Highly Reduced Anatase TiO2-δ Thin Films Obtained via Low-Temperature Reduction

We report the preparation and physical properties of reduced anatase TiO2-delta thin films obtained via a low-temperature (low-T) reduction using CaH2. The oxygen amounts were controlled in a wider range than ever reported. Some highly reduced anatase films showed resistivities as low as 10(-3) Omega cm at room temperature, both in metallic and semiconducting states. The most conducting metallic sample has very high carrier concentration of 1.6 x 10(21) cm(-3), comparable with those of metal-doped anatase films. Moreover, the magnetoresistance of the films changed its sign twice as a function of delta. (C) 2011 The Japan Society of Applied Physics