Facilitating Uniform\nLarge-Scale MoS₂,\nWS₂ Monolayers, and Their Heterostructures through van\nder Waals Epitaxy

Abstract

The fabrication process for the uniform large-scale MoS₂, WS₂ transition-metal dichalcogenides (TMDCs)\nmonolayers,\nand their heterostructures has been developed by van der Waals epitaxy\n(VdWE) through the reaction of MoCl₅ or WCl₆ precursors and the reactive gas H₂S to form MoS₂ or WS₂ monolayers, respectively. The heterostructures\nof MoS₂/WS₂ or WS₂/MoS₂ can be easily achieved by changing the precursor from WCl₆ to MoCl₅ once the WS₂ monolayer has been fabricated\nor switching the precursor from MoCl₅ to WCl₆ after the MoS₂ monolayer has been deposited on the substrate.\nThese VdWE-grown MoS₂, WS₂ monolayers, and their\nheterostructures have been successfully deposited on Si wafers with\n300 nm SiO₂ coating (300 nm SiO₂/Si), quartz\nglass, fused silica, and sapphire substrates using the protocol that\nwe have developed. We have characterized these TMDCs materials with\na range of tools/techniques including scanning electron microscopy\n(SEM), X-ray photoelectron spectroscopy (XPS), micro-Raman analysis,\nphotoluminescence (PL), atomic force microscopy (AFM), transmission\nelectron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX),\nand selected-area electron diffraction (SAED). The band alignment\nand large-scale uniformity of MoS₂/WS₂ heterostructures\nhave also been evaluated with PL spectroscopy. This process and resulting\nlarge-scale MoS₂, WS₂ monolayers, and their\nheterostructures have demonstrated promising solutions for the applications\nin next-generation nanoelectronics, nanophotonics, and quantum technology.