Subnanophase coatings as new type low-dimensional nanomaterials: ultra-high-vacuum synthesis, properties and application

A classification of low-dimensional nanomaterials is given, and a new type of these nanomaterials – subnanophase coatings is proposed. Experimental results on the formation of a wetting layer of a transition metal on a silicon substrate by physical deposition in vacuum and results of this layer identification by the EELS method are given. Based on these results, a new approach to the formation of subnanophase coatings has been proposed by creation of a interface stresses which structuring WL. The possible properties and application prospects of subnanophase coatings are considered.

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Effect of H Adsorption on the Magnetic Properties of an Fe Island on a W(110) Surface

10.26434/chemrxiv.9706040.v1 ◽

2019 ◽

Author(s):

Marko Melander ◽

Hannes Jonsson

Keyword(s):

Magnetic Properties ◽

Data Storage ◽

Density Functional ◽

Hydrogen Adsorption ◽

High Vacuum ◽

Ultra High Vacuum ◽

Generalized Gradient ◽

Functional Theory ◽

Low Dimensional ◽

Low Dimensional Materials

<p>Low-dimensional materials, such as ultrathin films, nanoislands and wires, are actively being researched due to their interesting magnetic properties and possible technological applications for example in high density data storage. Results of calculations of an Fe nanoisland on a W(110) support are presented here with particular focus on the effect of hydrogen adsorption on its magnetic properties. This is an important consideration since hydrogen is present even under ultra-high vacuum conditions. The calculations are based on density functional theory within the generalized gradient approximation. The adsorption of H atoms is found to strongly decrease the magnetic moment of the Fe atoms they are bound to, down to less than a half in some cases as compared with the clean Fe island. The results show that it may be important to take the presence of hydrogen into account in measurements of magnetic properties of nanoislands.</p>

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MBE FABRICATION OF GaAs/AlGaAs LOW-DIMENSIONAL STRUCTURES ON IN SITU PATTERNED GaAs SUBSTRATES

International Journal of Modern Physics B ◽

10.1142/s0217979296001975 ◽

1996 ◽

Vol 10 (27) ◽

pp. 3637-3648

Author(s):

TOMONORI ISHIKAWA ◽

MÁXIMO LÓPEZ

Keyword(s):

High Vacuum ◽

Processing Technique ◽

Ultra High Vacuum ◽

Surface Oxide Layer ◽

Gaas Substrates ◽

Mask Material ◽

Gaas Buffer Layer ◽

Novel Processing ◽

Low Dimensional

We have developed a novel processing technique, conducted entirely under an ultra-high vacuum environment, to pattern GaAs substrates on which GaAs/AlGaAs low-dimensional structures are subsequently regrown. In this technique, called in situ electron-beam (EB) lithography, a thin surface-oxide-layer is selectively formed by EB-stimulated oxidation under a controlled oxygen atmosphere. This is used as a mask material to define patterned mesas by Cl 2 gas etching. Subsequently, the initial mesa size is reduced by the regrowth of a GaAs buffer layer; finally, low-dimensional structures, such as quantum-wire or -box structures, are formed on the top of the mesas by the growth of a quantum well. This in situ technique is advantageous for the fabrication of arbitrarily designed low-dimensional structures with high quality.

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Effect of H Adsorption on the Magnetic Properties of an Fe Island on a W(110) Surface

10.26434/chemrxiv.9706040 ◽

2019 ◽

Author(s):

Marko Melander ◽

Hannes Jonsson

Keyword(s):

Magnetic Properties ◽

Data Storage ◽

Density Functional ◽

Hydrogen Adsorption ◽

High Vacuum ◽

Ultra High Vacuum ◽

Generalized Gradient ◽

Functional Theory ◽

Low Dimensional ◽

Low Dimensional Materials

<p>Low-dimensional materials, such as ultrathin films, nanoislands and wires, are actively being researched due to their interesting magnetic properties and possible technological applications for example in high density data storage. Results of calculations of an Fe nanoisland on a W(110) support are presented here with particular focus on the effect of hydrogen adsorption on its magnetic properties. This is an important consideration since hydrogen is present even under ultra-high vacuum conditions. The calculations are based on density functional theory within the generalized gradient approximation. The adsorption of H atoms is found to strongly decrease the magnetic moment of the Fe atoms they are bound to, down to less than a half in some cases as compared with the clean Fe island. The results show that it may be important to take the presence of hydrogen into account in measurements of magnetic properties of nanoislands.</p>

