Ab initio calculations of doping mechanisms in SrTiO3

摘要

A density functional plane-wave pseudopotential method is used to study the formation energy of a number of acceptor- and donor-type defects in SrTiO3 as a function of oxidizing atmosphere and doping levels in the bulk crystal. Of the three donor defects (V-O, Nb-Ti and Al-Sr) and two acceptor defects (Na-Sr and Al-Ti) considered in this study, Nb-Ti and Na-Sr impurities are predicted to have the largest effect on electrical conductivity. The Al impurity is amphoteric and Al-Ti and Al-Sr can compensate one another. However, the relative abundance of Al-Ti and Al-Sr is found to depend on the oxidizing conditions. In a highly oxidizing environment Al-Ti is preferred, resulting in p-type material. Therefore, the Al self-compensation mechanism is predicted to be less effective in conditions where the oxygen partial pressure is high.