Laser ablation of TiO_(2-2x)N_x targets for efficient N-doping into Anatase TiO2 photo-catalytic films

摘要

Among the well-known photo-catalytic materials, the anatase TiO2 is the most promising in terms of its chemical stability and high reactivity. It is known that the photo-catalytic activity under the visible light irradiation can be enhanced by nitrogen doping into the anatase, because the substitutional nitrogen produces an impurity state which absorbs the visible light. In this paper, we will report on the properties of the nitrogen doped films with different dopant concentrations. The anatase films are prepared by KrF excimer pulsed-laser ablation of TiO2-xNx targets. The films are deposited on the (100) LaAlO3 substrate which has a good lattice matching with anatase (~ 0.2%). First, we discuss the optimization of the growth conditions. To prepare the nitrogen doped anatase thin films, we have developed a lowtemperature epitaxy. The growth of anatase-type TiO2 was confirmed using an x-ray diffraction (XRD). The nitrogen incorporation was evaluated by an x-ray photoemission spectroscopy (XPS). The as-grown films have very smooth surface and exhibit good amphiphilic properties. Then, we present the photo-catalytic activity of the films. The nitrogen doping concentration was varied by adjusting the amount of nitrogen in the ablation targets. The photo-catalytic activity was measured by the decomposition rate of methylene blue solution under a fluorescent light illumination.