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  • 201. Latham, Chris
    et al.
    Ganchenkova, M.
    Laboratory of Physics, Helsinki University of Technology.
    Nieminen, R.M.
    Laboratory of Physics, Helsinki University of Technology.
    Nicolaysen, S.
    Department of Physics, University of Oslo.
    Alatalo, M.
    Department of Electrical Engineering, Lappeenranta University of Technology.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Electronic structure calculations for substitutional copper and monovacancies in silicon2006Inngår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 2006, nr T126, s. 61-64Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two different computer program packages based on the self-consistent local-spin-density approximation-aimpro and vasp-are employed in this study of substitutional copper CuSi and monovacancies VSi in silicon, including the effects of their charge state. The programs differ in the types of basis sets and pseudopotentials they use, each with their own relative merits, while being similar in overall quality. This approach aims to reduce uncertainty in the results, particularly for small or subtle effects, where the risk is greatest that the conclusions are affected by artifacts specific to a particular implementation. The electronic structures of the two defects are closely related, hence they are expected to behave in a similar manner. For both defects structural distortions resulting in lower point group symmetries than Td (the highest possible) are found. This is in good agreement with the results of previous studies of VSi. Much less is known about symmetry-lowering effects for CuSi; however, the electronic levels of CuSi have been measured accurately, while those for VSi are less accessible. Calculating them is a challenging task for theory. The strategy we adopt, based purely on comparing total energies of supercells in different charge states, with and without model defects, reproduces the three known levels for CuSi reasonably well. Satisfactory results are also obtained for VSi in so far as can be judged for this more complex case.

  • 202.
    Latham, Chris
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Jones, R.
    School of Physics, University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Nieminen, R.M.
    Laboratory of Physics, Helsinki University of Technology.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Calculated properties of nitrogen-vacancy complexes in beryllium- and magnesium-doped GaN2003Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 68, nr 20, s. 205209-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The properties of defect complexes consisting of a nitrogen vacancy with a substitutional beryllium or magnesium atom on neighboring lattice sites in hexagonal GaN are calculated using the AIMPRO local-density-functional theory method. Both types of defects VN-BeGa and VN-MgGa are bound with respect to their isolated constituents. They do not appear to have any electronic levels in the bandgap, and are expected to be neutral defects. Important structural differences are found. In its minimum energy configuration, the Be atom in the VN-BeGa complex lies nearly in the same plane as the three equivalent N atoms nearest to it. Thus, it has shorter Be-N bonds than the Ga-N distance in the bulk crystal, while the Mg atom in the VN-MgGa complex occupies a position closer the lattice site of the Ga atom it replaces. Hence, the VN-BeGa complex has a larger open volume than the VN-MgGa complex. This is consistent with positron annihilation experiments [Saarinen et al., J. Cryst. Growth 246, 281 (2002); Hautakangas et al., Phys. Rev. Lett. 90, 137402 (2003)]. The frequency of the highest local vibrational mode of the VN-BeGa center is calculated to be within 3-4 % of an infrared absorption line detected in Be-doped GaN

  • 203. Latham, Chris
    et al.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Louchet, F.
    LGGE, Saint Martin d'Hères.
    A pseudopotential density functional theory study of native defects and boron impurities in FeAl2006Inngår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 18, nr 39, s. 8859-8876Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structures and energies of point defects and point defect complexes in B 2 iron aluminium FeAl are calculated using a local density functional theory based method with large supercells. Particular emphasis is given to pseudopotential quality, choice of chemical potentials used to calculate defect formation energies, and how these are affected by magnetism. Both purely native defects and those containing boron atoms are considered. It is found that the relative stabilities of isolated point defects versus defect complexes depends on whether the material contains excess iron or aluminium. The situation in material containing boron is further complicated by the existence of iron borides in more than one form. We propose that the interaction between point defects, dislocations, and antiphase boundaries, where the local atomic environment has some similarities with antisite defects, also depends on the alloy composition. It is likely that these interactions are part of the underlying mechanism responsible for the unusual mechanical properties of iron aluminides.

  • 204.
    Latham, Christopher D.
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Heggie, Malcolm I.
    University of Surrey.
    Alatalo, Matti
    Lappeenranta University of Technology.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, Patrick R.
    University of Newcastle Upon Tyne.
    The contribution made by lattice vacancies to the Wigner effect in radiation-damaged graphite2013Inngår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 25, nr 13, artikkel-id 135403Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Models for radiation damage in graphite are reviewed and compared, leading to a re-examination of the contribution made by vacancies to annealing processes. A method based on density functional theory, using large supercells with orthorhombic and hexagonal symmetry, is employed to calculate properties and behaviour of lattice vacancies and displacement defects. It is concluded that annihilation of intimate Frenkel defects marks the onset of recovery in electrical resistivity, which occurs when the temperature exceeds about 160 K. Migration of isolated monovacancies is estimated to have an activation energy Ea ≈ 1.1 eV. Coalescence into divacancy defects occurs in several stages, with different barriers at each stage, depending on the path. The formation of pairs ultimately yields up to 8.9 eV energy, which is nearly 1.0 eV more than the formation energy for an isolated monovacancy. Processes resulting in vacancy coalescence and annihilation appear to be responsible for the main Wigner energy release peak in radiation-damaged graphite, occurring at about 475 K.

  • 205.
    Lavrov, E V
    et al.
    University of Aarhus.
    Nielsen, B Bech
    University of Aarhus.
    Byberg, J R
    University of Aarhus.
    Hourahine, B
    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.
    Local vibrational modes of two neighboring substitutional carbon atoms in silicon2000Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 62, nr 1, s. 158-165Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Infrared absorption measurements on n-type silicon doped with carbon and irradiated with electrons at room temperature have revealed new absorption lines at 527.4 and 748.7 cm-1, which originate from the same defect. The 748.7-cm-1 line is observed only when the sample is cooled in the dark and the spectrum is measured through a low-pass filter with cutoff frequency below 6000 cm-1. Light with frequency above 6000 cm-1 removes this line and generates the 527.4-cm-1 line. Comparison with spectra recorded on irradiated silicon doped with 13C shows that the two lines represent local vibrational modes of carbon. The annealing behavior of the 748.7-cm-1 line is identical to that of the EPR signal originating from the negative charge state of two adjacent substitutional carbon atoms (Cs-Cs)-. The 527.4- and 748.7-cm-1 lines are ascribed to the E modes of Cs-Cs in the neutral and negative charge states, respectively. The structure and local vibrational modes of (Cs-Cs)0 and (Cs-Cs)- have been calculated by ab initio local density functional theory. The calculated structures agree qualitatively with those obtained previously by Hartree-Fock methods, but the calculated Si-C and C-C bond lengths differ somewhat. The calculated local mode frequencies are in good agreement with those observed. The formation of Cs-Cs has also been investigated. It is suggested that the center is formed when a vacancy is trapped by the metastable substitutional carbon-interstitial carbon center, Cs-Ci.

