Polar catastrophe at the MgO(100)/SnO2(110) interface

Abstract

First principles calculations, based on density functional theory, are used to investigate the structural and electronic properties of the epitaxial MgO(100)/SnO₂(110) interface of wide band gap insulators. Depending on the interface termination, nonmagnetic metallic and half-metallic interface states are observed. The formation of these states is explained by a polar catastrophe model for nonpolar–polar interfaces. Strong lattice distortions and buckling develop in SnO₂, which influence the interface properties as the charge discontinuity is partially screened. Already a single unit cell of SnO₂ is sufficient to drive the polar catastrophe scenario.