Chemical Vapor Deposition Growth of Vertical Graphene/WSe2 Heterostructures with Interlayer Twists

The interlayer twist is a new degree of freedom for forming moir & eacute; superlattices in 2D vertical heterostructures, which is expected to play an important role in the emerging field of twistronics. The constructions of heterostructures by transfer and re-stacking way have low efficiency and are prone to causing interface pollution. In this study, vertical molybdenum diselenide (WSe2)/graphene heterostructures with twisted angles are realized by using two-step chemical vapor deposition (CVD) growth strategy. The WSe2/graphene heterostructures exhibit Raman and photoluminescence (PL) responses of both WSe2 and graphene. The PL quenching of WSe2 in the heterostructures manifests that direct CVD growth is conducive to the formation of a cleaner interlayer interface between WSe2 and graphene layers, resulting in better interlayer coupling. The adhesion and surface potential differences indicate the formation of hetero-bilayer stacks. By analyzing the apparent growth orientations and crystal diffractions, vertical WSe2/graphene heterostructures exhibit a wide range of interlayer twisted angles (3.6-46.5 degrees). The difference between the growth behavior with twisted angles and the typical epitaxial growth mode may originate from the heterogeneous nucleation, leading to interlayer twists of the hetero-bilayers. These findings provide a facile protocol for the preparations of twisted hetero-bilayers and a material system for fundamental research of twistronics.