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  • 1. Adey, J
    et al.
    Jones, R
    Palmer, D W
    Briddon, P R
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Erratum: Degradation of Boron-Doped Czochralski-Grown Silicon Solar Cells [Phys. Rev. Lett., 93, 055504 (2004)]2004Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 93, nr 16, s. 169904-Artikkel i tidsskrift (Annet vitenskapelig)
  • 2.
    Adey, J.
    et al.
    School of Physics, University of Exeter.
    Jones, R.
    School of Physics, University of Exeter.
    Palmer, D.W.
    School of Physics, University of Exeter.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Degradation of boron-doped Czochralski-grown silicon solar cells2004Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 93, nr 5, s. 055504-1Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The formation mechanism and properties of the boron-oxygen center responsible for the degradation of Czochralski-grown Si(B) solar cells during operation is investigated using density functional calculations. We find that boron traps an oxygen dimer to form a bistable defect with a donor level in the upper half of the band gap. The activation energy for its dissociation is found to be 1.2 eV. The formation of the defect from mobile oxygen dimers, which are shown to migrate by a Bourgoin mechanism under minority carrier injection, has a calculated activation energy of 0.3 eV. These energies and the dependence of the generation rate of the recombination center on boron concentration are in good agreement with observations.

  • 3.
    Blumenau, A.T.
    et al.
    School of Physics, University of Exeter.
    Jones, R.
    School of Physics, University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P.R.
    Department of Physics, University of Newcastle.
    Frauenheim, T.
    Theoretische Physik, Universität Paderborn.
    Dislocation related photoluminescence in silicon2001Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 87, nr 18, s. 187404-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dislocation related photoluminescence in Si and SiGe is attributed to stable interstitial clusters bound to 60° dislocations. Density functional based total energy calculations in Si give binding energies between 1.5 and 3.6 eV for I3 and I4 clusters with 90° and 30° partials. They possess donor levels around Ev+0.4 eV which are consistent with deep level transient spectroscopic studies on p-Si. It is further suggested that the clusters would act as the obstacles to the movement of dislocations which may have been observed in recent transmission electron microscopy studies.

  • 4.
    Carvalho, A.
    et al.
    School of Physics, University of Exeter.
    Jones, R.
    School of Physics, University of Exeter.
    Janke, C.
    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.
    Coutinho, J.
    Department of Physics and 13N, University of Aveiro, Aveiro.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Self-interstitial in germanium2007Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 99, nr 17, s. 175502-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Low-temperature radiation damage in n- and p-type Ge is strikingly different, reflecting the charge-dependent properties of vacancies and self-interstitials. We find, using density functional theory, that in Ge the interstitial is bistable, preferring a split configuration when neutral and an open cage configuration when positively charged. The split configuration is inert while the cage configuration acts as a double donor. We evaluate the migration energies of the defects and show that the theory is able to explain the principal results of low-temperature electron-irradiation experiments.

  • 5.
    Coutinho, J.
    et al.
    School of Physics, University of Exeter.
    Jones, R.
    School of Physics, University of Exeter.
    Murin, L.I.
    Institute of Solid State and Semiconductor Physics, Minsk.
    Markevich, V.P.
    Centre for Electronic Materials, University of Manchester.
    Lindström, J.L.
    Department of Physics, University of Lund.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P.R.
    Department of Physics, University of Newcastle.
    Thermal double donors and quantum dots2001Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 87, nr 23, s. 235501-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Combined local mode spectroscopy and ab initio modeling are used to demonstrate for the first time that oxygen atoms in thermal double donors (TDD) in Si are in close proximity. The observed vibrational modes in 16O, 18O, and mixed isotopic samples are consistent with a model involving [110] aligned oxygen chains made up of an insulating core lying between electrically active ends. The model also explains the minute spin density observed on oxygen in TDD+ as well as the piezospectroscopic tensors of the donors. The analogy between the thermal donors and quantum dots is emphasized.

  • 6. Ekelin, Svante
    et al.
    Fredriksson, Sverker
    Hadron pT correlations in quark jets1986Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 56, nr 22, s. 2428-2428Artikkel i tidsskrift (Fagfellevurdert)
  • 7.
    Elsner, J
    et al.
    University of Exeter.
    Jones, R
    University of Exeter.
    Stich, P K
    Technische Universität, Chemnitz.
    Porezag, V D
    Technische Universität, Chemnitz.
    Elstner, M
    Technische Universität, Chemnitz.
    Frauenheim, Th
    Technische Universität, Chemnitz.
    Heggie, M I
    University of Sussex.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P R
    University of Newcastle Upon Tyne.
    Theory of threading edge and screw dislocations in GaN1997Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 79, nr 19, s. 3672-3675Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The atomic structures, electrical properties, and line energies for threading screw and threading edge dislocations of wurtzite GaN are calculated within the local-density approximation. Both dislocations are electrically inactive with a band gap free from deep levels. These results are understood to arise from relaxed core structures which are similar to (101̅ 0) surfaces.

