Application of parallel recorded EELS to analysis of beam-sensitive organic compounds

1988 ◽  
Vol 46 ◽  
pp. 632-633
Author(s):  
R.D. Leapman
Keyword(s):  
Electron Microscope ◽  
Organic Compounds ◽  
Detection Efficiency ◽  
Electron Dose ◽  
Recording Time ◽  
Parallel Detection ◽  
Optimum Technique ◽  
Tem Mode ◽  
Analysis System ◽  
Counting Statistics

Electron energy loss spectroscopy (EELS) is the optimum technique for studying specific mass loss of light elements from organic compounds under irradiation in the electron microscope. The recent availability of parallel detection systems has provided a factor of approximately 1000 improvement in detection efficiency compared with serial detection. This implies a corresponding reduction in recording time or a reduction in the electron dose needed to obtain sufficient counting statistics for elemental detection. In addition, parallel detection allows us to perform “real-time” EELS, i.e. to observe the actual decay of characteristic peaks in the spectrum.EELS spectra have been recorded with a Gatan model 607 spectrometer fitted with a Gatan model 666 parallel detector based on a 1024 channel photodiode array. Data were transfered to a Tracor Northern TN5500 analysis system for display and processing. Samples were examined at 100 keV beam energy in a Hitachi H700H electron microscope operated in the TEM mode at 1000X to 10000X magnification and with a 30 mrad collection semi-angle defined by the objective aperture.

Performance of the Gatan PEELS™ on the VG HB501 STEM

1989 ◽  
Vol 47 ◽  
pp. 410-411
Author(s):  
Ondrej L. Krivanek ◽  
James H. Paterson ◽  
Helmut R. Poppa
Keyword(s):  
Electron Microscope ◽  
Energy Loss ◽  
Beam Energy ◽  
Detection Efficiency ◽  
Beam Current ◽  
Scanning Transmission Electron Microscope ◽  
Parallel Detection ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Electron Energy Loss

Parallel-detection electron energy-loss spectrometers offer several hundred times the detection efficiency of serial-detection spectrometers, as well as improved energy resolution. These advantages should be especially important when using a scanning transmission electron microscope (STEM) with a cold field emission gun (FEG), in which the available beam current is typically 10 to 100 times less than in a conventional TEM, while the beam energy spread is typically only 0.3 eV. We have therefore investigated the performance of the Gatan parallel-detection spectrometer (Gatan model 666 PEELS™) when mounted on the VG HB501 FEG STEM.

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).

The use of an analytical electron microscope in the analysis of mineral dusts

1977 ◽  
Vol 286 (1336) ◽  
pp. 625-638 ◽  
Keyword(s):  
Electron Microscope ◽  
Fine Particles ◽  
Dust Particles ◽  
Single Particles ◽  
Bulk Analysis ◽  
Mineral Concentration ◽  
Size And Shape ◽  
Mineral Particles ◽  
Analysis System ◽  
Bulk Chemistry

Dust samples, whatever their source, usually consist of small quantities of very fine particles from which the following information is necessary: (a) the morphology of the mineral particles in the dust, i.e. size and shape; (b) the identity of the mineral particles in the dust; (c) the proportion of each mineral contained in the dust; (d) the mineral concentration in the sample of air, water or biological material from which the dust was recovered. Information is also required as rapidly as possible from a single preparation so that many samples may be analysed on a routine basis. This paper will outline how this information can be obtained by using an electron microscope analysis system. With such an instrument, dust particles of all sizes may be observed and their size and shape obtained, while the electron microprobe may be used to analyse single particles to determine their chemistry and identify them. The bulk chemistry of the dust may be obtained in a similar manner by analysing large numbers of particles simultaneously. By using the chemical data obtained from single particles and also the bulk chemistry of the sample, the mineral composition of the dust may be computed. A measure of the mass of dust being analysed can be obtained from a measurement of the X-ray count rate obtained during bulk analysis, measurement of the incident electron-beam intensity and reference to an instrument calibration curve.

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.

Detection of small amounts of Fe and Nb in Zr-2.5wt%Nb pressure tubes

1997 ◽  
Vol 3 (S2) ◽  
pp. 969-970
Author(s):  
H. Müllejans ◽  
J. Thomas ◽  
O. Kienzle ◽  
M. Griffiths ◽  
M. Rühle
Keyword(s):  
Signal To Noise Ratio ◽  
Simple Estimate ◽  
The Past ◽  
Β Phase ◽  
Subtraction Procedure ◽  
Digital Pulse ◽  
Pressure Tubes ◽  
Ge Detector ◽  
Analysis System ◽  
Counting Statistics

The distribution of Nb and Fe in Zr-2.5wt%Nb pressure tube alloys has been of interest, in particular the effects of neutron irradiation. Both Fe in the β-phase and Nb in the α-phase are present in levels below lwt% and fluctuations of these elements in different parts of a specimen or between different specimens are of interest. In EDS quantification the signal-to-noise ratio and hence the detection limit is determined by the signals but depends also on the data analysis, in particular the background subtraction procedure. Here we compare the noise as given by the commercial analysis software to a simple estimate based on counting statistics. We used a VG HB 501 UX equipped with a thin window HP Ge detector, digital pulse processor and Voyager 3105 data acquisition and analysis system (Noran).In the past artefacts of Fe, Ni and Cu had been observed in EDS spectra, even for materials which did not contain any impurities of these elements.

Study on Effect and Mechanism of Chitosan Coagulation Aid in Flocculation Treatment of Water Supply

2012 ◽  
Vol 433-440 ◽  
pp. 1857-1863
Author(s):  
Bing Tao Liu ◽  
Wei Wu ◽  
Hai Yang Cong
Keyword(s):  
Molecular Weight ◽  
Image Analysis ◽  
Fractal Dimension ◽  
Electron Microscope ◽  
Zeta Potential ◽  
Ph Value ◽  
Yellow River ◽  
Image Analysis System ◽  
Raw Water ◽  
Analysis System

The aim of this work is to remove residual turbidity and index of Potassium permanganate of the drinking water by PAC/Chitosan coagulation treatment. The experiments were performd the efficiency of coagulation by PAC/Chitosan at different chitosan dosages , molecular weight and pH value. Zeta potential instrument and Nikon electron microscope were used to test Zeta potential and observe flocs morphology. It turn out that Chitosan enhance the flocculation treatment of the surface water of raw water of Yellow River by polymeric aluminum chloride (PAC)when PAC dosage is 35 mg•l-1 and Chitosan is 0.15 mg•l-1 and infer coagulation aid mechanism was interpartical bridging rather than the electrical neutralization. Microscope and image analysis system of flocs morphology show that fractal dimension of morphology of PAC and PAC/Chitosan were 1.294,1.385, respectively.

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