Copper doping in titanium oxide catalyst film prepared by dc reactive magnetron sputtering

Copper-doped titanium oxide films were prepared by dc magnetron sputtering using Ti and Cu mixed target. The XPS spectra showed that titanium was in the Ti4+ oxidation state and oxygen was in the form of O2− in TiO2 and CuO. Apparent high-intensity shake-up satellites of the main Cu 2p peaks indicated the existence of fully oxidized CuO in the Cu-doped TiO2 films. When the copper concentration was low, the Cu-doped TiO2 film had the similar anatase phase as pure TiO2. The samples became amorphous when copper concentration was more than 15.17 at.%. Copper oxides were in the amorphous state in all the films. In the sequence of decreasing copper concentration, the surface morphologies changed from flat to nano-crystalline with nano-sized pores. The absorption edges of the Cu-doped samples shifted to longer wavelength region and the optical transmittances of these films decreased abruptly with increasing copper concentration. The Cu-doped TiO2 films had different photocatalytic behavior in accordance with the amount of doped copper. The best copper doping concentration was 1.45 at.% in sample I, relating to the most effective photocatalytic activity.