Electronic structure of oxygen vacancies in SrTiO3 and LaAlO3

The electronic structure of oxygen vacancies in bulk perovskite oxides SrTiO3 and LaAlO3 is studied using the Heyd, Scuseria, Ernzerhof (HSE) hybrid density functional. In SrTiO3 the oxygen vacancy defect introduces a localized state comprised of 3d(z)2 and 4p(z) orbitals of the adjacent Ti atoms. This results in a bound state 0.7 eV below the conduction band edge. For LaAlO3, the oxygen vacancy creates a deep state 2.19 eV below the conduction band edge. The defect state is a hybrid of the adjacent La 5d and the Al 3p states. We compute the formation energies of the neutral oxygen vacancy defect V-0 in bulk SrTiO3 and LaAlO3 to be 6.0 and 8.3 eV, respectively.