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  • 251.
    Carro, Maria J.
    et al.
    Departamento de Matemàtica, Aplicada i Anàlisi, Universitat de Barcelona.
    Ericsson, Stefan
    Persson, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    S-divisibility property and a Holmstedt type formula1999Inngår i: Journal of Approximation Theory, ISSN 0021-9045, E-ISSN 1096-0430, Vol. 98, nr 1, s. 1-24Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Given a conePof positive functions and an operatorS: →Pwith an additive group, we extend the concept ofK-divisibility to get some new formulas for theK-functional of finite families of lattices. Applications are given in the setting of rearrangement invariant spaces and weighted Lorentz spaces. As a consequence of our results, we also obtain a generalized Holmstedt formula due to Asekritova

  • 252.
    Carro, Maria J.
    et al.
    Departamento de Matemàtica, Aplicada i Anàlisi, Universitat de Barcelona.
    Nikolova, Ljudmila I.
    Department of Mathematics, Sofia University.
    Peetre, Jaak
    Department of Mathematics, University of Lund.
    Persson, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Some real interpolation methods for families of Banach spaces: a comparison1997Inngår i: Journal of Approximation Theory, ISSN 0021-9045, E-ISSN 1096-0430, Vol. 89, nr 1, s. 26-57Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We consider certain real interpolation methods for families of Banach spaces. We also define some new such methods obtained by passing to the limit in the constructions of Sparr and Cobos-Peetre. The relations between all these methods are studied. Characterizations of minimal and maximal spaces are obtained. Some concrete examples as well as sharp estimates of the corresponding operator norms are also exhibited.

  • 253.
    Carro, Maria J.
    et al.
    University of Barcelona.
    Nikolova, Ludmila
    Persson, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Norms of interpolation operators controlled by the Dicesar function2000Inngår i: Function spaces and applications / [ed] David E. Edmunds, New Delhi: University of Dehli , 2000, s. 44-59Konferansepaper (Fagfellevurdert)
  • 254.
    Carvahlo, A.
    et al.
    Department of Physics, I3N, University of Aveiro, Campus Santiago.
    Coutinho, J.
    Department of Physics, I3N, University of Aveiro, Campus Santiago.
    Barroso, M.
    Department of Physics, I3N, University of Aveiro, Campus Santiago.
    Silva, E.L.
    Department of Physics, CEMDRX and CFC, Faculty of Science and Technology, University of Coimbra.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Rayson, Mark
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P.R.
    Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Electronic structure modification of Si nanocrystals with F(4)-TCNQ2011Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, nr 12Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We use first-principles models to demonstrate how an organic oxidizing agent F(4)-TCNQ (7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane) modifies the electronic structure of silicon nanocrystals, suggesting it may enhance p-type carrier density and mobility. The proximity of the lowest unoccupied level of F(4)-TCNQ to the highest occupied level of the Si nanocrystals leads to the formation of an empty hybrid state overlapping both the nanocrystal and molecule, reducing the excitation energy to similar to 0.8-1 eV in vacuum. Hence, it is suggested that F(4)-TCNQ can serve both as a surface oxidant and as a mediator for hole hopping between adjacent nanocrystals in p-type doped silicon nanocrystal networks

  • 255.
    Carvahlo, A.
    et al.
    School of Physics, University of Exeter.
    Jones, R.
    School of Physics, University of Exeter.
    Coutinho, J.
    Department of Physics, University of Aveiro.
    Shaw, M.
    School of Natural Science, University of Newcastle upon Tyne.
    Torres, V.J.B.
    Department of Physics, University of Aveiro.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Studies of the VO centre in Ge using first principles cluster calculations2006Inngår i: Materials Science in Semiconductor Processing, ISSN 1369-8001, E-ISSN 1873-4081, Vol. 9, nr 4-5, s. 489-493Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The small or near-zero band gap of germanium found by supercell local density functional treatments causes difficulties in the study of the properties of charged defects in Ge. Here, we use large H-terminated Ge clusters together with a non-linear core corrected (NLCC) Ge pseudopotential to explore the structure, vibrational and electrical properties of the vacancy-oxygen complex (VO). The cluster possesses a gap sufficiently wide to contain defect related energy levels, thus allowing us to model the three charge states of the defect. The local vibrational modes (LVM) calculated for the neutral (VO0), negatively charged (VO-) and double negative (VO=) defect are 602, 684 and 694 cm- 1, and can be favourably compared with experimental values of 621, 669 and 716 cm- 1, respectively [Markevich VP, et al. Physica B 2003; 340-2, 844-8]. Using substitutional gold (Aus) as a marker defect, electric levels of VO are found at E (-/ 0) = Ev + 0.30 eV and E (= /-) = Ec - 0.29 eV, in excellent agreement with the respective experimental enthalpies for hole and electron emission Δ Hh (-/ 0) ≃ 0.32 eV and Δ He (= /-) = 0.26 eV, respectively. Finally, the migration, dissociation and reorientation energies of the defect are also reported.

