Vertical Heterostructures of Layered Metal Chalcogenides by Van Der Waals Epitaxy for Solar Energy Conversion and Catalysis

Abstract

We report a facile chemical vapor deposition (CVD) growth of vertical heterostructures of layered metal dichalcogenides (MX2) enabled by van der Waals epitaxy for the first time. Few layers of MoS2, WS2, and WSe2 were grown uniformly onto microplates of SnS2 under mild CVD reaction conditions and the heteroepitaxy between them was confirmed using cross sectional transmission electron microscopy (TEM) and unequivocally characterized by resolving the large-area Moiré patterns appeared on the basal planes of microplates. Additional photoluminescence peaks were observed in heterostructures of MoS2-SnS2, which can be understood with electronic structure calculations to likely result from electronic coupling and charge separation between MoS2 and SnS2 layers. This work opens up the exploration of novel large-area heterostructures of diverse MX2 nanomaterials as the material platform for electronic structure engineering of atomically thin two-dimensional (2D) semiconducting heterostructures and novel device applications, such as in solar energy conversion. Furthermore, by controlling the nanostructures and polymorphs of group 6 MX2 (M = Mo, W; X = S, Se) materials, we have significant enhanced their catalytic activity in hydrogen evolution reaction for photoelectrochemical water splitting.