| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2016) | |
| Thin Films | Wednesday Sessions |
| Session TF-WeP |
| Session: | Thin Films Posters Session II |
| Presenter: | Toshiya Souma, Kogakuin University, Japan |
| Authors: | T. Souma, Kogakuin University, Japan I. Takano, Kogakuin University, Japan |
| Correspondent: | Click to Email |
In recent years, various characteristics of TiO2 have attracted considerable attention. One of their characteristics is a photocatalytic effect. The photocatalytic effect of TiO2 shows antifouling or antimicrobial activity, and has the ability to decompose environmental pollutants. The most important characteristic as a photocatalysis of TiO2 is well known that the photo-excited state is very stable and does not cause self-decomposition. Therefore, TiO2 can perform the electrolysis of water by light, however a light reaction of TiO2 is limited at ultraviolet region corresponded with only about 3 % of sunlight.
In this study, to improve the photocatalytic 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. In order to prevent the diffusion of Cu, an NiO or TaON layer was inserted between the TiO2 layer and the Cu2O layer. NiO has a high melting point, high hardness and has been used as a barrier layer in various fields. TaON is used as electrode materials for a semiconductor and light electronics devices. Each oxide layer was prepared by reactive magnetron sputtering.
The film composition and microstructure were investigated by the X-ray photoelectron spectroscopy and X-ray diffraction, respectively. The chromatic change of a methylene blue solution was applied to the measurement of the photocatalytic property. The light irradiation to the TiO2/NiO/Cu2O film or the TiO2/TaON/Cu2O film in a methylene blue solution was carried out using a commercial sterilizing lamp as ultraviolet light and an artificial sun lamp as visible light. The transmittance of a methylene blue solution was measured by a spectrophotometer.
It was confirmed that Cu on the TiO2 surface was not observed by inserting the NiO or the TaON layer. The crystal structure of the TiO2/Cu2O film showed a rutile type while the ratio of rutile (110) / anatase (101) changed with the NiO film thickness. In the case of the intermediate layer of NiO, the suitable photocatalytic effect was obtained by the film with the NiO layer of 20 nm thickness, when the transmittance showed about 57 % under an artificial sun lamp and about 77 % under a sterilization lamp. In the case of the TaON layer, the suitable photocatalytic effect was obtained by the TaON layer of 10 nm thickness, when the transmittance showed about 75 % under an artificial sun lamp and about 82 % under a sterilization lamp.
It is considered that the role of the intermediate layer is not only the protection of Cu diffusion from the Cu2O layer but also the activation of the mobility of carriers.