Refinement of rigid shift component normal to a Σ5 grain boundary in rutile by quantitative HREM

1995 ◽  
Vol 53 ◽  
pp. 570-571
Author(s):  
S. Paciornik ◽  
D. Michel ◽  
U. Dahmen
Keyword(s):  
High Resolution ◽  
Grain Boundary ◽  
Rigid Body ◽  
Boundary Plane ◽  
Sufficient Accuracy ◽  
Atomic Relaxation ◽  
High Resolution Images ◽  
Diffraction Patterns ◽  
Macroscopic Parameters

In contrast to the macroscopic parameters of a grain boundary, its microscopic parameters are difficult to determine with sufficient accuracy to make critical comparisons between models and experimental observations. Whereas the axis and angle of misorientation and the orientation of the boundary plane are easily measured from diffraction patterns or high resolution images, the rigid body shift and the localized atomic relaxation are far more complicated to determine and are more sensitive to image or sample artifacts. Yet it is only these microscopic parameters that differentiate the behavior of the same crystallographic interface in different materials. While the angle of misorientation and the plane of inclination are fixed macroscopically, the rigid body shift and localized atomic relaxations depend directly on the type of bonding that characterizes a given material.Several methods for the measurement of rigid shifts at interfaces have been given recently. Their accuracy is limited by instrumental parameters such as beam tilt, sample tilt, residual two-and threefold astigmatism, specimen noise or twist components.

High resolution STEM imaging study on high Tc superconductor YBa2CuaO7-x

1988 ◽  
Vol 46 ◽  
pp. 882-883
Author(s):  
H.-J. Ou ◽  
J. M. Cowley
Keyword(s):  
Crystal Structure ◽  
High Resolution ◽  
Grain Boundary ◽  
Strong Field ◽  
Imaging Study ◽  
Structure Defects ◽  
High Tc ◽  
High Tc Superconductor ◽  
Diffraction Patterns ◽  
Lattice Planes

Using the dedicate VG-HB5 STEM microscope, the crystal structure of high Tc superconductor of YBa2Cu3O7-x has been studied via high resolution STEM (HRSTEM) imaging and nanobeam (∽3A) diffraction patterns. Figure 1(a) and 2(a) illustrate the HRSTEM image taken at 10' times magnification along [001] direction and [100] direction, respectively. In figure 1(a), a grain boundary with strong field contrast is seen between two crystal regions A and B. The grain boundary appears to be parallel to a (110) plane, although it is not possible to determine [100] and [001] axes as it is in other regions which contain twin planes [3]. Following the horizontal lattice lines, from left to right across the grain boundary, a lattice bending of ∽4° is noticed. Three extra lattice planes, indicated by arrows, were found to terminate at the grain boundary and form dislocations. It is believed that due to different chemical composition, such structure defects occur during crystal growth. No bending is observed along the vertical lattice lines.

Atomic structure of YB56 studied by digital high-resolution electron microscopy and electron diffraction

2001 ◽  
Vol 16 (1) ◽  
pp. 101-107 ◽  
Author(s):  
Takeo Oku ◽  
Jan-Olov Bovin ◽  
Iwami Higashi ◽  
Takaho Tanaka ◽  
Yoshio Ishizawa
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
High Resolution Electron Microscopy ◽  
Charge Coupled Device ◽  
X Ray ◽  
Resolution Electron ◽  
High Resolution Images ◽  
Diffraction Patterns ◽  
Simulated Images

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.

Analysis of Image Contrast in High-Resolution Images of n-Paraffin Recorded at 400 kV and -167°C

1990 ◽  
Vol 48 (1) ◽  
pp. 86-87
Author(s):  
J. Brink ◽  
W. Chiu
Keyword(s):  
High Resolution ◽  
Image Contrast ◽  
Depth Of Field ◽  
Spot Scanning ◽  
Structure Factors ◽  
Ewald Sphere ◽  
High Resolution Images ◽  
Resolution Imaging ◽  
Diffraction Patterns ◽  
Envelope Functions

Images of radiation-sensitive two-dimensional crystals quite often fail to display the same resolution visible in electron diffraction patterns of these crystals. It is now generally accepted that besides the microscope's envelope functions, radiation damage and the MTF of the film and cryo-holder, beam-induced specimen motion is a major contrast degrading factor. Minimization of this movement proved possible through use of narrow electron beams, i.e. in spot-scanning. Routine high resolution imaging, however, remains a difficult task. We have investigated the possibilities of enhancing the effeciency this goal by using 400 keV electrons. Based upon overall less attenuation from the envelope functions at 400 kV, structure factors at around 3Å resolution would show amplitudes easily twice as large as compared to 100 kV. Further, at 400 kV inelastic scattering would be reduced relative to 100 kV. Moreover, it has been suggested that image contrast would increase roughly proportional to β. Additional advantages concerning for instance Ewald sphere curvature and depth of field have been put forward in Chiu et al.

