AVS 49th International Symposium
    Thin Films Wednesday Sessions
       Session TF-WeP

Paper TF-WeP15
Influence of Preparation Conditions on Structure and Properties of WO@sub3@Films Reactively Deposited by RF Magnetron Sputtering

Wednesday, November 6, 2002, 11:00 am, Room Exhibit Hall B2

Session: Poster Session
Presenter: J. Tanabe, Toyama University, Japan
Authors: T. Takahashi, Toyama University, Japan
J. Tanabe, Toyama University, Japan
H. Nakabayashi, Toyama University, Japan
N. Yamada, Toyama University, Japan
Correspondent: Click to Email
TiO@sub2@ photocatalyst can only react slightly to solar energy because of its optical band gap E@subG@ smaller than 3.2 eV (@lambda@ of 380 nm). So, it is desirable for most solar energy applications to have new materials that can highly react strongly to visible-light . Therefore, WO@sub3@ films with E@subG@ of 2.5 eV are very useful for the underlayer of TiO@sub2@ photocatalyst. In this study, WO@sub3@ films with thickness of 0.9-6.7 µm have been deposited on glass-slide substrates, using RF magnetron sputtering in an atmosphere of mixture gas of 80%Ar and 20%O@sub2@. The crystallographic and the surface structures and the optical properties of WO@sub3@ films deposited at the working gas pressure P@subW@ ranging from 1 to 8 mTorr have been investigated in detail. The as-deposited films showed dark metallic color as like as target at P@subW@ of 1 mTorr. The as-deposited films were yellow at P@subW@ of 3 mTorr. With further increase of P@subW@, the color of the films changed to pale yellow. From the X-ray diffraction patterns, the as-deposited films were polycrystalline crystallizing in the monoclinic or the triclinic crystal structure with high c-axis orientation perpendicular to the film plane. The optical transmittance of the films deposited at P@subW@ of 1 mTorr is nearly zero. However, the transmittance of the films deposited at other P@subW@ are larger than 70 % in the wavelength @lambda@ ranging from 500 to 900 nm. With decreasing @lambda@ to 400 nm, the transmittance steeply become zero. The @lambda@ at this absorption edge is longer than that in TiO@sub2@ and comes in the visible region. The surface morphology of the films depends on P@subW@. As P@subW@ increased, the surfaces of the films become rougher and grain sizes of the films also become larger. The WO@sub3@ films deposited in this study may be available for the underlayer of TiO@sub2@ photocatalyst.