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Optical properties and effective dielectric function of nanostructured materials consisting of silver nanoparticles
embed in dielectric matrix were studied. Experimental part was performed by means of angular and spectroscopic
ellipsometry. Measured angular dependences reveal, that optical conductivity changes from metallic to dielectric with
decrease of silver volume fraction. Complex effective dielectric function of the samples was measured within 295-825
nm wavelength range. Dispersion of optical constants of the samples with high silver volume fractions f<0.53 appears to be qualitatively similar to bulk silver. With decrease of Ag concentration influence of plasmon resonance on optical
properties of the samples is observed. Measured spectral dependences reveal redshift and significant broadening of
plasmon resonance peak of sample with f=0.28 in comparison to those with f=0.06-0.15 which can be explained within framework of surface plasmon resonance theory. Calculations show, that experimental data can’t be described using standard Maxwell-Garnett and Bruggeman effective-medium theories.
Effective dielectric function of such composite films can be tuned by varying silver concentration, size and shape of the metal particles. We show that measured values of complex index of refraction for samples with f=0.08-0.2
can guarantee a strong light absorption for 400 nm film thickness according to Fresnel equations and demonstrate, that a considerable fraction of light can be trapped in the film due to total internal reflection of the light, scattered by noble metal nanoparticles.
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