Control of optical absorption band due to Cu/Ag nanoparticles in SiO₂ glass by dual ion implantation of Cu^- and Ag^-

Optical absorption properties of Cu and Ag double metal negative-ion-implanted silica glasses have been investigated from a standpoint of controlling absorption band due to surface plasmon resonance of nanoparticles. Three silica glasses were implanted with Cu negative ions at 30, 60 and 90 keV, respectively, with dose of 1 × 10¹⁷ ions/cm². Then, Ag negative ions were implanted into each sample at a constant condition of 40 keV and 5 × 10¹⁶ ions/cm². Optical absorption spectra were measured after annealing at various temperatures for 1 hour in Ar gas flow. In all samples annealed at 500°C and below, intense and wide absorption with a peak of 2.6-2.8 eV was observed, and the peak position was moved to higher energy with increase in annealing temperature. These absorption peaks were considered to be due to Cu-Ag alloy nanoparticles. After annealing at 600-800°C, a sharp and intense absorption peak was observed for all the samples at photon energy of 3.1 eV, of which the absorption corresponded to that due to surface plasmon resonance of pure silver nanoparticles.