Self-Expanding Molten Salt-Driven Growth of Patterned Transition-Metal Dichalcogenide Crystals

Transition-metal dichalcogenides (TMDs) have been considered potentialmaterials for the next generation of semiconductors. Realizing controllable growth of TMDcrystals is a prerequisite for their future applications, which remains challenging. Here, wereveal a new mechanism of self-expanding molten salt-driven growth for a salt-assisted methodand achieve the patterned growth of TMD single-crystal arrays with a size of hundreds ofmicrometers. Time-of-flight secondary ion mass spectroscopy and other spectroscopycharacterizations identify the component of the molten salt solution. Microscopiccharacterizations reveal the existence of salt solution as an interlayer between a TMDmonolayer and the silicon substrate as well as particles along the crystal edge. The edged saltsolution serves as a self-expanding liquid substrate, which confines the reactive sites to thelocalized liquid surface, thus avoiding random nucleation. The surface reaction also assuresmonolayer crystal formation due to self-limiting growth. Besides, the liquid substrate affordssources and spreads itself continuously owing to the nonwetting effect on TMD crystals, thereby facilitating the continuousextension of the TMD monolayer. This work provides novel insights into the controllable synthesis of TMD monolayers and pavesthe way for the fabrication of TMD-based integrated functional devices