  • 206.
    Lavrov, E.V.
    et al.
    University of Aarhus.
    Hoffmann, L.
    University of Aarhus.
    Nielsen, B. Bech
    University of Aarhus.
    Hourahine, B.
    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.
    Combined infrared absorption and modeling study of a dicarbon-dihydrogen defect in silicon2000Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 62, nr 19, s. 12859-12867Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Crystalline silicon samples doped with carbon were irradiated with electrons and subsequently implanted with protons. Infrared-absorption measurements revealed local modes of hydrogen and carbon at 2967.4, 911.7, and 654.7 cm-1, which originate from the same defect. Measurements on samples codoped with different carbon and hydrogen isotopes showed that the defect contains two equivalent carbon and two equivalent hydrogen atoms. From uniaxial stress measurements, the defect is found to display trigonal symmetry. Ab initio local-density-functional theory was applied to calculate the structure and local vibrational modes of defects with pairs of equivalent carbon and hydrogen atoms. Based on these results, the observed local modes are ascribed to a defect with two adjacent substitutional carbon atoms, each of which binds a hydrogen atom located between the carbon atoms.

  • 207.
    Leary, P.
    et al.
    University of Exeter.
    Jones, R.
    University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Interaction of hydrogen with substitutional and interstitial carbon defects in silicon1998Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 57, nr 7, s. 3887-3889Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An ab initio cluster method is used to investigate substitutional, Cs, and interstitial, Ci, carbon defects in silicon complexed with hydrogen. We find that the binding energy of neutral H with Cs is 1.01 eV, and that the defect is bistable. In the positive and neutral charge states H lies near the center of a C-Si bond, and is antibonded to C in the negative charge state. A second H atom can be trapped in a H2* defect. H forms stronger bonds with interstitial Ci. In the Ci-H defect, the binding energy of H is 2.8 eV, and two low-energy structures have almost degenerate energies. These consist of a bond-centered Si-(Ci-H)-Si defect and a 〈100〉-oriented Ci-Si split interstitial with H bonded to Ci. The calculated barrier for conversion between the two stable structures is very low, ∼0.3 eV, implying that the defect migrates rapidly, and readily reacts with other defects or impurities present. Two possible reactions are considered: the first is with another H and the second with Cs. The defect is completely passivated in the former while the stable form of the latter consists of a 〈100〉 C-C dicarbon interstitial, where one radical is passivated by H. The calculated symmetry and the local vibrational modes are in excellent agreement with those experimentally observed for the T photoluminescent center. Finally, a further reaction involving the T center and a second H atom is considered, and is found to lead to the elimination of electrical activity.

  • 208.
    Leary, P
    et al.
    University of Exeter.
    Jones, R
    University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Torres, V J B
    Universidade de Aveiro.
    Dynamic properties of interstitial carbon and carbon-carbon pair defects in silicon1997Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 55, nr 4, s. 2188-2194Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Interstitial carbon, Ci, defects in Si exhibit a number of unexplained features. The Ci defect in the neutral charge state gives rise to two almost degenerate vibrational modes at 920 and 931 cm-1 whose 2:1 absorption intensity ratio naturally suggests a trigonal defect in conflict with uniaxial stress measurements. The dicarbon, Cs-Ci, defect is bistable, and the energy difference between its A and B forms is surprisingly small even though the bonding is very different. In the B form appropriate to the neutral charge state, a silicon interstitial is believed to be located near a bond-centered site between two Cs atoms. This must give rise to vibrational modes which involve the motion of both C atoms in apparent conflict with the results of photoluminescence experiments. We use an ab initio local density functional cluster method, AIMPRO, to calculate the structure and vibrational modes of these defects and find that the ratio of the absorption intensities of the local modes of Ci is in reasonable agreement with experiment even though the structure of the defect is not trigonal. We also show that modes in the vicinity of those detected by photoluminescence for the B form of the dicarbon center involve independent movements of the two C atoms. Finally, the trends in the relative energies of the A and B forms in three charge states are investigated.

  • 209.
    Leary, P.
    et al.
    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.
    Jones, R.
    Department of Physics, University of Exeter.
    Interstitial carbon-hydrogen defects in silicon1997Inngår i: Defects in semiconductors: : proceedings of the 19th International Conference on Defects in Semiconductors, Aveiro, Portugal, July 1997 / [ed] Gordon Davies, Trans Tech Publications Inc., 1997, s. 265-270Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Interstitial carbon, in contrast with substitutional carbon, forms defects with hydrogen which are both electrically active and stable to high temperatures. Ab initio cluster calculations show that the most primitive defect, CiH, diffuses very rapidly and is expected to complex with many other impurities notably C, H and O. We describe here the structure and properties of Ci,nHm defects where n and m are less than 3. The most stable defects of the type CiCsHm have very different structures when m = 0 and when m > 0. In the former case, the C-C bond is metastable and only C-Si-C bonds are formed. However in the second case, the presence of a H atom stabilises the C-C bond. These results are supported by experiment. We show that the vibrational modes of the Cs-CiH defect are close to those observed for the T-photoluminescent centre and this defect is passivated when complexed with a further H atom. This defect then provides the first example of a fully characterised carbon centre containing a C-C bond.

  • 210.
    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

  • 211.
    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.
    Interaction of vacancies with partial dislocations in silicon1997Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 56, nr 20, s. R12706-R12709Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The interaction of vacancies with 30° and 90° partial dislocations in silicon is examined. In particular, the structures and binding energies are calculated using hydrogen-terminated clusters and local density-functional theory. Moreover the electronic structure is determined using supercells containing dislocation dipoles. Vacancies are found to have binding energies of approximately 2.0 eV and 0.9 eV to 90° and 30° partials, respectively. The elastic strain field of the partials makes the fourfold vacancy reconstruct, which essentially clears the fundamental gap

  • 212.
    Leigh, R.S.
    et al.
    J. J. Thomson Physical Laboratory, University of Reading.
    Sangster, J.L.
    J. J. Thomson Physical Laboratory, University of Reading.
    Newman, R.C.
    Centre for Electronic Materials and Devices, The Blackett Laboratory, Department of Physics, Imperial College, London.
    Goss, J.P.
    School of Physics, University of Exeter.
    Jones, R.
    School of Physics, University of Exeter.
    Torres, V.J.B.
    Departamento de Fisica, Universidade de Aveiro.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P.R.
    Department of Physics, University of Newcastle.
    Vibrational modes of sulfur defects in GaP2003Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 68, nr 3, s. 33304-1Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    First principles calculations carried out on GaP containing sulfur donors 32SP (95%) and34SP (5%) show that both the neutral and ionized donors are located on substitutional sites and have weak S-Ga bonds. For the sulfur impurity in its positive charge state the calculations give gap modes for 32S and34S at frequencies close to those found experimentally. Modes within the gap are also predicted for neutral sulfur at frequencies within a few cm-1 of their charged-state counterparts. However, the SP0 donor has a very low apparent charge (i.e. oscillator strength), its calculated integrated absorption cross section being only ∼3% of that for the SP+ defect. These results support an earlier explanation of the failure to detect gap modes from SP0 in infrared measurements. Calculated and observed apparent charges for the SP+ donor are compared, and the importance of taking due account of the different geometries that apply to the theoretical calculations and infrared experiments is emphasized.

