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

Abstract

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.

Self-Assembly of Islands on Spherical Substrates by Surface Instability

“…In addition, the size of formed Ag core/SiO 2 shells in the vapor can be controlled by the base pressure, and the ratio of AgO 2 / SiO 2 powders determines the thickness of the SiO 2 layer. 44 Thus, we kept the mass ratio of Ag 2 O/SiO powders as 5:1, and the Ag core/SiO 2 shell microstructures with a radius of 1−10 μm were obtained by varying the base pressure within the range of 3 × 10 4 to 4 × 10 4 Pa. Then we annealed the system for 5 min before cooling it. The thickness of the SiO 2 layer can be measured as 150 nm from some broken structures similar to that in Figure 6d, and the thickness is approximately constant among the microstructures with various sizes due to the unchanged composition of the Ag 2 O/SiO precursor.…”

Development of a quantitative, portable, and automated fluorescent blue-ray device-based malaria diagnostic equipment with an on-disc SiO2 nanofiber filter

“…4a). The SiO 2 nanofiber was allowed to form only on the inside of the Si chip using the Vapour-Liquid-Solid (VLS) method 24,25 . The VLS method is a vapour phase growth method in which SiO 2 vapour is melted into liquid metal (platinum) particles and the nano solid phase (SiO 2 ) precipitates when SiO 2 reaches supersaturation 26 .…”

Synthesis of silicon dioxide cone shaped highly ordered hedgehog‐like microstructures on gallium droplets

“…Uniform, amorphous, and millimeter‐long silicon oxide nanowires for core‐shell samples on Ag droplet were obtained by Gao et al. . A triangular self‐aligned SiO 2 patterns were observed by Li et al.…”

“…In order to prepare ordered structures of core‐shell Ag‐SiO 2 , Li at al applied the VLS method. The process required relatively high temperatures above 1250°C, and the primary Ag‐core / SiO 2 ‐shell microstructures were prepared by thermal evaporation of mixed SiO and Ag 2 O powders onto polycrystalline sapphire substrates.…”