Braiding Lateral Morphotropic Grain Boundaries in Homogenetic Oxides

Interfaces formed by correlated oxides offer a critical avenue for discovering emergent phenomena and quantum states. However, the fabrication of oxide interfaces with variable crystallographic orientations and strain states integrated along a film plane is extremely challenging by conventional layer-by-layer stacking or self-assembling. Here, the creation of morphotropic grain boundaries (GBs) in laterally interconnected cobaltite homostructures is reported. Single-crystalline substrates and suspended ultrathin freestanding membranes provide independent templates for coherent epitaxy and constraint on the growth orientation, resulting in seamless and atomically sharp GBs. Electronic states and magnetic behavior in hybrid structures are laterally modulated and isolated by GBs, enabling artificially engineered functionalities in the planar matrix. This work offers a simple and scalable method for fabricating unprecedented innovative interfaces through controlled synthesis routes as well as providing a platform for exploring potential applications in neuromorphics, solid-state batteries, and catalysis.