  • 8.
    Ewels, C P
    et al.
    University of Exeter.
    Jones, R
    University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Miro, J
    Technical University of Budapest.
    Deák, P
    Technical University of Budapest.
    Shallow thermal donor defects in silicon1996Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 77, nr 5, s. 865-868Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An ab initio local density functional cluster program, aimpro, is used to examine nitrogen related shallow thermal donor defects in silicon. We find the bonding of oxygen with interstitial nitrogen in Ni- O2i to be almost "normal," but the O atoms move slightly out of their bond centered sites causing the deep donor level of Ni to become shallow. The defect has properties consistent with those experimentally observed for shallow thermal donors. We also find that a CiH- O2i defect has very similar electronic properties, and suggest that shallow thermal donors do not have a unique composition.

  • 9. Fredriksson, Sverker
    Clusters and tubes in multiparticle production from nuclear targets1980Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 45, nr 17, s. 1371-1374Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recent data on backward pion production in 0.8-4.89-GeV proton-nucleus collisions are analyzed within the scope of models where target nucleons react collectively. It is shown that the nuclear-size dependence in data is a sensitive probe of the effective target mass. The experimental results hint at a synthesis of the cluster ("fluctuon") model and the collective tube model.

  • 10. Fredriksson, Sverker
    Large-pT π0 Production in High-Energy πp Collisions1976Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 37, nr 21, s. 1373-1374Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is pointed out that the recently measured difference in pT spectrum between π±p→π0X and pp→π0X, with a large-pT π0, seems to be a consequence only of the smaller number of quarks per projectile in a pion beam.

  • 11. Fredriksson, Sverker
    Nuclear structure functions and the size of diquarks in nucleons1984Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 52, nr 9, s. 724-726Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is suggested that the observed difference between deep-inelastic structure functions from iron and deuterium targets comes about because two of the quarks in a nucleon are tightly bound in a diquark. It suffices for reproducing the data to assume that the diquark radius is enhanced by 10%-45% in a dense nucleus because of the disturbance from the surrounding nucleons. It is suggested how such a change of the diquark scale could be distinguished from the recently proposed change in the scale of the whole nucleon.

  • 12. Fredriksson, Sverker
    et al.
    Jändel, Magnus
    The diquark deuteron1982Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 48, nr 1, s. 14-16Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is speculated that an almost stable state of hadronic and nuclear matter can be built from diquarks. It is suggested that this alternative form of matter has already revealed itself in existing experimental data in the form of a diquark "deuteron" with JP=0- and with several other anomalous properties.

  • 13. Fredriksson, Sverker
    et al.
    Jändel, Magnus
    Larsson, Tomas
    Are "Gluon Effects" caused by diquarks?1983Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 51, nr 24, s. 2179-2182Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The possible importance of diquarks in high-energy physics is discussed and it is suggested that this nonperturbative phenomenon can explain the trends in high-energy data that are usually attributed to gluon processes as described by perturbative QCD. Several experimental tests are suggested for discriminating between gluon and diquark phenomena.

  • 14.
    Goss, J P
    et al.
    University of Exeter.
    Jones, R
    University of Exeter.
    Breuer, S J
    University of Exeter.
    Briddon, P R
    University of Newcastle Upon Tyne.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    The twelve-line 1.682 eV luminescence center in diamond and the vacancy-silicon complex1996Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 77, nr 14, s. 3041-3044Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ab initio cluster methods are used to investigate vacancy-impurity complexes in diamond. We assign the 1.682 eV, twelve-line optical band to a vacancy-Si complex which has a very unusual, possibly unique structure with a Si atom at the center of a split vacancy. The method also successfully accounts for the 1.945, 2.156, and 2.985 eV optical transitions in trigonal vacancy-N defects and estimates of radiative lifetimes are given.

  • 15.
    Holbech, J D
    et al.
    University of Aarhus.
    Nielsen, B Bech
    University of Aarhus.
    Jones, R
    University of Exeter.
    Stich, S
    University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    H2* defect in crystalline silicon1993Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 71, nr 6, s. 875-878Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Detailed infrared studies have been carried out on proton- and deuteron-implanted Si. A dominant trigonal defect involving a pair of inequivalent hydrogen atoms has been identified, with local modes at 2061.5, 1838.3, 1599.1, and 817.2 cm-1. The structure, the local modes, and the isotopic shifts of the H2* defect have been calculated using ab initio pseudopotential cluster theory. The structure is consistent with channeling and uniaxial stress experiments. The calculated frequencies and isotopic shifts are in close agreement with those observed.

