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

Abstract

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 <math xmlns="http://www.w3.org/1998/Math/MathML"><mn>3</mn><mo>×</mo><msqrt><mn>3</mn></msqrt></math> 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.