Electron Diffraction Study of Multilayer Structures with Partially Coherent Illumination

1985 ◽  
Vol 62 ◽  
Author(s):  
N. Otsuka ◽  
C. Choi ◽  
L. A. Kolodziejski ◽  
R. L. Gunshor
Keyword(s):  
Electron Diffraction ◽  
Incident Beam ◽  
Electron Diffraction Study ◽  
Diffraction Theory ◽  
Diffraction Spot ◽  
Multilayer Structures ◽  
Intensity Calculations ◽  
Diffraction Patterns ◽  
Monochromatic Source

ABSTRACTThe effect of partial coherency on electron diffraction patterns of Cd1−xMnxTe – Cd1−yMny Te superlattices has been investigated. Observed diffraction patterns are compared with intensity calculations performed using dynamical diffraction theory with a model of an extended incoherent monochromatic source. From this study, a new method of electron diffraction for characterization of multilayer structures can be developed. Under the condition that the lateral coherent distance of the incident beam covers two adjacent layers, diffraction beams arising from the two layers give rise to an interference fringe in a diffraction spot. With this type of diffraction pattern, one can determine the refractive index of a crystal in the multilayer structure.

Computer Indexing of Electron Diffraction Patterns Including the Effects of Lattice Symmetry

1977 ◽  
Vol 35 ◽  
pp. 22-23
Author(s):  
J. S. Lally ◽  
R. J. Lee
Keyword(s):  
Electron Diffraction ◽  
Zone Axis ◽  
Crystal Thickness ◽  
Double Diffraction ◽  
Automated Method ◽  
Lattice Symmetry ◽  
Intensity Calculations ◽  
Unknown Structure ◽  
Diffraction Patterns ◽  
Orientation Parameters

In the 50 year period since the discovery of electron diffraction from crystals there has been much theoretical effort devoted to the calculation of diffracted intensities as a function of crystal thickness, orientation, and structure. However, in many applications of electron diffraction what is required is a simple identification of an unknown structure when some of the shape and orientation parameters required for intensity calculations are not known. In these circumstances an automated method is needed to solve diffraction patterns obtained near crystal zone axis directions that includes the effects of systematic absences of reflections due to lattice symmetry effects and additional reflections due to double diffraction processes.Two programs have been developed to enable relatively inexperienced microscopists to identify unknown crystals from diffraction patterns. Before indexing any given electron diffraction pattern, a set of possible crystal structures must be selected for comparison against the unknown.

Error analysis of the crystal orientations and disorientations obtained by the classical electron backscatter diffraction technique

2015 ◽  
Vol 48 (3) ◽  
pp. 797-813 ◽  
Author(s):  
Farangis Ram ◽  
Stefan Zaefferer ◽  
Tom Jäpel ◽  
Dierk Raabe
Keyword(s):  
Electron Diffraction ◽  
Electron Backscatter Diffraction ◽  
Diffraction Theory ◽  
Classical Electron ◽  
Accuracy Measure ◽  
Electron Backscatter ◽  
Analytical Accuracy ◽  
Precision And Accuracy ◽  
Diffraction Patterns ◽  
Backscatter Diffraction

The fidelity – that is, the error, precision and accuracy – of the crystallographic orientations and disorientations obtained by the classical two-dimensional Hough-transform-based analysis of electron backscatter diffraction patterns (EBSPs) is studied. Using EBSPs simulated based on the dynamical electron diffraction theory, the fidelity analysis that has been previously performed using the patterns simulated based on the theory of kinematic electron diffraction is improved. Using the same patterns, the efficacy of a Fisher-distribution-based analytical accuracy measure for orientation and disorientation is verified.

DIFFRACTION OF 3.2 CM. ELECTROMAGNETIC WAVES BY CYLINDRICAL OBJECTS

1954 ◽  
Vol 32 (6) ◽  
pp. 372-380 ◽  
Author(s):  
A. B. McLay ◽  
S. T. Wiles
Keyword(s):  
Electromagnetic Waves ◽  
Incident Beam ◽  
Diffraction Theory ◽  
Central Peak ◽  
Beam Direction ◽  
Cylinder Axis ◽  
Scalar Diffraction ◽  
Conducting Cylinder ◽  
Scalar Diffraction Theory ◽  
Diffraction Patterns

Diffraction patterns of a brass tube and a hard rubber rod, each a cylinder of 1 in. diameter, in a nearly plane beam of square-wave modulated 3 cm. waves with electric vector parallel to the cylinder axis, have been measured in several planes transverse to the incident beam direction. Experimental results for the conducting cylinder agree closely with calculations based on scalar diffraction theory. Patterns of the dielectric rod show a pronounced central peak immediately behind the rod and other intensity effects differing from the conducting cylinder patterns, particularly in the vicinity of the shadow.

