Advances in Parallel-Detection EELS

1990 ◽  
Vol 48 (2) ◽  
pp. 76-77
Author(s):  
O.L. Krivanek ◽  
N. Dellby ◽  
A.J. Gubbens ◽  
M.K. Kundmann ◽  
M.L. Leber ◽  
...  
Keyword(s):  
Energy Resolution ◽  
Single Atom ◽  
Statistical Fluctuation ◽  
Parallel Detection ◽  
Routine Basis ◽  
Atom Level ◽  
New Applications ◽  
User Friendly ◽  
Electron Energy Loss ◽  
Better Than

Parallel-detection electron energy-loss spectrometers (PEELS) now routinely provide spectra in which the main source of noise is the statistical fluctuation in the number of arriving electrons (i.e., they have DQE > 0.5), achieve an energy resolution which is more than 90% limited by the electron microscope gun, and are fairly easy to operate. They have pushed the minimum detectable mass (MDM) obtainable by PEELS close to the single atom level, and have improved the minimum detectable mass fraction (MDF) so that it is now comparable or better than MDF detectable by EDXS even for elements as heavy as Fe. The attainable energy resolution is now 0.3-0.5 eV on a routine basis when the spectrometer is mounted on a cold field-emission gun (S)TEM operating at 100 kV (Fig. 1). This impressive progress has opened up an important question: where next?Our answer is three-fold: towards greater integration of EELS with other techniques of electron microscopy, towards new applications of the technique, and towards more quantitative and yet more user-friendly analysis of the results.

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.

A New High Performance Electron Energy Loss Spectrometer for use with Monochromated Microscopes

2001 ◽  
Vol 7 (S2) ◽  
pp. 908-909
Author(s):  
H.A. Brink ◽  
M. Barfels ◽  
B. Edwards ◽  
P. Burgner
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Energy Resolution ◽  
Optical Design ◽  
Electron Source ◽  
High Voltage Power Supply ◽  
Electron Energy Loss Spectrometer ◽  
Electron Microscopes ◽  
Electron Energy Loss ◽  
Better Than

A new type of electron energy loss spectrometer for use with monochromated microscopes is presented. The energy resolution of the spectrometer is better than 0.100 eV. A completely new electron optical design with a number of extra optical elements and advanced tuning software makes it possible to correct spectrum aberrations to 4th order, which increases sensitivity and collection angles. New high-stability electronics make it possible to maintain energy resolution over a period of several minutes in a practical laboratory environment.The energy resolution of Transmission Electron Microscopes (TEMs) equipped with electron energy loss spectrometers is determined by a combination of the energy spread of the electron source, the stability of the microscope’s high voltage power supply, and the energy resolution of the spectrometer. Commercial microscopes usually employ electron sources with an energy distributions of around 0.5 eV or more (FWHM), limiting the energy ultimate energy resolution that can be achieved. Recently FEI constructed a special 200 kV TEM with a built-in monochromator which makes it possible to monochromize the electron source to better than 0.100 eV. A prototype of the presented spectrometer has been installed on this microscope.

Fine structure of inner shell electron energy loss edges of manganese oxides

1989 ◽  
Vol 47 ◽  
pp. 392-393
Author(s):  
James H. Paterson ◽  
Ondrej L. Krivanek ◽  
Helmut R. Poppa
Keyword(s):  
Fine Structure ◽  
Energy Loss ◽  
Electron Energy ◽  
Energy Resolution ◽  
Manganese Oxides ◽  
Scanning Transmission Electron Microscope ◽  
Parallel Detection ◽  
Scanning Transmission ◽  
And Performance ◽  
Electron Energy Loss

