Interface Design Beyond Epitaxy: Oxide Heterostructures Comprising Symmetry-forbidden Interfaces

TL;DR

This paper introduces a new membrane-based method for creating oxide heterostructures with symmetry-forbidden interfaces, surpassing epitaxial growth limitations and enabling atomically clean, well-defined interfaces with novel reconstructions.

Contribution

It presents a novel fabrication approach for oxide heterostructures that does not rely on epitaxy, allowing interfaces between mismatched symmetries and lattice constants.

Findings

Successfully fabricated symmetry-forbidden interfaces between sapphire and SrTiO3

Achieved atomically clean interfaces with moiré-type reconstruction

Demonstrated structural integrity and novel interface properties

Abstract

Epitaxial growth of thin-film heterostructures is generally considered the most successful procedure to obtain interfaces of excellent structural and electronic quality between three-dimensional materials. However, these interfaces can only join material systems with crystal lattices of matching symmetries and lattice constants. We present a novel category of interfaces, the fabrication of which is membrane-based and does not require epitaxial growth. These interfaces therefore overcome limitations imposed by epitaxy. Leveraging the additional degrees of freedom gained, we demonstrate atomically clean interfaces between three-fold symmetric sapphire and four-fold symmetric SrTiO3. Atomic-resolution imaging reveals structurally well-defined interfaces with a novel moir\'e-type reconstruction.