Fabrication of N-doped TiO2 thin films by laser ablation method: Mechanism of N-doping and evaluation of the thin films

N-doped TiO2 thin films were prepared by the laser ablation method under an N2 gas atmosphere. Properties of the films such as color, the relative amount of N doped and the crystal structure strongly depended on substrate temperature and N2 gas pressure. XPS data indicated that the amount of doped N unexpectedly increases with decreasing N2 gas pressure in the range of ca. 40–270 Pa. We proposed that the N-doping occurred when N species and TiO2 particles collide on the substrate. The decomposition of methylene blue using the N-doped TiO2 thin film was also performed under visible light irradiation.