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.

Direct observation of van der Waals stacking-dependent interlayer magnetism.

Controlling the crystal structure is a powerful approach for manipulating the fundamental properties of solids. In van der Waals materials, this control can be achieved by modifying the stacking order through rotation and translation between the layers. Here, we observed stacking-dependent interlayer magnetism in the two-dimensional (2D) magnetic semiconductor chromium tribromide (CrBr), which was enabled by the successful growth of its monolayer and bilayer through molecular beam epitaxy.