Quantitative elemental concentrations by energy-filtered imaging

1995 ◽  
Vol 53 ◽  
pp. 268-269 ◽  
Author(s):  
J. Bentley ◽  
E. L. Hall ◽  
E. A. Kenik
Keyword(s):  
Core Loss ◽  
Specimen Thickness ◽  
Elemental Distribution ◽  
Edge Image ◽  
Distribution Maps ◽  
Diffraction Contrast ◽  
Transmission Electron ◽  
Half Angle ◽  
Electron Microscopes ◽  
Thickness Variations

There is widespread interest in elemental distribution maps produced from energy-filtered core-loss images obtained wim commercial imaging energy-filters and slow-scan charge-coupled device (CCD) cameras on transmission electron microscopes (TEMs). Earlier work on the feasibility of mapping solute segregation in stainless steels by energy-filtered imaging confirmed the utility of jump-ratio images (created by division of a post-edge image by a pre-edge one) for rapid assessments of elemental distributions. The effects of diffraction contrast and thickness variations are largely corrected for in such images. However, quantitative compositional information requires the use of net core-loss intensities following subtraction of an extrapolated background. Such core-loss intensities are influenced by diffraction contrast and thickness variations; corrections for these effects may be necessary for a quantitative interpretation. In the present work, energy-filtered images are treated similarly to quantitative electron energy-loss spectrometry (EELS) data. An image showing number of atoms per unit area, nx, is obtained by dividing the core-loss intensity image, Sx(Δ,β), by the low-loss image, J1(Δ,β), obtained with identical energy window Δ and collection half-angle β, and by the partial ionization cross-section, σx(Δ,β). Further normalization by specimen thickness, t, yields an image showing elemental concentration in atoms per unit volume:

Quantitative Measurements of Segregation In Co-Cr-X Magnetic Recording Media by Energy-Filtered Transmission Electron Microscopy

1998 ◽  
Vol 517 ◽  
Author(s):  
J. Bentley ◽  
J.E. Wittig ◽  
T.P. Nolan
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Magnetic Recording ◽  
Core Loss ◽  
Specimen Thickness ◽  
Recording Media ◽  
Magnetic Recording Media ◽  
Quantitative Measurements ◽  
Transmission Electron ◽  
Random Angle

AbstractReliable core-loss spectroscopic methods have been developed for mapping elemental segregation in Co-Cr-X magnetic recording media by energy-filtered transmission electron microscopy. Extraction of quantitative compositions at a spatial resolution approaching 1 nm involves sophisticated treatments for diffraction contrast, variations in specimen thickness, and closely-spaced oxygen K and chromium L23 ionization edges. These methods reveal that intergranular chromium levels are ∼25 at.% for random-angle boundaries and ∼15 at.% for 90° boundaries in films of Co84Cr12Ta4 d.c. magnetron sputtered at 250°C.

scholarly journals Chemical and Electron Beam Reduction of Vanadium Oxides Monitored by EELS and NEXAFS

2001 ◽  
Vol 7 (S2) ◽  
pp. 440-441
Author(s):  
D.S. Su ◽  
M. Hävecker ◽  
M. Willinger ◽  
R. Schlögl
Keyword(s):  
Core Loss ◽  
Vanadium Oxides ◽  
Catalytic Reactions ◽  
The Novel ◽  
Vanadyl Pyrophosphate ◽  
Transmission Electron ◽  
Environmental Tem ◽  
Defect Process ◽  
Electron Microscopes ◽  
Electron Energy Loss

The application of modern transmission electron microscopes (TEM) in catalytic research has accelerated the progress in understanding the mechanism of catalytic reactions. For instance, using environmental TEM, the novel glide shear defect process was revealed as an efficient mechanism for the release of the structural oxygen of vanadyl pyrophosphate in the n-butane oxidation [1]. On the other hand, electron energy-loss spectroscopy (EELS), which is nowadays commercially available on modern TEM, appears unknown in the catalytic community. in fact, core-loss EELS is a powerful tool to identify the chemical state of elements and to study the modification of this sate in various compounds.Fig.l shows EELS-spectra of various vanadium oxides in which the oxidation state of vanadium varies from 2+ (VO) to 5+ (V2O5). The first two features, marked as V L3 and V L2 edges, are attributed to the excitations from V 2p3/2and V 2p1/2core levels to the unoccupied V 3dstates, respectively.

scholarly journals A Convergence of Beauty and Utility

2014 ◽  
Vol 70 (a1) ◽  
pp. C41-C41
Author(s):  
John Steeds
Keyword(s):  
Electron Diffraction ◽  
Three Dimensional ◽  
Good Control ◽  
Critical Parameters ◽  
Specimen Thickness ◽  
Meaningful Information ◽  
Local Environments ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
Convergent Beam

