The effect of heat treatment temperature and Mg doping on structural and photocatalytic activity of ZnO thin films fabricated by RF magnetron co-sputtering technique

Abstract

In this study, it is aimed to increase the photocatalytic activity of ZnO thin films, which have promising effect on degradation of textile dyes as photocatalysts, under the UV light by doping Mg element via magnetron co-sputtering method, and to investigate the effect of heat treatment temperature on structural and photocatalytic activity. For this purpose, 300 nm ZnO and MgZnO thin films were fabricated by RF magnetron co-sputtering method on Si (100) substrate at room temperature and heat-treated at 300 degrees C, 400 degrees C, 500 degrees C, and 600 degrees C. Microstructural, surface morphology, roughness and crystal properties of prepared thin films were characterized by Grazing Incident X-ray diffractometer (GIXRD), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Raman spectroscopy. X-ray photoelectron spectroscopy (XPS) measurement was performed to determine chemical states on the surface. XRD patterns with (002) and (103) planes indicate that ZnO and MgZnO thin films have a hexagonal wurtzite-type structure. Also, E-2High mode is the main Raman mode in the wurtzite crystal structure and confirms hexagonal wurtzite phase with good crystallinity in thin films. Photocatalytic activity of thin films was measured by UV-Vis spectroscopy with degradation of methylene blue (MB) solution under UV light irradiation. Results showed that, maximum photocatalytic efficiency was observed in heat-treated ZnO and MgZnO films at 400 degrees C with the kinetic rate constants 3.7 x 10(-2) s(-1) and 16.9 x 10(-2) s(-1), respectively. Also, for all samples the degradation of the MB at low concentrations are good agreement with the first-order velocity law.