Rask et al. showed that electron energy loss spectroscopy (EELS) may be used to identify oxidation states of polyvalent cations. For the case of manganese, differences in oxidation state are reflected in the shape and position of the edges in the EELS spectrum due to inelastic scattering of incident electrons by the inner shells of manganese and oxygen. We have used a scanning transmission electron microscope (STEM) with a cold field emission gun (FEG) and a parallel-detection EELS system to re-investigate the variations in energy loss fine structure of EELS spectra of various manganese oxides with a significantly improved energy resolution.Spectra were recorded at 100 kV using a VG HB501 STEM with post-specimen lenses, and a Galan Model 666 parallel-detection electron energy loss spectrometer. The operation and performance of this system are discussed elsewhere in these proceedings. For the inner shell edges, the energy dispersion produced by the spectrometer was set to give 0.05 eV per channel. so that a complete spectrum of 1024 channels sampled a range of energy loss of 50 eV. The energy resolution, of the order of 0.4 eV, was therefore not limited by the spatial resolution of the photodiode array in the spectrometer. The oxygen K and manganese L2,3 edges were recorded separately.

Improved detection limits with parallel-detection EELS

1991 ◽  
Vol 49 ◽  
pp. 724-725
Author(s):  
O.L. Krivanek ◽  
M.K. Kundmann
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Cross Sections ◽  
Detection Limits ◽  
Single Atom ◽  
Probe Current ◽  
Parallel Detection ◽  
Microanalytical Technique ◽  
The Matrix ◽  
Electron Energy Loss

Parallel-detection electron energy-loss spectrometers (PEELS) have improved the detection limits of electron energy-loss spectroscopy (EELS) so much that established comparisons between EELS and energy-dispersive X-ray spectroscopy (EDXS) no longer apply. We have therefore decided to reinvestigate the comparative advantages of EELS as a microanalytical technique.Two types of detection limits are of interest: minimum detectable mass (MDM), and minimum detectable mass fraction (MMF). MDM has been improved by parallel-detection EELS so much that single atoms of elements with favorable cross-sections have become detectable. Since detecting a single atom requires a probe with at least 0.1 nA of current and a diameter of no more than 1 nm, this level of performance needs an electron microscope equipped with an efficient field-emission gun (FEG). On the other hand, because the ratio of the signal from a uniformly dispersed element to the signal from the matrix does not depend on the size of the probed area, MMF depends on the total available probe current rather than the probe current density. This means that MMF should be better for microscopes equipped with thermionic guns than for ones equipped with FEGs.

Stability of Fluorinated Organic Compounds as Measured by Parallel-Detection EELS

1990 ◽  
Vol 48 (2) ◽  
pp. 408-409
Author(s):  
B.J. Ciliax ◽  
K.L. Kirk ◽  
R.D. Leapman
Keyword(s):  
Energy Loss ◽  
Organic Compounds ◽  
Room Temperature ◽  
Cellular Level ◽  
Thin Layers ◽  
Air Drying ◽  
Parallel Detection ◽  
Electron Energy Loss ◽  
Beam Damage ◽  
Better Than

The use of fluorine-labelling to localize specific organic compounds at the sub-cellular level by means of electron energy loss spectroscopy (EELS) was suggested over ten years ago. Since then, however, there have been differing reports about the susceptibility of fluorinated compounds to fluorine loss in the electron beam; damage doses appear to range over several orders of magnitude. Recent advances in EELS, i.e. the availability of parallel detectors, have generated renewed interest in this labelling technique. We therefore have undertaken a more systematic study of radiation damage in a series of aromatic and aliphatic fluorinated compounds as a function of dose and temperature.Energy loss spectra were recorded using a VG Microscopes HB501 STEM equipped with a Gatan model 666 parallel-detection spectrometer. The vacuum at the specimen was better than 5×10−9 mbar and the specimen could be cooled from room temperature to 100 K. Samples were prepared by air drying thin layers of the compounds dissolved in appropriate solvents on to ˜10 nm carbon or aluminum evaporated films supported on 200 mesh copper grids.

