Study on the Morphological Mechanism of MoS2 Growth by NaCl-Assisted Chemical Vapor Deposition

Monolayer MoS2 is a two-dimensional transition-metal dichalcogenide (TMD), and its atomic-level thickness makes it an appealing research target in beyond-silicon devices. Future practical uses are intimately related to controllable synthesis of materials at present, and salt-assisted chemical vapor deposition (SA-CVD) offers a promising way. However, the specific growth mechanism of alkali metal salts on MoS2 crystal development and their influence on optoelectronic characteristics of the as-grown MoS2 crystals is not fully identified. Here, based on large amount experiments, we present a vapor-liquid-solid (VLS) edge-adsorbed growth model for synthesizing MoS2 nanoflakes, emphasizing the edge-adsorbed phenomena of the alkali metal element Na in regulating MoS2 crystal shape. Through controlling flow rate of carrier gas, the MoS2 defective morphology can be effectively suppressed. This study contributes to a better understanding of the role of alkali metal halide salts in TMD development by providing experimental and theoretical evidence, which is critical for synthesizing high quality TMD by alkali metal halide salts catalyst.