Ellipsometric study of optical properties of liquid Ga nanoparticles

The investigation of the optical properties of liquid Ga nanoparticles embedded in a dielectric matrix by means of spectroscopic ellipsometry is reported. The particles, which have the shape of truncated spheres and a radius which is varied in a controlled way between 5 and 16 nm, are grown by the evaporation-condensation technique. The results are discussed in terms of the current effective medium models and give new information on the distribution of the particles in the matrix as well as on their optical properties. A resonance peak due to the plasmon-polariton electron excitations in the particles is observed in the imaginary part of the effective dielectric function of the layer. Its position shifts to higher photon energies and the half width of the resonance increases with the decrease of the particle size. The dielectric function of the particles is parametrized using the Drude dispersion equation. The obtained electron damping parameter increases with the decrease of the particle size in accordance with the predictions of the size theories of the optical properties of small particles.