Pt/Ir/C, a new, powerful coating material for High-Resolution SEM

1990 ◽  
Vol 48 (3) ◽  
pp. 6-7
Author(s):  
Roger Wepf ◽  
Heinz Gross
Keyword(s):  
Freeze Drying ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Type I ◽  
Atmospheric Conditions ◽  
Coating Films ◽  
Hydration Shells ◽  
Probe Size ◽  
Structural Preservation ◽  
The Right

In-lens field emission SEM allows to image specimen surfaces with subnanometer resolution by collecting type I secondary electrons, with an incident electron probe size of abut 0.5 nm in diameter. To achieve such high topographic resolution on biological specimens adequate structural preservation and high resolving thin continuous coating films are necessary.Careful freeze-drying (“maintaining hydration shells”) followed by heavy metal shadowing at -250°C under ultra high vacuum conditions (UHV) allows to extract surface features ≤2 nm with TEM. TEM-shadowing films (Pt/C, Ta/W) are stabilized with a C-backing layer. Such a C-coat would blurr fine details when investigated with the SEM.At the right composition (C-content 25-40%, metal content 75-60%) only about 1.5 nm thick Pt/Ir/C-films remain three-dimensionally stable when transferred to atmospheric conditions after freeze-drying samples with macromolecular dimensions. Pt/Ir/C is made by evaporating a Pt/Ir cylinder (diameter 1.5 mm, 70% Ir) inserted into a graphite rod (diameter 2 mm).

Using a Moderate Vacuum, Hot/Cryo-Stage Equipped AFM for In-Situ Observation of α-Phase Growth In 60SN40PB Hypoeutectic Solder

1998 ◽  
Vol 4 (S2) ◽  
pp. 316-317
Author(s):  
D. N. Leonard ◽  
P.E. Russell
Keyword(s):  
Surface Science ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Scanning Tunneling ◽  
In Situ Observation ◽  
Atmospheric Conditions ◽  
Tunneling Microscopy ◽  
Wide Range ◽  
Gas Environment

Atomic force microscopy (AFM) was introduced in 1984, and proved to be more versatile than scanning tunneling microscopy (STM) due to the AFM's capabilities to scan non-conductive samples under atmospheric conditions and achieve atomic resolution. Ultra high vacuum (UHV) AFM has been used in surface science applications when control of oxidation and corrosion of a sample's surface are required. Expensive equipment and time consuming sample exchanges are two drawbacks of the UHV AFM system that limit its use. Until recently, no hot/cryo-stage, moderate vacuum, controlled gas environment AFM was commonly available.We have demonstrated that phase transformations are easily observable in metal alloys and polymers with the use of a moderate vacuum AFM that has in-situ heating/cooling capabilities and quick (within minutes) sample exchange times. This talk will describe the results of experiments involving a wide range of samples designed to make use of the full capabilities of a hot/cryo-stage, controlled gas environment AFM.

Band Alignment of Si1-xGex And Si1-x-y.GexCy Quantum Wells On Si (001)

1998 ◽  
Vol 533 ◽  
Author(s):  
N. L. Rowell ◽  
R. L. Williams ◽  
G. C. Aers ◽  
H. Lafontaine ◽  
D. C. Houghton ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Applied Stress ◽  
Vapour Deposition ◽  
Stress Condition ◽  
High Vacuum ◽  
Chemical Vapour ◽  
Band Alignment ◽  
Ultra High Vacuum ◽  
Multiple Quantum ◽  
Type I

AbstractRecent low-temperature photoluminescence (PL) studies will be discussed for coherent Si1-xGex. and Si1-xGexCy alloy multiple quantum wells on Si (001) substrates grown by either ultra-high vacuum chemical vapour deposition or solid source molecular beam epitaxy. An in-plane applied-stress technique will be described which removes systematically band edge degeneracies revealing the lower, PL-active CB. Applied-stress data taken with this technique at ultra-low excitation intensity proved intrinsic type II CB alignment in SiGe on Si (001). Apparent type I alignment observed at higher intensity will also be discussed. New applied stress PL results are presented for Si1-x-yGexCy quantum wells under various grown-in stress condition

Scanning Reflection Electron Microscopy of 2x1 Domain Structure of Si(111) Surface

1985 ◽  
Vol 43 ◽  
pp. 264-265
Author(s):  
H.-J. Ou
Keyword(s):  
Electron Microscopy ◽  
Electron Diffraction ◽  
Spatial Resolution ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Intermediate Energies ◽  
Good Spatial Resolution ◽  
Probe Size ◽  
Reflection Electron Microscopy ◽  
Better Than

Studies of the surface structure of silicon with good spatial resolution made recently by reflection electron microscopy, (REM) have complemented and greatly extended the earlier studies, made by LEED and other methods, of the formation of surface reconstruction superstructures such a the Si(111) 7x7. These studies have not included the 2x1 superstructure on (111) surfaces formed by cleaving Si crystals in ultra-high vacuum. We have now investigated the form of the domains of this 2x1 structure by use of a reconstructed REMEDIE system 2.3 (for Reflection Electron Microscopy and Electron Diffraction at Intermediate Energies, 1-20keV). This system has shown a spatial resolution of better than 100Å although resolutions of about 300Å may be more common in practise because of the limitations due to probe size, vibration and signal noise.

