scholarly journals Insights on Diffraction

2002 ◽  
Vol 10 (2) ◽  
pp. 34-35
Author(s):  
Alwyn Eades
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Flat Specimen ◽  
Kikuchi Lines ◽  
Different Parts

This article presents ideas on some topics related to electron diffraction in the TEM. These are in regard to topics that I have come to think of as standard parts of what it means to do microscopy. However, they represent insights that not all users share (or even agree with, maybe).Kikuchi lines are of great use in orienting a sample. Unfortunately, in modern microscopes, Kikuchi lines are not seen in selected-area diffraction (SAD). This is because immersion lenses send parallel electrons, from different parts of the sample (like the Kikuchi lines from a flat specimen), to different places in the diffraction pattern.

Topics in Electron Diffraction (TEM): A Tutorial

2001 ◽  
Vol 7 (S2) ◽  
pp. 764-765
Author(s):  
J. A. Eades
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Flat Specimen ◽  
Large Area ◽  
Kikuchi Lines ◽  
Difficult Subject ◽  
Different Parts

Introduction. Electron diffraction is sometimes considered to be a “difficult subject”. It is certainly one that can not be covered in the space available here. Rather this tutorial will present a few specific aspects of the topic. The topics have been chosen in the hope that they will provide illumination that spreads more widely than just onto the material presented. Several books treat electron diffraction with more generality.Kikuchi lines Kikuchi lines are of great use in orienting a sample. Unfortunately, in modern microscopes, Kikuchi lines are not seen in selected-area diffraction (SAD). This is because immersion lenses send parallel electrons, from different parts of the sample (like the Kikuchi lines from a flat specimen), to different places in the diffraction pattern. Thus Kikuchi lines are blurred and generally not useful whenever, as in SAD patterns, a large area of the sample contributes to the diffraction pattern.

Analysis of electron-diffraction intensity profiles using a photodiode-array detection system

1983 ◽  
Vol 41 ◽  
pp. 322-323
Author(s):  
J. B. Warren
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Detection System ◽  
High Energy ◽  
Photographic Emulsion ◽  
Diffraction Intensity ◽  
Silicon Photodiode ◽  
Photodiode Array Detection ◽  
Analog To Digital ◽  
Photodiode Array

Electron diffraction intensity profiles have been used extensively in studies of polycrystalline and amorphous thin films. In previous work, diffraction intensity profiles were quantitized either by mechanically scanning the photographic emulsion with a densitometer or by using deflection coils to scan the diffraction pattern over a stationary detector. Such methods tend to be slow, and the intensities must still be converted from analog to digital form for quantitative analysis. The Instrumentation Division at Brookhaven has designed and constructed a electron diffractometer, based on a silicon photodiode array, that overcomes these disadvantages. The instrument is compact (Fig. 1), can be used with any unmodified electron microscope, and acquires the data in a form immediately accessible by microcomputer.Major components include a RETICON 1024 element photodiode array for the de tector, an Analog Devices MAS-1202 analog digital converter and a Digital Equipment LSI 11/2 microcomputer. The photodiode array cannot detect high energy electrons without damage so an f/1.4 lens is used to focus the phosphor screen image of the diffraction pattern on to the photodiode array.

Electron Diffraction Analysis of Microtwin Structures in Regrown (III) Silicon

1982 ◽  
Vol 40 ◽  
pp. 460-461
Author(s):  
P. Ling ◽  
R. Gronsky ◽  
J. Washburn
Keyword(s):  
Electron Diffraction ◽  
Ion Implantation ◽  
Diffraction Analysis ◽  
Diffraction Pattern ◽  
Direct Consequence ◽  
The Other ◽  
Electron Diffraction Analysis ◽  
Defect Microstructures ◽  
Ion Implanted

The defect microstructures of Si arising from ion implantation and subsequent regrowth for a (111) substrate have been found to be dominated by microtwins. Figure 1(a) is a typical diffraction pattern of annealed ion-implanted (111) Si showing two groups of extra diffraction spots; one at positions (m, n integers), the other at adjacent positions between <000> and <220>. The object of the present paper is to show that these extra reflections are a direct consequence of the microtwins in the material.