  • 256.
    Carvahlo, A.
    et al.
    School of Physics, University of Exeter.
    Tagantsev, A.K.
    Ceramics Laboratory, Swiss Federal Institute of Technology (EPFL), Lausanne.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P.R.
    School of Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Setter, N.
    Ceramics Laboratory, Swiss Federal Institute of Technology (EPFL), Lausanne.
    Cation-site intrinsic defects in Zn-doped CdTe2010Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 81, nr 7, s. 75215-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The properties of the cation vacancy and the Te antisite, two dominant defects in CdTe and Cd1-xZnxTe alloys grown in Te-rich conditions, are examined using first-principles calculations. First, the structure, electronic levels, and migration paths of V-Cd and Te-Cd in CdTe are studied in detail. Additionally, we analyze the evolution of the stability and electronic properties in Cd1-xZnxTe alloys, taking into account both the role of alloying in the position of the ionization levels and its effects on the equilibrium concentration of those two defects. It is shown that the formation of cation vacancies becomes progressively more favorable as x increases, whereas Te antisites become less stable, backing the trend towards p-type conductivity in dilute Cd1-xZnxTe.

  • 257.
    Carvahlo, A.
    et al.
    Department of Physics, I3N, University of Aveiro, Campus Santiago.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Rayson, Mark
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P.R.
    Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Electronic properties, doping, and defects in chlorinated silicon nanocrystals2012Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 86, nr 4Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Silicon nanocrystals with diameters between 1 and 3 nm and surfaces passivated by chlorine or a mixture of chlorine and hydrogen were modeled using density functional theory, and their properties compared with those of fully hydrogenated nanocrystals. It is found that fully and partially chlorinated nanocrystals are stable, and have higher electron affinity, higher ionization energy, and lower optical absorption energy threshold. As the hydrogenated silicon nanocrystals, chlorinated silicon nanocrystals doped with phosphorus or boron require a high activation energy to transfer an electron or hole, respectively, to undoped silicon nanocrystals. The electronic levels of surface dangling bonds are similar for both types of surface passivation, although in the chlorinated silicon nanocrystals some fall outside the narrower energy gap.

  • 258.
    Carvalho, A.
    et al.
    School of Physics, University of Exeter.
    Barker, S.J.
    Centre for Electronic Materials and Devices, Imperial College, London.
    Jones, R.
    School of Physics, University of Exeter.
    Williams, R.S.
    Centre for Electronic Materials and Devices, Imperial College, London.
    Ashwin, M.J.
    Centre for Electronic Materials and Devices, Imperial College, London.
    Newman, R.C.
    Centre for Electronic Materials and Devices, Imperial College, London.
    Stavrinou, P.N.
    Centre for Electronic Materials and Devices, Imperial College, London.
    Parry, G.
    Centre for Electronic Materials and Devices, Imperial College, London.
    Jones, T.S.
    Centre for Electronic Materials and Devices, Imperial College, London.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Identification of the local vibrational modes of small nitrogen clusters in dilute GaAsN2007Inngår i: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 401-402, s. 339-342Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ultra-high-resolution infra-red local vibrational mode (IR LVM) spectroscopy measurements together with density-functional calculations have been used to identify the signatures of close substitutional nitrogen (NAs) pairs in GaAs1 - x Nx alloys with concentrations of x < 0.025. We show that the presence of sub-peaks close to the NAs absorption band can be attributed to nitrogen pairs up to fourth neighbor position. Additionally, we suggest that the nitrogen pairs which give rise to the deepest levels below the conduction band edge are the first to be removed upon annealing

  • 259.
    Carvalho, A.
    et al.
    School of Physics, University of Exeter.
    Coutinho, J.
    Department of Physics, University of Aveiro.
    Jones, R.
    School of Physics, University of Exeter.
    Silva, E.
    Department of Physics, University of Aveiro.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Density-functional theory study of Au, Ag and Cu defects in germanium2008Inngår i: Materials Science in Semiconductor Processing, ISSN 1369-8001, E-ISSN 1873-4081, Vol. 11, nr 5, s. 340-343Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Gold, silver and copper defects in germanium are modeled using density functional theory. The structures and electrical properties of the substitutional metals are calculated in excellent agreement with experiment. Interstitial Au, Ag and Cu are found to be shallow donors, in disagreement with a previous assignment of Cui to a hole trap in the lower half of the gap. Substitutional-interstitial metal (Mi - Ms) pairs and metal-vacancy pairs (Ms - V) are also investigated.

  • 260.
    Carvalho, A.
    et al.
    University of Exeter.
    Jones, R.
    University of Exeter.
    Coutinho, J.
    University of Aveiro.
    Torres, V. J. B.
    University of Aveiro.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Alsina, J. M. Campanera
    University of Sussex.
    Shaw, M.
    University of Newcastle Upon Tyne.
    Briddon, P. R.
    University of Newcastle Upon Tyne.
    Local-density-functional calculations of the vacancy-oxygen center in Ge2007Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, nr 11Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We carry out a comprehensive density-functional study of the vacancy-oxygen (VO) center in germanium using large H-terminated Ge clusters. The importance of a nonlinear core correction to account for the involvement of the 3d electrons in Ge-O bonds is discussed. We calculate the electrical levels and the vibrational modes of VO0, VO-, and VO= finding close agreement with experiment. We also explore the reorientation, migration, and dissociation mechanisms of neutral and negatively charged VO and compare the calculated energy barriers with experimental data. We conclude that the defect is likely to anneal through both mechanisms.

