Quality of surface and underlying glass layer influence on sensitivity of multialkaline photocathodes grown in ultra-high vacuum (UHV) chambers

2005 ◽  
Author(s):  
V. Loktionov ◽  
I. Nesterov
Keyword(s):  
High Vacuum ◽  
Ultra High Vacuum ◽  
Glass Layer

Microstructure of FCC/BCC Metal Multilayers

1989 ◽  
Vol 160 ◽  
Author(s):  
Nigel M. Jennett ◽  
D.J. Dingley ◽  
Y. Ando
Keyword(s):  
Substrate Temperature ◽  
Magnetic Moment ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Bcc Lattice ◽  
A Value ◽  
Fcc Lattice ◽  
Temperature Window ◽  
Backing Layer

AbstractBilayers of Cu/Fe and Cu/V and multilayers of Ni/Fe have been grown under high vacuum and ultra high vacuum conditions respectively with [111] epitaxy. Multilayer layer thicknesses ranged from 3 monolayers to 15 monolayers per layer. Improved epitaxy of the UHV growth was, we believe, due to the better vacuum although perfect material could only be obtained for growth within a narrow and shifting substrate temperature ‘window’. Possible shortfall in the quality of the Cu backing layer epitaxy was averted by a 2hr anneal at 425°C.In the Fe/Ni multilayers the Fe was observed to adopt the FCC lattice rather than the equilibrium BCC lattice for layer thicknesses less than 10 monolayers. This change of structure coincided with a reduction in sample magnetic moment per volume attributed to a collapse of the Fe moment to a value 7 times less than bulk.

Are major instrumental developments in TEM still to be Expected?

1988 ◽  
Vol 46 ◽  
pp. 646-647
Author(s):  
K.D. van der Mast ◽  
A.J. Koster
Keyword(s):  
Surface Science ◽  
New Technologies ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Analytical Instrument ◽  
Electron Efficiency ◽  
In Situ Experiments ◽  
New Ideas

In general instrumental developments are caused either by new application demands or by the availability of new technologies. If we investigate the trends in application demands, some predictions can be made safely: More and more the TEM will be used as an analytical instrument. The number of desired signals (detectors) will increase and the quality of the signals must be improved in terms of noise and electron efficiency. Examples are parallel collection EELS and Auger detectors (Kruit and Venables, 1988).The first experiments on coincidence techniques are also promising (Kruit et al, 1984) and exciting new ideas are investigated today. Besides this, another area of applications will probably become more important: surface science in situ experiments. Especially for this type of experiments it is difficult to transfer the specimen to another system without spoiling the experiment. So these applications will lead to an ultra high vacuum specimen environment - constructed in a way that many accessories necessary for surface experiments can be added: Ion guns, preparation chamber, knudsen cells etc.

The growth of gallium arsenide on Si(100) by molecular-beam epitaxy

1987 ◽  
Vol 65 (8) ◽  
pp. 904-908 ◽  
Author(s):  
W. T. Moore ◽  
R. L. S. Devine ◽  
P. Maigné ◽  
D. C. Houghton ◽  
J.-M. Baribeau ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
High Vacuum ◽  
Group Iv ◽  
Ultra High Vacuum ◽  
Buffer Layers ◽  
Threading Dislocations ◽  
X Ray Diffraction ◽  
X Ray

The growth of GaAs on Si(100) directly and with Ge buffer layers has been carried out sequentially under ultra high vacuum conditions in a double-ended III–V and group IV molecular beam epitaxy system. These heterostructures were examined by cross-section transverse emission microscopy, Rutherford backscattering, X-ray diffraction, and photoluminescence spectroscopy.Dislocation densities were observed to be high [Formula: see text] near both the GaAs–Si and the Ge–Si interfaces and to decrease to ~5 × 108 cm−2 a few micrometres from these interfaces. No dislocations were observed to originate at the GaAs–Ge interface, but the threading dislocations existing in the Ge buffer layer were found to propagate across this interface without significant deviation. The crystalline quality of the GaAs grown on Ge buffer layers was comparable with that grown on Si directly. However, GaAs has not yet been grown on the highest quality Ge buffer layers obtainable.