  • 213.
    Lindefelt, U.
    et al.
    Department of Physics & Measurement Technology, Linköping University.
    Iwata, H.
    Department of Physics & Measurement Technology, Linköping University.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P.R.
    Department of Physics, University of Newcastle.
    Insight into the degradation phenomenon in SiC devices from ab initio calculations of the electronic structure of single and multiple stacking faults2003Inngår i: Silicon carbide and related materials: ECSCRM 2002 : proceedings of the 4th European Conference on Silicon Carbide and Related Materials, September 2-5, 2002, Linköping, Sweden / [ed] Peder Bergman; Erik Janzén, Uetikon-Zuerich: Trans Tech Publications Inc., 2003, s. 907-912Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Soon after the discovery of the problem with electrical degradation of bipolar SiC devices, we started to perform ab initio calculations in order to evaluate the hypothesis that the degradation is caused by the expansion of stacking faults (SF) created by the propagation of partial dislocations in the (0001) basal plane. These investigations have created a wealth of important information, and constitutes a major part of our present understanding of the degradation phenomenon. Salient features are: (1) In 3C-, 4H-, 6H-, and 15R-SiC there are one, two, three, and five structurally different SFs, respectively, with different properties. (2) In 4H-, 6H- and 15R-SiC two of the different types of SFs give rise to states with energies around 0.2 eV (0.1-0.15 eV in 15R) below the conduction band. These states extend along the SF plane but are strongly localized to within around 10 Å in the direction perpendicular to the SF plane. (3) These states and their one-dimensional confinement can be interpreted in terms of a quantum-well whose depth is determined by the conduction band offset between the relevant polytype and 3C-SiC. (4) Very shallow, localized (gap) states appear in some cases and can be related to the change in electronic polarization induced by the SF. (5) Calculated SF energies (SFE) are very close to both measured values and to the predictions of the simpler ANNNI (axial next nearest neighbour Ising) model. (6) The SFE in 3C-SiC is negative. (7) In 6H-SiC, the SFE for one of the SFs is considerably larger than for the other two. (8) In 15R-SiC, the SFEs for two of the SFs are almost zero. (9) The localized states described in item 2 are, beyond reasonable doubt, responsible for the electrical degradation. We have also investigated the electronic properties of two (2SF), three (3SF), and four SFs (4SF) in neighbouring planes in 4H-SiC, leading to thin 3C-like inclusions. Especially double SFs (2SF) have been observed, and may also be present in degraded devices. For these systems, some salient features are: (1) Like in the case of an isolated SF, localized gap states in the upper part of the band gap appear. The number of bound states, their energies and wave function localizations are well described by a quantum-well model. (2) The electronic polarization of the host crystal gives rise to a clear displacement of the wave functions for the localized gap states. (3) The SFE for a second SF in the presence of an already existing one (i.e., the change in total energy in going from 1SF to 2SF) is around a factor four less than the SFE for the first SF. This is compatible with recent experimental observations

  • 214.
    Lindefelt, Ulf
    et al.
    Department of Physics and Measurement Technology, Linköping University.
    Iwata, Hisaomi
    Department of Physics and Measurement Technology, Linköping University.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, Patrick R.
    Department of Physics, University of Newcastle.
    Stacking faults in 3C-, 4H-, and 6H-SiC polytypes investigated by an ab initio supercell method2003Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, s. 155204-1Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recent attempts to make SiC diodes have revealed a problem with stacking fault expansion in the material, leading to unstable devices. In this paper, we present detailed results from a density-functional supercell calculation on the electronic structure of stacking faults which result from glide of Shockley partials in 3C-, 4H- and 6H-SiC. It was found [Phys. Rev. B 65, 033203 (2002)] that both types of stacking faults in 4H-SiC and two types of stacking faults in 6H-SiC give rise to band states, which are strongly localized (confined within around 10 Å) in the direction orthogonal to the stacking fault plane. Based on estimates of the band offsets between different polytypes and a simple quantum-well theory, we show that it is possible to interpret this one-dimensional localization as a quantum-well confinement effect. We also find that the third type of stacking fault in 6H-SiC and the only stacking fault in 3C-SiC do not give rise to states clearly separated from the band edges, but instead give rise to rather strongly localized band states with energies very close to the band edges. We argue that these localized near band edge states are created by stacking fault induced changes in the dipole moment associated with the hexagonal symmetry. In addition, we have also calculated the stacking fault energies, using both the supercell method and the simpler ANNNI (axial next nearest-neighbor Ising) model. Both theories agree well with the low stacking fault energies found experimentally.

  • 215.
    Löfgren, Robin
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Pawar, Ravinder
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Larsson, Andreas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Charged dopants in neutral supercells through substitutional donor (acceptor): nitrogen donor charging of the nitrogen-vacancy center in diamond2018Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 20, artikkel-id 023002Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Charged defects are traditionally computed by adding (subtracting) electrons for negative (positive) impurities. When using periodic boundary conditions this results in artificially charged supercells that also require a compensating background charge of the opposite sign, which makes slab supercells problematic because of an arbitrary dependence on the vacuum thickness. In this work, we test the method of using neutral supercells through the use of a substitutional electron donor (acceptor) to describe charged systems. We use density functional theory (DFT) to compare the effects of charging the well-studied NV-center in diamond by a substitutional donor nitrogen. We investigate the influence of the donor-N on the NV-center properties as a function of the distance between them, and find that they converge toward those obtained when adding an electron. We analyze the spin density and conclude that the donor-N has a zero magnetic moment, and thus, will not be seen in electron spin resonance. We validate our DFT energies through comparison to GW simulations. Charging the NV-center with a substitutional donor-N enables accurate calculations of slabs, without the ambiguity of using charged supercells. Implantation of donor-N atoms opens up the possibility to engineer NV-centers with the desired charge state for future ICT and sensor applications.

  • 216.
    Löfgren, Robin
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Pawar, Ravinder
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Larsson, Andreas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Density functional theory calculations on the diamond nitrogen-vacancy center2015Konferansepaper (Annet vitenskapelig)
  • 217.
    Löfgren, Robin
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Pawar, Ravinder
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Larsson, Andreas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    The bulk conversion depth of the NV-center in diamond: computing a charged defect in a neutral slab2019Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 21, artikkel-id 053037Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The negatively charged nitrogen vacancy (NV-) center in diamond has properties that make it a promising candidate for applications such as a qubit in room temperature quantum computing, single-molecule photoluminescence and NMR sensor, and as a single photon source for quantum cryptography. For many of its uses it is desirable to have the NV-center close to the diamond surface. In this work, we use density functional theory simulations to investigate how the distance of the NV- center to a surface, and its orientation, affect its properties, including the zero-phonon-line. We study the three technologically important surfaces terminated with fluorine, oxygen/hydroxyl and nitrogen. Since the NV-center is charged it requires special measures to simulate within a slab-model. We use the recently proposed charging with a substitutional donor in the diamond lattice resulting in a neutral super-cell, which provides very satisfactory results. We have found that the NV-centers properties converge to bulk values already at 5 angstrom depth.

