Effect of deposition time on the photocatalytic activity of sputtered mixed ZnO–SnO2 thin films under visible light irradiation

Abstract

In this work, transparent conducting ZnO–SnO2 oxide thin films have been prepared on glass substrates by radio-frequency RF magnetron sputtering at different deposition times dt using powder targets. The structural, optical, electrical and photocatalytic properties of the deposited films were studied based on the increased deposition time (1 h, 2 h, 3 h and 4 h). X-ray diffraction (XRD) results showed an amorphous aspect for all sputtered layers, while the Raman study proved the presence of characteristic modes of spinel phase Zn2SnO4. UV visible Spectroscopy results revealed good homogeneity and high transparency of the films within the visible wavelength. The estimated values of the optical band gap decreased from 3.77 to 3.59 eV as deposition time increased. The films’ thickness ranged from 60 to 400 nm. Hall effect measurements exhibited that the conduction of all films was n-type and electrons represented the majority of free charge carriers. The lowest electrical resistivity, highest mobility and highest charge carrier concentration were obtained for dt = 1 h. The test of the catalytic efficiency of these ZnO–SnO2 thin films indicated that the best degradation of the methylene blue (MB) dye under solar irradiation was obtained for 210 min.