Optical absorption of nanoclusters by sequentially implanting into SiO2 glass and subsequently annealing in a selected atmosphere

Abstract

Ag and Cu ions were implanted sequentially into SiO2glass by using a metal vapor vacuum arc (MEVVA) source in the room temperature. Both of the doses were 5×1016 ions/cm2The accelerated voltage for Ag was 43kV and for Cu 30kV with the ion flux density～2mA/cm2The valence states of composite sa mples were observed in details by x-ray photoelectron spectroscopy (XPS). The results showed that there were metallic Ag and Cu and CuO in the sample. The formation of alloy nanoclusters have been evidenced by selected area electron diffraction (SAED), energy dispersive xray spectra (EDS) and optical absorption spectra which fit the result of theoretical simulation well. After annealed at different temperatures for 1h in either oxidizing (air) or reducing(70%N2+30%H2 gas mixture, gas pressure 20Pa) atmosphere, the absorption peaks shifted to blue and appeared a new peak during annealing in reducing atmosphere. Applying the free electron model of metal particles, we have calculated the average size of nanoclusters annealed at different temperatures, the results showed that the size of nanoclusters increased gradually with the enhancement of temperature. AgCu alloy nanoclusters were decomposed after annealing in oxidizing atmosphere. Cu atoms migrated to the surface of the sample and are oxidized; Ag nanoclusters were formed due to low oxygensilver interaction. For the sample annealed in reducing atmosphere, the alloy decomposed to Ag and Cu nanoclusters.