Metal–insulator transition in oxygen deficient Ti based oxide films

We have studied the effects of oxygen deficiency on the physical properties of Ti based oxide films (La2/3TiO3−δ, SrTiO3−δ, Ba0.2Sr0.8TiO3−δ). These films were obtained by pulsed-laser deposition and a noticeable oxygen deficiency, i.e. about 15% of oxygen missing, leads to very specific transport properties. Metallic or semiconductor behaviors are evidenced in the resistivity measurements as a function of temperature: a metal–insulator transition (MIT) is observed at low temperatures. Two different approaches have been used to interpret that MIT. For La2/3TiOx, the MIT can be described in the frame of the quantum corrections to conductivity (QCC) in disordered oxides. On the contrary, for Ba0.2Sr0.8TiOx or SrTiOx the MIT cannot be correctly fitted by the QCC model, and the resistivity curve with temperature is better described in the frame of the electron localization which can be classically modeled by the variable range hopping model.