Characterization of Ni-doped TiO2 thin films deposited by dip-coating technique

Undoped and Ni-doped TiO 2 thin films have been prepared by sol-gel dip-coating method on glass and silicon substrates. X-ray diffraction studies show that both TiO 2 and Ni-doped TiO 2 thin films are of anatase phase with (1 0 1) as preferential orientation. From the UV-visible spectroscopy analysis, all films exhibits a high transparency ~ 80% and shows that the optical band gap decreases from 3.66 to 3.59 eV, which may be related with the phase composition and impurities. Fourier transformed infrared spectroscopy (FTIR) study confirms the presence of Ti-O, Ti=O and O-H bands. Thermal analysis by differential scanning calorimetriy (DSC) shows endothermic reactions between 30 °C and 280 °C and exothermic reactions between 370 °C and 540 °C corresponding to the crystallization of TiO 2 in the anatase phase. The Nyquist plots suggests that the equivalent circuit of the films is an R p C p parallel circuit and shows an increase in resistance R p with increasing the Ni concentration and a decrease in capacity C p .