Ultrathin films of ferroelectric solid solutions under residual depolarizing field

TL;DR

This study uses first-principles methods to explore how residual depolarizing fields influence the phases and polarization patterns of ultrathin ferroelectric films, revealing diverse structural states depending on boundary conditions.

Contribution

It introduces a first-principles-derived approach to analyze the impact of depolarizing fields on ferroelectric thin films under various mechanical constraints.

Findings

Identification of multiple ferroelectric phases influenced by depolarizing fields

Discovery of complex polarization patterns including laminar nanodomains

Demonstration of the interplay between strain and surface charge screening

Abstract

A first-principles-derived approach is developed to study the effects of uncompensated depolarizing electric fields on the properties of Pb(Zr,Ti)O$_3$ ultrathin films for different mechanical boundary conditions. A rich variety of ferroelectric phases and polarization patterns is found, depending on the interplay between strain and amount of screening of surface charges. Examples include triclinic phases, monoclinic states with in-plane and/or out-of-plane components of the polarization, homogeneous and inhomogeneous tetragonal states, as well as, peculiar laminar nanodomains.