Investigation of the Displacement Threshold of Si in 4H SiC

2006 ◽  
Vol 527-529 ◽  
pp. 481-484 ◽  
Author(s):  
W. Sullivan ◽  
John W. Steeds
Keyword(s):  
Electron Microscope ◽  
Low Temperature ◽  
Electron Energy ◽  
Transmission Electron Microscope ◽  
Low Energy ◽  
Electron Dose ◽  
Displacement Threshold ◽  
Transmission Electron ◽  
Low Energy Electrons ◽  
Low Temperature Photoluminescence

Samples of 4H SiC, both n- and p-doped, have been irradiated with low-energy electrons in a transmission electron microscope. The dependence of the silicon vacancy-related V1 ZPL doublet (~860nm) on electron energy and electron dose has been investigated by low temperature photoluminescence spectroscopy. Furthermore, this luminescence centre has been studied across a broad range of samples of various doping levels. Some annealing characteristics of this centre are reported.

Comparison of Techniques for EELS Mapping in Biology

1996 ◽  
Vol 54 ◽  
pp. 300-301
Author(s):  
R.D. Leapman ◽  
S.B. Andrews
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Image Data ◽  
Beam Current ◽  
Quantitative Information ◽  
Acquisition Time ◽  
Uniform Thickness ◽  
Electron Dose ◽  
Array Detectors ◽  
Transmission Electron

Elemental mapping of biological specimens by electron energy loss spectroscopy (EELS) can be carried out both in the scanning transmission electron microscope (STEM), and in the energy-filtering transmission electron microscope (EFTEM). Choosing between these two approaches is complicated by the variety of specimens that are encountered (e.g., cells or macromolecules; cryosections, plastic sections or thin films) and by the range of elemental concentrations that occur (from a few percent down to a few parts per million). Our aim here is to consider the strengths of each technique for determining elemental distributions in these different types of specimen.On one hand, it is desirable to collect a parallel EELS spectrum at each point in the specimen using the ‘spectrum-imaging’ technique in the STEM. This minimizes the electron dose and retains as much quantitative information as possible about the inelastic scattering processes in the specimen. On the other hand, collection times in the STEM are often limited by the detector read-out and by available probe current. For example, a 256 x 256 pixel image in the STEM takes at least 30 minutes to acquire with read-out time of 25 ms. The EFTEM is able to collect parallel image data using slow-scan CCD array detectors from as many as 1024 x 1024 pixels with integration times of a few seconds. Furthermore, the EFTEM has an available beam current in the µA range compared with just a few nA in the STEM. Indeed, for some applications this can result in a factor of ~100 shorter acquisition time for the EFTEM relative to the STEM. However, the EFTEM provides much less spectral information, so that the technique of choice ultimately depends on requirements for processing the spectrum at each pixel (viz., isolated edges vs. overlapping edges, uniform thickness vs. non-uniform thickness, molar vs. millimolar concentrations).

Biological X-ray Microanalysis: The Past, Present Practices, and Future Prospects

2001 ◽  
Vol 7 (2) ◽  
pp. 211-219 ◽  
Author(s):  
Patrick Echlin
Keyword(s):  
Electron Microscope ◽  
Low Temperature ◽  
Transmission Electron Microscope ◽  
Low Voltage ◽  
High Energy ◽  
Scanning Transmission Electron Microscope ◽  
X Ray ◽  
Ambient Temperatures ◽  
Advantages And Disadvantages ◽  
Transmission Electron

Abstract A brief description is given of the events surrounding the development of biological X-ray microanalysis during the last 30 years, with particular emphasis on the contribution made by research workers in Cambridge, UK. There then follows a broad review of some applications of biological X-ray microanalysis. A more detailed consideration is given to the main thrust of current procedures and applications that are, for convenience, considered as four different kinds of samples. Thin frozen dried sections which are analyzed at ambient temperatures in a transmission electron microscope (TEM); semithin frozen dried sections which are analyzed at low temperature in a scanning transmission electron microscope (STEM); thick frozen hydrated sections which are analyzed at low temperature in a scanning electron microscope (SEM), and bulk samples which are analyzed at low temperature in the same type of instrument. A brief outline is given of the advantages and disadvantages of performing low-voltage, low-temperature X-ray microanalysis on frozen hydrated bulk biological material. The article concludes with a consideration of alternative approaches to in situ analysis using either high-energy beams or visible and near-visible photons.

