Effect of annealing temperature on optical properties of titanium dioxide thin films prepared by sol-gel method

摘要

TiO _2 sol-gel thin films were deposited on glass substrates by dip coating method. Nanocrystalline TiO _2 thin films were prepared at 300°C. The effect of annealing temperature on optical properties of nanocrystalline TiO _2 thin films was studied. The films were characterized by different techniques: XRD, UV-visible spectroscopy, FTIR spectroscopy and FESEM. The characterization studies revealed that the films are crystallized as anatase phase and are nano-structured. The optical measurements were showed the indirect band gap between 3.31 and 3.35 eV with corresponding crystallite sizes between 8.9 and 3.7 nm at the temperatures 300, 400 and 500°C. The FESEM images of film were showed spherical nanocrystalline structure of TiO _2 particles with the crystallite sizes between 30 and 100 nm. It is also observed that refractive index of the film increases with increasing the annealing temperature. The smaller crystallite size gives larger band gap due to quantum size effects.