Strain engineering of epitaxial oxide heterostructures beyond substrate limitations

TL;DR

This paper introduces a method to achieve continuous, large epitaxial strain in oxide heterostructures beyond substrate limitations by inserting an interface layer, enabling phase transitions and stabilization of new phases in BiFeO3.

Contribution

It demonstrates a novel approach for strain engineering in oxide heterostructures using interface layers to surpass substrate constraints and induce new phases.

Findings

Achieved continuous phase transition in BiFeO3 from tension to compression.

Created a metastable super-tetragonal phase and morphotropic phase boundaries.

Extended strain engineering capabilities beyond traditional substrate limitations.

Abstract

The limitation of commercially available single-crystal substrates and the lack of continuous strain tunability preclude the ability to take full advantage of strain engineering for further exploring novel properties and exhaustively studying fundamental physics in complex oxides. Here we report an approach for imposing continuously tunable, large epitaxial strain in oxide heterostructures beyond substrate limitations by inserting an interface layer through tailoring its gradual strain relaxation. Taking BiFeO3 as a model system, we demonstrate that the introduction of an ultrathin interface layer allows the creation of a desired strain that can induce phase transition and stabilize a new metastable super-tetragonal phase as well as morphotropic phase boundaries overcoming substrate limitations. Furthermore, continuously tunable strain from tension to compression can be generated by precisely adjusting the thickness of the interface layer, leading to the first achievement of continuous O-R-T phase transition in BiFeO3 on a single substrate. This proposed route could be extended to other oxide heterostructures, providing a platform for creating exotic phases and emergent phenomena.