摘要:

AbstractThe theory of high‐energy electron diffraction is reviewed, with an emphasis on methods that help most in understanding the form of zone axis convergent‐beam patterns. A Bloch wave description is used throughout the paper, and the theory is formulated in real space, leading to general expressions for both zero‐layer and higher‐order Laue zone (HOLZ) diffraction amplitudes. HOLZ diffraction is discussed in detail, and it is shown that first‐order perturbation theory is usually applicable and provides a clear picture of the diffraction. The computation of diffracted intensities is discussed with reference to the many‐beam equations. Diffraction at the [0001] axis in 1T‐VSe2is analysed both to illustrate the theory and to provide an example of the special effects that occur at well defined str

ISSN:0741-0581    

DOI:10.1002/jemt.1060130202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractConvergent‐beam electron diffraction provides more precise measurements of diffracted intensity than the traditional method of selected‐area diffraction. The intensity is recorded at well‐defined beam directions for each reflection in the pattern within disks defined by the incident cone of rays. Measurements relating to structure factors or parameters can be arranged in different ways: intensities at the zone axis position; Kossel line profiles or integrated intensities across Kossel lines; conditions for vanishing contrast at a Kossel line (e.g., critical voltage); separation between Kossel line segments at intersections. Examples of application to refinement of structure parameters (zone axis intensities) and structure factor determination (Kossel line methods) are given.The relation of these magnitudes to theory is discussed, especially for the Kossel line methods. These are described in terms of effective Fourier potentials or gaps at the Bloch‐wave dispersion surface. Use of the methods for refinement of structure parameters and structure factors is reviewed with special attention to recent developments. This is seen along two lines: (1) extended scope for the more accurate methods in order to cover larger unit cells and (2) better precision in measurements of inte

ISSN:0741-0581    

DOI:10.1002/jemt.1060130203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThis paper explains how the convergent beam electron diffraction (CBED) and large angle convergent beam (LACBED) techniques can be used to study crystal defects, bicrystals, and multilayers. It is shown how the LACBED technique in particular can be used to derive the magnitude and sign of the Burgers vectors of dislocations and displacements at stacking faults. For bicrystals and multilayers examined in plan‐view, LACBED gives the rocking curve for a chosen reflection. This enables layer strains to be measured to ∼ 0.1% and composition profiles derived for both periodic and aperiodic structures. It is shown that a simple kinematic approach can be used to interpret the essential results in most ca

ISSN:0741-0581    

DOI:10.1002/jemt.1060130204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThis article has been written for experimenters who are beginning to work with convergent beam electron diffraction patterns (CBED). The indexing of the higher‐order Laue zone (HOLZ) lines inside the central spot of a CBED pattern is the first step towards studying variations in lattice parameter and three‐dimensional (3D) symmetry. To index the HOLZ lines one must construct and index the HOLZ, find its interplanar spacing and the location of its projection on the zero order Laüe zone (ZOLZ) for a given zone axis, and finally find the radius of the HOLZ ring. A computer program has been developed to perform all these tasks for cubic crystals and is very useful, especially when one varies parameters such as operating voltage, zone axis, lattice parameter, and crystalline struc

ISSN:0741-0581    

DOI:10.1002/jemt.1060130205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

ISSN:0741-0581    

DOI:10.1002/jemt.1060130206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

ISSN:0741-0581    

DOI:10.1002/jemt.1060130207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

ISSN:0741-0581    

DOI:10.1002/jemt.1060130208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

ISSN:0741-0581    

DOI:10.1002/jemt.1060130209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

ISSN:0741-0581    

DOI:10.1002/jemt.1060130201

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY