H 2 response characteristics for sol–gel-derived WO 3 -SnO 2 dual-layer thin films

Abstract This paper describes the deposition of SnO 2 and WO 3 thin films and WO 3 -SnO 2 dual-layer thin films using the sol-gel process. The microstructure and morphology of these three thin films were analyzed with FE-SEM and X-ray diffraction. The H 2 response characteristics, including response magnitude, time and transients of the three samples, were investigated at different operation temperatures and H 2 gas concentrations. Although the maximum response magnitude of 29.31 towards 1000 ppm H 2 gas appeared at 225 °C，the WO 3 -SnO 2 dual-layer films still had a response magnitude of 24.23 at 175 °C, which is much higher than those of the SnO 2 (4.19) and WO 3 (6.73) thin films. The linear response magnitude profile of the WO 3 -SnO 2 dual-layer thin films toward H 2 gas concentration was obtained. The mechanism of the enhanced gas response characteristics was explained by the band bending theory.