Imaging lattice reconstruction in homobilayers and heterobilayers of transition metal dichalcogenides

TL;DR

This paper demonstrates the use of secondary electron imaging in a scanning electron microscope to visualize lattice registry and reconstruction in transition metal dichalcogenide bilayers, revealing insights into their optoelectronic properties.

Contribution

It introduces a novel imaging technique for directly visualizing lattice registry in TMD bilayers, advancing the understanding of moiré phenomena in van der Waals heterostructures.

Findings

Distinct crystal registries identified in bilayers

Ubiquitous lattice reconstruction observed in assembled bilayers

Implications for optical properties of registry-specific excitons

Abstract

Moir\'{e} interference effects have profound impact on the optoelectronic properties of vertical van der Waals structures. Here we establish secondary electron imaging in a scanning electron microscope as a powerful technique for visualizing registry-specific domains in vertical bilayers of transition metal dichalcogenides with common moir\'e phenomena. With optimal parameters for contrast-maximizing imaging of high-symmetry registries, we identify distinct crystal realizations of WSe$_2$ homobilayers and MoSe$_2$-WSe$_2$ heterobilayers synthesized by chemical vapor deposition, and demonstrate ubiquitous lattice reconstruction in stacking-assembled bilayers with near parallel and antiparallel alignment. Our results have immediate implications for the optical properties of registry-specific excitons in layered stacks of transition metal dichalcogenides, and demonstrate the general potential of secondary electron imaging for van der Waals twistronics.