Thermal stability of nano-scale ferroelectric domains by molecular dynamics modeling

TL;DR

This study uses molecular dynamics to investigate how thermal fluctuations affect the stability and dynamics of nano-scale ferroelectric domain walls in BaTiO3, revealing limits on domain density in devices.

Contribution

It introduces a combined molecular dynamics approach to analyze thermally induced modifications of ferroelectric domain walls, highlighting the role of microscopic fluctuations.

Findings

Thermal fluctuations can induce domain wall motion and stability changes.

Small domains are unstable and can be annihilated by thermal fluctuations.

Domain wall density is limited by thermal stability, even below Curie temperature.

Abstract

Ultra-dense domain walls are increasingly important for many devices but their microscopic properties are so far not fully understood. Here we use molecular dynamic simulations to study the domain wall stability in the prototypical ferroelectric BaTiO3 combining core-shell pair potentials and a coarse-grained effective Hamiltonian. We transfer the discussion of the field-driven nucleation and motion of domain walls to thermally induced modifications of the wall without an external driving force. Our simulations show that domain wall dynamics and stability depend crucially on microscopic thermal fluctuations. Enhanced fluctuations at domain walls may result in the formation of critical nuclei for the permanent shift of the domain wall. If two domain walls are close - put in other words, when domains are small - thermal fluctuations can be sufficient to bring domain walls into contact and lead to the annihilation of small domains. This is even true well below the Curie temperature and when domain walls are initially as far apart as 6 unit cells. Such small domains are, thus, not stable and limit the maximum achievable domain wall density in nanoelectronic devices.