Metal nanoclusters embedded in silica glasses

Metal nanoclusters (NCs) embedded in insulating matrices have received in the last decade an increasing interest due to their optical, magnetic and catalytic properties when their size becomes comparable to or less than the electronic mean free path [1–8]. Metallic NCs embedded in glass can increase for instance the optical third-order susceptibility CHI(3) of the matrix by several orders of magnitude, making such systems inter- esting candidates to be used as optical switches [3, 9]. With respect to the monoelemental case, bimetallic nanoclusters have an additional way for controlling NCs properties, i.e., the composition. Of course, before the ”tunability” of the NCs properties can be used for actual devices, a careful control over alloy clusters synthesis and stability has to be achieved, in order to clarify which are the parameters (i.e., implantation conditions, subsequent thermal or laser annealings, ion irradiation, etc.) that can promote separation (via oxidation, for instance) instead of alloying of the implanted species. Moreover, the composition of the clusters can be varied easily by sequential ion implantation in the matrix of two different elements, whose energy and dose can be tailored so as to maximize the overlap between the implanted species and to control their local relative concentration. In this work two case studies related to embedded nanoclusters will be addressed: i) de-alloying of bimetallic Au-Ag nanoclusters under ion irradiation, ii) metallic nanoclusters for lustre decoration.