Electron spectroscopic imaging of thick crystalline specimens

1989 ◽  
Vol 47 ◽  
pp. 412-413
Author(s):  
L. Reimer ◽  
R. Rennekamp ◽  
A. Bakenfelder
Keyword(s):  
Angular Distribution ◽  
Lattice Defect ◽  
Spectroscopic Imaging ◽  
Chromatic Aberration ◽  
List Type ◽  
Electron Spectroscopic Imaging ◽  
Field Mode ◽  
Energy Filtering ◽  
Plasmon Loss ◽  
Electron Energy Loss

Electron spectroscopic imaging (ESI) by an energy-filtering electron microscope (EFEM, Zeiss EM902) shows the following advantages when compared with the unfiltered bright-field mode:1.The zero-loss image does not contain the contribution of inelastically scattered electrons. Though plasmon scattering shows a conversation of Bragg contrast - edge and bent contours and lattice defect images -, the angular distribution of inelastically scattered electrons results in a broader spectrum of excitation errors and a blurring of Bragg contrast.2.The zero-loss image avoids the chromatic aberration of inelastically scattered electrons for medium specimen thicknesses and can be applied so long as the intensity of the zero-loss peak in the electron energy-loss spectrum (EELS) is high enough for an exposure in a reasonable time (<100 s).3.Thick specimens with negligible zero-loss intensity can be imaged with an energy window at the highest multiple plasmon loss of the Poisson distribution or at the most probable energy of a Landau distribution. The angular distribution of electrons with these energy losses is so broad that the Bragg contrast is blurred, and the contrast is only caused by anomalous absorption effects similar to multi-beam images in the STEM mode when using a large probe aperture.

Electron Spectroscopic Imaging and Diffraction in TEM

1990 ◽  
Vol 48 (2) ◽  
pp. 66-67
Author(s):  
L. Reimer
Keyword(s):  
Electron Microscopy ◽  
Phase Contrast ◽  
Spectroscopic Imaging ◽  
Chromatic Aberration ◽  
Elemental Mapping ◽  
Electron Spectroscopic Imaging ◽  
Energy Filtering ◽  
Structure Sensitive ◽  
The Difference ◽  
Electron Energy Loss

Energy-filtering electron microscopy at 80 keV (ZEISS EM902) offers the combination of electron spectroscopic imaging (ESI) and diffraction (ESD) and electron energy-loss spectroscopy (EELS). For details the reader is referred to a description of the different modes, applications of ESI to biological and crystalline specimens and of ESD. The very important mode of elemental mapping with the difference of ESI below and beyond an edge will not be discussed in this review.The ESI mode increases scattering contrast of stained and unstained biological sections and avoids chromatic aberration by zero-loss filtering. Filtering at ΔE=250 eV below the C edge increases the (structure-sensitive) contrast by non-carbon atoms of unstained sections (Fig.1). Phase contrast is also increased but inelastically scattered electrons show a faint phase contrast which can be explained by treating partial inelastic waves with different q as incoherent. Bragg contrast of crystalline specimens is enhanced due to avoiding chromatic aberration and a blurring by the spectrum of excitation errors of inelastically scattered electrons (Fig.2).

Dark-field electron spectroscopic imaging of aged microstructures in an aluminium lithium base alloy

1990 ◽  
Vol 48 (4) ◽  
pp. 444-445
Author(s):  
I. G. Solórzano ◽  
W. Probst
Keyword(s):  
Base Alloy ◽  
Spectroscopic Imaging ◽  
Chromatic Aberration ◽  
Dark Field ◽  
Objective Lens ◽  
Electron Spectroscopic Imaging ◽  
Bright Field ◽  
Field Mode ◽  
Dark Field Electron ◽  
Very High

The examination of microstructures make very high demands on the imaging quality and, therefore, on the instrumentation. In Al-Li base alloys it is of great interest to determine parameters such as size, distribution, morphology and coherency of precipitate phases as they dictate their mechanical behavior. In order to reveal morphological features with high quality the electron spectroscopic imaging (ESI) in dark field mode has shown to be quite a powerful technique.The ESI technique in the TEM is based on the possibility that accelerated electrons can be elastic and inelastically scattered by the sample atoms, as recently reviewed. The electron distribution in the transmitted and diffracted beams through a crystalline sample is such that both energy loss and elastic electrons will enter a typical objective aperture and thus contribute to both bright field and dark field images. The effect of the polyenergetic electrons is that the image is affected by chromatic aberration of the objective lens. In CTEM’s this effect is enhanced the lower the accelerating voltage and the thicker the sample.