  • 261.
    Carvalho, A.
    et al.
    School of Physics, University of Exeter.
    Jones, R.
    School of Physics, University of Exeter.
    Goss, J.
    School of Natural Science, University of Newcastle upon Tyne.
    Janke, C.
    School of Physics, University of Exeter.
    Coutinho, J.
    Department of Physics, University of Aveiro.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Self-interstitials and Frenkel pairs in electron-irradiated germanium2007Inngår i: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 401-402, s. 495-498Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    First principles calculations were used to study the structures and electrical levels of the self-interstitial in Ge. We considered the possibility of structural changes consequent with change in charge state and show these have important implications in the mobility and electrical activity of the defect. The theoretical model is compared to the results of low temperature electron irradiation in germanium reported in the literature.

  • 262.
    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.

  • 263.
    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.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    First-principles study of the diffusion mechanisms of the self-interstitial in germanium2008Inngår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 20, nr 13Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The self-interstitial in germanium can assume multiple configurations depending on the temperature and charge state. Here, we employ a first-principles density functional method to investigate the diffusion mechanisms of this defect. The energy barriers associated with the transformation between different structures are determined by the climbing nudged elastic band method, as a function of the charge state. The relation between the thermodynamic properties of the self-interstitial and the temperature evolution of electron radiation damage in germanium are discussed.

  • 264.
    Carvalho, A.
    et al.
    University of Exeter.
    Jones, R.
    University of Exeter.
    Janke, C.
    University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P.R.
    University of Newcastle Upon Tyne.
    Primary defects in n-type irradiated germanium: a first-principles investigation2008Inngår i: Solid State Phenomena, ISSN 1012-0394, E-ISSN 1662-9779, Vol. 131-133, s. 253-258Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The properties of point defects introduced by low temperature electron irradiation of germanium are investigated by first-principles modeling. Close Frenkel pairs, including the metastable fourfold coordinated defect, are modelled and their stability is discussed. It is found that damage evolution upon annealing below room temperature can be consistently explained with the formation of correlated interstitial-vacancy pairs if the charge-dependent properties of the vacancy and self-interstitial are taken into account. We propose that Frenkel pairs can trap up to two electrons and are responsible for conductivity loss in n-type Ge at low temperatures.

  • 265.
    Carvalho, A.
    et al.
    University of Exeter.
    Jones, R.
    University of Exeter.
    Torres, V. J. B.
    University of Aveiro.
    Coutinho, J.
    University of Aveiro.
    Markevich, V.
    University of Manchester.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P. R.
    University of Newcastle Upon Tyne.
    Oxygen defects in irradiated germanium2007Inngår i: Journal of materials science. Materials in electronics, ISSN 0957-4522, E-ISSN 1573-482X, Vol. 18, nr 7, s. 781-786Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The defects present in oxygen-rich irradiated germanium have been extensively characterised from an experimental point of view. Here, we summarise recent theoretical findings obtained using the cluster method and discuss their relation with the experimental data. In order to find a microscopic interpretation of the reactions taking place in this material upon annealing up to 400°C, we performed nudged elastic band (NEB) calculations of the migration and dissociation paths of VO, as well as a modelling of other oxygen-related complexes that are expected to form in this temperature range. Energy barriers of 1.5 (1.1) eV and 1.2 (0.9) eV for the dissociation and migration of the neutral (negatively charged) VO defect are found. We compare these with the activation energies estimated from the analysis of Hall effect, deep level transient spectroscopy (DLTS) and infra-red (IR) spectroscopy annealing data reported in literature.

  • 266.
    Carvalho, A.
    et al.
    Swiss Federal Institute of Technology.
    Tagantsev, A.
    Swiss Federal Institute of Technology.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P.R.
    University of Newcastle Upon Tyne.
    Setter, N.
    Swiss Federal Institute of Technology.
    Intrinsic defects in CdTe and CdZnTe alloys2009Inngår i: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 404, nr 23-24, s. 5019-5021Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Cd vacancy (VCd) and Te anti-site (TeCd) are two dominant defects in CdTe and CdZnTe alloys grown in Terich conditions. We examine the properties of these two intrinsic defects in Cd1-xZnxTe alloys with x < 0:5 using first-principles calculations. It is shown that Cd vacancies become progressively more favourable with increasing Zn content, in contrast with Te anti-sites, which show the opposite behaviour, explaining the trend towards p-type conductivity in Cd1-xZnxTe.

  • 267.
    Carvalho, A.
    et al.
    Ceramics Laboratory, Swiss Federal Institute of Technology (EPFL), Lausanne.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Intrinsic defect complexes in CdTe and ZnTe2011Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 519, nr 21, s. 7468-7471Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Radiation defects in CdTe and ZnTe are modeled from first principles. The most important intrinsic defects resulting from cation evaporation or displacement are cation vacancies and tellurium anti-sites, electrically active defects characterized by a low formation energy. The reactions between those two defects are investigated. Since cation vacancy clusters of less than four vacancies are not stable, it is argued that cation vacancy aggregation is not a dominant process in near-equilibrium conditions. In-grown or radiation-induced clusters of four cation vacancies may serve as a nucleation center for tellurium precipitation. The formation energy of these small voids is lower in ZnTe than in CdTe. Additionally, cation-anion divacancies are stable in ZnTe and in p-type CdTe.

  • 268.
    Carvalho, Alexandra
    et al.
    Department of Physics, University of Aveiro, Campus Santiago.
    Rayson, Mark
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, Patrick R.
    Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Effect of oxidation on the doping of silicon nanocrystals with group III and group v elements2012Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, nr 14, s. 8243-8250Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Substitutional group III and group V elements, though commonly used as shallow dopants in bulk silicon, have a limited efficiency in silicon nanocrystals. In this work, we use first-principles models of 1.5 nm nanocrystals with hydride- and silanol-terminated surfaces to understand how oxidation influences the segregation and deactivation of dopants at the surface and the dopant binding energies. We show that the surface oxygen layer changes drastically the radial dependence of the dopant formation energy both for donors and for acceptors, but that, independently from the oxidation, dopant diffusion does not take place at operating conditions. Additionally, we show that the oxidation increases the electron binding energy of the P, As, and Sb and decreases the hole binding energy of B, Al, Ga, and In.