Use of LaB6 for a High Quality, Small Energy Spread Beam in an Electron Velocity Spectrometer

1976 ◽  
Vol 34 ◽  
pp. 534-535 ◽  
Author(s):  
P. E. Batson ◽  
C. H. Chen ◽  
J. Silcox
Keyword(s):  
High Temperature ◽  
Energy Resolution ◽  
Electron Velocity ◽  
Electronic Excitations ◽  
Small Energy ◽  
Small Intensity ◽  
Good Energy ◽  
Spectrometer System ◽  
Electron Energy Loss ◽  
Very High

Electron energy loss experiments combined with microscopy have proven to be a valuable tool for the exploration of the structure of electronic excitations in materials. These types of excitations, however, are difficult to measure because of their small intensity. In a usual situation, the filament of the microscope is run at a very high temperature in order to present as much intensity as possible at the specimen. This results in a degradation of the ultimate energy resolution of the instrument due to thermal broadening of the electron beam.We report here observations and measurements on a new LaB filament in a microscope-velocity spectrometer system. We have found that, in general, we may retain a good energy resolution with intensities comparable to or greater than those available with the very high temperature tungsten filament. We have also explored the energy distribution of this filament.

Probing the Chemistry and Spectroscopy of Radiation-Sensitive Polymers by Parallel-Detection EELS

1990 ◽  
Vol 48 (2) ◽  
pp. 34-35
Author(s):  
E. G. Rightor ◽  
G. P. Young
Keyword(s):  
Electron Beam ◽  
Bisphenol A ◽  
Energy Loss ◽  
Parallel Detection ◽  
Commercial Grade ◽  
Incident Electron Beam ◽  
Ptfe Sample ◽  
Spectroscopic Information ◽  
Edge Features ◽  
Electron Energy Loss

Investigation of neat polymers by TEM is often thwarted by their sensitivity to the incident electron beam, which also limits the usefulness of chemical and spectroscopic information available by electron energy loss spectroscopy (EELS) for these materials. However, parallel-detection EELS systems allow reduced radiation damage, due to their far greater efficiency, thereby promoting their use to obtain this information for polymers. This is evident in qualitative identification of beam sensitive components in polymer blends and detailed investigations of near-edge features of homopolymers.Spectra were obtained for a poly(bisphenol-A carbonate) (BPAC) blend containing poly(tetrafluoroethylene) (PTFE) using a parallel-EELS and a serial-EELS (Gatan 666, 607) for comparison. A series of homopolymers was also examined using parallel-EELS on a JEOL 2000FX TEM employing a LaB6 filament at 100 kV. Pure homopolymers were obtained from Scientific Polymer Products. The PTFE sample was commercial grade. Polymers were microtomed on a Reichert-Jung Ultracut E and placed on holey carbon grids.

ELNES of Iron Compounds

1990 ◽  
Vol 48 (2) ◽  
pp. 28-29
Author(s):  
Hiroki Kurata ◽  
Kazuhiro Nagai ◽  
Seiji Isoda ◽  
Takashi Kobayashi
Keyword(s):  
Energy Loss ◽  
Metal Ions ◽  
Energy Resolution ◽  
Transition Metal Oxides ◽  
Local Symmetry ◽  
Iron Compounds ◽  
Fine Structures ◽  
Electron Energy Loss ◽  
Fe Ions ◽  
Electron Energy Loss Spectra

Electron energy loss spectra of transition metal oxides, which show various fine structures in inner shell edges, have been extensively studied. These structures and their positions are related to the oxidation state of metal ions. In this sence an influence of anions coordinated with the metal ions is very interesting. In the present work, we have investigated the energy loss near-edge structures (ELNES) of some iron compounds, i.e. oxides, chlorides, fluorides and potassium cyanides. In these compounds, Fe ions (Fe2+ or Fe3+) are octahedrally surrounded by six ligand anions and this means that the local symmetry around each iron is almost isotropic.EELS spectra were obtained using a JEM-2000FX with a Gatan Model-666 PEELS. The energy resolution was about leV which was mainly due to the energy spread of LaB6 -filament. The threshole energies of each edges were measured using a voltage scan module which was calibrated by setting the Ni L3 peak in NiO to an energy value of 853 eV.

pLoc_bal-mPlant: Predict Subcellular Localization of Plant Proteins by General PseAAC and Balancing Training Dataset

2019 ◽  
Vol 24 (34) ◽  
pp. 4013-4022 ◽  
Author(s):  
Xiang Cheng ◽  
Xuan Xiao ◽  
Kuo-Chen Chou
Keyword(s):  
Subcellular Localization ◽  
Basic Research ◽  
Training Dataset ◽  
Sequence Information ◽  
Plant Proteins ◽  
Protein Subcellular Localization ◽  
Computational Tools ◽  
Validation Tests ◽  
User Friendly ◽  
Better Than

