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| 11. |
- Nielsen, B. Bach, et al.
(författare)
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Local vibrational modes of weakly bound O-H complexes in SI
- 1997
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Ingår i: Defects in semiconductors. - : Trans Tech Publications Inc.. ; , s. 391-398
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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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| 12. |
- Coomer, B.J., et al.
(författare)
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Vacancy-hydrogen complexes in germanium
- 1998
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Ingår i: E-MRS Meeting. - : European Materials Research Society.
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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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| 13. |
- Coomer, B.J., et al.
(författare)
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Vacancy-hydrogen complexes in germanium
- 1999
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Ingår i: Materials Science & Engineering. - 0921-5107 .- 1873-4944. ; 58:1-2, s. 36-38
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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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| 14. |
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| 15. |
- Albin, Maria, et al.
(författare)
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Astma och eksem hos frisörer.
- 1998
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Ingår i: Hygiea. - 0346-6264. ; 1:Band 107:144, s. 137-137
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Konferensbidrag (refereegranskat)
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| 18. |
- Budde, M., et al.
(författare)
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Identification of the hydrogen-saturated self-interstitials in silicon and germanium
- 1998
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 57:18, s. 4397-4412
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Tidskriftsartikel (refereegranskat)abstract
- Silicon and germanium single crystals are implanted with protons. The infrared-absorption spectra of the samples contain sharp absorption lines due to the excitation of hydrogen-related local vibrational modes. The lines at 743.1, 748.0, 1986.5, and 1989.4 cm-1 in silicon and at 700.3, 705.5, 1881.8, and 1883.5 cm-1 in germanium originate from the same defect in the two materials. Measurements on samples coimplanted with protons and deuterons show that the defect contains two equivalent hydrogen atoms. Uniaxial stress measurements are carried out and a detailed analysis of the results is presented. It is shown that the defect has monoclinic-II symmetry, and the orientations of the Si-H and Ge-H bonds of the defect are determined. Ab initio local-density-functional theory is used to calculate the structure and local vibrational modes of the self-interstitial binding one and two hydrogen atoms in silicon and germanium together with the structure of the self-interstitial itself. The observed properties of the defect are in excellent agreement with those calculated for the self-interstitial binding two hydrogen atoms.
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| 19. |
- Budde, M., et al.
(författare)
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Local modes of the H2* dimer in germanium
- 1996
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 54:8, s. 5485-5494
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Tidskriftsartikel (refereegranskat)abstract
- Local vibrational modes of the H2* defect in crystalline germanium are identified by a combination of infrared-absorption spectroscopy, uniaxial stress measurements, and ab initio theory. Germanium crystals are implanted with protons and/or deuterons at 30 K, and subsequently annealed at room temperature. A number of local vibrational modes of hydrogen are revealed by infrared-absorption spectroscopy. In particular, modes at 765, 1499, 1774, and 1989 cm-1 originate from the same defect which has trigonal symmetry according to the uniaxial stress measurements. The 765-cm-1 mode is two dimensional, while the 1774- and 1989-cm-1 modes are one dimensional. Measurements on samples coimplanted with protons and deuterons show that the defect contains a pair of weakly coupled and inequivalent hydrogen atoms. The 765-, 1499-, 1774-, and 1989-cm-1 modes are ascribed to the H2* defect. The 765-cm-1 mode is a Ge-H bend mode with an overtone at 1499 cm-1 and the modes at 1774 and 1989 cm-1 are Ge-H stretch modes. An excellent fit to the stretch frequencies is obtained with a simple model based on two coupled Morse-potential oscillators. In addition, the model gives intensity ratios in fair agreement with those observed. The structure, the local-mode frequencies, and the isotope shifts of H2* are calculated with ab initio local-density-functional cluster theory. The theoretical frequencies are consistently 5-10 % too high, as expected from the theory which often leads to overbinding. The isotope shifts, however, are in fair agreement with observations. These results provide additional support for our assignments, and show that the 765- and 1774-cm-1 modes primarily involve the hydrogen at the antibonding site, while the 1989-cm-1 mode is related mainly to vibration of the hydrogen near the bond-center site.
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| 20. |
- Budde, M., et al.
