Barium titanate（BaTiO3）has been an important material in the manufacture of electronic components for many years due to its unique properties of high dielectric constant,high ferroelectricity and piezoelectricity.They are mainly used as superconductors,ferromagnets,pyroelectric detectors and high capacitance capacitors.The functional properties of ferroelectric thin films for various purposes are determined by domains and domain walls.Understanding the development and topologies of domains and domain walls is critical for modifying and exploring their dynamics.Super-domains and super-domain walls occur when domains aggregate into hierarchical structures,exhibiting unit shape and potentially leading to distinct behaviour.Using the Ba Ti O3 thin films as a model system,we create the misfit strain-misfit strain phase diagram at various temperatures and use phase-field simulations to investigate the formation condition,morphological features,and polarization configurations of two types of super-domain structures.We illustrate how super-domain structures can be thought of as a superposition of two sets of poly-twin structures in well-defined planes.In the same way that ordinary domain walls have different energies and finite thicknesses,super-domain walls have variable energies and finite thicknesses.We also show that some super-domain walls can be unusually wide and carry electricity.This discovery may pique people’s curiosity in learning more about the structures and functions of super-domains and super-domain walls in ferroelectric thin films,which could be used in next-generation electronic devices.