Abstract
Moiré interference effects influence profoundly the optoelectronic properties of vertical van der Waals structures. Here we systematically establish secondary electron imaging in a scanning electron microscope as a powerful technique for visualizing reconstruction of moiré lattices into registry-contrasting domains in vertical homobilayers and heteorbilayers of transition metal dichalcogenides (TMDs) with parallel and antiparallel alignment. With optimal parameters for contrast-maximizing imaging of high-symmetry registries, we identify distinct crystal realizations of WSe2 homobilayers and MoSe2–WSe2 heterostructures synthesized by chemical vapor deposition. In particular, we find evidence for a mutually exclusive competition between and registries, manifesting in complete reconstruction of bilayer crystals into one distinct registry or alternating large-area domains in and stacking. Our results have immediate implications for the optical properties of registry-specific excitons in layered stacks of TMDs, and demonstrate the general potential of secondary electron imaging for van der Waals twistronics.
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