Chemical Reactions at the in Vacuo Au/Inp Interface

1986 ◽  
Vol 83 ◽  
Author(s):  
R. Stanley Williams ◽  
C. Thomas Tsai ◽  
Eun-Hee Cirlin
Keyword(s):  
Intermetallic Compound ◽  
Atmospheric Pressure ◽  
High Vacuum ◽  
Thermodynamic System ◽  
External Pressure ◽  
Ultra High Vacuum ◽  
Reaction Products ◽  
Inp Substrate ◽  
Major Reaction ◽  
Closed Thermodynamic System

ABSTRACTThe reaction between a Au film and an Inp substrate occurs much more readily in vacuo than under an external pressure of an inert ga. At atmospheric pressure, the compounds Au2P3 and the γ intermetallic compound (at times designated Au7In3, Au9In4, or Au2In) are formed at 450 °C and remain fairly stable even when annealed at 500°C for hours. Under ultra-high vacuum conditions, phosphorous readily escapes from the film when a sample is annealed at 300°C for 15 minutes, and the major reaction products are the ψ phase (Au3In2) and another intermetallic compound that is probably AuIn. The presence of an inert gas creates a kinetic barrier for the escape of phosphorous from the surface, and thus Au/InP behaves more like a closed thermodynamic system under pressure than in a vacuum.

scholarly journals The Determination of Interfacial Structure and Phase Transitions in Al/Cu and Al/Ni Interfaces by Means of Surface Extended X-Ray Absorption Fine Structure

1991 ◽  
Vol 238 ◽  
Author(s):  
E. V. Barrera ◽  
S. M. Heald
Keyword(s):  
Fine Structure ◽  
Room Temperature ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Interfacial Structure ◽  
Reaction Products ◽  
X Ray ◽  
Absorption Fine ◽  
Reaction Zones ◽  
X Ray Absorption

ABSTRACTSurface extended x-ray absorption fine structure (SEXAFS) was used to investigate the interfacial conditions of Al/Cu and Al/Ni shallow buried interfaces. Previous studies using glancing angle extended x-ray absorption fine structure, x-ray reflectivity, photoemission, and SEXAFS produced conflicting results as to whether or not the interfaces between Al and Cu and Al and Ni were reacted upon room temperature deposition. In this study polycrystalline bilayers of Al/Cu and Al/Ni and trilayers of Al/Cu/Al and Al/Ni/Al were deposited on tantalum foil at room temperature in ultra high vacuum and analyzed to evaluate the reactivity of these systems on a nanometer scale. It became overwhelming apparent that the interfacial phase reactions were a function of the vacuum conditions. Samples deposited with the optimum vacuum conditions showed reaction products upon deposition at room temperature which were characterized by comparisons to standards and by least squares fitting to be CuAl2 and NiAl3 respectively. The results of this study showed that the reacted zone thicknesses were readily dependent on the deposition parameters. For both Al on Cu and Al on Ni as well as the metal on Al conditions 10A reaction zones were observed. These reaction zones were smaller than that observed for bilayers of Al on Cu (30Å) and Al on Ni (60Å) where deposition rates were much higher and samples were much thicker. The reaction species are evident by SEXAFS, where the previous photoemission studies only indicated that changes had occurred. Improved vacuum conditions as compared to the earlier experiments is primarily the reason reactions on deposition were seen in this study as compared to the earlier SEXAFS studies.

Oxidation of α-Pinene with Hydrogen Peroxide Catalyzed by VO(OAc)2

2012 ◽  
Vol 550-553 ◽  
pp. 179-182
Author(s):  
Min Zheng ◽  
Jian Sheng Tang ◽  
Du Lin Yin ◽  
Qiong Xu
Keyword(s):  
Hydrogen Peroxide ◽  
Catalytic Activity ◽  
Atmospheric Pressure ◽  
Product Selectivity ◽  
Reaction Products ◽  
Campholenic Aldehyde ◽  
Ethylene Glycol Dimethyl Ether ◽  
Major Reaction ◽  
Catalyst Dosage ◽  
Influence Of Solvent

The oxidation of α-pinene with hydrogen peroxide, at 40°C and atmospheric pressure, using ethylene glycol dimethyl ether as solvent was carried out in the presence of VO(OAc)2. The influence of solvent, reaction temperature and catalyst dosage on catalytic activity and product selectivity was studied. The major reaction products were verbenon (45.9% selectivity at 82.9% conversion). Formation of campholenic aldehyde, myrtenal, verbenol and epoxypinane was also observed.

