Hybrid Alkali Salt Catalysts‐Promoted CVD Growth of 2D MoSe2–WSe2 and WSe2–MoSe2 Lateral Heterostructures

Abstract A scalable growth of atomically‐thin 2D transition metal dichalcogenides (TMDs) with defect‐free large‐area surfaces is crucial for developing high‐performing optoelectronic devices. Herein, a method to grow large‐area, high‐quality MoSe 2 monolayers, MoSe 2 –WSe 2 , and WSe 2 –MoSe 2 lateral heterostructures using molten salt‐based chemical vapor deposition (CVD) is systematically reported. First, effects of isolated inorganic (sodium chloride (NaCl) and sodium nitrate (NaNO 3 )), organic (Perylene–3,4,9,10–tetracarboxylic acid tetrapotassium salt (PTAS), mixed inorganic (NaCl/NaNO 3 ), and hybrid organic–inorganic (PTAS/NaCl/NaNO 3 ) salt catalysts on the CVD growth and optoelectronic quality of MoSe 2 monolayers and their lateral heterostructures with WSe 2 in MoSe 2 –WSe 2 and WSe 2 –MoSe 2 assemblies are investigated. Results show that molten salt catalysts (NaCl/NaNO 3 and PTAS/NaCl/NaNO 3 ) support high‐quality, large‐area growth of MoSe 2 monolayers with low defect density. The mixed inorganic salt supports growth of MoSe 2 –WSe 2 lateral heterostructures but not their counterpart. Meanwhile, WSe 2 –MoSe 2 lateral heterostructures are optimally grown, supported by the hybrid organic–inorganic salt. These results are ascribed to the difference in the associated kinetic and thermodynamic mechanisms for the growths of MoSe 2 and WSe 2 as starting materials. Last, it is confirmed that optoelectronic quality of realized heterostructures and monolayers is improved compared to their mechanically exfoliated counterparts. The obtained high‐quality, large‐area 2D TMD heterostructures can be useful for various optoelectronic applications.