Knowledge of protein subcellular localization is vitally important for both basic research and drug development. With the avalanche of protein sequences emerging in the post-genomic age, it is highly desired to develop computational tools for timely and effectively identifying their subcellular localization based on the sequence information alone. Recently, a predictor called “pLoc-mPlant” was developed for identifying the subcellular localization of plant proteins. Its performance is overwhelmingly better than that of the other predictors for the same purpose, particularly in dealing with multi-label systems in which some proteins, called “multiplex proteins”, may simultaneously occur in two or more subcellular locations. Although it is indeed a very powerful predictor, more efforts are definitely needed to further improve it. This is because pLoc-mPlant was trained by an extremely skewed dataset in which some subsets (i.e., the protein numbers for some subcellular locations) were more than 10 times larger than the others. Accordingly, it cannot avoid the biased consequence caused by such an uneven training dataset. To overcome such biased consequence, we have developed a new and bias-free predictor called pLoc_bal-mPlant by balancing the training dataset. Cross-validation tests on exactly the same experimentconfirmed dataset have indicated that the proposed new predictor is remarkably superior to pLoc-mPlant, the existing state-of-the-art predictor in identifying the subcellular localization of plant proteins. To maximize the convenience for the majority of experimental scientists, a user-friendly web-server for the new predictor has been established at http://www.jci-bioinfo.cn/pLoc_bal-mPlant/, by which users can easily get their desired results without the need to go through the detailed mathematics.

pLoc_bal-mEuk: Predict Subcellular Localization of Eukaryotic Proteins by General PseAAC and Quasi-balancing Training Dataset

2019 ◽  
Vol 15 (5) ◽  
pp. 472-485 ◽  
Author(s):  
Kuo-Chen Chou ◽  
Xiang Cheng ◽  
Xuan Xiao
Keyword(s):  
Drug Development ◽  
Subcellular Localization ◽  
Basic Research ◽  
The Other ◽  
Training Dataset ◽  
Sequence Information ◽  
Eukaryotic Proteins ◽  
Validation Tests ◽  
User Friendly ◽  
Better Than

<P>Background/Objective: Information of protein subcellular localization is crucially important for both basic research and drug development. With the explosive growth of protein sequences discovered in the post-genomic age, it is highly demanded to develop powerful bioinformatics tools for timely and effectively identifying their subcellular localization purely based on the sequence information alone. Recently, a predictor called “pLoc-mEuk” was developed for identifying the subcellular localization of eukaryotic proteins. Its performance is overwhelmingly better than that of the other predictors for the same purpose, particularly in dealing with multi-label systems where many proteins, called “multiplex proteins”, may simultaneously occur in two or more subcellular locations. Although it is indeed a very powerful predictor, more efforts are definitely needed to further improve it. This is because pLoc-mEuk was trained by an extremely skewed dataset where some subset was about 200 times the size of the other subsets. Accordingly, it cannot avoid the biased consequence caused by such an uneven training dataset. </P><P> Methods: To alleviate such bias, we have developed a new predictor called pLoc_bal-mEuk by quasi-balancing the training dataset. Cross-validation tests on exactly the same experimentconfirmed dataset have indicated that the proposed new predictor is remarkably superior to pLocmEuk, the existing state-of-the-art predictor in identifying the subcellular localization of eukaryotic proteins. It has not escaped our notice that the quasi-balancing treatment can also be used to deal with many other biological systems. </P><P> Results: To maximize the convenience for most experimental scientists, a user-friendly web-server for the new predictor has been established at http://www.jci-bioinfo.cn/pLoc_bal-mEuk/. </P><P> Conclusion: It is anticipated that the pLoc_bal-Euk predictor holds very high potential to become a useful high throughput tool in identifying the subcellular localization of eukaryotic proteins, particularly for finding multi-target drugs that is currently a very hot trend trend in drug development.</P>

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