F. Beltram

Publications (77)125.84 Total impact

• Article: Nanowire-based field effect transistors for terahertz detection and imaging systems.

  L Romeo, D Coquillat, M Pea, D Ercolani, F Beltram, L Sorba, W Knap, A Tredicucci, M S Vitiello
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  ABSTRACT: The development of self-assembled nanostructure technologies has recently opened the way towards a wide class of semiconductor integrated devices, with progressively optimized performances and the potential for a widespread range of electronic and photonic applications. Here we report on the development of field effect transistors (FETs) based on semiconductor nanowires (NWs) as highly-sensitive room-temperature plasma-wave broadband terahertz (THz) detectors. The electromagnetic radiation at 0.3 THz is funneled onto a broadband bow-tie antenna, whose lobes are connected to the source and gate FET electrodes. The oscillating electric field experienced by the channel electrons, combined with the charge density modulation by the gate electrode, results in a source-drain signal rectification, which can be read as a DC signal output. We investigated the influence of Se-doping concentration of InAs NWs on the detection performances, reaching responsivity values higher than 100 V W(-1), with noise-equivalent-power of ∼10(-9) W Hz(-1/2). Transmission imaging experiments at 0.3 THz show the good reliability and sensitivity of the devices in a real practical application.
  Nanotechnology 05/2013; 24(21):214005. · 3.98 Impact Factor
• Source

  Available from: Mauro Gemmi

  Article: Suppression of lateral growth in InAs/InAsSb heterostructured nanowires

  M Pea, D Ercolani, A Li, M Gemmi, F Rossi, F Beltram, L Sorba, J M Redwing
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  ABSTRACT: a b s t r a c t It is well known that a significant lateral growth is observed in the InAsSb sections of InAs/InAsSb heterostructured nanowires (NWs) with intermediate Sb content that prevents the independent control of NW diameter and length. Here we demonstrate that this lateral growth can be suppressed by increasing the growth temperature of the InAsSb segment and by reducing the InAs stem length. Optimized InAsSb sections show good structural and electrical properties. The mechanism driving this reduced lateral growth and its relevance toward the synthesis of highly controlled InAs/InAsSb heterostructured NWs are discussed. & 2013 Elsevier B.V. All rights reserved.
  Journal of Crystal Growth 02/2013; 366:8-14. · 1.73 Impact Factor
• Article: Quantum transport in low-dimensional AlGaN/GaN systems

  D Spirito, G Frucci, A Di Gaspare, L Di Gaspare, E Giovine, A Notargiacomo, S Roddaro, F Beltram, F Evangelisti
  Journal of Nanoparticle Research 11/2011; 13(11, SI):5699-5704. · 3.29 Impact Factor
• Source

  Available from: Francesco Giazotto

  Article: Quantum dot spectroscopy of proximity-induced superconductivity in a two-dimensional electron gas

  F. Deon, V. Pellegrini, F. Giazotto, G. Biasiol, L. Sorba, F. Beltram
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  ABSTRACT: We report the realization of a hybrid superconductor-quantum dot device by means of top-down nanofabrication starting from a two-dimensional electron gas in a InGaAs/InAlAs semiconductor heterostructure. The quantum dot is defined by electrostatic gates placed within the normal region of a planar Nb–InGaAs quantum well-Nb junction. Measurements in the regime of strong Coulomb blockade as well as cotunneling spectroscopy allow to directly probe the proximity-induced energy gap in a ballistic two-dimensional electron gas coupled to superconductors.
  Applied Physics Letters 03/2011; 98(13):132101-132101-3. · 3.84 Impact Factor
• Source

  Available from: ArXiv

  Article: Hybrid InAs nanowire-vanadium proximity SQUID.

  P Spathis, S Biswas, S Roddaro, L Sorba, F Giazotto, F Beltram
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  ABSTRACT: We report the fabrication and characterization of superconducting quantum interference devices (SQUIDs) based on InAs nanowires and vanadium superconducting electrodes. These mesoscopic devices are found to be extremely robust against thermal cycling and to operate up to temperatures of ∼ 2.5 K with reduced power dissipation. We show that our geometry allows one to obtain nearly-symmetric devices with very large magnetic field modulation of the critical current. All these properties make these devices attractive for sensitive magnetometry applications and quantum circuit implementation.
  Nanotechnology 03/2011; 22(10):105201. · 3.98 Impact Factor
• Article: Magnetotransport investigation of conducting channels and spin splitting in high-density AlGaN/AlN/GaN two-dimensional electron gas

  D Spirito, L Di Gaspare, G Frucci, F Evangelisti, A Di Gaspare, A Notargiacomo, E Giovine, S Roddaro, F Beltram
  Physical Review B 01/2011; 83(15). · 3.69 Impact Factor
• Source

