The Resolution and Contrast in Biological Sections Determined by Inelastic and Elastic Scattering

1973 ◽  
Vol 31 ◽  
pp. 224-225
Author(s):  
D. L. Misell
Keyword(s):  
Electron Microscopy ◽  
Adverse Effect ◽  
Elastic Scattering ◽  
Inelastic Scattering ◽  
Amorphous Carbon ◽  
Polymeric Materials ◽  
Chromatic Aberration ◽  
Image Resolution ◽  
Quantitative Estimates ◽  
Elastic Ratio

In the electron microscopy of biological sections the adverse effect of chromatic aberration on image resolution is well known. In this paper calculations are presented for the inelastic and elastic image intensities using a wave-optical formulation. Quantitative estimates of the deterioration in image resolution as a result of chromatic aberration are presented as an alternative to geometric calculations. The predominance of inelastic scattering in the unstained biological and polymeric materials is shown by the inelastic to elastic ratio, I/E, within an objective aperture of 0.005 rad for amorphous carbon of a thickness, t=50nm, typical of biological sections; E=200keV, I/E=16.

Low-voltage, high-resolution scanning electron microscopy of polymers

1987 ◽  
Vol 45 ◽  
pp. 466-467 ◽  
Author(s):  
S. J. Krause ◽  
W.W. Adams ◽  
S. Kumar ◽  
T. Reilly ◽  
T. Suziki
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Voltage ◽  
Chromatic Aberration ◽  
Image Resolution ◽  
Resolution Limit ◽  
Crossover Point ◽  
New Generation ◽  
Beam Damage ◽  
Scanning Electron

Scanning electron microscopy (SEM) of polymers at routine operating voltages of 15 to 25 keV can lead to beam damage and sample image distortion due to charging. Imaging polymer samples with low accelerating voltages (0.1 to 2.0 keV), at or near the “crossover point”, can reduce beam damage, eliminate charging, and improve contrast of surface detail. However, at low voltage, beam brightness is reduced and image resolution is degraded due to chromatic aberration. A new generation of instruments has improved brightness at low voltages, but a typical SEM with a tungsten hairpin filament will have a resolution limit of about 100nm at 1keV. Recently, a new field emission gun (FEG) SEM, the Hitachi S900, was introduced with a reported resolution of 0.8nm at 30keV and 5nm at 1keV. In this research we are reporting the results of imaging coated and uncoated polymer samples at accelerating voltages between 1keV and 30keV in a tungsten hairpin SEM and in the Hitachi S900 FEG SEM.

The use of an energy-filtering electron microscope to reduce chromatic aberration in images of thick biological specimens

1986 ◽  
Vol 44 ◽  
pp. 88-91
Author(s):  
L. D. Peachey ◽  
J. P. Heath ◽  
G. Lamprecht
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Beam ◽  
Cross Section ◽  
Electron Scattering ◽  
Chromatic Aberration ◽  
Image Resolution ◽  
Incident Electron Energy ◽  
Energy Filtering ◽  
Transmission Electron

Biological specimens of cells and tissues generally are considerably thicker than ideal for high resolution transmission electron microscopy. Actual image resolution achieved is limited by chromatic aberration in the image forming electron lenses combined with significant energy loss in the electron beam due to inelastic scattering in the specimen. Increased accelerating voltages (HVEM, IVEM) have been used to reduce the adverse effects of chromatic aberration by decreasing the electron scattering cross-section of the elements in the specimen and by increasing the incident electron energy.

Zero-Loss Energy Filtered REM and RHEED Observations on Rutile (110) Surface

1993 ◽  
Vol 51 ◽  
pp. 968-969
Author(s):  
L. Wang ◽  
J. Liu ◽  
J. M. Cowley
Keyword(s):  
Inelastic Scattering ◽  
Phonon Scattering ◽  
Chromatic Aberration ◽  
Electron Excitation ◽  
High Energy ◽  
Image Resolution ◽  
Surface Reflection ◽  
Energy Filtering ◽  
Reflection Electron Microscopy ◽  
Scattering Contribution

In reflection electron microscopy (REM), the surface reflection electrons undergo both elastic and inelastic scattering within a crystal. The dominant inelastic processes are phonon scattering, valence electron excitation, bulk and surface plasmon excitation and combinations of these processes. Multiple inelastic scattering processes are also probable as the mean traveling distance of surface reflection electrons is about 10 to 100 nm. In reflection high energy electron diffraction pattern (RHEED), 50% to 90% of the electrons contributing to surface reflection spots used for imaging have suffered energy loss of more than 10 eV, thus the main limitation on REM image resolution is due to the chromatic aberration effects given by the energy spread from inelastic scattering. An energy filter fitted inside a TEM microscope can remove most of the inelastic scattering contribution and so improve the contrast and resolution. Oxygen-annealed rutile (001), (100) and (110) surfaces were previously studied by REM and RHEED techniques without energy filtering.

