The epitaxial growths of titanium dioxide (TiO2) thin films were prepared by pulsed laser deposition. The dependencies of the crystalline structure of prepared films upon buffer O-2 gas pressure, laser power and substrate were studied. The crystalline structures were found by the X-ray diffraction method to be a mixture of rutile and anatase on alpha-Al2O3, and anatase on LaAlO3. The crystallite sizes were calculated to be about 10 nm by applying the Scherrer equation to the diffraction peaks. The sizes were increased by collisions between evaporated particles and O-2. The growth of mixed crystal is caused by the competitive process between lattice misfit-induced epitaxy and thermodynamic stability. (c) 2006 Elsevier B.V. All rights reserved.