| 1. |
- BERTOLOTTO, L, et al.
(författare)
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RESULTS FROM (P)OVER-BAR-P-]PHI-PHI
- 1994
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Ingår i: NUOVO CIMENTO DELLA SOCIETA ITALIANA DI FISICA A-NUCLEI PARTICLES AND FIELDS. - : EDITRICE COMPOSITORI BOLOGNA. ; , s. 2329-2337
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Konferensbidrag (refereegranskat)abstract
- The reaction ($) over bar pp --> phi phi is investigated in the JETSET (PS202) experiment using an internal target in LEAR. Data have been analysed at a variety of beam momenta from 1.2 GeV/c to 2.0 GeV/c, corresponding to centre-of-mass energies between
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| 2. |
- Jones, R, et al.
(författare)
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Ab initio calculations of anharmonicity of the C-H stretch mode in HCN and GaAs
- 1994
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 50:12, s. 8378-8388
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Tidskriftsartikel (refereegranskat)abstract
- The anharmonicities of the C-H stretch modes in HCN and the passivated C acceptor in GaAs are investigated using ab initio local-density-functional cluster theory. The effective-mass parameter χ for the C-H stretch mode is shown to be less than unity in HCN, and greater than unity for the GaAs case. The calculated anharmonic parameter for the first defect is found to be 106 cm-1 and is in very good agreement with experiment. For the second defect, the anharmonicity is about 50% larger in agreement with empirical estimates. The frequencies of the fundamental transitions in both systems are shown to be very sensitive to the C-H length. This limits the accuracy of theoretical investigations of these high frequency H modes. Finally, the effects of electrical anharmonicity are considered and it is shown that they reduce the intensity of the overtone in the C-H complex in GaAs by about 70%.
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| 3. |
- Jones, R, et al.
(författare)
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Identification of the dominant nitrogen defect in silicon
- 1994
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 72:12, s. 1882-1885
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Tidskriftsartikel (refereegranskat)abstract
- The structure of the dominant N pair defect in Si is determined from channeling, infrared local vibrational mode spectroscopy, and ab initio local density functional theory. Channeling experiments show that the N atoms are displaced by 1.1±0.1 Å from lattice sites along 〈100〉. Annealing experiments reveal that this N site is associated with two N-related local vibrational modes originating from the N pair. The ab initio calculations demonstrate that the pair consists of two neighboring 〈100〉 oriented N-Si split interstitials, arranged in an antiparallel configuration, and with four N-Si bonds forming a square lying on {011}.
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| 4. |
- Jones, R, et al.
(författare)
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Theory of carbon complexes in aluminum arsenide
- 1994
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 49:8, s. 5306-5312
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Tidskriftsartikel (refereegranskat)abstract
- The structural and dynamic properties of carbon defects in aluminum arsenide are investigated using first-principles local-density-functional cluster theory. The method accounts satisfactorily for the structure and phonon modes of AlAs. The carbon acceptor and donor possess triplet modes in the band gap between the acoustic and optic branches as well as localized triplet modes. The local mode of the acceptor lies within 40 cm-1 of the observed mode. Four modes of a close-by acceptor pair lie within 40 cm-1 of the local mode of the isolated acceptor and this supports a previous assignment of four satellite lines seen in heavily doped material to this defect. The modes of a donor-acceptor pair are investigated but there is no evidence of their existence.
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| 5. |
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| 6. |
- Jones, R., et al.
(författare)
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Theory of dislocations in GaAs
- 1994
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Ingår i: Proceedings of the 17th International Conference on Defects in Semiconductors. - : Trans Tech Publications Inc.. ; , s. 1605-1610
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Konferensbidrag (refereegranskat)
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| 7. |
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| 8. |
- Nielsen, B. Bech, et al.
(författare)
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Observation and theory of the H2* defect in silicon
- 1994
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Ingår i: Proceedings of the 17th International Conference on Defects in Semiconductors. - : Trans Tech Publications Inc.. ; , s. 845-852
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Konferensbidrag (refereegranskat)
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| 9. |
- Pritchard, R E, et al.
(författare)
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Bonding of H-CAs pairs in AlxGa1-xAs alloys
- 1994
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 50:15, s. 10628-10636
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Tidskriftsartikel (refereegranskat)abstract
- 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
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| 10. |
- Rasmussen, F Berg, et al.
(författare)
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Nitrogen in germanium : identification of the pair defect
- 1994
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 50:7, s. 4378-4384
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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