Ordering In Zn0.5Fe0.5Se Epilayers Grown on InP Substrates by Molecular Beam Epitaxy

1991 ◽  
Vol 231 ◽  
Author(s):  
L. Salamanca Riba ◽  
K. Park ◽  
B. T. Jonker
Keyword(s):  
High Resolution ◽  
Ordered Structure ◽  
Cross Sectional ◽  
Zinc Blende ◽  
Transmission Electron ◽  
Lattice Images ◽  
High Resolution Images ◽  
Diffraction Patterns ◽  
Inp Substrates ◽  
Image Simulations

AbstractWe have observed an ordered structure in Zn0.5Fe0.5Se epilayers grown on (001) InP substrates using transmission electron microscopy. The ordered structure of Zn0.5Fe0.5Se has Fe atoms occupying the (0,0,0) and (½, ½, 0) sites and Zn atoms occupying the (0, ½, ½) and (½, 0, ½) sites in the zinc-blende unit cell. Ordering is observed in both electron diffraction patterns and cross-sectional high-resolution lattice images along the < 100 > and < 110 > directions. This ordered structure consists of alternating ZnSe and FeSe monolayers along the < 100 > and < 110 > directions. Computer image simulations of the high-resolution images under various thicknesses, and defocusing conditions have been obtained and are compared with those obtained experimentally.

TEM Study of Quasicrystals in Al-Mn-Fe Melt-Spun Ribbon

2012 ◽  
Vol 186 ◽  
pp. 255-258 ◽  
Author(s):  
Katarzyna Stan ◽  
Lidia Lityńska-Dobrzyńska ◽  
Jan Dutkiewicz ◽  
Lukasz Rogal ◽  
Anna Maria Janus
Keyword(s):  
High Resolution ◽  
Electron Diffraction ◽  
Crystallographic Direction ◽  
Fold Axis ◽  
Orientation Relationships ◽  
Melt Spun ◽  
High Resolution Images ◽  
Different Shapes ◽  
Diffraction Patterns ◽  
Rapidly Solidified

Microstructure of rapidly solidified Al91Mn7Fe2 (at.%) alloy was investigated using SEM and TEM techniques. Quasicrystalline particles of different shapes and sizes embedded in the aluminium matrix were observed. Quasilattice constant was calculated as 0.461 Å. Additionally orientation relationships between matrix and quasicrystals particles were found based on electron diffraction patterns and high resolution images, such that: five-fold axis lie along [011] or [001] axes of the α-Al crystallographic direction.

High-resolution three-dimensional Coulomb potential map of PhoE porin

1992 ◽  
Vol 50 (1) ◽  
pp. 434-435
Author(s):  
Bing K. Jap ◽  
Thomas N. Earnest ◽  
Peter Walian ◽  
Kalle Gehring
Keyword(s):  
High Resolution ◽  
Three Dimensional ◽  
Data Set ◽  
Membrane Pore ◽  
3 Dimensional ◽  
Potential Map ◽  
High Resolution Images ◽  
Diffraction Patterns ◽  
Phoe Porin ◽  
Structural Architecture

PhoE porin is an outer membrane, pore-forming channel with selectivity for the transport of phosphate-containing compounds and negatively charged solutes. We have reconstituted this membrane protein with lipids to form highly coherent, 2-dimensional crystalline patches. Diffraction patterns and images of trehalose embedded crystalline patches were recorded using a JEOL 100B electron microscope, which is equipped with a field emission gun and a cold stage that was operated at about −120° C. A complete 3-dimensional (3-D) diffraction data set to a resolution of 2.8Å and a number of high resolution images at tilt angles ranging from 0 to 60 degrees were collected. A high resolution projection map at 3.5Å resolution and a 3-D map at 6Å , showing the detailed structural architecture of this protein, have been published.

Cooling-induced wrinkling of thin crystals of biological macromolecules can be prevented by using molybdenum grids

1992 ◽  
Vol 50 (1) ◽  
pp. 520-521
Author(s):  
Robert M. Glaeser
Keyword(s):  
High Resolution ◽  
Signal To Noise Ratio ◽  
Data Retrieval ◽  
Biological Macromolecules ◽  
Tilt Axis ◽  
Resolution Electron ◽  
High Resolution Images ◽  
Diffraction Patterns ◽  
Rate Of Success ◽  
High Degree

It is an important requirement of high resolution electron diffraction and electron microscopy of thin crystals of biological macromolecules that the specimen be flat (i.e. planar) to one degree or less over distances of one micrometer or more. This high degree of specimen flatness is required in order to collect diffraction patterns and images at high tilt angles and high resolution. Imperfect flatness causes the diffraction spots which are perpendicular to the tilt axis to become streaked or blurred, while the spots parallel to the tilt axis remain sharp. If the specimen wrinkling, or mosaic angular spread, is too severe, the diffraction spots overlap one another to make a continuum, and data retrieval becomes impossible (see Figure 3, for an example). Even before that point is reached, the broadening of the diffraction spots makes it increasingly difficult to obtain accurate background-subtracted diffraction intensities, and the signal-to-noise ratio in the computed Fourier transform of high resolution images is severely decreased. In some preparations of thin protein crystals the stringent requirements for specimen flatness can be met with a reasonable rate of success. In the case of bacteriorhodopsin, prepared as large singlecrystal sheets by detergent-induced fusion of the native purple membrane of Halobacterium halobium, the frequency of success is normally very low.

