Nanocrystalline SnO2 film prepared by the aqueous sol–gel method and its application as sensing films of the resistance and SAW H2S sensor

Abstract

Tin oxide (SnO2) has been employed as the sensitive film of surface acoustic wave (SAW) gas sensor, which enhanced the sensor performance toward H2S gas. However, the conventional sol–gel method is unfit for depositing SnO2 films on SAW devices as the sol can corrode the electrodes made of conventional metals due to its strong acidity. In this paper, a new aqueous and non-corrosive sol–gel method was adopted to deposit SnO2 films on SAW device substrate with little corrosion of electrodes. The prepared sol is weak alkaline and noncorrosive, which prevent the contact between the electrodes and the air during the sintering process. The surface morphology and microstructure of the prepared films were investigated and the H2S sensing properties of the films were studied. The gas sensing results showed that the prepared SnO2 films have the highest resistance response (the ratio of film resistance in air versus in H2S) 58,057 toward 13.7ppm H2S at 60°C and good selectivity for H2S detection. The SAW gas sensors had a good performance for detecting H2S at room temperature and at low relative humidity. This method can also be applied to prepare the sensing membrane of the other acoustic wave sensors.