TiO2 thin film was deposited on non-heated Si(1 0 0) substrate by RF magnetron sputtering. The as-deposited films were annealed by a conventional thermal annealing (CTA) and rapid thermal annealing (RTA) at 700 and 800 degrees C, and the effects of annealing temperature and method on optical properties of studied films were investigated by measuring the optical band gaps and FT-IR spectra. And we also compared the XRD patterns of the studied samples. The as-deposited film showed a mixed structure of anatase and brookite. Only rutile structures were found in samples annealed above 800 degrees C by CTA, while there are no special peaks except the weak brookite B(2 3 2) peak for the sample annealed at (or above) 800 degrees C by RTA. Fr-IR spectra show the broad peaks due to Ti-O vibration mode in the range of 590-620 cm(-1) for the as-deposited film as well as samples annealed by both annealing methods at 700 degrees C. The studied samples all had the peaks from Si-O vibration mode, which seemed to be due to the reaction between TiO2, and Si substrate, and the intensities of these peaks increased with increasing of annealing temperature. The optical band gap of the as-deposited film was 3.29 eV but it varied from 3.39 to 3.43 eV as the annealing temperature increased from 700 to 800 degrees C in the samples annealed by CTA. However, it varied from 3.38 to 3.32 eV as the annealing temperature increased from 700 to 800 degrees C by RTA. (c) 2006 Elsevier B.V. All rights reserved.