(författare)
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The hydrogen-saturated self-interstitial in silicon and germanium
- 1997
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Ingår i: Defects in semiconductors. - : Trans Tech Publications Inc.. ; , s. 35-40
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Konferensbidrag (refereegranskat)abstract
- Infrared absorption spectroscopy is used to study H-related point defects in H+-implanted Si (Si:H) and Ge (Ge:H). The absorption lines at 743.1, 748.0, 1986.5 and 1989.4 cm-1 in Si:H and at 700.3, 705.5, 1881.8 and 1883.5 cm-1 in Ge:H are shown to originate from the same defect containing two equivalent H atoms. Uniaxial stress experiments show that the defects have monoclinic-II symmetry, and the orientations of the two Si-H or Ge-H bonds are determined. The structure and the local vibrational modes of the self-interstitial binding two H atoms (IH2) are calculated with LDF cluster theory. The symmetry, bond-orientations and isotopic frequency-shifts calculated for IH2 are in excellent agreement with those observed for the 743.1-, 748.0-, 1986.5- and 1989.4-cm-1 modes in Si:H and for the 700.3-, 705.5-, 1881.8- and 1883.5-cm-1 modes in Ge:H.
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| 23. |
- Hoffmann, L., et al.
(författare)
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Substitutional carbon in Ge and Si1-xGex
- 1997
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Ingår i: Defects in semiconductors. - : Trans Tech Publications Inc.. ; , s. 97-102
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Konferensbidrag (refereegranskat)abstract
- In the present work, carbon is implanted into monocrystalline Ge and into relaxed epitaxial MBE-grown Si1-xGex. The samples are studied with infrared absorption spectroscopy along with ion-channeling studies on the Ge samples. Finally, ab-initio local density functional cluster theory is applied to calculate the structure and the local vibrational modes of substitutional carbon, Cs, in Ge. After implantation of 12C+ in Ge at room temperature and subsequent annealing at 350°C, a sharp absorption line is observed at 531 cm-1. By isotope substitution, it is concluded that the 531 cm-1 line represents a local vibrational mode of a single carbon atom. From ion-channeling measurements on samples annealed at 450°C, it is found that 31±3 % of the carbon atoms are located at substitutional sites. The population of the substitutional site and the intensity of the 531 cm-1 mode have identical annealing behavior and it is concluded that the 531 cm-1 mode is the three-dimensional T2 stretch mode of Cs in Ge. The calculated frequency and isotope shift for this mode are in good agreement with the observations. In Si0.65Ge0.35, two broad absorption lines are observed at ∼551 and ∼592 cm-1 after implantation of 12C+ and subsequent annealing at 550°C. From measurements on samples implanted with 13C+ and coimplanted with 12C+ and 13C+ we conclude that these lines represent local vibrational modes of defects containing a single carbon atom. In 13C+ implanted Si1-xGex samples that contain 15 to 50 % Ge a number of modes are observed in a frequency range from ∼510 to ∼610 cm-1, i.e., in the range of Cs in Ge and in Si. From the experimental findings it is concluded that substitutional carbon in Si1-xGex binds to both Si and Ge.
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| 24. |
- Hoffmann, L., et al.
(författare)
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Substitutional carbon in germanium
- 1997
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 55:17, s. 11167-11173
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Tidskriftsartikel (refereegranskat)abstract
- Carbon impurities implanted into single-crystalline germanium are studied with infrared absorption spectroscopy and ion channeling. After implantation of 12C+ at room temperature and subsequent annealing at 350 °C, a sharp infrared absorption line is observed at 531 cm-1. When 12C+ is substituted by 13C+, the line shifts down in frequency to 512 cm-1 and co-implantation of 12C+ and 13C+ does not give rise to additional lines. Therefore, the 531-cm-1 line represents a local vibrational mode of a defect containing a single carbon atom. Channeling measurements are carried out around the 〈100〉, 〈110〉, and 〈111〉 axes in 12C+-implanted samples annealed at 450 °C. The analysis of the data shows that 31±3 % of the carbon atoms are located at substitutional sites, while the remaining carbon atoms appear to be located randomly. The population of the substitutional site and the intensity of the 531-cm-1 mode have identical temperature dependencies. It is concluded that the 531-cm-1 mode is the three-dimensional T2 stretch mode of substitutional carbon. The effective charge of the mode is determined to be (3.4±0.5)e.mAb initio local density functional cluster theory is applied to calculate the structure and the local vibrational modes of substitutional carbon in germanium. The calculated frequencies and isotope shifts for the T2 stretch mode are in good agreement with the observations.
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| 25. |
- Hoffmann, L., et al.