  • 269.
    Carvalho, Alexandra
    et al.
    Department of Physics, I3N, University of Aveiro, Campus Santiago.
    Santos, Paulo
    Department of Physics, I3N, University of Aveiro, Campus Santiago.
    Coutinho, José
    Department of Physics, I3N, University of Aveiro, Campus Santiago.
    Jones, Robert
    School of Physics, University of Exeter.
    Rayson, Mark
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, Patrick R.
    Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Light induced degradation in B doped Cz-Si solar cells2012Inngår i: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 209, nr 10, s. 1894-1897Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We analyse the formation energy of interstitial boron (Bi) and the properties of the defect resulting from its association with an oxygen dimer (BiO2i) to evaluate the possibility that it may be the slow-forming centre responsible for the light-induced degradation of B-doped Si solar cells. However, we find that the formation energy of Bi is too high, and therefore its concentration is negligible. Moreover, we find that the lowest energy form of BiO2i is a shallow donor, and the deep donor form is high in energy. Lowest energy structure of the BiO2i defect.

  • 270.
    Carvalho, Alexandra T.G.
    et al.
    Department of Physics, I3N, University of Aveiro, Campus Santiago.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Rayson, Mark
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, Patrick R.
    School of Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Electronic and optical properties of chlorinated silicon nanoparticles2013Inngår i: Journal of Nanoscience and Nanotechnology, ISSN 1533-4880, E-ISSN 1533-4899, Vol. 13, nr 2, s. 1039-1042Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    First-principles calculations are used to investigate the structure, electronic and optical properties of silicon nanocystals with chlorine-passivated surface. The nanocrystals considered were approximately spherical, with diameters between 1.5 and 3.0 nm. We show that the nanocrystals with chlorinated surface have a smaller bandgap, lower optical absorption threshold, and greater ionization energy and electron affinity than hydrogenated silicon nanocrystals of the same size

  • 271.
    Carvalho, Alexandra T.G.
    et al.
    Department of Physics, I3N, University of Aveiro, Campus Santiago.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Rayson, Mark
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, Patrick R.
    School of Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Increased electronic coupling in silicon nanocrystal networks doped with F4-TCNQ2013Inngår i: Journal of Nanoscience and Nanotechnology, ISSN 1533-4880, E-ISSN 1533-4899, Vol. 13, nr 2, s. 1035-1038Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The modification of the electronic structure of silicon nanocrystals using an organic dopant, 2,3,5,6- tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F 4-TCNQ), is investigated using first-principles calculations. It is shown that physisorbed F4-TCNQ molecules have the effect of oxidizing the nanocrystal, attracting the charge density towards the F 4-TCNQ-nanocrystal interface, and decreasing the excitation energy of the system. In periodic F4-TCNQ/nanocrystal superlattices, F 4-TCNQ is suggested to enhance exciton separation, and in the presence of free holes, to serve as a bridge for electron/hole transfer between adjacent nanocrystals.

  • 272.
    Carvalho, Alexandra
    et al.
    Department of Physics, I3N, University of Aveiro, Campus Santiago.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Barroso, Manuel
    Department of Physics, I3N, University of Aveiro, Campus Santiago.
    Rayson, Mark
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, Patrick
    Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    P-doping of Si nanoparticles: the effect of oxidation2012Inngår i: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 209, nr 10, s. 1847-1850Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The radial dependence of the formation energy of substitutional phosphorus in silicon nanoparticles covered by an amorphous oxide shell is analysed using local density functional theory calculations. It is found that P+ is more stable at the silicon core. This explains the experimental observation of segregation of phosphorus to the Si-rich regions in a material consisting of Si nanocrystals embedded in a SiO2 matrix [Perego et al., Nanotechnology 21, 025602 (2010)]. Formation energy of positively charged substitutional phosphorus in a 1.5 nm diameter Si nanoparticle covered by a ∼2 nm-thick amorphous SiO2 shell, as a function of its distance to the centre.

  • 273. Castagliola, Philippe
    et al.
    Maravelakis, P.
    Psarakis, S.
    Vännman, Kerstin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Monitoring capability indices using run rules2007Inngår i: Proceedings of International Conference on Industrial Engineering and Systems Management, ISEM 07, ISEM 07 , 2007Konferansepaper (Fagfellevurdert)
  • 274. Castagliola, Philippe
    et al.
    Maravelakis, P.
    University of the Aegean, Samos.
    Psarakis, S.
    Athens University of Economics and Business.
    Vännman, Kerstin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Monitoring capability indices using run rules2009Inngår i: Journal of Quality in Maintenance Engineering, ISSN 1355-2511, E-ISSN 1758-7832, Vol. 15, nr 4, s. 358-370Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    PurposeThe purpose of this paper is propose a methodology for monitoring industrial processes that cannot be stabilized, but are nevertheless capable. Design/methodology/approach The proposed procedure uses the C P (u,v) family of capability indices proposed by Vännman (including the indices C PK , C PM , C PMK ) combined with one-sided two-out-of-three and three-out-of-four run rules strategies. FindingsThis paper introduces a new strategy, where capability indices are monitored in place of the classical sample statistics like the mean, median, standard deviation or range. Practical implicationsWhen doing a capability analysis it is recommended to first check that the process is stable, e.g. by using control charts. However, there are occasions when a process cannot be stabilized, but is nevertheless capable. Then the classical control charts fail to efficiently monitor the process position and variability. The approach suggested in this paper overcomes this problem. Originality/valueThe experimental results presented in this paper demonstrate how the new proposed approach efficiently monitors capable processes by detecting decreases or increases of capability level.

