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Träfflista för sökning "WFRF:(Öberg B.) ;pers:(Jones R.)"

Sökning: WFRF:(Öberg B.) > Jones R.

  • Resultat 1-10 av 72
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1.
  • Coomer, B.J., et al. (författare)
  • Vacancy-hydrogen complexes in germanium
  • 1998
  • Ingår i: E-MRS Meeting. - : European Materials Research Society.
  • Konferensbidrag (refereegranskat)abstract
    • 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
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2.
  • Coomer, B.J., et al. (författare)
  • Vacancy-hydrogen complexes in germanium
  • 1999
  • Ingår i: Materials Science & Engineering. - 0921-5107 .- 1873-4944. ; 58:1-2, s. 36-38
  • Tidskriftsartikel (refereegranskat)abstract
    • 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
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3.
  • Hoffmann, L., et al. (författare)
  • Weakly bound carbon-hydrogen complex in silicon
  • 2000
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 61:24, s. 16659-16666
  • Tidskriftsartikel (refereegranskat)abstract
    • Local vibrational modes of a weakly bound carbon-hydrogen complex in silicon have been identified with infrared-absorption spectroscopy. After implantation of protons at ∼20 K and subsequent annealing at 180 K, two carbon modes at 596 and 661 cm-1, and one hydrogen mode at 1885 cm-1 are observed. The three modes originate from the same complex, which is identified as bond-centered hydrogen in the vicinity of a nearby substitutional carbon atom. Ab initio theory has been applied to calculate the structure and local modes of carbon-hydrogen complexes with hydrogen located at the first, second, and third nearest bond-center site to substitutional carbon. The results support our assignment.
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4.
  • Lavrov, E.V., et al. (författare)
  • Combined infrared absorption and modeling study of a dicarbon-dihydrogen defect in silicon
  • 2000
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 62:19, s. 12859-12867
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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5.
  • Lavrov, E. V., et al. (författare)
  • Local vibrational modes of two neighboring substitutional carbon atoms in silicon
  • 2000
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 62:1, s. 158-165
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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6.
  • Nielsen, B. Bach, et al. (författare)
  • Local vibrational modes of weakly bound O-H complexes in SI
  • 1997
  • Ingår i: Defects in semiconductors. - : Trans Tech Publications Inc.. ; , s. 391-398
  • Konferensbidrag (refereegranskat)abstract
    • 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.
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7.
  • Wagner, J, et al. (författare)
  • Di-Carbon defects in annealed highly carbon doped GaAs
  • 1997
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 78:1, s. 74-77
  • Tidskriftsartikel (refereegranskat)abstract
    • Formation of bonded dicarbon C-C centers is deduced from the observation of Raman lines at 1742, 1708, and 1674 cm -1 in GaAs codoped with 12C and 13C after annealing at 850 °C with concomitant loss of vibrational scattering from CAs. The frequencies agree with results of ab initio theory for a C-C split interstitial (deep donor) formed by the trapping of a mobile interstitial C (displaced CAs) atom by an undisplaced CAs acceptor. Other mechanisms of carrier loss are inferred since a weaker Raman triplet is detected at 1859, 1824, and 1788 cm -1 from a different C-C complex.
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8.
  • Andersen, O., et al. (författare)
  • Electrical activity of carbon-hydrogen centers in Si
  • 2002
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 66:23, s. 235205-1
  • Tidskriftsartikel (refereegranskat)abstract
    • The electrical activity of Cs-H defects in Si has been investigated in a combined modeling and experimental study. High-resolution Laplace capacitance spectroscopy with the uniaxial stress technique has been used to measure the stress-energy tensor and the results are compared with theoretical modeling. At low temperatures, implanted H is trapped as a negative-U center with a donor level in the upper half of the gap. However, at higher temperatures, H migrates closer to the carbon impurity and the donor level falls, crossing the gap. At the same time, an acceptor level is introduced into the upper gap making the defect a positive-U center.
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9.
  • Andersen, O., et al. (författare)
  • Piezospectroscopic analysis of the hydrogen-carbon complexes in silicon
  • 2001
  • Ingår i: Physica. B, Condensed matter. - 0921-4526 .- 1873-2135. ; 308, s. 139-142
  • Tidskriftsartikel (refereegranskat)abstract
    • We have observed the donor (Ec-0.22 eV) and acceptor (Ec-0.16 eV) levels related to hydrogen-carbon complexes in silicon. The donor level is only detected at low temperatures after proton implantation. This hydrogen-carbon complex irreversibly reconfigures at temperatures above 225 K to a configuration characterized by the acceptor level, which is stable up to room temperature. The same acceptor level is also observed after atomic hydrogen diffusion. We have used Laplace transform deep level transient spectroscopy (DLTS) to show the influence of uniaxial stress on the electron emission process and the effect of the stress-induced alignment for the acceptor state. The pattern of the Laplace DLTS peak splittings indicate a trigonal symmetry of the defect. First principles calculations were carried out on the hydrogen-carbon defects with a view of determining their electrical levels and stress response for comparison with the experimental results.
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10.
  • Ashwin, M.J., et al. (författare)
  • The bonding of CAs acceptors in InxGa1-xAs grown by chemical beam epitaxy using carbon tetrabromide as the source of carbon
  • 1996
  • Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 80:12, s. 6754-6760
  • Tidskriftsartikel (refereegranskat)abstract
    • InxGa1-xAs layers (0≤x≤0.37) doped with carbon (>1020 cm-3) were grown on semi-insulating GaAs substrates by chemical beam epitaxy using carbon tetrabromide (CBr4) as the dopant source. Hall measurements imply that all of the carbon was present as CAs for values x up to 0.15. The C acceptors were passivated by exposing samples to a radio frequency hydrogen plasma for periods of up to 6 h. The nearest-neighbor bonding configurations of CAs were investigated by studying the nondegenerate antisymmetric hydrogen stretch mode (A-1 symmetry) and the symmetric XH mode (A+1 symmetry) of the H-CAs pairs using IR absorption and Raman scattering, respectively. Observed modes at 2635 and 450 cm-1 had been assigned to passivated Ga4CAs clusters. New modes at 2550 and 430 cm-1 increased in strength with increasing values of x and are assigned to passivated InGa3CAs clusters. These results were compared with ab initio local density functional theory. Modes due to AlInGaCAs clusters were detected in samples containing grown in Al and In. These results demonstrate that for InGaAs, CBr4 is an efficient C doping source since both In-CAs bonds as well as Ga-CAs bonds are formed, whereas there is no evidence for the formation of In-CAs bonds in samples doped with C derived from trimethylgallium or solid sources
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  • Resultat 1-10 av 72

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