Microstructural variations as a function of δ in La2−xSrxNiO4+δ

1994 ◽  
Vol 9 (5) ◽  
pp. 1263-1271 ◽  
Author(s):  
M.J. Sayagués ◽  
A. Caneiro ◽  
J.M. González-Calbet ◽  
M. Vallet-Regí
Keyword(s):  
Electron Diffraction ◽  
Diffraction Study ◽  
Oxygen Content ◽  
Random Distribution ◽  
Electron Diffraction Study ◽  
Microstructural Characterization ◽  
Compositional Variations

A microstructural characterization of the La2−xSrxNiO4+δ (0 ⋚ x ⋚ 1) system, prepared with accurate control of the oxygen content, has been performed. The electron diffraction study shows the evolution of the accommodation of compositional variations as a function of δ. For δ > 0.06, interstitial oxygens are ordered, leading to new K2NiF4 superstructural types. Samples with δ < 0.06 accommodate the nonstoichiometry by means of random distribution of anionic vacancies.

Synthesis and Characterization of Srilankite Nanowires

2008 ◽  
Vol 8 (3) ◽  
pp. 1481-1488 ◽  
Author(s):  
Marguerite Germain ◽  
Philip Fraundorf ◽  
Sam Lin ◽  
Elena A. Guliants ◽  
Christopher E. Bunker ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Synthesis And Characterization ◽  
X Ray Diffraction ◽  
X Ray ◽  
Molar Ratios ◽  
Superlattice Structure ◽  
Titanate Nanowires ◽  
Alkaline Conditions ◽  
Diffraction Patterns

We describe the synthesis and characterization of srilankite (Ti2ZrO6) nanowires. The nanowires are produced via hydrothermal synthesis with a TiO2/ZrO2 mixture under alkaline conditions. The zirconium titanate nanowires have median diameters of 60 nm and median lengths of 800 nm with the 〈022〉 axis along the length of the nanowire. Electron microscopy, energy dispersive X-ray spectroscopy, powder X-ray diffraction, and electron diffraction are used to characterize the phases and compare nanowires produced with varying molar ratios of Ti and Zr. Electron diffraction patterns produced from single nanowires show highly crystalline nanowires displaying a compositional-ordering superlattice structure with Zr concentrated in bands within the crystal structure. This is in contrast to naturally occurring bulk srilankite where Zr and Ti are randomly substituted within the crystal lattice. Streaking is observed in the electron diffraction patterns suggesting short-range ordering within the superlattice structure.

Global least-squares determination of Eulerian angles from single electron diffraction patterns of tilted crystals

2000 ◽  
Vol 33 (4) ◽  
pp. 1088-1101 ◽  
Author(s):  
Eva Dimmeler ◽  
Rasmus R. Schröder
Keyword(s):  
Electron Diffraction ◽  
Least Squares ◽  
Three Dimensional ◽  
Test Sample ◽  
Single Electron ◽  
Dimensional Structure ◽  
Diffraction Spot ◽  
Linear Fit ◽  
Diffraction Patterns

Three-dimensional structure determination using electron diffraction of crystalline samples necessitates the determination of the Eulerian angles of tilted samples. For experimental tilt series, even with approximately known tilt, the resolution of the final three-dimensional reconstructions is reduced as a result of the large errors of the refined tilt angles and crystal axes positions. The presented new least-squares procedure determines the orientation of the crystal with very high accuracy from a single electron diffraction pattern. Instead of evaluating the averaged pattern geometry, each diffraction spot position is individually included in an analytical non-linear fit. This procedure is very stable against potential experimental errors, as demonstrated by Monte Carlo simulations. As a test sample, a three-dimensional microcrystal of an organic crystal compound was used. Contrary to the conventional method, which produced erroneous Miller indices for some reflections, the indexing obtained with the new algorithm was more consistent for each individual pattern. Preliminary data from frozen hydrated protein crystals, the samples of which are beam sensitive and for which only a few patterns can be recorded from a single crystal, indicate that the new angle determination promises to be particularly beneficial under such conditions.

A “filmless” method of acquiring and measuring electron diffraction patterns

1996 ◽  
Vol 54 ◽  
pp. 594-595 ◽  
Author(s):  
D. C. Dufner
Keyword(s):  
Electron Diffraction ◽  
User Interaction ◽  
Computer Programs ◽  
Specific Aspect ◽  
Convenient Means ◽  
Standard Procedures ◽  
Measurement And Analysis ◽  
Diffraction Patterns

Electron diffraction is one of most widely used techniques in the characterization of specimens in the TEM. With the advent of computerization, there is a growing trend toward automation of the measurement and analysis of electron diffraction patterns (EDPs). There are a number of computer programs used for measuring, indexing, and simulating EDPs, some of which are now commercially available. Many of these programs are stand-alone programs which either perform a specific aspect of EDP analysis or require significant user interaction, particularly in the measurement phase. In some cases, the lack of suitable algorithms for measuring EDPs usually limit these programs to the extent that users still have to perform standard procedures of measuring EDPs from negatives or prints to obtain the necessary values needed to complete the execution of these programs. Here, a more convenient means for online acquisition and measurement of EDPs is presented.

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