Development of a conical anode Fe-gun for low voltage SEM

1988 ◽  
Vol 46 ◽  
pp. 978-979
Author(s):  
T. Miyokawa ◽  
S. Norioka ◽  
S. Goto
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Low Voltage ◽  
Irradiation Damage ◽  
Cold Cathode ◽  
Virtual Source ◽  
Source Position ◽  
Electrostatic Lens ◽  
Electrostatic Lenses ◽  
Wide Range

Field emission SEMs (FE-SEMs) are becoming popular due to their high resolution needs. In the field of semiconductor product, it is demanded to use the low accelerating voltage FE-SEM to avoid the electron irradiation damage and the electron charging up on samples. However the accelerating voltage of usual SEM with FE-gun is limited until 1 kV, which is not enough small for the present demands, because the virtual source goes far from the tip in lower accelerating voltages. This virtual source position depends on the shape of the electrostatic lens. So, we investigated several types of electrostatic lenses to be applicable to the lower accelerating voltage. In the result, it is found a field emission gun with a conical anode is effectively applied for a wide range of low accelerating voltages.A field emission gun usually consists of a field emission tip (cold cathode) and the Butler type electrostatic lens.

Three-fold astigmatism: An important TEM aberration

1993 ◽  
Vol 51 ◽  
pp. 972-973 ◽  
Author(s):  
O.L. Krivanek ◽  
M.L. Leber
Keyword(s):  
High Resolution ◽  
Spatial Frequency ◽  
Field Emission ◽  
Azimuthal Angle ◽  
Hollow Cone ◽  
Small Probe ◽  
Wide Range ◽  
High Resolution Images ◽  
Image Position

Three-fold astigmatism resembles regular astigmatism, but it has 3-fold rather than 2-fold symmetry. Its contribution to the aberration function χ(q) can be written as:where A3 is the coefficient of 3-fold astigmatism, λ is the electron wavelength, q is the spatial frequency, ϕ the azimuthal angle (ϕ = tan-1 (qy/qx)), and ϕ3 the direction of the astigmatism.Three-fold astigmatism is responsible for the “star of Mercedes” aberration figure that one obtains from intermediate lenses once their two-fold astigmatism has been corrected. Its effects have been observed when the beam is tilted in a hollow cone over a wide range of angles, and there is evidence for it in high resolution images of a small probe obtained in a field emission gun TEM/STEM instrument. It was also expected to be a major aberration in sextupole-based Cs correctors, and ways were being developed for dealing with it on Cs-corrected STEMs.

Field Emission Scanning Electron Microscopy Studies of Industrial Polymers - A Survey

1998 ◽  
Vol 4 (S2) ◽  
pp. 814-815
Author(s):  
E.F. Osten ◽  
M.S. Smith
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
High Resolution ◽  
Field Emission ◽  
Low Voltage ◽  
Structural Features ◽  
X Ray Diffraction ◽  
Styrene Acrylonitrile ◽  
Microscopy Techniques ◽  
Scanning Electron

We are using the term "Industrial Polymers" to refer to polymers [plastics] that are produced by the ton or (in the case of films) by the mile. For example, in descending order of world-wide use (tonnage), the top eight of these polymers are polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP), styrene polymers (including polystyrene - PS, and acrylonitrile-butadienestyrene/ styrene-acrylonitrile - ABS/SAN), polyesters (PETP), polyurethane (PU), phenolics and aminoplastics.Industrial polymers, which have been produced by the millions of tons for the last five decades and are of obvious social and economic importance, have been exhaustively characterized. Structural features which affect physical properties and indicate process variables have been studied by many techniques other than microscopy (x-ray diffraction, thermal analysis, rheology, chromatographies, etc.). Microscopy techniques for polymer characterization have been well documented. Our motivation to apply field emission (high resolution) scanning electron microscopy to the study of polymers is: (1) The application of low voltage, high resolution SEM to biological materials is well characterized.

Structural Evidence for Actin-like Filaments in Toxoplasma gondii Using High-Resolution Low-Voltage Field Emission Scanning Electron Microscopy

2003 ◽  
Vol 9 (4) ◽  
pp. 330-335 ◽  
Author(s):  
Heide Schatten ◽  
L. David Sibley ◽  
Hans Ris
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
High Resolution ◽  
Toxoplasma Gondii ◽  
Field Emission ◽  
Low Voltage ◽  
Protozoan Parasite ◽  
Cytoskeletal Network ◽  
Unicellular Organisms ◽  
Scanning Electron

The protozoan parasite Toxoplasma gondii is representative of a large group of parasites within the phylum Apicomplexa, which share a highly unusual motility system that is crucial for locomotion and active host cell invasion. Despite the importance of motility in the pathology of these unicellular organisms, the motor mechanisms for locomotion remain uncertain, largely because only limited data exist about composition and organization of the cytoskeleton. By using cytoskeleton stabilizing protocols on membrane-extracted parasites and novel imaging with high-resolution low-voltage field emission scanning electron microscopy (LVFESEM), we were able to visualize for the first time a network of actin-sized filaments just below the cell membrane. A complex cytoskeletal network remained after removing the actin-sized fibers with cytochalasin D, revealing longitudinally arranged, subpellicular microtubules and intermediate-sized fibers of 10 nm, which, in stereo images, are seen both above and below the microtubules. These approaches open new possibilities to characterize more fully the largely unexplored and unconventional cytoskeletal motility complex in apicomplexan parasites.

