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  • Articles: DFG German National Licenses  (56)
  • 1990-1994  (56)
  • 1920-1924
  • 1991  (56)
  • 1
    Electronic Resource
    Electronic Resource
    Calculated structures for [001] symmetrical tilt grain boundaries in silicon (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 2048-2056 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structures of [001] tilt boundaries in silicon have been systematically investigated by computer modeling, using the harmonic Keating potential to describe the interatomic forces. The full angular range of symmetrical tilt boundaries can be described in terms of linear combinations of characteristic groupings of atoms. More than one stable relaxed structure has been found for most grain boundaries. In all cases the relaxed bicrystal consists of localized groups of pure edge or 45° dislocation cores embedded in a tetrahedrally coordinated, stable structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348730
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Raman scattering study of InAs/GaInSb strained layer superlattices (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5608-5614 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a Raman scattering study of the InAs/GaInSb superlattice. This new superlattice is promising as a long wavelength infrared detector material. The samples were grown by molecular beam epitaxy and their structural parameters were determined by Rutherford backscattering and x-ray diffraction. Samples were grown on [001] GaAs substrates with GaSb buffers, and directly on [001] GaSb substrates. Cross-sectional transmission electron micrographs show that for the samples grown on GaAs substrates, a high density of dislocations was generated at the GaAs-GaSb interface, and many of these dislocations thread through the superlattice. The samples grown directly on GaSb had a much lower dislocation density. The Raman spectra of the InAs/GaInSb superlattice shows a single peak, which is a superposition of scattering from the LO phonons in InAs and in GaInSb. For unstrained InAs and GaInSb, the LO phonon energies are sufficiently separated that they would be well resolved in Raman scattering. However, the strain introduced into these materials by the pseudomorphic boundary conditions moves the two phonons closer together energetically so that only one peak is seen in the Raman spectrum of the superlattice. A high energy Raman scattering tail is seen in some of the samples. This tail is from Ga-As local modes. Such modes may be due to As incorporation in the GaInSb, Ga incorporation in the InAs or phase mixing at the interfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350174
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  • 3
    Electronic Resource
    Electronic Resource
    Rotational tunneling of methane on MgO surfaces: A neutron scattering study (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6997-7000 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High-resolution inelastic neutron scattering was used to investigate the rotational tunneling of methane molecules in a (large-closed-square)×(large-closed-square)R45° commensurate, square-lattice–solid monolayer adsorbed on MgO (100) surfaces. Good matches to the observed transition energies were obtained using potential functions with C2v symmetry, suggesting that the preferred orientation of the molecule is the dipod-down configuration with two opposite edges of the H-atom tetrahedron parallel to the surface plane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461044
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  • 4
    Electronic Resource
    Electronic Resource
    Laser induced fluorescence and vacuum ultraviolet spectroscopic studies of H-atom production in the dissociative recombination of some protonated ions (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 4852-4857 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The flowing afterglow technique, coupled with laser induced fluorescence (LIF) and vacuum ultraviolet (vuv) absorption spectroscopy, has been used to determine the fractional H-atom contributions, fH, to the product distributions for the dissociative recombination of a series of protonated ions (N2H+, HCO+, HCO+2, N2OH+, OCSH+, H2CN+, H3O+, H3S+, NH+4, and CH+5 ) with electrons. The measurements were made at 300 K in two separate ways in two laboratories by (i) directly determining the H-atom number density using vuv absorption spectroscopy at the Lα (121.6 nm) wavelength and (ii) converting the H atoms to OH radicals using the reaction H+NO2→OH+NO followed by LIF to determine the OH number density. The agreement between the two techniques is excellent and values of fH varying from ∼0.2 (for OCSH+ ) to 1.2 (for CH+5 ) have been obtained showing that in some of the cases recombination can lead to the ejection of two separate H atoms. Comparison of the oxygen/sulphur analogs, HCO+2/OCSH+ and H3O+/H3S+ showed that the fH values were very different. Possible reasons for these differences are discussed. Comparison is also made with the available theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460570
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  • 5
    Electronic Resource
    Electronic Resource