Electron spectroscopic imaging and diffraction: applications II materials science

1992 ◽  
Vol 50 (2) ◽  
pp. 1198-1199
Author(s):  
J. Mayer
Keyword(s):  
Electron Microscopy ◽  
Energy Loss ◽  
Materials Science ◽  
Spectroscopic Imaging ◽  
Electron Spectroscopic Imaging ◽  
Imaging Spectrometer ◽  
Transmission Electron ◽  
Diffraction Patterns ◽  
Electron Spectroscopic Diffraction ◽  
Electron Energy Loss

With imaging energy filters becoming commercially available in transmission electron microscopy many of the limitations of conventional TEM instruments can be overcome. Energy filtered images of diffraction patterns can now be recorded without scanning using efficient parallel (2-dimensional detection. We have evaluated a prototype of the Zeiss EM 912 Omega, the first commercially available electron microscope with integrated imaging Omega energy filter. Combining the capabilities of the imaging spectrometer with the principal operation modes of a TEM gives access to many new qualitative and quantitative techniques in electron microscopy. The basis for all of them is that the filter selecte electrons within a certain energy loss range ΔE1 <ΔE < ΔE2 and images their contribution to an image (electron spectroscopic imaging, ESI) or a diffraction pattern (electron spectroscopic diffraction, ESD) In many applications the filter is only used to remove the inelastically scattered electrons (elastic or zero loss filtering). Furthermore, the electron energy loss spectrum can be magnified and recorded with serial or parallel detection.

Resolution and contrast enhancement on biological specimens by means of electron spectroscopic imaging (ESI)

1986 ◽  
Vol 44 ◽  
pp. 68-69
Author(s):  
U. B. Hezel ◽  
R. Bauer ◽  
E. Zellmann ◽  
W. I. Miller
Keyword(s):  
Heavy Metals ◽  
Heavy Metal ◽  
Electron Beam ◽  
Contrast Enhancement ◽  
Electron Scattering ◽  
Biological Material ◽  
Spectroscopic Imaging ◽  
Chromatic Aberration ◽  
Electron Spectroscopic Imaging ◽  
Chromatic Aberrations

The main elemental constituents of biological material - C,H,N,O - are the same elements found in typical embedding materials. Because of this the contrast of unstained biological material is very poor. Additionally, electron scattering by low Z atoms is mainly inelastic resulting in unsharp images from the concomitant chromatic aberration.These effects have been delt with by employing stains of such heavy metals as Os, U, or Pb. These stains are for the most part located at the biological structures themselves and primarily scatter the electron beam elastically. Thus with ultra-thin (<80nm) heavy metal stained sections of biological material the contrast in the CTEM is very good and chromatic aberrations are negligable.

Energy-filtering Transmission Electron Microscopy in materials and life science

1994 ◽  
Vol 52 ◽  
pp. 936-937
Author(s):  
L. Reimer
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Energy Loss ◽  
Electron Energy ◽  
Analytical Electron Microscopy ◽  
Edge Structure ◽  
Energy Filtering ◽  
Transmission Electron ◽  
Plasmon Loss ◽  
Electron Energy Loss

Energy-filtering transmission electron microscopy can be realized by an imaging filter lens in thecolumn of a TEM, a post-column electron energy-loss spectrometer or a dedicated STEM. This offers new possibilities in analytical electron microscopy by combining the operation modes of electron-spectroscopic imaging (ESI), electron-spectroscopic diffraction (ESD) and the record of an electron energy-loss spectrum (EELS).ESI can be used in the zero-loss mode to remove all inelastically scattered electrons. Thicker amorphous and crystalline specimens can be observed without chromatic aberration and with a transmissionof 10−3 up to 80(110) and 150(200) μg/cm2 at 80(120) keV, respectively. This results in a condiserable increase of scattering, phase and Bragg contrast, especially for low Z material because the ratio of inelastic-to-elastic cross section increases as 20/Z with decreasing atomic number. In future energy-filtered high-resolution crystal-lattice images will offer us a better comparison with dynamical simulations. Plasmon loss filtering can be applied for a better separation of phases (e.g. precipitates in a matrix), which differ in their plasmon loss by about 1 eV. Owing to intersections of the energy loss spectra, different parts of a specimen can change their contrast when tuning the selected energy window. Structures containing non carbon atoms will beconsiderably increased in a bright field like contrast relative to the carboneous matrix just below the carbon K edge (structure—sensitive imaging).

Sign in / Sign up

Export Citation Format

Share Document