Residual Gas Reactions in the Electron Microscope: I. Qualitative Observations on the Water Gas Reaction

1968 ◽  
Vol 26 ◽  
pp. 292-293
Author(s):  
Richard E. Hartman ◽  
Roberta S. Hartman ◽  
Peter L. Ramos
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Gas Phase ◽  
Absolute Temperature ◽  
Residual Gas ◽  
Gas Reactions ◽  
Image Position ◽  
The Right ◽  
Water Gas ◽  
Thinning Rate

The action of water and the electron beam on organic specimens in the electron microscope results in the removal of oxidizable material (primarily hydrogen and carbon) by reactions similar to the water gas reaction .which has the form:The energy required to force the reaction to the right is supplied by the interaction of the electron beam with the specimen.The mass of water striking the specimen is given by:where u = gH2O/cm2 sec, PH2O = partial pressure of water in Torr, & T = absolute temperature of the gas phase. If it is assumed that mass is removed from the specimen by a reaction approximated by (1) and that the specimen is uniformly thinned by the reaction, then the thinning rate in A/ min iswhere x = thickness of the specimen in A, t = time in minutes, & E = efficiency (the fraction of the water striking the specimen which reacts with it).

From the Scanning Electron Microscope to the Scanning Electron Macroscope with X-Ray Microanalysis in the ESEM

2000 ◽  
Vol 6 (S2) ◽  
pp. 792-793 ◽  
Author(s):  
Raynald Gauvin
Keyword(s):  
Monte Carlo ◽  
Electron Beam ◽  
Electron Microscope ◽  
Incident Beam ◽  
Correction Procedure ◽  
Measured Intensity ◽  
X Ray ◽  
Image Position ◽  
Corrected Intensity ◽  
Scanning Electron

Recently, a new correction procedure has been proposed in order to perform X-Ray microanalysis in the ESEM or in the VP-SEM1. This new correction procedure is based on this equation:where I is the measured intensity at a given pressure P, Ip is the intensity that would be generated without any gas in the microscope (the corrected intensity) and Im is the intensity with complete scattering of the electron beam. Im is therefore the contribution of the skirt on I. In equation (1), fp is the fraction of the incident beam, which is not scattered by the gas above the specimen, and it can be obtained from Monte Carlo simulations or from an analytical equation.

Electron trajectories in electrostatic fields

1992 ◽  
Vol 50 (2) ◽  
pp. 954-955
Author(s):  
Zbigniew Czyzewski ◽  
David C. Joy
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Magnetic Fields ◽  
Laplace Equation ◽  
Secondary Electron ◽  
Low Voltage ◽  
Electron Trajectories ◽  
Electrostatic Fields ◽  
Image Position ◽  
Detector Placement

Electron microscope use an electron beam to obtain various kind of information about specimen. The electron beam is focussed by electrostatic and magnetic fields and electron detectors employ electrostatic fields to attract or deflect electrons. In many cases the demand to calculate the electron trajectories in a fast and visual way is very strong. One of the most important questions is the problem of the secondary electron (SE) trajectories inside the SEM chamber and the effect of sample charging on detector yield. This is especially important in the low voltage SEM when investigating an uncoated, non-conductive specimen. A relatively large number of calculated trajectories gives a possibility to optimize SE detector placement as well as detector bias.The main problem is solving the Laplace equation in a 3-D space. In the 3-D space composed of cubic cells of dimension Δ3, the Laplace equation takes the following form:

Residual Gas Reactions in the Electron Microscope: IV. A Factor in Radiation Damage

1971 ◽  
Vol 29 ◽  
pp. 74-75
Author(s):  
Richard E. Hartman ◽  
Roberta S. Hartman
Keyword(s):  
Electron Microscope ◽  
Inelastic Scattering ◽  
Radiation Damage ◽  
Common Assumption ◽  
Step Process ◽  
One Step ◽  
The Common ◽  
Residual Gas ◽  
Gas Reactions ◽  
Dose Dependent

The common assumption that in the electron microscope there is a minimum, irreducible, dose-dependent damage to the specimen caused by inelastic scattering of electrons implies that such damage results from a one - step process. We now have evidence that this assumption is open to serious question.

Simple Identification of Electron Diffraction Ring Patterns

1969 ◽  
Vol 27 ◽  
pp. 160-161
Author(s):  
Carolyn Nohr ◽  
Ann Ayres
Keyword(s):  
Electron Microscope ◽  
Electron Diffraction ◽  
Diffraction Ring ◽  
Image Position

Texts on electron diffraction recommend that the camera constant of the electron microscope be determine d by calibration with a standard crystalline specimen, using the equation

Residual Gas Reaction in the Electron Microscope: II The Design of a Gas-Control Chamber for Quantitative Observations

1969 ◽  
Vol 27 ◽  
pp. 82-83
Author(s):  
Chester J. Calbick ◽  
Richard E. Hartman
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Local Environment ◽  
Chamber Pressure ◽  
Objective Lens ◽  
Ion Pump ◽  
Quantitative Studies ◽  
Precise Knowledge ◽  
Differential Pumping ◽  
And Control

Quantitative studies of the phenomenon associated with reactions induced by the electron beam between specimens and gases present in the electron microscope require precise knowledge and control of the local environment experienced by the portion of the specimen in the electron beam. Because of outgassing phenomena, the environment at the irradiated portion of the specimen is very different from that in any place where gas pressures and compositions can be measured. We have found that differential pumping of the specimen chamber by a 4" Orb-Ion pump, following roughing by a zeolite sorption pump, can produce a specimen-chamber pressure 100- to 1000-fold less than that in the region below the objective lens.

