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

Cu nanoclusters embedded in silica glass were formed by ion implantation with different doses. Optical absorption spectra of the implanted samples showed peaks around 570 nm, attributed to the surface plasmon resonance (SPR) absorption of Cu nanoclusters. Optical absorption increased with the increasing of doses, but decreased for dose higher than 1.5×1017 ions/cm2 due to the surface-sputtering effect. The positions of resonance peaks were slowly red-shifted with increasing annealing temperature in oxidizing atmosphere. The red-shift is mainly attributed to the interaction of Cu nanoclusters with diffused oxygen from the oxidizing atmosphere. With increasing annealing temperature, a new absorption at 300 nm was observed while the absorption belonging to SPR disappeared. The formation of Cu nanoclusters was also observed by transmission electron microscopy measurement.