Morphology Engineering in Monolayer MoS₂-WS₂ Lateral Heterostructures

In recent years, heterostructures formed in transition metal dichalcogenides (TMDs) have attracted significant attention due to their unique physical properties beyond the individual components. Atomically thin TMD heterostructures, such as MoS₂-WS₂, MoS₂-MoSe₂, MoS₂-WSe₂, and WSe₂-WS₂, are synthesized so far via chemical vapor deposition (CVD) method. Engineering the morphology of domains including size and shape, however, still remains challenging. Here, a one-step CVD strategy on the morphology engineering of MoS₂ and WS₂ domains within the monolayer MoS₂-WS₂ lateral heterostructures through controlling the weight ratio of precursors, MoO₃ and WO₃, as well as tuning the reaction temperature is reported. Not only can the size ratio in terms of area between WS₂ and MoS₂ domains be easily controlled from less than 1 to more than 20, but also the overall heterostructure size can be tuned from several to hundreds of micrometers. Intriguingly, the quantum well structure, a WS₂ stripe embedded in the MoS₂ matrix, is also observed in the as-synthesized heterostructures, offering opportunities to study quantum confinement effects and quantum well applications. This approach paves the way for the large-scale fabrication of MoS₂-WS₂ lateral heterostructures with controllable domain morphology, and shall be readily extended to morphology engineering of other TMD heterostructures.