  Available from: Francesco Giazotto

  Article: Cooling electrons from 1 K to 400 mK with V-based nanorefrigerators

  O. Quaranta, P. Spathis, F. Beltram, F. Giazotto
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  ABSTRACT: The fabrication and operation of V-based superconducting nanorefrigerators is reported. Specifically, electrons in an Al island are cooled thanks to hot-quasiparticle extraction provided by tunnel-coupled V electrodes. Electronic temperature reduction down to 400 mK starting from 1 K is demonstrated with a cooling power ~20 pW at 1 K for a junction area of 0.3 micron^2. The present architecture extends to higher temperatures refrigeration based on tunneling between superconductors and paves the way to the implementation of a multi-stage on-chip cooling scheme operating from above 1 K down to the mK regime.
  11/2010;
• Article: Pd-Assisted Growth of InAs Nanowires

  S. Heun, B. Radha, D. Ercolani, G. U. Kulkarni, F. Rossi, V. Grillo, G. Salviati, F. Beltram, L. Sorba
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  ABSTRACT: We report the Pd-assisted chemical beam epitaxy growth of zinc blende InAs nanowires which are grown on InAs(111)A substrates by employing Pd octane and hexadecyl thiolates as catalyst precursors. The structural properties of these nanowires are investigated by scanning and transmission electron microscopy. Furthermore, we demostrate the growth of InAs nanowires on patterned substrates by employing the Pd hexadecylthiolate precursors as a direct-write resist in electron beam lithography.
  08/2010;
• Source

  Available from: ArXiv

  Article: Delocalized-localized transition in a semiconductor two-dimensional honeycomb lattice

  G. De Simoni, A. Singha, M. Gibertini, B. Karmakar, M. Polini, V. Piazza, L. N. Pfeiffer, K. W. West, F. Beltram, V. Pellegrini
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  ABSTRACT: We report the magneto-transport properties of a two-dimensional electron gas in a modulation-doped AlGaAs/GaAs heterostructure subjected to a lateral potential with honeycomb geometry. Periodic oscillations of the magneto-resistance and a delocalized-localized transition are shown by applying a gate voltage. We argue that electrons in such artificial-graphene lattices offer a promising approach for the simulation of quantum phases dictated by Coulomb interactions.
  07/2010;
• Source

  Available from: V. Giovannetti

  Article: Coherent detection of electron dephasing.

  E Strambini, L Chirolli, V Giovannetti, F Taddei, R Fazio, V Piazza, F Beltram
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  ABSTRACT: We show that an Aharonov-Bohm ring with asymmetric electron injection can act as a coherent detector of electron dephasing. The presence of a dephasing source in one of the two arms of a moderately-to-highly asymmetric ring changes the response of the system from total reflection to complete transmission while preserving the coherence of the electrons propagating from the ring, even for strong dephasing. We interpret this phenomenon as an implementation of an interaction-free measurement.
  Physical Review Letters 04/2010; 104(17):170403. · 7.37 Impact Factor
• Source

  Available from: Giorgio Biasiol

  Article: Cantilever deflection measurement and actuation by an interdigitated transducer

  E. Strambini, V. Piazza, P. Pingue, G. Biasiol, L. Sorba, F. Beltram
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  ABSTRACT: A scheme that allows all-electrical high-bandwidth readout of a cantilever deflection by means of an integrated interdigitated transducer is presented. The present approach takes advantage of the piezoelectricity of the chosen cantilever substrate material to generate and detect surface-acoustic-waves by means of an interdigitated transducer (IDT) and to determine cantilever deflections. We shall also show that the same IDT can be used to excite the oscillation modes of the lever. Our scheme is compatible with implementations exploiting wireless excitation and readout and in mass sensing applications.
  Applied Physics Letters 04/2010; 96(17):173505-173505-3. · 3.84 Impact Factor
• Source

  Available from: V. Giovannetti

  Article: Electronic implementations of Interaction-Free Measurements

  L. Chirolli, E. Strambini, V. Giovannetti, F. Taddei, V. Piazza, R. Fazio, F. Beltram, G. Burkard
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  ABSTRACT: Three different implementations of interaction-free measurements (IFMs) in solid-state nanodevices are discussed. The first one is based on a series of concatenated Mach-Zehnder interferometers, in analogy to optical-IFM setups. The second one consists of a single interferometer and concatenation is achieved in the time domain making use of a quantized electron emitter. The third implementation consists of an asymmetric Aharonov-Bohm ring. For all three cases we show that the presence of a dephasing source acting on one arm of the interferometer can be detected without degrading the coherence of the measured current. Electronic implementations of IFMs in nanoelectronics may play a fundamental role as very accurate and noninvasive measuring schemes for quantum devices. Comment: 12 pages, 10 figures
  04/2010;
• Source

  Available from: Francesco Giazotto

  Article: InAs nanowire hot-electron Josephson transistor

  S. Roddaro, A. Pescaglini, D. Ercolani, L. Sorba, F. Giazotto, F. Beltram
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  ABSTRACT: At a superconductor (S)-normal metal (N) junction pairing correlations can "leak-out" into the N region. This proximity effect [1, 2] modifies the system transport properties and can lead to supercurrent flow in SNS junctions [3]. Recent experimental works showed the potential of semiconductor nanowires (NWs) as building blocks for nanometre-scale devices [4-7], also in combination with superconducting elements [8-12]. Here, we demonstrate an InAs NW Josephson transistor where supercurrent is controlled by hot-quasiparticle injection from normal-metal electrodes. Operational principle is based on the modification of NW electron-energy distribution [13-20] that can yield reduced dissipation and high-switching speed. We shall argue that exploitation of this principle with heterostructured semiconductor NWs opens the way to a host of out-of-equilibrium hybrid-nanodevice concepts [7, 21].
  03/2010;
• Source