  • 16.
    Ivanov, Yu M.
    et al.
    Petersburg Nuclear Physics Institute.
    Petrunin, A. A.
    Petersburg Nuclear Physics Institute.
    Skorobogatov, V. V.
    Petersburg Nuclear Physics Institute.
    Gavrikov, Yu A.
    Petersburg Nuclear Physics Institute.
    Gelamkov, A. V.
    Petersburg Nuclear Physics Institute.
    Lapina, L. P.
    Petersburg Nuclear Physics Institute.
    Schetkovsky, A. I.
    Petersburg Nuclear Physics Institute.
    Vavilov, S. A.
    Petersburg Nuclear Physics Institute.
    Baranov, V. I.
    Institute of High Energy Physics - Moscow Region.
    Chesnokov, Yu A.
    Institute of High Energy Physics - Moscow Region.
    Afonin, A. G.
    Institute of High Energy Physics - Moscow Region.
    Baranov, V. T.
    Institute of High Energy Physics - Moscow Region.
    Chepegin, V. N.
    Institute of High Energy Physics - Moscow Region.
    Guidi, V.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Scandale, W.
    European Organization for Nuclear Research.
    Vomiero, Alberto
    Laboratori Nazionali di Legnaro.
    Volume reflection of a proton beam in a bent crystal2006Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 97, nr 14, artikkel-id 144801Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Volume reflection predicted in the mid-1980s by Taratin and Vorobiev has been observed for the first time in the interactions of a 70 GeV proton beam with a short bent crystal. Incident protons deviate from convex atomic planes in the bulk of the crystal as a result of coherent interaction with bent lattice around the tangency point of particle trajectory with a curved atomic plane. The deflection angle 2Î R was found to be (39.5±2.0) Î rad, or (1.65±0.08)Î c in terms of the critical angle for channeling. The process has a large probability with respect to channeling and takes place in the angular range equal to the bend angle of atomic planes. It could possibly open new fields of application of crystals in high-energy particle beam optics. © 2006 The American Physical Society.

  • 17.
    Ivanovskaya, Viktoria V.
    et al.
    Institut des Matériaux Jean Rouxel (IMN), UMR 6502 CNRS, University of Nantes.
    Zobelli, Alberto
    Laboratoire de Physique des Solides, Université Paris-Sud, CNRS UMR 8502, F-91405, Orsay.
    Wagner, Philipp
    Institut des Matériaux Jean Rouxel (IMN), UMR 6502 CNRS, University of Nantes.
    Heggie, Marlcolm I.
    Department of Chemistry, University of Sussex.
    Briddon, Patrick R.
    School of Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Rayson, Mark
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Ewles, Chris P.
    Institut des Matériaux Jean Rouxel (IMN), UMR 6502 CNRS, University of Nantes.
    Low-energy termination of graphene edges via the formation of narrow nanotubes2011Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 107, nr 6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We demonstrate that free graphene sheet edges can curl back on themselves, reconstructing as nanotubes. This results in lower formation energies than any other nonfunctionalized edge structure reported to date in the literature. We determine the critical tube size and formation barrier and compare with density functional simulations of other edge terminations including a new reconstructed Klein edge. Simulated high resolution electron microscopy images show why such rolled edges may be difficult to detect. Rolled zigzag edges serve as metallic conduction channels, separated from the neighboring bulk graphene by a chain of insulating sp3-carbon atoms, and introduce van Hove singularities into the graphene density of states.

  • 18.
    Jones, R
    et al.
    University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Multiple charge states of substitutional oxygen in gallium arsenide1992Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 69, nr 1, s. 136-139Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A local-density-functional cluster method is used to calculate the structure and vibrational modes of substitutional oxygen, OAs, in gallium arsenide. We find the defect can exist in a surprisingly large number of five charge states: On- with n=-1, 0, 1, 2, and 3. The structures of the first two of these are very different from the last three. Their calculated modes are in fair agreement with observations on O in GaP and GaAs. The first pair of defects have a midgap level, and the third has an empty upper-gap level which can become occupied in photoillumination experiments. The consequent structural change causes a lowering in vibrational mode frequency as is observed.

  • 19. Jones, R
    et al.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Oxygen frustration and the interstitial carbon-oxygen complex in Si1993Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 70, nr 8, s. 1186-1186Artikkel i tidsskrift (Fagfellevurdert)
  • 20.
    Jones, R
    et al.
    University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Oxygen frustration and the interstitial carbon-oxygen complex in Si1992Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 68, nr 1, s. 86-89Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The interstitial carbon-oxygen complex is one of the dominant defects produced in electron irradiated Si. In spite of much work, there is no consensus on its structure and a recent model of Trombetta and Watkins seems inconsistent with the lack of strong O-related vibrational modes expected from bond-centered O. Our ab initio cluster calculations reveal very unusual bonding of O in these complexes but yield vibrational modes and isotope shifts which are in reasonable agreement with experiment.

  • 21.
    Jones, R
    et al.
    University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Goss, J
    University of Exeter.
    Briddon, P R
    University of Newcastle Upon Tyne.
    Resende, A
    Universidade de Aveiro.
    Theory of nickel and nickel-hydrogen complexes in silicon1995Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 75, nr 14, s. 2734-2737Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Spin-polarized local density functional cluster calculations are carried out on substitutional Ni and Ni-H2 complexes. We find that Ni- undergoes a Jahn-Teller distortion along 〈100〉 with Ni moving slightly along the cube axis. The distorted state gives b1, b2, and a1 levels in ascending order of energies within the gap in agreement with experiment. Several candidate NiH2 defects are investigated: the lowest energy structure consists of a substitutional Ni atom together with two H atoms at antibonding sites to two Si neighbors of Ni. This gives H related vibrational modes and a spin-polarized charge density close to those reported for Pt-H2.

