Evaluation of photocatalytic properties of titanium oxide films prepared by plasma-enhanced chemical vapor deposition

Photocatalytic titanium oxide (TiO2) films were prepared by plasma-enhanced chemical vapor deposition (PECVD). All the films prepared in this study were nearly stoichiometric titanium dioxide. X-ray diffraction shows weak diffraction peaks of anatase even in the as-grown film, and their intensities increase after 600 °C annealing. The crystalline phase changes from anatase to rutile after 900 °C annealing. The anatase films have a surface where high-density small grains have gathered, while the rutile film has an uneven surface with elongated grains. When the PECVD-TiO2 films were irradiated by UV-light, the photocatalytic reactions occur on the film surface, namely the photo-induced decomposition of organic compounds and the photo-induced hydrophilicity. These photocatalytic reactions occur more strongly on the anatase film than the rutile film. Moreover, photocatalytic activity strengthens with increasing crystallinity of anatase.