Guide Ultrahigh Vacuum Practice

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However, extended high-temperature active-nitrogen cleaning leads to severe surface roughening. Optimum results regarding both the removal of surface oxides as well as the surface structural and morphological quality have been achieved for a combination of initial low-temperature plasma-assisted cleaning, followed by a rapid nitrogen plasma-assisted cleaning at high temperature. Ultrahigh vacuum and low-temperature cleaning of oxide surfaces using a low-concentration ozone beam. We present a novel method of delivering a low-concentration ultra-high vacuum environment for the purpose of cleaning and dosing experimental samples through oxidation processing.

The system described is safe, low-cost, and practical and overcomes the limitations of ozone transport in the molecular flow environment of high or ultrahigh vacuum whilst circumventing the use of pure ozone gas which is potentially highly explosive. Additionally, we demonstrate the potential of ozone for obtaining clean complex oxide surfaces without the need for high-temperature annealing which may significantly alter surface structure.

The surface variation of TiAlNb as a function of temperature under ultrahigh vacuum conditions. The effect of temperature, at conditions of ultrahigh vacuum , on the surface composition of the TiAlNb in wt pct alloy was investigated in samples heated to C in C increments.

At C, the carbon and oxygen began to rapidly dissolve into the alloy, and at C, bulk S segregated to the surface.

A Review: Ultrahigh-Vacuum Technology for Electron Microscopes

The variation in the surface composition was extensive and different over the temperature range studied, indicating that there may be substantial changes in the hydrogen transport. Multifunctional ultra-high vacuum apparatus for studies of the interactions of chemical warfare agents on complex surfaces. Wilmsmeyer, Amanda R. A fundamental understanding of the surface chemistry of chemical warfare agents is needed to fully predict the interaction of these toxic molecules with militarily relevant materials, catalysts, and environmental surfaces.

For example, rules for predicting the surface chemistry of agents can be applied to the creation of next generation decontaminants, reactive coatings, and protective materials for the warfighter. Here, we describe a multifunctional ultra-high vacuum instrument for conducting comprehensive studies of the adsorption, desorption, and surface chemistry of chemical warfare agents on model and militarily relevant surfaces.

The system applies reflection-absorption infrared spectroscopy, x-ray photoelectron spectroscopy, and mass spectrometry to study adsorption and surface reactions of chemical warfare agents. Several novel components have been developed to address the unique safety and sample exposure challenges that accompany the research of these toxic, often very low vapor pressure, compounds.

While results of vacuum -based surface science techniques may not necessarily translate directly to environmental processes, learning about the fundamental chemistry will begin to inform scientists about the critical aspects that impact real-world applications. Advanced Photon Source accelerator ultrahigh vacuum guide. In this document the authors summarize the following: 1 an overview of basic concepts of ultrahigh vacuum needed for the APS project, 2 a description of vacuum design and calculations for major parts of APS, including linac, linac waveguide, low energy undulator test line, positron accumulator ring PAR , booster synchrotron ring, storage ring, and insertion devices, and 3 cleaning procedures of ultrahigh vacuum UHV components presently used at APS.

Ultra-high vacuum surface analysis study of rhodopsin incorporation into supported lipid bilayers. Planar supported lipid bilayers that are stable under ambient atmospheric and ultra-high- vacuum conditions were prepared by cross-linking polymerization of bis-sorbylphosphatidylcholine bis-SorbPC. X-ray photoelectron spectroscopy XPS and time-of-flight secondary ion mass spectrometry ToF-SIMS were employed to investigate bilayers that were cross-linked using either redox-initiated radical polymerization or ultraviolet photopolymerization.

The redox method yields a more structurally intact bilayer; however, the UV method is more compatible with incorporation of transmembrane proteins. UV polymerization was therefore used to prepare cross-linked bilayers with incorporated bovine rhodopsin, a light-activated, G-protein-coupled receptor GPCR.

A previous study Subramaniam, V. In this study, we show that rhodopsin is retained in supported bilayers of poly bis-SorbPC under ultra-high- vacuum conditions, on the basis of the increase in the XPS nitrogen concentration and the presence of characteristic amino acid peaks in the ToF-SIMS data. Angle-resolved XPS data show that the protein is inserted into the bilayer, rather than adsorbed on the bilayer surface. This is the first study to demonstrate the use of ultra-high- vacuum techniques for structural studies of supported proteolipid bilayers. Ultrahigh vacuum gauge having two collector electrodes.

A gauge for measuring ultrahigh vacuums with great accuracy is described.

Ultrahigh Vacuum Practice

It provides a means for ionizing the gas whose pressure is being measured, and consists of a collector electrode, a suppressor, radiation shielding, and a second collector. Sample mounting and transfer for coupling an ultrahigh vacuum variable temperature beetle scanning tunneling microscope with conventional surface probes.

We present a new ultrahigh vacuum UHV chamber for surface analysis and microscopy at controlled, variable temperatures. The new instrument allows surface analysis with Auger electron spectroscopy, low energy electron diffraction, quadrupole mass spectrometer, argon ion sputtering gun, and a variable temperature scanning tunneling microscope VT-STM.

In this system, we introduce a novel procedure for transferring a sample off a conventional UHV manipulator and onto a scanning tunneling microscope in the conventional ''beetle'' geometry, without disconnecting the heating or thermocouple wires. The microscope, a modified version of the Besocke beetle microscope, is mounted on a 2.

The sample is attached to a tripod sample holder that is held by the main manipulator. The performance of the chamber is demonstrated here by producing an ordered array of island vacancy defects on a Pt surface and obtaining STM images of these defects. Cu In,Ga Se2 surface treatment with Na and NaF: A combined photoelectron spectroscopy and surface photovoltage study in ultra-high vacuum.

