Relaxation of transport properties in electron doped SrTiO3

We electron-dope single crystal samples of SrTiO_3 by exposing them to Ar^+ irradiation and observe carrier mobility similar in its magnitude and temperature dependence to the carrier mobility in other electron-doped SrTiO3 systems. We find that some transport properties are time-dependent. In particular, the sheet resistance increases with time at a temperature-dependent rate, suggesting an activation barrier on the order of 1 eV. We attribute the relaxation effects to diffusion of oxygen vacancies - a process with energy barrier similar to the observed activation energy.