CNR Institute for Microelectronics and Microsystems

Agrate Brianza, Italy

CNR Institute for Microelectronics and Microsystems

Agrate Brianza, Italy
SEARCH FILTERS
Time filter
Source Type

Prokopidis K.P.,Aristotle University of Thessaloniki | Zografopoulos D.C.,CNR Institute for Microelectronics and Microsystems
Journal of Lightwave Technology | Year: 2013

A generalized auxiliary differential equation (ADE) finite-difference time-domain (FDTD) dispersive scheme is introduced for the rigorous simulation of wave propagation in metallic structures at optical frequencies, where material dispersion is described via an arbitrary number of Drude and critical point terms. The implementation of an efficient perfectly matched layer for the termination of such media is also discussed and demonstrated. The model's validity is directly compared with both analytical and numerical results that employ known dispersion schemes, for the case of two benchmark examples, transmission through a thin metal film and scattering from a metallic nanocylinder. Furthermore, the accuracy of the proposed method is also demonstrated in the study of the optical properties of Ag and Au metal-insulator-metal waveguides, filters, and resonators, which also involve dielectrics whose material dispersion is described by the Sellmeier model. © 2013 IEEE.


Tao L.,University of Texas at Austin | Cinquanta E.,CNR Institute for Microelectronics and Microsystems | Chiappe D.,CNR Institute for Microelectronics and Microsystems | Grazianetti C.,CNR Institute for Microelectronics and Microsystems | And 4 more authors.
Nature Nanotechnology | Year: 2015

Free-standing silicene, a silicon analogue of graphene, has a buckled honeycomb lattice and, because of its Dirac bandstructure combined with its sensitive surface, offers the potential for a widely tunable two-dimensional monolayer, where external fields and interface interactions can be exploited to influence fundamental properties such as bandgap and band character for future nanoelectronic devices. The quantum spin Hall effect, chiral superconductivity, giant magnetoresistance and various exotic field-dependent states have been predicted in monolayer silicene. Despite recent progress regarding the epitaxial synthesis of silicene and investigation of its electronic properties, to date there has been no report of experimental silicene devices because of its air stability issue. Here, we report a silicene field-effect transistor, corroborating theoretical expectations regarding its ambipolar Dirac charge transport, with a measured room-temperature mobility of ∼100 cm2 V-1 s-1 attributed to acoustic phonon-limited transport and grain boundary scattering. These results are enabled by a growth-transfer-fabrication process that we have devised - silicene encapsulated delamination with native electrodes. This approach addresses a major challenge for material preservation of silicene during transfer and device fabrication and is applicable to other air-sensitive two-dimensional materials such as germanene and phosphorene. Silicene's allotropic affinity with bulk silicon and its low-temperature synthesis compared with graphene or alternative two-dimensional semiconductors suggest a more direct integration with ubiquitous semiconductor technology. © 2015 Macmillan Publishers Limited. All rights reserved.


Zografopoulos D.C.,CNR Institute for Microelectronics and Microsystems | Beccherelli R.,CNR Institute for Microelectronics and Microsystems
Applied Physics Letters | Year: 2013

An optical switch based on liquid-crystal (LC) tunable long-range metal stripe waveguides is proposed and theoretically investigated. A nematic liquid crystal layer placed between a vertical configuration consisting of two gold stripes is shown to allow for the extensive electro-optic tuning of the couplers waveguiding characteristics. Rigorous liquid-crystal switching studies are coupled with the investigation of the optical properties of the proposed plasmonic structure, taking into account different excitation conditions and the impact of LC-scattering losses. A directional coupler optical switch is demonstrated, which combines low power consumption, low cross-talk, short coupling lengths, along with sufficiently reduced insertion losses. © 2013 American Institute of Physics.


Zografopoulos D.C.,CNR Institute for Microelectronics and Microsystems | Beccherelli R.,CNR Institute for Microelectronics and Microsystems
Plasmonics | Year: 2013

A long-range surface plasmon polariton variable optical attenuator based on available nematic liquid crystals and polymers is proposed and theoretically investigated. It is demonstrated that the electro-optic control of the nematic molecular orientation is capable of tuning the level of index asymmetry of an Au stripe waveguide and the key properties of the fundamental long-range plasmonic mode, such as modal profile and propagation losses. By proper structural design and material selection, plasmonic in-line intensity modulators are designed, which exhibit very low power consumption, extinction ratios in excess of 30 dB, and insertion losses as low as 1 dB for a device length in the millimeter range. Such active plasmonic elements are envisaged to be used in interchip photonics bus interconnects. © 2012 Springer Science+Business Media, LLC.


Di Lorenzo A.,Federal University of Uberlandia | Di Lorenzo A.,CNR Institute for Microelectronics and Microsystems
Annals of Physics | Year: 2014

In a weak measurement, the average output 〈o 〉 of a probe that measures an observable  of a quantum system undergoing both a preparation in a state ρi and a postselection in a state Ef is, to a good approximation, a function of the weak value Aw=Tr[EfÂρi]/Tr[Efρi], a complex number. For a fixed coupling λ, when the overlap Tr [Efρi] is very small, Aw diverges, but 〈o 〉 stays finite, often tending to zero for symmetry reasons. This paper answers the questions: what is the weak value that maximizes the output for a fixed coupling? What is the coupling that maximizes the output for a fixed weak value? We derive equations for the optimal values of Aw and λ, and provide the solutions. The results are independent of the dimensionality of the system, and they apply to a probe having a Hilbert space of arbitrary dimension. Using the Schrödinger-Robertson uncertainty relation, we demonstrate that, in an important case, the amplification 〈o 〉 cannot exceed the initial uncertainty σo in the observable ô, we provide an upper limit for the more general case, and a strategy to obtain 〈o 〉 ≫ σo. © 2014 Elsevier Inc.


