Evolution of the band alignment at polar oxide interfaces

TL;DR

This study uses first-principles calculations to analyze how the band alignment at polar oxide interfaces evolves with interfacial composition, revealing a linear relationship influenced by electrostatic screening effects.

Contribution

It provides a detailed first-principles analysis of how interfacial A-site composition affects band alignment and Schottky barrier height at oxide heterointerfaces, highlighting electrostatic screening mechanisms.

Findings

Linear change in SrTiO3 valence band offset with A-site composition

Electrostatic screening influences interfacial dipole and potential step

Results agree with recent experimental data

Abstract

First-principles calculations demonstrate the evolution of the band alignment at La0.7A0.3MnO3|La1-xAx|TiO2|SrTiO3(001) heterointerfaces, where A = Ca, Sr, or Ba, as the interfacial A-site composition, La1-Ax, is varied from x = 0.5 to x = 1.0. This variation leads to a linear change of the SrTiO3 valence band offset with respect to the Fermi level of the La0.7A0.3MnO3 metal electrode and hence to a linear change of the Schottky barrier height at this interface. The effect arises due to electrostatic screening of the polar interface which alters the interfacial dipole and hence the electrostatic potential step at this interface. We find that both the La0.7A0.3MnO3 and SrTiO3 layers contribute to screening with both electronic and ionic screening being important for the change in the interface dipole. The results are in agreement with the recent experimental data.