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Titanium (Ti) is a popular and low cost metal with an abundant resource as well as silicon and iron in the world. Its oxide film is used as optical film with high refractive index, photocatalytic film with highly decomposed organic compounds or dye sensitized solar cell may replace p-n junction solar cell. On the other hand, its nitride film is used as wear-resistant hard coating film. In this study, to obtain the basic data concerned with transition mechanism from TiO2 to TiN, nitrogen doped TiO2 films were prepared on glass substrates by DC reactive facing targets sputtering using Ti target. After the chamber was enough evacuated, oxygen was introduced at gas flow rate of 3 ccm. Subsequently, nitrogen was introduced at gas flow rate of 0 to 20 ccm. Finally, the sputtering pressure was fixed at 0.8 Pa introducing argon. The crystal structure and surface morphology of films were estimated from XRD, Raman spectroscopy and FE-SEM measurements. The films deposited at nitrogen gas flow rate ranging from 0 to 10 ccm were found be in a mixture of the anatase and rutile phase. However, the anatase phase is dominated for all the films. When the films were deposited at nitrogen gas flow rate of 15 and 20 ccm, they showed bad crystalline anatase phase and amorphous, respectively. The crystallinity of nitrogen doped films becomes worse with increasing nitrogen gas flow rate. The anatase phase of films was revealed in the Raman spectra with a Raman shift of 640 cm-1. The nitrogen no doped films have the highest Raman shift peaks, while those films have lower and broader Raman shift peaks with increasing nitrogen gas flow rate. This change in the Raman peak intensity may be closely related to the change of the film crystallinity and composition. The grain size of films increases with an increase of nitrogen gas flow rate. The optical absorption edge of films shifted toward visible light wavelength and the band gap energy was found to decrease from 3.2 to 2.9 eV for an increase of nitrogen gas flow rate. The lowest band gap was observed for the films deposited at 20 ccm nitrogen flow rate. Consequently, the structure and properties of TiO2 films significantly depended on nitrogen doping amount. |