Energy levels of point defects in SrTiO3 and related oxides

The energy levels of defects in SrTiO3, PbTiO3 and PbZrO3 have been calculated by the tight-binding Greens function method and compared to experiment. This method is very useful for displaying the chemical trends in defect energy levels. The Ti and O vacancies are found to be shallow. Transition metal impurities at the octahedral ion site are found to give rise to numerous charge states because of the large intra-atomic electron repulsion. The levels are generally in the high spin configuration, except for the high valence transition metals. The levels of Cr4+, Fe4+, and Co4+ lie near midgap. The Ti3+ trapped electron centers become deep at higher Zr contents in Pb(Zr,Ti)O-3. (C) 2003 American Institute of Physics.