<i>n</i>-Beam lattice images. VI. Degradation of image resolution by a combination of incident-beam divergence and spherical aberration

O’Keefe, Michael A.; Sanders, J. V.

doi:10.1107/s0567739475000654

Cited by 62 publications

(15 citation statements)

References 6 publications

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“…sities for a range of crystal tilts covering the diffraction discs (O'Keefe & Sanders, 1975). This is time consuming as the iteration must be repeated for each tilt.…”

Section: Electron-optical Imaging Of the Hollandite Structure At 3 A mentioning

confidence: 99%

Electron-optical imaging of the hollandite structure at 3 Å resolution

Bursill¹,

Wilson²

1977

Acta Cryst Sect A

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This paper shows that it is possible markedly to improve the resolution obtainable in electron micrographs by deliberately using low beam divergence (2 x 10 -4 rad) and by minimizing thermal spread in the electron gun. Point-to-point resolutions in the sub-3 A range will be illustrated for the hollandite structure. Image matching, including the effects of both beam divergence and chromatic aberration, showed that the experimental images could be fitted using 2 A objective aperture, with no divergence and defocus ripple of only 50 ,~. In fact, these stringent experimental requirements must be met if useful structural information is to be obtained in the 2-3 A range.

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“…sities for a range of crystal tilts covering the diffraction discs (O'Keefe & Sanders, 1975). This is time consuming as the iteration must be repeated for each tilt.…”

Section: Electron-optical Imaging Of the Hollandite Structure At 3 A mentioning

confidence: 99%

Electron-optical imaging of the hollandite structure at 3 Å resolution

Bursill¹,

Wilson²

1977

Acta Cryst Sect A

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“…When a crystal of smaller unit cell is studied, however, it becomes doubtful that the above-mentioned conditions are always satisfied. Therefore, it is worth while in the case of V203 to compare the image calculated by use of this method with that obtained by summing the image intensity over the finite effective source (spatial coherence) and over the distribution of the defocus fluctuation (temporal coherence) (O'Keefe & Sanders, 1975;Bursill & Wilson, 1977). However, the latter, let us call it the 'intensity-sum method', naturally needs computation of very long duration if it is applied strictly as is the case for Fig.…”

Section: Validity Of the Envelope-function Approximationmentioning

confidence: 99%

Lattice-image interpretation of a relatively-small-unit-cell crystal

Tanaka¹,

Jouffrey²

1984

Acta Cryst Sect A

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Many-beam lattice images obtained at 200 kV from V203 crystals are discussed in comparison with those calculated in the Bloch-wave approach. The technique of optical diffractogram and equal-thickness fringes is utilized, if possible, to determine the defocus value and the crystal thickness which are the essential parameters for objective interpretation at atomic resolution. Whereas images observed in a thin region (~<50 A) of crystal have been reproduced fairly well by simulation, there are others from thicker regions which are not always explained for lack of knowledge of the parameters. As for the effect of the partial coherence, the validity of the envelope-function approximation is examined with the aid of the first principle involving image-intensity summation, and under the experimental conditions used it proved to be satisfactory for qualitatively reproducing the observed image even for relatively thick (~<450 A) regions.

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“…Individual metal-atom columns became accessible in alloys at 1.8-2.0Å resolution [5], and in silicates at 1.6Å resolution [6]. Development of software for simulation of HREM images from structural models explained the images and confirmed their interpretations [7][8][9][10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

HRTEM imaging of atoms at sub-Ångström resolution

O’Keefe¹,

Allard²,

Blom³

2005

Microscopy

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John Cowley and his group at Arizona State University pioneered the use of transmission electron microscopy (TEM) for high-resolution imaging. Images were achieved three decades ago showing the crystal unit cell content at better than 4Å resolution. This achievement enabled researchers to pinpoint the positions of heavy atom columns within the unit cell. Lighter atoms appear as resolution is improved to sub-Ångström levels. Currently, advanced microscopes can image the columns of the light atoms (carbon, oxygen, nitrogen) that are present in many complex structures, and even the lithium atoms present in some battery materials. SubÅngström imaging, initially achieved by focal-series reconstruction of the specimen exit surface wave, will become commonplace for next-generation electron microscopes with C S -corrected lenses and monochromated electron beams. Resolution can be quantified in terms of peak separation and inter-peak minimum, but the limits imposed on the attainable resolution by the properties of the microscope specimen need to be considered. At extreme resolution the "size" of atoms can mean that they will not be resolved even when spaced farther apart than the resolution of the microscope.

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n-Beam lattice images. VI. Degradation of image resolution by a combination of incident-beam divergence and spherical aberration

Cited by 62 publications

References 6 publications

Electron-optical imaging of the hollandite structure at 3 Å resolution

Electron-optical imaging of the hollandite structure at 3 Å resolution

Lattice-image interpretation of a relatively-small-unit-cell crystal

HRTEM imaging of atoms at sub-Ångström resolution

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