High-angle scattering of fast electrons from crystals containing heavy elements: Simulation and experiment

2009 ◽  
Vol 79 (21) ◽  
Author(s):  
James M. LeBeau ◽  
Scott D. Findlay ◽  
Xiqu Wang ◽  
Allan J. Jacobson ◽  
Leslie J. Allen ◽  
...  
Keyword(s):  
Heavy Elements ◽  
High Angle ◽  
Fast Electrons ◽  
Angle Scattering ◽  
Simulation And Experiment

High-angle electron scattering from amorphous silicon

1995 ◽  
Vol 53 ◽  
pp. 162-163
Author(s):  
M. Libera ◽  
J.A. Ott ◽  
K. Siangchaew ◽  
L. Tsung
Keyword(s):  
Electron Scattering ◽  
Amorphous Material ◽  
Structural Defects ◽  
Constant Thickness ◽  
High Angle ◽  
Fast Electrons ◽  
Angle Scattering ◽  
Stem Image ◽  
Amorphous Si ◽  
Thermal Vibrations

Channeling occurs when fast electrons follow atomic strings in a crystal where there is a minimum in the potential energy (1). Channeling has a strong effect on high-angle scattering. Deviations in atomic position along a channel due to structural defects or thermal vibrations increase the probability of scattering (2-5). Since there are no extended channels in an amorphous material the question arises: for a given material with constant thickness, will the high-angle scattering be higher from a crystal or a glass?Figure la shows a HAADF STEM image collected using a Philips CM20 FEG TEM/STEM with inner and outer collection angles of 35mrad and lOOmrad. The specimen (6) was a cross section of singlecrystal Si containing: amorphous Si (region A), defective Si containing many stacking faults (B), two coherent Ge layers (CI; C2), and a contamination layer (D). CBED patterns (fig. lb), PEELS spectra, and HAADF signals (fig. lc) were collected at 106K and 300K along the indicated line.

scholarly journals Scanning transmission imaging in the helium ion microscope using a microchannel plate with a delay line detector

2020 ◽  
Vol 11 ◽  
pp. 1854-1864
Author(s):  
Eduardo Serralta ◽  
Nico Klingner ◽  
Olivier De Castro ◽  
Michael Mousley ◽  
Santhana Eswara ◽  
...  
Keyword(s):  
Delay Line ◽  
Ion Beam ◽  
Microchannel Plate ◽  
Wide Energy Range ◽  
High Angle ◽  
Data Set ◽  
Beam Position ◽  
Angle Scattering ◽  
Helium Ion ◽  
Scanning Transmission

A detection system based on a microchannel plate with a delay line readout structure has been developed to perform scanning transmission ion microscopy (STIM) in the helium ion microscope (HIM). This system is an improvement over other existing approaches since it combines the information of the scanning beam position on the sample with the position (scattering angle) and time of the transmission events. Various imaging modes, such as bright field and dark field or the direct image of the transmitted signal, can be created by post-processing the collected STIM data. Furthermore, the detector has high spatial and temporal resolution, is sensitive to both ions and neutral particles over a wide energy range, and shows robustness against ion beam-induced damage. A special in-vacuum movable support gives the possibility of moving the detector vertically, placing the detector closer to the sample for the detection of high-angle scattering events, or moving it down to increase the angular resolution and distance for time-of-flight measurements. With this new system, we show composition-dependent contrast for amorphous materials and the contrast difference between small-angle and high-angle scattering signals. We also detect channeling-related contrast on polycrystalline silicon, thallium chloride nanocrystals, and single-crystalline silicon by comparing the signal transmitted at different directions for the same data set.

The elastic scattering of fast electrons and positrons by hydrogen and helium atoms

1959 ◽  
Vol 250 (1262) ◽  
pp. 337-345 ◽  
Keyword(s):  
Elastic Scattering ◽  
Cross Sections ◽  
Differential Cross ◽  
Born Approximation ◽  
Logarithmic Singularity ◽  
Hydrogen Atoms ◽  
Fast Electrons ◽  
Helium Atoms ◽  
Electrons And Positrons ◽  
Angle Scattering

A simplification of the second Born approximation due to Massey & Mohr is used to calculate the differential cross-sections for the elastic scattering of fast electrons and fast positrons by hydrogen atoms and helium atoms, the method of Dalitz being applied to evaluate all the relevant integrals. Although the logarithmic singularity which is found in the differential cross-section for zero-angle scattering is shown to be absent in the true second Born approximation the use of the simplification of this approximation is justified at sufficiently high impact energies provided the angle of scattering is not too small. The results of the calculations for incident electrons in helium are compared with the available experimental data.

scholarly journals Towards weighing individual atoms by high-angle scattering of electrons

