TiO2 thin films were deposited on MgO substrates by reactive RF magnetron sputtering using oxygen radicals. In order to perform the low temperature crystallization and control of crystal structure, the TiO2 thin film was irradiated by highly reactive oxygen radicals during the deposition. When the distance between the substrate and Ti-metal target (S-T distance) was 90 mm and substrate temperature were kept at 125 degrees C, the radical irradiated TiO2 film exhibited a (1 10) orientation with rutile structure. The radical irradiated TiO2 thin film prepared at 300 degrees C was changed from rutile to anatase structure by the adjustment of S-T distance. When the S-T distance was fixed at 110 mm, the TiO2 film exhibited a high a-axis orientation with anatase structure. The TiO2 rutile and anatase thin films consisted of small grains with very smooth surface. (c) 2006 Elsevier B.V. All rights reserved.