Influence of Nb content on the structural and optical properties of anatase TiO2 polycrystalline thin film by e-beam technique

In this paper, we report the structural and optical properties of Nb-doped TiO2 thin films deposited by e-beam evaporation technique. After post annealing in air at 500 °C for 1 h, the samples were characterized by various techniques such as X-ray diffraction (XRD), Raman spectroscopy, UV-Vis spectrophotometry and spectroscopic Ellipsometer. Both XRD and Raman analyses indicate that the films were crystallized into the polycrystalline anatase TiO2 structure. However it was observed that the crystallinity of the films decreases with the addition of Nb atoms and tends to become amorphous at 20% Nb content in TiO2 film. Moreover, no new phases such as Nb2O5, NbO2 or Nb metal were observed. The band gap energy was found to decrease with the increasing of Nb concentration which was verified by ellipsometric study. Ellipsomtric measurements also indicate that refractive index (n) of the films decreases while extinction coefficient (k) increases with the increasing of Nb content. All these analyses elucidate that the incorporation of Nb atom into TiO2 may tune the structural and optical properties of TiO2 thin films.