Strain-Engineered Method for Atomically Sharp Interfaces in 2D TMDC Lateral Heterostructures

While strain is widely used to tune the properties of two-dimensional transition-metal dichalcogenides (TMDCs), its role in controlling chalcogen exchange and alloy formation at interfaces of lateral heterostructures (LHSs) needs further exploration. Here, we demonstrate that the tensile strain in monolayer WSe₂ controls the atomic sharpness of interfaces formed during subsequent MoS₂ growth. Using a two-step chemical vapor deposition (CVD) process on Al₂O₃ (0001), highly tensile-strained WSe₂ suppresses chalcogen intermixing, whereas strain-relaxed WSe₂ promotes alloy-mediated interfacial evolution. Density functional theory (DFT) calculations reveal how tensile strain modifies vacancy formation, substitutional energetics, and alloy stability, while high-resolution scanning transmission electron microscopy (HR-STEM) confirms the sharp atomic interfaces in high-strain WSe₂. Together, these results establish tensile strain as a control parameter for lateral interface formation in TMDC heterostructures and provide a generalizable strain-engineering strategy for scalable fabrication of precise 2D LHSs for electronic and optoelectronic applications.