Raman scattering studies on silver nanoclusters in a silica matrix formed by ion-beam mixing

The formation and growth of nanoscale silver clusters in silica matrices ar e studied by means of optical absorption and Raman scattering spectroscopy. The metallic silver layer of the Ag/SiO2 couple was irradiated by argon io ns for ion-beam mixing of silver with the silica matrix. Postannealing of t he embedded Ag atoms in silica matrices results in the growth of Ag nanoclu sters. The quadrupolar surface acoustic vibrational mode of the Ag nanoclus ters has been observed in low-frequency Raman scattering experiments. The a verage size of these Ag nanoclusters is estimated from the quadrupolar mode frequency. Systematic growth of Ag nanoclusters embedded in silica matrice s is observed with the increase of postannealing temperature. We have estim ated the activation energy for the diffusion of Ag atoms in irradiated a-Si O2 from the coarsening of these embedded Ag atoms. Development of a peak at about 3 eV in the optical absorption spectra for the samples postannealed at higher temperatures corroborates further the growth of Ag nanoclusters i n the silica matrices. New Raman modes at 1368 and 1573 cm(-1) are observed in Ag embedded silica samples and the possible origin of these modes is di scussed. (C) 2000 American Institute of Physics. [S0021-8979(00)03420-4].