Stefano Ossicini

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Silicon photonics meets the electronics requirement of increased speed and bandwidth with on-chip optical networks. All-optical data management requires nonlinear silicon photonics. In silicon only third-order optical nonlinearities are present owing to its crystalline inversion symmetry. Introducing a second-order nonlinearity into silicon photonics by(More)
Silicon nanocrystals (Si-nc) embedded in SiO2 matrix have been prepared by high temperature thermal annealing (1000-1250 degrees C) of substoichiometric SiOx films deposited by plasma-enhanced chemical vapor deposition (PECVD). Different techniques have been used to examine the optical and structural properties of Si-nc. Transmission electron microscopy(More)
Basic Principles to Advanced Applications Michele Amato,*,† Maurizia Palummo,*,‡ Riccardo Rurali,* and Stefano Ossicini* †Institut d’Electronique Fondamentale, UMR8622, CNRS, Universite ́ Paris-Sud, 91405 Orsay, France ‡European Theoretical Spectroscopy Facility (ETSF), Dipartimento di Fisica, Universita ̀ di Roma, “Tor Vergata”, Via della Ricerca(More)
Impurity doping of semiconducting nanowires has been predicted to become increasingly inefficient as the wire diameter is reduced, because impurity states get deeper due to quantum and dielectric confinement. We show that efficient n- and p-type doping can be achieved in SiGe core-shell nanowires as thin as 2 nm, taking advantage of the band offset at the(More)
In this work we aim at understanding the effect of n- and p-type substitutional doping in the case of matrix-embedded and freestanding Si nanocrystals. By means of ab initio calculations we identify the preferential positioning of the dopants and its effect on the structural properties with respect to the undoped case. Subsequently, we consider the case of(More)
Actually, most of the electric energy is being produced by fossil fuels and great is the search for viable alternatives. The most appealing and promising technology is photovoltaics. It will become truly mainstream when its cost will be comparable to other energy sources. One way is to significantly enhance device efficiencies, for example by increasing the(More)
We present density functional theory calculations of carrier multiplication properties in a system of strongly coupled silicon nanocrystals. Our results suggest that nanocrystal-nanocrystal interaction can lead to a reduction of the carrier multiplication energy threshold without altering the carrier multiplication efficiency at high energies, in agreement(More)
Actually, most of the electric energy is being produced by fossil fuels and great is the search for viable alternatives. The most appealing and promising technology is photovoltaics. It will become truly mainstream when its cost will be comparable to other energy sources. One way is to significantly enhance device efficiencies, for example by increasing the(More)
We show that the electronic and optical properties of silicon nanowires, with different size and orientation, are dominated by important many-body effects. The electronic and excitonic gaps, calculated within first principles, agree with the available experimental data. Huge excitonic effects, which depend strongly on wire orientation and size, characterize(More)
Starting from experimental findings and interface growth problems in Si/Ge superlattices, we have investigated through ab initio methods the concurrent and competitive behavior of strain and defects in the second-harmonic generation process. Interpreting the second-harmonic intensities as a function of the different nature and percentage of defects together(More)