Eine Methode zur Messung geringster Ölbedeckungen in Vakuumsystemen

1967 ◽  
Vol 22 (4) ◽  
pp. 549-553 ◽  
Author(s):  
R. Dobrozemsky ◽  
W. K. Huber ◽  
F. Viehböck
Keyword(s):  
High Vacuum ◽  
High Sensitivity ◽  
Radioactive Tracer ◽  
Operating Conditions ◽  
Ultra High Vacuum ◽  
Vacuum System ◽  
First Results ◽  
Tracer Isotope ◽  
Radioactive Tracer Method ◽  
Vacuum Systems

To get information on extremely small organic deposits in ultra high vacuum systems the sensitivity of most of the conventional methods for thickness measurements is not high enough. On the other hand the radioactive tracer method has shown its high sensitivity and wide versatility in many fields. Tritium with a half life of 12.3 γ and a mean β-energy of 5.4 keV was choosen as tracer isotope. A method is described for Tritium-labelling diffusion pump oils with specific activities up to 100 mC/g. Using the liquid scintillation counting technique one can detect deposits down to below 1010 molecules/cm2. First results with this Tritium labelled pump fluid are given under different operating conditions in an all metal ultra high vacuum system.

Development of the Cryo Pump System for Electron Microscope

1981 ◽  
Vol 39 ◽  
pp. 386-387
Author(s):  
M. Iwatsuki ◽  
Guy Venuti
Keyword(s):  
Electron Microscope ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Vacuum System ◽  
Ion Pumps ◽  
Pump System ◽  
Electron Microscopes ◽  
Vacuum Systems ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

In proportion, as the electron microscope expands the field as an analytical instrument, the problems of specimen contaimination will become more critical. Also, emission instability and short life of the LaB6 tips depend on the ultimate vacuum pressure in the gun chamber (particularly, due to the partial pressure of oxygenized molecules). Meanwhile, as scanning electron microscopes are utilized as a means for quality control in the semi-conductor field, as well as for analysis, the problems with specimen contamination will become more prominent.Today, DP-RP type pumps are widely used as high vacuum pumps in scanning electron microscopes. However, due to the oil used in these pumps, back-streaming occurs, causing specimen contamination. In contrast to this wet vacuum system, ion pumps, Ti-sublimation pumps, and Turbo-molecular pumps, etc. have been utilized as dry vacuum systems. Among these dry pumps, ion pumps and Ti-sublimation pumps are most popular as a means of obtaining ultra high vacuum. Also, Turbo-molecular pumps are widely used for scanning electron microscopes.

Discerning water contamination during freeze—fracturing on stearic acid crystal sheets

1992 ◽  
Vol 50 (1) ◽  
pp. 758-759
Author(s):  
Theo Müller ◽  
Heinz Gross
Keyword(s):  
High Vacuum ◽  
Saturation Pressure ◽  
Adsorbed Water ◽  
Ultra High Vacuum ◽  
Vacuum System ◽  
Condensation Temperature ◽  
Gas Atmosphere ◽  
Water Ph ◽  
Main Component ◽  
Vacuum Systems

In high vacuum (HV) systems, as well as in ultra high vacuum (UHV) systems that have not been sufficiently baked out, the main component of the residual gas atmosphere is water. Adsorbed water is present on all surfaces of the vacuum chamber. Whether or not ice introduced into such a vacuum system sublimes depends on its saturation pressure (at the surface, as a function of the specimen temperature )and on the surrounding partial pressure of water (pH2O). These facts must be considered when fracturing frozen biological material in vacuum systems. Thus the critical condensation temperature ( 162, 144.5, 130 K for 10−6, 10−8, 10-10 mbar, respectively) is an important factor in discussions of specimen fracture face contamination. Possibilities to reduce the rate of water condensation include the use of UHV (p < 10 —9 mbar) and/or surrounding the specimen with a cold, optically dense shroud system. When such a shroud is used, water molecules originating outside the shroud can only reach the specimen surface if they condense on and reevaporate from the shroud surface at least once (probability at T < 123 K is less than 10 4).

