Dopant Site Location by Electron Channeling in Ion Implanted Silicon

1983 ◽  
Vol 31 ◽  
Author(s):  
S. J. Pennycook ◽  
J. Narayan ◽  
O.W. Holland
Keyword(s):  
Electron Microscope ◽  
Electron Micrographs ◽  
Site Location ◽  
Electron Channeling ◽  
Ion Channeling ◽  
Stages Of Growth ◽  
Early Stages ◽  
Simple Ratio ◽  
Implantation Profile

ABSTRACTA simple ratio technique using the phenomenon of electron channeling can be used to measure the substitutional concentrations of dopants in semiconductors on a submicron scale.A comparison was made between electron and ion channeling measurements on Si-Sb alloy samples having a range of nonsubstitutional fractions of Sb.Good agreement was obtained but both measurements indicated considerably more nonsubstitutional dopant than could be accounted for by precipitates observed in electron micrographs. The discrepancy can be explained if the precipitates are coherent in the early stages of growth and have their planes located interstitially with respect to the Si planes. The sensitivity of the electron channeling measurements to the implantation profile was investigated and found to be small.The determination of local dopant profiles in the electron microscope is described.

Ion Beam Study of Early Stages of Growth of GaN films on Sapphire

2002 ◽  
Vol 743 ◽  
Author(s):  
Eugen M. Trifan ◽  
David C. Ingram
Keyword(s):  
Photoelectron Spectroscopy ◽  
Ion Beam ◽  
Ex Situ ◽  
Crystallographic Axis ◽  
In Situ Characterization ◽  
X Ray ◽  
Ion Channeling ◽  
Stages Of Growth ◽  
Early Stages

ABSTRACTAn innovative approach for in-situ characterization has been used in this work to investigate the composition, growth mode, morphology and crystalline ordering of the early stages of growth of GaN films grown on sapphire by MOCVD for substrate temperatures in the range of 450°C to 1050°C. We have performed in-situ characterization by Rutherford Backscattering Spectroscopy (RBS), Ion Channeling, X-ray Photoelectron Spectroscopy (XPS), and Low Energy Electron Diffraction. Ex-situ the films have been characterized by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and thickness profilometry. The films have been grown in an in-house designed and build MOCVD reactor that is attached by UHV lines to the analysis facilities. RBS analysis indicated that the films have the correct stoichiometry, have variable thickness and for low substrate temperature completely cover the substrate while for temperatures 850°C and higher islands are formed that may cover as few as 5 percent of the substrate. From Ion Channeling and LEED we have determined the crystallographic phase to be wurtzite. The crystalline quality increases with higher deposition temperature and with thickness. The films are epitaxialy grown with the <0001> crystallographic axis and planes of the GaN films aligned with the sapphire within 0.2 degrees.

Nucleation in silver azide: an investigation by electron microscopy and diffraction

1955 ◽  
Vol 229 (1176) ◽  
pp. 135-142 ◽  
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Single Crystals ◽  
Electron Micrographs ◽  
The Other ◽  
Metallic Silver ◽  
Silver Azide ◽  
Cubic Lattice ◽  
Early Stages ◽  
Last Stage

The beam of an electron microscope has been used to decompose single crystals of silver azide into nitrogen and metallic silver. The decomposition was slow enough to allow electrondiffraction photographs and electron micrographs to be taken at various stages of the decomposition. From these observations it is possible to follow very closely the process of nucleation. The diffraction photographs show that two forms of silver result, one highly oriented and the other randomly oriented. The microscope identifies the two forms. The randomly oriented silver appears to separate at the boundaries of a substructure of the crystal. The highly oriented silver exists as discrete nuclei, of dimensions of the order 0.1 x 0.1 x 0.05p, probably formed near the surface of the silver azide crystal. The nuclei consist of normal metallic silver only at the end of the decomposition. There is no evidence for the formation in the early stages of a small speck of metallic silver which then grows. Rather, a nucleus is a region into which silver diffuses to build up a face-centred cubic lattice of parameter greater than that of normal silver, and which uses the silver positions in the silver azide lattice as the basis for this build-up. In the last stage a collapse to normal metallic silver takes place. During decomposition the size of a nucleus does not appear to change, but the density increases.