  • 22.
    Jones, R
    et al.
    University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Rasmussen, F Berg
    University of Aarhus.
    Nielsen, B Bech
    University of Aarhus.
    Identification of the dominant nitrogen defect in silicon1994Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 72, nr 12, s. 1882-1885Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structure of the dominant N pair defect in Si is determined from channeling, infrared local vibrational mode spectroscopy, and ab initio local density functional theory. Channeling experiments show that the N atoms are displaced by 1.1±0.1 Å from lattice sites along 〈100〉. Annealing experiments reveal that this N site is associated with two N-related local vibrational modes originating from the N pair. The ab initio calculations demonstrate that the pair consists of two neighboring 〈100〉 oriented N-Si split interstitials, arranged in an antiparallel configuration, and with four N-Si bonds forming a square lying on {011}.

  • 23.
    Larsen, A. Nylandsted
    et al.
    Institute of Physics and Astronomy, University of Aarhus.
    Mesli, A.
    Institut d'Electronique du Solide et des Systèmes, CNRS/ULP, Strasbourg.
    Nielsen, K. Bonde
    Institute of Physics and Astronomy, University of Aarhus.
    Nielsen, H. Kortegaard
    Institute of Physics and Astronomy, University of Aarhus.
    Dobaczewski, L.
    Institute of Physics, Polish Academy of Sciences.
    Adey, J.
    School of Physics, University of Exeter.
    Jones, R.
    School of Physics, University of Exeter.
    Palmer, D.W.
    School of Physics, University of Exeter.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    E center in silicon has a donor level in the band gap2006Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 97, nr 10, s. 106402/1-106402/4Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It has been an accepted fact for more than 40 years that the E center in Si (the group-V impurity-vacancy pair)-one of the most studied defects in semiconductors-has only one energy level in the band gap: namely, the acceptor level at about 0.45 eV below the conduction band. We now demonstrate that it has a second level, situated in the lower half of the band gap at 0.27 eV above the valence band. The existence of this level, having a donor character, is disclosed by a combination of different transient-capacitance techniques and electronic-structure calculations. The finding seriously questions some diffusion-modeling approaches performed in the past.

  • 24.
    Lehto, Niklas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Effects of dislocation interactions: application to the period-doubled core of the 90° partial in silicon1998Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 80, nr 25, s. 5568-71Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The elastic strain field of a dislocation is highly affected by nearby dislocations. The effects of dislocation-dislocation interactions on elastic energy and core structure are analyzed using a new and self-consistent method to apply periodic boundary conditions on unit cells containing dislocations. Local density functional theory on hydrogen terminated clusters is used to gauge the effects of long-range elastic fields on the core structure of the 90° partial in silicon. It is shown that the single and double period structures of this core are very close in energy, and that the structure adopted probably depends on the environment in which the dislocation is located

  • 25.
    Minnhagen, Petter
    et al.
    Department of Theoretical Physics, Umeå University.
    Kim, Beom Jun
    Department of Theoretical Physics, Umeå University.
    Weber, Hans
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Evidence of two distinct dynamic critical exponents in connection with vortex physics2001Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 87, nr 3, s. 37002-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The dynamic critical exponent z is determined from numerical simulations for the three-dimensional (3D) lattice Coulomb gas (LCG) and the 3D XY models with relaxational dynamics. It is suggested that the dynamics is characterized by two distinct dynamic critical indices z0 and z related to the divergence of the relaxation time τ by τ∝ξz0 and τ∝k-z, where ξ is the correlation length and k the wave vector. The values determined are z0≈1.5 and z≈1 for the 3D LCG and z0≈1.5 and z≈2 for the 3D XY model. Comparisons with other results are discussed.

  • 26.
    Nikolaou, Marios
    et al.
    Kungliga tekniska högskolan, KTH.
    Wallin, Mats
    Kungliga tekniska högskolan, KTH.
    Weber, Hans
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Critical scaling properties at the superfluid transition of 4He in aerogel2006Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 97, nr 22Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study the superfluid transition of 4He in aerogel by Monte Carlo simulations and finite size scaling analysis. Aerogel is a highly porous silica glass, which we model by a diffusion limited cluster aggregation model. The superfluid is modeled by a three dimensional XY model, with excluded bonds to sites on the aerogel cluster. We obtain the correlation length exponent ν=0.73±0.02, in reasonable agreement with experiments and with previous simulations. For the heat capacity exponent α, both experiments and previous simulations suggest deviations from the Josephson hyperscaling relation α=2-dν. In contrast, our Monte Carlo results support hyperscaling with α=-0.2±0.05. We suggest a reinterpretation of the experiments, which avoids scaling violations and is consistent with our simulation results.

  • 27.
    Osuna-Esteban, Susana
    et al.
    Centro de Astrobiología (CSIC-INTA).
    Zorzano, María Paz
    Centro de Astrobiología (CSIC-INTA).
    Menor-Salván, César
    Centro de Astrobiología (CSIC-INTA).
    Ruíz-Bermejo, Marta
    Centro de Astrobiología (CSIC-INTA).
    Veintemillas-Verdaguer, Sabino
    Centro de Astrobiología (CSIC-INTA).
    Asymmetric chiral growth of micron-size NaClO3 crystals in water aerosols2008Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 100, nr 14, artikkel-id 146102Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We describe an aerosol-liquid cycle that launches the autocatalytic amplification of any initial imbalance of the order of 10-7% (1 ppb) up to total chiral purity in a single step process. Crystal nucleation of NaClO3 is initiated at the aerosol air-water interface where, due to the accumulation of ambient chiral impurities or added hydrophobic chiral aminoacids in tiny concentrations (ppb), the initial levorotatory (l) and dextrorotatory (d) excess will not be produced with equal probability. The enantiomeric yield is then enhanced up to homochirality by recycling the crystallites through a liquid phase. In the absence of added catalysts this process leads to preferential (d) homochiral crystallizations in a ratio of 4 1 which is due to ambient contamination. By adding only 2 ppb of (L) or (D) Phe, we induce a final preferential homochiral crystallization of (d) or (l) handedness, respectively, in a ratio of 2 1.