Convergent Beam Electron Diffraction

1978 ◽  
Vol 36 (3) ◽  
pp. 304-315
Author(s):  
G. Lehmpfuhl
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Crystal Surface ◽  
Diffraction Spot ◽  
Crystal Thickness ◽  
Large Area ◽  
Electron Microscopic ◽  
Additional Information ◽  
Microscopic Investigations

Introduction In electron microscopic investigations of crystalline specimens the direct observation of the electron diffraction pattern gives additional information about the specimen. The quality of this information depends on the quality of the crystals or the crystal area contributing to the diffraction pattern. By selected area diffraction in a conventional electron microscope, specimen areas as small as 1 µ in diameter can be investigated. It is well known that crystal areas of that size which must be thin enough (in the order of 1000 Å) for electron microscopic investigations are normally somewhat distorted by bending, or they are not homogeneous. Furthermore, the crystal surface is not well defined over such a large area. These are facts which cause reduction of information in the diffraction pattern. The intensity of a diffraction spot, for example, depends on the crystal thickness. If the thickness is not uniform over the investigated area, one observes an averaged intensity, so that the intensity distribution in the diffraction pattern cannot be used for an analysis unless additional information is available.

The structure of amorphous and polycrystalline materials using energy-filtered RDF analysis

1992 ◽  
Vol 50 (2) ◽  
pp. 1190-1191
Author(s):  
David Cockayne ◽  
David McKenzie
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Density Function ◽  
Electron Diffraction Pattern ◽  
Polycrystalline Materials ◽  
Nearest Neighbour ◽  
X Ray ◽  
Selected Area Electron Diffraction ◽  
Reduced Density ◽  
System F

The technique of Electron Reduced Density Function (RDF) analysis has ben developed into a rapid analytical tool for the analysis of small volumes of amorphous or polycrystalline materials. The energy filtered electron diffraction pattern is collected to high scattering angles (currendy to s = 2 sinθ/λ = 6.5 Å-1) by scanning the selected area electron diffraction pattern across the entrance aperture to a GATAN parallel energy loss spectrometer. The diffraction pattern is then converted to a reduced density function, G(r), using mathematical procedures equivalent to those used in X-ray and neutron diffraction studies.Nearest neighbour distances accurate to 0.01 Å are obtained routinely, and bond distortions of molecules can be determined from the ratio of first to second nearest neighbour distances. The accuracy of coordination number determinations from polycrystalline monatomic materials (eg Pt) is high (5%). In amorphous systems (eg carbon, silicon) it is reasonable (10%), but in multi-element systems there are a number of problems to be overcome; to reduce the diffraction pattern to G(r), the approximation must be made that for all elements i,j in the system, fj(s) = Kji fi,(s) where Kji is independent of s.

Determination of hydrogen ordering within the β-RH2+xphase (R= Ho, Y) using electron diffraction techniques

2000 ◽  
Vol 33 (5) ◽  
pp. 1246-1252 ◽  
Author(s):  
Elizabeth J. Grier ◽  
Amanda K. Petford-Long ◽  
Roger C. C. Ward
Keyword(s):  
Electron Diffraction ◽  
Neutron Scattering ◽  
Diffraction Pattern ◽  
Computer Simulations ◽  
Fluorite Structure ◽  
Long Range Order ◽  
Hydrogen Atoms ◽  
Ordered Structures ◽  
Diffraction Patterns

