Interface Design Beyond Epitaxy

The study of thin films, their interfaces and thin film heterostructures has been a cornerstone of experimental research at reduced dimensions. Advancements in epitaxial techniques have enabled the engineering of atomically precise and well-defined interfaces. However, the parameter space of interfaces enabled by epitaxy is determined by the lattice symmetry of the substrate and the plane on which epitaxy takes place. This for such interfaces is taken as a given. I will take this opportunity to focus on recent developments in oxide growth enabling the separation of the grown thin films from the growth substrate, resulting in freestanding oxide membranes. These membranes have allowed for unprecedented access to avenues in oxides, with novel symmetry disallowed interfaces, which go beyond the epitaxially possible atomically sharp interfaces . I will show striking phenomena we have observed with an exemplary SrTiO₃ (001) on a sapphire (0001) interface, through which I hope to convey how these developments in oxides promise a fertile ground for remarkable discoveries in material science and physics.