Abstract: Ferroelectric topological domain structures exhibit rich physical properties and demonstrate a wide range of application potential for next-generation nanoelectronic devices. The fundamental issue for the applications of topological devices lies in the precise design and control of ferroelectric topological domain states. In this work, we investigated the growth condition effects on center-type quadrant topological doman configurations in BiFeO₃ nanoislands formed through bending-induced bulges, which were generated by underlying electrode SrRuO₃ nanoislands. The experimental results indicate that the formation of central-type topological domains is closely related to the growing conductions of SrRuO₃electrode nano-islands, nano-islands dimensions, the temperature of BiFeO₃epitaxial growth, and the deposition thickness. When the lateral size of the electrode nano-islands ranges from 300 nm to 400 nm, the subsequently grown BiFeO₃thin film can be induced by the underlying electrode protrusions to develop nano-islands, and central-type four-quadrant topological domains. As the height of the electrode nano-islands gradually increases, the domain structure of the ferroelectric nano-islands changes from the stripe domains of the thin film to the central-type topological domains. However, at the diameter of electrode nano-island exceeding 500 nm, the central domain transforms into a zigzag domain-wall configuration, demonstrating the important role of flexoelectric effects induced by the morphological protrusions in the formation of topological domains. Within a certain growth parameters ( growth temperature: 690-730 °C; BiFeO₃ thickness: 30-60 nm), increasing the growth temperature facilitate the formation of complete four-quadrant central-type topological domains, highlighting synergistic interactions among defects, domain wall energy, and fexoelectric effects on the formation central domain states. This central-type topological domain can also be switched by external field, and simultaneously induce switching between high/low conductive states, laying a foundation for the further construction of polarization topological electronic devices.

Key words: BiFeO₃, self-assembly, nanoisland arrays, quad-domain textures, flexoelectric effect