Metal Seed Loss Throughout The Nanowire Growth: Bulk Trapping And Surface Mass Transport

The physical and chemical properties of metal-catalyzed semiconductor nanowires are very sensitive to their composition and morphology, which are very sensitive to the behavior of the catalyst nanodroplet during growth. Herein, we identify and investigate the main atomic pathways and processes governing the metal mass transport and the associated variation in the nanodroplet size throughout the growth of metal-catalyzed silicon nanowires. This includes surface diffusion and catalyst trapping in addition to the shift in phase boundaries of the eutectic nanodroplet to count for surface effects, capillarity, and related nanoscale stresses. On the basis of thermodynamic and kinetic considerations, a theoretical framework is presented to elucidate these catalyst nanodroplet instabilities. Moreover, we also address the influence of these phenomena on the shape and impurity concentration in silicon nanowires. Modeling results along with experimental data demonstrate that the combined effects of the kinetically driven catalyst trapping and surface diffusion play the key role in tailoring the nanowire morphology and composition. The proposed model can be extended straightforwardly to describe the evolution of the morphology during the growth of any other system of metal-catalyzed semiconductor nanowires.