Shear effects in lateral piezoresponse force microscopy at 180$^\circ$ ferroelectric domain walls

TL;DR

This paper investigates shear strain effects causing lateral piezoresponse at 180° ferroelectric domain walls in specific thin films, highlighting the importance of considering these effects for accurate domain imaging.

Contribution

It demonstrates the shear strain origin of lateral piezoresponse at 180° domain walls and clarifies its impact on interpreting ferroelectric domain structures.

Findings

Shear strain causes non-zero lateral piezoresponse at 180° domain walls.

The effect aligns with theoretical predictions based on piezoelectric coefficient sign change.

In BiFeO₃ films, shear effects overlay true in-plane polarization signals.

Abstract

In studies using piezoresponse force microscopy, we observe a non-zero lateral piezoresponse at 180$^\circ$ domain walls in out-of-plane polarized, c-axis-oriented tetragonal ferroelectric Pb(Zr$_{0.2}$Ti$_{0.8}$)O$_3$ epitaxial thin films. We attribute these observations to a shear strain effect linked to the sign change of the $d_{33}$ piezoelectric coefficient through the domain wall, in agreement with theoretical predictions. We show that in monoclinically distorted tetragonal BiFeO$_3$ films, this effect is superimposed on the lateral piezoresponse due to actual in-plane polarization, and has to be taken into account in order to correctly interpret the ferroelectric domain configuration.