| AVS 56th International Symposium & Exhibition | |
| Thin Film | Thursday Sessions |
| Session TF-ThP |
| Session: | Aspects of Thin Films Poster Session |
| Presenter: | H. Shukur, Kogakuin University, Japan |
| Authors: | H. Shukur, Kogakuin University, Japan K. Komiyama, Kogakuin University, Japan M. Sato, Kogakuin University, Japan I. Takano, Kogakuin University, Japan |
| Correspondent: | Click to Email |
TiO2 as photo-functional material is one of lower cost material and harmless material to environment. It is expected to use as material of clean energy in future. Furthermore the photocatalytic property provides antibacterial or antifouling effect. These effects decompose environmental pollution matters (like nitrogen oxide etc.) by generate active oxygen (O2-, OH), when TiO2 is exposed to sunlight. On the other hand, TiO2 has characteristically electrical properties such as an n-type semiconductor or a dielectric. In order to improve the electrical and photocatalytic property of TiO2, many researchers have used various methods such as gas or metal doping into TiO2 techniques etc. In this study, tungsten (W) was doped to TiO2 thin film to improve the electrical properties and to enhance the photo-sensitivity of TiO2 thin film. The doping of W in TiO2 thin film generates tungsten oxide (WO3) and this oxide shifts the conduction band of TiO2 to the positive side because of the low band gap of WO3 (2.8eV) as compared with that of TiO2 (3.2eV). As a result, because the motion energy of each electron becomes smaller, excited electrons in a visible region (wavelength more than 400 nm) increase and promote the photocatalytic reaction in this region.
TiO2 thin films were prepared by using the reactive magnetron sputtering method on stainless steel substrate (SUS304) of 18×18 mm in size and also glass substrate of 18×9 mm in size. All samples were formed in four layers. The first one was a Ti layer with 50 nm in thickness. The second layer was a TiO2 layer of 170 nm. The third layer and surface layer were W-doped TiO2 of 30 nm and TiO2 of 10 - 60 nm, respectively. Other formation conditions were 1.1 sccm in O2 gas flow rate and 20 sccm in Ar gas flow rate. Ti and W sputtering rate were fixed at 0.025 nm/sec and 0.002nm/sec, respectively. The substrate temperature through this formation process was set at 200 oC.
The photocatalytic property was measured by a methylene blue immersion test. The difference in light absorbance at a wave length of 665 nm after light irradiation for 12 hours using sterilization, fluorescent and an artificial sunlight lamp (with UV band filter) was measured by a spectrophotometer (SHIMADZU UV-2550). Photoelectric current was measured by a cyclic volt ammeter system.
The photo-functional properties of W-doped TiO2 were improved by the additional TiO2 onto the W-doped TiO2 layer. Photocatalytic property showed a higher value under artificial sunlight irradiation when the surface layer thickness was 20 nm.