Atomistic mechanisms of seeding promoter-controlled growth of molybdenum disulphide

Seeding promoters facilitate the nucleation and growth of transition metal dichalcogenides in chemical vapor deposition (CVD). However, sophisticated roles of seeding promoter remain unclear. Here, adopting triangular-shaped crystal violet (CV) consisting of nonpolar and polar parts as the seeding promoter, we study the role of seeding promoter for the growth of molybdenum disulfide (MoS 2 ). We systematically control the geometrical configuration of CV on SiO 2 /Si substrate by changing the solvent polarity and find that it strongly affects the growth of monolayer or multilayer MoS 2 domains via CVD. Monolayer MoS 2 domains were predominantly grown on randomly lying-down CV configurations on SiO 2 /Si substrate, whereas multilayer MoS 2 domains are synthesized at concentrated polar parts in CV micelle on the substrate. Density functional theory calculations reveal that the initial nucleation step for the MoS 2 growth is the adsorption of S on CV and the most favourable S adsorption site is the polar part in CV. Furthermore, it is found that the CV adsorption to SiO 2 is mediated by the polar CV part and additionally strengthened in the lying-down CV configuration. Enhancing the thermal stability as well as hindering the re-aggregation of CV at high temperature, the lying down CV configuration allows the predominant growth of monolayer MoS 2 . This work provides a general framework to understand the growth of MoS 2 from aromatic seeding promoters.