Paper SS-TuP27
Photo-functional Properties of Cu-Added Titanium Dioxide Thin Films Prepared by Reactive Magnetron Sputtering

Tuesday, November 1, 2011, 6:00 pm, Room East Exhibit Hall

TiO₂ has been known as one of a promising photocatalyst and is already used in various practical applications, such as the degradation of environmental pollutants and the self cleaning of glasses. Furthermore, the surface of TiO₂ exhibits high hydrophilicity under ultra-violet (UV) light irradiation. A crystal form of TiO₂ is classified according to structure as anatase, ruttile and brookite. TiO₂ shows relatively high reactivity and chemical stability under UV light whose energy exceeds the band gap of 3.2eV in the anatase crystalline phase. The sun can provide an abundant source of photons. However, UV energy accounts for only a small fraction (~5%) of the sun’^’s energy compared to the visible region (45%). Many techniques have been examined to improve this problem by the doping of transition metals into TiO₂.

In this study, TiO₂ films were prepared by reactive magnetron sputtering using a Ti target in an Ar/O₂ gas mixture. Cu addition was performed by Cu sputtering onto those TiO₂ films. It was considered that the charge separation between an electron and a hole was improved by adding Cu to the TiO₂ surface. 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 a photocatalytic property. Light irradiation to TiO₂ films in a methylene blue solution was carried out by using a commercial sterilizing lamp as ultraviolet light and an artificial sun light as visible light. Transmittance of a methylene blue solution was measured by a spectrophotometer. Furthermore, photocurrent between the TiO₂ film and a platinum electrode was measured by a volt-ampere characteristic using an unresisted ammeter in a KCl solution of 0.5 mol/ℓ.

The crystal structure of TiO₂ turned from a rutile type into an anatase type with increase of O₂ gas flow rate. Photocatalytic property and photocurrent property of an anatase type of TiO₂ showed the high value. The effect of the Cu addition exhibited different behavior according to each crystal structure. As for the photocatalytic property, the effect of the Cu addition was observed in rutile type, while on the photocurrent property the effect of the Cu addition was observed in anatase type. It was considered that the charge separation between an electron and a hole was enhanced by adding Cu to the TiO₂ surface.