Zografopoulos D.C.,CNR Institute for Microelectronics and Microsystems | Beccherelli R.,CNR Institute for Microelectronics and Microsystems
Optics Express | Year: 2013

A liquid-crystal tunable plasmonic optical switch based on a long-range metal stripe directional coupler is proposed and theoretically investigated. Extensive electro-optic tuning of the coupler's characteristics is demonstrated by introducing a nematic liquid crystal layer above two coplanar plasmonic waveguides. The switching properties of the proposed plasmonic structure are investigated through rigorous liquid-crystal studies coupled with a finite-element based analysis of light propagation. A directional coupler optical switch is demonstrated, which combines very low power consumption, low operation voltages, adjustable crosstalk and coupling lengths, along with sufficiently reduced insertion losses. © 2013 Optical Society of America.


Debernardi A.,CNR Institute for Microelectronics and Microsystems
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

I present an ab initio study of the phase stability and dielectric constant (κ 0) of Hf 1-xGe xO 2 alloy as a function of Ge concentration in the range 0≤x≤0.25. I determine the critical concentration x c at which the monoclinic structure (the stable phase at low x and at low temperatures) has a phase transition into the high-κ 0 fluorite structure. I found that, at x c, the fluorite phase presents a dielectric constant that is more than 50% higher than the orientationally averaged dielectric constant of undoped bulk monoclinic phase. I studied the effect of temperature on this phase transition. I identified the microscopic mechanisms which influence the dielectric properties of the fluorite phase finding that the decrease of the Born effective charge of Ge with respect to that of Hf is locally compensated by a variation of the Born effective charge of the O atoms which are neighbors of the Ge. I predict that the bulk modulus of this superhard oxide increases as a function of doping. My results are relevant to improve, by Ge alloying, the dielectric and mechanical properties of hafnia in advanced technological applications. © 2012 American Physical Society.


Camarda M.,CNR Institute for Microelectronics and Microsystems
Surface Science | Year: 2012

In this article we use three dimensional kinetic Monte Carlo simulations on super-lattices to study the hetero-polytypical growth of cubic silicon carbide polytype (3C-SiC) on misoriented hexagonal (4H and 6H) substrates. We analyze the quality of the 3C-SiC film varying the polytype, the miscut angle and the initial surface morphology of the substrate. We find that the use of 6H misoriented (4°-10°off) substrates, with step bunched surfaces, can strongly improve the quality of the cubic epitaxial film whereas the 3C/4H growth is affected by the generation of dislocations, due to the incommensurable periodicity of the 3C (3) and the 4H (4) polytypes. For these reasons, a proper pre-growth treatment of 6H misoriented substrates can be the key for the growth of high quality, twin free, 3C-SiC films. © 2012 Elsevier B.V. All rights reserved.


Priolo F.,University of Catania | Priolo F.,CNR Institute for Microelectronics and Microsystems | Gregorkiewicz T.,University of Amsterdam | Galli M.,University of Pavia | Krauss T.F.,University of York
Nature Nanotechnology | Year: 2014

Silicon has long been established as the material of choice for the microelectronics industry. This is not yet true in photonics, where the limited degrees of freedom in material design combined with the indirect bandgap are a major constraint. Recent developments, especially those enabled by nanoscale engineering of the electronic and photonic properties, are starting to change the picture, and some silicon nanostructures now approach or even exceed the performance of equivalent direct-bandgap materials. Focusing on two application areas, namely communications and photovoltaics, we review recent progress in silicon nanocrystals, nanowires and photonic crystals as key examples of functional nanostructures. We assess the state of the art in each field and highlight the challenges that need to be overcome to make silicon a truly high-performing photonic material. © 2014 Macmillan Publishers Limited.


Deretzis I.,CNR Institute for Microelectronics and Microsystems | La Magna A.,CNR Institute for Microelectronics and Microsystems
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We present an orbital-resolved density functional theory study on the electronic properties of hydrogen and lithium intercalated graphene grown on the Si face of SiC. Starting from the (6√3×6√3)R30 surface reconstruction of the graphene/SiC heterosystem, we find that both H and Li can restore the ideal structural characteristics of the two nonequivalent junction parts (i.e., graphene and the SiC substrate) when inserted at the interface. However, the chemical and electrostatic interactions remain different for the two cases. Hence, H-intercalated epitaxial graphene is subject to a sublattice symmetry-breaking electronic interference that perturbs the Dirac point, whereas Li intercalation gives rise to a highly n-doped system due to a nonuniform delocalization of Li charges. Results bring to discussion the role of substrate engineering in epitaxial graphene on SiC. © 2011 American Physical Society.

Loading CNR Institute for Microelectronics and Microsystems collaborators
Loading CNR Institute for Microelectronics and Microsystems collaborators