Characterization and visible light germicidal efficacy of nitrogen doped TiO2 film crystallized by microwave irradiations

The visible light bactericidal ability of nitrogen doped TiO2 (TiON) film on Si (100) has been enhanced greatly (by 22%) through a single-mode microwave irradiation annealing (f = 2.45 GHz, 20 s) in comparison with the conventional heat treatment at the same temperature (500 °C, 300 s). Analyses of X-ray photoelectron spectroscopy and transmission electron microscopy showed that the microwave annealed TiON film had a higher nitrogen concentration and much better crystallinity, both of which contribute to its prior bactericidal ability under visible light. The optimized annealing parameters of microwave irradiation are 500 °C within 20 s. Increase of annealing temperature and irradiation time resulted in the decrease of nitrogen concentration within the film. The crystallized TiON film has an anatase but not a rutile structure at the annealing temperature up to 800 °C.