Imaging of III-V Compound Superlattices by Hrem and Rem

1986 ◽  
Vol 77 ◽  
Author(s):  
B. C. De Cooman ◽  
J. R. Conner ◽  
S. R. Summerfelt ◽  
S. McKernan ◽  
C. B. Carter ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Dark Field ◽  
Contrast Effects ◽  
Cross Sectional ◽  
Dark Field Imaging ◽  
Thin Foils ◽  
High Resolution Tem ◽  
Reflection Electron Microscopy ◽  
Field Imaging

ABSTRACTTwo techniques for the analysis of III-V compound superlattices are examined. It has been proposed that high-resolution TEM of [100]-oriented thin foils would give an improvement in layer contrast compared with [110]-oriented thin foils; it is shown here that the contrast of [100]-oriented superlattices is not necessarily better. Moreover, both high resolution and conventional dark-field imaging may be subject to significant diffraction contrast effects resulting from the bending of the reflecting planes near the surface of the sample. Reflection electron microscopy (REM) of cross-sectional (110) cleavage planes can also yield dark-field superlattice images and selected area RHEED patterns can in principle be used to determine reliably the superlattice strain as surface effects are minimized.

Reflection Electron Microscopy

1975 ◽  
Vol 33 ◽  
pp. 122-123
Author(s):  
P. E. Højlund Nielsen ◽  
J. M. Cowley
Keyword(s):  
Electron Microscopy ◽  
Single Crystal ◽  
Chromatic Aberration ◽  
Dark Field ◽  
Energy Spread ◽  
Crystal Surfaces ◽  
Single Crystal Surfaces ◽  
Dark Field Imaging ◽  
Reflection Electron Microscopy ◽  
Field Imaging

Reflection electron microscopy was widely used before 1960 for the study of surfaces. For the imaging diffuse scattered electrons was applied. For avoiding a severe foreshortening the surface was illuminated and viewed at fairly large angles. That resulted in a large energy spread of the scattered electrons so the resolution was limited to about 500Å due to chromatic aberration. Since such a resolution could be achieved more readily in scanning microscopes, the method was abandoned. However for single crystal surfaces the situation is entirely different. If the surface can be maintained reasonably clean, strong diffraction spots can be obtained and the energy spread in the diffracted beam is usually small; thus the imaging of the surface can be performed in a manner similar to the dark field imaging of a thin crystalline specimen.

Origin of Threefold Periodicity in High-Resolution Transmission Electron Microscopy Images of Thin Film Cubic SiC

1999 ◽  
Vol 5 (6) ◽  
pp. 420-427 ◽  
Author(s):  
U. Kaiser ◽  
A. Chuvilin ◽  
P.D. Brown ◽  
W. Richter
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Molecular Beam ◽  
Dark Field ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Field Imaging ◽  
Microscopy Images ◽  
Image Simulations

Abstract: High-resolution transmission electron microscopy (HRTEM) images of the [1–10] zone of cubic SiC layers grown by molecular beam epitaxy (MBE) often reveal regions of material exhibiting an unusual threefold periodicity. The same contrast was found in earlier works of Jepps and Page, who attributed this contrast in HRTEM images of polycrystalline SiC to the 9R-SiC polytype. In this report we demonstrate by HRTEM image simulations that the model of the 9R polytype and an alternative twinning model can fit qualitatively the experimental HRTEM images. However, by comparing the fast Fourier transform (FFT) patterns of the experiments and the simulations, as well as by using dark-field imaging, we show unambiguously that only the model of overlapping twinned 3C-SiC crystals fully agrees with the experiments.

A Preparation of High Resolution Standards for Electron Microscopy. Part II

1971 ◽  
Vol 29 ◽  
pp. 160-161
Author(s):  
Akira Tanaka ◽  
David F. Harling
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Carbon Black ◽  
Single Crystal ◽  
Dark Field ◽  
Graphitized Carbon Black ◽  
Graphitized Carbon ◽  
Dark Field Imaging ◽  
Crystal Films ◽  
Micro Holes

In the previous paper, the author reported on a technique for preparing vapor-deposited single crystal films as high resolution standards for electron microscopy. The present paper is intended to describe the preparation of several high resolution standards for dark field microscopy and also to mention some results obtained from these studies. Three preparations were used initially: 1.) Graphitized carbon black, 2.) Epitaxially grown particles of different metals prepared by vapor deposition, and 3.) Particles grown epitaxially on the edge of micro-holes formed in a gold single crystal film.The authors successfully obtained dark field micrographs demonstrating the 3.4Å lattice spacing of graphitized carbon black and the Au single crystal (111) lattice of 2.35Å. The latter spacing is especially suitable for dark field imaging because of its preparation, as in 3.), above. After the deposited film of Au (001) orientation is prepared at 400°C the substrate temperature is raised, resulting in the formation of many square micro-holes caused by partial evaporation of the Au film.

