Stage cooling rates and specimen-transfer facilities of the Duke University cryomicroscope

1983 ◽  
Vol 41 ◽  
pp. 306-307
Author(s):  
M.K. Lamvik ◽  
R.E. Worsham ◽  
D.A. Kopf ◽  
J.D. Robertson
Keyword(s):  
Liquid Helium ◽  
National Laboratory ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Objective Lens ◽  
Oak Ridge ◽  
Fold Reduction ◽  
Resolution Electron ◽  
Biological Studies ◽  
Duke University

A liquid helium cold stage offers unique advantages for biological electron microscopy, including a five-fold reduction in radiation damage, higher ultimate specimen resolution and greater stability for frozen hydrated specimens. Ultra-high vacuum and reduced surface diffusion also reduce specimen contamination to negligible levels. To make efficient use of these advantages in biological studies, however, the microscope must be able to handle a variety of specimens while quickly achieving low temperature.The cryomicroscope that is currently in operation at Duke University (Fig. 1) was originally designed and built at Oak Ridge National Laboratory as a high-resolution electron microscope with a superconducting objective lens. The well-shielded cryostat for the objective lens assures a low specimen temperature. There are two thermal shields surrounding the liquid helium vessel, each cooled by the venting cold helium gas. The inner shield is at its nominal value, 20°K, at the end of the helium transfer when gas is actively venting from the system; later during routine operation, the inner shield temperature is about 30°K.

A Liquid Helium Cryostat for a Superconducting Objective and Cold Stage

1976 ◽  
Vol 34 ◽  
pp. 532-533
Author(s):  
R. E. Worsham ◽  
J. E. Mann
Keyword(s):  
Liquid Helium ◽  
High Vacuum ◽  
Strong Support ◽  
Liquid Helium Temperature ◽  
Ultra High Vacuum ◽  
Objective Lens ◽  
Helium Temperature ◽  
Different Temperatures ◽  
Radiation Shields ◽  
High Coherence

In the design of the 150 kV High-Coherence Column, it was considered essential that the specimen be in ultra-high vacuum at liquid helium temperature for minimum radiation damage. It followed that the simplest solution was to make the entire region about the specimen at liquid helium temperature and to make the objective lens with a superconducting winding.For mechanical rigidity, two things were considered essential. First, a strong support structure for the liquid helium vessel and the objective lens. Second, the use of no liquid nitrogen but rather the use of helium vapor cooling for the radiation shields, leads and supports. The drawing, fig. 1, shows the helium vessel, 9-1/2-inches diameter by 5-inches tall, surrounded by two concentric radiation shields. The entire assembly is rigidly supported on four posts one of which is shown. These posts consist of cylinders of epoxyglass (G-10) spacing the components between their different temperatures.

Liquid Helium Cryostat for the Imaging System of a High Resolution Electron Microscope

1975 ◽  
Vol 33 ◽  
pp. 154-155
Author(s):  
D. L. Musinski ◽  
S. T. Wang ◽  
B. M. Siegel
Keyword(s):  
High Resolution ◽  
Liquid Helium ◽  
Imaging System ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Basic Design ◽  
Optimum Conditions ◽  
Resolution Electron ◽  
High Resolution Electron Microscope ◽  
High Resolution Microscopy

The specimen environment for high resolution microscopy of biomolecular materials is critical. To obtain the optimum conditions we maintain the specimen in an ultra high vacuum (10-10 Torr) and at liquid helium temperatures to minimize contamination and hopefully radiation damage. To meet these specifications, the imaging system composed of the cryostat shown in the schematic drawing was developed and constructed. Besides assuring that the basic design does not limit the desired resolution, our cryostat offers the maximum in engineering flexibility so alternate lens configurations or even extensive design modifications are relatively easy to accomplish.

