High-angle electron scattering from amorphous silicon

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.

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

Physical Review B ◽

10.1103/physrevb.79.214110 ◽

2009 ◽

Vol 79 (21) ◽

Cited By ~ 81

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

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Small Angle Electron Scattering From Vacuum Condensed Metallic Films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100101657 ◽

1968 ◽

Vol 26 ◽

pp. 380-381

Author(s):

J. Silcox ◽

R. H. Wade

Keyword(s):

Electron Scattering ◽

Small Angle ◽

Ring Structure ◽

Two Dimensional ◽

Metallic Films ◽

Micro Structure ◽

Angle Scattering ◽

The Fourier Transform ◽

Source Of Information ◽

Kinematical Theory

Recent work has drawn attention to the possibilities that small angle electron scattering offers as a source of information about the micro-structure of vacuum condensed films. In particular, this serves as a good detector of discontinuities within the films. A review of a kinematical theory describing the small angle scattering from a thin film composed of discrete particles packed close together will be presented. Such a model could be represented by a set of cylinders packed side by side in a two dimensional fluid-like array, the axis of the cylinders being normal to the film and the length of the cylinders becoming the thickness of the film. The Fourier transform of such an array can be regarded as a ring structure around the central beam in the plane of the film with the usual thickness transform in a direction normal to the film. The intensity profile across the ring structure is related to the radial distribution function of the spacing between cylinders.

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Atomic Imaging of Crystals using Large-Angle Electron Scattering in STEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100179129 ◽

1990 ◽

Vol 48 (1) ◽

pp. 74-75

Author(s):

D.E. Jesson ◽

S. J. Pennycook

Keyword(s):

Wave Function ◽

Electron Scattering ◽

Numerical Solutions ◽

Large Angle ◽

Real Space ◽

High Angle ◽

Analytical Treatment ◽

Order Zero ◽

Experimental Conditions ◽

Ewald Sphere

It is well known that conventional atomic resolution electron microscopy is a coherent imaging process best interpreted in reciprocal space using contrast transfer function theory. This is because the equivalent real space interpretation involving a convolution between the exit face wave function and the instrumental response is difficult to visualize. Furthermore, the crystal wave function is not simply related to the projected crystal potential, except under a very restrictive set of experimental conditions, making image simulation an essential part of image interpretation. In this paper we present a different conceptual approach to the atomic imaging of crystals based on incoherent imaging theory. Using a real-space analysis of electron scattering to a high-angle annular detector, it is shown how the STEM imaging process can be partitioned into components parallel and perpendicular to the relevant low index zone-axis.It has become customary to describe STEM imaging using the analytical treatment developed by Cowley. However, the convenient assumption of a phase object (which neglects the curvature of the Ewald sphere) fails rapidly for large scattering angles, even in very thin crystals. Thus, to avoid unpredictive numerical solutions, it would seem more appropriate to apply pseudo-kinematic theory to the treatment of the weak high angle signal. Diffraction to medium order zero-layer reflections is most important compared with thermal diffuse scattering in very thin crystals (<5nm). The electron wave function ψ(R,z) at a depth z and transverse coordinate R due to a phase aberrated surface probe function P(R-RO) located at RO is then well described by the channeling approximation;

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Including Thermal Vibrations and Bonding in HAADF-STEM Image Simulation

Microscopy and Microanalysis ◽

10.1017/s1431927614002499 ◽

2014 ◽

Vol 20 (S3) ◽

pp. 154-155 ◽

Cited By ~ 1

Author(s):

Michael Odlyzko ◽

K. Andre Mkhoyan

Keyword(s):

Image Simulation ◽

Stem Image ◽

Thermal Vibrations

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Computer studies of fast ion trajectories in crystals

Canadian Journal of Physics ◽

10.1139/p68-064 ◽

1968 ◽

Vol 46 (6) ◽

pp. 503-516 ◽

Cited By ~ 60

Author(s):

D. V. Morgan ◽

D. van Vliet

Keyword(s):

Large Angle ◽

Classical Dynamics ◽

Perfect Lattice ◽

Fast Ions ◽

Angle Scattering ◽

Initial Work ◽

Fast Ion ◽

Thermal Vibrations ◽

Computer Studies ◽

Good Agreement

A computer program has been developed which follows the trajectories of fast ions in crystals, based on the assumption of classical dynamics and binary collisions. Initial work has been directed at various aspects of proton channeling in copper in the energy range 5–500 keV. The critical angle and distance of closest approach in a perfect lattice have been evaluated for both rows and planes and compare well with the predictions of the continuum model as developed by Lindhard (1965). We also discuss the overlap of close-packed rows and planes, and the modifications necessary to the basic theory when thermal vibrations are introduced. Experiments have been simulated directly by obtaining a statistical analysis of the velocity distribution of protons reflected from a (100) face of copper and transmitted through a thin (~1800 Â) crystal. In reflection, distinct minima were obtained along directions corresponding to close-packed rows and planes, in good agreement with experimental "blocking patterns" (Nelson 1967a). Transmission patterns also revealed a lack of large-angle scattering parallel to close-packed planes, analogous to the white arms observed experimentally with thinner crystals.

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

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.11.167 ◽

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.

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

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1959.0067 ◽

1959 ◽

Vol 250 (1262) ◽

pp. 337-345 ◽

Cited By ~ 19

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.

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Longitudinal magnetoresistance in silver and copper between 4.2 and 35 °K

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1967.0228 ◽

1967 ◽

Vol 302 (1468) ◽

pp. 83-98 ◽

Cited By ~ 18

Keyword(s):

Relaxation Time ◽

Electron Scattering ◽

Small Angle ◽

Time Approximation ◽

Long Wavelength ◽

Relaxation Time Approximation ◽

Angle Scattering ◽

Different Types ◽

Pure Single Crystal ◽

Longitudinal Magnetoresistance

Longitudinal magnetoresistance has been measured in a number of single crystals of silver and one very pure single crystal of copper in fields up to 65 kG and at temperatures between 4.2 and 35 °K. The purpose of the work has been to investigate the effects of different types of electron scattering, in particular small angle scattering. It has been found that at 4.2 °K impure crystals obey the relaxation time approximation fairly well, whereas crystals that have been purified (by oxidation at 800 °C) do not. Above 4.2 °K, the addition of long wavelength phonons has caused the magnetoresistance to increase substantially, as predicted by Pippard (1964), but agreement with Pippard’s theory is only qualitative. To account for the results a more detailed treatment of the scattering is required.

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Vibrational Properties of Si Microclusters and Comparison to the Amorphous Material

MRS Proceedings ◽

10.1557/proc-206-79 ◽

1990 ◽

Vol 206 ◽

Author(s):

Joseph L. Feldman ◽

Efthimios Kaxiras

Keyword(s):

Density Of States ◽

Interatomic Potential ◽

Amorphous Material ◽

Vibrational Properties ◽

Dynamical Matrix ◽

Vibrational Density Of States ◽

Remarkable Similarity ◽

Surface Reconstructions ◽

Amorphous Si ◽

Vibrational Density

ABSTRACTThe lattice vibrational properties of two clusters of Si atoms are studied using the Stillinger-Weber phenomenological interatomic potential to calculate the dynamical matrix. The clusters contain 33 and 45 atoms, and their structure was postulated from considerations of surface reconstructions in analogy to crystalline Si surfaces. A remarkable similarity to the vibrational density of states of amorphous Si is demonstrated especially for the 45 atom cluster.

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