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  • 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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  • 2
    Electronic Resource
    Electronic Resource
    Improved instrument for medium energy electron diffraction and microscopy of surfaces (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1215-1219 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The REMEDIE system for reflection electron microscopy and electron diffraction at intermediate energies (0.5–20 keV) has been rebuilt with an improved imaging resolution of better than 10 nm, a convenient and versatile system for observation diffraction patterns and provision for specimen preparation and treatment suitable for surface structural studies. The current capabilities of the instrument are illustrated by results obtained from cleaved and annealed silicon (111) surfaces with or without thin deposited silver and gold layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1137978
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  • 3
    Electronic Resource
    Electronic Resource
    High Resolution Electron Microscopy (1987)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Physical Chemistry 38 (1987), S. 57-88 
    Details
    ISSN: 0066-426X
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.pc.38.100187.000421
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  • 4
    Electronic Resource
    Electronic Resource
    The structure of Pt particles on γ-Al2O3 support (1987)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 20 (1987), S. 300-305 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Samples of the catalyst Pt/γ-Al2O3 have been examined by high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM) and microdiffraction techniques. An epitaxic relationship of metallic Pt crystals on the γ-Al2O3 has been established. In both calcined and reduced samples, the crystalline oxide α-PtO2 was found along with metallic Pt. The oxide has a hexagonal lattice with unit-cell dimensions about 6% smaller than those previously reported. Microdiffraction from areas less than 20 Å in diameter, combined with HRTEM, STEM and secondary electron microscopy (SEM), has proved to be a very powerful technique for the study of the structures of particles less than 50 Å in size.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889887086631
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  • 5
    Electronic Resource
    Electronic Resource
    High-voltage transmission scanning electron microscopy (1970)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 3 (1970), S. 49-59 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The use of scanning electron microscopy for the study of thin specimens by transmission has advantages over conventional transmission electron microscopy in terms of simplicity and cheapness, reduction in damage to irradiation-sensitive specimens and convenience for electron diffraction, energy analysis and the electronic measurement and recording of images. These advantages are specially important for microscopes operating in the range 200 kV to 1 MeV. The design of a 600 kV instrument to exploit these advantages is described. The possible modes of operation employing deflexion systems and an energy analyser are discussed with reference to light- and dark-field microscopy, convergent beam diffraction and conventional focused diffraction patterns. The reciprocity principle is invoked to relate both image contrast and instrument design in scanning electron microscopy to that in conventional transmission electron microscopy. Examples are given of light- and dark-field images and diffraction patterns obtained with the instrument.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889870005642
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  • 6
    Electronic Resource
    Electronic Resource
    Line patterns in wide-angle convergent beam electron diffraction (1971)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 4 (1971), S. 482-487 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Wide-angle convergent-beam electron diffraction patterns from thin single crystals show sets of parallel lines somewhat similar to Kikuchi or Kossel lines. In some cases, each line separates into a black and white line pair when the electron beam is defocused. It is shown that this separation depends on the curvature of the crystal. A method for analysis of the line geometry is proposed which takes into account the aberrations of the electron lens. Using a high-voltage transmission scanning electron microscope, through-focus series of patterns from graphite crystals have been obtained and analyzed to give values for the radius of curvature of the crystal. In defocussed patterns the distortions of the lattice by defects are clearly visible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889871007507
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  • 7
    Electronic Resource
    Electronic Resource
    Errors arising from numerical use of the Mott formula in electron image simulation (1988)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 44 (1988), S. 1-6 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The Mott formula relating the electron scattering factor to that for X-rays is inaccurate in its numerical form in the small-angle region. Effects of the inaccuracy on both kinematic and dynamical diffraction have been investigated. Some artifacts arising from the inaccuracy have been found in simulated electron microscopy images. A modified form for the Mott formula, which minimizes the error, is proposed. However, for any accurate and reliable calculation only those electron scattering factors derived directly from the atomic potential can be used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767387006858
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  • 8
    Electronic Resource
    Electronic Resource
    Electron microscopy of crystals with time-dependent perturbations (1988)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 44 (1988), S. 847-853 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The electron microscope image intensity of a thin crystal is described as a time average of the image of a crystal perturbed by time-dependent fluctuations corresponding to thermal motion of the atoms or low-energy electronic excitations. For very thin crystals the phase-object approximation indicates that images having atomic resolution may be obtained from the inelastically scattered electrons. It is shown that the use of suitable approximations allows estimates to be made of the contribution of the inelastically scattered electrons to the high-resolution images of thicker crystals. The resolution of images formed by inelastically scattered electrons is not affected by the non-localization of the inelastic scattering process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767388004751
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  • 9
    Electronic Resource
    Electronic Resource
    Dynamical diffraction calculations for RHEED and REM (1986)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 42 (1986), S. 545-552 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The multislice formulation of the many-beam dynamical diffraction theory has been applied to the Bragg case of electron diffraction for the extended surface of a perfect crystal and also for a crystal surface with a surface step. The wavefunctions within and outside the crystal have been calculated and used to derive the standing-wave pattern in the top atomic layers of the crystal, the intensities of the reflection high-energy electron diffraction (RHEED) pattern and the contrast of the reflection electron microscopy (REM) image. Calculations made for the diffraction of 19, 40 and 80 keV electrons from (111) surfaces of Pt and Au demonstrate the channeling of electrons under the conditions of surface resonance, the perturbation of the standing-wave field in the crystal by a one-atom-high surface step and the REM contrast for a through-focus series of images of a surface step. The method is applicable to models including surface relaxations and reconstructions and any kind of local defect of the surface or of the bulk crystal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767386098756
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  • 10
    Electronic Resource
    Electronic Resource
    The present and future of high-resolution electron microscopy (1987)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 43 (1987), S. 737-751 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: High-resolution electron microscopy, with the current resolution limits of better than 2 Å, has been proven to be a valuable technique for the study of radiation-resistant crystals, allowing the determination of the structures of perfect crystal regions, crystal defects and crystal surfaces with atomic resolution. As the resolution is improved, however, the image contrast is increasingly determined by dynamical diffraction effects and it is increasingly sensitive to the instrumental parameters and to the geometry and alignment of the specimen. For both the conventional transmission electron microscope and the scanning transmission electron microscope, further developments should lead to better or more versatile performance, up to the limits set by the fundamental problems of radiation damage. Major advances may be expected from developments of the associated techniques of microanalysis and microdiffraction. Applications of particular interest will include studies of surfaces and interfaces, small particles and radiation-induced chemical reactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S010876738709857X
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