  • 275. Castagliola, Philippe
    et al.
    Vännman, Kerstin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Average run length when monitoring capability indices using EWMA2008Inngår i: Quality and Reliability Engineering International, ISSN 0748-8017, E-ISSN 1099-1638, Vol. 24, nr 8, s. 941-955Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In order to monitor unstable but capable processes Castagliola and Vännman have recently suggested a procedure based on an EWMA approach, called EWMA capability chart, for monitoring Vännman's Cp(u,v)-family of capability indices and showed how their proposed approach efficiently monitors capable processes by detecting a decrease or increase in the capability level. The goal of this paper is to investigate the efficiency of this capability chart in terms of ARL. The procedure used for computing this ARL is presented and simple guidelines for obtaining approximations to the optimal EWMA parameters are proposed.

  • 276.
    Castagliola, Philippe
    et al.
    Université de Nantes and IRCCyN.
    Vännman, Kerstin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Monitoring capability indices using an EWMA approach2007Inngår i: Quality and Reliability Engineering International, ISSN 0748-8017, E-ISSN 1099-1638, Vol. 23, nr 7, s. 769-790Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    When performing a capability analysis it is recommended to first check that the process is stable, for example, by using control charts. However, there are occasions when a process cannot be stabilized, but it is nevertheless capable. Then the classical control charts fail to efficiently monitor the process position and variability. In this paper we propose a new strategy to solve this problem, where capability indices are monitored in place of the classical sample statistics such as the mean, median, standard deviation, or range. The proposed procedure uses the Cp(u,v) family of capability indices proposed by Vännman combined with a logarithmic transformation and an EWMA approach. One important property of the procedure presented here is that the control limits used for the monitoring of capability indices only depend on the capability level assumed for the process. The experimental results presented in this paper demonstrates how this new approach efficiently monitors capable processes by detecting changes in the capability level.

  • 277.
    Castagliola, Philippe
    et al.
    Université de Nantes.
    Vännman, Kerstin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Monitoring capability indices using EWMA2006Rapport (Annet vitenskapelig)
  • 278.
    Castagliola, Philippe
    et al.
    Université de Nantes and IRCCyN.
    Vännman, Kerstin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    The efficiency of the EWMA capability chart2007Inngår i: IEEE International Conference on Industrial Engineering and Engineering Management, 2007: IEEM 2007 ; 2 - 4 Dec. 2007, Singapore / [ed] Martin Helander, Piscataway, NJ: IEEE Communications Society, 2007, s. 1389-1393Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In order to monitor unstable but capable processes Castagliola & Vännman have recently suggested a procedure based on an EWMA approach, called EWMA capability chart, for monitoring Vännman's Cp(u, v)-family of capability indices and showed how their proposed approach efficiently monitors capable processes by detecting a decrease or increase of the capability level. The goal of this paper is to investigate the efficiency of this capability chart by computing optimal EWMA parameters yielding the smallest possible ARL's. The method for computing the ARL is explained and a table summarizing optimal values for the EWMA parameters (λ*,K*) is given for the Cpk chart.

  • 279.
    Cederwall, Krister
    et al.
    Luleå tekniska universitet.
    Vännman, Kerstin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Composite beams from a statistical point of view1982Rapport (Annet vitenskapelig)
  • 280.
    Chechkin, G. A.
    et al.
    Department of Differential Equations, Faculty of Mechanics and Mathematics, Moscow Lomonosov State University.
    Koroleva, Yulia O.
    Persson, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    On the precise asymptotics of the constant in Friedrich's inequality for functions vanishing on the part of the boundary with microinhomogeneous structure2007Inngår i: Journal of inequalities and applications (Print), ISSN 1025-5834, E-ISSN 1029-242XArtikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We construct the asymptotics of the sharp constant in the Friedrich-type inequality for functions, which vanish on the small part of the boundary Γ1ɛ. It is assumed that Γ1ɛ consists of (1/δ)n-1 pieces with diameter of order O(ɛδ). In addition, δ=δ(ɛ) and δ→0 as ɛ→0.

  • 281.
    Chechkin, G.A.
    et al.
    Department of Mechanics and Mathematics, Moscow State University.
    Koroleva, Yulia O.
    Meidell, Annette
    Narvik University College, 8505 Narvik, Norway.
    Persson, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    On the Friedrichs inequality in a domain perforated aperiodically along the boundary: Homogenization procedure. Asymptotics for parabolic problems2009Inngår i: Russian journal of mathematical physics, ISSN 1061-9208, E-ISSN 1555-6638, Vol. 16, nr 1, s. 1-16Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper is devoted to the asymptotic analysis of functions depending on a small parameter characterizing the microinhomogeneous structure of the domain on which the functions are defined. We derive the Friedrichs inequality for these functions and prove the convergence of solutions to corresponding problems posed in a domain perforated aperiodically along the boundary. Moreover, we use numerical simulation to illustrate the results.