2015 ◽  
Vol 151 ◽  
pp. 23-30 ◽  
Author(s):  
G. Argentero ◽  
C. Mangler ◽  
J. Kotakoski ◽  
F.R. Eder ◽  
J.C. Meyer
Keyword(s):  
High Angle ◽  
Angle Scattering

The Elastic Scattering of Fast Electrons by Heavy Elements

1939 ◽  
Vol 56 (6) ◽  
pp. 612-613 ◽  
Author(s):  
J. H. Bartlett ◽  
R. E. Watson
Keyword(s):  
Elastic Scattering ◽  
Heavy Elements ◽  
Fast Electrons

Elastic scattering of partially coherent beams of fast electrons by a crystal with a defect

1999 ◽  
Vol 55 (2) ◽  
pp. 289-304
Author(s):  
N. I. Borgardt
Keyword(s):  
Plane Waves ◽  
Large Angle ◽  
Matrix Elements ◽  
Bloch Waves ◽  
Fast Electrons ◽  
Angle Scattering ◽  
Coherent Beams ◽  
The Matrix ◽  
Mutual Intensity ◽  
Convergent Beam

Scattering of a quasi-monochromatic electron beam by a crystal with a defect is described with the use of the mutual coherency function and the formalism of quasi-Bloch waves. An expression correlating the mutual intensity on the exit and entrance surfaces of the crystal in terms of the scattering matrix has been found. The matrix elements are determined by a system of integro-differential equations, which have been obtained without using the column approximation. It has been shown that calculations of the matrix elements can be significantly simplified when the approximation of the small-angle scattering of quasi-Bloch waves by the defect displacement field is satisfied. Such an approximation can be applied in many cases, e.g. to a crystal with a dislocation. The mutual intensity on the crystal entrance surface has been found for the general case of defocused illumination. As an example of applying the new approach, expressions for the intensity in convergent-beam electron diffraction (CBED) and large-angle CBED (LACBED) patterns have been obtained. The LACBED patterns of a crystal with a dislocation have been simulated. It has been shown that the developed approach allows a more exact simulation of the LACBED than do the conventional approaches using the column approximation and the approximation of independent plane waves filling the illumination cone.

scholarly journals The Analytical Limits: HADF (High Angle Dark Field Imaging)

1996 ◽  
Vol 4 (9) ◽  
pp. 14-15
Author(s):  
Michael Kersker
Keyword(s):  
Dark Field ◽  
Atomic Level ◽  
Imaging Method ◽  
High Angle ◽  
Contrast Imaging ◽  
Heavy Atoms ◽  
Dark Field Imaging ◽  
Angle Scattering ◽  
Z Contrast ◽  
Field Imaging

High Angle Dark Field Imaging, or Z contrast imaging, is an Imaging method. It takes advantage of the useful fact that if one uses the high angle scattering intensities and eliminates the elastic scattered (diffracted) beams from the image (by using a Howie type angular dark field detector), the remaining image will be characterized by, if the probe used is on the order of the atomic dimensions, intensity modulations that reveal atom positions and relative atomic number. In simple terms, the image will display Z-contrast at the atomic level and can differentiate columns of heavy atoms from columns of lighter ones.

scholarly journals Scanning transmission imaging in the helium ion microscope using a microchannel plate with a delay line detector

2020 ◽  
Author(s):  
Eduardo Serralta ◽  
Nico Klingner ◽  
Olivier De Castro ◽  
Michael Mousley ◽  
Santhana Eswara ◽  
...  
Keyword(s):  
Delay Line ◽  
Ion Beam ◽  
Microchannel Plate ◽  
Wide Energy Range ◽  
High Angle ◽  
Data Set ◽  
Beam Position ◽  
Angle Scattering ◽  
Helium Ion ◽  
Scanning Transmission

A detection system based on a microchannel plate with a delay line readout structure has been developed to perform scanning transmission ion microscopy (STIM) in the helium ion microscope (HIM). This system is an improvement over other existing approaches since it combines the information of the scanning beam position on the sample with the position (scattering angle) and time of the transmission events. Various imaging modes such as bright and dark field or the direct image of the transmitted signal can be created by post-processing the collected STIM data. Furthermore, the detector has high spatial and time resolution, is sensitive to both ions and neutral particles over a wide energy range, and shows robustness against ion beam-induced damage. A special in-vacuum movable support gives the possibility of moving the detector vertically, placing the detector closer to the sample for the detection of high-angle scattering events, or moving it down to increase the angular resolution and distance for time-of-flight measurements. With this new system, we show composition-dependent contrast for amorphous materials and the contrast difference between small and high angle scattering signals. We also detect channeling related contrast on polycrystalline silicon, thallium chloride nanocrystals, and single crystalline silicon by comparing the signal transmitted at different directions for the same data set.

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