Solid lubrication with MoS2-Ti-C films for high-vacuum applications in a nuclear fusion experimental device

2018 ◽  
Vol 70 (1) ◽  
pp. 155-160 ◽  
Author(s):  
Shanshuang Shi ◽  
Huapeng Wu ◽  
Yuntao Song ◽  
Heikki Handroos
Keyword(s):  
High Vacuum ◽  
Ultra High Vacuum ◽  
Experimental Device ◽  
Solid Lubrication ◽  
Hybrid Coatings ◽  
Vacuum Vessel ◽  
Coating Films ◽  
Content Type ◽  
Sputtering Deposition ◽  
Inner Vessel

Purpose This paper aims to present a study on composite coating films for solid lubrication applied on the surface of bearings and gears, which are exposed to the vacuum vessel of a tokamak fusion experimental device running under ultra-high vacuum conditions. Experimental advanced superconducting tokamak is a tokamak fusion experimental device running under ultra-high vacuum conditions. To avoid polluting the inner vessel environment, solid lubrication has been applied on the surface of bearings and gears, which are exposed to the vacuum. Design/methodology/approach Anti-friction MoS2 coatings integrated with Titanium and Carbon have been developed using the multi-target magnetron sputtering deposition technique. This paper presents the comparative testing of tribological properties for three kinds of MoS2-based coating layers. Findings Based on the test results, MoS2-Ti-C coating films are supposed to be the final selection because of the better performance of friction coefficient and lubrication longevity. Originality/value Finally, the detailed information has been characterized for the hybrid coatings, which can provide some references for applications of solid lubrications under similar conditions of high vacuum and temperature.

Ultra High Vacuum Scanning Electron Microscopy of Directly Deposited Metallic Films

1971 ◽  
Vol 29 ◽  
pp. 228-229
Author(s):  
J. P. Ballantyne ◽  
C. Dix ◽  
W. C. Nixon
Keyword(s):  
Integrated Circuit ◽  
High Vacuum ◽  
Steel Specimen ◽  
Ultra High Vacuum ◽  
Main Reaction ◽  
Partial Pressures ◽  
Probe Size ◽  
Main Column ◽  
Differential Pumping ◽  
Scanning Electron

A basic scanning electron microscope of similar construction to that described by Pease and Nixon has been modified for ultra high vacuum by using a special stainless steel specimen chamber. The final aperture of the electron optical column is also the differential pumping aperture separating the lens and scan coil region from the specimen chamber. Recent further refinement has given a measured vacuum in the specimen region of 1 x 10-10 torr after baking and day to day operation at 10-8 torr. The specimen stage stability and the electron optical performance permit an electron probe size of 200-300 A at these vacuum levels. The main column is pumped to 10-6 torr.This improved vacuum performance is necessary for depositing and viewing thin metal films as there is no residual contamination and no effect of partial pressures of gases to influence the main reaction. Both silver and tin films have been deposited from halide compounds with a resulting metal thickness of about one micron giving reasonable conductivity. The substrate is silicon of integrated circuit quality.

The adsorption of copper on tungsten

1965 ◽  
Vol 284 (1399) ◽  
pp. 469-487 ◽  
Keyword(s):  
Activation Energy ◽  
Work Function ◽  
Lattice Structure ◽  
High Vacuum ◽  
Copper Deposit ◽  
Ultra High Vacuum ◽  
Type I ◽  
Type Ii ◽  
Kcal Mole ◽  
Type Iii

A detailed examination has been made by field emission microscopy, of the behaviour of small amounts of copper evaporated onto a clean tungsten point in ultra high vacuum. With increasing thickness, the behaviour of the copper deposit and its effect on work function, change in a way which leads to classification of three types of copper layer. Small amounts of copper form a layer on the surface which raises the work function from 4.52 to 4.83 eV, and can be desorbed therm ally with activation energy 95±6 kcal/mole. It is termed type I, and is believed to form the first monolayer of copper in which all adatoms are bonded directly to tungsten and are therefore polarized negative outward, giving rise to the observed increase in work function. Copper adsorbed upon the type I layer forms type II, which lowers the work function to 4.2 eV, diffuses over the tip surface with activation energy 20 kcal/mole, and is desorbed therm ally with activation energy 70 ± 7 kcal/mole. It is believed to comprise a layer 2 atoms thick which forms a copper lattice strained to conform to the substrate structure. Copper absorbed upon the type II layer is of type III. It is less strongly bound than type II, being desorbed with activation energy 64±3 kcal/mole and diffusing over the tip surface with activation energy 12kcal/mole. The increase in measured work function from 4.2 to 4.3 eV produced by type III is thought of about 3 atom layers, and addition of further copper produces nuclei which are thought to be crystallites having a true copper lattice structure. The observations reported are believed to be consistent with a description of epitaxial overgrowth given by van der Merwe (1963), and thus contrast with much other work on epitaxial overgrowth of pairs of metals with differing lattice dimensions.

