Three-dimensional imaging of YB56 by high-resolution electron microscopyElectronic supplementary information (ESI) available: Table S1: three-dimensional amplitudes and symmetrized phases of YB56 in Fourier transform derived by crystallographic image processing of HREM images, and amplitudes obtained from electron diffraction patterns. See http://www.rsc.org/suppdata/cc/b1/b107864j/

2002 ◽  
pp. 302-303 ◽  
Author(s):  
Takeo Oku
2001 ◽  
Vol 16 (1) ◽  
pp. 101-107 ◽  
Author(s):  
Takeo Oku ◽  
Jan-Olov Bovin ◽  
Iwami Higashi ◽  
Takaho Tanaka ◽  
Yoshio Ishizawa

Atomic positions for Y atoms were determined by using high-resolution electron microscopy and electron diffraction. A slow-scan charge-coupled device camera which had high linearity and electron sensitivity was used to record high-resolution images and electron diffraction patterns digitally. Crystallographic image processing was applied for image analysis, which provided more accurate, averaged Y atom positions. In addition, atomic disordering positions in YB56 were detected from the differential images between observed and simulated images based on x-ray data, which were B24 clusters around the Y-holes. The present work indicates that the structure analysis combined with digital high-resolution electron microscopy, electron diffraction, and differential images is useful for the evaluation of atomic positions and disordering in the boron-based crystals.


2015 ◽  
Vol 21 (S3) ◽  
pp. 1095-1096
Author(s):  
Jian-Min Zuo ◽  
Yifei Meng ◽  
Piyush Vivek Deshpande ◽  
Yang Hu ◽  
Kyou-Hyun Kim ◽  
...  

Author(s):  
Fang-hua Li

AbstractA simple image contrast theory in high-resolution electron microscopy (HREM) is introduced to demonstrate that below a certain critical crystal thickness the intensity of the Scherzer focus image is linear to the projected potential of an artificial crystal that is isomorphic to the examined one. It has become the theoretical base of electron crystallographic image processing techniques relying on the weak-phase-object approximation and kinematical diffraction. Two techniques of image processing are introduced. One of them aims at determining crystal structures by combining electron diffraction data and applying diffraction analysis methods. To reduce various kinds of electron diffraction intensity distortion the diffraction data are corrected by means of an empirical method set up by referring to the heavy atom method and Wilson statistic. The other one aims at revealing crystal defects at atomic resolution from the image taken with a medium-voltage field-emission high-resolution electron microscope. The dynamical effect is corrected by forcing the integral amplitudes of reflections in the diffractogram of image equal to the amplitudes of corresponding structure factors for the perfect crystal. The principle of the two techniques is briefly introduced, and examples of applications to crystal structure and defect determination are given.


Author(s):  
Kenneth H. Downing ◽  
Robert M. Glaeser

The contrast observed in images of beam-sensitive, crystalline specimens is found to be significantly less than one would predict based on observations of electron diffraction patterns of the specimens. Factors such as finite coherence, inelastic scattering, and the limited MTF of the photographic emulsion account for some decrease in contrast. It appears, however, that most of the loss in signal is caused by motion of the specimen during exposure to the electron beam. The introduction of point and other defects in the crystal, resulting from radiation damage, causes bending and lateral motion, which degrade the contrast in the image. We have therefore sought to determine whether the beam-induced specimen motion can be reduced by reducing the area of the specimen which is illuminated at any one time.


Materials containing planar boundaries are of general interest and complete understanding of their structures is important. When direct imaging of the boundaries by, for instance, high-resolution electron microscopy, is impracticable, details of their structure and arrangement may be obtained from electron diffraction patterns. Such patterns are discussed in terms of those from intergrowth tungsten bronzes as specific examples. Fourier-transform calculations for proposed structures have been made to establish, in conjunction with optical-diffraction analogues, the features of the far-field diffraction patterns. These results have been compared with diffraction patterns obtained experimentally by transmission electron microscopy. The aim of the study, to show that the arrangement of the boundaries in these complicated phases can be deduced from their diffraction patterns without the need for high-resolution imaging, has been achieved. The steps to be taken to make these deductions are set out.


Author(s):  
K. Hiraga ◽  
D. Shindo ◽  
M. Hirabayashi ◽  
T. Oikawa ◽  
N. Mori ◽  
...  

The “Imaging Plate” (IP) has three superior characteristics, i.e., high sensitivity to the electron beam, and a wide dynamic range and good linearity for electron dose compared with conventional EM films. The use of the IP is expected to lead to quantitative analysis of electron microscopy. The purpose of the present work is to examine the possibility of application of the IP to the quantitative analysis of electron diffraction and high-resolution electron microscopy.By using the TEM-IP System developed by Oikawa et al., which is published in this conference, electron diffraction patterns and high-resolution electron micrographs taken on the IP with an effective size of 102 х 77 mm2 were convertedinto digital data of 2048 х 1536 pixels with 4096 gray levels. Observations of electron diffraction patterns and high-resolution electron micrographs were made with a 200 kV (JEM-2000FX) and a 400 kV (JEM-4000EX) electron microscope, respectively.


Author(s):  
Kenneth A. Taylor

Recently, a method has been developed in this laboratory for maintaining the hydration of biological materials by using frozen specimens. With this technique specimens are prepared using folding grids on which are mounted composite support films of carbon and SiO. The technique essentially embeds the biological material in a thin aqueous film between the two supporting films. The sandwiched specimens are then frozen directly in liquid nitrogen. While it was thought at first that freezing directly in liquid nitrogen might cause disordering of periodic or crystalline biological specimens, this has been shown not to be the case. High resolution electron diffraction patterns have been obtained from frozen unstained catalase crystals.The microscopy of frozen specimens depends on their resistance to damage by electron irradiation. The critical exposure for fading of the electron diffraction intensities from frozen unstained catalase crystals has been measured.


Author(s):  
W. F. Tivol ◽  
J. H. Kim

Collection of a three-dimensional data set from anthracene illustrates some of the difficulties which can be encountered. Since the crystals are grown from solution their orientation is not certain, and the crystals are very bendy, so a range of orientations is encountered at a given tilt setting. Anthracene is moderately labile to irradiation, so care must be taken to avoid radiation damage during data collection. Anthracene will sublime at room temperature under vacuum, so the data must be collected at reduced temperature. Flat, well-ordered areas of the crystals are rare, so collection of high-resolution data is time-consuming. The thickness of the crystals is difficult to control, so finding areas which have minimal multiple scattering is also formidable.The structure of anthracene is already known, so simulations of the diffraction patterns along various zone axes can be made. Cerius 2.0® was used to produce simulated zone axis patterns for all combinations of indices whose absolute values were 3 or less. The preferred orientation for the untilted grid is [102]. Scans of several preparations resulted in patterns which matched the simulation for [102]. The angles for each of the Miller planes with respect to [102] were calculated from the formula given by Dorset.


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