Analysis of Diffraction Contrast as A Function of Energy Loss in Energy Filtering Transmission Electron Microscope (EFTEM) Imaging and Possible Implications on High-Resolution Compositional Mapping

1999 ◽  
Vol 5 (S2) ◽  
pp. 620-621
Author(s):  
K.T. Moore ◽  
J.M. Howe
Keyword(s):  
Electron Microscope ◽  
Energy Loss ◽  
Electron Energy ◽  
Transmission Electron Microscope ◽  
Diffraction Contrast ◽  
Energy Filtering ◽  
Background Removal ◽  
Transmission Electron ◽  
Important Relationship ◽  
Electron Energy Loss

The dependence of diffraction contrast on electron energy loss is an important relationship that needs to be understood because of its potential effect on energy-filtering transmission electron microscope (EFTEM) images. Often when either a two-window jump-ratio image or a three-window elemental map is produced diffraction contrast is not totally eliminated and contributes to the intensity of the final EFTEM image. Background removal procedures often are unable to completely account for intensity changes due to dynamical effects (i.e., elastic scattering) that occur between images acquired at different energy losses, leaving artifacts in the final EFTEM image.In this study, the relationship between diffraction contrast and electron energy loss was investigated by obtaining EFTEM images of a bend contour in aluminum in 100 eV increments from 0 to 1000 eV (Fig. 1). EFTEM images were acquired a JOEL 2010F FEG TEM with a Gatan imaging filter (GIF) at a microscope magnification of 8 kX using a 1 eV/pixel dispersion, 2X binning (512 x 512) and exposure times ranging from 0.25 s for 0 eV energy loss up to 132 sec for 1000 eV energy loss.

Mapping the Subcellular Distribution of Calcium in Depolarized Neurons by Electron Energy Loss Spectrum Imaging

2000 ◽  
Vol 6 (S2) ◽  
pp. 162-163
Author(s):  
S.B. Andrews ◽  
J. Hongpaisan ◽  
N.B. Pivovarova ◽  
D.D. Friel ◽  
R.D. Leapman
Keyword(s):  
Electron Microscope ◽  
Energy Loss ◽  
Electron Energy ◽  
Transmission Electron Microscope ◽  
Detection Threshold ◽  
Electron Energy Loss Spectrum ◽  
Acquisition Time ◽  
Transmission Electron ◽  
Spectrum Imaging ◽  
Electron Energy Loss

In the context of biological specimens, it is in principle desirable to quantitatively map, rather than just point analyze, the distribution of physiologically important elements, and to do so at subcellular resolution. Presently, this can be accomplished by electron energy loss spectrum-imaging (EELSI) in both the scanning transmission electron microscope (STEM) and the energy-filtering transmission electron microscope (EFTEM). Until recently, this approach has been of limited value for mapping the particularly important element Ca, mainly because intracellular total Ca concentrations are normally quite low (<5 mmol/kg dry weight) and because the background in the vicinity of the Ca L23 edge is complex and requires precise background modeling to extract the very weak Ca signals. As a result, the Ca signal is usually not high enough to reach detection threshold during a practical EELSI acquisition time.

Analysis of Spherical Carbides Formed in Chromium Added Hypereutectoid Bearing Steels

2007 ◽  
Vol 539-543 ◽  
pp. 4866-4871 ◽  
Author(s):  
Atsushi Yamamoto ◽  
Katsuhiko Inoue ◽  
Harushige Tsubakino
Keyword(s):  
Electron Microscope ◽  
Synchrotron Radiation ◽  
Low Temperature ◽  
Transmission Electron Microscope ◽  
Bearing Steel ◽  
Bearing Steels ◽  
Transmission Electron ◽  
Synchrotron Radiation Diffraction ◽  
M23c6 Type ◽  
Means Of Transmission

Microstructures in a bearing steel, JIS SUJ2, have been observed and analyzed in detail by means of transmission electron microscope and synchrotron radiation diffraction in SPring-8. Spherodized carbides in the steel are generally recognized as spherical cementite particles, but some of them have been clearly shown to be M23C6 type of carbide in this study. The shapes and sizes of these two types of carbides are similar to each other. On the martensitic matrix of the steel, it is believed to be stable at relatively low temperature, but it is also shown to be decomposed to form cementite by prolonged aging at 383 K, which provides a reason for decrease in hardness in standard hardness blocks, previously reported by the authors.

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