Preparation and characterization of rare earth ions-doped TiO₂ photocatalyst film by RF-magnetron sputtering

This research studied on the preparation and the effect of Yb₂O₃ and Er₂O₃ doped TiO₂ on the surface morphology, optical and photocatalyst properties under UV and fluorescent irradiation of thin films via RF-magnetron sputtering method. The preparation conditions were fixed for applied power, distance between target-substrate and substrate heating temperature at 150 W, 5.0 cm and 500 °C, respectively. All deposited films were controlled the thickness at about 1.0 μm by varying deposition time. As the results, all of prepared films showed only pure anatase phase. The sputtering pressure and sputtering gas had significantly affected on the microstructure of TiO₂ film. The films prepared under high pressure (3 Pa) and pure Ar gas displayed porous structure and high surface roughness, resulted in high photocatalytic activity. While the TiO₂ films prepared under gas mixture Ar/O₂ (8/2) showed porous structure with lower surface roughness resulted in lower photocatalytic activity than that of film prepared under pure Ar gas. In case of TiO₂ films doping with Yb₂O₃ and Er₂O₃, the increasing in surface roughness and the decreasing in transmittance of the films prepared under gas mixture of Ar/O₂ (8/2) when concentration of Yb₂O₃ and Er₂O₃ target increased from 0.5 to 1.0 mol% was observed. Moreover, the absorption thresholds slightly shifted to longer wavelength which was attributed to the decreases in band gap energy. And higher photocatalytic activity under UV and Fluorescent irradiation was obtained. The similar result of absorption and band gap energy of the films prepared under pure Ar was also observed. But the difference in surface roughness was not significantly affected as the concentration of dopant increased. In addition, the doped films prepared under gas mixture had better photocatalytic activity than that of films prepared under pure Ar gas.