Computer simulations of the electron diffraction patterns along the [\bar{1}10] zone axes of four ordered structures within the β-RH2+xphase, withR= Ho or Y, and 0 ≤x≤ 0.25, have been performed to establish whether or not the hydrogen ordering could be detected using electron diffraction techniques. Ordered structures within otherRH2+x(R= Ce, Tb) systems have been characterized with neutron scattering experiments; however, for HoH(D)2+x, neutron scattering failed to characterize the superstructure, possibly because of the lowxconcentration or lack of long-range order within the crystal. This paper aims to show that electron diffraction could overcome both of these problems. The structures considered were the stoichiometric face-centred cubic (f.c.c.) fluorite structure (x= 0), theD1 structure (x= 0.125), theD1astructure (x= 0.2) and theD022structure (x= 0.25). In the stoichiometric structure, with all hydrogen atoms located on the tetrahedral (t) sites, only the diffraction pattern from the f.c.c. metal lattice was seen; however, for the superstoichiometric structures, with the excess hydrogen atoms ordered on the octahedral (o) sites, extra reflections were visible. All the superstoichiometric structures showed extra reflections at the (001)f.c.c.and (110)f.c.c.type positions, with structureD1 also showing extra peaks at (½ ½ ½)f.c.c.. These reflections are not seen in the simulations at similar hydrogen concentrations with the hydrogen atoms randomly occupying theovacancies.

Photographical Record of the Dispersion Surface in Rotating Crystal Electron Diffraction Pattern

1968 ◽  
Vol 23 (4) ◽  
pp. 544-549 ◽  
Author(s):  
G. Lehmpfuhl ◽  
A. Reissland
Keyword(s):  
Dynamical System ◽  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Electron Diffraction Pattern ◽  
Plane Waves ◽  
Zone Axis ◽  
System Of Equations ◽  
Wave Fields ◽  
Dispersion Surface ◽  
Crystal Electron

Strong interacting wave fields in a wedge-shaped crystal are separated into different plane waves when leaving the crystal and reveal points on the dispersion surface. By rotating the crystal while moving the film one obtains a photographical record of a section through the dispersion surface which may be compared with theory. An experiment with a macroscopic MgO wedge is reported. The 002 interference with excitation error nearly zero was recorded near the [I10] zone axis while rotating the crystal about the [001] axis. The diagrams are compared with dynamical 17-beam calculations. The results show that a reduction of the infinite dynamical system of equations to 17 equations is correct under these special geometrical conditions.

In-Situ Transmission Electron Microscopy Investigation of Aluminum Induced Crystallization of Amorphous Silicon

2008 ◽  
Vol 1066 ◽  
Author(s):  
Ram Kishore ◽  
Renu Sharma ◽  
Satoshi Hata ◽  
Noriyuki Kuwano ◽  
Yoshitsuga Tomokiyo ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Amorphous Silicon ◽  
Diffraction Pattern ◽  
Electron Diffraction Pattern ◽  
Polycrystalline Silicon ◽  
Nanocrystalline Silicon ◽  
Transmission Electron ◽  
In Situ Heating ◽  
Induced Crystallization

ABSTRACTThe interaction of amorphous silicon and aluminum films to achieve polycrystalline silicon has been investigated using transmission electron microscope equipped with in-situ heating holder. Carbon coated nickel grids were used for TEM studies. An ultra high vacuum cluster tool was used for the deposition of a ∼50nm a-Si films and a vacuum deposition system was used to deposit a ∼50nm Al films on a-Si film. The microstructural features and electron diffraction in the plain view mode were observed with increase in temperature starting from room temperature to 275 °C. The specimen was loaded inside TEM heating holder. The temperature was measured and kept constant for 5 minutes during which the microstructure at fixed magnification of X63K was recorded and the electron diffraction pattern of the same area was also recorded. The temperature was then increase and fixed at desired value and microstructure and EDP were again recorded. The temperatures used in this experiment were 30, 100, 150, 200, 225, 275°C. A sequential change in microstructural features and electron diffraction pattern due to interfacial diffusion of boundary between Al and amorphous Si was investigated. Evolution of polycrystalline silicon with randomly oriented grains as a result of a-Si and Al interaction was revealed. After the in-situ heating experiment the specimen was subjected to high resolution TEM and EDS investigations after removing the excess Al. The EDS analysis of the crystallized specimen was performed to locate the Al distribution in the crystallized silicon. These studies show that the Al induced crystallization process can be used to prepare polycrystalline as well as nanocrystalline silicon by controlling the in-situ annealing parameters. The investigations are very useful as the nanocrystalline silicon is being investigated for its use in developing high efficiency silicon solar structures.

Sign in / Sign up

Export Citation Format

Share Document