Parvan, V. Either metallic Na or NaF were deposited onto Cu In,Ga Se2 surfaces and studied by photoelectron spectroscopy and surface photovoltage spectroscopy without breaking the ultra-high vacuum. A metal like surface induced by an inverted near surface region with a reduced number of defect states was formed after the deposition of Na. Under the chosen experimental conditions, the near surface layer was independent on the amount of Na and stable in time.

In contrast, the usage of NaF weakened the inversion and led to an increased band bending compared to the untreated CIGSe sample. Thesis - va. Polytechnic Inst. The physical adsorption of nitrogen on the chemically cleaned surfaces of Pyrex, stainless steel and polycrystalline nickel was investigated over the pressure range 1 x 10 to the minus 12th power to 3 x 10 to the minus 7th power torr and for temperatures The adsorption data were linearized by the Dubinin-Radushkevich equation.

The metal surfaces were cleaned by electron impact desorption EID and the desorbed gases analyzed by mass spectrometry. Work function measurements were also used to indicate changes in the surface condition following an EID dose. At least a monolayer of gas was observed to desorb from the metal surfaces. The isotherms revealed that the metal surfaces were very heterogeneous and that the Pyrex surface had been leached.

The calculated isosteric heats of adsorption indicated that the relative order of the physical binding of nitrogen to the solids was stainless steel Pyrex nickel. A relationship was observed to exist in the dynamic technique between the equilibration time and the pressure above the absorbed layer. The slope of the log-log plot of these parameters was found to be sensitive to the surface heterogeneity and may be related to the activation energy for surface diffusion of physically absorbed molecules. Ultrahigh vacuum process for the deposition of nanotubes and nanowires. A system and method A method of growing an elongate nanoelement from a growth surface includes: a cleaning a growth surface on a base element; b providing an ultrahigh vacuum reaction environment over the cleaned growth surface ; c generating a reactive gas of an atomic material to be used in forming the nanoelement; d projecting a stream of the reactive gas at the growth surface within the reactive environment while maintaining a vacuum of at most 1.

Degassing procedure for ultrahigh vacuum. Calculations based on diffusion coefficients and degassing rates for stainless-steel vacuum chambers indicate that baking at lower temperatures for longer periods give lower ultimate pressures than rapid baking at high temperatures. Process could reduce pressures in chambers for particle accelerators, fusion reactors, material research, and other applications. Three-configurational surface magneto-optical Kerr effect measurement system for an ultrahigh vacuum in situ study of ultrathin magnetic films.

We have constructed a three-configurational surface magneto-optical Kerr effect system, which provides the simultaneous measurements of the "polar," "longitudinal," and "transverse" Kerr hysteresis loops at the position where deposition is carried out in an ultrahigh vacuum growth chamber. The present system enables in situ three-dimensional vectorial studies of ultrathin film magnetism with a submonolayer sensitivity.

Experimental system for drilling simulated lunar rock in ultrahigh vacuum. An experimental apparatus designed for studying drillability of hard volcanic rock in a simulated lunar vacuum of 5 x 10 to the minus 10th power torr is described. The engineering techniques used to provide suitable drilling torque inside the ultrahigh vacuum chamber while excluding all hydrocarbon are detailed.

Totally unlubricated bearings and gears were used to better approximate the true lunar surface conditions within the ultrahigh vacuum system. The drilling system has a starting torque of 30 in-lb with an unloaded running torque of 4 in-lb. Nominal torque increase during drilling is 4. The research shows conclusively that it is possible to design operational equipment for moderate loads operating under UHV conditions without the use of sealed bearings or any need of lubricants whatsoever.

Characteristic modes of the sarin molecule itself are also ob- served. These experimental results show While results of vacuum -based surface science. The valve is capable of withstanding extended baking at deg C and repeated opening and closing without repiacement of the valve seat approximately cycle limit. The seal is formed by mutual interdiffusion weld, coerced by a pneumatic actuator. Reactive and non-reactive interactions of thiophene with WS2 fullerene-like nanoparticles: an ultra-high vacuum surface chemistry study.

Definition of vacuum

The adsorption kinetics of thiophene on WS2 nanoparticles with fullerene-like onion-like structure has been studied at ultra-high vacuum conditions by sample temperature ramping techniques. At low temperatures, thiophene adsorbs molecularly. The formation of H2S and alkanes is evident at greater temperatures on fully sulfided as well as reduced and oxidized WS2 nanoparticles. Ge quantum dot arrays grown by ultrahigh vacuum molecular-beam epitaxy on the Si surface : nucleation, morphology, and CMOS compatibility.

PubMed Central. Issues of morphology, nucleation, and growth of Ge cluster arrays deposited by ultrahigh vacuum molecular beam epitaxy on the Si surface are considered. The atomic models of growth of both species of Ge huts--pyramids and wedges-- are proposed.

The growth cycle of Ge QD arrays at low temperatures is explored. The temperature of the Si clean surface preparation, the final high-temperature step of which is, as a rule, carried out directly in the MBE chamber just before the structure deposition, determines the compatibility of formation process of Ge-QD-array based devices with the CMOS manufacturing cycle. Silicon surface hydrogenation at the final stage of its wet chemical etching during the preliminary cleaning is proposed as a possible way of efficient reduction of the Si wafer pre-growth annealing temperature.

High field electron paramagnetic resonance spectroscopy under ultrahigh vacuum conditions—A multipurpose machine to study paramagnetic species on well defined single crystal surfaces.


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