  • 218.
    Markevich, A.
    et al.
    College of Engineering, Mathematics and Physical Sciences, University of Exeter.
    Jones, R.
    College of Engineering, Mathematics and Physical Sciences, University of Exeter.
    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.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    First-principles study of hydrogen and fluorine intercalation into graphene-SiC(0001) interface2012Inngår 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]

    The properties of epitaxial graphene on SiC substrates can be modified by intercalation of different atomic species. In this work, mechanisms of hydrogen intercalation into the graphene-SiC(0001) interface, and properties of hydrogen and fluorine intercalated structures have been studied with the use of density functional theory. Our calculations show that the intercalation of hydrogen and fluorine into the interface is energetically favorable. Energy barriers for diffusion of atomic and molecular hydrogen through the interface graphene layer with no defects and graphene layers containing Stone-Wales defect or two- and four-vacancy clusters have been calculated. It is argued that diffusion of hydrogen towards the SiC surface occurs through the hollow defects in the interface graphene layer. It is further shown that hydrogen easily migrates between the graphene layer and the SiC substrate and passivates the surface Si bonds, thus causing the graphene layer decoupling. According to the band structure calculations the graphene layer decoupled from the SiC(0001) surface by hydrogen intercalation is undoped, while that obtained by the fluorine intercalation is p-type doped.

  • 219.
    Markevich, A.V..
    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.
    School of Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    First principles study of hydrogen-induced decoupling of epitaxial graphene from SiC substrates2011Inngår i: Physics, Chemistry and Applications of Nonostructures: Proceedings of the International Conference Nanomeeting-2011 : reviews and short notes : Minsk, Belarus, 24-27 May 2011 / [ed] Victor E. Borisenko, Singapore: World Scientific Publishing Co Pte Ltd , 2011, s. 311-314Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Density functional theory calculations have been used to investigate possible mechanisms of hydrogen-induced decoupling of graphene from SiC(0001). The results suggest that hydrogen atoms reach SiC surface through extended defects in graphene layers and then migrate and passivate bonds on the SiC surface

  • 220.
    Markevich, V P
    et al.
    Institute of Solid State and Semiconductor Physics, Minsk.
    Murin, L I
    Institute of Solid State and Semiconductor Physics, Minsk.
    Suezawa, M
    Tohoku University.
    Lindström, J L
    University of Lund.
    Coutinho, J
    University of Exeter.
    Jones, R
    University of Exeter.
    Briddon, P R
    University of Newcastle Upon Tyne.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Observation and theory of the V-O-H2 complex in silicon2000Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 61, nr 19, s. 12964-12969Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The interaction of hydrogen with radiation-induced defects (RD's) in Czochralski-grown silicon crystals has been studied by infrared-absorption spectroscopy and ab initio modeling. Hydrogen and/or deuterium was introduced into the crystals by indiffusion from H2 (D2) gas at 1200-1300 °C. The samples were subsequently irradiated with fast electrons (E=2-4 MeV) and annealed in the temperature range of 100-600 °C. The centers produced by the irradiation were the same in both the untreated and treated cases, namely the A-center, Ci-Oi complex, and divacancy. A heat treatment of the H-treated samples resulted in the enhanced loss of these centers and the formation of centers containing hydrogen. The disappearance of the A centers in the temperature range of 100-150 °C is correlated with the appearance of three local vibrational modes (LVM's) at 943.5, 2126.4, and 2151.5 cm-1. The isotopic shifts of these lines were obtained from measurements on the samples doped with hydrogen and deuterium. The lines are identified as related to stretching vibrational modes of a complex that consists of one oxygen and two hydrogen atoms sharing a vacancy site (V-O-H2 complex). Ab initio calculations are used to explore the structures and properties of this defect. The origin of other LVM bands, which were observed upon annealing, is discussed

  • 221.
    Markevich, V.P.
    et al.
    Centre for Electronic Materials, University of Manchester.
    Hourahine, B.
    Theoretische Physik, Universität Paderborn.
    Newman, R.C.
    Centre for Electronic Materials and Devices, Blackett Laboratory, Imperial College of Science.
    Jones, R.
    School of Physics, University of Exeter.
    Kleverman, M.
    Department of Physics, University of Lund.
    Lindström, J.L.
    Department of Physics, University of Lund.
    Murin, L.I.
    Institute of Solid State and Semiconductor Physics, Minsk.
    Suezawa, M.
    Institute for Materials Research, Tohoku University.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P.R.
    Department of Physics, University of Newcastle.
    Stable hydrogen pair trapped at carbon impurities in silicon2003Inngår i: Diffusion and defect data, solid state data. Part A, Defect and diffusion forum, ISSN 1012-0386, E-ISSN 1662-9507, Vol. 221, s. 1-9Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Local mode spectroscopy and ab initio modeling are used to investigate two trigonal defects found in carbon rich Si into which H had been in-diffused. Isotopic shifts with D and 13C are reported along with the effect of uniaxial stress. Ab-initio modeling studies suggest that the two defects are two forms of the CH2* complex where one of the two hydrogen atoms lies at an anti-bonding site attached to C or Si respectively. The two structures are nearly degenerate and possesess vibrational modes in good agreement with those observed experimentally. The defects are energetically favorable in comparison with separated Cs and H2 in Si and may represent aggregation sites for hydrogen.

  • 222.
    Markevich, V.P.
    et al.
    Institute of Solid State and Semiconductor Physics, Minsk.
    Murin, L.I.
    Institute of Solid State and Semiconductor Physics, Minsk.
    Lastovskij, S.B.
    Institute of Solid State and Semiconductor Physics, Minsk.
    Medvedeva, L.R.
    Institute of Solid State and Semiconductor Physics, Minsk.
    Lindström, J.L.
    Lund University, Division of Solid State Physics.
    Peaker, A.R.
    Centre for Electronic Materials, Devices and Nanostructures, University of Manchester.
    Coutinho, J.
    Department of Physics, University of Aveiro, Campus Santiago.
    Jones, R.
    School of Physics, University of Exeter.
    Torres, V.J.B.
    Department of Physics, University of Aveiro, Campus Santiago.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Electronic properties and structure of a complex incorporating a self-interstitial and two oxygen atoms in silicon2005Inngår i: Solid State Phenomena, ISSN 1012-0394, E-ISSN 1662-9779, Vol. 108, s. 273-278Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The electronic properties and structure of a complex incorporating a self-interstitial (I) and two oxygen atoms are presented by a combination of deep level transient spectroscopy (DLTS), infrared absorption spectroscopy and ab-initio modeling studies. It is argued that the IO2 complex in Si can exist in four charge states (IO2-, IO20, IO2+, and IO2++). The first and the second donor levels of the IO2 complex show an inverted location order in the gap, leading to a E(0/ ++) occupancy level at Ev + 0.255 eV. Activation energies for hole emission, transformation barriers between different structures, and positions of LVM lines for different configurations and charge states have been determined. These observables were calculated by density-functional calculations, which show that they are accounted for if we consider at least two charge-dependent defect structures.

