convergent-beam diffraction from surfaces

1987 ◽  
Vol 45 ◽  
pp. 30-33
Author(s):  
J. A. Eades ◽  
A. E. Smith ◽  
D. F. Lynch
Keyword(s):  
Reciprocal Lattice ◽  
Three Dimensional ◽  
Grazing Incidence ◽  
Three Dimensions ◽  
Plane Figure ◽  
Transmission Electron ◽  
Convergent Beam ◽  
Beam Patterns ◽  
Beam Diffraction

It is quite simple (in the transmission electron microscope) to obtain convergent-beam patterns from the surface of a bulk crystal. The beam is focussed onto the surface at near grazing incidence (figure 1) and if the surface is flat the appropriate pattern is obtained in the diffraction plane (figure 2). Such patterns are potentially valuable for the characterization of surfaces just as normal convergent-beam patterns are valuable for the characterization of crystals.There are, however, several important ways in which reflection diffraction from surfaces differs from the more familiar electron diffraction in transmission.GeometryIn reflection diffraction, because of the surface, it is not possible to describe the specimen as periodic in three dimensions, nor is it possible to associate diffraction with a conventional three-dimensional reciprocal lattice.

Microdiffraction and convergent-beam diffraction from surfaces

1989 ◽  
Vol 47 ◽  
pp. 526-527
Author(s):  
J. A. Eades
Keyword(s):  
Surface Characterization ◽  
Normal Incidence ◽  
Grazing Incidence ◽  
High Energy ◽  
Large Area ◽  
High Energy Electrons ◽  
Convergent Beam ◽  
Beam Diffraction ◽  
Convergent Beam Diffraction

Microdiffraction from surfaces at near grazing incidence is an important method of surface characterization. It is very much akin to RHEED (reflection high-energy electron diffraction) except that in RHEED a large area of sample (∼ 1 mm2) contributes to the diffraction. In this respect the relationship between RHEED and surface microdiffraction is analogous to that between selected-area diffraction and microdiffraction in transmission. In addition RHEED systems usually have no post-specimen lenses and therefore operate at a fixed camera length.Surface microdiffraction can contribute important information for the characterization of surfaces but there are some important factors that make it more complex than in the case of convergent-beam diffraction in transmission.At grazing incidence, even with high-energy electrons, refraction at the surface is important -whereas in transmission (at near-normal incidence) it may be neglected.

Convergent-Beam Diffraction in the Characterization of Crystalline Phases

1985 ◽  
Vol 62 ◽  
Author(s):  
J. A. Eades ◽  
M. J. Kaufman ◽  
H. L. Fraser
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Zone Axis ◽  
Crystalline Materials ◽  
Powerful Technique ◽  
Transmission Electron ◽  
Convergent Beam ◽  
Beam Diffraction ◽  
Convergent Beam Diffraction

ABSTRACTConvergent-beam diffraction in the transmission electron microscope is a powerful technique for the characterization of crystalline materials. Examples are presented to show the way in which convergent-beam zone-axis patterns can be used to determine: the unit cell; the symmetry; the strain of a crystal. The patterns are also recognizable and so can be used, like fingerprints, to identify phases.

One of my Failures: Diffraction in the TEM

2011 ◽  
Vol 19 (1) ◽  
pp. 72-72 ◽  
Author(s):  
Alwyn Eades
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Standard Method ◽  
Transmission Electron ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Beam Diffraction ◽  
Convergent Beam Diffraction

There are two principal techniques for obtaining diffraction patterns in the transmission electron microscope (TEM). They are selected-area diffraction (SAD) and convergent-beam diffraction (CBED). CBED is quicker and easier to use, and it provides a much richer characterization of the sample. Thus, it is clear that CBED should be used in the vast majority of cases. It should be the diffraction technique that students learn first, and students should be taught to consider it the standard method of doing diffraction in the TEM.

Performance and applications of a field-emission gun TEM/STEM

1992 ◽  
Vol 50 (2) ◽  
pp. 942-943
Author(s):  
Judith M. Brock ◽  
Max T. Otten ◽  
Marc. J.C. de Jong
Keyword(s):  
Field Emission ◽  
High Resolution Imaging ◽  
High Quality ◽  
Small Energy ◽  
High Brightness ◽  
Small Probe ◽  
Resolution Imaging ◽  
Convergent Beam ◽  
Beam Patterns ◽  
Beam Diffraction

A Field Emission Gun (FEG) on a TEM/STEM instrument provides a major improvement in performance relative to one equipped with a LaB6 emitter. The improvement is particularly notable for small-probe techniques: EDX and EELS microanalysis, convergent beam diffraction and scanning. The high brightness of the FEG (108 to 109 A/cm2srad), compared with that of LaB6 (∼106), makes it possible to achieve high probe currents (∼1 nA) in probes of about 1 nm, whilst the currents for similar probes with LaB6 are about 100 to 500x lower. Accordingly the small, high-intensity FEG probes make it possible, e.g., to analyse precipitates and monolayer amounts of segregation on grain boundaries in metals or ceramics (Fig. 1); obtain high-quality convergent beam patterns from heavily dislocated materials; reliably detect 1 nm immuno-gold labels in biological specimens; and perform EDX mapping at nm-scale resolution even in difficult specimens like biological tissue.The high brightness and small energy spread of the FEG also bring an advantage in high-resolution imaging by significantly improving both spatial and temporal coherence.

