Simulation of optical properties of layered metallic nanoparticles embedded inside dielectric matrices: interference method or Maxwell Garnett effective-medium theory?

摘要

Optical characterization of composite films consisting of a ceramic matrix with embedded layered metal nanoparticles have recently received increasing interest. In particular, two methods have been mainly proposed in order to obtain optical performances of dielectric matrices containing layered nanoclusters (NCs): the first method is based on the simulation of the layered system as composed of alternated films of dielectric material and effective-medium material. Therefore, the optical response of the multilayer stack is calculated, assigning to the effective-medium layers the dielectric constant (epsilon)_(f)~(Yama), obtained by the Yamaguchi theory, and calculating the interference between the beams reflected and refracted at each interface inside the stack. The second method considers the multilayer stack as a single-layer effective-medium film whose dielectric constant is calculated by the Maxwell Garnett (MG) theory. In particular, this second method is recognized to be valid in the case of nanoparticles uniformly distributed inside a dielectric matrix. The present study shows that the interference method, as it has been applied up to now, does not allow reproducing reflectance and transmittance spectra calculated by the MG theory in the case of a uniform distribution of NCs.