Anisotropic Ferroelectric Switching Dynamics in Layered Bi₂WO₆.

Abstract

Layered perovskite oxides have emerged as a promising class of ferroelectric materials, yet their layered structure and nontrivial switching mechanisms require deeper investigation. Here, epitaxial Aurivillius-phase Bi₂WO₆ thin films are shown to exhibit crystallographic tilts likely originating from planar defects formed at step edges due to significant out-of-plane lattice mismatch. Such structural distortions impact polarization switching behavior, progressively suppressing switching response as the electric field rotates from parallel to perpendicular to the step edges, suggesting that the planar defects affect the domain nucleation and growth processes. Stroboscopic piezoresponse force microscopy reveals that domains nucleate and propagate preferentially along step edges under electric fields parallel to the step edges, while isotropic nucleation governs switching under fields perpendicular to the step edges, indicating defect-guided domain switching. Furthermore, domain-wall pinning at planar defects stabilizes multiple partially switched domains, allowing stable multilevel polarization switching with low cycle-to-cycle variation and long retention.