TiO2, which is high in refractive index and dielectric constant, plays an important role in the fields of optics and electronics. In this work, TiO2 films were prepared on glass substrates by the technique of ion beam assisted electron beam evaporation. The films were deposited at 50, 150 and 300 degrees C, respectively. Then the as-deposited TiO2 films were annealed at 450 degrees C for 1 h in vacuum atmosphere. Structures and optical properties of TiO2 films were characterized by XRD, SEM, ellipsometry and spectrophotometer. As a result, the structure and the refractive index of films were improved by both the annealing and the increasing of the deposition temperature. The UV- vis transmittance spectra also confirmed that the deposition temperature has a significant effect on the transparency of the thin films. The highest transparency over the visible wavelength region of spectra was obtained at the deposition temperature of 300 degrees C. The allowed direct band gap at the deposition temperature ranging from 50 to 300 degrees C was estimated to be in the range from 3.81 to 3.92 eV. (C) 2007 Elsevier B. V. All rights reserved.