In Situ Observation of Domain Wall Lateral Creeping in a Ferroelectric Capacitor

Abstract

As a promising candidate for next‐generation nonvolatile memory devices, ferroelectric oxide films exhibit many emergent phenomena with functional applications, making understanding polarization switching and domain evolution behaviors of fundamental importance. However, tracking domain wall motion in ferroelectric oxide films with high spatial resolution remains challenging. Here, an in situ biasing approach for direct atomic‐scale observations of domain nucleation and sideways motion is presented. By accurately controlling the applied electric field, the lateral translational speed of the domain wall can decrease to less than 2.2 Å s−1, which is observable with atomic resolution STEM imaging. In situ observations on a capacitor structured PbZr0.1Ti0.9O3/La0.7Sr0.3MnO3 heterojunction demonstrate the unique creeping behavior of a domain wall under a critical electric field, with the atomic structure of the creeping domain wall revealed. Moreover, the evolution of the metastable domain wall forms an elongated morphology, which contains a large proportion of charged segments. Phase‐field simulations unveil the competition between gradient, elastic, and electrostatic energies that decide this unique domain wall creeping and morphology variation. This work paves the way toward a complete fundamental understanding of domain wall physics and potential modulations of domain wall properties in real devices.

Reduced dimensional ferroelectric domains and their characterization techniques

“…Ferroelectric thin film samples are usually prepared by creating a lamella using FIB and then transferring the sample [181,183] . Through the design of the sample's electrode, the electrical path can be constructed as desired, either in-plane or out-of-plane [182,184,185] . In PMN-PT single crystal, electrical biasing experiments were conducted using a MEMS chip.…”

“…During the 280 electrical cycles, c-domain formation was observed, and charge accumulation was also monitored using TEM. The accumulation of charge led to the formation of frozen domains and shed light on ferroelectric degradation [185] . As another example, in situ electrical biasing experiments were conducted on an (La,Sr)MnO 3 /Hf 0.5 Zr 0.5 O 2 /(La,Sr)MnO 3 capacitor at the atomic scale.…”