Photocatalytic Zn-doped TiO2 films prepared by DC reactive magnetron sputtering

Zn-doped TiO2 films were prepared by means of pulsed DC reactive magnetron sputtering method using Ti and Zn mixed target. The deposition condition was optimized to produce uniform and transparent TiO2 films. Titanium was in the Ti4+ oxidation state in all Zn-doped TiO2 films. The zinc oxide deposited on the substrate was in the fully oxidized state of ZnO. Increase of zinc concentration inhibited the crystal growth in the TiO2 films. The surface morphology gradually changed from crystalline to amorphous along with the increase of doped zinc concentration. The optical transmittances of these films decreased only slightly with increasing zinc concentration due to very similar band edges of ZnO and anatase TiO2. The doped ZnO had weak influence on light absorption of the TiO2 films. When zinc concentration was very low (<1 at%), the photocatalytic activities of the doped films had nearly no difference from that of pure TiO2 film. Photocatalytic activities decreased obviously in the films containing high amount of zinc oxide.