High H2S-sensitive copper-doped tin oxide thin film

The gas sensitivity of SnO2-based thin films doped with 0.05–2 wt.% Cu has been studied. The films were deposited by the conventional spray pyrolysis technique. The H2S sensitivity and selectivity in relation to the concentration of Cu in SnO2 has been systematically studied. A remarkable sensitivity towards H2S at the operating temperature of 200 °C is observed for the Cu-doped SnO2. The incorporation of Cu in the SnO2 makes the film crystalline at lower deposition temperatures along with an enhanced sensitivity towards H2S. The 1.19 wt.% Cu-doped SnO2 exhibits a sensitivity of 910 for H2S as compared to 12 for the pure SnO2 at an operating temperature of 200 °C, where the sensitivity of the film is calculated as the ratio of change in the conductance to the original conductance. The effect of surface coverage, morphology, oxidation state and amount of Cu on the sensitivity has been studied. The correlation between Cu incorporation in the SnO2 thin film at different deposition temperatures and the improvement in the selectivity and sensitivity towards hydrogen sulfide is discussed.