Control of optical absorption of silica glass by Ag ion implantation and subsequent heavy ion irradiation.

For the samples implanted with 200 keV or 380 keV Ag ions to high fluence, an optical absorption peak appeared around 600 nm as well as the well-known surface plasmon resonance (SPR) peak around 400 nm, and Ag spherical nanoparticles with a high space density were observed. The absorption peaks around 600 nm can, therefore, be explained as due to the interaction among Ag nanoparticles (inter-particle interaction). By the subsequent irradiation with 16 MeV Au ions, the optical absorption around 400 nm and 600 nm showed a blue-shift and their peak intensity remarkably decreased. The TEM observation revealed an elongation of Ag nanoparticles along the direction of 16 MeV Au irradiation, and a resulting enlargement of the distances among the nanoparticles. The change in the peak wavelength and the peak intensity of the optical absorption by the 16 MeV Au irradiation can, therefore, be explained as originating from the decrease in the inter-particle interaction.