A Study of Contrast For Biological Electron Microscopy

1973 ◽  
Vol 31 ◽  
pp. 256-257
Author(s):  
C. S. Chen
Keyword(s):  
Electron Microscopy ◽  
Elastic Scattering ◽  
Inelastic Scattering ◽  
Quantitative Study ◽  
Carbon Films ◽  
Experimental Measurements ◽  
Theoretical Predictions ◽  
Scattering Phase

The lack of contrast in the images of unstained and hydrated biological specimens is a serious limitation. Therefore, a quantitative study of contrast for various image modes has been undertaken. However, rather than perform time consuming experiments directly on the microscope, I have chosen to predict the contrast theoretically using a smaller number of experimental measurements to test the accuracy of the theoretical predictions.Fig. 1 shows the scattering distribution of carbon films at 100kV, and indicates that,at a given carbon thickness, the inelastic scattering passed by the aperture is almost ten times the elastic scattering. Thus, the image formed is incoherent, and highly chromatically aberrant. Due to the small elastic scattering, phase effects are expected to be small.

Applications of virtual objective aperture in TEM

1993 ◽  
Vol 51 ◽  
pp. 634-635
Author(s):  
G.Y. Fan ◽  
T. Deerinck ◽  
C.C. Ahn ◽  
J. Price ◽  
S.J. Young ◽  
...  
Keyword(s):  
Energy Loss ◽  
Inelastic Scattering ◽  
Focal Plane ◽  
Chromatic Aberration ◽  
Spinal Ganglion ◽  
Image Resolution ◽  
Objective Lens ◽  
Inelastic Contribution ◽  
Imaging Mode ◽  
Image Blur

In a special imaging mode (B mode) available on a customized JEM-4000EX microscope, the objective mini lens (OM) is strongly excited so that the back focal plane of the objective lens (OL) is imaged onto the plane of the selected-area aperture (SA), Fig. 1, with a magnification of 3.2x. Thus the S A functions as a virtual objective aperture, the applications of which are summarized below.1. Improving contrast in imaging thick sections of biological specimens.The increased inelastic scattering in thick specimens results in image blur due to chromatic aberration present in the magnetic lenses. Such blur degrades image resolution and contrast. The energy loss spectrum in Fig. 2 (curve 1), from a 1 μm section of frog spinal ganglion, suggests that the inelastic contribution to images of this type of specimen is substantial. The use of an objective aperture (OA) can reduce some of the unwanted contributions (curve 2), but the SA in B mode is much more effective, as suggested by Fig. 1 and demonstrated by curved 3.

Energy-filtered imaging in biological intermediate voltage TEM

1992 ◽  
Vol 50 (2) ◽  
pp. 1570-1571
Author(s):  
A.J. Gubbens ◽  
O.L. Krivanek
Keyword(s):  
Spatial Distribution ◽  
Elastic Scattering ◽  
Energy Loss ◽  
Inelastic Scattering ◽  
Chromatic Aberration ◽  
Biological Information ◽  
Energy Losses ◽  
Objective Lens ◽  
Characteristic Energy ◽  
Energy Filtering

In biological specimens of 150 nm and greater, inelastic scattering typically surpasses elastic scattering in magnitude. Because of the chromatic aberration of the objective lens of a TEM, the inelastically scattered electrons are focused differently, resulting in a loss of contrast in an ordinary TEM. With energy filtering, however, the inelastically scattered electrons can be prevented from contributing to the image, resulting in substantial recovery of contrast. In very thick specimens (1-5 μm), an energy filter can be used to select electrons of a particular energy loss, and an image with usable contrast can be formed. Further, by imaging only with electrons that have experienced characteristic energy losses, information can be obtained about the spatial distribution of various elements in the sample.Because of presently available instrumentation, energy filtered biological TEM has so far only been performed with TEMs of primary energies of 120 keV and lower. In this paper, we demonstrate the feasibilty of obtaining interesting biological information with a newly developed imaging filter designed for operation at up to 400 kV.

