On Dark-Field High-Resolution Images Of Two-Dimensional Antiphase Structures

1983 ◽  
Vol 21 ◽  
Author(s):  
O. Terasaki ◽  
G.J. Wood ◽  
D. Watanabe
Keyword(s):  
High Resolution ◽  
Dark Field Image ◽  
Antiphase Domain ◽  
Dark Field ◽  
Two Dimensional ◽  
Domain Structures ◽  
Resolution Electron ◽  
True Representation ◽  
High Resolution Images ◽  
Electron Microscopes

ABSTRACTDark-field images of two-dimensional antiphase domain structures with stepped boundaries have been simulated for imaging conditions corresponding to some current high resolution electron microscopes. The simulations reveal that the positions of the dots in the dark-field images do not give a true representation of atomic structure; thus, in contrast to the brightfield superstructure images, it is very misleading to say that bright dots in the dark-field image correspond exactly to the positions of the minority atoms.

A study of the ordered structures of the Au–Mn system by high-voltage–high-resolution electron microscopy. II. Two-dimensional antiphase structures based on the DO 22 structure

1981 ◽  
Vol 14 (6) ◽  
pp. 392-400 ◽  
Author(s):  
O. Terasaki ◽  
D. Watanabe ◽  
K. Hiraga ◽  
D. Shindo ◽  
M. Hirabayashi
Keyword(s):  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Antiphase Domain ◽  
Two Dimensional ◽  
Ordered Structures ◽  
Domain Structures ◽  
Resolution Electron ◽  
Specimen Area ◽  
High Resolution Structure ◽  
Resolution Structure

Two-dimensional antiphase domain structures existing in the composition range 20–23 at.% Mn were investigated by a high-resolution structure-imaging technique with a 1 MV electron microscope. The structures are based on the DO 22 structure and consist of parallelogram-shaped domains containing 4 × 3 columns of Mn atoms and lozenge-shaped domains with 4 × 4 and 3 × 3 columns, and the domains are separated by two-dimensional antiphase boundaries parallel to the ({\bar 2}40) and (240) planes of the fundamental face-centred structure. The configuration of the domains changes delicately with a slight change of composition or annealing temperature, and the symmetry of the structure is lowered below about 670 K. The ideal structure models have compositions of about 22.7 at.% Mn. The images of about half of the specimen area of the 22.6 at.% Mn alloy annealed at 570 K do not correspond to these new structures, but bear a resemblance to the image expected from the two-dimensional antiphase structure proposed by Watanabe [J. Phys. Soc. Jpn (1960), 15, 1030–1040] for Au3Mn, which is based on the L12 structure and has boundaries parallel to the (100) and (010) planes.

Recent trends in high-resolution electron microscopy

1986 ◽  
Vol 44 ◽  
pp. 530-533
Author(s):  
David J. Smith
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Two Dimensional ◽  
Planar Defects ◽  
Medium Voltage ◽  
Resolution Electron ◽  
Routine Basis ◽  
Recent Trends ◽  
Electron Microscopes

The recent advent of high-resolution electron microscopes (HREMs) capable of resolving sub-2-Ångstrom detail on a routine basis has led to an enormous increase in the range of materials which can be usefully studied. Not only is it possible to resolve individual atomic columns in low index zones of most common metals but observations of semiconductors, for example, are no longer restricted to the traditional [110] zone, thereby making it feasible at last to obtain two-dimensional information about surfaces, interfaces and other planar defects. There is a worldwide upsurge of interest in the capabilities of these machines and the so-called medium-voltage (300-400kV) HREMs are selling rapidly despite their considerable expense. Our objective here is to provide a brief and selective overview of the latest applications and likely trends in HREM studies of materials - further details can be found elsewhere in these proceedings. No attempt is made to review instrumentation developments since they are being considered separately.

High resolution electron microscopy of molecular crystals I. Quaterrylene, C 40 H 20

1982 ◽  
Vol 381 (1780) ◽  
pp. 225-240 ◽  
Keyword(s):  
High Resolution ◽  
Film Growth ◽  
High Resolution Electron Microscopy ◽  
Boundary Structure ◽  
Grain Boundary Structure ◽  
Resolution Electron ◽  
High Resolution Images ◽  
Electron Microscopes ◽  
Dose Measurements ◽  
Image Simulations

The polynuclear aromatic hydrocarbon quaterrylene, C 40 H 20 , has been studied by using high resolution electron microscopes operating at 100 and 500 kV. Despite the susceptibility of quaterrylene to damage by the incident electron beam, the use of low-dose techniques has allowed a detailed investigation of thin film growth and grain boundary structure in quaterrylene. Comparisons with image simulations establish that high resolution images recorded in the (110)-projection at 500 kV extend to about 0.35 nm, with this figure being limited by radiation damage rather than microscope performance. Moreover, critical dose measurements by electron diffraction establish a good correlation between dose and spot resolution. Extensive crystal distortion has been observed to accommodate mismatch at crystal junctions and boundaries; it is proposed that such distortion arises from individual molecular distortion.

