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  • 1.
    Abadei, S
    et al.
    Chalmers University of Technology.
    Gevorgian, S
    Chalmers University of Technology.
    Cho, C.-R
    Royal Institute of Technology.
    Grishin, A.
    Royal Institute of Technology.
    Andreasson, Johanna
    Lindbäck, Ture
    DC field dependent properties of Na0.5K0.5NbO₃/SiO₂/Si structures at millimeter-wave frequencies2001In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 78, no 13, p. 1900-1902Article in journal (Refereed)
    Abstract [en]

    Dielectric properties of laser-ablated 0.5-μm-thick c-axis epitaxial Na0.5K0.5NbO3 films on high-resistivity (7.7 Ω cm) silicon SiO2/Si substrate are studied experimentally at frequencies up to 40 GHz. For measurements, planar 0.5-μm-thick gold electrodes (interdigital and straight slot) are photolithography defined on the top surface of Na0.5K0.5NbO3 films. The slot width between the electrodes is 2 or 4 μm. 13% capacitance change at 40 V dc bias and Q factor more than 15 are observed at 40 GHz, which makes the structure useful for applications in electrically tunable millimeter-wave devices

  • 2. Baricordi, S.
    et al.
    Biryukov, V. M.
    Institute for High Energy Physics.
    Carnera, A.
    Chesnokov, Yu A.
    Institute for High Energy Physics.
    Mea, G. Della
    University of Trento, Department of Materials Engineering and Industrial Technologies.
    Guidi, V.
    Ivanov, Yu M.
    Petersburg Institute for Nuclear Physics.
    Martinelli, G.
    Milan, E.
    Restello, S.
    INFN.
    Sambo, A.
    Scandale, W.
    CERN.
    Vomiero, Alberto
    Department of Physics, University of Padova.
    Low-energy-channeling surface analysis on silicon crystals designed for high-energy-channeling in accelerators2005In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 87, no 9, article id 94102Article in journal (Refereed)
    Abstract [en]

    Channeling of relativistic particles in bent Si crystals is a powerful technique for use with accelerators. Its efficiency can be found to be highly dependent on the state of the surface of the crystal steering the particles. We investigated the morphology and structure of the surface of the samples that have been used with high efficiency for channeling in accelerators. Low-energy channeling of 2 MeVα particles or protons was used as a probe. We found that mechanical treatment of the samples leads to a superficial damaged layer, which is correlated to efficiency limitations of the crystal in accelerators. In contrast, chemical etching, which was used to treat the surface of the most efficient crystals, leaves a surface with superior perfection. © 2005 American Institute of Physics.

  • 3.
    Baricordi, S.
    et al.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Guidi, V.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Mazzolari, A.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Martinelli, G.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Carnera, A.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Salvador, D. De
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Sambo, A.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Mea, G. Della
    Dipartimento di Ingegneria dei Materiali, Università di Trento.
    Milan, R.
    INFN Laboratori Nazionali di Legnaro.
    Vomiero, Alberto
    INFM-CNR Sensor Lab.
    Scandale, W.
    European Organization for Nuclear Research.
    Optimal crystal surface for efficient channeling in the new generation of hadron machines2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, no 6, article id 61908Article in journal (Refereed)
    Abstract [en]

    The new generation of hadron machines may profitably take advantage of channeling for steering and collimation of high-energy particle beams. In that case, the requirements on the quality of the crystal surface are rather stringent in terms of both lattice perfection and roughness. Here, the authors show the structural and morphological characterizations of crystals fabricated through a method to achieve a surface that fulfills all needed specifications for application in hadron machines. © 2007 American Institute of Physics.