UHV conversion of a 300 kV high-resolution electron microscope

1987 ◽  
Vol 45 ◽  
pp. 136-137
Author(s):  
Peter R. Swann ◽  
Joseph S. Jones ◽  
Ondrei L. Krivanek ◽  
David J. Smith ◽  
John A. Venables ◽  
...  
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Full Range ◽  
High Vacuum ◽  
High Resolution Electron Microscopy ◽  
Ultra High Vacuum ◽  
Objective Lens ◽  
Surface And Interface ◽  
Resolution Electron ◽  
Point To Point

Ultra-high-vacuum high-resolution electron microscopy (UHV-HREM) is a powerful technique for studying the structure of surfaces, and for characterizing the mechanisms and kinetics of surface and interface reactions. It requires an electron microscope capable of atomic resolution, a vacuum of about 10-10 torr around the sample, and a range of specimen treatment capabilities. We have replaced the standard specimen chamber of a Philips 430ST high resolution microscope by a special UHV chamber which allows for limited specimen treatment in-situ, and a full range of specimen treatments in a preparation chamber mounted on the side of the microscope column. At 300 kV, the objective lens (Cs= Cc = 1.1mm) of the 430ST has demonstrated a point-to-point resolution of 2.0 Å, and a spatial frequency transfer limit with axial illumination of better than 1.5 Å. A critical specification for the microscope conversion was that this performance should not be compromised even under full UHV operation.

Development Program for a 500-kV High Resolution Microscope

1969 ◽  
Vol 27 ◽  
pp. 184-185
Author(s):  
R. E. Worsham ◽  
J. E. Mann ◽  
E. G. Richardson ◽  
G. G. Slaughter ◽  
N. F. Ziegler
Keyword(s):  
High Resolution ◽  
Liquid Helium ◽  
Spherical Aberration ◽  
National Laboratory ◽  
Development Program ◽  
Objective Lens ◽  
Helium Temperature ◽  
Oak Ridge ◽  
Point To Point ◽  
High Resolution Microscopy

The goal of the development program for high resolution microscopy at Oak Ridge National Laboratory is a 100-500 kV instrument with a point-to-point resolution of at least 1Å. As reported previously, this microscope is intended for biological specimens to be observed at liquid helium temperature. This resolution is to be achieved principally by reduction of the primary spherical aberration for the objective lens with a quadrupole-octupole system of lenses.

A Field Emission System For Transmission Electron Microscopy

1973 ◽  
Vol 31 ◽  
pp. 298-299
Author(s):  
Michel Troyonal ◽  
Huei Pei Kuoal ◽  
Benjamin M. Siegelal
Keyword(s):  
Electron Microscope ◽  
Field Emission ◽  
Optical System ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Objective Lens ◽  
Electron Optical System ◽  
Cross Sectional ◽  
Transmission Electron ◽  
Emission System

A field emission system for our experimental ultra high vacuum electron microscope has been designed, constructed and tested. The electron optical system is based on the prototype whose performance has already been reported. A cross-sectional schematic illustrating the field emission source, preaccelerator lens and accelerator is given in Fig. 1. This field emission system is designed to be used with an electron microscope operated at 100-150kV in the conventional transmission mode. The electron optical system used to control the imaging of the field emission beam on the specimen consists of a weak condenser lens and the pre-field of a strong objective lens. The pre-accelerator lens is an einzel lens and is operated together with the accelerator in the constant angular magnification mode (CAM).

Atomic-level imaging of the surface structure of Ag2O

1984 ◽  
Vol 42 ◽  
pp. 656-657
Author(s):  
William Krakow
Keyword(s):  
High Vacuum ◽  
Atomic Level ◽  
Ultra High Vacuum ◽  
Research Groups ◽  
Resolution Electron ◽  
Surface Reconstructions ◽  
Order Of Magnitude ◽  
High Resolution Electron Microscope ◽  
Saturated Structure ◽  
Transmission And Reflection

In recent years electron microscopy has been used to image surfaces in both the transmission and reflection modes by many research groups. Some of this work has been performed under ultra high vacuum conditions (UHV) and apparent surface reconstructions observed. The level of resolution generally has been at least an order of magnitude worse than is necessary to visualize atoms directly and therefore the detailed atomic rearrangements of the surface are not known. The present author has achieved atomic level resolution under normal vacuum conditions of various Au surfaces. Unfortunately these samples were exposed to atmosphere and could not be cleaned in a standard high resolution electron microscope. The result obtained surfaces which were impurity stabilized and reveal the bulk lattice (1x1) type surface structures also encountered by other surface physics techniques under impure or overlayer contaminant conditions. It was therefore decided to study a system where exposure to air was unimportant by using a oxygen saturated structure, Ag2O, and seeking to find surface reconstructions, which will now be described.

