Photoinduced Current of a CuO/ZnO Thin-Film Heterojunction in Humid Atmosphere

Abstract
The effects of the light illumination on the humidity sensing properties of a CuO/ZnO thin-film heterojunction where the interface is partly exposed to atmosphere were investigated. When ultraviolet light ( ∼400 nm) was applied to the heterojunction, a very large photoinduced current, about two orders of magnitude larger than that in dry air, was observed under humid conditions at the forward bias of the p-n junction above about 1 V. The increase of photoinduced current is assumed to be due to desorption of adsorbed oxygen species on ZnO promoted by the adsorption of water molecules and the application of the forward bias, which caused the changes of interface states.

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