Phase-field modeling of chemical control of polarization stability and switching dynamics in ferroelectric thin film

TL;DR

This paper introduces a self-consistent phase-field model incorporating electrochemical boundary conditions to study how surface chemistry influences polarization stability and switching in ferroelectric thin films, revealing size effects and emergent phenomena.

Contribution

The authors developed a novel phase-field model with electrochemical boundary conditions, enabling the study of surface chemical effects on ferroelectric polarization and switching dynamics.

Findings

Surface chemical environment significantly affects ferroelectric polarization.

Size effects are pronounced under chemical screening conditions.

Oxygen partial pressure influences polarization switching behavior.

Abstract

Phase-field simulation (PFS) have revolutionized the understanding of domain structure and switching behavior in ferroelectric thin films and ceramics. Generally, PFS is based on solution of a (set) of Ginzburg-Landau equations for a defined order parameter field(s) under physical boundary conditions (BCs) of fixed potential or charge. While well-matched to the interfaces in bulk materials and devices, these BCs are generally not applicable to free ferroelectric surfaces. Here, we developed a self-consistent phase-field model with boundary conditions based on electrochemical equilibria. We chose Pb(Zr0.2Ti0.8)O3 ultrathin film consisting of (001) oriented single tetragonal domain (Pz) as a model system, and systematically studied the effects of oxygen partial pressure, temperature and surface ion on the ferroelectric state, and compared it with the case of complete screening. We have further explored the polarization switching induced by the oxygen partial pressure and observed pronounced size effect induced by chemical screening. Our work thus helps to understand the emergent phenomena in ferroelectric thin films brought about by the electrochemical ionic surface compensations.