Device Quality of Hydrogen Plasma Cleaning for Silicon Molecular Beam Epitaxy

1995 ◽  
Vol 386 ◽  
Author(s):  
W. Hansch ◽  
I. Eisele ◽  
H. Kibbel ◽  
U. KÖnig
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Hydrogen Plasma ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Plasma Cleaning ◽  
Chemical Cleaning ◽  
Cleaning Procedures ◽  
Desorption Step

ABSTRACTDifferent substrate cleaning procedures were used before fabrication of pin diodes by silicon molecular beam epitaxy (MBE). We investigated the quality of these diodes in order to demonstrate the superior quality of a low energy plasma cleaning in an ultra-high vacuum ( UHV). This plasma cleaning by hydrogen makes a wet-chemical cleaning or a high-temperature desorption step unnecessary. Moreover, the plasma-cleaned substrates are so strongly hydrogen passivated, that they can be transported through air and processed in another MBE chamber without any additional cleaning steps.

Enhanced quality of epitaxial AlN thin films on 6H–SiC by ultra-high-vacuum ion-assisted reactive dc magnetron sputter deposition

2000 ◽  
Vol 76 (2) ◽  
pp. 170-172 ◽  
Author(s):  
S. Tungasmita ◽  
J. Birch ◽  
P. O. Å. Persson ◽  
K. Järrendahl ◽  
L. Hultman
Keyword(s):  
Thin Films ◽  
High Vacuum ◽  
Sputter Deposition ◽  
Ultra High Vacuum ◽  
Magnetron Sputter Deposition ◽  
Magnetron Sputter

Surface Morphology of Si1−x−y GexCy Epitaxial Films Deposited by Low Temperature UHV-CVD

1996 ◽  
Vol 440 ◽  
Author(s):  
S. John ◽  
E. J. Quinones ◽  
B. Ferguson ◽  
S. K. Ray ◽  
C. B. Mullins ◽  
...  
Keyword(s):  
Surface Morphology ◽  
Carbon Concentration ◽  
Critical Thickness ◽  
High Vacuum ◽  
Three Dimensional ◽  
Chemical Vapor ◽  
Epitaxial Films ◽  
Ultra High Vacuum ◽  
Epitaxial Thin Films

AbstractSi1−x−y GexCy epitaxial films offer wider control of strain and bandgap. In such films the morphology is an important indication of the crystalline quality of the material. We report on the morphology of Si1−x−y GexCy epitaxial thin films deposited by Ultra High Vacuum Chemical Vapor Deposition at a temperature of 550° C and deposition pressures ranging from 1 to 10 mTorr. The precursors used were Si2H6, GeH4 and CH3SiH3. Germanium mole fractions ranging from 0% to 40% were studied with carbon concentrations varying from 2×1019 to 2×1021 atoms/cm3. AFM analysis of the surface indicates that the roughness is a function of both the carbon concentration and the film thickness. For high germanium concentrations with thickness beyond the critical thickness (of Si1−xGex), carbon is found to decrease the surface roughness of the film. Thus the surface morphology confirms the strain compensation provided by carbon which is also observed using XRD. For films below the critical thickness, as the carbon concentration is increased, three dimensional islanding is observed by RHEED and AFM, degrading the epitaxial quality of the material.

Intermixing in Ge/Si(001) Islands: Elemental Content and Structure

2001 ◽  
Vol 696 ◽  
Author(s):  
A. Eshed ◽  
J. Zhu ◽  
J. Yan ◽  
R. Beserman ◽  
A. H. Weiss
Keyword(s):  
Self Assembly ◽  
Molecular Beam ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Crystalline Quality ◽  
Elemental Content ◽  
High Crystalline Quality ◽  
Micro Raman Spectroscopy ◽  
Atomic Force

AbstractWe have investigated the shapes, thickness, density, composition, and quality of Ge/Si(001) islands grown by solid source molecular beam epitaxy in ultra high vacuum conditions. Nano crystals were formed by means of the Stranski-Krastanow “self assembly” growth mechanism. 5 nm of Ge were deposited on Si(001) substrates, at 500 °C, with deposition rate of 0.5 nm/min. Atomic force microscope measurements reveal islands of various sizes, ranging from 60 nm to 700 nm in diameter. Islands' density found to be correlated with their sizes, with denser areas containing mostly islands of the smaller sizes. Micro Raman spectroscopy, with probing spot of about 0.7 µm diameter, has been used to study the composition, thickness and crystalline quality of the islands. Data were taken at various points on the sample distinguishing between various islands' types. Combined analysis of Raman spectra and the micrographs reveal low amount of alloying (less than 30%) in all types of islands, with the larger islands showing the more amount of intermixing. High crystalline quality of the layers within the islands suggests negligible amount of dislocations.

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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