scholarly journals Coma-corrected rapid single-particle cryo-EM data collection on the CRYO ARM 300

2021 ◽  
Vol 77 (5) ◽  
pp. 555-564
Author(s):  
Rouslan G. Efremov ◽  
Annelore Stroobants
Keyword(s):  
High Resolution ◽  
Data Collection ◽  
Single Particle ◽  
Protein Complexes ◽  
Large Area ◽  
Beam Image ◽  
Resolution Electron ◽  
High Resolution Images ◽  
Electron Microscopes ◽  
Data Collection Procedure

Single-particle cryogenic electron microscopy has recently become a major method for determining the structures of proteins and protein complexes. This has markedly increased the demand for throughput of high-resolution electron microscopes, which are required to produce high-resolution images at high rates. An increase in data-collection throughput can be achieved by using large beam-image shifts combined with off-axis coma correction, enabling the acquisition of multiple images from a large area of the EM grid without moving the microscope stage. Here, the optical properties of the JEOL CRYO ARM 300 electron microscope equipped with a K3 camera were characterized under off-axis illumination conditions. It is shown that efficient coma correction can be achieved for beam-image shifts with an amplitude of at least 10 µm, enabling a routine throughput for data collection of between 6000 and 9000 images per day. Use of the benchmark for the rapid data-collection procedure (with beam-image shifts of up to 7 µm) on apoferritin resulted in a reconstruction at a resolution of 1.7 Å. This demonstrates that the rapid automated acquisition of high-resolution micrographs is possible using a CRYO ARM 300.

Effect of strain on ADF-STEM high-resolution images

1991 ◽  
Vol 49 ◽  
pp. 666-667
Author(s):  
M. Kelly ◽  
D.M. Bird
Keyword(s):  
High Resolution ◽  
Strong Influence ◽  
Intensity Variation ◽  
Dark Field ◽  
Atomic Resolution ◽  
Strain Fields ◽  
High Resolution Image ◽  
Annular Dark Field ◽  
High Resolution Images ◽  
Interesting Alternative

It is well known that strain fields can have a strong influence on the details of HREM images. This, for example, can cause problems in the analysis of edge-on interfaces between lattice mismatched materials. An interesting alternative to conventional HREM imaging has recently been advanced by Pennycook and co-workers where the intensity variation in the annular dark field (ADF) detector is monitored as a STEM probe is scanned across the specimen. It is believed that the observed atomic-resolution contrast is correlated with the intensity of the STEM probe at the atomic sites and the way in which this varies as the probe moves from cell to cell. As well as providing a directly interpretable high-resolution image, there are reasons for believing that ADF-STEM images may be less suseptible to strain than conventional HREM. This is because HREM images arise from the interference of several diffracted beams, each of which is governed by all the excited Bloch waves in the crystal.

Electron crystallographic determination of the 3-D structure of staurolite at atomic resolution

1991 ◽  
Vol 49 ◽  
pp. 540-541
Author(s):  
Kenneth H. Downing ◽  
Hu Meisheng ◽  
Hans-Rudolf Went ◽  
Michael A. O'Keefe
Keyword(s):  
High Resolution ◽  
Three Dimensional ◽  
High Resolution Electron Microscopy ◽  
Atomic Resolution ◽  
Dimensional Structure ◽  
Structure Information ◽  
Resolution Electron ◽  
Scattering Effects ◽  
High Resolution Images ◽  
Effects Of Radiation

With current advances in electron microscope design, high resolution electron microscopy has become routine, and point resolutions of better than 2Å have been obtained in images of many inorganic crystals. Although this resolution is sufficient to resolve interatomic spacings, interpretation generally requires comparison of experimental images with calculations. Since the images are two-dimensional representations of projections of the full three-dimensional structure, information is invariably lost in the overlapping images of atoms at various heights. The technique of electron crystallography, in which information from several views of a crystal is combined, has been developed to obtain three-dimensional information on proteins. The resolution in images of proteins is severely limited by effects of radiation damage. In principle, atomic-resolution, 3D reconstructions should be obtainable from specimens that are resistant to damage. The most serious problem would appear to be in obtaining high-resolution images from areas that are thin enough that dynamical scattering effects can be ignored.

The observation of solutions in Ni3Nb

1988 ◽  
Vol 46 ◽  
pp. 540-541
Author(s):  
Z.M. Wang ◽  
J.P. Zhang
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Phase Modulation ◽  
High Resolution Electron Microscopy ◽  
Antiphase Domain ◽  
Boundary Area ◽  
Matrix Type ◽  
Resolution Electron ◽  
Domain Boundaries ◽  
Kontorova Model

High resolution electron microscopy reveals that antiphase domain boundaries in β-Ni3Nb have a hexagonal unit cell with lattice parameters ah=aβ and ch=bβ, where aβ and bβ are of the orthogonal β matrix. (See Figure 1.) Some of these boundaries can creep “upstairs” leaving an incoherent area, as shown in region P. When the stepped boundaries meet each other, they do not lose their own character. Our consideration in this work is to estimate the influnce of the natural misfit δ{(ab-aβ)/aβ≠0}. Defining the displacement field at the boundary as a phase modulation Φ(x), following the Frenkel-Kontorova model [2], we consider the boundary area to be made up of a two unit chain, the upper portion of which can move and the lower portion of the β matrix type, assumed to be fixed. (See the schematic pattern in Figure 2(a)).

