When an array of small metallic particles is embedded into a dielectric matrix one should expect a pole in the polarizability of the medium at certain energy, when the negative real part of the dielectric function of the metal compensates the double value of the positive real part of the dielectric function of the surrounding dielectric material. This gives rise to so called Froelich resonance in the optical properties of such metamaterial.
We discovered and investigated a resonance in optical absorption, which originates from localized plasmon excitations in a self-organized system of metal AsSb nanoparticles embedded in a semiconductor AlGaAs matrix.
The AsSb-GaAlAs metamaterial was produced by a low-temperature molecular-beam epitaxy on the (001) GaAs substrates followed by a high-temperature annealing. Our transmission electron microscopy study revealed a system of almost spherical AsSb inclusions in the crystalline AlGaAs matrix. The average diameter of the inclusions was 6 nm. The filling factor was about 0.2%.
The Froelich plasmon resonance in our metamaterial was revealed at 1.48 eV with a bandwidth of 0.18 eV. The absorption coefficient within the resonant band was as large as 9000 cm-1. The observed optical properties were theoretically considered in terms of either Mie scattering or Maxwell-Garnett effective medium. We used well documented data for the dielectric properties of AlGaAs and Drude model for the electron system in the metal AsSb nanoinclusions. A reasonably good description was achieved in both approaches.