  • 223.
    Markevich, V.P.
    et al.
    Institute of Solid State and Semiconductor Physics, Minsk.
    Murin, L.I.
    Institute of Solid State and Semiconductor Physics, Minsk.
    Suezawa, M.
    Institute for Materials Research, Tohoku University.
    Lindström, J.C.
    Department of Physics, University of Lund.
    Coutinho, J.
    Department of Physics, University of Exeter.
    Jones, R.
    Department of Physics, University of Exeter.
    Briddon, P.R.
    Department of Physics, University of Newcastle.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Local vibrational mode bands of V-O-H complexes in silicon1999Inngår i: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 273-274, s. 300-304Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    H2 molecules, which are introduced into moderately doped silicon crystals by high-temperature in-diffusion from H2 gas ambient followed by fast cooling to room temperature, are found to interact effectively with the defects induced by irradiation of the crystals with fast electrons. In Czochralski-grown silicon crystals, the interaction of the mobile H2 molecules with vacancy-oxygen defects (A centers) leads to the creation of V-O-H2 complexes. This complex gives rise to infrared (IR) absorption lines at 943.5, 2126.4, and 2151.5 cm-1. Ab initio calculations showed that the most stable configuration of V-O-H2 consists of one oxygen and two hydrogen atoms sharing a vacancy site. It is suggested that the interaction of the V-O-H2 complexes with interstitial oxygen atoms results in the formation of V-O2-H2 complexes, which are responsible for the IR absorption line at 891.5 cm-1.

  • 224.
    Markevich, V.P.
    et al.
    Centre for Electronic Materials, University of Manchester Institute of Science and Technology.
    Peaker, A.R.
    Centre for Electronic Materials, University of Manchester Institute of Science and Technology.
    Coutinho, J.
    Department of Physics, University of Aveiro.
    Jones, R.
    School of Physics, University of Exeter.
    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.
    Murin, L.I.
    Institute of Solid State and Semiconductor Physics, Minsk.
    Dobaczewski, L.
    Institute of Physics, Polish Academy of Sciences.
    Abrosimov, N.V.
    Institute of Crystal Growth, Berlin.
    Structure and properties of vacancy-oxygen complexes in Si1-xGex alloys2004Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 69, nr 12, s. 125218-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The electronic properties and structure of vacancy-oxygen (VO) complexes in Czochralski-grown Si1-xGex crystals (0

  • 225.
    Markevich, V.P.
    et al.
    Centre for Electronic Materials, University of Manchester.
    Peaker, A.R.
    Centre for Electronic Materials, University of Manchester.
    Murin, L.I.
    Institute of Solid State and Semiconductor Physics, Minsk.
    Coutinho, J.
    Department of Physics, University of Aveiro.
    Torres, V.J.B.
    Department of Physics, University of Aveiro.
    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.
    Auret, F.D.
    Centre for Electronic Materials, University of Manchester.
    Abrosimov, N.V.
    Institute of Crystal Growth, Berlin.
    Electronic properties of vacancy-oxygen complexes in SiGe alloys2003Inngår i: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 340, s. 790-4Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Capacitance transient techniques, combined with ab initio modeling, were employed to study the electronic properties and structure of vacancy-oxygen (VO) complexes in unstrained Czochralski-grown Si1-xGex crystals (0

  • 226.
    Murin, L.I.
    et al.
    Institute of Solid State and Semiconductor Physics, Minsk.
    Lindström, J.L.
    Department of Physics, Lund University.
    Markevich, V.P.
    Centre for Electronic Materials, University of Manchester.
    Hallberg, T.
    Defence Research Establishment, Linköping.
    Litvinov, V.V.
    Belarusian State University, Minsk.
    Coutinho, J.
    School of Physics, University of Exeter.
    Jones, R.
    School of Physics, University of Exeter.
    Briddon, P.R.
    Department of Physics, University of Newcastle.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Isotopic effects on vibrational modes of thermal double donors in Si and Ge2001Inngår i: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 308, s. 290-293Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The local vibrational modes of thermal double donors in Si and Ge are investigated by FTIR and ab initio modelling. At most, two oxygen modes are detected from each donor, which exhibit regular shifts with increasing donor number. By using mixtures of 16O and 18O, it is found that in Si the upper band does not yield any new modes suggesting that any oxygen atom is decoupled from any other. However, the lower frequency bands exhibit unique mixed modes proving for the first time that oxygen atoms are coupled together and in close spatial proximity. Ab initio calculations demonstrate that the modes and their isotopic shifts are consistent with a model involving two parallel chains of oxygen atoms linking second neighbour Si atoms, terminated by O-atoms close to the normal position for interstitial O.

  • 227.
    Nielsen, B. Bach
    et al.
    Institute of Physics and Astronomy, University of Aarhus.
    Tanderup, K.
    Institute of Physics and Astronomy, University of Aarhus.
    Budde, M.
    Institute of Physics and Astronomy, University of Aarhus.
    Bonde-Nielsen, K.
    Institute of Physics and Astronomy, University of Aarhus.
    Lindström, J.L.
    Department of Physics, Linköping University.
    Jones, R.
    Department of Physics, University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Hourahine, B.
    Department of Physics, University of Newcastle.
    Briddon, P.
    Department of Physics, University of Newcastle.
    Local vibrational modes of weakly bound O-H complexes in SI1997Inngår i: Defects in semiconductors: proceedings of the 19th International Conference on Defects in Semiconductors, Aveiro, Portugal, July 1997 / [ed] Gordon Davies, Trans Tech Publications Inc., 1997, s. 391-398Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Local vibrational modes of two oxygen-hydrogen complexes have been identified with infrared absorption spectroscopy. Samples of intrinsic silicon and samples doped with 16O or 18O isotopes were implanted with protons and deuterons at ∼20 K. After the implantation, infrared absorbance spectra were measured at 8 K on unannealed samples. An oxygen mode at 1077 cm-1 and a hydrogen mode at 1879 cm-1, which originate from the same defect OHI were observed in the as-implanted samples. Heat-treatment at 200 K produced a new center OHII with modes at 1028 and 1830 cm-1. OHI anneals out at ∼130 K while OHII is stable up to ∼240 K. OHI and OHII are tentatively identified with two complexes of interstitial oxygen and bond-centred hydrogen. Ab initio theory was applied to calculate the structure and local modes of three such complexes. The results qualitatively support our tentative assignments.

