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A systematic X-ray absorption spectroscopy investigation of the local coordination in gallium nanostructures has been performed as a function of temperature and particle size. It is shown that the nanostructure strongly affects the polymorphism of solid gallium and the (meta)stability range of the liquid phase (in agreement with previous works) and that the surface tension acts in the same direction as hydrostatic pressure in stabilizing the Ga solid phases. The effect of surface free energy is first to favor the metallic arrangement of the delta phase and then to stabilize a liquid-like phase based on dimeric molecules even at 90 K. The Ga-Ga distance in the dimers is lower in the liquid phase than in the alpha solid. The experimental results are discussed in comparison with molecular dynamic calculations to assess the presence of covalent character of the dimeric Ga-2 units in liquid nanostructured gallium.

Cd1−xMnxTe/CdTe superlattices and thin films were grown by molecular beam epitaxy on GaAs (001) substrates. Spectroscopic ellipsometry measurements were performed on Cd1−xMnxTe/CdTe superlattices with compositions x = 0.4, 0.8, and Cd1−xMnxTe thin films with x = 0.2, 0.4, 0.6 at room temperature in the photon energy range 1.4–5 eV. In superlattices the pseudodielectric functions measured by ellipsometry show specific features related to the exciton transition between quantized interbands. The exciton transitions related to the heavy holes of 11 H, 22 H, and 33 H are observed and identified. In thin films spectroscopic ellipsometry allows the clear identification of the energy gap E0. Additionally, critical point transitions are observable in both the spectra of the superlattices and films. Photoreflectance spectra were also performed at room temperature in order to compare with our ellipsometry results. After taking into account the strain-induced and quantum confinement effects, the theoretical calculations are in good agreement with our experimental spectra. Ellipsometry appears to be a suited technique to monitor the MBE growth, ultimately also in situ, of diluted magnetic low-dimensional systems.

We report on second-harmonic generation from Ga nanoparticle monolayers embedded in a dielectric transparent matrix for different average radii and at different temperatures. The nanoparticles are produced in the liquid phase by means of a self-organized process in ultra high vacuum (Vollmer–Weber mode). The measurements show a strong size dependence of the second-harmonic signal. A wide hysteresis cycle appears in correspondence of the melting–solidification process. The experimental results have been analyzed through a nonlinear Mie scattering model and explained in terms of the coupling of SH radiation with surface plasma oscillations in the nanoparticles.

I had the opportunity to meet Prof. Rinaldo Castello in the mid-80s of the last century, shortly after he joined the Department of Electrical Engineering of the University of Pavia.

Atomic force microscopy (AFM) is recognized a suitable and powerful technique for surface and morphological analysis. Even if until now this technique has not been frequently used in the pharmaceutical field, it can contribute to an accurate morphologic characterization of microspheres and nanospheres. In this work, atomic force microscopy has been used to perform the surface characterization of sterilized microspheres. The aim is to investigate the morphologic modifications induced by gamma irradiation on poly(lactide-co-glycolide) microspheres loaded with ovalbumin and to compare the results obtained by AFM to those obtained by scanning electron microscopy (SEM). The results obtained show that, with respect to SEM, AFM can give some additional information regarding the modifications induced by gamma-irradiation on microspheres surface morphology. The significant changes in surface roughness after irradiation are indicative of damage due to gamma-irradiation. The unchanged surface roughness values calculated for microspheres containing PEG in their matrix, suggest that this polymer exerts a protective effect towards gamma-irradiation.

The interstitial oxygen profile across the epitaxial silicon and Czochralski silicon interface has been determined using a micro Fourier transform infrared technique. Systematic measurements performed in transversal wafer cross-section configuration demonstrate the presence of interstitial oxygen in the epitaxial layer, clearly indicating that solid state outdiffusion from the substrate occurs during film preparation. Moreover, it is shown that oxygen contamination may produce precipitation phenomena inside the film.

This paper presents angle-resolved photoemission spectroscopy data of the core lines of a heavily implanted and laser-annealed Si(100) surface. For the first time unambiguous data show that the laser-annealing process induces an almost complete reconstruction of the inner-layer electronic structure, whereas the outermost layers preserve the behavior of the ion-implanted surface. Ab initio electronic structure calculations performed on a ${\mathrm{Si}}_{\mathrm{n}}$${\mathrm{H}}_{3\mathrm{n}\mathrm{\ensuremath{-}}3}$ cluster strongly indicate that the modifications observed are due to the loss of coordination of the Si atoms, which is recovered after laser annealing only in the inner layers.

We studied, by means of spectroscopic ellipsometry, dilute magnetic Cd1−xMnxTe∕CdTe semiconductor superlattices and Cd1−xMnxTe thin films grown by molecular beam epitaxy. In superlattices, the pseudodielectric function measured by ellipsometry shows specific features related to the excitonic transition between quantized minibands. In thin films, ellipsometry allows the clear identification of the energy gap. Additionally, critical point transitions are observable both in the spectra of the superlattices and films. Photoluminescence experiments have also been measured in order to evidence the fundamental interminiband excitonic transitions in superlattices and the energy gap in thin films, respectively. The electronic structure of the superlattices has been calculated in the framework of the envelope function approximation and compared with the experimental spectra. Ellipsometry appears to be a suitable technique to monitor the molecular beam epitaxy growth, ultimately also in situ, of dilute magnetic low-...

We studied the optical properties of Cd1−xMnxTe∕Cd1−yMnyTe 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 Cd1−xMnxTe∕Cd1−yMnyTe superlattices that can find specific applications in spintronic devices.