Photocatalytic TiO2 deposition by chemical vapor deposition

Abstract

Dip-coating, spray-coating or spin-coating methods for crystalline thin film deposition require post-annealing process at high temperature. Since chemical vapor deposition (CVD) process is capable of depositing high-quality thin films without post-annealing process for crystallization, CVD method was employed for the deposition of TiO2 films on window glass substrates. Post-annealing at high temperature required for other deposition methods causes sodium ion diffusion into TiO2 film from window glass, resulting in the degradation of photocatalytic efficiency. Anatase-structured TiO2 thin films were deposited on window glass by CVD, and the photocatalytic dissociation rates of benzene with CVD-grown TiO2 under UV exposure were characterized. As the TiO2 film deposition temperature was increased, the (112)-preferred orientations were observed in the film. The (112)-preferred orientation of TiO2 thin film resulted in a columnar structure with a larger surface area for benzene dissociation. Obviously, benzene dissociation rate was maximum when the degree of the (112) preferential orientation was maximum. It is clear that the thin film TiO2 should be controlled to exhibit the preferred orientation for the optimum photocatalytic reaction rate. CVD method is an alternative for the deposition of photocatalytic TiO2. (C) 2000 Elsevier Science B.V. All rights reserved.