Relations between the optical properties of Cu–Ag:Si3N4 nanocermets and the microstructure of the metallic nanoclusters

Ion beam sputtering has been used to prepare Ag/Cu, Ag and Cu nanoclusters embedded in a Si3N4 dielectric matrix with the goal to correlate structural information and optical properties. The optical transmittance spectra of the bimetallic nanoclusters are compared with those obtained in the case of the single metallic nanocermets in the as-deposited state. The influence of a post annealing treatment, at different temperatures, on the optical properties of the bimetallic nanocermets is also discussed. The nanocluster structure has been investigated by X-ray absorption spectroscopy and X-ray diffraction. The chemical composition has been analysed by Rutherford backscattering spectroscopy. The surface plasmon resonance occurring after annealing in a definite temperature range is interpreted as due to the specific atomic arrangement resulting from this treatment.