Electronic charge redistribution in LaAlO$_3$(001) thin films deposited at SrTiO$_3$(001) substrate: First principles analysis and the role of stoichiometry

TL;DR

This study uses first-principles calculations to analyze how charge redistribution and stoichiometry affect the electronic properties of LaAlO$_3$/SrTiO$_3$(001) heterointerfaces, revealing that non-stoichiometric films can exhibit conductivity regardless of film thickness.

Contribution

It demonstrates that the electronic properties of LaAlO$_3$/SrTiO$_3$ heterointerfaces depend on surface termination and stoichiometry, providing insights into the mechanisms behind interface conductivity.

Findings

Non-stoichiometric films can be conductive regardless of thickness.

Surface termination influences the heterointerface's conducting properties.

Both polar catastrophe and polar distortion scenarios are possible depending on stoichiometry.

Abstract

We present a comprehensive first-principles study of the electronic charge redistribution in atomically sharp LaAlO$_3$/SrTiO$_3$(001) heterointerfaces of both n- and p-types allowing for non-stoichiometric composition. Using two different computational methods within the framework of the density functional theory (linear combination of atomic orbitals and plane waves) we demonstrate that conducting properties of LaAlO$_3$/SrTiO$_3$(001) heterointerfaces strongly depend on termination of LaAlO$_3$ (001) surface. We argue that both the polar "catastrophe" and the polar distortion scenarios may be realized depending on the interface stoichiometry. Our calculations predict that heterointerfaces with a non-stoichiometrc film---either LaO-terminated n-type or AlO$_2$-terminated p-type---may exhibit the conductivity of n- or p-type, respectively, independently of LaAlO$_3$(001) film thickness.