Nanoscale studies of domain wall motion in epitaxial ferroelectric thin films

TL;DR

This study uses atomic force microscopy to explore nanoscale domain wall motion in epitaxial ferroelectric thin films, revealing a creep process influenced by disorder and defects, with implications for understanding ferroelectric switching dynamics.

Contribution

It provides new insights into the nanoscale domain wall dynamics and the effects of different types of defects on creep behavior in epitaxial ferroelectric films.

Findings

Domain wall velocity follows a creep law with electric field dependence.

Defects significantly reduce the creep exponent mu.

Disorder from defects influences domain wall motion in the films.

Abstract

Atomic force microscopy was used to investigate ferroelectric switching and nanoscale domain dynamics in epitaxial PbZr0.2Ti0.8O3 thin films. Measurements of the writing time dependence of domain size reveal a two-step process in which nucleation is followed by radial domain growth. During this growth, the domain wall velocity exhibits a v ~ exp[-(1/E)^mu] dependence on the electric field, characteristic of a creep process. The domain wall motion was analyzed both in the context of stochastic nucleation in a periodic potential as well as the canonical creep motion of an elastic manifold in a disorder potential. The dimensionality of the films suggests that disorder is at the origin of the observed domain wall creep. To investigate the effects of changing the disorder in the films, defects were introduced during crystal growth (a-axis inclusions) or by heavy ion irradiation, producing films with planar and columnar defects, respectively. The presence of these defects was found to significantly decrease the creep exponent mu, from 0.62 - 0.69 to 0.38 - 0.5 in the irradiated films and 0.19 - 0.31 in the films containing a-axis inclusions.