AVS 54th International Symposium
    Advanced Surface Engineering Tuesday Sessions
       Session SE-TuP

Paper SE-TuP3
High Rate Deposition of Photocatalytic TiO2 Films with High Activity by Hollow Cathode Gas-Flow Sputtering

Tuesday, October 16, 2007, 6:00 pm, Room 4C

Session: Advanced Surface Engineering Poster Session
Presenter: Y. Kubo, Aoyama Gakuin University, Japan
Authors: Y. Kubo, Aoyama Gakuin University, Japan
Y. Iwabuchi, Bridgestone Co., Japan
M. Yoshikawa, Bridgestone Co., Japan
Y. Sato, Aoyama Gakuin University, Japan
Y. Shigesato, Aoyama Gakuin University, Japan
Correspondent: Click to Email

Titanium dioxide (TiO2) has been well known as a photocatalyst because of the strong oxidizing power of photo-generated holes. Reactive sputter depositions using a Ti metal target should be one of the most promising techniques for uniform coatings in large area with high packing density and strong adhesion. However, the deposition rate is very small of 2~5 nm/min for the conventional reactive magnetron sputtering to deposit fully oxidized TiO2 films because the films should be deposited at the "oxide mode" where the target surface is oxidized and the sputtering yield is very smal.1 In order for the high deposition rate of 30~90 nm/min, we have been reported on dual cathode sputtering system2 or unipolor pulsing system3 with plasma emission control systems2-3. As the much simpler and lower cost system, TiO2 films were deposited on unheated alkali-free glass substrates by gas-flow sputtering using two Ti metal targets which were mounted parallel with each other. Ar (sputtering gas) was supplied between these two targets.O2 (reactive gas) was supplied in the vicinity of the substrate. Ar and O2 flows were 3.0 SLM and 10~50 sccm, respectively, and total gas pressure during the depositions was maintained at 45 Pa. In such pressure mean free path of gas atoms is very small and a gas flow is in viscous regime, that is why the process has been named gas-flow sputtering.4 The photocatalytic activity was evaluated by photo-decomposition of acetaldehyde and contact angle for water after UV illumination (black light lamp, 0.4 mW/cm2). Both of the as-deposited films and the post-annealed films at 300 °C in air performed the photocatalytic decomposition. Especially the post-annealed films performed extremely high photocatalytic activities. The highest deposition rate to deposit such photocatalytic TiO2 films were 162 nm/min.

1 M. Yamagishi, S. Kuriki, P. K. Song and Y. Shigesato, Thin Solid Films, 442 (2003) 227.
2 S. Ohno, D. Sato, M. Kon, Y. Sato, M. Yoshikawa, P. Frach, Y. Shigesato, Jpn. J. Appl. Phys., Vol. 43, No.12 (2004) 8234.
3 S. Ohno, N. Takasawa, Y. Sato, M. Yoshikawa, K. Suzuki, P. Frach and Y. Shigesato, Thin Solid Films 496 (2006) 126.
4 K. Ishii, J. Vac. Sci. Technol., A7 (1989) 256.