  • 282.
    Chechkin, G.A.
    et al.
    Department of Differential Equations, Faculty of Mechanics and Mathematics, Moscow Lomonosov State University.
    Koroleva, Yulia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Persson, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Wall, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    On spectrum of the Laplacian in a circle perforated along the boundary: application to a Friedrichs-type inequality2011Rapport (Annet vitenskapelig)
  • 283.
    Chechkin, Gregory
    et al.
    Moscow Lomonosov State University.
    Koroleva, Yulia
    Persson, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Wall, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    A new weighted Friedrichs-type inequality for a perforated domain with a sharp constant2011Inngår i: Eurasian Mathematical Journal, ISSN 2077-9879, Vol. 2, nr 1, s. 81-103Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We derive a new three-dimensional Hardy-type inequality for a cube for the class of functions from the Sobolev space $H^1$ having zero trace on small holes distributed periodically along the boundary. The proof is based on a careful analysis of the asymptotic expansion of the first eigenvalue of a related spectral problem and the best constant of the corresponding Friedrichs-type inequality.

  • 284.
    Chechkin, Gregory
    et al.
    Department of Differential Equations, Faculty of Mechanics and Mathematics, Moscow Lomonosov State University.
    Koroleva, Yulia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Persson, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Wall, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    On spectrum of the Laplacian in a circle perforated along the boundary: Application to a Friedrichs-type inequality2011Inngår i: International Journal of Differential Equations, ISSN 1687-9643, E-ISSN 1687-9651, Vol. 2011, artikkel-id 619623Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper we construct and verify the asymptotic expansion for the spectrum of a boundary-value problem in a unit circle periodically perforated along the boundary. It is assumed that the size of perforation and the distance to the boundary of the circle are of the same smallness. As an application of the obtained results the asymptotic behavior of the best constant in a Friedrichs-type inequality is investigated.

  • 285.
    Choquard, Philippe
    et al.
    EPFL, Lausanne.
    Strömberg, Thomas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    A one-dimensional inviscid and compressible fluid in a harmonic potential well2007Inngår i: Acta Applicandae Mathematicae - An International Survey Journal on Applying Mathematics and Mathematical Applications, ISSN 0167-8019, E-ISSN 1572-9036, Vol. 99, nr 2, s. 161-183Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A Hamiltonian model is analyzed for a one-dimensional inviscid compressible fluid. The space-time evolution of the fluid is governed by the following system of the Hamilton-Jacobi and the continuity equations: S-t + 1/2(S-x(2) + omega(2)chi(2)) =0, S(x, 0) = S-0(x); rho(t) + (rho S-x)(x) =0, rho(x, 0) =rho(0)(x).Here S and rho designate the velocity potencial and the mass density, respectively. Unless S-0 is convex, shocks form and the velocity S (x) becomes discontinuous in {0 < omega t < pi/2}. It is demonstrated that there nevertheless exists a unique viscosity-measure solution (S,rho) when S-0 is globally Lipschitz continuous and locally semi-concave while rho(0) is a finite Borel measure. The structure of the velocity and the density is exhibited. For initial data correlated in a certain sense, a class of classical solutions (S,rho) is given. Negative time is also considered, and illustrating examples are given.

  • 286. Ciesielska, Danuta
    et al.
    Maligranda, Lech
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Alfred Rosenblatt (1880-1947)2014Inngår i: Wiadomosci Matematyczne, ISSN 2080-5519, Vol. 50, nr 2, s. 221-259Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Summary. Life of Alfred Rosenblatt (1880-1947) is precisely discribed. We tried to bring the Polish reader forgotten figure of the Krakow mathematics. We have gathered all the information related to his life, his work and achievements in mathematics and in applications of mathematics. We greached also written information about it in Spanish. Rosenblatt has published almostthree hundred scientific papers in many areas of mathematics and its applications. In addition, he participated in four International Congresses of Mathematicians in Cambridge (1912), Strasbourg (1920), Bologna (1928) and Zurich (1932). Streszczenie. Zycie Alfreda Rosenblatta (1880-1947) zostało dokładnie opisane. Staralismy sie przyblizyc polskiemu czytelnikowi sylwetke tego zapomnianego krakowskiego matematyka.Zebralismy wszelkie informacje zwiazane z jego zyciem, jego pracami i osiagnieciami wmatematyce oraz w zastosowaniach matematyki. Dotarlismy rowniez do informacji pisanych o nim po hiszpansku. Rosenblatt opublikowal prawie trzysta prac naukowych w wieludziedzinach matematyki i jej zastosowan. Ponadto uczestniczyl w czterech Miedzynarodowych Kongresach Matematykow w Cambridge (1912), Strasburgu (1920), Bolonii (1928) i Zurichu (1932).

