Effect of thermal annealing on the optical properties of high-energy Cu-implanted silica glass

Abstract Silica glasses implanted with 2 MeV Cu+ ions at various doses from 9.95 × 1016 to 2.2 × 1017 ions/cm2 were thermally annealed in air in between 600°C and 1050°C. Rutherford backscattering measurements were used to determine the concentration of implanted ions and their distributions in the samples. The Cu distribution in the samples depended on the implantation dose. Optical absorption spectra, measured in between 200 and 800 nm at room temperature, revealed a peak at about 560 nm, attributed to colloidal Cu particles, for all the samples even before heat treatment, which indicates the formation of particles even at lower doses, when high energy implantation is used. Using the equation derived from the framework of free-electron theory, the average radii of the Cu particles were determined from the experimental surface plasmon absorption peaks. The average radius of Cu particles decreased slightly on annealing at 600°C, suggesting the formation of additional small Cu precipitates at this temperature. However, the average radius of Cu particles increased as the annealing temperature increased from 800°C to 1050°C. The anomalies between the calculated average radius of the particles and the absorption peak positions at higher annealing temperatures were explained.