Conductivity in transparent anatase TiO2 films epitaxially grown by reactive sputtering deposition

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.