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In reactive sputtering with pure metal target, it is very difficult to deposit metallic oxide or metallic nitride films with good crystallinity on substrates with low temperature because the metal-gas reactions may not take place in the space between target and substrate, but may mostly take place on the surface of the substrate. In this study, nitrogen doped TiO2 films were deposited on no heating glass substrates using sputtering. 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 substrate temperature gradually increases from room temperature to about 100 °C during deposition due to plasma emission. The crystal structure of films was estimated from XRD and Raman spectroscopy 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. Its crystallinity becomes worse with increasing nitrogen gas flow rate, while those films have lower and broader Raman shift peaks. This change in the Raman peak intensity may be closely related to the change of the film crystallinity and composition. The band gap energy was found to decrease from 3.2 to 2.9 eV for the increase of nitrogen gas flow rate. The lowest band gap of 2.9 eV was observed for the films deposited at 20 ccm nitrogen flow rate. To improve the film crystallinity, samples are heated for 2 hours at 400 °C in an electric furnace for a reaction with oxygen that is left there with air. After annealing, the samples have better crystallinity and high and narrow Raman shift peaks and the band gap energy was found to be about 3.1 eV for all the films. Consequently, the crystallinity of films with higher nitrogen doped amount was significantly improved and the band gap energy of films approached that of TiO2 anatase phase by annealing in air. This may be due to the substitution of nitrogen with oxygen. |