Effect of ultrasmall Au–Ag aggregates formed by ion implantation in Er-implanted silica on the 1.54 m Er3+ luminescence

Multiple implantations of Au and Ag ions in pure silica and Er-doped silica matrices have been performed to promote the formation of small Au–Ag alloy clusters. Upon annealing in N2 atmosphere at 600 C the structural investigation based on X-ray absorption spectroscopy at Au L3-edge detected for both cases the formation of Au–Ag alloy clusters, whose size is likely below 1 nm. The alloy composition is rich in Au; a minor part of Au atoms remains dispersed into the matrix and oxidized. In the Er-doped silica, the presence of these small alloy aggregates promotes a strong enhancement of the Er3+ luminescence at 1.54 microm, that is more marked with respect to similarly produced layers where only pure Au sub-nanometer clusters were present.