Nanoclusters Formation in Ion Implanted Silicate Glasses

Glasses containing nanometer-sized metal clusters exhibit intensity-dependent refractive index values several orders of magnitude larger than that of silica glass, owing to dielectric and quantum confinement effects. Transition metals are particularly interesting since they also exhibit peculiar magnetic properties. Recently, the preparation of "mixed" colloidal structures, containing clusters of either different metals or metallic alloys, has also attracted attention due to the possibility of tailoring the performances of these composites. Ion implantation has been exploited as one of the most effective techniques for creating metal nanoclusters in glasses. In spite of the non-equilibrium characteristics of the ion implantation process, the important role of chemical driving forces has been recognized in determining the final configuration of ionimplanted materials, even more so when the process involves different sequentially implanted species. Both the ion implantation as a synthesis method and the nanometric dimension of the formed metallic particles can influence in a very complex way the alloy formation steps: in particular, the relative importance of the thermodynamic mechanism and the kinetic one is far from to be completely understood. In the following, we briefly summarize recently obtained results in this field. Detailed descriptions are reported in the publications.