Vacancy Cluster-Mediated Epitaxial Layer-by-Layer Growth of van der Waals Heterostructures.

Two-dimensional transition metal dichalcogenide heterostructures offer a versatile platform for tailoring quantum and optoelectronic properties, yet their scalable synthesis remains challenging due to the inert nature of van der Waals (vdW) basal planes, which lack nucleation sites for epitaxy. Here, we report a vacancy cluster-mediated epitaxial layer-by-layer growth strategy that enables the deterministic construction of vdW heterostructures with atomic precision. Hydrogen plasma treatment generates chalcogen vacancy clusters on template monolayers, providing localized nucleation sites for subsequent overlayer growth. This process yields highly crystalline heterostructures, as confirmed by atomic-resolution scanning transmission electron microscopy and density functional theory, while postgrowth annealing under chalcogen-rich conditions heals interface vacancies, restoring optical quality and enabling robust interlayer excitonic coupling. Using this approach, we demonstrate versatile MoS2/WS2, MoSe2/WSe2, bilayer MoS2, and MoS2/MoSSe heterostructures, all exhibiting atomically sharp interfaces and epitaxial alignment. Our results establish vacancy cluster-mediated epitaxy as a general platform for programmable stacking of two-dimensional materials, advancing the scalable design of functional vdW solids.