An Interactive Minicomputer Program for the Indexing and Simulation of Electron Diffraction Patterns

Computer programs are now available in various laboratories for the indexing and simulation of transmission electron diffraction patterns. Although these programs address themselves to the solution of various aspects of the indexing and simulation process, the ultimate goal is to perform real time diffraction pattern analysis directly off of the imaging screen of the transmission electron microscope. The program to be described in this paper represents one step prior to real time analysis. It involves the combination of two programs, described in an earlier paper(l), into a single program for use on an interactive basis with a minicomputer. In our case, the minicomputer is an INTERDATA 70 equipped with a Tektronix 4010-1 graphical display terminal and hard copy unit.A simplified flow diagram of the combined program, written in Fortran IV, is shown in Figure 1. It consists of two programs INDEX and TEDP which index and simulate electron diffraction patterns respectively. The user has the option of choosing either the indexing or simulating aspects of the combined program.

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Real time analysis of self-assembled InAs/GaAs quantum dot growth by probing reflection high-energy electron diffraction chevron image

Journal of Applied Physics ◽

10.1063/1.2987469 ◽

2008 ◽

Vol 104 (7) ◽

pp. 074305 ◽

Cited By ~ 17

Author(s):

Takuya Kudo ◽

Tomoya Inoue ◽

Takashi Kita ◽

Osamu Wada

Keyword(s):

Electron Diffraction ◽

Quantum Dot ◽

Real Time ◽

High Energy ◽

Energy Electron ◽

High Energy Electron ◽

Time Analysis ◽

Real Time Analysis ◽

Self Assembled ◽

Gaas Quantum Dot

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Real time analysis of diffraction patterns, at extremely low light levels

Optics and Lasers in Engineering ◽

10.1016/0143-8166(94)90051-5 ◽

1994 ◽

Vol 21 (5) ◽

pp. 317-325 ◽

Cited By ~ 2

Author(s):

C. Ciamberlini ◽

G. Longobardi

Keyword(s):

Real Time ◽

Time Analysis ◽

Low Light ◽

Real Time Analysis ◽

Light Levels ◽

Diffraction Patterns

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A library of convergent-beam electron diffraction patterns

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100144826 ◽

1986 ◽

Vol 44 ◽

pp. 688-691

Author(s):

John F. Mansfield

Keyword(s):

Electron Diffraction ◽

Materials Science ◽

Convergent Beam Electron Diffraction ◽

Beam Electron ◽

Transmission Electron ◽

Yield Information ◽

Analytical Electron ◽

Diffraction Patterns ◽

Convergent Beam ◽

Electron Energy Loss

One of the most important advancements of the transmission electron microscopy (TEM) in recent years has been the development of the analytical electron microscope (AEM). The microanalytical capabilities of AEMs are based on the three major techniques that have been refined in the last decade or so, namely, Convergent Beam Electron Diffraction (CBED), X-ray Energy Dispersive Spectroscopy (XEDS) and Electron Energy Loss Spectroscopy (EELS). Each of these techniques can yield information on the specimen under study that is not obtainable by any other means. However, it is when they are used in concert that they are most powerful. The application of CBED in materials science is not restricted to microanalysis. However, this is the area where it is most frequently employed. It is used specifically to the identification of the lattice-type, point and space group of phases present within a sample. The addition of chemical/elemental information from XEDS or EELS spectra to the diffraction data usually allows unique identification of a phase.

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Structural studies of small amorphous volumes by electron diffraction

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100173741 ◽

1990 ◽

Vol 48 (4) ◽

pp. 122-123

Author(s):

Pierre Moine

Keyword(s):

Electron Diffraction ◽

Born Approximation ◽

Structural Information ◽

Fundamental Relation ◽

X Rays ◽

Structural Studies ◽

Diffraction Experiment ◽

Transmission Electron ◽

Amorphous Structures ◽

Diffraction Patterns

Qualitatively, amorphous structures can be easily revealed and differentiated from crystalline phases by their Transmission Electron Microscopy (TEM) images and their diffraction patterns (fig.1 and 2) but, for quantitative structural information, electron diffraction pattern intensity analyses are necessary. The parameters describing the structure of an amorphous specimen have been introduced in the context of scattering experiments which have been, so far, the most used techniques to obtain structural information in the form of statistical averages. When only small amorphous volumes (< 1/μm in size or thickness) are available, the much higher scattering of electrons (compared to neutrons or x rays) makes, despite its drawbacks, electron diffraction extremely valuable and often the only feasible technique.In a diffraction experiment, the intensity IN (Q) of a radiation, elastically scattered by N atoms of a sample, is measured and related to the atomic structure, using the fundamental relation (Born approximation) : IN(Q) = |FT[U(r)]|.

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A Structural Model for a Quasi-Crystalline Material Derived from TEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100178999 ◽

1990 ◽

Vol 48 (1) ◽

pp. 48-49

Author(s):

Jan-Olov Bovin ◽

Osamu Terasaki ◽

Jan-Olle Malm ◽

Sven Lidin ◽

Sten Andersson

Keyword(s):

High Resolution ◽

Electron Diffraction ◽

Structural Model ◽

Image Intensifier ◽

Crystalline Materials ◽

Icosahedral Phases ◽

Transmission Electron ◽

Electron Microscopes ◽

Diffraction Patterns ◽

Quasi Crystals

High resolution transmission electron microscopy (HRTEM) is playing an important role in identifying the new icosahedral phases. The selected area diffraction patterns of quasi crystals, recorded with an aperture of the radius of many thousands of Ångströms, consist of dense arrays of well defined sharp spots with five fold dilatation symmetry which makes the interpretation of the diffraction process and the resulting images different from those invoked for usual crystals. The atomic structure of the quasi crystals is not established even if several models are proposed. The correct structure model must of course explain the electron diffraction patterns with 5-, 3- and 2-fold symmetry for the phases but it is also important that the HRTEM images of the alloys match the computer simulated images from the model. We have studied quasi crystals of the alloy Al65Cu20Fe15. The electron microscopes used to obtain high resolution electro micrographs and electron diffraction patterns (EDP) were a (S)TEM JEM-2000FX equipped with EDS and PEELS showing a structural resolution of 2.7 Å and a IVEM JEM-4000EX with a UHP40 high resolution pole piece operated at 400 kV and with a structural resolution of 1.6 Å. This microscope is used with a Gatan 622 TV system with an image intensifier, coupled to a YAG screen. It was found that the crystals of the quasi crystalline materials here investigated were more sensitive to beam damage using 400 kV as electron accelerating voltage than when using 200 kV. Low dose techniques were therefore applied to avoid damage of the structure.

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