Hole-doping-assisted epitaxial growth of wafer-scale rhombohedral-stacked bilayer transition-metal dichalcogenides single crystals

Bilayer rhombohedral-stacked transition-metal dichalcogenides (3R-TMDCs) combining high carrier mobility, good electrostatic control, and exotic switchable polarization are emerging as promising semiconducting channels for beyond-silicon electronics. However, despite great efforts, the growth of wafer-scale bilayer 3R-TMDCs single crystals remains difficult due to challenges in the synergistic control of phase structure and grain orientation. Here we design a hole-doping-assisted strategy to synthesize a series of two-inch bilayer 3R-TMDCs single crystals on c-plane sapphire. The introduction of hole dopants (e.g. Hf, V, Nb, Ta) not only increases the interlayer coupling to break the formation energy degeneracy of bilayer 3R-stacked and hexagonal-stacked TMDCs, but also promotes the parallel steps formation on sapphire surfaces to induce the unidirectionally aligned bilayer grain nucleation. The fabricated ferroelectric semiconductor field-effect transistors based on bilayer Hf-MoS₂ demonstrate high endurance (more than 10⁵ cycles) and long retention time (exceeding one year) due to the restriction of interlayer charge defect migration/aggregation caused by sliding ferroelectricity. This work proposes a promising strategy for synthesizing wafer-scale ferroelectric semiconductor single crystals, which could promote the further exploration of logic-in-memory chips.