The optical properties of Ag–Si nano-composite films prepared by sputtering

Ag–Si nano-composite films were prepared with a co-sputtering technique and step-sputtering method, respectively. The step-sputtered sandwich Ag–Si samples with Ag islands of area fraction approximately 0.43 showed strong resonance absorption near 610 nm. In contrast, the resonance absorption was widened and weakened in the co-sputtered Ag–Si films with the Ag volume fraction at approximately 0.26. The effective dielectric function of the composite materials consisting of multi-stage nanosized metal particles (or clusters) was deduced based on the theory of Sheng. The calculated absorptive coefficients from this modified model coincides very well with the measured spectra of co-sputtered Ag–Si composite films.