    Ranakinin: A Novel NK1 Tachykinin Receptor Agonist Isolated with Neurokinin B from the Brain of the Frog Rana ridibunda (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 57 (1991), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: An extract of the whole brain of the frog Rana ridibunda contained high concentrations of substance P-like immunoreactivity, measured with an antiserum directed against the COOH-terminal region of mammalian substance p and neurokinin b-like immurtoreactivity, measured with an antiserum directed against the NH2-terminus of neurokinin B. The primary structure of the substance p-related peptide (ranakinin) was established as: Lys-Pro-Asn-Pro-Glu-Arg-Phe-Tyr-Gly-Leu-Met-NH2. Mammalian substance P was not present in the extract. The primary structure of the neurokinin b-related peptide was established as: Asp-Met-His-Asp-Phe-Phe-Val-Gly-Leu-Met-NH2. This amino acid sequence is the same as that of mammalian neurokinin B.Ranakinin was equipotent with substance p and [Sar9,-Met(O2)11]substance p in inhibiting the binding of 125I-Bolton-Hunter-[Sar9, Met(O2)11]substance p, a selective radio-ligand for the NK1 receptor, to binding sites in rat subman-dibular gland membranes (IC50 1.6 ± 0.3 nM; n = 5). It is concluded that ranakinin is a preferred agonist for the mammalian NK1 tachykinin receptor subtype.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1991.tb06426.x
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  • 6
    Electronic Resource
    Electronic Resource
    Excitonic optical nonlinearity induced by internal field screening in (211) oriented strained-layer superlattices (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 684-686 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nonlinear optical properties of a new class of strained-layer superlattices (intrinsic Stark effect superlattices) have been investigated. Specifically, we have compared the nonlinear transmission of Ga1−xInxAs-GaAs strained-layer superlattices grown along the (211) axis to identical superlattices grown along the (100) axis, and found that the optical nonlinearity in the (211) sample is about one order of magnitude greater than in the (100) sample. A blue shift of the exciton resonance and an increase in the exciton absorption strength in the (211) sample with increasing light intensity was observed (attributed to screening of the intrinsic Stark effect fields by photogenerated carriers), resulting in the stronger optical nonlinearity. The maximum of the nonlinear absorption index, ||α2||, in the (211) sample was 54 cm/W (||Im χ3||=0.33 esu) whereas in the (100) sample the maximum of ||α2|| was 6.9 cm/W (||Im χ3||=0.042 esu). The measured carrier recovery time in both samples was 2 ns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104568
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    A maternal death caused by AIDS. Case report (1991)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 98 (1991), S. 0 
    Details
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-0528.1991.tb13465.x
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  • 8
    Electronic Resource
    Electronic Resource
    Far-infrared photoresponse of the InAs/GaInSb superlattice (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 846-848 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe the growth and characterization of the InAs/GaInSb superlattice on GaSb substrates. We present far-infrared (λ∼10 μm) photoabsorption and photoconductivity spectra which are in good agreement with theoretical predictions for the photoresponse of this spatially indirect superlattice. We report time-resolved photoconductivity measurements in which two response times are observed. We interpret the fast, 2 ns decay as resulting from electron-hole recombination via deep defect levels and the slow, 2 μs decay as resulting from recombination of a small fraction of the photogenerated minority carriers which become trapped at a defect site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105255
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Epitaxy of LiF on Ge(100) (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 2174-2176 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is shown that LiF(100) films with the electronic properties of cleaved bulk LiF crystals can be grown epitaxially on Ge(100). These include an exceptionally large, negative electron affinity of −2.7 eV, which leads to intense photoemission at zero kinetic energy. The valence band offset ranges from 7.3–7.6 eV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106091
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  • 10
    Electronic Resource
    Electronic Resource
    Electrooptic modulation in polar growth axis InGaAs/GaAs multiple quantum wells (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 1711-1713 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present electrooptic modulation results on [100], [211]A and [211]B oriented InGaAs/GaAs multiple quantum wells. Internal electric fields are generated by a combination of strain, due to lattice mismatch, and the piezoelectric properties of III-V semiconductors in the [211] structures. These fields have opposite orientation in the [211]A and [211]B samples. They do not occur in the [100] samples. The total electric field is a superposition of the strain-generated field, the built-in field from the p-n junction and any externally applied field. We show that whereas in the conventional [100] structures the exciton energy is a quadratic function of applied field, the strain-generated fields cause a linear shift in the exciton resonance with applied field in the [211] structures. In addition, the direction of the excitonic shift is opposite in the [211]A and [211]B samples, because the sign of the strain-generated fields are opposite for these samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106226
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