Three-fold domain-wall topologies in BiFeO₃/DyScO₃(110) heterostructure

This study explores the synthesis of hetero-structured bismuth ferrite (BiFeO₃) nano-islands on a (110)-oriented orthorhombic dysprosium scandate (DyScO₃) substrate, with emphasis on the effects of pulsed laser energy density on morphological evolution and domain configurations. Structural characterization indicates that films deposited at a high laser energy density of 1.65 J/cm² form a maze-like morphology. In contrast, reducing the laser energy to 1.20 J/cm² induce the formation of highly dense and nano-sized discrete nano-islands. This morphological transition is attributed to the reduced kinetic energy of ablated particles and diminished adatom mobility at lower laser energies, which suppress surface diffusion and promote a shift from two-dimensional layer-by-layer growth to a three-dimensional island growth mode. Piezoresponse force microscopy reveals that film with maze-like morphology exhibits domain configurations with 71° and 109° domain walls, forming three-fold vortex and antivortex junctions. Meanwhile, three-dimensional nano-islands display multiple polar variants, resulting in three-fold vortex and antivortex configurations accompanied with 71°, 109°, and 180° domain walls. This study provides a new way to achieve a desired morphological and polar configurations in epitaxial heterostructure with a small lattice mismatch.