Effect of epitaxial strain on the spontaneous polarization of thin film ferroelectrics

TL;DR

This study uses first principles calculations to analyze how epitaxial strain affects the spontaneous polarization in various ferroelectric thin films, revealing different strain sensitivities among materials.

Contribution

It demonstrates that the strain dependence of polarization varies significantly among ferroelectric materials and links this behavior to their piezoelectric and elastic properties.

Findings

Strong strain dependence in BaTiO₃ and PbTiO₃

Weak strain dependence in LiNbO₃ and BiFeO₃

Behavior explained by piezoelectric and elastic constants

Abstract

We investigate the variation of the spontaneous ferroelectric polarization with epitaxial strain for BaTiO$_3$, PbTiO$_3$, LiNbO$_3$, and BiFeO$_3$ using first principles calculations. We find that while the strain dependence of the polarization is very strong in the simple perovskite systems BaTiO$_3$ and PbTiO$_3$ it is only weak in LiNbO$_3$ and BiFeO$_3$. We show that this different behavior can be understood purely in terms of the piezoelectric and elastic constants of the unstrained bulk material, and we discuss several factors that determine the strain behavior of a certain material.