Structural analysis on photocatalytic efficiency of TiO₂ by chemical vapor deposition

Structural analysis of anatase TiO₂ films on window glass by chemical vapor deposition (CVD) was performed. Relationships between preferred orientation and photocatalytic activity of polycrystalline TiO₂ films were investigated. Photocatalytic activity was affected by crystalline orientation that depended on the deposition temperature. 〈112〉-oriented TiO₂ films were obtained at 360°C, while 〈001〉-oriented films were obtained at other temperatures. Photocatalytic activity of the 〈112〉-oriented film was greater than that of the 〈001〉-oriented film. The film with 〈11〉2-preferred orientation exhibited a columnar structure resulting in a larger surface area for photocatalytic reaction than the films with 〈001〉-preferred orientation. Also, the film with 〈112〉-preferred orientation exhibited a facet consisting of s-faces {100} which showed the larger surface energy theoretically. It is clear that fabrication of the thin film TiO₂ by CVD should be controlled to exhibit the 〈112〉-preferred orientation for the optimum photocatalytic efficiency.