Coverage and Stability of NHx Terminated Cobalt and Ruthenium Surfaces: a First Principles Investigation

2019 ◽  
Author(s):  
Ji Liu ◽  
Michael Nolan
Keyword(s):  
Metal Surfaces ◽  
High Vacuum ◽  
Atomic Layer ◽  
Nitrogen Plasma ◽  
Operating Conditions ◽  
Ultra High Vacuum ◽  
Bridge Site ◽  
Stable Surface ◽  
Saturation Coverage ◽  
The Stability

<div>In the atomic layer deposition (ALD) of Cobalt (Co) and Ruthenium (Ru) metal using nitrogen plasma, the structure and composition of the post N-plasma NHx terminated (x = 1 or 2) metal surfaces are not well known but are important in the subsequent metal containing pulse. In this paper, we use the low-index (001) and (100) surfaces of Co and Ru as models of the metal polycrystalline thin films. The (001) surface with a hexagonal surface structure is the most stable surface and the (100) surface with a zigzag structure is the least stable surface but has high reactivity. We investigate the stability of NH and NH2 terminations on these surfaces to determine the saturation coverage of NHx on Co and Ru. NH is most stable in the hollow hcp site on (001) surface and the bridge site on the (100) surface, while NH2 prefers the bridge site on both (001) and (100) surfaces. The differential energy is calculated to find the saturation coverage of NH and NH2. We also present results on mixed NH/NH2-terminations. The results are analyzed by thermodynamics using Gibbs free energies (ΔG) to reveal temperature effects on the stability of NH and NH2 terminations. Ultra-high vacuum (UHV) and standard ALD</div><div>operating conditions are considered. Under typical ALD operating conditions we find that the most stable NHx terminated metal surfaces are 1 ML NH on Ru (001) surface (350K-550K), 5/9 ML NH on Co (001) surface (400K-650K) and a mixture of NH and NH2 on both Ru (100) and Co (100) surfaces.</div>

The design and study of a compact bakeable ultra-high vacuum system for calibrating absolutely low pressure gauges

Vacuum ◽  
1977 ◽  
Vol 27 (9) ◽  
pp. 511-517 ◽  
Author(s):  
K.J. Close ◽  
R.S. Vaughan-Watkins ◽  
J Yarwood
Keyword(s):  
High Vacuum ◽  
Low Pressure ◽  
Ultra High Vacuum ◽  
Vacuum System

scholarly journals Why Pressure Scales Cause So Much Confusion

1993 ◽  
Vol 1 (8) ◽  
pp. 5-6
Author(s):  
Anthony D. Buonaquisti
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Ambient Pressure ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Vacuum System ◽  
Scanning Auger Microprobe ◽  
The Mean ◽  
Scanning Electron

Pressure scales can be extremely confusing to new operators. This is not surprising. To my mind, there are three primary areas of confusion.Firstly, the pressure of gas inside an instrument changes over many orders of magnitude during pumpdown. The change is about 9 orders of magnitude for a traditional Scanning Electron Microscope and about 13 orders of magnitude for an ultra-high vacuum instrument such as a Scanning Auger Microprobe.To give an idea about the scale of change involved in vacuum, consider that the change in going from ambient pressure to that inside a typical ultra high vacuum system is like comparing one meter with the mean radius of the planet Pluto's orbit. The fact is that we don't often get to play with things on that scale. As a consequence, many of us have to keep reminding ourselves that 1 X 10-3 is one thousand times the value of 1 X 10-6 - not twice the value.

scholarly journals Optical contamination control in the Advanced LIGO ultra-high vacuum system

2013 ◽  
Author(s):  
Margot H. Phelps ◽  
Kaitlin E. Gushwa ◽  
Calum I. Torrie
Keyword(s):  
High Vacuum ◽  
Ultra High Vacuum ◽  
Vacuum System ◽  
Contamination Control
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