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  • 1990-1994  (7)
  • 1994  (4)
  • 1993  (3)
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  • 1990-1994  (7)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Reflection high energy electron diffraction observation of anion exchange reactions on InAs surfaces (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 259-262 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have used time-resolved reflection high energy electron diffraction (RHEED) measurements to study anion exchange reactions in molecular beam epitaxy (MBE) grown III-V semiconductors. In the experiment, InAs surfaces are exposed to Sbx fluxes and subsequent changes in the crystals RHEED patterns are examined. We find that when an InAs surface is initially exposed to an Sb flux the specular spot intensity first decreases, then recovers back toward its initial value. The shape of the intensity versus time curves is extremely reproducible if the absolute Sb flux and the Sb species are kept constant. The length of time required for the RHEED pattern to stabilize is much shorter for cracked Sb than for uncracked Sb. The RHEED dynamics are also faster if the total Sb flux increases. The behavior of the RHEED dynamics as a function of Sb flux and Sb species is consistent with the changes in the RHEED pattern being due to an Sb/As exchange reaction on the crystal's surface. The RHEED data are compared to previously published x-ray photoelectron spectroscopy (XPS) data which studied exchange reactions on InAs surfaces exposed to Sb fluxes. The XPS study confirmed that the incident Sb did indeed exchange with As in the epilayer and estimated the exposure time needed to complete the Sb/As exchange reaction. The time scales for exchange associated with the RHEED and XPS data are in good agreement. This further indicates that RHEED could be used to indirectly probe anion exchange reactions, potentially opening up several avenues of research ranging from basic materials science to MBE process control in manufacturing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355893
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Determination of acoustic phonon dispersion curves in layer silicates by inelastic neutron scattering and computer simulation techniques (1993)
    Springer
    Physics and chemistry of minerals 19 (1993), S. 520-527 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Inelastic neutron scattering and computer modelling techniques have been used to study acoustic phonons in several layer silicate minerals. Experimental measurements have been made on four layer silicate minerals; namely samples of muscovite, Fe-bearing muscovite, margarite and chlorite. The longitudinal acoustic modes propagating along the [0, 0, ξ] direction of muscovite and Fe-bearing muscovite were found to be the same, within experimental error. The longitudinal and transverse acoustic modes propagating along [0, 0, ξ] of muscovite have been calculated using computer simulation techniques based on lattice dynamics. The experimental and calculated longitudinal modes of muscovite are in excellent agreement, thereby demonstrating the complementary nature of both techniques. The shape of both experimental and calculated dispersion curves was found to be approximately sinusoidal, indicating that interatomic forces act principally between nearest-neighbour atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203052
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Programs for phasing by entropy maximization as implemented in Xtal3.2: a crystallographic software system (1993)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 49 (1993), S. 100-106 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Xtal3.2, a crystallographic software package, is an international development project involving about 40 researchers over a full spectrum of crystallographic interests. This development has been supported by many national and international agencies and commercial institutions since the first version in 1983. The 1992 release, Xtal3.2, contains software for 95 different calculations. These range from the processing of raw diffraction data to interactive molecular graphics, atomic charge estimation, electronic publication preparation, and the structure solution and refinement of small and large molecules. Tests of the Xtal programs for phase determination and phase refinement by the application of `maximum entropy' are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444992008898
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Entropy on charge density: making the quantum mechanical connection (1993)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 49 (1993), S. 86-89 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Entropy maximization has proven effective in treating certain aspects of the phase problem of X-ray diffraction. Much of its development has been expressed in probabilistic language, although image enhancement has been somewhat more physical or geometric in description. Here phasing and entropy maximization are embedded in the quantum mechanical problem of reconstructing an electronic one-matrix under experimental constraints. Entropy on an N-representable one-particle density matrix is well defined. The entropy is the expected form, and it is a simple function of the one-matrix eigenvalues which all must be non-negative. Certain other properties are pertinent to phasing which is implicit in one-matrix reconstruction governed by entropy maximization. Throughout this work reference is made to informational entropy, not the entropy of thermodynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444992009429
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    Paper (German National Licenses)
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  • 5
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    Sibirica, the Journal of Siberian Studies (Book Review) (1994)
    London, etc. : Periodicals Archive Online (PAO)
    Slavonic and East European review. 72:4 (1994:Oct.) 763 
    Details
    ISSN: 0037-6795
    Topics: History , Slavonic Studies
    Notes: REVIEWS
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:0072-1994-072-04-000056
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Growth series for the group 〈x,y¦x −1 yx=y l 〉 (1994)
    Springer
    Archiv der Mathematik 62 (1994), S. 1-11 
    Details
    ISSN: 1420-8938
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01200431
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    Paper (German National Licenses)
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  • 7
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    Dune, E. M. "Notes of a Red Guard" (Book Review) (1994)
    London, etc. : Periodicals Archive Online (PAO)
    Slavonic and East European review. 72:4 (1994:Oct.) 748 
    Details
    ISSN: 0037-6795
    Topics: History , Slavonic Studies
    Notes: REVIEWS
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:0072-1994-072-04-000044
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    Paper (German National Licenses)
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