Modification of the Electron Microscope for Investigation of Fully Hydrated Biological Specimens

1969 ◽  
Vol 27 ◽  
pp. 418-419 ◽  
Author(s):  
R. C. Moretz ◽  
D. F. Parsons
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Structural Damage ◽  
Lower Percentage ◽  
Vacuum Drying ◽  
Total Removal ◽  
Total Absence ◽  
Biological Studies ◽  
Electron Microscopes ◽  
Beam Damage

Short lifetime or total absence of electron diffraction of ordered biological specimens is an indication that the specimen undergoes extensive molecular structural damage in the electron microscope. The specimen damage is due to the interaction of the electron beam (40-100 kV) with the specimen and the total removal of water from the structure by vacuum drying. The lower percentage of inelastic scattering at 1 MeV makes it possible to minimize the beam damage to the specimen. The elimination of vacuum drying by modification of the electron microscope is expected to allow more meaningful investigations of biological specimens at 100 kV until 1 MeV electron microscopes become more readily available. One modification, two-film microchambers, has been explored for both biological and non-biological studies.

X-ray microanalysis of thin specimens in the transmission electron microscope at voltages up to 1000 Kv.

1978 ◽  
Vol 36 (1) ◽  
pp. 540-541
Author(s):  
G. Cliff ◽  
M.J. Nasir ◽  
G.W. Lorimer ◽  
N. Ridley
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Weight Fraction ◽  
Present Series ◽  
Constant Independent ◽  
X Ray ◽  
Transmission Electron ◽  
Series Of Experiments ◽  
Image Position ◽  
X Ray Absorption

In a specimen which is transmission thin to 100 kV electrons - a sample in which X-ray absorption is so insignificant that it can be neglected and where fluorescence effects can generally be ignored (1,2) - a ratio of characteristic X-ray intensities, I1/I2 can be converted into a weight fraction ratio, C1/C2, using the equationwhere k12 is, at a given voltage, a constant independent of composition or thickness, k12 values can be determined experimentally from thin standards (3) or calculated (4,6). Both experimental and calculated k12 values have been obtained for K(11<Z>19),kα(Z>19) and some Lα radiation (3,6) at 100 kV. The object of the present series of experiments was to experimentally determine k12 values at voltages between 200 and 1000 kV and to compare these with calculated values.The experiments were carried out on an AEI-EM7 HVEM fitted with an energy dispersive X-ray detector.

Aspects of microanalysis in a transmission electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 510-511
Author(s):  
R. Sinclair ◽  
B.E. Jacobson
Keyword(s):  
Grain Size ◽  
Electron Beam ◽  
Electron Microscope ◽  
Chemical Analysis ◽  
Transmission Electron Microscope ◽  
Vapor Deposition ◽  
Critical Currents ◽  
X Ray ◽  
Fine Grain ◽  
Transmission Electron

INTRODUCTIONThe prospect of performing chemical analysis of thin specimens at any desired level of resolution is particularly appealing to the materials scientist. Commercial TEM-based systems are now available which virtually provide this capability. The purpose of this contribution is to illustrate its application to problems which would have been intractable until recently, pointing out some current limitations.X-RAY ANALYSISIn an attempt to fabricate superconducting materials with high critical currents and temperature, thin Nb3Sn films have been prepared by electron beam vapor deposition [1]. Fine-grain size material is desirable which may be achieved by codeposition with small amounts of Al2O3 . Figure 1 shows the STEM microstructure, with large (∽ 200 Å dia) voids present at the grain boundaries. Higher quality TEM micrographs (e.g. fig. 2) reveal the presence of small voids within the grains which are absent in pure Nb3Sn prepared under identical conditions. The X-ray spectrum from large (∽ lμ dia) or small (∽100 Ǻ dia) areas within the grains indicates only small amounts of A1 (fig.3).

The Analysis of Dislocations Using a Symmetry Criterion

1972 ◽  
Vol 30 ◽  
pp. 660-661
Author(s):  
J. C. Ingram ◽  
P. R. Strutt ◽  
Wen-Shian Tzeng
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Displacement Field ◽  
Standard Technique ◽  
Residual Image ◽  
Symmetry Criterion

The invisibility criterion which is the standard technique for determining the nature of dislocations seen in the electron microscope can at times lead to erroneous results or at best cause confusion in many cases since the dislocation can still show a residual image if the term is non-zero, or if the edge and screw displacements are anisotropically coupled, or if the dislocation has a mixed character. The symmetry criterion discussed below can be used in conjunction with and in some cases supersede the invisibility criterion for obtaining a valid determination of the nature of the dislocation.The symmetry criterion is based upon the well-known fact that a dislocation, because of the symmetric nature of its displacement field, can show a symmetric image when the dislocation is correctly oriented with respect to the electron beam.

A Device for Magnification Measurement

1972 ◽  
Vol 30 ◽  
pp. 622-623
Author(s):  
J.A. Eades ◽  
A. van Dun
Keyword(s):  
Electron Microscope ◽  
Small Displacement ◽  
Private Communication ◽  
Piezoelectric Crystal ◽  
Double Exposure ◽  
Standard Methods ◽  
Elegant Method ◽  
The Right ◽  
Piezo Electric

The measurement of magnification in the electron microscope is always troublesome especially when a goniometer stage is in use, since there can be wide variations from calibrated values. One elegant method (L.M.Brown, private communication) of avoiding the difficulties of standard methods would be to fit a device which displaces the specimen a small but known distance and recording the displacement by a double exposure. Such a device would obviate the need for changing the specimen and guarantee that the magnification was measured under precisely the conditions used.Such a small displacement could be produced by any suitable transducer mounted in one of the specimen translation mechanisms. In the present case a piezoelectric crystal was used. Modern synthetic piezo electric ceramics readily give reproducible displacements in the right range for quite modest voltages (for example: Joyce and Wilson, 1969).

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