scholarly journals Dark field imaging of biological macromolecules with the scanning transmission electron microscope

1979 ◽  
Vol 76 (3) ◽  
pp. 1228-1232 ◽  
Author(s):  
M. Ohtsuki ◽  
M. S. Isaacson ◽  
A. V. Crewe
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Biological Macromolecules ◽  
Scanning Transmission Electron ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Field Imaging

Resolution in the Scanning Transmission Electron Microscope

1972 ◽  
Vol 30 ◽  
pp. 454-455
Author(s):  
M. G. R. Thomson
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Spherical Aberration ◽  
Signal To Noise Ratio ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Objective Lens ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

The variation of contrast and signal to noise ratio with change in detector solid angle in the high resolution scanning transmission electron microscope was discussed in an earlier paper. In that paper the conclusions were that the most favourable conditions for the imaging of isolated single heavy atoms were, using the notation in figure 1, either bright field phase contrast with β0⋍0.5 α0, or dark field with an annular detector subtending an angle between ao and effectively π/2.The microscope is represented simply by the model illustrated in figure 1, and the objective lens is characterised by its coefficient of spherical aberration Cs. All the results for the Scanning Transmission Electron Microscope (STEM) may with care be applied to the Conventional Electron Microscope (CEM). The object atom is represented as detailed in reference 2, except that ϕ(θ) is taken to be the constant ϕ(0) to simplify the integration. This is reasonable for θ ≤ 0.1 θ0, where 60 is the screening angle.

scholarly journals Determination of Dy substitution site in Nd2−xDyxFe14B by HAADF-STEM and illustration of magnetic anisotropy of “g” and “f” sites, before and after substitution

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Syed Kamran Haider ◽  
Min-Chul Kang ◽  
Jisang Hong ◽  
Young Soo Kang ◽  
Cheol-Woong Yang ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Magnetic Anisotropy ◽  
Transmission Electron Microscope ◽  
Magnetic Moment ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Product Analysis ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

AbstractNd2Fe14B and Nd2−xDyxFe14B (x = 0.25, 0.50) particles were prepared by the modified co-precipitation followed by reduction–diffusion process. Bright field scanning transmission electron microscope (BF-STEM) image revealed the formation of Nd–Fe–B trigonal prisms in [− 101] viewing zone axis, confirming the formation of Nd2Fe14B/Nd2−xDyxFe14B. Accurate site for the Dy substitution in Nd2Fe14B crystal structure was determined as “f” site by using high-angle annular dark field scanning transmission electron microscope (HAADF-STEM). It was found that all the “g” sites are occupied by the Nd, meanwhile Dy occupied only the “f” site. Anti-ferromagnetic coupling at “f” site decreased the magnetic moment values for Nd1.75Dy0.25Fe14B (23.48 μB) and Nd1.5Dy0.5Fe14B (21.03 μB) as compared to Nd2Fe14B (25.50 μB). Reduction of magnetic moment increased the squareness ratio, coercivity and energy product. Analysis of magnetic anisotropy at constant magnetic field confirmed that “f” site substitution did not change the patterns of the anisotropy. Furthermore, magnetic moment of Nd2Fe14B, Nd2−xDyxFe14B, Nd (“f” site), Nd (“g” site) and Dy (“f” site) was recorded for all angles between 0° and 180°.

scholarly journals Determination of Dy Substitution Site in Nd2-xDyxFe14B by HAADF-STEM and Illustration of Magnetic Anisotropy of “g” and “f” Sites, Before and After Substitution

2021 ◽  
Author(s):  
Young Kang ◽  
Syed Haider ◽  
Min-Chul Kang ◽  
Jisang Hong ◽  
Cheol-Woong Yang ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Magnetic Anisotropy ◽  
Transmission Electron Microscope ◽  
Magnetic Moment ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Product Analysis ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

Abstract Nd2Fe14B and Nd2 − xDyxFe14B (x = 0.25,0.50) particles were prepared by the modified co-precipitation followed by reduction-diffusion process. Bright field scanning transmission electron microscope (BF-STEM) image revealed the formation of Nd-Fe-B trigonal prisms in [-101] viewing zone axis, confirming the formation of Nd2Fe14B/Nd2 − xDyxFe14B. Accurate site for the Dy substitution in Nd2Fe14B crystal structure was determined as “f” site by using high-angle annular dark field scanning transmission electron microscope (HAADF-STEM). It was found that all the “g” sites are occupied by the Nd, where’s and Dy occupied only the “f” site. Anti-ferromagnetic coupling at “f” site decreased the magnetic moment values for Nd1.75Dy0.25Fe14B (23.48 µB) and Nd1.5Dy0.5Fe14B (21.03 µB) as compared to Nd2Fe14B (25.50 µB). Reduction of magnetic moment increased the squareness ratio, coercivity and energy product. Analysis of magnetic anisotropy at constant magnetic field confirmed that “f” site substitution did not change the patterns of the anisotropy. Furthermore, magnetic moment of Nd2Fe14B, Nd2 − xDyxFe14B, Nd (“f” site), Nd (“g” site) and Dy (“f” site) was recorded for all angles between 0-180o.

A General Method for Spectrometer Design in the Scoff Approximation

1976 ◽  
Vol 34 ◽  
pp. 538-539
Author(s):  
J. R. Fields
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Energy Analysis ◽  
Incident Beam ◽  
Scanning Transmission Electron Microscope ◽  
Chemical Identification ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
General Method

The energy analysis of electrons scattered by a specimen in a scanning transmission electron microscope can improve contrast as well as aid in chemical identification. In so far as energy analysis is useful, one would like to be able to design a spectrometer which is tailored to his particular needs. In our own case, we require a spectrometer which will accept a parallel incident beam and which will focus the electrons in both the median and perpendicular planes. In addition, since we intend to follow the spectrometer by a detector array rather than a single energy selecting slit, we need as great a dispersion as possible. Therefore, we would like to follow our spectrometer by a magnifying lens. Consequently, the line along which electrons of varying energy are dispersed must be normal to the direction of the central ray at the spectrometer exit.

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