Synthesis of anatase TiO2 with thickness of ten nanometers, and improvement of its photo-catalytic property by nitrogen ion irradiation

RF sputtered titanium thin films with 200–800 nm thickness were deposited on Si(100) substrates. Titanium oxide films were synthesized by a thermal annealing in oxygen at 300–600 °C. These titanium oxides were characterized by GA-XRD, XPS and TEM. The photo-catalytic property of TiO2 was evaluated by the bleaching method of methylene blue solution with a concentration of 10 μmol/l. ickness of anatase TiO2 was estimated to be about 13 nm by TEM. After irradiation by UV light for 3 h, the specimen bleached the methylene blue solution. When a visible blue LED was used as the light source instead of UV light, the bleaching process was not observed at all. On the other hand, for specimens which had been irradiated by nitrogen ions at relatively low energies such as several hundred eV, the methylene blue solution was bleached even for the visible blue LED light source. XPS analyses indicated that the N concentration within the specimen was about 20 at.%. It is concluded that 13 nm thick anatase TiO2 has good photo-catalytic performance, and that the addition of nitrogen results in improvement of the photo-catalytic reaction in the region of visible light.