Effective permittivity of co-evaporated metal-organic mixed films

The combination of organics and metals in a composite film holds promise for combining plasmonic interaction with gain and for the realization of epsilon-near-zero (ENZ) metamaterials. In particular, fluorescent organic dyes can be used to compensate the plasmonic losses of a homogenized metal-organic material. Here, we fabricate such films through thermal co-evaporation of silver and an organic host:guest system and investigate experimentally the resulting linear optical properties for varying metal concentrations. We extract the effective permittivity of the resulting films with ellipsometry measurements and demonstrate the formation of silver nanoparticles, resulting in strongly localized surface plasmon resonances until a percolation threshold is reached. Through enhanced light-matter interaction, we observe a maximum of the photoluminescence for a concentration of 15% in volume of metal in the composite material. These results showcase a variety of growth parameters and will be useful for the future design of gain-compensated plasmonics and ENZ metamaterials