  • 4.
    Blomqvist, Mats
    et al.
    Department of Condensed Matter Physics, Royal Institute of Technology.
    Koh, Jung-Hyuk
    Department of Condensed Matter Physics, Royal Institute of Technology.
    Grishin, Alex
    Department of Condensed Matter Physics, Royal Institute of Technology.
    Andreasson, Johanna
    High-performance epitaxial Na0.5K0.5NbO3 thin films by magnetron sputtering2002In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 81, no 2, p. 337-Article in journal (Refereed)
  • 5.
    Chen, Yao
    et al.
    Chinese Academy of Sciences, Beijing.
    Gan, Cuihua
    Chinese Academy of Sciences, Beijing.
    Zhang, Tainua
    Chinese Academy of Sciences, Beijing.
    Yu, Gang
    Chinese Academy of Sciences, Beijing.
    Bai, Pucun
    Chinese Academy of Sciences, Beijing.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Laser-surface-alloyed carbon nanotubes reinforced hydroxyapatite composite coatings2005In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 86, no 25, p. 251905-251907Article in journal (Refereed)
    Abstract [en]

    Carbon-nanotube (CNT)-reinforced hydroxyapatite composite coatings have been fabricated by laser surface alloying. Microstructural observation using high-resolution transmission electron microscopy showed that a large amount of CNTs remained with their original tubular morphology, even though some CNTs reacted with titanium element in the substrate during laser irradiation. Additionally, measurements on the elastic modulus and hardness of the composite coatings indicated that the mechanical properties were affected by the amount of CNTs in the starting precursor materials. Therefore, CNT-reinforced hydroxyapatite composite is a promising coating material for high-load-bearing metal implants

  • 6.
    Chernogorova, Olga
    et al.
    A.A. Baikov Institute of Metallurgy and Materials Science (IMET), Moscow.
    Potapova, Iraida
    A.A. Baikov Institute of Metallurgy and Materials Science (IMET), Moscow.
    Drozdova, Ekaterina
    A.A. Baikov Institute of Metallurgy and Materials Science (IMET), Moscow.
    Sirotinkin, Vladimir
    A.A. Baikov Institute of Metallurgy and Materials Science (IMET), Moscow.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Vasiliev, Alexander
    National Research Center, Kurchatov Instiute, Moscow.
    Ekimov, Evgeny
    RAS, Vereshchagin Institute of High Pressure Physics, Troitsk, Moscow.
    Structure and physical properties of nanoclustered graphene synthesized from C-60 fullerene under high pressure and high temperature2014In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 104, no 4, article id 43110Article in journal (Refereed)
    Abstract [en]

    C-60 treatment at 5-8 GPa, similar to 1000 degrees C results in the fullerene cage collapse and transformation to a phase with outstanding mechanical properties. A detailed structural analysis of the phase reveals that it comprised 7-12 layer graphene clusters with lateral dimension of 2-4 nm. Raman spectra of the nanoclustered graphene phase are similar to those of disordered sp(2) carbon structure with an admixture of sp(3)-bonded carbon. The phase is characterized by a high (up to 19 GPa) hardness, relatively low (about 70 GPa) Young modulus and up to 95% elastic recovery, determining excellent wear resistance and good antifriction properties. (C) 2014 AIP Publishing LLC.

  • 7.
    Coutinho, J.
    et al.
    Department of Physics, University of Aveiro.
    Jones, R.
    School of Physics, University of Exeter.
    Shaw, M.
    School of Natural Science, University of Newcastle upon Tyne.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Optically active erbium-oxygen complexes in GaAs2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 84, no 10, p. 1683-1685Article in journal (Refereed)
    Abstract [en]

    Density functional modeling of Er and Er-O complexes in GaAs show that Er impurities at the Ga site are not efficient channels for exciton recombination, but decorative O atoms play crucial roles in inhibiting Er precipitation and in creating the necessary conditions for electron-hole capture. Among the defects studied, the ErGaOAs and ErGa(OAs)2 models have the symmetry and carrier trap location close to the defect responsible for the strong 1.54 µm photoluminescence band in Er, O codoped GaAs.