  • 287. Ciesielska, Danuta
    et al.
    Maligranda, Lech
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Alfred Rosenblatt (1880-1947): Publikacje, odczyty i wykłady2014Inngår i: Antiquitates Mathematicae, ISSN 1898-5203, Vol. 8, nr 1, s. 3-45Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of the paper is to present scientific and educationalachievements of Alfred Rosenblatt (1880-1947). We have collected thefirst complete list of scientific papers and books by Rosenblatt. Thelist is divided into the following parts: textbooks and monographs, scientificarticles in the field of mathematics and its applications, astronomy,history of mathematics and reviews, translations and other. Frompublished and unpublished sources we collected information about hislectures and short presentations on conferences, among others on InternationalCongresses of Mathematicians, Congresses of Mathematiciansof Slavic Countries, Polish Mathematical Society Meetings and others.Complete list of Rosenblatt’s academic lectures at the Jagiellonian Universityand available information about lectures at the National Universityof San Marcos in Lima are collected. A very short biographyof Rosenblatt and overview of his scientific results in algebraic geometry,differential equations, analytic function, calculus of variations,probability theory and statistics, and application of mathematics inhydrodynamic is presented.Streszczenie Celem artykułu jest zaprezentowanie dorobku naukowegoi dydaktycznego Alfreda Rosenblatta (1880-1947). Zgromadzilsmypierwszy kompletny spis jego artykułów i ksiazek naukowych,z podziałem na: podreczniki i monografie, artykuły naukowe z zakresumatematyki i jej zastosowan, astronomii, historii matematyki w tymbiografie oraz recenzje, tłumaczenia i inne. Zebralismy w publikowanychi niepublikowanych zródłach informacje o jego odczytach, w tymo odczytach i komunikatach na Miedzynarodowych Kongresach Matematyków,wystapieniach na Kongresach Matematyków Krajów Słowianskich,Zjazdach PTM i innych. Przedstawilismy kompletny spiswykładów Rosenblatta na Uniwersytecie Jagiellonskim oraz dostepneinformacje o wykładach na Uniwersytecie Swietego Marka w Limie. Ponadtow artykule znajduje sie krótki biogram A. Rosenblatta i krótkieomówienie jego wyników naukowych z geometrii algebraicznej, teoriirównan rózniczkowych, funkcji analitycznych, rachunku wariacyjnego,szeregów, rachunku prawdopodobienstwa i statystyki oraz zastosowanmatematyki w hydrodynamice

  • 288.
    Cizmesija, Alexandra
    et al.
    Department of Mathematics, University of Zagreb.
    Pecaric, Josip
    Faculty of Textile Technology, University of Zagreb.
    Persson, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    On strengthened Hardy and Pólya–Knopp's inequalities2003Inngår i: Journal of Approximation Theory, ISSN 0021-9045, E-ISSN 1096-0430, Vol. 125, nr 1, s. 74-84Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper we prove a strengthened general inequality of the Hardy–Knopp type and also derive its dual inequality. Furthermore, we apply the obtained results to unify the strengthened classical Hardy and Pólya–Knopp's inequalities deriving them as special cases of the obtained general relations. We discuss Pólya–Knopp's inequality, compare it with Levin–Cochran–Lee's inequalities and point out that these results are mutually equivalent. Finally, we also point out a reversed Pólya–Knopp type inequality.

  • 289.
    Cizmesija, Alexandra
    et al.
    Department of Mathematics, University of Zagreb.
    Pecaric, Josip
    Faculty of Textile Technology, University of Zagreb.
    Persson, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    On strengthened weighted Carleman´s inequality2003Inngår i: Bulletin of the Australian Mathematical Society, ISSN 0004-9727, E-ISSN 1755-1633, Vol. 68, nr 3, s. 481-490Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper we prove a new refinement of the weighted arithmetic-geometric mean inequality and apply this result in obtaining a sharpened version of the weighted Carleman's inequality

  • 290. Cizmesija, Alexandra
    et al.
    Persson, Lars-ErikLuleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Mathematical inequalities and applications: proceedings of the conference in honour of professor Josip Pecaric, Trogir, Croatia, June 8-14, 20082009Collection/Antologi (Annet vitenskapelig)
  • 291.
    Cizmesija, Alexandra
    et al.
    Department of Mathematics, University of Zagreb.
    Persson, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Wedestig, Anna
    Weighted integral inequalities for Hardy and geometric mean operators with kernals over cones in Rn2005Inngår i: Italian Journal of Pure and Applied Mathematics, ISSN 1126-8042, nr 18, s. 89-118Artikkel i tidsskrift (Fagfellevurdert)
  • 292.
    Cobos, Fernando
    et al.
    Departamento de Análisis Matémático, Facultad de Matemáticas, Universidad Complutense de Madrid.
    Peetre, Jaak
    Matematiska institutionen, Lunds universitet.
    Persson, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    On the connection between real and complex interpolation of quasi-banach spaces1998Inngår i: Bulletin des Sciences Mathématiques, ISSN 0007-4497, E-ISSN 1952-4773, Vol. 122, nr 1, s. 17-37Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We describe a new approach to interpolate by the complex method quasi-Banach couples formed by real-intermediate spaces. End-point cases are also considered, and applications are given to function spaces and to operator spaces.

  • 293.
    Cobos, Fernando
    et al.
    Department of Mathematical Analysis, Faculty of Mathematics, Universidad Complutense de Madrid.
    Persson, Lars-Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Real interpolation of compact operators between quasi-Banach spaces1998Inngår i: Mathematica Scandinavica, ISSN 0025-5521, E-ISSN 1903-1807, Vol. 82, nr 1, s. 138-160Artikkel i tidsskrift (Fagfellevurdert)
  • 294.
    Coomer, B.J.
    et al.
    School of Physics, University of Exeter.
    Goss, J.P.
    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.
    Identification of the tetra-interstitial in silicon2001Inngår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 13, nr 1, s. L1-L7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    First-principles computational methods are employed to investigate the structural, vibrational, optical and electronic properties of the self-interstitial aggregate, I4 in silicon. We find the defect to be electrically active and identify it with the B3 EPR centre. We also show that its properties are consistent with DLTS and optical spectra observed following implantation of silicon.

