Engineering band structures of two-dimensional materials with remote moiré ferroelectricity.

The stacking order and twist angle provide abundant opportunities for engineering band structures of two-dimensional materials, including the formation of moiré bands, flat bands, and topologically nontrivial bands. The inversion symmetry breaking in rhombohedral-stacked transitional metal dichalcogenides endows them with an interfacial ferroelectricity associated with an out-of-plane electric polarization. By utilizing twist angle as a knob to construct rhombohedral-stacked transitional metal dichalcogenides, antiferroelectric domain networks with alternating out-of-plane polarization can be generated.

Dual-coupling-guided epitaxial growth of wafer-scale single-crystal WS monolayer on vicinal a-plane sapphire.

The growth of wafer-scale single-crystal two-dimensional transition metal dichalcogenides (TMDs) on insulating substrates is critically important for a variety of high-end applications. Although the epitaxial growth of wafer-scale graphene and hexagonal boron nitride on metal surfaces has been reported, these techniques are not applicable for growing TMDs on insulating substrates because of substantial differences in growth kinetics. Thus, despite great efforts, the direct growth of wafer-scale single-crystal TMDs on insulating substrates is yet to be realized.