  Available from: F. Carillo

  Article: Singlet-triplet transition in a few-electron lateral InGaAs-InAlAs quantum dot

  F. Deon, V. Pellegrini, F. Carillo, F. Giazotto, L. Sorba, G. Biasiol, F. Beltram
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  ABSTRACT: The magnetic-field evolution of Coulomb blockade peaks in lateral InGaAs/InAlAs quantum dots in the few-electron regime is reported. Quantum dots are defined by gates evaporated onto a 60 nm-thick hydrogen silsesquioxane insulating film. A gyromagnetic factor of 4.4 is measured via zero-bias spin spectroscopy and a transition from singlet to triplet spin configuration is found at an in-plane magnetic field B = 0.7 T. This observation opens the way to the manipulation of singlet and triplet states at moderate fields and its relevance for quantum information applications will be discussed. Comment: 4 pages, 3 figures
  02/2010;
• Article: Electronic properties of quantum dot systems realized in semiconductor nanowires

  J Salfi, S Roddaro, D Ercolani, L Sorba, I Savelyev, M Blumin, H E Ruda, F Beltram
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  ABSTRACT: Catalyst-assisted growth of semiconductor nanowires has opened up several new and exciting possibilities for low-dimensional semiconductor structures. The authors review progress on the realization of quantum dots in semiconductor nanowires, and their characterization by transport spectroscopy. Emphasis is placed on the wide range electronic properties exhibited due to flexibility of the growth process in terms of nanostructure composition and size. Particular attention is placed on studies of spin in few-electron quantum dots.
  Semiconductor Science and Technology 01/2010; 25(2):024007. · 1.72 Impact Factor
• Article: Singlet-triplet transition in a few-electron lateral In0.75 Ga0.25 As/ In0.75 Al0.25 As quantum dot

  F Deon, V Pellegrini, F Carillo, F Giazotto, G Biasiol, L Sorba, F Beltram
  Applied Physics Letters 01/2010; 96(14). · 3.84 Impact Factor
• Article: Conductance and valley splitting in etched Si/SiGe one-dimensional nanostructures

  G Frucci, L Di Gaspare, F Evangelisti, E Giovine, A Notargiacomo, V Piazza, F Beltram
  Physical Review B 01/2010; 81(19). · 3.69 Impact Factor
• Article: Quasi-periodic distributed feedback laser

  L.~Mahler, A.~Tredicucci, F.~Beltram, C.~Walther, J.~Faist, H.~E.~Beere, D.~A.~Ritchie, D.~S.~Wiersma
  Nature Photonics. 01/2010; 4:165-169.
• Article: Differential near-field scanning optical microscopy with THz quantum cascade laser sources.

  R Degl'Innocenti, M Montinaro, J Xu, V Piazza, P Pingue, A Tredicucci, F Beltram, H E Beere, D A Ritchie
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  ABSTRACT: We have realized a differential Near-field Scanning Optical Microscope (NSOM) working with subwavelength resolution in the THz spectral region. The system employs a quantum cascade laser emitting at lambda approximately 105 microm as source, and the method, differently from conventional NSOM, involves diffracting apertures with size comparable to the wavelength. This concept ensures a higher signal-to-noise level at the expense of an additional computational step. In the implementation here reported lambda/10 resolution has been achieved; present limiting factors are investigated through finite difference time domain simulations.
  Optics Express 12/2009; 17(26):23785-92. · 3.59 Impact Factor
• Article: Directional PC12 Cell Migration Along Plastic Nanotracks

  A. Ferrari, M. Cecchini, R. Degl'Innocenti, F. Beltram
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  ABSTRACT: The design of materials to promote the development and/or regeneration of neuronal tissue requires the understanding of the mechanisms by which the underlying substrate topography can modulate neuronal cell differentiation and migration. We recently demonstrated that plastic nanogratings (alternating lines of grooves and ridges of submicrometer size) can effectively change the neuronal polarity state, selecting bipolar cells with aligned neurites. Here, we address the effect of nanogratings on the migration properties of differentiating PC12 cells and correlate their behavior with the polarity state induced by the substrate. During neuronal differentiation, cell-substrate interaction is sufficient to induce directional migration along the nanogratings. Control cells contacting flat substrates migrated freely in all directions, while cells differentiating on nanogratings showed slower migration characterized by an angular restriction that confined cell movements. Finally, we show that directional migration on nanogratings is linked to a specific organization of the cell cytoskeleton reflecting the nanograting directionality.
  IEEE Transactions on Biomedical Engineering 12/2009; · 2.28 Impact Factor