Control of frictional force on coating films of boron nitride–copper complex in ultra high vacuum

2002 ◽  
Vol 405 (1-2) ◽  
pp. 300-303 ◽  
Author(s):  
Masahiro Goto ◽  
Akira Kasahara ◽  
Masahiro Tosa ◽  
Kazuhiro Yoshihara
Keyword(s):  
Boron Nitride ◽  
Copper Complex ◽  
Frictional Force ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Coating Films

Thin Pyrolytic Graphite Films for Electron Microscope Substrates

1971 ◽  
Vol 29 ◽  
pp. 226-227 ◽  
Author(s):  
George H. N. Riddle ◽  
Benjamin M. Siegel
Keyword(s):  
Vacuum Chamber ◽  
Pyrolytic Graphite ◽  
High Vacuum ◽  
Dark Field ◽  
Ultra High Vacuum ◽  
Graphite Substrate ◽  
Nickel Substrate ◽  
Routine Procedure ◽  
Field Electron Microscopy ◽  
Dark Field Electron

A routine procedure for growing very thin graphite substrate films has been developed. The films are grown pyrolytically in an ultra-high vacuum chamber by exposing (111) epitaxial nickel films to carbon monoxide gas. The nickel serves as a catalyst for the disproportionation of CO through the reaction 2C0 → C + CO2. The nickel catalyst is prepared by evaporation onto artificial mica at 400°C and annealing for 1/2 hour at 600°C in vacuum. Exposure of the annealed nickel to 1 torr CO for 3 hours at 500°C results in the growth of very thin continuous graphite films. The graphite is stripped from its nickel substrate in acid and mounted on holey formvar support films for use as specimen substrates.The graphite films, self-supporting over formvar holes up to five microns in diameter, have been studied by bright and dark field electron microscopy, by electron diffraction, and have been shadowed to reveal their topography and thickness. The films consist of individual crystallites typically a micron across with their basal planes parallel to the surface but oriented in different, apparently random directions about the normal to the basal plane.

A High Voltage Electron Microscopy Study of Sub-Oxide Formation in Vanadium

1971 ◽  
Vol 29 ◽  
pp. 212-213
Author(s):  
R. H. Geiss ◽  
R. L. Ladd ◽  
K. R. Lawless
Keyword(s):  
High Vacuum ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Ultra High Vacuum ◽  
Pure Oxygen ◽  
Pressure Oxidation ◽  
High Voltage Electron Microscopy ◽  
Oxidation Study ◽  
Voltage Electron ◽  
Good Agreement

Detailed electron microscope and diffraction studies of the sub-oxides of vanadium have been reported by Cambini and co-workers, and an oxidation study, possibly complicated by carbon and/or nitrogen, has been published by Edington and Smallman. The results reported by these different authors are not in good agreement. For this study, high purity polycrystalline vanadium samples were electrochemically thinned in a dual jet polisher using a solution of 20% H2SO4, 80% CH3OH, and then oxidized in an ion-pumped ultra-high vacuum reactor system using spectroscopically pure oxygen. Samples were oxidized at 350°C and 100μ oxygen pressure for periods of 30,60,90 and 160 minutes. Since our primary interest is in the mechanism of the low pressure oxidation process, the oxidized samples were cooled rapidly and not homogenized. The specimens were then examined in the HVEM at voltages up to 500 kV, the higher voltages being necessary to examine thick sections for which the oxidation behavior was more characteristic of the bulk.

The High Resolution Scanning Transmission Electron Microscope

1974 ◽  
Vol 32 ◽  
pp. 316-317
Author(s):  
A. V. Crewe
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
High Vacuum ◽  
Scanning Transmission Electron Microscope ◽  
Ultra High Vacuum ◽  
Resolving Power ◽  
Imaging Characteristics ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
The Moment

The high resolution STEM is now a fact of life. I think that we have, in the last few years, demonstrated that this instrument is capable of the same resolving power as a CEM but is sufficiently different in its imaging characteristics to offer some real advantages.It seems possible to prove in a quite general way that only a field emission source can give adequate intensity for the highest resolution^ and at the moment this means operating at ultra high vacuum levels. Our experience, however, is that neither the source nor the vacuum are difficult to manage and indeed are simpler than many other systems and substantially trouble-free.

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