Local hard and soft pinning of 180$^\circ$ domain walls in BaTiO$_3$ probed by in situ transmission electron microscopy

TL;DR

This study investigates the behavior of 180-degree domain walls in BaTiO₃ under electric fields using in situ TEM, revealing distinct hard and soft pinning effects with local, direct measurements.

Contribution

It provides the first direct in situ TEM evidence of local hard and soft domain wall pinning in BaTiO₃, linking domain wall behavior to ferroelectric properties.

Findings

Hard domain walls exhibit asymmetrical hysteresis loops.

Soft domain walls follow Rayleigh-like behavior.

Pinning effects are measured locally and directly from domain images.

Abstract

We report on the electric field response of 180 degree nanodomain walls in BaTiO$_3$ using in situ electrical biasing in transmission electron microscopy (TEM). The sample is biased on a micro-device designed for reliable testing whose key attributes are confirmed by finite element calculations. The presence of weakly charged zig-zag domain walls at room temperature is attributed to the geometric confinement of the device. The motion of the domain walls under the applied electric field allows to extract local P-E loops where distinct domain wall pinning in deep and random energy potential profiles, characteristic for hard and soft ferroelectrics, respectively, are observed. Hard domain wall pinning results in asymmetrical loops typical for "hard" ferroelectrics while the soft domain wall pinning follows Rayleigh-like behaviour. All effects are measured locally and directly from the imaged domain structure.