The clustering process of gold atoms in ion-implanted silica, during annealing in different atmospheres, is experimentally investigated and phenomenologically described. With respect to inert (Ar) or reducing (H2-Ar) atmosphere, annealing in oxidizing (air) atmosphere is the most effective in promoting cluster formation above 700–800°C due to a thermally activated correlated diffusion of gold atoms and excess oxygen molecules coming from the atmosphere

Light waveguides containing silver, introduced by ion-exchange process in soda-lime glass, has been annealed in hydrogen atmosphere at temperatures in the 120-250 degrees C range. Annealings cause a near-surface precipitation of metallic silver to form nanometer-size clusters with good uniformity in size and spatial distribution. Hydrogen permeation and ion-exchange between hydrogen and sodium (which remains in the glass matrix after silver-for-sodium exchange) are steps of the annealing process. A further step is the diffusion of silver ions towards the surface, and its eventual precipitation, with an activation energy close to that measured for silver-sodium interdiffusion in glasses of comparable composition

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A selective dealloying in bimetallic nanoclusters prepared by ion implantation has been found upon thermal annealing in oxidizing atmosphere or irradiation with light ions. In the first process, the incoming oxygen interacts preferentially with copper promoting Cu2O formation, therefore extracting copper from the alloy. In the second process the irradiation with Ne ions promotes a preferential extraction of Au from the alloy, resulting in the formation of Au-enriched "satellite" nanoparticles around the original AuxCu1-x cluster.