Effect of surface ionic screening on polarization reversal scenario in ferroelectric thin films: crossover from ferroionic to antiferroionic states

TL;DR

This study explores how surface ionic screening influences polarization reversal and phase states in ferroelectric thin films, revealing transitions from ferroionic to antiferroionic states through combined numerical and analytical modeling.

Contribution

It introduces a comprehensive analysis of surface ion formation energy effects on ferroelectric states, combining 3D finite element modeling with analytical Landau-Ginzburg theory.

Findings

Identified phase boundaries between ferroionic, antiferroionic, and non-ferroelectric states.

Mapped the influence of surface ion energy, film thickness, voltage, and temperature on polarization states.

Established correspondence between 3D numerical simulations and 1D analytical models.

Abstract

Nonlinear electrostatic interaction between the surface ions of electrochemical nature and ferroelectric dipoles gives rise to the coupled ferroionic states in nanoscale ferroelectrics. Here, we investigated the role of the surface ions formation energy value on the polarization states and polarization reversal mechanisms, domain structure and corresponding phase diagrams of ferroelectric thin films. Using 3D finite elements modeling we analyze the distribution and hysteresis loops of ferroelectric polarization and ionic charge, and dynamics of the domain states. These calculations performed over large parameter space delineate the regions of single- and poly- domain ferroelectric, ferroionic, antiferroionic and non-ferroelectric states as a function of surface ions formation energy, film thickness, applied voltage and temperature. We further map the analytical theory for 1D system onto effective Landau-Ginzburg free energy and establish the correspondence between the 3D numerical and 1D analytical results. This approach allows performing the overview of the phase diagrams of ferroionic systems and exploring the specific of switching and domain evolution phenomena.