H2 response characteristics for sol-gel-derived WO3-SnO2 dual-layer thin films

This paper describes the deposition of SnO2 and WO3 thin films and WO3-SnO2 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 H2 response characteristics, including response magnitude, time and transients of the three samples, were investigated at different operation temperatures and H2 gas concentrations. Although the maximum response magnitude of 29.31 towards 1000 ppm H2 gas appeared at 225 °C，the WO3-SnO2 dual-layer films still had a response magnitude of 24.23 at 175 °C, which is much higher than those of the SnO2 (4.19) and WO3 (6.73) thin films. The linear response magnitude profile of the WO3-SnO2 dual-layer thin films toward H2 gas concentration was obtained. The mechanism of the enhanced gas response characteristics was explained by the band bending theory.