(författare)
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Substitutional carbon in Si1-xGex
- 1999
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 60:19, s. 13573-13581
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Tidskriftsartikel (refereegranskat)abstract
- Local vibrational modes of carbon impurities in relaxed Si1-xGex have been studied with infrared absorption spectroscopy in the composition range 0.05≤x≤0.50. Carbon modes with frequencies in the range 512-600 cm-1 are observed in 13C+-implanted Si1-xGex after annealing at 550°C. Measurements on samples coimplanted with 12C+ and 13C+ show that these modes originate from defects containing a single carbon atom and from the variation of the mode frequencies with composition x, the modes are assigned to substitutional carbon in Si1-xGex. Based on the frequencies obtained from a simple vibrational model, the observed modes are assigned to specific combinations of the four Si and Ge neighbors to the carbon. The intensities of the modes indicate that the combination of the four neighbors deviates from a random distribution. Ab initio local-density-functional cluster theory has been applied to calculate the structure and the local mode frequencies of substitutional carbon with n Ge and 4-n Si neighbors in a Si and a Ge cluster. The calculated frequencies are ∼9% higher than those observed, but the ordering and the splitting of the mode frequencies agree with our assignments.
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| 26. |
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| 27. |
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| 28. |
- Meggerle, Theis, et al.
(författare)
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A Critical Evaluation of a Project
- 1998
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Ingår i: IRIS 21 : information systems research in collaboration with industry : proceedings of the 21th Information Systems Research Seminar in Scandinavia.
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Konferensbidrag (refereegranskat)
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| 29. |
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| 30. |
- Nielsen, A S, et al.
(författare)
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Alcohol problems among suicide attempters in the Nordic countries.
- 1996
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Ingår i: Crisis. - 0227-5910 .- 2151-2396. ; 17:4, s. 157-66
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to see whether and how the number of suicide attempters with alcohol problems and their drinking habits differ between the Nordic areas under study. Problem-drinkers were defined as persons who themselves felt that they had an alcohol problem. The analyses were based on data collected at five Nordic research centers participating in the WHO/Euro Multicentre Study on Parasuicide, namely: Helsinki (Finland); Umeå and Stockholm (Sweden); Słr-Trłndelag (Norway); and Odense (Denmark). The results showed that the frequency of problem-drinking among suicide attempters differed markedly between the areas under study; the Finnish male and the Danish female suicide attempters included the highest proportions of self-identified problem-drinkers. The pattern of drinking among the suicide attempters also differed between the areas. The analyses indicate that the point when alcohol becomes a problem to somebody, especially to a degree that it increases the risk of suicidal behavior, not only depends on how much and how often the person drinks alcohol; the prevailing drinking pattern, the attitudes towards drinking alcohol, and the level of social control are also important factors to take into consideration when relations between alcohol and suicidal behavior are under study.
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| 31. |
- Rasmussen, F Berg, et al.
(författare)
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Comment on "Role played by N and N-N impurities in type-IV semiconductors"
- 1995
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 51:20, s. 14756-14757
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 34. |
- WITTUNG, P, et al.
(författare)
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PHOSPHOLIPID MEMBRANE-PERMEABILITY OF PEPTIDE NUCLEIC-ACID
- 1995
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Ingår i: FEBS LETTERS. - 0014-5793. ; 365:1, s. 27-29
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Tidskriftsartikel (refereegranskat)abstract
- Phospholipid vesicles (liposomes) as membrane models have been used to study the penetration properties of peptide nucleic acid (PNA), a new DNA analog in which the nucleobases are attached to a pseudo-peptide backbone, The liposomes were characterised by
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| 35. |
- Wittung, Pernilla, 1968, et al.
(författare)
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Phospholipid membrane permeability of peptide nucleic acid
- 1995
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Ingår i: FEBS Letters. - : Wiley. - 1873-3468 .- 0014-5793. ; 365:1, s. 27-29
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Tidskriftsartikel (refereegranskat)abstract
- Phospholipid vesicles (liposomes) as membrane models have been used to study the penetration properties of peptide nucleic acid (PNA), a new DNA analog in which the nucleobases are attached to a pseudo-peptide backbone, The liposomes were characterised by carboxyfluorescein efflux, light-scattering and cryogenic transmission electron microscopy. The liposome structure was found not to be affected by the incorporation of PNA or an oligonucleotide. Two 10-mer fluorescein-labelled PNAs were found to have low efflux rates (half-times of 5.5 and 11 days), comparable to a 10-mer oligonucleotide (half-time of 7 days). We conclude that passive diffusion of unmodified PNA is not an effective way of transport into biological cells.
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