Atomic structure imaging of the Si/SiO2 interface with high-resolution electron microscopy

1986 ◽  
Vol 44 ◽  
pp. 390-391
Author(s):  
J.L. Batstone ◽  
J.M. Gibson ◽  
Alice.E. White ◽  
K.T. Short
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Atomic Structure ◽  
High Resolution Electron Microscopy ◽  
Medium Voltage ◽  
Voltage Electron ◽  
Resolution Electron ◽  
Structural Image ◽  
Electron Microscopes ◽  
Point To Point

High resolution electron microscopy (HREM) is a powerful tool for the determination of interface atomic structure. With the previous generation of HREM's of point-to-point resolution (rpp) >2.5Å, imaging of semiconductors in only <110> directions was possible. Useful imaging of other important zone axes became available with the advent of high voltage, high resolution microscopes with rpp <1.8Å, leading to a study of the NiSi2 interface. More recently, it was shown that images in <100>, <111> and <112> directions are easily obtainable from Si in the new medium voltage electron microscopes. We report here the examination of the important Si/Si02 interface with the use of a JEOL 4000EX HREM with rpp <1.8Å, in a <100> orientation. This represents a true structural image of this interface.

High-resolution EM investigation about effect of stress on formation of ω-phase crystals in β-tttanium alloys

1996 ◽  
Vol 54 ◽  
pp. 1006-1007
Author(s):  
E. Sukedai ◽  
M. Shimoda ◽  
A. Fujita ◽  
H. Nishizawa ◽  
H. Hashimoto
Keyword(s):  
High Resolution ◽  
Titanium Alloys ◽  
High Resolution Electron Microscopy ◽  
Dark Field ◽  
Zone Refining ◽  
Ω Phase ◽  
Α Phase ◽  
Nucleation Sites ◽  
Resolution Electron ◽  
Bcc Structure

ω-phase particles formed in β-titanium alloys (bcc structure) act important roles to their mechanical properties such as ductility and hardness. About the ductility, fine ω-phase particles in β–titanium alloys improve the ductility, because ω-phase crystals becomes nucleation sites of α-phase and it is well known that (β+α) duplex alloys have higher ductility. In the present study, the formation sites and the formation mechanism of ω-phase crystals due to external stress and aging are investigated using the conventional and high resolution electron microscopy.A β-titanium alloy (Til5Mo5Zr) was supplied by Kobe Steel Co., and a single crystal was prepared by a zone refining method. Plates with {110} surface were cut from the crystal and were pressured hydrostatically, and stressed by rolling and tensile testing. Specimens for aging with tensile stress were also prepared from Ti20Mo polycrystals. TEM specimens from these specimens were prepared by a twin-jet electron-polishing machine. A JEM 4000EX electron microscope operated at 400k V was used for taking dark field and HREM images.

The Contribution of Intermediate-Voltage, High-Resolution Electron Microscopy In Materials Science: An Appraisal

1990 ◽  
Vol 48 (1) ◽  
pp. 478-479
Author(s):  
John L. Hutchison
Keyword(s):  
High Resolution ◽  
Materials Science ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
The Past ◽  
Resolution Electron ◽  
Extreme Sensitivity ◽  
Electron Microscopes ◽  
New Generation ◽  
Small Metal Particles

Over the past five years or so the development of a new generation of high resolution electron microscopes operating routinely in the 300-400 kilovolt range has produced a dramatic increase in resolution, to around 1.6 Å for “structure resolution” and approaching 1.2 Å for information limits. With a large number of such instruments now in operation it is timely to assess their impact in the various areas of materials science where they are now being used. Are they falling short of the early expectations? Generally, the manufacturers’ claims regarding resolution are being met, but one unexpected factor which has emerged is the extreme sensitivity of these instruments to both floor-borne and acoustic vibrations. Successful measures to counteract these disturbances may require the use of special anti-vibration blocks, or even simple oil-filled dampers together with springs, with heavy curtaining around the microscope room to reduce noise levels. In assessing performance levels, optical diffraction analysis is becoming the accepted method, with rotational averaging useful for obtaining a good measure of information limits. It is worth noting here that microscope alignment becomes very critical for the highest resolution.In attempting an appraisal of the contributions of intermediate voltage HREMs to materials science we will outline a few of the areas where they are most widely used. These include semiconductors, oxides, and small metal particles, in addition to metals and minerals.

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