Enhanced catalytic activity of ultrathin CuO islands on SnO2 films for fast response H2S gas sensors

H₂S gas-sensing properties of a novel SnO₂-CuO structure consisting of ultrathin (∼10 nm) CuO dotted islands (600 μm diameter) on 120-nm thick, sputtered SnO₂ film are compared with a pure SnO₂ and a SnO₂-CuO bilayer sensor. The SnO₂-CuO-dotted sensor exhibited a high sensitivity of 7.3×10³ at a low operating temperature of 150°C. A fast response time of 14 s for 20 ppm of H₂S gas and a recovery time of 118 s under flowing air have been measured. The electronic interaction due to modulation of the space charge regions between the distributed p-type CuO islands on the n-type SnO₂ thin-film surface and the presence of adsorbed oxygen on the SnO₂ support have been analyzed. Dissociated hydrogen available from the CuO-H₂S interaction spills over and its chemical interaction with the adsorbed oxygen on the SnO₂ surface is found to play a dominant role in the observed fast response characteristics.