The effective routine achievement of useful convergent beam electron diffraction (CBED) patterns was frustrated for many years until transmission electron microscopes (TEMs) were developed that overcame the practical difficulties. Because specimen thickness and orientation are two critical parameters in electron diffraction and are not under good control because of the difficulty of producing thin enough regions it was necessary to have TEMs capable of forming small focussed probes of less than 100nm diameter in local environments where the hydrocarbon level was sufficiently low to reduce carbon contamination to a reasonable level. Once these problems were overcome the importance of three-dimensional diffraction became apparent but to exploit this property it was necessary to develop TEMs with a large angular range in the diffraction plane. With appropriately designed instruments very beautiful CBED patterns could be obtained from crystalline samples and a variety of experimental techniques were exploited to extract meaningful information from them.

Spectroscopy and Imaging With Energy-Filtering Tems: Parameters That Matter

2000 ◽  
Vol 6 (S2) ◽  
pp. 158-159
Author(s):  
G. Kothleitner ◽  
H. A. Brink
Keyword(s):  
Imaging Techniques ◽  
Image Resolution ◽  
Elemental Distribution ◽  
Elemental Mapping ◽  
Core Excitation ◽  
Energy Filtering ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
Science Investigations ◽  
Shell Ionization

Spectroscopy and imaging techniques based on electron energy-losses (EELS), which are accessible through energy-filtering transmission electron microscopes (EFTEMs), have proven to be important tools in both materials and life science investigations.The two most widely used techniques on commercially available EFTEMs are elastic imaging and elemental mapping. Elastic imaging enhances image resolution and contrast by extracting the zero-loss signal and eliminating the inelastic background, whereas elemental mapping, which involves signals coming from element-specific inner-shell ionization edges, is employed to form two dimensional elemental distribution images. In both cases relatively large energy windows of a range of 10 to 30eVare typically used to form energy-filtered images with usually low to moderately high magnifications.There is however much more information available in an EELS spectrum, which is contained in the detailed fine structure within 0-20eV of a core excitation edge (ELNES) or in the very low energy-loss up to 5eV.

Plasmon-Ratio Imaging: A Technique for Enhancing the Contrast of Second Phases with Reduced Diffraction Contrast in TEM Micrographs

2004 ◽  
Vol 10 (4) ◽  
pp. 435-441 ◽  
Author(s):  
Graham J.C. Carpenter
Keyword(s):  
Imaging System ◽  
Core Loss ◽  
Low Loss ◽  
Crystalline Materials ◽  
Diffraction Contrast ◽  
Transmission Electron ◽  
Ratio Image ◽  
Ratio Imaging ◽  
Second Phases ◽  
Diffraction Effects

A technique is proposed for reducing unwanted diffraction contrast when imaging second phases in crystalline materials using transmission electron microscopy. With the suggested name of plasmon-ratio imaging, the technique uses an energy-filtered imaging system to record and determine a ratio for two images taken at energies in the low loss region. Unlike core-loss imaging, the use of very thin specimens is not required. It is concluded that it is often possible to create a ratio image in which the contrast is dominated by energy loss, that is, chemical differences, rather than by diffraction effects.

Energy-Filtered Electron Microscopy (EFEM) of Frozen Hydrated Biological Specimens

1990 ◽  
Vol 48 (1) ◽  
pp. 274-275
Author(s):  
Wolfgang Probst ◽  
Erhard Zellmann ◽  
Richard Bauer
Keyword(s):  
Core Loss ◽  
Low Loss ◽  
Transmission Electron ◽  
Freeze Dried ◽  
Before And After ◽  
Electron Microscopes ◽  
Blurred Images ◽  
Physical Reasons ◽  
Loss Range ◽  
Great Stride

The preparation of hydrated biological specimens for the use in a TEM has made a great stride foreward due to the work of Dubochet et al. on vitrification and Muller et al. on high pressure freezing. Transfer units and cryo stages for the microscopes allow imaging of specimens in the 100K range. Due to simple physical reasons, however, contrast of such kinds of specimen is still a problemm in conventional transmission electron microscopes (CTEM). Solutions as they are provided by an EFEM will be shown and explained in the following.Ice is the main constituent of frozen hydrated specimens. The large ratio of inelastic-to-elastic total cross section of 4.0 in case of ice which is even more than that for carbon results in an unavoidable high amount of inelastically scattered electrons. Blurred images and lacking contrast are due to that fact. The EEL spectra from a frozen hydrated section of biological material before and after freeze drying in the microscope document this fact. (Figure 1). Increased scattering probability and thickness contribute to the inelastic loss. In Figure 2 the EEL spectrum from a thin pure ice layer without any support is compared to the spectrum from thin freeze dried cryo section on a thin support. In case of ice the maximum of the low loss range is clearly shifted towards zero loss, mainly due to oxygen low loss and plasmon and to hydrogen core loss. Thus for the images shown in the following Figures a narrow energy window of 10 eV is used really to cut off all the inelastically scattered electrons.

