Controlled Growth of Gold Nanoparticles on Silica Nanowires

Production of gold nanoparticles with the specific goal of particle size control has been investigated by systematic variation of chamber pressure and substrate temperature. Gold nanoparticles have been synthesized on SiO₂ nanowires by plasma-enhanced chemical vapor deposition. Determination of particle size and particle size distribution was done using transmission electron microscopy. Average nanoparticle diameters were between 4 and 12 nm, with particle size increasing as substrate temperature increased from 573 to 873 K. A bimodal size distribution was observed at temperatures ≥723 K indicating Ostwald ripening dominated by surface diffusion. The activation energy for surface diffusion of gold on SiO₂ was determined to be 10.4 kJ/mol. Particle sizes were found to go through a maximum with increases in chamber pressure. Competition between diffusion within the vapor and dissociation of the precursor caused the pressure effect.