Fast vapor phase growth of SiO2 nanowires via surface-flow on Ag core/SiO2 shell structure

Uniform, millimeter-long SiO2 nanowires were grown from co-evaporation of Ag2O and SiO powders. The ‘frozen’ growth scenario by cooling enables revelation of the vapor-liquid-solid mechanism here in action, which is generally inaccessible due to the high temperature and high pressure condition. Ag core/SiO2 shell preformed in the vapor and wetting the substrate will expose its liquid Ag-core to catalyze nanowire growth, at a rate over 10 nm/s, via viscous flow of the encasing SiO2 layer which precipitates through a liquid neck zone. This method is characteristic of high-yield of catalytic seeds free from overgrowth or consuming, easy control of wire thickness by vapor pressure adjustment, enhanced rooting ability since catalyst deposition on substrate becomes dispensable, etc. Also spinning growth of nanowires observed in many other circumstances can be explained by the viscous flow mechanism.