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  • 1985-1989  (3)
  • 1945-1949
  • 1989  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Determination of the local Al concentration in AlxGa1−xAs-GaAs quantum well structures using the (200) diffraction intensity obtained with a 10 A(ring) electron beam (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1454-1456 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel method for determining the local concentration of Al in the AlxGa1−xAs layer of AlxGa1−xAs-GaAs multiple quantum well structures is reported. By scanning a 10 A(ring) electron beam across the interface, the (200) dark-field scanning transmission electron microscopy (STEM) image shows the contrast of the AlxGa1−xAs-GaAs multilayer since the intensity of the (200) diffraction is sensitive to the Al concentration. The line scan intensity profile of the (200) diffraction, along a uniform specimen region of known thickness, shows the intensity variation of the (200) diffraction and reflects the local content of Al in each region. The simulation of the nanodiffraction patterns produces a chart of the (200) diffraction intensity versus the Al concentration for the determination of the local change of the Al concentration. A molecular beam epitaxy grown AlxGa1−xAs-GaAs specimen (x=0.57 as determined from Raman spectroscopy) is tested and the dark-field STEM studies show two thin layers of x=0.46 at the 1/3 and 2/3 height level within every AlxGa1−xAs layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100695
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Electron inelastic plasmon scattering and its resonance propagation at crystal surfaces in RHEED (1989)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 45 (1989), S. 325-333 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The modified multislice theory [Wang (1989). Acta Cryst. A45, 193-199] has been employed to calculate the electron reflection intensity with and without considering the plasmon diffuse scattering in the geometry of reflection high-energy electron diffraction (RHEED). It has been shown that the inelastic scattering can greatly enhance the reflectance of a surface, depending critically on the incident conditions of the electrons. At some incidences, the inelastic resonance reflection is enhanced, which is considered as the 'true' surface resonance state. This happens within a very narrow angular range (〈1 mrad). For 'true' resonance states, the inelastic intensity is much stronger than for other conditions as shown both theoretically and experimentally. The enhancement of the reflection intensity may not be the proper criterion for identifying the 'true' surface resonance. Besides the surface plasmon peaks, an 'extra' peak, located at 4.5 eV, is observed in the reflection electron energy-loss spectroscopy (REELS) study of the 'true' resonance of GaAs (110) surface. This is considered as a characteristic of the resonance propagations of the electrons along the surface and may result from the generation of resonance radiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767388014539
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Observation of microdiffraction patterns with a dedicated STEM instrument (1989)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 11 (1989), S. 143-154 
    Details
    ISSN: 0741-0581
    Keywords: Detector systems for microdiffraction ; STEM imaging ; Coherent diffraction effects ; Image reconstruction from diffraction patterns ; EELS ; SEM ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A two-dimensional detector system, designed for the observation and recording of microdiffraction patterns formed in an HB 5 scanning transmission electron microscope (STEM) is described and discussed. Possibilities are described and demonstrated for the simultaneous or successive recording of microdiffraction patterns from regions of diameter 3 å or more, bright- or dark-field STEM images, EELS spectra, secondary electron images, and in-line holograms. Applications of the system have been made to studies of catalyst particles, reflection-mode imaging of bulk surfaces, and image reconstruction from microdiffraction patterns obtained from each point of a STEM image.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060110209
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    Paper (German National Licenses)
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