Stacking-specific two-dimensional In2Se3 for ferroelectric homojunctions

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Abstract
Two-dimensional (2D) ferroelectric semiconductors offer unique opportunities for ultrathin non-volatile memory and neuromorphic devices, yet the role of stacking order in intrinsic ferroelectric systems remains largely unexplored. Here we report the stacking-controlled growth of large-area 2D β′- and α-In2Se3 with distinct 2H and 3R configurations through chemical vapour deposition by regulating selenium kinetics and strain relaxation. By combining atomic-resolution microscopy, non-linear optical characterization and first-principles calculations, we uncover a strong correlation between stacking order and ferroelectric behaviour: β′-In2Se3 undergoes an antiferroelectric-to-paraelectric transition when switching from 2H to 3R stacking, whereas in α-In2Se3, in-plane ferroelectric polarization vanishes during the 3R-to-2H transition. We further achieve the controlled synthesis of 2H/3R ferroelectric homojunctions and directly visualize polarization-dependent interfacial potential barriers using differential phase-contrast scanning transmission electron microscopy. The engineered homojunctions exhibit switchable band alignment and tunable carrier transport, yielding memristors with significantly reduced switching voltages and an on/off ratio of ∼2.6 × 104, approximately one order of magnitude higher than devices based on single-stacking α-In2Se3. These findings establish stacking order as a powerful structural parameter for tailoring ferroelectricity in 2D materials and introduce stacking-engineered polymorphic heterogeneity as a versatile platform for high-performance ferroelectric electronics and memory technologies.

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