Conductivity in transparent anatase TiO_2 films epitaxially grown by reactive sputtering deposition

摘要

The synthesis of semiconducting TiO_2 thin films deposited by reactive sputtering is discussed. In particular, defect doping of the anatase polymorph that is epitaxial stabilized on (001) LaAlO_3 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 Ti_nO_(2n-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 TiO_2 with carrier density on the order of 10~(18) cm~(-3) and mobility of 10-15 cm~2/V s.