A surface acoustic wave H2S gas sensor employing nanocrystalline SnO2 thin film

Abstract A surface acoustic wave (SAW) H 2 S gas sensor with high sensitivity and good recovery characteristics was presented. SnO 2 films with an average grain size of 25 nm were deposited as the sensitive film at the surface of the SAW devices using an aqueous sol–gel technique. The sensitivity toward H 2 S gas was increased by optimizing parameters including film thickness and operating temperature. The maximal response (center frequency change) toward 68.5 ppm of H 2 S was 112.232 kHz when the sensor was operated at 120 °C with SnO 2 film thickness of 275 nm. The frequency response of the SAW sensor showed good selectivity and a linear relation to H 2 S gas with different concentrations. We demonstrated that the dominant sensing mechanism of this SAW sensor is the acoustoelectric effect arising from the electrical conductivity change of the SnO 2 film. Further analysis of the optimum parameters and the good recovery characteristics were conducted based on the acoustoelectric effect.