  • 8.
    Coutinho, J.
    et al.
    Department of Physics, University of Aveiro, Campus Santiago.
    Torres, V.J.B.
    Department of Physics, University of Aveiro, Campus Santiago.
    Jones, R.
    School of Physics, University of Exeter.
    Carvalho, A.
    School of Physics, University of Exeter.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Briddon,, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Calculation of deep carrier traps in a divacancy in germanium crystals2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 88, no 9, p. 91919-Article in journal (Refereed)
    Abstract [en]

    We present an ab initio density functional study on the electronic structure and electrical properties of divacancies in Ge. Although suffering essentially different Jahn-Teller distortions when compared to the analogous defect in Si, the relative location of the electrical levels in the gap does not differ radically in both materials. We propose a V2 model that is responsible for a donor level at Ev+0.03 eV, a first acceptor state at Ev+0.3 eV, and a second acceptor level at Ec-0.4 eV. The latter is only 0.1 eV deeper than an electron trap that has been recently linked to a divacancy in proton implanted material.

  • 9.
    Eberlein, T.A.G.
    et al.
    School of Physics, University of Exeter.
    Blumenau, A.T.
    Max-Planck-Institut für Eisenforschung GmbH.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Briddon, P.R.
    Department of Physics, University of Newcastle.
    Jones, R.
    School of Physics, University of Exeter.
    Effect of charge on the movement of dislocations in SiC2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 88, no 8, p. 82113-Article in journal (Refereed)
    Abstract [en]

    SiC bipolar devices show a degradation under forward-biased operation which has been linked with a current induced motion of one of the two glide dislocations having either Si or C core atoms. We have carried out calculations of the core structures and dynamics of partial dislocations in 3C and 2H-SiC. In this work we present results on the effect of charge on the dislocation kinks. The calculations show that silicon kinks have a deep filled band above the valence band and the trapping of holes into this band permits motion at room temperature.

  • 10.
    Eberlein, T.A.G.
    et al.
    University of Exeter.
    Jones, R.
    University of Exeter.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Briddon, P.R.
    University of Newcastle Upon Tyne.
    Shallow acceptors in GaN2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, no 13, p. 132105-Article in journal (Refereed)
    Abstract [en]

    Recent high resolution photoluminescence studies of high quality Mg doped GaN show the presence of two acceptors. One is due to Mg and the other labeled A1 has a shallower acceptor defect. The authors investigate likely candidates for this shallow acceptor and conclude that CN is the most likely possibility. The authors also show that the CN is passivated by H and the passivated complex is more stable than MgGa-H

  • 11.
    Elsner, J.
    et al.
    Department of Physics, University of Exeter.
    Jones, R.
    Department of Physics, University of Exeter.
    Haugk, M.
    Technische Universität, Theoretische Physik III, D-09107 Chemnitz.
    Gutierrez, R.
    Technische Universität, Theoretische Physik III, D-09107 Chemnitz.
    Frauenheim, Th.
    Theoretische Physik III, TU Chemnitz.
    Heggie, M.I.
    CPES, University of Sussex, Falmer, Brighton.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Briddon, P.R.
    Department of Physics, University of Newcastle.
    Effect of oxygen on the growth of (101‾0) GaN surfaces: The formation of nanopipes1998In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 73, no 24, p. 3530-3532Article in journal (Refereed)
    Abstract [en]

    Local density-functional methods are used to examine the behavior of O and O-related defect complexes on the walls of nanopipes in GaN. We find that O has a tendency to segregate to the (10 1̄ 0) surface and identify the gallium vacancy surrounded by three oxygen impurities [VGa-(ON)3] to be a particularly stable and electrically inert complex. We suggest that during Stranski-Krastanow growth, when interisland spaces shrink, these defects reach a critical concentration beyond which further growth is prevented and nanopipes are formed

