Photocatalytic Characteristics and Structure of TiO2 Film Deposited by Oxygen-Ion-Assisted Reactive Evaporation at Low Temperature

Abstract

We investigated the room temperature deposition of photocatalytic TiO2 films by oxygen-ion-assisted reactive evaporation (OIARE). All the films deposited at room temperature without oxygen ion acceleration, however, have an amorphous structure. To promote the crystallization of TiO2 film, the acceleration of oxygen ions in the range from 0 to 1000 eV was attempted during film deposition. As a result, it was found that the increase in the acceleration voltage promotes the crystallization of the films, so that the film with anatase and/or rutile structure was able to be obtained at room temperature under the condition at avacceleration voltage above 600 eV. Further increase in the acceleration voltage leads to a crystal formation with rutile structure. These results indicate that the OIARE using highly accelerated oxygen ions is useful to obtaining crystallized TiO2 films at room temperature. The photoinduced hydrophilicity performance (contact angle of water droplet) and decomposition performance of methylen eblue were improved following the crystallization of the films, although the decomposition performance index of the crystallized film still has a small value in the range of 1.4–2.0 µmol·l-1·min-1. This result indicates that the improvement of the photocatalytic performance of the TiO2 films deposited at room temperature is necessary for their practical use.