Control of ferroelectric domain wall dynamics by point defects: Insights from ab initio based simulations

TL;DR

This paper investigates how point defects, especially defect dipoles, influence ferroelectric domain wall dynamics in BaTiO3 using ab initio-based molecular dynamics simulations, revealing defect interactions and mechanisms of wall pinning and motion.

Contribution

It provides new insights into the role of defect dipoles in ferroelectric domain wall behavior, an area previously underexplored in theoretical studies.

Findings

Defects act as local pinning centers and influence wall motion.

Walls can bypass sparse defects via dipole cluster nucleation.

Interaction between acceptor dopants and walls is short-ranged.

Abstract

The control of ferroelectric domain walls and their dynamics on the nanoscale becomes increasingly important for advanced nanoelectronics and novel computing schemes. One common approach to tackle this challenge is the pinning of walls by point defects. The fundamental understanding on how different defects influence the wall dynamics is, however, incomplete. In particular, the important class of defect dipoles in acceptor-doped ferroelectrics is currently underrepresented in theoretical work. In this study, we combine molecular dynamics simulations based on an \textit{ab\ initio}-derived effective Hamiltonian and methods from materials informatics, and analyze the impact of these defects on the motion of 180$^{\circ}$ domain walls in tetragonal BaTiO$_3$. We show how these defects can act as local pinning centers and restoring forces on the domain structure. Furthermore, we reveal how walls can flow around sparse defects by nucleation and growth of dipole clusters, and how pinning, roughening and bending of walls depend on the defect distribution. Surprisingly, the interaction between acceptor dopants and walls is short-ranged. We show that the limiting factor for the nucleation processes underlying wall motion is the defect-free area in front of the wall.