Control of Nano-Structure of Photocatalytic TiO2 Films by Oxygen Ion Assisted Glancing Angle Deposition

Abstract

Control of the nano-structure of TiO2 photocatalytic films by a glancing angle deposition was investigated using an oxygen ion assisted reactive evaporation (OARE) system. The porosity of the film was increased as the incidence angle of Ti vapor increased, and films with clearly separated columnar grains were obtained at an incident angle above 60°. The increase in the porosity led to a significant decrease in UV reflectance and the film deposited at 60° had a large UV absorptance above 80% at 300 nm. The photocatalytic performance of the film, however, did not improve remarkably, since the crystallinity of the film was degraded by the deposition at a high incidence angle above 60°. To improve the crystallinity of the film, control of energy of the incident oxygen ions was attempted. However, only a slight improvement of photocatalytic properties was observed.