Evolution of nanoparticles in gold-implanted glass

The interest in metal nanocrystals is focused on their nonlinear optical properties, as they are expected to have a large third-order nonlinear susceptibility. In order to explore the possibility of tuning the size and shape of metal nanocrystals, we implanted gold into fused silica substrate. The implantation energy was 1.1 MeV and doses were of 1, 3, and 6×1016 ions/cm2. All samples were subsequently annealed in air at 1000 and 1100 °C. Grazing incidence small-angle X-ray scattering was used to study the morphology and the distribution of gold nanoparticles formed in the substrate. The clustering process is evident already during the implantation itself. Upon annealing, the number of clusters, as well as their size is increased. The clusters are smaller in the vicinity of the surface, where the effective implant concentration is lower, regardless of the annealing temperature. At the highest annealing temperature the clustering diverges into two distinct size distributions.