH) sensor was prepared by sputtering SiO2 sensing film on the total surface of an SAW resonator. The prepared humidity sensor exhibits good linear relationship under wide RH range of 10%-80%. Small hysteresis is observed during the adsorption and desorption processes. The sensitivity of the sensor is -1.14 kHz/% for the adsorption process and -1.06 kHz/% for the desorption process. The sensing mechanism of the sensor can be explained from the mass loading effect of the SiO2 film. The response time is 6.0 s and the recovery time is 21.3 s when the RH switches between 10% and 70%. Moreover, the SAW sensor also shows good repeatability and stability due to the high adhesion of the sputtering SiO2 film to the substrate.