Detection of a point defect in a silicon single crystal by high-resolution TEM

1995 ◽  
Vol 53 ◽  
pp. 466-467
Author(s):  
M. Awaji
Keyword(s):  
High Resolution ◽  
Single Crystal ◽  
Point Defect ◽  
Point Defects ◽  
Noise Level ◽  
Dark Field ◽  
Silicon Single Crystal ◽  
High Resolution Image ◽  
Dark Field Imaging ◽  
Field Imaging

It is necessary to improve the resolution, brightness and signal-to-noise ratio(s/n) for the detection and identification of point defects in crystals. In order to observe point defects, multi-beam dark-field imaging is one of the useful methods. Though this method can improve resolution and brightness compared with dark-field imaging by diffuse scattering, the problem of s/n still exists. In order to improve the exposure time due to the low intensity of the dark-field image and the low resolution, we discuss in this paper the bright-field high-resolution image and the corresponding subtracted image with reference to a changing noise level, and examine the possibility for in-situ observation, identification and detection of the movement of a point defect produced in the early stage of damage process by high energy electron bombardment.The high-resolution image contrast of a silicon single crystal in the [10] orientation containing a triple divacancy cluster is calculated using the Cowley-Moodie dynamical theory and for a changing gaussian noise level. This divacancy model was deduced from experimental results obtained by electron spin resonance. The calculation condition was for the lMeV Berkeley ARM operated at 800KeV.

scholarly journals Annular Dark Field Imaging of Catalyst Nanoparticles in Single Shot Dynamic Transmission Electron Microscopy

2009 ◽  
Vol 15 (S2) ◽  
pp. 1082-1083
Author(s):  
D Masiel ◽  
B Reed ◽  
T LaGrange ◽  
ND Browning
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Dark Field ◽  
Single Shot ◽  
Catalyst Nanoparticles ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Annular Dark Field ◽  
Field Imaging

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Techniques for Characterising Artificial Layer Structures using Transmission Electron Microscopy

1987 ◽  
Vol 103 ◽  
Author(s):  
W. M. Stobbs
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Structural Changes ◽  
Dark Field ◽  
Multilayer Structures ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Layer Structures ◽  
Quantitative Characterisation ◽  
Field Imaging

ABSTRACTT.E.M. methods are described for the quantitative characterisation of the compositional and structural changes at interfaces and in homo- and hetero-phase multilayer structures. Many of the newer approaches described including the Fresnel and Centre Stop Dark Field Imaging Methods were developed specifically for such characterisations. The range of applications of each of the techniques is assessed as is the importance of delineating the limiting effects of inelastic and inelastic/elastic multiple scattering.

High Resolution TEM Studies On Palladium, Rhodium Nanoparticles

2001 ◽  
Vol 7 (S2) ◽  
pp. 1100-1101
Author(s):  
M. José-Yacamán ◽  
M. Marín-Almazo ◽  
J.A. Ascencio
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Indirect Evidence ◽  
High Resolution Electron Microscopy ◽  
Dark Field ◽  
Rhodium Nanoparticles ◽  
Resolution Electron ◽  
Annular Dark Field ◽  
High Resolution Tem ◽  
Important Field

The field of catalysis is one of the most important areas of the nano-sciences for many years. in deed the goal of having a catalyst, with the maximum active area exposed to a chemical reaction, has produced enormous amount of research in nanoparticles. Particularly, the metal nanoparticles study is a very important field in catalysis. Electron Microscopy is one of the techniques that have played a mayor role on studding nanoparticles. Since bright field images, dark field techniques, to the high-resolution atomic images of nanoparticles and more recently the High Angle Annular dark field images or Z-contrast. However this technique provides only indirect evidence of the atomic arrangements on the particles. High Resolution Electron Microscopy (HREM) still appears as a very powerful technique to study nanoparticles and their internal structure. Among the most interesting metals to study is the palladium, which acts for instance as excellent catalyst for hydrogenation of unsaturated hydrocarbons and has many other applications such as environmental catalysts.

HREM Studies of Structural Changes Induced by Phase Transformations in Zirconia Powders

1990 ◽  
Vol 48 (1) ◽  
pp. 24-25
Author(s):  
M.G. Blanchin ◽  
G. Nihoul ◽  
E. Bernstein
Keyword(s):  
Electron Microscopy ◽  
Phase Transformations ◽  
Structural Changes ◽  
Dark Field ◽  
Powder Materials ◽  
Aggregation State ◽  
Dark Field Imaging ◽  
High Resolution Tem ◽  
Hydrated Zirconium ◽  
Zirconia Powders

The use of microcrystalline (submicron) and nanocrystalline (≤10nm) particles as powder materials for sintering of advanced ceramics like oxide-based ceramics or high-Tc superconductors , requires new techniques for characterization. Thus classical optical microscopy or even scanning electron microscopy are no longer effective for examination of 1-10 nm particles. In previous work we developed quantitative analysis of transmission electron microscopy (TEM) observations at medium resolution (0.4-1 nm, typically) to study morphology, size distribution, agglomeration and/or aggregation state of elementary powder particles characterized by bright- and dark - field imaging as well as diffraction TEM techniques.Here the high resolution TEM (HREM) techniques (at 200 kV) have been used to investigate phase transformations occuring in ultrafine zirconia powders processed by calcination of an amorphous hydrated zirconium oxide prepared at low temperature. X-ray examination showed the sequence : amorphous , cubic (C) or tetragonal (T) , monoclinic (M), at increasing temperatures.

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