Unveiling the Growth Mechanism of MoS 2 with Chemical Vapor Deposition: From Two-Dimensional Planar Nucleation to Self-Seeding Nucleation

The deep understanding of nucleation and growth mechanisms is fundamental for the precise control of the size, layer number, and crystal quality of two-dimensional (2D) transition-metal dichalcogenides (TMDs) with the chemical vapor deposition (CVD) method. In this work, we present a systematic spectroscopic study of CVD-grown MoS 2, and two types of MoS 2 flakes have been identified: one type of flake contains a central nanoparticle with the multilayer MoS 2 structure, and the other is dominated by triangular flakes with monolayer or bilayer structures. Our results demonstrate that two types of flakes can be tuned by changing the growth temperature and carrier-gas flux, which originates from their different nucleation mechanisms that essentially depends on the concentration of MoO 3– x and S vapor precursors: a lower reactant concentration facilitates the 2D planar nucleation that leads to the monolayer/bilayer MoS 2 and a higher reactant concentration induces the self-seeding nucleation which easily produces few-layer and multilayer MoS 2 . The reactant-concentration dependence of nucleation can be used to control the growth of MoS 2 and understand the growth mechanism of other TMDs.