c-SiO2samples were implanted withAg+at an energy of 200 keV to doses in the range of2.3–9×1016 ions/cm2at room temperature. At a dose of6.7×1016 ions/cm2,the transmission electron microscopy image shows that the implanted layer consists of two major sizes of nanoclusters: the large clusters, found in the deeper layer, are about 20 nm in diameter; the smaller clusters, found near the surface, are about 5 nm in diameter. At the relatively low dose of2.3×1016 ions/cm2,there is only one optical absorption band caused by surface plasmon resonance. At a higher dose, a splitting of the absorption band and the redshift are attributed to a dipole interaction between nanoclusters for a high density of nanoclusters.