Paper SS-TuP7
Photo-function Property of TiO₂/Cu₂O Thin Films by Reactive Magnetron Sputtering

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

Characteristics based on photo-inducement of TiO₂ have attracted various interests in many fields. One of those characteristics is a photocatalytic effect. The photocatalytic effect shows antifouling or antimicrobial activity and also has the ability to decompose environmental pollutants. The most important characteristic as a photocatalyst of TiO₂ is well known that photo-excited state is very stable and does not cause self-decomposition. Therefore, the electrolysis of water is performed under ultraviolet irradiation to TiO₂. However the light reaction region of TiO₂ is limited at ultraviolet region corresponded with only about 3 % of sunlight.

In this study, to improve the photo-function property of TiO2 the double layer films were fabricated by the constitution of the TiO₂ layer with 3.0 - 3.2 eV and the Cu₂O layer with 2.2 eV in a band gap energy. Each constitution of the film with TiO₂/Cu₂O and Cu₂O/TiO₂ was also investigated about optical permeability. Furthermore, to prevent diffusion of Cu from the Cu₂O layer to the TiO₂ layer, the TiN layer was inserted between the TiO₂ layer and the Cu₂O layer. TiN has a high melting point, stability and the suitable electric property as a barrier layer. Those TiO₂/Cu₂O and TiN were fabricated by reactive magnetron sputtering. 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 for the photocatalytic evaluation. Light irradiation to the sample 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 after irradiation for 6 hours by each lamp.

The XRD pattern of the TiO₂/Cu₂O thin film showed the strong peak of the anatase-rutile TiO from an upper layer and the weak peak of Cu₂O from lower layer. The suitable photocatalytic effect was obtained by the constitution of TiO2 with 300 nm and Cu₂O with 200 nm in thickness, when the photocatalytic effect showed about 31 % under an artificial sun lamp and about 90 % under a sterilization lamp. In the case of the TiO₂/ TiN /Cu₂O film it was estimated that the diffusion of Cu was prevented by inserting TiN from the XRD pattern, however, the high photocatalytic effect was not obtained. It was considered that the photocatalytic effect depended on thickness of the TiN layer.