Dilute hydrogen sulfide sensing properties of CuO-SnO₂ thin film prepared by low-pressure evaporation method

A low pressure evaporation method was adopted for preparing SnO₂ and CuO-SnO₂ thin films. Metallic tin and copper were evaporated on the alumina substrate under a low pressure (1 torr) of air atmosphere. As observed with AFM, these evaporated films had unique microstructure in which discrete clusters of SnO₂ grains (30 nm) contacted to each other two-dimensionally with large mesopores penetrating between. The film added with a small amount of CuO exhibited very high sensitivity to H₂S in air, being able to detect dilute H₂S close to 0.02 ppm at 300 °C. The high sensitivity seems to result from the unique promoting effect of CuO coupled with the unique microstructure of the film.