Two- or three-way observations of the identical cell elements within the same sections by LM, TEM and/or SEM

1978 ◽  
Vol 36 (2) ◽  
pp. 82-83 ◽  
Author(s):  
Nakazo Watari ◽  
Yasuaki Hotta ◽  
Yoshio Mabuchi
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Fine Structure ◽  
Light Microscopy ◽  
Thin Sections ◽  
Transmission Electron ◽  
Identical Cell ◽  
Electron Microscopes ◽  
Scanning Electron

It is very useful if we can observe the identical cell elements within the same sections by light microscopy (LM), transmission electron microscopy (TEM) and/or scanning electron microscopy (SEM) sequentially, because, the cell fine structure can not be indicated by LM, while the color is; on the other hand, the cell fine structure can be very easily observed by EM, although its color properties may not. However, there is one problem in that LM requires thick sections of over 1 μm, while EM needs very thin sections of under 100 nm. Recently, we have developed a new method to observe the same cell elements within the same plastic sections using both light and transmission (conventional or high-voltage) electron microscopes.In this paper, we have developed two new observation methods for the identical cell elements within the same sections, both plastic-embedded and paraffin-embedded, using light microscopy, transmission electron microscopy and/or scanning electron microscopy (Fig. 1).

Resolution Attainable With the Present Day STEM

1973 ◽  
Vol 31 ◽  
pp. 230-231 ◽  
Author(s):  
J. S. Wall ◽  
J. P. Langmore ◽  
H. Isaacson ◽  
A. V. Crewe
Keyword(s):  
Spherical Aberration ◽  
Focal Length ◽  
Incident Beam ◽  
Scanning Transmission Electron Microscope ◽  
Aperture Size ◽  
Magnetic Lens ◽  
Peak Intensity ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Half Angle

The scanning transmission electron microscope (STEM) constructed by the authors employs a field emission gun and a 1.15 mm focal length magnetic lens to produce a probe on the specimen. The aperture size is chosen to allow one wavelength of spherical aberration at the edge of the objective aperture. Under these conditions the profile of the focused spot is expected to be similar to an Airy intensity distribution with the first zero at the same point but with a peak intensity 80 per cent of that which would be obtained If the lens had no aberration. This condition is attained when the half angle that the incident beam subtends at the specimen, 𝛂 = (4𝛌/Cs)¼

Removing Substrate Background in TEM Microanalysis

1974 ◽  
Vol 32 ◽  
pp. 568-569
Author(s):  
John C. Russ ◽  
Nicholas C. Barbi
Keyword(s):  
Electrical Conductivity ◽  
Rapid Growth ◽  
Organic Film ◽  
Absolute Concentration ◽  
Background Signal ◽  
X Ray ◽  
Elemental Concentrations ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
The Continuum

The rapid growth of interest in attaching energy-dispersive x-ray analysis systems to transmission electron microscopes has centered largely on microanalysis of biological specimens. These are frequently either embedded in plastic or supported by an organic film, which is of great importance as regards stability under the beam since it provides thermal and electrical conductivity from the specimen to the grid.Unfortunately, the supporting medium also produces continuum x-radiation or Bremsstrahlung, which is added to the x-ray spectrum from the sample. It is not difficult to separate the characteristic peaks from the elements in the specimen from the total continuum background, but sometimes it is also necessary to separate the continuum due to the sample from that due to the support. For instance, it is possible to compute relative elemental concentrations in the sample, without standards, based on the relative net characteristic elemental intensities without regard to background; but to calculate absolute concentration, it is necessary to use the background signal itself as a measure of the total excited specimen mass.

Resolution of a Transmitted Electron Image Formed by A Scanning Electron Microscope

1970 ◽  
Vol 28 ◽  
pp. 386-387
Author(s):  
S. Takashima ◽  
H. Hashimoto ◽  
S. Kimoto
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Chromatic Aberration ◽  
Objective Lens ◽  
Specimen Thickness ◽  
Probe Diameter ◽  
Transmission Electron ◽  
Electron Image ◽  
Conventional Transmission Electron Microscope ◽  
Scanning Electron

The resolution of a conventional transmission electron microscope (TEM) deteriorates as the specimen thickness increases, because chromatic aberration of the objective lens is caused by the energy loss of electrons). In the case of a scanning electron microscope (SEM), chromatic aberration does not exist as the restrictive factor for the resolution of the transmitted electron image, for the SEM has no imageforming lens. It is not sure, however, that the equal resolution to the probe diameter can be obtained in the case of a thick specimen. To study the relation between the specimen thickness and the resolution of the trans-mitted electron image obtained by the SEM, the following experiment was carried out.

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