  • 228.
    Nielsen, B. Bech
    et al.
    University of Aarhus.
    Holbech, J.D.
    University of Aarhus.
    Jones, R.
    University of Exeter.
    Sitch, P.
    University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Observation and theory of the H2* defect in silicon1994Inngår i: Proceedings of the 17th International Conference on Defects in Semiconductors: Gmunden, Austria, July 18 - 23, 1993 / [ed] Helmut Heinrich, Trans Tech Publications Inc., 1994, s. 845-852Konferansepaper (Fagfellevurdert)
  • 229.
    Ohlin, Lindsay
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Berezovsky, Vladimir
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Farzaneh, Amirfarrokh
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Effect of Water on the Adsorption of Methane and Carbon Dioxide in Zeolite Na-ZSM-5 Studied Using in Situ ATR-FTIR Spectroscopy2016Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 51, s. 29144-29152Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Methane is the main component in biogas and natural gas along with contaminants such as water and carbon dioxide. Separation of methane from these contaminants is therefore an important step in the upgrading process. Zeolite adsorbents and zeolite membranes have great potential to be cost-efficient candidates for upgrading biogas and natural gas, and in both of these applications, knowing the nature of the competitive adsorption is of great importance to further develop the properties of the zeolite materials. The binary adsorption of methane and carbon dioxide in zeolites has been studied to some extent, but the influence of water has been much less studied. In the present work, in situ ATR (attenuated total reflection)–FTIR (Fourier transform infrared) spectroscopy was used to study the adsorption of water/methane and water/carbon dioxide from binary mixtures in a high-silica Na-ZSM-5 zeolite film at various gas compositions and temperatures. Adsorbed concentrations for all species were determined from the recorded IR spectra, and the experimental values were compared to values predicted using the ideal adsorbed solution theory (IAST). At lower temperatures (35, 50, and 85 °C), the IAST was able to predict the binary adsorption of water and methane, whereas the values predicted by the IAST deviated from the experimental data at the highest temperature (120 °C). For the binary adsorption of water and carbon dioxide, the IAST could not predict the adsorption values accurately. This discrepancy was assigned to the particular adsorption behavior of water in high-silica MFI forming clusters at hydrophilic sites. However, the predicted values did follow the same trend as the experimental values. The adsorption selectivity was determined, and it was found that the H2O/CH4 adsorption selectivity was decreasing with increasing water content in the gas phase at low temperatures whereas the selectivity was increasing at higher temperatures. The H2O/CO2 adsorption selectivity was increasing with increasing water content at all temperatures.

  • 230.
    Pinho, N.M.C.
    et al.
    School of Physics, University of Exeter.
    Torres, V.B.
    Department of Physics, University of Aveiro.
    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.
    Mg-H and Be-H complexes in c-BN2001Inngår i: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 308, s. 1027-30Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ab initio calculations on hydrogen complexes with Mg and Be impurities in c-BN are reported. We find that both impurities are acceptors and bind H to form passive defects. However, their structures are different. For Be-H, the H atom lies at a puckered bond centre configuration similar to C-H in GaAs, while in Mg-H the H atom lies at an anti-bonding site to an N neighbour of the impurity. The hydrogen related vibrational modes of the two complexes are also reported.

  • 231.
    Pinho, N.M.C.
    et al.
    Department of Physics, University of Aveiro.
    Torres, V.J.B.
    Department of Physics, University of Aveiro.
    Jones, R.
    School of Physics, University of Exeter.
    Briddon, P.R.
    Department of Physics, University of Newcastle.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Mg-H and Be-H complexes in cubic boron nitride2001Inngår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 13, nr 40, s. 8951-8956Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ab initio calculations on hydrogen complexes with Mg and Be impurities in c-BN are reported. We find that both impurities are acceptors and both bind H to form passive defects. However, their structures are different. For Be-H, the H atom lies at a puckered bond-centre configuration similar to that of C-H in GaAs, while in Mg-H, the H atom lies at a site anti-bonding to a N neighbour of the impurity. The hydrogen-related vibrational modes of the two complexes are also reported.

  • 232.
    Pinto, H.
    et al.
    COMP, Department of Applied Physics, Aalto University.
    Haapasilta, Ville
    COMP, Department of Applied Physics, Aalto University.
    Lokhandwala, M.
    COMP, Department of Applied Physics, Aalto University.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Foster, Adam S.
    COMP, Department of Applied Physics, Aalto University.
    Adsorption and migration of single metal atoms on the calcite (10.4) surface2017Inngår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 29, nr 13, artikkel-id 135001Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Transition metal atoms are one of the key ingredients in the formation of functional 2D metal organic coordination networks. Additionally, the co-deposition of metal atoms can play an important role in anchoring the molecular structures to the surface at room temperature. To gain control of such processes requires the understanding of adsorption and diffusion properties of the different transition metals on the target surface. Here, we used density functional theory to investigate the adsorption of 3d (Ti, Cr, Fe, Ni, Cu), 4d (Zr, Nb, Mo, Pd, Ag) and 5d (Hf, W, Ir, Pt, Au) transition metal adatoms on the insulating calcite (10.4) surface. We identified the most stable adsorption sites and calculated binding energies and corresponding ground state structures. We find that the preferential adsorption sites are the Ca–Ca bridge sites. Apart from the Cr, Mo, Cu, Ag and Au all the studied metals bind strongly to the calcite surface. The calculated migration barriers for the representative Ag and Fe atoms indicates that the metal adatoms are mobile on the calcite surface at room temperature. Bader analysis suggests that there is no significant charge transfer between the metal adatoms and the calcite surface.

  • 233.
    Pinto, H.
    et al.
    College of Engineering, Mathematics and Physical Sciences, University of Exeter.
    Jones, R.
    College of Engineering, Mathematics and Physical Sciences, University of Exeter.
    Palmer, D.W.
    College of Engineering, Mathematics and Physical Sciences, University of Exeter.
    Goss, J.O
    School of Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Briddon, P.R.
    School of Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Theory of the surface effects on the luminescence of the NV(-) defect in nanodiamond2011Inngår i: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 208, nr 9, s. 2045-2050Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A vacancy with one of the carbon neighbours replaced by a nitrogen atom in diamond (the NV centre) is a defect of particular interest due to its many potential applications. In the negatively charged state, the defect is paramagnetic with spin 1 and under optical excitation it exhibits an intense luminescence with a zero-phonon line at 1.945eV. This fluorescence is found in nanodiamonds even as small as 5nm and an important question is the effect of the surface of the nanodiamond on the optical emission of NV-. Density functional calculations are used in this work to investigate the effect of the bare (001) and (001)-OH diamond surfaces on the electronic structure of NV -. We show that the (001)-OH diamond surface has the minimum interaction with the defect and is the ideal terminating surface of nanodiamonds, while the bare (001) diamond surface has a strong effect on broadening the emission.

  • 234.
    Pinto, H.
    et al.
    Hungarian Academy of Sciences, Wigner Research Centre for Physics, Institute for Solid State Physics and Optics.
    Jones, R.
    College of Engineering, Mathematics and Physical Sciences, University of Exeter.
    Palmer, D.W.
    College of Engineering, Mathematics and Physical Sciences, University of Exeter.
    Goss, J.P.
    School of Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Briddon, P.R.
    School of Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    On the diffusion of NV defects in diamond2012Inngår i: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 209, nr 9, s. 1765-1768Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Besides their importance for quantum information processing, NV defects are crucial agents for the diffusion and aggregation of nitrogen in diamond. In the absence of transition metals, it is thought that the first stage of nitrogen aggregation, where close neighbour nitrogen pairs are formed, is mediated by NV defects. Here we use density functional theory to explore the barriers to NV diffusion. We conclude that the barrier is around 5 eV when there is a ready source of vacancies and that this barrier is weakly dependent on pressure.

