Optical and structural properties of TiO2 films as a function of Nb doping concentration

Ti1–x Nb x O2 (x = 0–0.06) films were prepared on quartz substrates by sol–gel spin coating and characterized by a variety techniques. The effect of Nb doping on the structural and optical properties of Ti1–x Nb x O2 films were mainly investigated by X-Ray diffraction (XRD), Raman spectroscopy, Field-emission scanning electron microscopy and UV–vis transmittance spectroscopy. XRD and Raman study showed that the Nb doping inhibited the grain growth. The grain size decreased from 39.4 to 23.4 nm as the doping concentration increased from 0 to 0.06 in atomic percent. The UV–vis transmittance spectroscopy analysis revealed that the films exhibited 55–65% transmittance in the visible region and the band gap of films became wider with increasing Nb doping concentration.