Controllable Epitaxial Growth of Large-Area MoS /WS Vertical Heterostructures by Confined-Space Chemical Vapor Deposition.

The controllable large-area growth of single-crystal vertical heterostructures based on 2D transition metal dichalcogenides (TMDs) remains a challenge. Here, large-area vertical MoS /WS heterostructures are synthesized using single-step confined-space chemical vapor epitaxy. The heterostructures can evolve into two different kinds by switching the H flow on and off: MoS /WS heterostructures with multiple WS domains can be achieved without introducing the H flow due to the numerous nucleation centers on the bottom MoS monolayer during the transition stage between the MoS and WS monolayer growth. In contrast, isolated MoS /WS heterostructures with single WS domain can be obtained with introducing the H flow due to the reduced nucleation centers on the bottom MoS monolayer arising from the hydrogen etching effect. Both the two kinds of the vertical MoS /WS heterostructures feature high quality. The photodetectors based on the isolated MoS /WS heterostructures exhibit a high responsivity of 68 mA W and a short response time of 35 ms. This single-step chemical vapor epitaxy can be used to synthesize vertical MoS /WS heterostructures with high production efficiency. The new epitaxial growth approach may open new pathways to fabricate large-area heterostructures made of different 2D TMDs monolayers of interest to electronics, optoelectronics, and other applications.