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

H
₂
S gas-sensing properties of a novel SnO
₂
-CuO structure consisting of ultrathin (∼10 nm) CuO dotted islands (600 μm diameter) on 120-nm thick, sputtered SnO
₂
film are compared with a pure SnO
₂
and a SnO
₂
-CuO bilayer sensor. The SnO
₂
-CuO-dotted sensor exhibited a high sensitivity of 7.3×10
³
at a low operating temperature of 150°C. A fast response time of 14 s for 20 ppm of H
₂
S 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 SnO
₂
thin-film surface and the presence of adsorbed oxygen on the SnO
₂
support have been analyzed. Dissociated hydrogen available from the CuO-H
₂
S interaction spills over and its chemical interaction with the adsorbed oxygen on the SnO
₂
surface is found to play a dominant role in the observed fast response characteristics.