The relationships between the film structure and photocatalytic characteristics of TiO₂ films deposited under oblique incidence by oxygen ion assisted reactive evaporation (OIARE) method.

Abstract

  We deposited the TiO₂ films at various oxygen ion accelerating voltages under oblique incidence by using OIARE method and investigated the relationships between their structures and photocatalytic performances. The films deposited at 350 ℃, the accelerating voltage of 200 eV, and substrate tilt angle of 35 degree had excellent photocatalytic performance of 17.7 [μmol・l^-1・min^-1] for the decomposition of metylene-blue. The film has anatase structure with mean surface roughness Ra of 11.4 nm and mean crystallite size of 18.0 nm. The photocatalytic performance takes a maximum value around 200 eV and decreases monotonically with further increase of the accelerating voltage. The mean crystallite size of the film was decreased from 20.8 nm to 14.3 nm by the increase of the oxygen ion accelerating voltage from 0 to 1000 eV, which suggests that the high energy oxygen ion bombardment to the film surface will produce damages in the film and degrading the performance of the film. These results indicate that control of the energy of oxygen ions incident to the film surface is important to obtain a film with excellent photocatalytic properties.