scholarly journals Arrangement of Subunits in Flagellar Microtubules

1974 ◽  
Vol 14 (3) ◽  
pp. 523-549 ◽  
Author(s):  
LINDA A. AMOS ◽  
A. KLUG
Keyword(s):  
Electron Microscope ◽  
Electron Micrographs ◽  
Helical Surface ◽  
3 Dimensional ◽  
Additional Information ◽  
Microscope Images ◽  
Staggered Arrangement ◽  
Diffraction Patterns ◽  
Tubule Wall

Electron micrographs of outer doublet tubules from flagella have been analysed by methods which make use of the computed diffraction patterns of electron-microscope images. Analysis of singlet A-tubules in the tips of flagella has led to a determination of the helical surface lattice of the A-subfibre, confirming that there are 13 longitudinal protofilaments in the tubule wall and that dimers in neighbouring protofilaments form a staggered arrangement, equivalent to the lattice with an axial periodicity of 8.0 nm predicted in earlier work. A low-resolution 3-dimensional image of the A-tubule has been reconstructed, which supports the evidence for an 8.0-nm-long heterodimer oriented along the protofilaments. The heterodimer is identified as a pair of 4.0-nm morphological units, which appear to be globular at this resolution. Filtered images have been obtained from doublet tubules which show that the B-subfibre is also made up of 8.0-nm dimers, but it differs from the A-tubule in that dimers in adjacent filaments are not in a staggered arrangement but are lined up obliquely at a shallow angle. Using the additional information about the hands of the lattices in the 2 subfibres which is presented in the accompanying paper, a model for the whole doublet has been proposed.

Utilizing Dark Field Electron Microscopy to Produce Lantern Slides

1974 ◽  
Vol 32 ◽  
pp. 116-117
Author(s):  
J. N. Meador ◽  
C. N. Sun ◽  
H. J. White
Keyword(s):  
Electron Microscope ◽  
Electron Micrographs ◽  
Dark Field ◽  
Limiting Factor ◽  
Clinical Laboratories ◽  
Field Electron ◽  
Time Element ◽  
Field Electron Microscopy ◽  
Dark Field Electron ◽  
Dark Field Micrographs

The electron microscope is being utilized more and more in clinical laboratories for pathologic diagnosis. One of the major problems in the utilization of the electron microscope for diagnostic purposes is the time element involved. Recent experimentation with rapid embedding has shown that this long phase of the process can be greatly shortened. In rush cases the making of projection slides can be eliminated by taking dark field electron micrographs which show up as a positive ready for use. The major limiting factor for use of dark field micrographs is resolution. However, for conference purposes electron micrographs are usually taken at 2.500X to 8.000X. At these low magnifications the resolution obtained is quite acceptable.

Spherulitic crystal growth in the prodissoconch larval of Crassostrea virginica

1983 ◽  
Vol 41 ◽  
pp. 518-519
Author(s):  
George G. Cocks ◽  
Louis Leibovitz ◽  
DoSuk D. Lee
Keyword(s):  
Crystal Structure ◽  
Crassostrea Virginica ◽  
Crystal Orientation ◽  
Developmental Changes ◽  
Gastrula Stage ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Stages Of Growth ◽  
Early Stages ◽  
Initial Deposition

Our understanding of the structure and the formation of inorganic minerals in the bivalve shells has been considerably advanced by the use of electron microscope. However, very little is known about the ultrastructure of valves in the larval stage of the oysters. The present study examines the developmental changes which occur between the time of conception to the early stages of Dissoconch in the Crassostrea virginica(Gmelin), focusing on the initial deposition of inorganic crystals by the oysters.The spawning was induced by elevating the temperature of the seawater where the adult oysters were conditioned. The eggs and sperm were collected separately, then immediately mixed for the fertilizations to occur. Fertilized animals were kept in the incubator where various stages of development were stopped and observed. The detailed analysis of the early stages of growth showed that CaCO3 crystals(aragonite), with orthorhombic crystal structure, are deposited as early as gastrula stage(Figuresla-b). The next stage in development, the prodissoconch, revealed that the crystal orientation is in the form of spherulites.