  • 295.
    Coomer, B.J.
    et al.
    School of Physics, University of Exeter.
    Goss, J.P.
    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.
    Interstitial aggregates and a new model for the I1/W optical centre in silicon1999Inngår i: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 273-274, s. 505-508Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The properties of di-interstitial (I2), tri-interstitial (I3) and tetra-interstitial (I4) structures in silicon were studied by employing first principles local-density-functional (LDF) theory. A tri-interstitial defect can account for many of the fundamental properties of the I1/W-optical center which is observed in irradiated, annealed silicon. Energy comparisons between di-interstitial defects reveal four low-energy structures within 0.5 eV of each other.

  • 296.
    Coomer, B.J.
    et al.
    University of Exeter.
    Leary, P.
    University of Exeter.
    Budde, M.
    Aarhus University.
    Nielsen, B. Bech
    Aarhus University.
    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.
    Vacancy-hydrogen complexes in germanium1998Inngår i: E-MRS Meeting, European Materials Research Society , 1998Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Local-density-functional pseudopotential theory is used to investigate the structural, electronic and vibrational properties of vacancy-hydrogen complexes in germanium. The results are compared with recent infrared absorption data from proton and deuteron implanted Ge. The acceptor and donor levels of the VH defects are derived semi-empirically from the relaxed structures

  • 297.
    Coomer, B.J.
    et al.
    Department of Physics, University of Exeter.
    Leary, P.
    Department of Physics, University of Exeter.
    Budde, M.
    Institute of Physics and Astronomy, University of Aarhus.
    Nielsen, B. Bech
    Institute of Physics and Astronomy, University of Aarhus.
    Jones, R.
    Department 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.
    Vacancy-hydrogen complexes in germanium1999Inngår i: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 58, nr 1-2, s. 36-38Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Local-density-functional pseudopotential theory is used to investigate the structural, electronic and vibrational properties of vacancy-hydrogen complexes in germanium. The results are compared with recent infrared absorption data from proton and deuteron implanted Ge. The acceptor and donor levels of the VHn defects are derived semi-empirically from the relaxed structures

  • 298.
    Coomer, B.J.
    et al.
    School of Physics, University of Exeter.
    Resende, A.
    School of Physics, University of Exeter.
    Goss, J.P.
    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.
    The divacancy in silicon and diamond1999Inngår i: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 273-274, s. 520-523Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    First-principles studies of the divacancy (V2) in both silicon and diamond are reported. We demonstrate that the contrasting experimental spin-density localisation of both systems can be explained through the one-electron pictures arising from opposing distortions

  • 299.
    Coutinho, J.
    et al.
    Department of Physics, University of Aveiro.
    Andersen, O.
    Center for Electronic Materials, Devices and Nanostructures, University of Manchester.
    Dobaczewski, L.
    Institute of Physics, Polish Academy of Sciences.
    Nielsen, K. Bonde
    Institute of Physics and Astronomy, University of Aarhus.
    Peaker, A.R.
    Center for Electronic Materials, Devices and Nanostructures, University of Manchester.
    Jones, R.
    School of Physics, University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Effect of stress on the energy levels of the vacancy-oxygen-hydrogen complex in Si2003Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 68, nr 18, s. 184106-1Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The piezospectroscopic properties of the VOH defect in Si are found using stress Laplace deep level transient spectroscopy (DLTS) and are compared with local density-functional calculations of (i) the acceptor level and its shift under stress, and (ii) the alignment of the neutral center under stress. The theory is able to account for two acceptor levels observed for 〈100〉, 〈111〉, and 〈110〉 stress even though additional splitting is expected for a defect with static C1h symmetry. This is related to (i) a rapid reorientation of the H atom within the defect at temperatures at which the DLTS experiments are carried out, and (ii) the small effect of stress on two orientations of the defect under 〈110〉 stress. The theory is also able to give a quantitative account of the alignment of the center. The effect of stress on the reorientation barrier of the defect is also investigated. The reorientation barrier of the defect in its positive charge state is found theoretically to be very small, consistent with the lack of any splitting in the donor level under stress.

  • 300.
    Coutinho, J.
    et al.
    Department of Physics, I3N, University of Aveiro, Campus Santiago.
    Janke, C.
    School of Physics, University of Exeter.
    Carvalho, A.
    School of Physics, University of Exeter.
    Torres, V.J.B.
    Department of Physics, I3N, University of Aveiro, Campus Santiago.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Jones, R.
    School of Physics, University of Exeter.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Strong compensation of n-type Ge via formation of donor-vacancy complexes2007Inngår i: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 401-402, s. 179-183Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Vacancies and interstitials in semiconductors play a fundamental role in both high-temperature diffusion and low-temperature radiation and implantation damage. In Ge, a serious contender material for high-speed electronics applications, vacancies have historically been believed to dominate most diffusion related phenomena such as self-diffusivity or impurity migration. This is to be contrasted with silicon, where self-interstitials also play decisive roles, despite the similarities in the chemical nature of both materials. We report on density functional calculations of the formation and properties of vacancy-donor complexes in germanium. We predict that most vacancy-donor aggregates are deep acceptors, and together with their high solubilities, we conclude that they strongly contribute for inhibiting donor activation levels in germanium

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