Electronic conductivity and structural distortion at the interface between insulators SrTiO3 and LaAlO3

TL;DR

This study investigates the atomic-scale structure and electronic properties of the SrTiO3/LaAlO3 interface, revealing structural distortions linked to charge transfer that contribute to its unexpected metallic behavior.

Contribution

The paper provides a detailed structural analysis of the SrTiO3/LaAlO3 interface using advanced microscopy, elucidating the microscopic mechanisms behind its conductivity.

Findings

Interface unit cells are elongated.

Structural distortion relates to electrostatic charge.

Charge transfer contributes to metallicity.

Abstract

When insulator LaAlO3 is grown by epitaxy onto a TiO2-terminated {100} surface of insulator SrTiO3, the resulting system has a metallic character. This phenomenon has been associated with an electrostatic frustration at the interface, as {100} surfaces of SrTiO3 are neutral while those of LaAlO3 are polar, but its microscopic mechanism is not quite understood. Here, we present a structural characterisation of this interface by aberration-corrected transmission electron microscopy. The unit cells at the interface appear elongated: we discuss this distortion in terms of electrostatic charge and extra carriers at the interface.