Cosputtered SnO2-ZnO composite nanofilms with improved dual function

Abstract

SnO2-ZnO composite thin films were grown by radio-frequency and direct-current cosputtering of ceramic ZnO and metallic Sn targets, respectively. During the cosputtering film growth, the SnO2 matrix sputtering power was fixed at 20 W, while the additive ZnO sputtering power was varied in the range of 40-80 W. Structural and compositional analysis results showed that the ZnO sputtering power increased the relative ZnO phase content in the composite film and its surface grain size. Compared to the single-constituent compounds, the as-synthesized SnO2-ZnO composite films exhibited enhanced photoelectrocatalytic performances for the degradation of methyl orange dyes under irradiation. The SnO2-ZnO composite film obtained at a ZnO sputtering power of 60 W (SZ60; Zn/Sn = 11.2%) exhibited the highest photoelectrocatalytic activity among the various samples. In addition, SZ60 exhibited superior ethanol gas-sensing performances among the various thin-film sensors. Owing to the formation of a suitable number of SnO2/ZnO heterojunctions, SZ60 exhibited a highly efficient photo-induced charge separation and appropriate potential barrier height to improve the gas-sensing ability. The experimental results demonstrate a promising approach to design oxide composite films with desirable photoelectrocatalytic and gas-sensing functions by controlling the relative content of ZnO and SnO2 in the composite film through a cosputtering process.