  • 28.
    Resende, A
    et al.
    University of Exeter.
    Jones, R
    University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P R
    University of Newcastle Upon Tyne.
    Calculations of electrical levels of deep centers: application to Au-H and Ag-H defects in silicon1999Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 82, nr 10, s. 2111-2114Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    First-principles local-density formalism cluster theory is used to determine the structure of Au- and Ag-hydrogen complexes in Si. The theory, with an empirical correction, is then applied to extract their donor and acceptor levels and these are compared with capacitance transient spectroscopic measurements. Assignments of these levels to specific H defects are then made. Models for the defects responsible for the neutralization of the electrical activity of the Au and Ag centers are proposed.

  • 29.
    Safonov, A N
    et al.
    King's College London.
    Lightowlers, E C
    King's College London.
    Davies, Gordon
    King's College London.
    Leary, P
    University of Exeter.
    Jones, R
    University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Interstitial-carbon hydrogen interaction in silicon1996Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 77, nr 23, s. 4812-4815Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The T-line luminescence system is created in Si by annealing at 400-600 °C. Shifts and splitting of the spectral features with 13C and D isotope substitution identify the presence of two C atoms and one H atom in the center. Uniaxial stress and magnetic field measurements show that the T center has monoclinic I symmetry and possesses an acceptor ( -/0) level at 0.2 eV below the conduction band. Ab initio cluster calculations lead to a structure in which an interstitial C-H defect binds with a substitutional C atom. The calculated vibrational modes are in good agreement with those observed.

  • 30.
    Scandale, W.
    et al.
    CERN.
    Vomiero, Alberto
    INFM-CNR Sensor Lab.
    Baricordi, S.
    INFN Sezione di Ferrara.
    Dalpiaz, P.
    INFN Sezione di Ferrara.
    Fiorini, M.
    INFN Sezione di Ferrara.
    Guidi, V.
    INFN Sezione di Ferrara.
    Mazzolari, A.
    INFN Sezione di Ferrara.
    Mea, G. Della
    INFN Laboratori Nazionali di Legnaro.
    Milan, R.
    INFN Laboratori Nazionali di Legnaro.
    Ambrosi, G.
    INFN Sezione di Perugia.
    Zuccon, P.
    INFN Sezione di Perugia.
    Bertucci, B.
    INFN Sezione di Perugia.
    Burger, W.
    INFN Sezione di Perugia.
    Duranti, M.
    INFN Sezione di Perugia.
    Cavoto, G.
    INFN Sezione di Roma.
    Santacesaria, R.
    INFN Sezione di Roma.
    Valente, P.
    INFN Sezione di Roma.
    Luci, C.
    INFN Sezione di Roma.
    Iacoangeli, F.
    Dipartimento di Fisica, Universita di Roma La Sapienza Piazzale A.Moro.
    Vallazza, E.
    INFN Sezione di Trieste.
    Afonin, A. G.
    Institute of High Energy Physics - Moscow Region.
    Chesnokov, Yu A.
    Institute of High Energy Physics - Moscow Region.
    Kotov, V. I.
    Institute of High Energy Physics - Moscow Region.
    Maisheev, V. A.
    Institute of High Energy Physics - Moscow Region.
    Yazynin, I. A.
    Institute of High Energy Physics - Moscow Region.
    Prest, M.
    Università dell'Insubria.
    Observation of multiple volume reflection of ultrarelativistic protons by a sequence of several bent silicon crystals2009Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 102, nr 8, artikkel-id 84801Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The interactions of 400 GeV protons with different sequences of bent silicon crystals have been investigated at the H8 beam line of the CERN Super Proton Synchrotron. The multiple volume reflection of the proton beam has been studied in detail on a five-crystal reflector measuring an angular beam deflection θ=52.96±0.14μrad. The efficiency was found larger than 80% for an angular acceptance at the reflector entrance of 70μrad, with a maximal efficiency value of ε=0.90±0.01±0.03. © 2009 The American Physical Society.

