Pseudosymmetric Epitaxy for Scalable Growth of Uniform Two-Dimensional Ferroelectric α-In2Se3 Monolayer

The 2D ferroelectric semiconductor α-In2Se3 offers compelling opportunities for next-generation ultrathin electronics, but the controllable growth of a monolayer with large-scale uniformity and single phase has proven challenging. Here, we demonstrate the pseudosymmetry epitaxial growth of a uniform centimeter-scale α-In2Se3 monolayer by leveraging a fluorophlogopite mica (F-mica) substrate with its pseudohexagonal surface atom configuration, in a confined space chemical vapor deposition setup. Transmission electron microscopy and in-plane XRD reveal the pseudohexagonal symmetry of an F-mica surface and establish the in-plane epitaxial relation of (100) α-In2Se3∥(010) F-mica with a 4 × 4 α-In2Se3 unit cell matching the 3×3 F-mica surface. Second-harmonic generation and piezoresponse force microscopy confirm the homogeneity and polarization of the films. A ferroelectric semiconductor junction array based on the α-In2Se3 films exhibits consistent and reliable multipattern memorization and an enhanced On/Off ratio over 105. Our strategies offer critical insights into pseudosymmetric epitaxy of 2D materials and pave the way for advanced ultrathin ferroelectric memory technologies.