XPS and AES Study of Oxygen Interaction on the Surface of the ZrNi Intermetallic Compound

2012 ◽  
Vol 445 ◽  
pp. 709-713 ◽  
Author(s):  
A. Roustila ◽  
A. Rabehi ◽  
M. Souici ◽  
J. Chene
Keyword(s):  
Intermetallic Compound ◽  
Photoelectron Spectroscopy ◽  
High Vacuum ◽  
Chemical Properties ◽  
Binding Energies ◽  
Ultra High Vacuum ◽  
Ion Sputtering ◽  
Xps Spectra ◽  
Preferential Sputtering ◽  
Application Fields

ZrNi intermetallic compound is used in several application fields due to its very favorable characteristics for the storage of hydrogen. The hydrogen reactions are important, it is vital to examine the evolution of physico-chemical properties at the surface. X-ray photoelectron spectroscopy, is used to follow the evolution of electronic properties of ZrNi versus the ion sputtering in ultra high vacuum in the range 300-600°C. Morever, the evolution of species concentrations at the surface of ZrNi in the range 100-700°C is followed by means of Auger electron spectroscopy. The present results show that temperature and ion sputtering favor significant changes in surface properties of ZrNi. In situ annealing of ZrNi favors the oxygen decontamination associated with segregation of zirconium metal on the surface. The values of binding energies deduced from the reconstruction of XPS spectra, allowed the identification of species present at the surface. The results indicate that nickel is not contaminated and all the obtained sub-oxides are related to bonding states of oxygen with zirconium (Zr2O, ZrO, ZrO2and Zr2O3). The ion sputtering of the surface of ZrNi causes preferential sputtering phenomenon. The later results from the removal of surface layers and from the appearance of zirconium oxide layers initially present on the surface. The results obtained by AES show the segregation of impurities (oxygen and carbon) and of zirconium on the surface of ZrNi. AES observations of Zr segregation start to be important above 300°C and this is in agreement with XPS analysis showing a Zr enrichment of the surface of ZrNi.

scholarly journals Low loss hollow optical-waveguide connection from atmospheric pressure to ultra-high vacuum

2013 ◽  
Vol 103 (26) ◽  
pp. 261115 ◽  
Author(s):  
A. Ermolov ◽  
K. F. Mak ◽  
F. Tani ◽  
P. Hölzer ◽  
J. C. Travers ◽  
...  
Keyword(s):  
Optical Waveguide ◽  
Atmospheric Pressure ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Low Loss

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.

Structure of Palladium Single-Crystal Films Prepared by Flash Evaporation onto (001) NaCl Substrates

1970 ◽  
Vol 28 ◽  
pp. 456-457
Author(s):  
L. E. Murr ◽  
G. Wong
Keyword(s):  
Single Crystal ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
High Rate ◽  
Flash Evaporation ◽  
Optimum Load ◽  
Single Crystal Films ◽  
Crystal Films ◽  
A Current

Palladium single-crystal films have been prepared by Matthews in ultra-high vacuum by evaporation onto (001) NaCl substrates cleaved in-situ, and maintained at ∼ 350° C. Murr has also produced large-grained and single-crystal Pd films by high-rate evaporation onto (001) NaCl air-cleaved substrates at 350°C. In the present work, very large (∼ 3cm2), continuous single-crystal films of Pd have been prepared by flash evaporation onto air-cleaved (001) NaCl substrates at temperatures at or below 250°C. Evaporation rates estimated to be ≧ 2000 Å/sec, were obtained by effectively short-circuiting 1 mil tungsten evaporation boats in a self-regulating system which maintained an optimum load current of approximately 90 amperes; corresponding to a current density through the boat of ∼ 4 × 104 amperes/cm2.

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