Pseudo-Ferroelectric Domain-Wall in Perovskite Ferroelectric Thin Films

Perovskite ferroelectric thin films exhibit unique dielectric and piezoelectric properties owing to their internal polarized domains that accommodate the out-of-plane (ferroelectric) and in-plane (ferroelastic) polarization-induced electrostatic and elastic energy. These domains are generally treated as 2D defects with distinctive differences in domain morphology and domain-wall characteristics, although they are indeed 3D volumetric defects. Here, by using atomistic simulation and microscopy characterization, a "pseudo-ferroelectric domain" that has the morphology similar to a ferroelectric domain but holds the same defect character of ferroelastic domain-wall, i.e., semi-coherent (100)(matrix)||(100)(domain) interface is identified. Such pseudo-ferroelectric domain walls will play a critical role in the migration kinetics of ferroelastic domains and in the piezoelectric responses of ferroelectric thin films during cyclic mechanical/electrical loading. The study throws light on a novel aspect of domains, namely, the 3D configuration and mobility of domain walls, and their role in the overall domain engineering.