Polarity-induced oxygen vacancies at LaAlO3|SrTiO3 interfaces

TL;DR

This study uses first-principles calculations to analyze how oxygen vacancies form at LaAlO3|SrTiO3 interfaces, revealing their dependence on position and thickness, and explaining their impact on interface conductivity.

Contribution

It provides a detailed theoretical analysis of oxygen vacancy formation and its effects on interface properties, introducing an analytical capacitor model for interpretation.

Findings

Oxygen vacancies form preferentially at p-type interfaces.

Excess electrons from vacancies reduce their energy by migrating to n-type interfaces.

The asymmetric vacancy behavior influences the conducting nature of the interfaces.

Abstract

Using first-principles density functional theory calculations, we find a strong position and thickness dependence of the formation energy of oxygen vacancies in LaAlO3|SrTiO3 (LAO|STO) multilayers and interpret this with an analytical capacitor model. Oxygen vacancies are preferentially formed at p-type SrO|AlO2 rather than at n-type LaO|TiO2 interfaces; the excess electrons introduced by the oxygen vacancies reduce their energy by moving to the n-type interface. This asymmetric behavior makes an important contribution to the conducting (insulating) nature of n-type (p-type) interfaces while providing a natural explanation for the failure to detect evidence for the polar catastrophe in the form of core level shifts.