Epitaxial Growth of Ferroelectric BaTiO₃ on a Compliant Substrate

The concept of compliant substrates, which distribute misfit strain energy between the film and substrate, has been widely explored in the growth of Ⅲ-Ⅴ semiconductors but remains largely unexplored in oxide heteroepitaxy. In this work, we demonstrate the epitaxial growth of single-crystalline BaTiO₃ films on ultrathin CaSnO₃ nanomembranes, both synthesized via hybrid molecular beam epitaxy (MBE). Structural and morphological characterization using reflection high-energy electron diffraction, scanning electron microscopy, atomic force microscopy, mechanical testing, and optical microscopy reveals how substrate compliance influences strain relaxation and surface morphology in BaTiO₃ films. We will discuss the design criteria for selecting compliant oxide substrates and highlight the emergence of unique surface textures in BaTiO₃/CaSnO₃ heterostructures, illustrating a new pathway for strain engineering in epitaxial oxides.