Effect of the nitrogen-oxygen ratio on the position of N atoms in the TiO2 lattice of N-doped TiO2 thin films prepared by DC magnetron sputtering

The nitrogen-doped TiO2 thin films are deposited on the glass substrate by using a direct-current (DC) magnetron sputtering technique. The film properties are analyzed by X-ray diffraction (XRD), atomic force microscopy (AFM), UV-vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) measurements. The results show that, under the same working pressure and other conditions, nitrogen doping promotes the phase transition from anatase to rutile. Also, on changing the nitrogen-oxygen ratio, nitrogen atoms enter the TiO2 lattice in different positions. When oxygen is abundant, nitrogen atoms will be presented in the interstitial positions; when oxygen is insufficient, nitrogen atoms enter the oxygen vacancies first, forming a substituted position. Finally, we find that, with the increase in nitrogen-oxygen ratio, the sample has a better response to visible light, attributed to the change in the energy band-gap.