The Analysis of Dislocations Using a Symmetry Criterion

1972 ◽  
Vol 30 ◽  
pp. 660-661
Author(s):  
J. C. Ingram ◽  
P. R. Strutt ◽  
Wen-Shian Tzeng
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Displacement Field ◽  
Standard Technique ◽  
Residual Image ◽  
Symmetry Criterion

The invisibility criterion which is the standard technique for determining the nature of dislocations seen in the electron microscope can at times lead to erroneous results or at best cause confusion in many cases since the dislocation can still show a residual image if the term is non-zero, or if the edge and screw displacements are anisotropically coupled, or if the dislocation has a mixed character. The symmetry criterion discussed below can be used in conjunction with and in some cases supersede the invisibility criterion for obtaining a valid determination of the nature of the dislocation.The symmetry criterion is based upon the well-known fact that a dislocation, because of the symmetric nature of its displacement field, can show a symmetric image when the dislocation is correctly oriented with respect to the electron beam.

Feasibility of Molecular Structure Determination With a High Resolution Electron Microscope

1968 ◽  
Vol 26 ◽  
pp. 338-339
Author(s):  
T. A. Welton
Keyword(s):  
Electron Microscope ◽  
Substrate Surface ◽  
Helical Axis ◽  
Base Plane ◽  
Resolution Electron ◽  
High Resolution Electron Microscope ◽  
High Degree ◽  
Degree Of Order ◽  
Purine Pyrimidine

An ultimate design goal for an improved electron microscope, aimed at biological applications, is the determination of the structure of complex bio-molecules. As a prototype of this class of problems, we propose to examine the possibility of reading DNA sequence by an imaginable instrument design. This problem ideally combines absolute importance and relative simplicity, in as much as the problem of enzyme structure seems to be a much more difficult one.The proposed technique involves the deposition on a thin graphite lamina of intact double helical DNA rods. If the structure can be maintained under vacuum conditions, we can then make use of the high degree of order to greatly reduce the work involved in discriminating between the four possible purine-pyrimidine arrangements in each base plane. The phosphorus atoms of the back bone form in projection (the helical axis being necessarily parallel to the substrate surface) two intertwined sinusoids. If these phosphorus atoms have been located up to a certain point on the molecule, we have available excellent information on the orientation of the base plane at that point, and can then locate in projection the key atoms for discrimination of the four alternatives.

scholarly journals Meso-Scale Transmission Electron Microscope Tomography Applied for Wax Distribution in Toner Particles

2013 ◽  
Vol 19 (S5) ◽  
pp. 58-61 ◽  
Author(s):  
Mino Yang ◽  
Jun-Ho Lee ◽  
Hee-Goo Kim ◽  
Euna Kim ◽  
Young-Nam Kwon ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Three Dimensional ◽  
Chromatic Aberration ◽  
Laser Printer ◽  
Medium Voltage ◽  
Transmission Electron ◽  
Z Contrast ◽  
Contrast Image

AbstractDistribution of wax in laser printer toner was observed using an ultra-high-voltage (UHV) and a medium-voltage transmission electron microscope (TEM). As the radius of the wax spans a hundred to greater than a thousand nanometers, its three-dimensional recognition via TEM requires large depth of focus (DOF) for a volumetric specimen. A tomogram with a series of the captured images would allow the determination of their spatial distribution. In this study, bright-field (BF) images acquired with UHV-TEM at a high tilt angle prevented the construction of the tomogram. Conversely, the Z-contrast images acquired by the medium-voltage TEM produced a successful tomogram. The spatial resolution for both is discussed, illustrating that the image degradation was primarily caused by beam divergence of the Z-contrast image and the combination of DOF and chromatic aberration of the BF image from the UHV-TEM.

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