  • 31.
    Scandale, W.
    et al.
    CERN.
    Vomiero, Alberto
    INFM-CNR Sensor Lab.
    Baricordi, S.
    INFN Sezione di Ferrara.
    Dalpiaz, P.
    INFN Sezione di Ferrara.
    Fiorini, M.
    INFN Sezione di Ferrara.
    Guidi, V.
    INFN Sezione di Ferrara.
    Mazzolari, A.
    INFN Sezione di Ferrara.
    Milan, R.
    INFN Laboratori Nazionali di Legnaro.
    Mea, Gianantonio Della
    Dipartimento di Ingegneria dei Materiali, Università di Trento.
    Ambrosi, G.
    INFN Sezione di Perugia.
    Bertucci, B.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Burger, W. J.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Duranti, M.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Zuccon, P.
    INFN Sezione di Perugia.
    Cavoto, G.
    INFN Sezione di Roma.
    Iacoangeli, F.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Luci, C.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Pisano, S.
    Dipartimento di Fisica Sperimentale, Università di Torino.
    Santacesaria, R.
    INFN Sezione di Roma.
    Valente, P.
    INFN Sezione di Roma.
    Vallazza, E.
    INFN Sezione di Trieste.
    Afonin, A. G.
    Institute of High Energy Physics - Moscow Region.
    Chesnokov, Yu A.
    Institute of High Energy Physics - Moscow Region.
    Kotov, V. I.
    Institute of High Energy Physics - Moscow Region.
    Maisheev, V. A.
    Institute of High Energy Physics - Moscow Region.
    Prest, M.
    Università dell'Insubria.
    Volume reflection dependence of 400GeV/c protons on the bent crystal curvature2008Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 101, nr 23, artikkel-id 234801Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The trend of volume reflection parameters (deflection angle and efficiency) in a bent (110) silicon crystal has been investigated as a function of the crystal curvature with 400GeV/c protons on the H8 beam line at the CERN Super Proton Synchrotron. This Letter describes the analysis performed at six different curvatures showing that the optimal radius for volume reflection is approximately 10 times greater than the critical radius for channeling. A strong scattering of the beam by the planar potential is also observed for a bend radius close to the critical one. © 2008 The American Physical Society.

  • 32.
    Scandale, Walter
    et al.
    CERN.
    Still, Dean A.
    Fermi National Accelerator Laboratory.
    Carnera, Alberto
    INFN Laboratori Nazionali di Legnaro.
    Mea, Gianantonio Della
    INFN Laboratori Nazionali di Legnaro.
    Salvador, Davide De
    INFN Laboratori Nazionali di Legnaro.
    Milan, Riccardo
    INFN Laboratori Nazionali di Legnaro.
    Vomiero, Alberto
    INFN Laboratori Nazionali di Legnaro.
    Baricordi, Stefano
    INFN Sezione di Ferrara.
    Dalpiaz, Pietro
    INFN Sezione di Ferrara.
    Fiorini, Massimiliano
    INFN Sezione di Ferrara.
    Guidi, Vincenzo
    INFN Sezione di Ferrara.
    Martinelli, Giuliano
    INFN Sezione di Ferrara.
    Mazzolari, Andrea
    INFN Sezione di Ferrara.
    Milan, Emiliano
    INFN Sezione di Ferrara.
    Ambrosi, Giovanni
    INFN Sezione di Perugia.
    Azzarello, Philipp
    INFN Sezione di Perugia.
    Battiston, Roberto
    INFN Sezione di Perugia.
    Bertucci, Bruna
    INFN Sezione di Perugia.
    Burger, William J.
    INFN Sezione di Perugia.
    Ionica, Maria
    INFN Sezione di Perugia.
    Zuccon, Paolo
    INFN Sezione di Perugia.
    Cavoto, Gianluca
    INFN Sezione di Roma.
    Santacesaria, Roberta
    INFN Sezione di Roma.
    Valente, Paolo
    INFN Sezione di Roma.
    Vallazza, Erik
    INFN Sezione di Trieste.
    Prest, Michela
    Universita Degli Studi di Padova.
    High-efficiency volume reflection of an ultrarelativistic proton beam with a bent silicon crystal2007Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 98, nr 15, artikkel-id 154801Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The volume reflection phenomenon was detected while investigating 400 GeV proton interactions with bent silicon crystals in the external beam H8 of the CERN Super Proton Synchrotron. Such a process was observed for a wide interval of crystal orientations relative to the beam axis, and its efficiency exceeds 95%, thereby surpassing any previously observed value. These observations suggest new perspectives for the manipulation of high-energy beams, e.g., for collimation and extraction in new-generation hadron colliders, such as the CERN Large Hadron Collider. © 2007 The American Physical Society.

