Giant Flexoelectric Effect in Ferroelectric Epitaxial Thin Films

TL;DR

This paper demonstrates a giant flexoelectric effect in ferroelectric epitaxial thin films caused by nanoscale strain gradients, enabling new ways to tune their physical properties.

Contribution

It reports the discovery of extremely large strain gradients in ferroelectric thin films and shows how flexoelectricity can be used to control their properties.

Findings

Strain gradients are 6-7 orders of magnitude larger than in bulk oxides.

Flexoelectricity influences domain configurations and hysteresis.

Nanoscale strain gradients can be precisely measured using X-ray diffraction.

Abstract

We report on nanoscale strain gradients in ferroelectric HoMnO3 epitaxial thin films, resulting in a giant flexoelectric effect. Using grazing-incidence in-plane X-ray diffraction, we measured strain gradients in the films, which were 6 or 7 orders of magnitude larger than typical values reported for bulk oxides. The combination of transmission electron microscopy, electrical measurements, and electrostatic calculations showed that flexoelectricity provides a means of tuning the physical properties of ferroelectric epitaxial thin films, such as domain configurations and hysteresis curves.