The synthesis of semiconducting TiO2 thin films deposited by reactive sputtering is discussed. In particular, defect doping of the anatase polymorph that is epitaxial stabilized on (0 0 1) LaAlO3 was explored using either oxygen or water vapor as the oxidizing species. For films grown in oxygen, a transition from insulating to metallic conductivity of the films is observed as the O-2 pressure is reduced. X-ray diffraction measurements show the presence of the TinO2n-1 phase when the oxygen pressure is reduced sufficiently to induce conductive behavior. Hall measurements indicate that these materials are p-type. In contrast, the use of water vapor as the oxidizing species enabled the formation of n-type semiconducting TiO2 with carrier density on the order of 10(18) cm(-3) and mobility of 10-15 cm(2)/V s. (C) 2003 Elsevier Ltd. All rights reserved.