  • 33.
    Scandale, Walter
    et al.
    CERN.
    Vomiero, Alberto
    INFM-CNR Sensor Lab.
    Baricordi, Stefano
    INFN Sezione di Ferrara.
    Dalpiaz, Pietro
    INFN Sezione di Ferrara.
    Fiorini, Massimiliano
    INFN Sezione di Ferrara.
    Guidi, Vincenzo
    INFN Sezione di Ferrara.
    Mazzolari, Andrea
    INFN Sezione di Ferrara.
    Mea, Gianantonio Della
    INFN Laboratori Nazionali di Legnaro.
    Milan, Riccardo
    INFN Laboratori Nazionali di Legnaro.
    Ambrosi, Giovanni
    INFN Sezione di Perugia.
    Bertucci, Bruna
    INFN Sezione di Perugia.
    Burger, William J.
    INFN Sezione di Perugia.
    Zuccon, Paolo
    INFN Sezione di Perugia.
    Cavoto, Gianluca
    INFN Sezione di Roma.
    Luci, Claudio
    INFN Sezione di Roma.
    Santacesaria, Roberta
    INFN Sezione di Roma.
    Valente, Paolo
    INFN Sezione di Roma.
    Vallazza, Erik
    INFN Sezione di Trieste.
    Afonin, Alexander G.
    Institute of High Energy Physics - Moscow Region.
    Chesnokov, Yury A.
    Institute of High Energy Physics - Moscow Region.
    Maisheev, Vladimir A.
    Institute of High Energy Physics - Moscow Region.
    Yazynin, Igor A.
    Institute of High Energy Physics - Moscow Region.
    Kovalenko, Alexander D.
    Joint Institute for Nuclear Research, Dubna.
    Taratin, Alexander M.
    Joint Institute for Nuclear Research, Dubna.
    Denisov, Alexander S.
    Petersburg Nuclear Physics Institute.
    Michela, Prest
    Università dell'Insubria.
    High-efficiency deflection of high-energy protons through axial channeling in a bent crystal2008Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 101, nr 16, artikkel-id 164801Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Beam deflection due to axial channeling in a silicon crystal bent along the 111 axis was observed with 400GeV/c protons at the CERN Super Proton Synchrotron. The condition for doughnut scattering of protons by the atomic strings of the crystal was attained. Such a condition allowed one to observe a beam deflection of 50μrad with about 30% efficiency. The contribution of hyperchanneled states of protons to the observed beam deflection was less than 2% according to simulation results. © 2008 The American Physical Society.

  • 34. Shaw, M. J.
    et al.
    Briddon, P. R.
    Goss, J. P.
    Rayson, Mark
    Kerridge, A.
    Harker, A. H.
    Stoneham, A. M.
    Importance of Quantum Tunneling in Vacancy-Hydrogen Complexes in Diamond2005Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 95, s. 105502-Artikkel i tidsskrift (Fagfellevurdert)
  • 35. Sundqvist, B.
    et al.
    Andersson, O.
    Soldatov, Alexander
    Comment on "Pressure-Induced Structural Metastability in Crystalline C60"1995Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 75, nr 15, s. 2906-2906Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    A Comment of the Letter by J. A. Wolk, P. J. Horoyski, and M. L. W. Thewalt Phys. Rev. Lett. 74, 3483 (1995). The authors of the Letter offer a Reply

  • 36.
    Trevethan, Thomas
    et al.
    Department of Chemistry, University of Surrey.
    Dyulgerova, Polina
    Department of Chemistry, University of Surrey.
    Latham, Chris
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Heggie, Malcolm
    Department of Chemistry, University of Surrey.
    Seabourne, Che
    Institute for Materials Research, SPEME, University of Leeds.
    Scott, Andrew
    Institute for Materials Research, SPEME, University of Leeds.
    Briddon, Patrick
    School of Electrical and Electronic Engineering, University of Newcastle upon Tyne.
    Rayson, Mark
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Extended interplanar linking in graphite formed from vacancy aggregates2013Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 111, nr 9, artikkel-id 95501Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The mechanical and electrical properties of graphite and related materials such as multilayer graphene depend strongly on the presence of defects in the lattice structure, particularly those which create links between adjacent planes. We present findings which suggest the existence of a new type of defect in the graphite or graphene structure which connects adjacent planes through continuous hexagonal sp² bonding alone and can form through the aggregation of individual vacancy defects. The energetics and kinetics of the formation of this type of defect are investigated with atomistic density functional theory calculations. The resultant structures are then employed to simulate high resolution transmission electron microscopy images, which are compared to recent experimental images of electron irradiation damaged graphite.

  • 37.
    Wagner, J
    et al.
    Fraunhofer-Institut für Angewandte Festkörperphysik, Tullastrasse 72, D-79108 Freiburg.
    Newman, R C
    Imperial College of Science.
    Davidson, B R
    Imperial College of Science.
    Westwater, S P
    University of Liverpool.
    Bullough, T J
    University of Liverpool.
    Joyce, T B
    University of Liverpool.
    Latham, Chris
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Jones, R
    University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Di-Carbon defects in annealed highly carbon doped GaAs1997Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 78, nr 1, s. 74-77Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Formation of bonded dicarbon C-C centers is deduced from the observation of Raman lines at 1742, 1708, and 1674 cm -1 in GaAs codoped with 12C and 13C after annealing at 850 °C with concomitant loss of vibrational scattering from CAs. The frequencies agree with results of ab initio theory for a C-C split interstitial (deep donor) formed by the trapping of a mobile interstitial C (displaced CAs) atom by an undisplaced CAs acceptor. Other mechanisms of carrier loss are inferred since a weaker Raman triplet is detected at 1859, 1824, and 1788 cm -1 from a different C-C complex.

  • 38.
    Weber, Hans
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Jensen, Henrik
    Imperial College.
    Monte Carlo Calculation of the Linear Resistance of a Three Dimensional Lattice superconductor Model in the London Limit1997Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 78, nr 13, s. 2620-2623Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have studied the linear resistance of a three dimensional lattice superconductor model in the London limit by Monte Carlo simulation of the vortex loop dynamics. We find excellent finite size scaling at the phase transition. We determine the dynamical exponent z = 1.51 for the isotropic London lattice model.