  • 12.
    Fujita, N.
    et al.
    Department Physik, Universität Paderborn.
    Jones, R.
    School of Physics, University of Exeter.
    Goss, J.P.
    School of Natural Science, University of Newcastle upon Tyne.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Frauenheim, T.
    Department Physik, Universität Paderborn.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Diffusion of nitrogen in silicon2005In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 87, no 2, p. 21902-Article in journal (Refereed)
    Abstract [en]

    We use local density functional theory to investigate the diffusion of nitrogen dimers in silicon. We investigate several trajectories for the diffusing dimer finding an alternative one whose barrier is 2.69 eV and in close agreement with experimental diffusion data carried out at high temperature. We suggest that recent reports of a low barrier of 1.45 eV found from studies of dislocation unlocking are to be understood from the interaction of nitrogen dimers with interstitials or vacancies released by the dislocation.

  • 13.
    Fujita, N.
    et al.
    School of Physics, University of Exeter.
    Jones, R.
    School of Physics, University of Exeter.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Nitrogen related shallow thermal donors in silicon2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, no 5, p. 51914-Article in journal (Refereed)
    Abstract [en]

    In this letter, the authors investigate the electrical properties of nitrogen related shallow thermal donor (STD) candidates and their concentrations under different doping conditions by means of density functional theory. Experimentally, the existence of STDs containing one nitrogen atom and both even and odd numbers of oxygen atoms has been proposed. However, so far first principles studies have not presented a candidate for the latter. Here, they show that the NO defect possesses a shallow donor level. Adding one or two more oxygen atoms results in the donor level to become shallower. The fraction of shallow nitrogen related donors to N dimers increases in material with low concentration of nitrogen.

  • 14.
    Goss, J.P.
    et al.
    School of Natural Science, University of Newcastle upon Tyne.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Eberlein, T.A.G.
    School of Physics, University of Exeter.
    Jones, R.
    School of Physics, University of Exeter.
    Pinho, N.
    School of Physics, University of Exeter.
    Blumenau, A.T.
    Theoretische Physik, Universität Paderborn.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Electrical and optical properties of rod-like defects in silicon2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 85, no 20, p. 4633-4635Article in journal (Refereed)
    Abstract [en]

    Self-interstitials in silicon can aggregate to form rod-like defects (RLDs) having both electrical and optical activity. We carry out local density functional calculations for both {113} and {111} RLDs to determine their structures and electrical activity. We find that small {113} RLDs are more stable than {111} RLDs but this reverses for larger defects. We attribute the electrical activity of {113} RLDs found in deep level transient spectroscopy studies with the bounding dislocations and the 0.903 eV photoluminescence to vacancy point defects lying on the habit plane.

  • 15.
    Janke, C.
    et al.
    School of Physics, University of Exeter.
    Jones, R.
    School of Physics, University of Exeter.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Ab initio studies of arsenic and boron related defects in silicon mesa diodes2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 90, no 15, p. 152103-Article in journal (Refereed)
    Abstract [en]

    E centers are known to diffuse around 400 K in Si and may then form larger donor-vacancy defects such as As2V in heavily doped n-type Si doped with As or AsBV if they diffuse into p-type regions. Ab initio methods are used to explore these possibilities. The AsV defect possesses electrical levels in agreement with experiments. The AsBV defect is found to exhibit a charge-dependent structure, has a barrier to dissociation of ~1.4 eV, and possesses an acceptor level at 0.27 or 0.47 eV above the valence band top depending on the defect structure. The As2V defect possesses only an acceptor level at 0.22 eV below the conduction band. Comparison is made with recent experiments carried out on mesa diodes.