Image Formation With Upper and Lower Secondary Electron Detectors in the Low Voltage Field-Emission SEM

1998 ◽  
Vol 4 (S2) ◽  
pp. 260-261
Author(s):  
J. Liu
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Secondary Electron ◽  
Low Voltage ◽  
Incident Beam ◽  
Sample Surface ◽  
Backscattered Electrons ◽  
Sample Chamber ◽  
Scale Surface ◽  
Short Working

High-resolution secondary electron (SE) imaging was first demonstrated at 100 kV in the STEM a decade ago. High-resolution SE imaging is now routinely obtainable in field-emission SEMs. Although nanometer-scale surface features can be examined at low incident beam voltages we still do not fully understand the factors that affect the contrast of low voltage SE images. At high incident beam voltages, SE1 (SEs generated by the incident probe) and SE2 (SEs generated by backscattered electrons at the sample surface) can be spatially separated. SE1 carries high-resolution detail while SE2 contributes to background. At low incident beam voltages, however, the interaction volume of the incident electrons shrinks rapidly with decreasing incident beam voltage. Thus, both the SE1 and SE2 signals carry high-resolution information. At low incident beam voltages, SE3 (SEs generated by backscattered electrons impinging on the sample chamber, pole pieces and etc.) also carries high-resolution detail and contributes significantly to the collected signal, especially for high atomic number materials and at short working distances.

Application of the Sterecon System for the Determination of Area, Volume, and Linear Distance of Cell Surface Topography of Secondary and Backscatter Electron Stereoscopic Images in Low-Voltage Field Emission SEM

1992 ◽  
Vol 50 (2) ◽  
pp. 1320-1321
Author(s):  
Stanley L. Erlandsen ◽  
Carol L. Wells ◽  
Stephen B. Olmsted ◽  
ArDean Leith ◽  
Michael Marko
Keyword(s):  
High Resolution ◽  
Surface Topography ◽  
Field Emission ◽  
Low Voltage ◽  
Bacterial Species ◽  
Quantitative Information ◽  
Backscatter Electron ◽  
Linear Distance ◽  
Scintillator Detectors

Extraction of quantitative information on surface topography in SEM can.be accomplished with, stereoscopic visual parallaxes. This method has received little attention in the last decade and to our knowledge has not been applied to high resolution secondary or backscatter electron images from field emission SEM. The STERECON system was developed for 3-D reconstruction of cells from stereo images obtained by high voltage EM. The present study describes the application of STERECON to quantitative determination of volume, surface area, and linear distance of topographical features in high resolution SEM.Trophozoites of the free-living protozoan, Hexamita inflata, and two bacterial species (Proteus mirabilus and Enterococcus faecalis) were fixed in 2.5-3.0% glutaraldehyde, dehydrated in ethanol, critical point dried in CO2, and coated with about 1 nm of platinum before examination at low kV (<4.0) in a Hitachi S-900 field emission SEM equipped with secondary (Se) and backscatter (YAG scintillator) detectors and photographed on Polaroid type 52 film using a stereo tilt of 8°.

A New High Resolution Field Emission SEM with Variable Pressure Capabilities

2001 ◽  
Vol 7 (S2) ◽  
pp. 880-881 ◽  
Author(s):  
Peter Gnauck ◽  
Volker Drexel ◽  
J. Greiser
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Low Voltage ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Chamber Pressure ◽  
Variable Pressure ◽  
Natural State ◽  
Electron Microscopes ◽  
Scanning Electron

To examine non conductive samples in their natural state (i.e. without significant sample preparation) at high resolution in the SEM the technique of low voltage field emission scanning electron microscopy (LVFESEM) is used. Due to the limitation in accelerating voltage (U<1kV) this technique is limited in respect of chemical analysis. Furthermore it is not possible to examine humid and outgassing samples in high vacuum. in recent years the application of variable pressure scanning electron microscopes (VPSEM) became an important technique in materials science as well as in life science. Due to the capability of maintaining a high chamber pressure humid, outgassing and non-conductive samples, can be examined in their natural state without significant sample modification or preparation. Especially compound materials with different electron yields can be imaged without any charging effects (Fig. 2), [2]. This paper describes a high resolution field emission electron microscope, that combines low voltage and variable pressure capabilities.The high pressure capabilities of the instrument are realized by eliminating the high vacuum requirements of SEM in the microscope chamber. This is done by separating the vacuum environment in the chamber from the ultra high vacuum environment in the gun area.

Low Voltage X-Ray Microanalysis of Bulk Bio-Organic Samples

1998 ◽  
Vol 4 (S2) ◽  
pp. 190-191
Author(s):  
Patrick Echlin
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Spatial Resolution ◽  
High Voltage ◽  
Biological Material ◽  
High Spatial Resolution ◽  
Low Voltage ◽  
Similar Type ◽  
The Other ◽  
X Ray

Although high resolution (2nm), low voltage (lkV), SEM of bio-organic materials can now be performed more or less routinely using instruments fitted with a field emission source, virtually no low voltage x-ray microanalysis has been carried out on this type of specimen. Boyes and Nockolds showed that quantitative microanalytical information could be obtained from polished inorganic samples at a spatial resolution of l00nm at 5kV and Johnson et al obtained similar type of data at a spatial resolution of 150nm at 3kV. High spatial resolution (l0nm) microanalysis can be achieved in frozen dried or chemically compromised sections of biological material examined at high voltage in the TEM but frozen hydrated chemically unfixed sections are damaged. The other approach is to use the SEM with frozen hydrated, chemically uncompromised samples, usually at about 10-15kV, in order to obtain sufficient signal from the elements of interest which typically lie in the range Na (Z=l 1) to Ca (Z=20).

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