Imaging of the alpha-chain extensions of fibrinogen

1983 ◽  
Vol 41 ◽  
pp. 604-605
Author(s):  
Todd M. Price ◽  
M. L. Rudee
Keyword(s):  
Electron Microscopy ◽  
Amorphous Carbon ◽  
Microscopic Examination ◽  
Plasma Proteins ◽  
Polymeric Materials ◽  
Electron Microscopic Examination ◽  
Biological Materials ◽  
Mica Surface ◽  
Electron Microscopic ◽  
Alpha Chain

Amorphous carbon, as well as a few polymeric materials, are used routinely as substrates for the electron microscopic examination of macrorno1ecules. Replication of molecules from a cleaved mica surface is also used. The choice is ty pically made on the basis of convenience, and limited to commonly used materials.In the course of research on the interaction of plasma proteins with several non-biological materials we observed that the use of substrate materials that were not typical in electron microscopy produced images that revealed hitherto unobserved features of certain macromolecules. This paper will describe the techniques we have developed to image additional features of fibrinogen, give some additional results, and describe some experiments undertaken to elucidate the basis of the technique.

Elastic Scattering in Electron Microscopy

1973 ◽  
Vol 31 ◽  
pp. 252-253
Author(s):  
J. Langmore ◽  
M. Isaacson ◽  
J. Wall ◽  
A. V. Crewe
Keyword(s):  
Electron Microscopy ◽  
Elastic Scattering ◽  
Cross Section ◽  
Quantum Noise ◽  
Dark Field ◽  
Elastic Cross Section ◽  
Biological Molecules ◽  
Dark Field Microscopy ◽  
Field Systems ◽  
Effects Of Radiation

High resolution dark field microscopy is becoming an important tool for the investigation of unstained and specifically stained biological molecules. Of primary consideration to the microscopist is the interpretation of image Intensities and the effects of radiation damage to the specimen. Ignoring inelastic scattering, the image intensity is directly related to the collected elastic scattering cross section, σɳ, which is the product of the total elastic cross section, σ and the eficiency of the microscope system at imaging these electrons, η. The number of potentially bond damaging events resulting from the beam exposure required to reduce the effect of quantum noise in the image to a given level is proportional to 1/η. We wish to compare η in three dark field systems.

A New Image Processing Technique for STEM

1974 ◽  
Vol 32 ◽  
pp. 432-433
Author(s):  
Yasushi Kokubo ◽  
Hirotami Koike ◽  
Teruo Someya
Keyword(s):  
Electron Microscopy ◽  
Image Processing ◽  
Scanning Electron Microscopy ◽  
Elastic Scattering ◽  
Field Emission ◽  
Processing Technique ◽  
Image Processing Technique ◽  
Energy Analyzer ◽  
Scanning Microscope ◽  
Scanning Electron

One of the advantages of scanning electron microscopy is the capability for processing the image contrast, i.e., the image processing technique. Crewe et al were the first to apply this technique to a field emission scanning microscope and show images of individual atoms. They obtained a contrast which depended exclusively on the atomic numbers of specimen elements (Zcontrast), by displaying the images treated with the intensity ratio of elastically scattered to inelastically scattered electrons. The elastic scattering electrons were extracted by a solid detector and inelastic scattering electrons by an energy analyzer. We noted, however, that there is a possibility of the same contrast being obtained only by using an annular-type solid detector consisting of multiple concentric detector elements.

An Environmental Wet Cell For High Voltage Electron Microscopy

1973 ◽  
Vol 31 ◽  
pp. 18-19
Author(s):  
N.J. Tighe ◽  
H.M. Flower ◽  
P.R. Swann
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Image Quality ◽  
Inelastic Scattering ◽  
High Voltage ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
Environmental Cell ◽  
Water Saturated ◽  
High Temperature Gas

A differentially pumped environmental cell has been developed for use in the AEI EM7 million volt microscope. In the initial version the column of gas traversed by the beam was 5.5mm. This permited inclusion of a tilting hot stage in the cell for investigating high temperature gas-specimen reactions. In order to examine specimens in the wet state it was found that a pressure of approximately 400 torr of water saturated helium was needed around the specimen to prevent dehydration. Inelastic scattering by the water resulted in a sharp loss of image quality. Therefore a modified cell with an ‘airgap’ of only 1.5mm has been constructed. The shorter electron path through the gas permits examination of specimens at the necessary pressure of moist helium; the specimen can still be tilted about the side entry rod axis by ±7°C to obtain stereopairs.

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