  • 235.
    Pinto, H.
    et al.
    School of Engineering, Mathematics and Physical Sciences, University of Exeter.
    Jones, R.
    School of Engineering, Mathematics and Physical Sciences, University of Exeter.
    Palmer, D.W.
    School of Engineering, Mathematics and Physical Sciences, University of Exeter.
    Goss, J.P.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Tiwari, Amit K.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Briddon, P.R.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Wright, Nick G.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Horsfall, Alton B.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Rayson, Mark
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    First-principles studies of the effect of (001) surface terminations on the electronic properties of the negatively charged nitrogen-vacancy defect in diamond2012Inngår 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]

    Density functional calculations have been carried out on (001)-orientated slabs of diamond with different surface terminations. A negatively charged nitrogen-vacancy defect (NV-) is placed in the middle of the slab approximately 1 nm from each surface and the effect of the surface on the internal optical transition in NV- investigated. The calculations show that the chemical nature of the surface is important. We find that although the clean surface does not lead to charge transfer between the defect and the surface, there is a splitting of the empty excited state, the final state in optical absorption, arising from a strong hybridization of the surface and defect bands. This leads to a broadening of the 1.945-eV transition of the NV- defect. OH- and F-terminated surfaces have no surface states in the band gap and again charge transfer between the defect and surface does not occur. The splitting of the e levels responsible for the optical transitions for OH or F termination is similar to that found in periodic boundary condition simulations for bulk diamond where the defects are separated by 1 nm, and thus the calculations show that hydroxylated or fluorinated surfaces give favorable optical properties.

  • 236.
    Pinto, Helder M.
    et al.
    College of Engineering, Mathematics and Physical Sciences, University of Exeter.
    Palmer, Derek W.
    College of Engineering, Mathematics and Physical Sciences, University of Exeter.
    Jones, R.
    College of Engineering, Mathematics and Physical Sciences, University of Exeter.
    Goss, Jonathan P.G.
    School of Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Briddon, Patrick R.
    School of Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Ab initio studies of fluorine passivation on the electronic structure of the NV- defect in nanodiamond2012Inngår i: Journal of Nanoscience and Nanotechnology, ISSN 1533-4880, E-ISSN 1533-4899, Vol. 12, nr 11, s. 8589-8593Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have investigated using density functional theory the effect of fluorine termination of a (001) diamond surface on the electronic energy levels of an NV- centre buried beneath the surface. We find that, like OH termination, fluorine passivates the surface and reduces the influence of the surface on the electronic properties of the NV- centre. The results have significance for the optical properties of NV- defects in nanodiamonds

  • 237.
    Pinto, H.M.
    et al.
    Department of Physics, University of Minho, Campus de Gualtar, 4710-553 Braga.
    Coutinho, J.
    Department of Physics, University of Aveiro.
    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.
    Formation energy and migration barrier of a Ge vacancy from ab initio studies2006Inngår i: Materials Science in Semiconductor Processing, ISSN 1369-8001, E-ISSN 1873-4081, Vol. 9, nr 4-5, s. 498-502Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Here we present local density functional calculations of the formation and migration energies of a vacancy in large Ge supercells and hydrogen-terminated Ge clusters. Migration barriers for neutral (V0), negatively charged (V-) and double negatively charged (V=) vacancies were calculated by using symmetry-constrained atomic relaxations, as well as a nudged elastic band scheme. The formation energy of the neutral vacancy is estimated at 2.6 eV, whereas 0.4, 0.1 and 0.04 eV are obtained for migration barriers of V0, V- and V=, respectively. These figures account well for the formation kinetics of vacancy-impurity complexes in Ge at cryogenic temperatures, and are also in line with measured self-diffusion activation barriers obtained at elevated temperatures

  • 238.
    Prezzi, D.
    et al.
    School of Physics, University of Exeter.
    Eberlein, T.A.G.
    School of Physics, University of Exeter.
    Filhol, J.S.
    School of Physics, University of Exeter.
    Jones, R.
    School of Physics, University of Exeter.
    Shaw, M.J.
    School of Natural Science, University of Newcastle upon Tyne.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Optical and electrical properties of vanadium and erbium in 4H-SiC2004Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 69, nr 19, s. 193202-1Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Local-density-functional calculations are carried out on vanadium and erbium centers in 4H-SiC. Particular attention is paid to their electrical and optical properties. We find that both V and Er lie at Si sites and can exist in three charge states with deep donor and acceptor levels. While isolated VSi possesses intra-d and ionization induced optical transitions around 0.94 and 2.9 eV respectively, the intense and temperature stable intra-f optical transitions due to Er are unlikely to be due to an isolated Er defect. It is suggested that both impurities can trap H and N forming complexes which may limit the electrical efficiency of V and act as Er related exciton traps.

  • 239.
    Prezzi, D.
    et al.
    School of Physics, University of Exeter.
    Eberlein, T.A.G.
    School of Physics, University of Exeter.
    Jones, R.
    School of Physics, University of Exeter.
    Hourahine, B.
    Theoretische Physik, Universität Paderborn.
    Briddon, P.R.
    School of Natural Science, University of Newcastle upon Tyne.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Hydrogen-related photoluminescent centers in SiC2004Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 70, nr 20, s. 205207-1Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Local density functional calculations are used to investigate models of the center responsible for a prominent set of luminescent lines with zero-phonon lines around 3.15 eV in hydrogen rich 4H-SiC and previously attributed to VSi-H . We find that the electronic structure of this defect and the character of its vibrational modes are inconsistent with this assignment. In contrast, a H2* center, bound to a carbon anti-site, is more stable than the isolated molecule and possesses a donor level close to that observed for the H-lines. Moreover, its vibrational modes are in good agreement with experiment. A possible mechanism for the radiation enhanced quenching of the defect is discussed.

