Paper SS-TuP6
The Influence of the Magnetic Field on the Photo-Functional Property of TiO₂/Ni/TiO₂ Thin Films Prepared by Sputtering

Tuesday, October 30, 2012, 6:00 pm, Room Central Hall

Since the photoinduced decomposition of water on TiO₂electrodes were discovered, various characteristics based on photocatalyst have attracted extensive interest. TiO₂ is anticipated as one of materials which are alternative for an existing solar cell based on silicon. TiO₂ shows relatively high reactivity and chemical stability under UV light whose energy exceeds a band gap of 3.2 eV in the anatase crystalline phase. The sun can provide an abundant source of photons, however, UV light accounts for the only small fraction (5 %) of the sun’s energy compared to the visible region (45 %). Many techniques have been examined to achieve this purpose.

In this study, the glass (Corning#1737) was used as the substrate. After the TiO₂ layer was prepared by reactive magnetron sputtering using a Ti target in an Ar/O₂ gas mixture, the Ni layer was deposited by using DC sputtering. Finally the TiO₂ layer was coated on the Ni layer. The TiO₂/Ni/TiO₂ multi-layer films were constituted with the first TiO₂ layer of 100 - 200 nm, second Ni layer of 25 nm and the third TiO₂ surface layer of 0 - 100 nm. Composition and microstructure of these films were investigated by X-ray photoelectron spectroscopy and X-ray diffraction, respectively. Chromatic change of a methylene blue solution was applied to photocatalytic evaluation. Light irradiation to TiO₂ films in a methylene blue solution was carried out using a commercial sterilizing lamp as ultraviolet light and an artificial sun lamp as visible light. Transmittance of a methylene blue solution was measured by a spectrophotometer. In this experiment the relationship between the photocatalytic effect and the magnetic field was investigated. Magnets with magnetic field intensity of 0.15 - 0.23 T were placed on the outside of a methylene blue cell. We anticipated that the magnetic field affected separation of an electron and a hole.

The XRD patterns of TiO₂ prepared by reactive magnetron sputtering showed anatase (101) and rutile (110) of TiO₂. The anatase content for the crystal structure of the TiO₂ was 82 %. When the magnetic field was applied in the parallel direction to the substrate surface, the TiO₂/Ni/TiO₂ thin film with the thinner TiO₂ surface layer, i.e. the third layer of 50 nm, showed the higher photocatalytic property. It was clear that the magnetic field affected a photocatalytic property.