ADICT: Growth of MoS2 Using Molecular Beam Epitaxy

Since the synthesis of graphene in 2004 [1], interest in two-dimensional (2D) materials has significantly increased, particularly focusing on transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS2). These materials offer exceptional electronic, mechanical, and optical properties at the atomic scale, and their bandgap is tunable depending on the number of layers [2], making them ideal for advanced electronic, and optoelectronic devices. However, synthesizing highquality 2D materials on an industrial scale remains a challenge. Although Chemical Vapor Deposition (CVD) and Pulsed Laser Deposition (PLD) offer more scalable alternatives, they encounter issues related to thickness uniformity and purity control. In this context, Molecular Beam Epitaxy (MBE) has emerged as a leading technique for growing TMDs (such as MoS2), thanks to its precise control over deposition parameters and the ability to monitor growth in situ using techniques such as Reflection High-Energy Electron Diffraction (RHEED). Our study demonstrates a growth of MoS2 layers on GaN/sapphire substrates using Molecular Beam Epitaxy (MBE). Morphological characterization via Atomic Force Microscopy (AFM) revealed the formation of triangular MoS2 domains on the GaN surface. Raman spectroscopy analysis of the E12g and A1g modes showed distinct peak separations, confirming the formation of monolayer and bilayer MoS2 on the GaN substrate. High-Resolution Scanning Transmission Electron Microscopy (HR-STEM) was employed to investigate the interface between MoS2 and GaN.