Interplay between strain and oxygen vacancies in lanthanum aluminate

TL;DR

This study uses density functional theory to analyze how epitaxial strain influences oxygen vacancy formation in lanthanum aluminate, finding minimal dependence within typical strain ranges, implying extrinsic factors affect vacancy concentrations.

Contribution

The paper provides the first detailed computational analysis of the relationship between strain and oxygen vacancies in LaAlO$_3$, showing negligible effects within accessible strain ranges.

Findings

Oxygen vacancy formation energy is largely unaffected by strain.

Experimental variations in vacancy concentrations likely stem from extrinsic factors.

Strain does not significantly alter defect formation in LaAlO$_3$.

Abstract

We evaluate the interplay between epitaxial strain and oxygen vacancy formation in the perovskite-structure oxide lanthanum aluminate, LaAlO$_3$. Using density functional theory within the GGA$+U$ approximation we calculate the dependence of the oxygen vacancy formation energy on the biaxial strain conditions. We find that the change in formation energy with strain is negligible over the range of strain values usually accessible through coherent epitaxial growth. Our findings suggest that experimental reports of different oxygen vacancy concentrations in strained films result from extrinsic factors, or from other impurities such as defect complexes.