Progress in parallel-detection electron energy loss spectroscopy

1988 ◽  
Vol 46 ◽  
pp. 660-661
Author(s):  
Ondrej L. Krivanek
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Dynamic Range ◽  
Detection Efficiency ◽  
Acquisition Time ◽  
Electron Spectrometer ◽  
Parallel Detection ◽  
Gain Variation ◽  
Electron Energy Loss ◽  
Spectral Intensities

Parallel-detection electron energy loss spectrometers improve the detection efficiency by several hundred times compared to the traditional serial-detection spectrometers, but they have their own set of difficulties, such as the limited dynamic range of solid state detectors, the possibility of stray reflections of the intense zero loss beam giving rise to spurious background, and channel-to-channel gain variation. Fortunately, none of these difficulties is turning out to be insoluble. Here we report on improvements of the Gatan 666 parallel detection electron spectrometer in the areas of increasing the dynamic range of the detector, and in eliminating stray reflections.The increase in the dynamic range of the detector was needed especially for low energy losses (high spectral intensities), which usually saturated the detector even at the minimum acquisition time of 12 msecs. Accordingly, we have developed an electron attenuator which uses a magnetic dipole to sweep the spectrum across the detector perpendicular to the dispersion direction (Fig. 1).

Parallel Detection of Electron Energy Loss Spectra in Direct Mode

1990 ◽  
Vol 48 (2) ◽  
pp. 82-83
Author(s):  
Eckhard Quandt ◽  
Stephan laBarré ◽  
Andreas Hartmann ◽  
Heinz Niedrig
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Energy Resolution ◽  
Large Angle ◽  
Maximum Energy ◽  
Semiconductor Detectors ◽  
Parallel Detection ◽  
Photodiode Arrays ◽  
Electron Energy Loss ◽  
Electron Energy Loss Spectra

Due to the development of semiconductor detectors with high spatial resolution -- e.g. charge coupled devices (CCDs) or photodiode arrays (PDAs) -- the parallel detection of electron energy loss spectra (EELS) has become an important alternative to serial registration. Using parallel detection for recording of energy spectroscopic large angle convergent beam patterns (LACBPs) special selected scattering vectors and small detection apertures lead to very low intensities. Therefore the very sensitive direct irradiation of a cooled linear PDA instead of the common combination of scintillator, fibre optic, and semiconductor has been investigated. In order to obtain a sufficient energy resolution the spectra are optionally magnified by a quadrupole-lens system.The detector used is a Hamamatsu S2304-512Q linear PDA with 512 diodes and removed quartz-glas window. The sensor size is 13 μm ∗ 2.5 mm with an element spacing of 25 μm. Along with the dispersion of 3.5 μm/eV at 40 keV the maximum energy resolution is limited to about 7 eV, so that a magnification system should be attached for experiments requiring a better resolution.

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.

Parallel electron energy-loss spectroscopy free from gain variation

1999 ◽  
Vol 76 (4) ◽  
pp. 221-231 ◽  
Author(s):  
J.L. Feng ◽  
R. Ho ◽  
Z. Shao ◽  
A.P. Somlyo
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Electron Energy Loss Spectroscopy ◽  
Gain Variation ◽  
Electron Energy Loss

Application of electron energy loss spectroscopy to microanalysis of irradiated stainless steels

1991 ◽  
Vol 49 ◽  
pp. 732-733
Author(s):  
E. A. Kenik ◽  
J. Bentley ◽  
N. D. Evans
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Stainless Steels ◽  
Electron Energy Loss Spectroscopy ◽  
Analytical Electron Microscopy ◽  
Radioactive Decay ◽  
Acquisition Time ◽  
Detector Performance ◽  
Radiation Induced ◽  
Electron Energy Loss

Energy dispersive X-ray spectroscopy (EDXS) has limited application to microanalysis of radioactive materials because of degraded detector performance and the “intrinsic” spectrum associated with the radioactive decay. Electron energy loss spectroscopy (EELS) is not affected by specimen radioactivity and also offers the possibility of improved spatial resolution. Measurements of radiation-induced segregation (RIS) in irradiated stainless steels have been made by both techniques. Analytical electron microscopy was performed at 100 kV in a Philips EM400T/FEG, equipped with an EDAX 9100/70 EDXS system and a Gatan 666 parallel detection EELS (PEELS). Microanalysis was performed in the STEM mode (<2-nm-diam probe with >0.5 nA) with the same acquisition time (50 s) used for both techniques.Initial measurements were performed on an ion-irradiated modified type 316 stainless steel (designated LS1A), which had moderate-width (∼20 nm) RIS profiles at grain boundaries. Profiles measured by EDXS and PEELS match well and show chromium depletion and nickel enrichment (Fig. 1).

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.

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