Periodically twinned nanowires and polytypic nanobelts of ZnS: The role of mass diffusion in vapor-liquid-solid growth.

There are two mass diffusion processes regarding the vapor-liquid-solid (VLS) growth of nanostructures: one is inside the catalyst droplet toward the liquid-solid interface; the other is along the side surface planes of the growing nanostructures. In this letter, microscale, modulated mass diffusion scenarios are exhibited through the synthesis of two types of ZnS nanostructures in an Au-catalyzed VLS process: periodically twinned nanowires originated from periodical fluctuation between diffusion rate inside the catalytic droplet and the growth rate on the liquid-solid interface; the formation of asymmetrically polytypic nanobelts is related to one certain side surface bounded by high surface-energy plane, which serves as a preferential diffusion direction of reactant adatoms. The results may have important impact on the understanding of the physical and chemical process of the VLS mechanism. These longitudinally and latitudinally tunable crystalline structures enrich the family of one-dimensional nano-building blocks, and may find potential applications in nanotechnology.