  • 16.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Absorptivity modulation on wavy molten steel surfaces: the influence of laser wavelength and angle of incidence2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, no 15Article in journal (Refereed)
    Abstract [en]

    The modulation of the angle-dependent Fresnel absorptivity across wavy molten steel surfaces during laser materials processing, like drilling, cutting, or welding, has been calculated. The absorptivity is strongly altered by the grazing angle of incidence of the laser beam on the processing front. Owing to its specific Brewster-peak characteristics, the 10.64 μm wavelength CO 2-laser shows an opposite trend with respect to roughness and angle-of-incidence compared to lasers in the wavelength range of 532-1070 nm. Plateaus or rings of Brewster-peak absorptivity can lead to hot spots on a wavy surface, often in close proximity to cold spots caused by shadow domains.

  • 17. Kaplan, Alexander
    Surface processing with non-Gaussian beams1997In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 70, no 2, p. 264-266Article in journal (Refereed)
    Abstract [en]

    The heat transfer problem of a moving source of heat scanning over a semi-infinite solid is of considerable importance for surface processing with high energy beams. The analytical solution of a moving Gaussian beam is extended by superposition of several Gaussian beams in order to approximate real beam shapes, thus providing high flexibility and accuracy. By superimposing two concentric beams, a real intensity profile with a central minimum was approximated with an accuracy of 13% compared to 35% for the conventional Gaussian beam approach. For the corresponding temperature field, an error of 57% for the depth and 17% for the width of the melt pool was eliminated

  • 18.
    Maggioni, G.
    et al.
    INFM-CNR Sensor Lab.
    Vomiero, Alberto
    Dipartimento di Fisica, Universitá di Firenze and INFM, Unitá di Firenze.
    Carturan, S.
    INFM-CNR Sensor Lab.
    Scian, C.
    INFM-CNR Sensor Lab.
    Mattei, G.
    INFM-CNR Sensor Lab.
    Bazzan, M.
    INFM-CNR Sensor Lab.
    Fernández, C. De Julián
    INFM-CNR Sensor Lab.
    Mazzoldi, P.
    INFM-CNR Sensor Lab.
    Quaranta, A.
    Laboratori Nazionali di Legnaro.
    Mea, G. Della
    Laboratori Nazionali di Legnaro.
    Structure and optical properties of Au-polyimide nanocomposite films prepared by ion implantation2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 85, no 23, p. 5712-5714Article in journal (Refereed)
    Abstract [en]

    Au-polyimide nànocomposites have been synthesized by implanting different doses of Au+ ions in 100 nm thick films of pyromellitic dianhydride-4,4′ oxydianiline polyimide, prepared by glow discharge vapor deposition polymerization. Unambiguous evidence of Au nanoclusters growth is found only at the highest implantation doses (5 × 1016 Au + / cm2). Structural, compositional, and optical characterizations show that the implantation induces the compactation of the initial film due to H and C loss. The resulting structure is a composite containing 2-3 nm gold nanoparticles arranged in a layer of about 40 nm and, just beneath the sample surface, a 15 nm thick carbon-rich layer. Optical simulations suggest the presence of a gold-carbon core-shell structure in the nanoparticles. © 2004 American Institute of Physics.

  • 19.
    Mannelquist, Anders
    et al.
    Luleå tekniska universitet.
    Iwamoto, Hideki
    Department of Molecular Physiology and Biological Physics, Biophysics Graduate Program, University of Virginia School of Medicine.
    Szabo, Gabor
    Department of Molecular Physiology and Biological Physics, Biophysics Graduate Program, University of Virginia School of Medicine.
    Shao, Zhifeng
    Department of Molecular Physiology and Biological Physics, Biophysics Graduate Program, University of Virginia School of Medicine.
    Near-field optical microscopy with a vibrating probe in aqueous solution2001In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 78, no 14, p. 2076-2078Article in journal (Refereed)
    Abstract [en]

    We show that with an appropriately configured scanning quartz pipette coated with aluminum, a near-field scanning optical microscope (NSOM) can be constructed to operate in aqueous solution for applications in biology. Many of the technical limitations associated with a scanning pipette were circumvented by introducing a small modulation of the distance between the pipette and the sample. We show that this ac method allows the pipette to be positioned very close to the sample surface and is robust in obtaining reproducible NSOM images in solution. This approach is also compatible with fluorescence imaging and fluorescence resonance energy transfer, and should further facilitate the use of NSOM in various areas of cell biology where high resolution is considered to be critical.

