Thermal quench effects on ferroelectric domain walls

TL;DR

This study investigates how heat-quench cycles affect ferroelectric domain wall roughening, revealing a transition in roughness behavior and emphasizing the role of defect configurations and oxygen vacancies in domain stability.

Contribution

It provides new insights into the mechanisms behind domain wall roughening after thermal quench, favoring a model involving metastable states and defect interactions over simple thermal configurations.

Findings

Roughness exponent .25 to 0.5 increase after quench

Metastable state structures suggest a growing dynamical length scale

Oxygen vacancies stabilize ferroelectric domain structures

Abstract

Using piezoresponse force microscopy on epitaxial ferroelectric thin films, we have measured the evolution of domain wall roughening as a result of heat-quench cycles up to 735C, with the effective roughness exponent \zeta\ changing from 0.25 to 0.5. We discuss two possible mechanisms for the observed \zeta\ increase: a quench from a thermal 1-dimensional configuration, and from a locally-equilibrated pinned configuration with a crossover from a 2- to 1-dimensional regime. We find that the post-quench spatial structure of the metastable states, qualitatively consistent with the existence of a growing dynamical length scale whose ultra slow evolution is primarily controlled by the defect configuration and heating process parameters, makes the second scenario more plausible. This interpretation suggests that pinning is relevant in a wide range of temperatures, and in particular, that purely thermal domain wall configurations might not be observable in this glassy system. We also demonstrate the crucial effects of oxygen vacancies in stabilizing domain structures.