Boundary conditions control of topological polar nanodomains in epitaxial BiFeO3 (110) multilayered films.

Topological structures in ferroelectric materials play a crucial role in the potential applications of high-density memories and are currently the subject of intensive interest. Interfaces with local symmetry breaking have garnered wide attention in designing the topological domains in ferroelectric films by regulating the different boundary conditions. Here, we present multiple topological polar nanodomains near the heterointerfaces in the trilayered systems of BiFeO3/GdScO3/BiFeO3 grown on [110]-oriented TbScO3 substrates. The formation and stabilization of these topological polar states depend on the electrical and mechanical boundary conditions of the BiFeO3 layers. Aberration-corrected transmission electron microscopy observation reveals that the topological polar nanodomains, including nano-scale vortices and flux-closures at the termination of 109° domain walls and the semi-vortices at the end of 180° domain walls, are stabilized in the BiFeO3 layers confined by two orthorhombic structures. Furthermore, the formation of flux-closures near the BiFeO3/GdScO3 interface is influenced by the domain structures in the adjacent BiFeO3 layers, which is preferred by the 180° domain patterns rather than the 109° domain patterns. This work provides further understanding into the influences of boundary conditions on topological polar configurations and would offer guidance for designing novel topological states that enable the development of high-density memory devices. [ABSTRACT FROM AUTHOR]