  • 240.
    Pritchard, R E
    et al.
    Imperial College of Science Technology and Medicine.
    Newman, R C
    Imperial College of Science Technology and Medicine.
    Wagner, J
    Fraunhofer-Institut für Angewandte Festkörperphysik, Tullastrasse 72, D-79108 Freiburg.
    Fuchs, F
    Fraunhofer-Institut für Angewandte Festkörperphysik, Tullastrasse 72, D-79108 Freiburg.
    Jones, R
    University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Bonding of H-CAs pairs in AlxGa1-xAs alloys1994Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 50, nr 15, s. 10628-10636Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The local structure of CAs acceptors in AlxGa1-xAs has been investigated by studying the nondegenerate localized vibrational modes of H-CAs pairs with A1 symmetry, rather than those of isolated CAs impurities. Infrared absorption and Raman scattering measurements have been made on AlxGa1-xAs: 12C epilayers that (a) had been exposed to a radio-frequency hydrogen (deuterium) plasma or (b) contained hydrogen incorporated during growth. Arguments are advanced that indicate that the H(D) atom should occupy a bond-centered site between CAs and Ga atoms rather than between CAs and Al atoms at low temperatures. An ab initio local-density-functional calculation indicates that the energy is then lowered by 0.24 eV. This analysis has led to the assignment of five antisymmetric stretch modes and five symmetric (X) modes to H-CAs pairs at sites where the carbon atom that was originally unpaired had zero, one, two, three, or four Al nearest neighbors

  • 241.
    Purton, J.
    et al.
    Royal Institution of Great Britain.
    Jones, R.
    Department of Physics, University of Exeter.
    Heggie, M.
    Department of Computer Science, University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    LDF pseudopotential calculations of the α-quartz structure and hydrogarnet defect1992Inngår i: Physics and chemistry of minerals, ISSN 0342-1791, E-ISSN 1432-2021, Vol. 18, nr 6, s. 389-392Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ab initio LDF theory has been used to study the structure of the hydrogarnet defect in α-quartz. The predicted structure is in good agreement with the available sexperimental data. The techniques employed also yield a good model for the structure of α-quartz, giving an average Si-O bond length of 1.62 Å and average Si-O-Si angle of 142°.

  • 242.
    Rahbi, R.
    et al.
    Groupe de Physique des Solides, Université Denis Diderot.
    Theys, B.
    Laboratoire de Physique des Solides, CNRS.
    Pajot, B.
    Department of Physics, University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Somogyi, K.
    Research Institute for Technical Physics, P.O. Box 76, Foti ùt. 56, Budapest.
    Fille, M.L.
    LPSES, CNRS, Sophia Antipolis.
    Chevallier, J.
    Laboratoire de Physique des Solides, CNRS.
    Neutralisation of group vi donors by hydrogen in gallium arsenide1994Inngår i: Solid State Communications, ISSN 0038-1098, E-ISSN 1879-2766, Vol. 91, nr 3, s. 187-190Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The infrared absorption of GaAs:S and GaAs:Te samples partially neutralised by hydrogen show two local modes with very similar frequencies. These modes are comparable to the ones already reported in GaAs:Se. These results are interpreted by assuming that neutralisation takes place by the formation of a bond between a Ga atom first neighbour of the chalcogen and a H atom in an antibonding location. This assumption is strengthened by ab initio calculations that provide also frequencies of the right order of magnitude.

  • 243.
    Rasmussen, F Berg
    et al.
    University of Aarhus.
    Jones, R
    University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Nitrogen in germanium: identification of the pair defect1994Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 50, nr 7, s. 4378-4384Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Several nitrogen-related centers have been introduced by ion implantation of nitrogen into germanium and studied by infrared-absorption spectroscopy. Two local vibrational modes at 825.3 and 658.6 cm-1 were especially prominent. Measurements on annealed samples implanted with either pure 14N or 15N, or implanted with both isotopes showed these modes to arise from a nitrogen pair defect analogous to one previously suggested to occur in silicon. Based on this and ab initio pseudopotential cluster theory, a model of the pair is proposed which is consistent with the observed infrared absorption. This model is similar to that of the nitrogen pair in silicon and offers an explanation of the low donor efficiency of nitrogen in germanium. Several other nitrogen-related local vibrational modes are also observed in the implanted material.

  • 244.
    Rasmussen, F Berg
    et al.
    University of Aarhus.
    Nielsen, B Bech
    University of Aarhus.
    Jones, R
    University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Comment on "Role played by N and N-N impurities in type-IV semiconductors"1995Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 51, nr 20, s. 14756-14757Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    In a recent paper [Phys. Rev. B 48, 17 806 (1993)] Cunha, Canuto, and Fazzio reported ab initio Hartree-Fock calculations on nitrogen impurities in group-IV semiconductors. In their paper it is suggested that nitrogen pairs form from substitutional atoms on adjacent lattice sites. However, the experimentally observed configuration in silicon and germanium is different from this. The aim of this Comment is to clarify the situation of the nitrogen pair in these materials.

  • 245.
    Rasmussen, F. Berg
    et al.
    University of Aarhus.
    Nielsen, B. Bech
    University of Aarhus.
    Jones, R.
    University of Exeter.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    The nitrogen pair in crystalline silicon studied by ion channeling1994Inngår i: Proceedings of the 17th International Conference on Defects in Semiconductors: Gmunden, Austria, July 18 - 23, 1993 / [ed] Helmut Heinrich, Trans Tech Publications Inc., 1994, s. 1221-1226Konferansepaper (Fagfellevurdert)
  • 246. Rasmussen, F. Berg
    et al.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Jones, R.
    Ewels, C.
    Goss, J.
    Miro, J.
    Deak, P.
    The NNO defect in silicon1995Inngår i: Proceedings of the 18th International Conference on Defects in Semiconductors: ICDS-18; Sendai, Japan, July 23 - 28, 1995 / [ed] Masashi Suezawa, Trans Tech Publications Inc., 1995, s. 791-796Konferansepaper (Fagfellevurdert)
  • 247.
    Rasmussen, F. Berg
    et al.
    Van der Waals-Zeeman Institute, University of Amsterdam.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Jones, R.
    Department of Physics, University of Exeter.
    Ewels, C.
    Department of Physics, University of Exeter.
    Goss, J.
    Department of Physics, University of Exeter.
    Miro, J.
    Department of Atomic Physics, Technical University of Budapest.
    Deák, P.
    Department of Atomic Physics, Technical University of Budapest.
    The nitrogen-pair oxygen defect in silicon1996Inngår i: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 36, nr 1-3, s. 91-95Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The nitrogen-pair oxygen defect in silicon has been studied by infrared absorption spectroscopy on samples implanted with various combinations of 14N, 15N, 16O and 17O. The measurements give direct evidence for the involvement of nitrogen and oxygen in the defect and show that the impurity atoms comprising the defect are only weakly coupled. Ab initio cluster calculation on several models of the nitrogen-pair oxygen defect have been performed and are compared with experiment. Based on these investigations a model consisting of a bridging oxygen atom adjacent to the nitrogen pair is suggested

  • 248. Resende, A
    et al.
    Goss, J
    Briddon, P R
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Jones, R
    Theory of gold-hydrogen complexes in silicon1997Inngår i: Defects in Semiconductors: proceedings of the 19th International Conference on Defects in Semiconductors, Aveiro, Portugal, July 1997 / ICDS-19 / [ed] Gordon Davies, Uetikon-Zuerich: Trans Tech Publications Inc., 1997, s. 295-300Konferansepaper (Fagfellevurdert)
  • 249.
    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.

  • 250.
    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.
    The structural properties of transition metal hydrogen complexes in silicon1998Inngår i: E-MRS Meeting, European Materials Research Society , 1998Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A first-principles spin-polarised local density functional cluster method is used to explore the structural and vibrational properties of several substitutional transition-metal impurities complexed with hydrogen.

23456 201 - 250 of 288
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