Effect of N2 flow rate on the properties of N doped TiO2 films deposited by DC coupled RF magnetron sputtering

•N doped TiO2 films were deposited by DC coupled RF magnetron reactive sputtering.•As N2 flow rate increases, the crystallization of the deposited films degrades.•The higher N2 flow rate is beneficial to form more substituted N in the film.•N doping causes an obvious red shift in the absorption wavelength.

N doped TiO2 films were deposited on glass substrates at room temperature using DC coupled RF magnetron sputtering with a TiO2 ceramic target. The influences of N2 flow rate on the deposition rate, crystal structure, chemical composition and band gap of the deposited films were investigated by Optical profiler, X-ray diffraction, X-ray photoelectron spectroscope and ultraviolet-visible spectrophotometer. The film growth rate gradually decreased with increasing N2 flow rate. As N2 flow rate increased, the crystallization of the films deteriorated, and the films tended to form amorphous structure. XPS analysis revealed that N dopant atoms were added at the substitutional sites into TiO2 lattice structure. FE-SEM results showed that the grain size of the film decreased and the crystallinity degraded as N2 flow rate increases. In addition, N doping caused an obvious red shift in the optical absorption edge.

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