  • 20.
    Odén, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Rogström, L.
    Linköping University.
    Terner, Mark
    Hedström, Peter
    Almer, J.
    Argonne National Laboratory, Argonne, IL.
    llavsky, J.
    Argonne National Laboratory, Argonne, IL.
    In situ small-angle x-ray scattering study of nanostructure evolution during decomposition of arc evaporated TiAlN coatings2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 94, no 5, p. 53114-Article in journal (Refereed)
    Abstract [en]

    Small-angle x-ray scattering was used to study in situ decomposition of an arc evaporated TiAlN coating into cubic-TiN and cubic-AlN particles at elevated temperature. At the early stages of decomposition particles with ellipsoidal shape form, which grow and change shape to spherical particles at higher temperatures. The spherical particles grow at a rate of 0.18 Å/°C while coalescing

  • 21.
    Stróecka, Anna
    et al.
    Institut für Bio- und Nanosysteme, Forschungszentrum Jülich.
    Muthukumar, Kaliappan
    Tyndall National Institute, University College Cork.
    Dybek, Aneta
    Department of Physics, Queen Mary University of London.
    Dennis, T. Jiohn S.
    Department of Physics, Queen Mary University of London.
    Larsson, Andreas
    Mysliveček, Josef
    Institut für Bio- und Nanosysteme, Forschungszentrum Jülich.
    Voigtländer, Bert
    Institut für Bio- und Nanosysteme, Forschungszentrum Jülich.
    Modification of the conductance of single fullerene molecules by endohedral doping2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 95, no 13Article in journal (Refereed)
    Abstract [en]

    We use scanning tunneling microscopy to establish controlled contacts to single molecules of endohedrally doped Ce 2@C 80 fullerenes with C 60 as a reference. The stability of the experimental setup allows for the determination of the conductance of Ce 2@C 80 relative to the conductance of C 60. The endohedral doping reduces the conductance of Ce 2@C 80 by a factor of about five with respect to C 60. Ab initio calculations show that the reason for this reduced conductance is the absence of electron orbitals delocalized over the cage of Ce 2@C 80 in the energy window of the conductance measurement

  • 22. Söderberg, Hans
    et al.
    Odén, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Larsson, Tommy
    Hultman, Lars
    Thin Film Physics Division, IFM, Linköping University.
    Molina-Aldareguia, Jon M.
    CEIT and TECNUN, Paseo de Manuel Lardizabal 15, 20018 San Sebastián.
    Epitaxial stabilization of cubic-SiNx in TiN/SiNx multilayers2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 88, p. 191902/1-191902/3Article in journal (Refereed)
    Abstract [en]

    The formation of cubic-phase SiNx is demonstrated in TiN/SiNx multilayers deposited by reactive dual magnetron sputtering. Transmission electron microscopy examination shows a transition from epitaxially stabilized growth of crystalline SiNx to amorphous growth as the layer thickness increases from 0.3 to 0.8 nm. The observations are supported by ab initio calculations on different polytypes, which show that the NaCl structure has the best lattice match to TiN. Calculations also reveal a large difference in elastic shear modulus between NaCl-SiNx and TiN. The results for phase structure and shear modulus offer an explanation for the superhardening effect determined by nanoindentation experiments.

