Gas sensing characteristics of SnO2 thin films and analyses of sensor response by the gas diffusion theory

Nanocrystalline SnO2 thin films with crystallite size of 14.5–20.3 nm and thickness of 206–342 nm are prepared by sol–gel technique. The films not only exhibit high response of 1478 to 68.5 ppm H2S gas at 60 °C, but also show fast response time of 8 s and the ability of recovery. The influences of various basic parameters on sensor response are discussed, such as film thickness, crystallite size, operating temperature and gas concentration. The gas diffusion theory is applied to analyze the experimental data quantitatively and it gives out explanation to all the relationships satisfactorily, except the one between response and gas concentration, proving that the theory is basically applicable to H2S detection. Furthermore, the original reason of the deviation between the theory and response versus gas concentration is revealed.