Observation of GaAs/Si Epitaxial Interfaces by Atomic Resolution Electron Microscopy

1986 ◽  
Vol 67 ◽  
Author(s):  
N. Otsuka ◽  
C. Choi ◽  
Y. Nakamura ◽  
S. Nagakura ◽  
R. Fischer ◽  
...  
Keyword(s):  
Substrate Surface ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Threading Dislocations ◽  
Misfit Dislocations ◽  
Si Substrates ◽  
Voltage Electron ◽  
Resolution Electron ◽  
Gaas Films ◽  
Substrate Surfaces

ABSTRACTRecent studies have shown that high quality GaAs films can be grown by MBE on Si substrates whose surfaces are slightly tilted from the (100) plane. In order to investigate the effect of the tilting of substrate surfaces on the formation of threading dislocations, the GaAs/Si epitaxial interfaces have been observed with a 1 MB ultra-high vacuum, high voltage electron microscope. Two types of misfit dislocations, one with Burgers vectors parallel to the interface and the other with Burgers vectors inclined from the interface, were found in these epitaxial interfaces. The observation of crosssectional samples perpendicular to each other has shown that the tilting of the substrate surface directly influences the generation of these two types of misfit dislocations. The mechanism of the reduction of threading dislocations by the tilting of the substrate surface is discussed based on these observations.

Energy Filtering of Schottky Field Emission Gun Using Fringe Field Monochromator

1999 ◽  
Vol 5 (S2) ◽  
pp. 646-647
Author(s):  
H.W. Mook ◽  
A.H.V. van Veen ◽  
P. Kruit
Keyword(s):  
Field Emission ◽  
Low Voltage ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Electron Gun ◽  
Fringe Field ◽  
Objective Lens ◽  
Electronic Band ◽  
Energy Width ◽  
Energy Filtering

The energy resolution which can be attained in electron energy loss spectroscopy (EELS) is determined by the energy spread of the electron source. The energy width of a high brightness electron gun (typically 0.4 to 0.8 eV) blurs the energy spectrum. A pre-specimen energy filter or monochromator must be used to reduce the energy width of the beam below 0.1 eV to allow detailed EELS analysis of the electronic band structures in materials. The monochromator can not only improve EELS, but it is also capable of improving the spatial resolution in low voltage SEM, which is limited by the chromatic blur of the objective lens. A new type of monochromator the Fringe Field Monochromator has been designed and experiments in an ultra high vacuum setup show the monochromatisation of a Schottky Field Emission Gun.

The ORNL Aberration-Corrected STEM/TEM Project

2001 ◽  
Vol 7 (S2) ◽  
pp. 906-907
Author(s):  
L. F. Allard ◽  
E. Voelkl ◽  
D. A. Blom ◽  
T. A. Nolan ◽  
F. Kahl ◽  
...  
Keyword(s):  
Spherical Aberration ◽  
National Laboratory ◽  
Dark Field ◽  
Electron Gun ◽  
Objective Lens ◽  
Resolution Limit ◽  
Oak Ridge ◽  
Transfer Characteristics ◽  
Dark Field Imaging ◽  
Electron Microscopes

Field emission electron microscopes operating at 200kV or 300kV and incorporating aberration correctors for either the incident electron probe or for the primary aberrations of the objective lens (OL) are currently under development for several laboratories in the world. OL-corrected instruments require monochromators for the electron beam, built into the electron gun prior to the accelerating stages, in order to optimize the contrast transfer characteristics of the objective lens to push the instrumental resolution limit to well beyond 0.1nm. This will allow the point resolution limit as controlled by the correction of spherical aberration Cs to potentially extend to the instrumental limit of better than 0.1nm. Figure 1 shows the contrast transfer characteristics of a Cs-corrected 200kV TEM, both without and with a beam monochromator.Dedicated STEM instruments such as the 300kV VG-603 and lOOkV VG-501 at Oak Ridge National Laboratory, and other VG instruments at Cornell University and IBM Co. are also being adapted (by Nion Co., Kirkland, WA) to incorporate aberration correctors for the incident probe. The aim is to improve the resolution of the VG-603 instrument in dark-field imaging mode, for example, from 0.13nm to 0.05nm. in another ORNL project, the High Temperature Materials Laboratory has contracted JEOL Ltd. to construct a STEM-TEM instrument with a probe corrector designed and built by CEOS GmbH (Heidelberg, Germany).

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