  • 23.
    Ulisse, Giacomo
    et al.
    University of Rome Tor Vergata.
    Brunetti, Francesca
    University of Rome Tor Vergata.
    Vomiero, Alberto
    SENSOR Lab, Department of Chemistry and Physics, Brescia University and CNR-IDASC.
    Natile, Marta M.
    CNR-ISTM.
    Sberveglieri, Giorgio
    CNR IDASC SENSOR Lab.
    Carlo, Aldo Di
    University of Rome Tor Vergata.
    Hybrid thermal-field emission of ZnO nanowires2011In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 99, no 24, article id 243108Article in journal (Refereed)
    Abstract [en]

    The electron emission properties of an array of ZnO nanowires were studied in the temperature range of 300-473 K. An almost doubling of the current density at 473 K under an electric field of 8 V/μm (j (T=473 K) = 190 μA/cm 2, j (T=300 K) = 114 μA/cm 2) was observed together with a reduction of the turn-on field from 552 V/μm to 482 V/μm. Theoretical model that combines the thermal-field emission for high electric field and the Schottky emission for the low field can satisfactorily account for temperature dependence of current at low as well as at high applied bias. The obtained effect is particularly appealing for the application in micro-gun for THz vacuum tubes. © 2011 American Institute of Physics.

  • 24.
    Vomiero, Alberto
    et al.
    INFM-CNR Sensor Lab and Department of Chemistry and Physics for Engineering and Materials, University of Brescia.
    Concina, Isabella
    Department of Physics and Chemistry, INFM — University of Brescia.
    Natile, M. M.
    Department of Chemical Sciences and INSTM Padova, Padova University.
    Comini, E.
    Department of Physics and Chemistry, INFM — University of Brescia.
    Faglia, G.
    Department of Physics and Chemistry, INFM — University of Brescia.
    Ferroni, M.
    Department of Physics and Chemistry, INFM — University of Brescia.
    Kholmanov, I.
    Department of Physics and Chemistry, INFM — University of Brescia.
    Sberveglieri, G.
    Department of Physics and Chemistry, INFM — University of Brescia.
    ZnO/ TiO2 nanonetwork as efficient photoanode in excitonic solar cells2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 95, no 19, article id 193104Article in journal (Refereed)
    Abstract [en]

    An innovative nanonetwork composed of TiO2 nanoparticles and single-crystalline ZnO nanowires is demonstrated as efficient photoanode in excitonic solar cells. Such architecture benefits of the capability of high sensitizer loading offered by the nanoparticles and of the direct conduction path for electrons guaranteed by the nanowires. The combination of these features leads to improved light absorption, electron photogeneration, and charge collection. The nanonetwork was implemented in a dye-sensitized solar-cell architecture demonstrating threefold enhancement of the efficiency with respect to a nanowire photoanode of the same thickness. Cell efficiency of 1.6% was obtained in 1.5 μm thick nanonetwork. © 2009 American Institute of Physics.

  • 25.
    Vomiero, Alberto
    et al.
    Dipartimento di Fisica, Università di Padova.
    Marchi, E. Boscolo
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Mariotto, G.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Quaranta, A.
    INFN-LNL.
    Mea, G. Della
    INFN-LNL.
    Ottaviani, G.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Tonini, R.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Butturi, M.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Martinelli, G.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Composition and resistivity changes of reactively sputtered W-Si-N thin films under vacuum annealing2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 88, no 3, p. 1-3, article id 31917Article in journal (Refereed)
    Abstract [en]

    W-Si-N layers about 200 nm thick with different nitrogen content were reactively sputtered from a W5 Si3 target on oxidized silicon substrates. The thermal stability of the films' composition and resistivity was studied with ion beam analysis and four-point probe measurements. Upon vacuum annealing from 600 to 980 °C for 1.5 h, a sample with an initial 56 at. % of nitrogen gradually loses nitrogen down to 36%. This composition lies close to the W- Si3 N4 tie line. Concurrently, the room temperature resistivity decreases from 4.7 to about 2 mΩ cm. The composition changes only a little for a sample whose initial composition is near the W- Si3 N4 tie line and the resistivity changes significantly less than for the nitrogen-rich film. Interpretations are discussed. © 2006 American Institute of Physics.

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