  • 39.
    Zhang, Jianyang
    et al.
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, People’s Republic of China.
    Dai, Dongxu
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, People’s Republic of China.
    Wang, Chia C.
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, People’s Republic of China.
    Harich, Steven A.
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, People’s Republic of China.
    Wang, Xiuyan
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, People’s Republic of China.
    Yang, Xueming
    State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, People’s Republic of China.
    Gustafsson, Magnus
    Department of Chemistry and Biochemistry, University of Colorado, Boulder.
    Skodje, Rex T.
    Department of Chemistry and Biochemistry, University of Colorado, Boulder.
    State to State to State Dynamics of the D+H2→HD+H Reaction: Control of Transition-State Pathways via Reagent Orientation2006Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 96, nr 9, artikkel-id 93201Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of reagent rotation on the dynamics of the D+H2→HD+H reaction is studied. The state-resolved differential cross section is measured using the Rydberg-atom scheme in a crossed beam experiment. It is found that the H2 rotation has a strong influence on the results. This effect was traced to the selection of the quantum bottleneck states through reagent orientation, thus suggesting a novel strategy to control the transition-state pathways in direct chemical reactions.

  • 40.
    Ziese, M.
    et al.
    Leipzig University, Abteilung Supraleitung & Magnetismus.
    Vrejoiu, I.
    Max-Planck-Institut für Mikrostrukturphysik.
    Pippel, E.
    Max-Planck-Institut für Mikrostrukturphysik.
    Esquinazi, P.
    Leipzig University, Abteilung Supraleitung & Magnetismus.
    Hesse, D.
    Max-Planck-Institut für Mikrostrukturphysik.
    Etz, Corina
    Max-Planck-Institut für Mikrostrukturphysik.
    Henk, J.
    Martin Luther Universität.
    Ernst, A.
    Max-Planck-Institut für Mikrostrukturphysik.
    Maznichenko, Igor
    Institut für Physik, Martin-Luther-Universität Halle-Wittenberg.
    Hergert, W.
    Institut für Physik, Martin-Luther-Universität Halle-Wittenberg.
    Mertig, Ingrid
    Institut für Physik, Martin-Luther-Universität Halle-Wittenberg.
    Tailoring Magnetic Interlayer Coupling in La0.7Sr0.3MnO3/SrRuO3 Superlattices2010Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 104, nr 16, artikkel-id 167203Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The magnetic interlayer coupling in La0.7Sr0.3MnO3/SrRuO3 superlattices was investigated. High quality superlattices with ultrathin La0.7Sr0.3MnO3 and SrRuO3 layers were fabricated by pulsed laser deposition. The superlattices grew coherently with Mn/Ru intermixing restricted to about one interfacial monolayer. Strong antiferromagnetic interlayer coupling depended delicately on magnetocrystalline anisotropy and intermixing at interfaces. Ab initio calculations elucidated that the antiferromagnetic coupling is mediated by the Mn-O-Ru bond. The theoretical calculations allowed for a quantitative correlation between the total magnetic moment of the superlattice and the degree of Mn/Ru intermixing.

  • 41.
    Åström, Jan A.
    et al.
    Centre for Scientific Computing, Esbo.
    Ouchterlony, Finn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Linna, R.P.
    Department of Physics, University of Jyväskylä.
    Timonen, J.
    Department of Physics, University of Jyväskylä.
    Universal dynamic fragmentation in D dimensions2004Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 92, nr 24, s. 245506-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A generic model is introduced for brittle fragmentation in D dimensions, and this model is shown to lead to a fragment-size distribution with two distinct components. In the small fragment-size limit a scale-invariant size distribution results from a crack branching-merging process. At larger sizes the distribution becomes exponential as a result of a Poisson process, which introduces a large-scale cutoff. Numerical simulations are used to demonstrate the validity of the distribution for D = 2. Data from laboratory-scale experiments and large-scale quarry blastings of granitic gneiss confirm its validity for D = 3. In the experiments the nonzero grain size of rock causes deviation from the ideal model distribution in the small-size limit. The size of the cutoff seems to diverge at the minimum energy sufficient for fragmentation to occur, but the scaling exponent is not universal.

  • 42.
    Öberg, Sven
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Ewels, C P
    University of Exeter.
    Jones, R
    University of Exeter.
    Hallberg, T
    Linköping University.
    Lindström, J L
    Linköping University.
    Murin, L I
    Institute of Solid State and Semiconductor Physics, Minsk.
    Briddon, P R
    University of Newcastle Upon Tyne.
    First stage of oxygen aggregation in silicon: the oxygen dimer1998Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 81, nr 14, s. 2930-2933Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structure and dynamic properties of the interstitial oxygen dimer in silicon are found using a combination of infrared spectroscopy and ab initio modeling. We find that the stable dimer consists of a pair of inequivalent weakly coupled interstitial oxygen atoms separated by a Si-Si bond. Two high frequency modes are decoupled in one 16O-18O combination but are strongly mixed in the other combination. A third lower lying mode involves the compression of the Si-Si bond joining the oxygen atoms and gives distinct modes in the mixed 16O-18O case.

1 - 42 of 42
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