Inelastic Scattering in Electron Microscopy

1973 ◽  
Vol 31 ◽  
pp. 254-255
Author(s):  
M. Isaacson ◽  
J. Langmore ◽  
J. Wall ◽  
A. V. Crewe
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Chromatic Aberration ◽  
Dark Field ◽  
Biological Molecules ◽  
Objective Lens ◽  
Transmission Electron ◽  
Field Electron Microscopy ◽  
Dark Field Electron ◽  
Conventional Transmission Electron Microscope

The effort to image biological molecules by high resolution (2-4 Å) dark field electron microscopy has stimulated interest in those factors Which influence image contrast. It is known that elastically scattered electrons can be used to obtain high resolution information about a specimen. On the other hand, most inelastically scattered electrons cannot contribute any high resolution information about the specimen since they are the result of a nonlocalized interaction of the incident electrons with the electrons in the specimen. Moreover, in the conventional transmission electron microscope (CTEM) without a chromatic aberration corrector or an energy filter between the specimen and recording plane, inelastically scattered electrons blur the image, due to the chromatic aberration of the objective lens. This has particular importance in biological electron microscopy, since the ratio of total inelastic to elastic scattering for carbon is 1.6.

Experimental High Resolution Dark Field Electron Microscopy

1977 ◽  
Vol 35 ◽  
pp. 142-143
Author(s):  
Larry Pierce ◽  
Peter R. Buseck
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Dark Field ◽  
Objective Lens ◽  
Aperture Size ◽  
Bright Field ◽  
Chromatic Aberrations ◽  
Field Electron Microscopy ◽  
Dark Field Electron ◽  
Diffraction Patterns

High resolution dark field (DF) images of the superstructures of the pyrrhotite (Fe1-xS) and bornite-digenite (Cu5FeS4-Cu9S5) series can be related to structure. Further, they provide more detail than bright field (BF) images. The same objective aperture size and stigmater settings were used for DF as for BF imaging; symmetrical arrangements of diffracted beams in the objective aperture were used. Images that can be related to structure were obtained at the defocus value giving the greatest image contrast, thereby enabling proper defocusing without requiring extensive through-focus series.For the minerals of interest, diffraction patterns consist of many superstructure reflections and a few subcell reflections. BF images contain primarily features of the superstructure, presumably because the subcell reflections fall far from the axis of the objective lens and thus are affected by spherical and chromatic aberrations and beam divergence. Likewise, DF images formed with a similar arrangement of beams as that in BF contain only features of superstructure, but with reverse contrast to BF.

Current and future aberration correctors for the improvement of resolution in electron microscopy

2009 ◽  
Vol 367 (1903) ◽  
pp. 3665-3682 ◽  
Author(s):  
M. Haider ◽  
P. Hartel ◽  
H. Müller ◽  
S. Uhlemann ◽  
J. Zach
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Low Voltage ◽  
Spherical Aberration ◽  
Chromatic Aberration ◽  
Objective Lens ◽  
Voltage Electron ◽  
System A ◽  
Transmission Electron ◽  
Correction System

The achievable resolution of a modern transmission electron microscope (TEM) is mainly limited by the inherent aberrations of the objective lens. Hence, one major goal over the past decade has been the development of aberration correctors to compensate the spherical aberration. Such a correction system is now available and it is possible to improve the resolution with this corrector. When high resolution in a TEM is required, one important parameter, the field of view, also has to be considered. In addition, especially for the large cameras now available, the compensation of off-axial aberrations is also an important task. A correction system to compensate the spherical aberration and the off-axial coma is under development. The next step to follow towards ultra-high resolution will be a correction system to compensate the chromatic aberration. With such a correction system, a new area will be opened for applications for which the chromatic aberration defines the achievable resolution, even if the spherical aberration is corrected. This is the case, for example, for low-voltage electron microscopy (EM) for the investigation of beam-sensitive materials, for dynamic EM or for in-situ EM.

Characterization Of Chrysotile Asbestos In Automobile Brake Drum Dust By Transmission Electron Microscopy (TEM)

1977 ◽  
Vol 35 ◽  
pp. 148-149
Author(s):  
Krishna Seshan ◽  
Glenn R. Smith
Keyword(s):  
Electron Microscopy ◽  
Dark Field ◽  
Chrysotile Asbestos ◽  
Fibre Bundles ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
Field Electron Microscopy ◽  
Dark Field Electron ◽  
Brake Drum

This study supports other work that automobile brake drum dust is a source of partially altered and unaltered chrysotile asbestos (1-3) and suggests that dark-field electron microscopy could be used to identify the source of the fibres. These results are in contradiction to those who report that high temperatures reached during braking reduce a majority of the chrysotile to forsterite (4,5).Automobile brake drum dust was directly transferred to formvar coated grids and coated with carbon on both sides. The grids were then examined with a Siemens 1A and a Philips 301 at 100 kV.Intact chrysotile fibre bundles with some phenolic opaque binder is shown in Fig. 1 displaying partially deformed internal canals, but does not show gross morphological change. Unaltered chrysotile is shown in Fig. 2a and was confirmed by selected area electron diffraction (SAED), see Fig. 2.

Studies of a Model DNA Sequence by Dark Field Electron Microscopy

1974 ◽  
Vol 32 ◽  
pp. 384-385
Author(s):  
R.F. Whiting ◽  
F.P. Ottensmeyer
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Dna Sequence ◽  
Dark Field ◽  
Heavy Atoms ◽  
Transmission Electron ◽  
Thin Carbon ◽  
Field Electron Microscopy ◽  
Dark Field Electron ◽  
Small Model

Single heavy atoms in a variety of small model molecules have been managed by dark field transmission electron microscopy. The image intenses and geometry have been shown to be consistent with theoretical expectations. The use of this system for sequencing requires a demonstration theory accurate sequence can be derived for a small well-defined nucleic species. We have prepared and stained a homogeneous fragment of bacteria DNA. The molecule was a large pyrimidine oligomer anc b 5en sequenced biochemically. The sequence is shown in Fig. 1(a). Thymidine residues were marked with Beer's OsO4-cyanide stain. The refined, purified product was applied to pre-treated thin carbon specimen forms for electron microscopy.

Recent advances in studies of carbon fibre structure

1980 ◽  
Vol 294 (1411) ◽  
pp. 443-449 ◽  
Keyword(s):  
Electron Microscopy ◽  
Carbon Fibre ◽  
Dark Field ◽  
Diffraction Measurement ◽  
Type I ◽  
Fibre Structure ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Field Electron Microscopy ◽  
Dark Field Electron

Carbon fibre structure is usually characterized by means of X-ray diffraction measurement and electron microscope observation. The meaning of the most important parameters is discussed in terms of the structures revealed by high resolution transmission electron microscopy. Recently, dark-field electron microscopy and electron diffraction of selected areas has been used to reveal and characterize skin-core and sheath—core heterogeneity in type I (2500 °C) polyacrylonitrile (PAN)-based carbon fibres. Lattice-fringe electron microscopy has given some insight into the nature of the surface layers in type I, type II (1500 °C) and type A (1000 °C) fibres. The skin regions of type I fibres are seen to contain misorientated crystallites interlinked in a complex manner; these are flaws that will limit the intrinsic tensile strength of the material.

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