Evolution of the interfacial structure of LaAlO3 on SrTiO3

TL;DR

This study investigates how the atomic structure of LaAlO3 on SrTiO3 evolves with film thickness, revealing depolarizing buckling, intermixing, and implications for conductivity through experimental and theoretical analysis.

Contribution

It provides new insights into the atomic-scale structural evolution and interfacial phenomena of LaAlO3/SrTiO3 heterostructures using surface x-ray diffraction and density-functional theory.

Findings

Depolarizing buckling decreases with increasing film thickness.

Cationic intermixing extends about three monolayers into the interface.

Interfaces of films thinner than four monolayers may influence conductivity.

Abstract

The evolution of the atomic structure of LaAlO3 grown on SrTiO3 was investigated using surface x-ray diffraction in conjunction with model-independent, phase-retrieval algorithms between two and five monolayers film thickness. A depolarizing buckling is observed between cation and oxygen positions in response to the electric field of polar LaAlO3, which decreases with increasing film thickness. We explain this in terms of competition between elastic strain energy, electrostatic energy, and electronic reconstructions. The findings are qualitatively reproduced by density-functional theory calculations. Significant cationic intermixing across the interface extends approximately three monolayers for all film thicknesses. The interfaces of films thinner than four monolayers therefore extend to the surface, which might affect conductivity.