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The Scanning Photoelectron Microscope : A Novel Tool in Surface Science

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100181531 ◽

1990 ◽

Vol 48 (1) ◽

pp. 556-557

Author(s):

A. von Oertzen ◽

H.H. Rotermund ◽

S. Jakubith ◽

S. Kubala ◽

G. Ertl

Keyword(s):

Surface Science ◽

Uv Light ◽

High Vacuum ◽

Ultra High Vacuum ◽

Electron Optics ◽

Experimental Setup ◽

Photoelectron Emission ◽

Small Aperture ◽

New Approach ◽

Work Functions

Photoelectron microscopes using electron optics had been built long before. Until recently these microscopes were not widely used in surface science due to unsufficient vacuum conditions as well as weak image intensifying devices. In this paper we will present a new approach to photoelectron microscopy, the Scanning Photoelectron Microscope (SPM).Photoelectron emission will occur as soon as the photon energy is higher than the work function on the illuminated area. Since work functions never exceed 6.5 eV, ultraviolet (UV) light with λ ≥ 190 nm will be appropriate. This kind of radiation is a very gentle probe, even for sensitive adlayers.The experimental setup is shown schematicaly in Fig. 1. A UV light optics outside the ultra high vacuum (UHV) system focusses the actual 30 W Deuterium discharge lamp through a grid monochromator onto a small aperture (50 to 400 microns). The aperture hole is projected with a reflecting microscope objective (Schwarzschild type) onto the surface of the sample yielding a lateral resolution of about 3 microns.

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A two-dimensional crystal formed by pentamers on Au(111)

Chemical Communications ◽

10.1039/c9cc01658a ◽

2019 ◽

Vol 55 (38) ◽

pp. 5427-5430 ◽

Cited By ~ 1

Author(s):

Chenyang Yuan ◽

Na Xue ◽

Xue Zhang ◽

Yajie Zhang ◽

Na Li ◽

...

Keyword(s):

Low Temperature ◽

High Vacuum ◽

Ultra High Vacuum ◽

Two Dimensional ◽

Scanning Tunnelling Microscope ◽

Scanning Tunnelling ◽

New Type ◽

Temperature Scanning ◽

Dimensional Crystal

A new type of two-dimensional crystal comprising supramolecular pentamers on Au(111) is studied using an ultra-high vacuum low-temperature scanning tunnelling microscope.

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Nanomechanics Using an Ultra-Small Amplitude AFM

MRS Proceedings ◽

10.1557/proc-649-q9.2 ◽

2000 ◽

Vol 649 ◽

Cited By ~ 2

Author(s):

Peter M. Hoffmann ◽

Steve Jeffery ◽

Ahmet Oral ◽

Ralph A. Grimble ◽

H. özgür Özer ◽

...

Keyword(s):

Mechanical Response ◽

High Vacuum ◽

Interaction Force ◽

Ultra High Vacuum ◽

Atomic Scale ◽

Resonance Amplitude ◽

Molecular Ordering ◽

Atomic Relaxation ◽

New Type ◽

Sample Separation

ABSTRACTA new type of AFM is presented which allows for direct measurements of nanomechanical properties in ultra-high vacuum and liquid environments. The AFM is also capable of atomic-scale imaging of force gradients. This is achieved by vibrating a stiff lever at very small amplitudes of less than 1 Å (peak-to-peak) at a sub-resonance amplitude. This linearizes the measurement and makes the interpretation of the data straight-forward. At the atomic scale, interaction force gradients are measured which are consistent with the observation of single atomic bonds. Also, atomic scale damping is observed which rapidly rises with the tip-sample separation. A mechanism is proposed to explain this damping in terms of atomic relaxation in the tip. We also present recent results in water where we were able to measure the mechanical response due to the molecular ordering of water close to an atomically flat surface.

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Thin Pyrolytic Graphite Films for Electron Microscope Substrates

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100065183 ◽

1971 ◽

Vol 29 ◽

pp. 226-227 ◽

Cited By ~ 1

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.

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

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100065110 ◽

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.

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The High Resolution Scanning Transmission Electron Microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100051591 ◽

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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