Growth of Transition Metal Dichalcogenides Ribbon Arrays via Droplet Motion Method

The controlled synthesis of transition metal dichalcogenide (TMD) ribbon arrays represents a promising route toward integrating 2D semiconductors into large-scale circuits. However, in ribbon synthesis, excessively large diameters of transition metal source droplets lead to a dominant non-directional surface driving force, which disrupts directional droplet migration and consequently hinders the growth of ribbon arrays. In this work, we leverage the surface energy difference to provide a driving force for the molten precursor droplets, while the atomic steps of the sapphire substrate impart directionality to this force. The introduction of Ni substantially reduced the droplet size, which significantly enhanced the efficacy of this directional driving force. Based on this approach, we successfully guided the directional migration of molten transition metal precursor droplets, thereby enabling the fabrication of highly aligned ribbon arrays. In situ visual chemical vapor deposition enables in situ observation of droplet-mediated growth, while density functional theory calculations and force analyses elucidate the underlying driving mechanisms. This work provides both a mechanistic framework and a versatile synthesis strategy for the scalable fabrication of well-aligned TMD ribbon arrays suitable for next-generation 2D semiconductor integration.