Sputter deposition of high transparent TiO2−xNx/TiO2/ZnO layers on glass for development of photocatalytic self-cleaning application

In this study, TiO2−xNx/TiO2 double layers thin film was deposited on ZnO (80 nm thickness)/soda-lime glass substrate by a dc reactive magnetron sputtering. The TiO2 film was deposited under different total gas pressures of 1 Pa, 2 Pa, and 4 Pa with constant oxygen flow rate of 0.8 sccm. Then, the deposition was continued with various nitrogen flow rates of 0.4, 0.8, and 1.2 sccm in constant total gas pressure of 4 Pa. Post annealing was performed on as-deposited films at various annealing temperatures of 400, 500, and 600 °C in air atmosphere to achieve films crystallinity. The structure and morphology of deposited films were evaluated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM). The chemical composition of top layer doped by nitrogen was evaluated by X-ray photoelectron spectroscopy (XPS). Photocatalytic activity of samples was measured by degradation of Methylene Blue (MB) dye. The optical transmittance of the multilayer film was also measured using ultraviolet-visible light (UV-vis) spectrophotometer. The results showed that by nitrogen doping of a fraction (∼1/5) of TiO2 film thickness, the optical transmittance of TiO2−xNx/TiO2 film was compared with TiO2 thin film. Deposited films showed also good photocatalytic and hydrophilicity activity at visible light.

► In this study, TiO2−xNx/TiO2/ZnO multilayer thin film was deposited on ZnO (80 nm thickness)/soda-lime glass substrate by a dc reactive magnetron sputtering. ► The results showed that by nitrogen doping of a fraction (∼1/5) of TiO2 film thickness, the optical transmittance of TiO2−xNx/TiO2 film was improved than TiO2 thin film. ► The optical transmittance of the film on glass was not destroyed by this doping due to considering doping of only fraction of TiO2 coating thickness. ► Besides, the films showed also good photocatalytic and hydrophilicity activity in visible light. So, the low absorption edge of TiO2 in visible light range was improved by nitrogen doping.