Strong tunability of epitaxial relationship and reconstruction at improper ferroelectric interface

TL;DR

This study demonstrates the ability to controllably switch between different atomic interface structures in improper ferroelectric thin films, affecting their ferroelectric properties and potentially solving critical thickness limitations.

Contribution

It reveals how growth conditions and substrate composition can precisely tune the epitaxial interface structure in improper ferroelectric films, a novel control mechanism.

Findings

Disordered interface suppresses primary ferroelectric distortion.

Hybridized interface maintains ferroelectric distortion with minimal suppression.

Interface tunability impacts ferroelectric film properties and critical thickness.

Abstract

The atomic structures at epitaxial film-substrate interfaces determine scalability of thin films and can result in new phenomena. However, it is challenging to control the interfacial structures since they are decided by the most stable atomic bonding. In this work, we report strong tunability of the epitaxial interface of improper ferroelectric hexagonal ferrites deposited on spinel ferrites. The selection of two interface types, related by a 90 deg rotation of in-plane epitaxial relations and featured by disordered and hybridized reconstructions respectively, can be achieved by growth conditions, stacking sequences, and spinel compositions. While the disordered type suppresses the primary K3 structure distortion and ferroelectricity in hexagonal ferrites, the hybridized type is more coherent with the distortion with minimal suppression. This tunable interfacial structure provides critical insight on controlling interfacial clamping and may offer a solution for the long-standing problem of practical critical thickness in improper ferroelectrics.