Vanadium-Assisted Epitaxy Growth of Wafer-Scale Bilayer Tungsten Disulfide Ferroelectric Semiconductor Single Crystals with High-Endurance Memory.

Abstract

Bilayer rhombohedral-stacked (3R) transition metal dichalcogenides (TMDCs) with switchable polarization expand the ferroelectric scope and provide a promising avenue to construct low-power and nonvolatile memory devices. However, epitaxy growth of wafer-scale 2D ferroelectric semiconductor single crystals is still on the way due to the challenge of phase structure and domain orientation control. Here, a vanadium-assisted epitaxy strategy is designed to synthesize two-inch bilayer 3R-WS₂ single crystals on c-plane sapphire. The introduction of vanadium not only increases the interlayer coupling to break the formation energy degeneracy between 3R- and hexagonal-stacked (2H) WS₂, but also promotes the parallel steps evolution on sapphire surfaces to induce the unidirectional bilayer domains nucleation. Ferroelectric semiconductor field-effect transistors with high endurance (more than 10⁵ cycles) and a large write/erase ratio (3.0 × 10⁵) are fabricated due to excellent polarization. This work represents a substantial leap in terms of controlling synthesis and memory device construction of wafer-scale 2D ferroelectric semiconductor single crystals, which should promote the further design of logic-in-memory chips to overcome von Neumann architecture bottlenecks.