Room temperature ammonia gas sensing characteristics of copper oxide-tin oxide composite thin films prepared by radio frequency magnetron sputtering technique

Abstract

In this work, thin films of composite copper oxide-tin oxide [CuO:SnO2 (1:1)] were prepared by radio frequency magnetron sputtering technique at room temperature on quartz glass substrates. X-ray diffraction study revealed that the as-deposited films were amorphous in nature and the crystallinity of the films was obtained by annealing the films at 1000 °C. The hexagon rod-like structure, dews-like particles and cylindrical-shaped particles were observed in surface morphological study. The X-ray photoelectron spectroscopic study confirmed the formation of Cu2+ and Sn4+ states in the deposited films. The decrease in optical energy band gap with increase in RF power and annealing temperature may be due to the creation of localized states near the band edges of CuO:SnO2. The gas sensing characteristics of the films were analysed by recording the electrical resistance variation of the films in the presence/absence of various concentrations of NH3 gas at room temperature. The CuO:SnO2 film exhibited a highest sensing response of 3838 for 125 ppm of NH3 gas at room temperature. The film sustained its initial sensor response even after 6 months period for 5 repeated cycles, which ascertained the stability and repeatability of CuO:SnO2 thin film based gas sensor.