Towards 3D image-based nanocrystallography by means of transmission electron goniometry

2004 ◽  
Vol 839 ◽  
Author(s):  
Peter Moeck ◽  
Wentao Qin ◽  
Philip B. Fraundorf
Keyword(s):  
Lattice Structure ◽  
Three Dimensions ◽  
Structural Defects ◽  
Transmission Electron ◽  
Means Of Transmission ◽  
Z Contrast ◽  
Individual Nanoparticles ◽  
Nanocrystal Model ◽  
The Ideal

ABSTRACTIt is well known that the crystallographic phase and morphology of many materials changes with the crystal size in the tens of nanometer range and that many nanocrystals possess structural defects in excess of their equilibrium levels. A need to determine the ideal and real structure of individual nanoparticles, therefore, arises. High-resolution phase-contrast transmission electron microscopy (TEM) and atomic resolution Z-contrast scanning TEM (STEM) when combined with transmission electron goniometry offer the opportunity of develop dedicated methods for the crystallographic characterization of nanoparticles in three dimensions. This paper describes tilt strategies for taking data from individual nanocrystals “as found”, so as to provide information on their lattice structure and orientation, as well as on the structure and orientation of their surfaces and structural defects. Internet based java applets that facilitate the application of this technique for cubic crystals with calibrated tilt-rotation and double-tilt holders are mentioned briefly. The enhanced viability of image-based nanocrystallography in future aberration-corrected TEMs and STEMs is illustrated on a nanocrystal model system.

Transmission Electron Diffraction Techniques for Nm Scale Strain Measurement in Semiconductors

1995 ◽  
Vol 405 ◽  
Author(s):  
J. Vanhellemont ◽  
K. G. F. Janssens ◽  
S. Frabboni ◽  
P. Smeys ◽  
R. Balboni ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Large Angle ◽  
Three Dimensional ◽  
Local Strain ◽  
Quantitative Information ◽  
Contrast Imaging ◽  
Transmission Electron ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Convergent Beam

AbstractAn overview is given of transmission electron microscopy techniques to address strain with nm scale spatial resolution. In particular the possibilities and limitations of (large angle) convergent beam electron diffraction ((LA)CBED) and electron diffraction contrast imaging (EDCI) techniques are discussed in detail. It will be shown by a few case studies that unique and quantitative information on local strain distributions can be obtained by the combined use of both (LA)CBED and EDCI in correlation with three dimensional finite element simulations of the strain distributions in the thinned specimen.

Local bond order parameters for accurate determination of crystal structures in two and three dimensions

2018 ◽  
Vol 20 (42) ◽  
pp. 27059-27068 ◽  
Author(s):  
Hossein Eslami ◽  
Parvin Sedaghat ◽  
Florian Müller-Plathe
Keyword(s):  
Crystal Structures ◽  
Bond Order ◽  
Accurate Determination ◽  
Three Dimensional ◽  
Order Parameters ◽  
Three Dimensions ◽  
Local Order ◽  
Crystalline Structures

Local order parameters for the characterization of liquid and different two- and three-dimensional crystalline structures are presented.

Using the TEM Condenser Lens to Switch between Image and Diffraction Modes

2013 ◽  
Vol 21 (2) ◽  
pp. 40-40
Author(s):  
Lydia Rivaud
Keyword(s):  
Electron Microscope ◽  
Diffraction Pattern ◽  
Transmission Electron Microscope ◽  
Condenser Lens ◽  
Selected Area Diffraction Pattern ◽  
Transmission Electron ◽  
Set Up ◽  
Convergent Beam ◽  
Beam Diffraction ◽  
Convergent Beam Diffraction

Central to the operation of the transmission electron microscope (TEM) (when used with crystalline samples) is the ability to go back and forth between an image and a diffraction pattern. Although it is quite simple to go from the image to a convergent-beam diffraction pattern or from an image to a selected-area diffraction pattern (and back), I have found it useful to be able to go between image and diffraction pattern even more quickly. In the method described, once the microscope is set up, it is possible to go from image to diffraction pattern and back by turning just one knob. This makes many operations on the microscope much more convenient. It should be made clear that, in this method, neither the image nor the diffraction pattern is “ideal” (details below), but both are good enough for many necessary procedures.

Inversion Domain Boundaries in GaN Grown on Sapphire

1996 ◽  
Vol 449 ◽  
Author(s):  
L. T. Romano ◽  
J.E. Northrup
Keyword(s):  
Dark Field ◽  
Hydride Vapor Phase Epitaxy ◽  
Dark Field Imaging ◽  
Inversion Domain ◽  
Transmission Electron ◽  
Domain Boundaries ◽  
Convergent Beam ◽  
Inversion Domain Boundaries ◽  
Field Imaging ◽  
Beam Diffraction

ABSTRACTInversion domain boundaries (IDBs) in GaN grown on sapphire (0001) were studied by a combination of high resolution transmission electron microscopy, multiple dark field imaging, and convergent beam diffraction. Films grown by molecular beam epitaxy (MBE), metalorganic vapor deposition (MOCVD), and hydride vapor phase epitaxy (HVPE) were investigated and all found to contain IDBs. Inversion domains (IDs) that extended from the surface to the interface were found to be columnar with facets on the {10–10} and {11–20} planes. Other domains ended within the film that formed IDBs on the (0001) and {1–102} planes. The domains were found to grow in clusters and connect at points along the boundary.

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