Effect of symmetry mismatch on the domain structure of rhombohedral BiFeO3 thin films

TL;DR

This study reveals that the monoclinic distortion of substrates, caused by oxygen octahedral rotation, influences domain variant selection in rhombohedral BiFeO3 thin films, beyond just lattice mismatch effects.

Contribution

It demonstrates that substrate symmetry mismatch, specifically monoclinic distortion, plays a key role in domain structure formation in BiFeO3 films, providing new insights into domain engineering.

Findings

Two domain variants on DyScO3 substrates

Four domain variants on buffered DyScO3 substrates

Substrate symmetry mismatch affects domain evolution

Abstract

Considerable work has focused on the use of epitaxial strain to engineer domain structures in ferroic materials. Here, we revisit the observed reduction of domain variants in rhombohedral BiFeO3 films on rare-earth scandate substrates. Prior work has attributed the reduction of domain variants to anisotropic in-plane strain, but our findings suggest that the monoclinic distortion of the substrate, resulting from oxygen octahedral rotation, is the driving force for variant selection. We study epitaxial BiFeO3 DyScO3 (110)o heterostructures with and without ultrathin, cubic SrTiO3 buffer layers as a means to isolate the effect of symmetry mismatch on the domain formation. Two variant stripe domains are observed in films grown directly on DyScO3, while four-variant domains are observed in films grown on SrTiO3 buffered DyScO3 when the buffer layer is >2 nm thick. This work provides insights into the role of the substrate beyond just lattice mismatch in manipulating and controlling domain structure evolution in materials.