Photocatalytic TiO2 thin film deposited onto glass by DC magnetron sputtering

A high performance photocatalytic TiO2 thin film was successfully obtained by reactive DC magnetron sputtering. The film was deposited onto SiO2-coate d glass at a substrate temperature of 220 degreesC using a titanium metal t arget in O-2 100% atmosphere. The film showed good uniformity of thickness in a large area with the optical transmittance of similar to 80% in the vis ible region. The decomposition ability of acetaldehyde (CH3CHO) of the film under UV irradiation was almost the same as that of the sol-gel-derived Ti O2 thin film but the sputtered film showed a much higher mechanical durabil ity. The characterization of the films was carried out using XRD, SEM, AFM, XPS and SIMS, and the electronic structures of the films were calculated u sing a first-principle calculation method based on the density functional t heory. It was found that the amount of incorporated O-18 into the film was larger for the films with lower photocatalytic activity when the films were annealed in O-18(2)/N-2 atmosphere. This result indicates that the amount of oxygen vacancies, which were occupied by incorporated O-18, was larger f or the films with lower photocatalytic activity. Furthermore, the introduct ion of structural defects associated with oxygen vacancies was found to cre ate some energy levels around the mid-gap, indicating that they could work as recombination centers of photo-induced holes and electrons, causing the decrease in photocatalytic activity. Therefore, the decrease in the structu ral defects associated with oxygen vacancies is important for improving the photocatalytic activity of the films. (C) 2001 Elsevier Science B.V. All r ights reserved.