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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 39 (1983), S. 422-422 
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: As a result of a printer's error, Figs. 9(a) and 9(b) in Smith & O'Keefe [Acta Cryst. (1983), A39, 139-148] have been transposed, so that (a) is labelled (b) and (b) is labelled (a).
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 39 (1983), S. 139-148 
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The conditions appropriate for direct structure imaging of silicon carbide polytypes in the high-resolution electron microscope have been investigated. Weak-phase-object calculations confirm that a resolution of better than 2.5 Å is necessary before polytypic stacking sequences can be identified directly. Furthermore, resolutions closely approaching 1 Å are required to resolve projected pairs of Si-C atoms, and considerably better than 1 Å is necessary to differentiate between the two species. Extensive multi-slice calculations, based on both current and projected electron-optical characteristics, show that polytype stacking should be recognizable at 500 kV up to thicknesses of 45-75 Å, but not at 100 kV, except possibly at the 'reversed' Scherzer defocus position with extremely coherent illumination. The occurrence of Fourier images complicates recognition of the correct objective-lens defocus particularly for thin crystals of the 3C polytype. In thicker-crystal regions (≥ 100 Å), where linear image contributions are small, mutual interference between diffracted beams results generally in polytype images of apparently improved resolution and, at specific thickness and defocus values, leads to images of 3C resembling the 'atom-pair' configuration. The latter are then explained by consideration of the image amplitude and intensity spectra. Finally, the problems of recovering specimen structure from crystals of intermediate thickness, as well as some of the factors affecting any quantitative experimental studies, are briefly discussed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 43 (1987), S. 737-751 
    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
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 35 (1979), S. 916-923 
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Lattice imaging with tilted illumination at the 2.5 Å level has been used for the direct determination of stacking sequences in silicon carbide polytypes by observation of electron micrographs. The method employed is first demonstrated by observations of the common short-period polytypes 3C, 4H, 15R and 6H, and is then used to reveal the stacking sequences in the polytypes 9R and 129R, neither of which appear to have been reported previously. Stacking sequences in disordered and faulted materials have also been characterised.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 37 (1981), S. 273-280 
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The feasibility of direct structure imaging of pyroxenoid chain silicates by high-resolution electron microscopy at 500 kV is demonstrated both experimentally and theoretically for the minerals wollastonite, CaSiO3, and rhodonite, MnSiO3. Image simulations with a simplified multi-slice approach indicated that the crystal projection most suitable for direct observation of the tetrahedral chain arrangement corresponded to the overlap of the metal cations with the tetrahedral sites, a situation which occurs in all pyroxenoids. Electron micrographs were also obtained, with bright- field axial illumination at 500 kV, which could be closely matched with the simulated images, at least for very thin crystal regions. The implications of these results, in particular for studies at the atomic level of solid-state transformations involving the pyroxenoids, are briefly discussed.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 37 (1981), S. 119-125 
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The ferroelectric material Ba2Bi4Ti5O18 has been examined by high-resolution electron microscopy at 200 and 500 kV. With the directly interpretable resolution limit in each case extending to better than 2.5 Å, it was demonstrated that both the A-cation and B-cation positions could be resolved and, furthermore, that analysis of structural disorder at this level of resolution allowed an explanation of some observed lattice defects. In particular, unit shifts of a perovskite cell along a bismuthate sheet were identified as occurring in the manner previously postulated, and a Burgers vector circuit analysis around a low-angle domain boundary permitted the formulation of a model for the atomic configuration at the boundary. The implications of these observations for the study of perovskites generally are briefly discussed.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 39 (1983), S. 838-847 
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Computer-simulated electron-microscope images have been produced for several different aromatic hydrocarbons, as well as the organometallic compound chlorinated copper phthalocyanine. Weak-phase-object images are compared with full multislice imaging calculations that include the resolution-limiting effects of limited spatial and temporal coherence; the comparisons indicate a considerable range of focus and thickness where intuitive image interpretation is possible. This favourable situation arises directly from the low atomic numbers of the atoms comprising the molecules and the almost monotonic fall-off with scattering angle of those structure factors within the resolution limit of the microscope. The occurrence and nature of both first- and second-order resolution-limiting effects on typical 100 and 500 kV images is also discussed.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Nuclear Physics, Section B 349 (1991), S. 168-206 
    ISSN: 0550-3213
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 2279-2285 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: KDP, KD*P, and LiNbO3, three nonlinear optical materials that have been difficult to coat, are treated with polymeric surface layers. These layers hermetically seal the hygroscopic crystal surfaces. Their optical properties, thermal compatibility, high-power laser damage behavior, abrasive resistance, and suitability for overcoating with traditional, dielectric antireflection multilayers are reported.
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  • 10
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 4003-4007 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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