Electronic Properties of Semiconductor and Metallic Clusters

The investigation of the structures in the nanometer domain presents rather challenging aspects in terms of experimental characterization and theoretical calculations for the prediction and/or interpretation of their basic properties. To summarize in one sentence, it can be stated that space confinement plays a key role in modeling and tuning the physical properties of nanocrystals

Infrared study of iron impurities in polycrystalline solar grade silicon

In this work the role of Fe impurities introduced in boron doped polycrystalline solar grade silicon is examined by means of low temperature absorption measurements in the far infrared. In particular, the results can be explained in term of formation of boron acceptor-iron donor complexes

Early stages of growth of Ge quantum dots

The present work is concentrated on the investigation of the initial stages of growth of Ge nanoparticles embedded in an amorphous A1203 matrix on suitable substrates. The growth technique is based on self-organization processes related to the balance of the interface energies involved. Combined data from complementary optical techniques (absorption, Raman scattering, spectroscopic ellipsometry) give evidence of a behaviour which can be ascribed to the existence of a wetting layer, not detectable by conventional transmission microscopy

Optical properties of Cd(1-x)Mn(x)Te/Cd(1-y)Mn(y)Te superlattices with high difference of Mn concentration between wells and barriers

We studied the optical properties of Cd(1–x)Mn(x)Te/Cd(1–y)Mn(y)Te semiconductor superlattices with medium (x=0.3,y=0.01) and high (x=0.8,y=0) difference of the Mn concentration between wells and barriers, by means of photoluminescence and photoreflectance spectroscopy. Photoluminescence allows us to study the emission due to the fundamental heavy (H) hole 11H interminiband excitonic transition and evidences the emission characteristics. Photoreflectance reveals several heavy and light (L) holes interminiband excitonic transitions, up to the 33H. The experiments are in good agreement with the theory with an envelope-function approximation approach, taking into account strain effects due to lattice mismatch between wells and barriers. The combined use of photoluminescence and photoreflectance gives a complete information on the electronic configuration of these Cd(1–x)Mn(x)Te/Cd(1–y)Mn(y)Te superlattices that can find specific applications in spintronic devices

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