Paper SE1-MoM6
Micro-Structure of Photo-Catalytic TiO₂ Films Deposited by Oxygen Ion Assist Reactive Evaporation Method and Reactive Sputtering

Monday, November 9, 2009, 10:00 am, Room B1

TiO₂ films were deposited on glass slide substrates by using oxygen ion assist reactive evaporation method(IARE) and reactive sputtering method(RS), and their micro-structure was investigated by using FE-TEM.

The films of above 1um thick deposited by IARE at the substrate temperature of 300 ℃ and ion accelerating voltage of 200 V has excellent photo-catalytic properties. However, the films with thickness lower than 1um shows poor photo-catalytic properties. In these films, the crystallization in the initial layer on the substrate was suppressed so that the film near the substrate contains large amount of amorphous phase. As the film grew, crystallization was enhanced and clear columnar structure was developed in the films. As a result, most of the amorphous phase was disappeared at the thickness above 600 nm. In addition, the column were separated each other with clear spaces at the thickness above 800 nm. This may be the reason why the photocatalytic properties improved significantly as the film thickness increased above 1um. These results suggest that the poor crystal structure is the main reason why the film with thickness below 800nm has poor photo-catalytic properties.

On the other hand, compared with the films deposited by IARE, crystallization was enhanced in the deposition of the films by using a reactive sputtering. As a result, crystallized film with thickness below 200 nm can be obtained at 300 ℃. This may be due to the fact that the depositing atoms in the sputtering process have much larger kinetic energy than in IARE. The film, however, has much dense structure and smooth surfaces, which results in a poor photo-catalytic organic decomposition properties.