Periodic grain boundary structures in aluminium I. A combined experimental and theoretical investigation of coincidence grain boundary structure in aluminium

1977 ◽  
Vol 357 (1691) ◽  
pp. 453-470 ◽  
Keyword(s):  
Grain Boundary ◽  
Rigid Body ◽  
Interatomic Potential ◽  
Boundary Structure ◽  
Grain Boundary Structure ◽  
Transmission Electron ◽  
Annealing Twins ◽  
Theoretical Predictions ◽  
Atomic Relaxation ◽  
Pseudo Potential

The results of a computer simulation of the structure of periodic grain boundaries between twin related crystals of aluminium are described. An interatomic potential derived on the basis of pseudo-potential theory was used. The algorithm employed allows simultaneous local atomic relaxation and rigid body translation of the adjacent grains. It was found that rigid body translation is a dominant contribution to relaxation, and that the energy of a boundary, y, is not simply related to boundary periodicity. In addition, annealing twins in aluminium were observed by using transmission electron microscopy and detailed correspondence with theoretical predictions was found in two areas; the calculated y ’s of experimentally observed boundary planes were lower than those of geometrically possible alternatives, and excellent agreement between predicted and experimentally measured rigid body translations was obtained for two types of tilt boundary.

Modulated Structure of Bi1.8Sr2.0Rh1.6Ox

2007 ◽  
Vol 336-338 ◽  
pp. 818-821
Author(s):  
Kunio Yubuta ◽  
Satoshi Okada ◽  
Yuzuru Miyazaki ◽  
Ichiro Terasaki ◽  
Tsuyoshi Kajitani
Keyword(s):  
High Resolution ◽  
Electron Diffraction ◽  
High Resolution Electron Microscopy ◽  
Layered Crystal ◽  
Structural Analogue ◽  
Modulated Structure ◽  
Incident Electron Beam ◽  
Resolution Electron ◽  
High Resolution Images ◽  
Diffraction Patterns

We have investigated the modulated structure of the misfit-layered crystal Bi1.8Sr2.0Rh1.6Ox by means of electron diffraction and high-resolution electron microscopy. This compound consists of two interpenetrating subsystems of a hexagonal RhO2 sheet and a distorted four-layered rock-salt-type (Bi,Sr)O block. Both subsystems have common a-, c-axes and β-angles with a = 5.28 Å, c = 29.77 Å and β = 93.7º. On the other hand, the crystal structure is incommensurated parallel to the b-axes, among which b1 = 3.07 Å for the RhO2 sheet and b2 = 4.88 Å for the (Bi,Sr)O block. The misfit ratio, b1/b2 ~ 0.63, characterizes the structural analogue as [Bi1.79Sr1.98Oy]0.63[RhO2]. This compound has two modulation vectors, i.e., q1 = – a* + 0.63b1* and q2 = 0.17b1* + c*, and the superspace group is assigned as the Cc(1β0, 0μ1)-type from the electron diffraction patterns. High-resolution images taken with the incident electron beam parallel to the a- and c-axes clearly show displacive as well as compositional modulations.

Effects of illumination spot size on high-resolution image contrast for radiation-sensitive specimens

1986 ◽  
Vol 44 ◽  
pp. 14-17
Author(s):  
Kenneth H. Downing
Keyword(s):  
High Resolution ◽  
Electron Diffraction ◽  
Spot Size ◽  
Image Contrast ◽  
Protein Crystals ◽  
Hexagonal Symmetry ◽  
High Resolution Image ◽  
Lattice Images ◽  
High Resolution Images ◽  
Diffraction Patterns

Electron diffraction patterns of a number of different protein crystals extend to well beyond 0.4 nm. However, until quite recently, no images of these crystals had been obtained which showed such high resolution. The recent introduction of monolayer crystals of paraffin, which diffract at 0.4 nm several thousand times as strongly as typical protein crystals, has made it possible to obtain such high-resolution images almost routinely, and has allowed the study of the causes for the previous lack of success. It has been found that the images of paraffin crystals fall far short of images which could be obtained under ideal circumstances. Not only do the images only rarely show the pseudo-hexagonal symmetry of the crystals, but quantitative analysis of lattice images has shown that under normal conditions the image contrast is typically only about 3-4% of that which is theoretically possible, based on the strength of electron diffraction spots.

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