Solid phase equilibria in the Au-Ga-As, Au-Ga-Sb, Au-In-As, and Au-In-Sb ternaries

1986 ◽  
Vol 1 (2) ◽  
pp. 352-360 ◽  
Author(s):  
Tsai C. Thomas ◽  
R. Stanley Williams
Keyword(s):  
Gas Phase ◽  
Intermetallic Compounds ◽  
Small Volume ◽  
Solid Phase ◽  
Compound Semiconductors ◽  
The Other ◽  
Group V ◽  
X Ray ◽  
Group Iii ◽  
Pseudobinary Systems

The Au-Ga-As, Au-Ga-Sb, Au-In-As, and Au-In-Sb ternaries were surveyed using x-ray powder diffraction to determine which metallic phases exist at equilibrium with the III-V compound semiconductors. In closed, small-volume systems (i.e., formation of gas-phase products was prevented), Au does not react with GaAs but does react with the other III-V's investigated to produce Au-group III intermetallic compounds and another solid phase containing the group V element. However, each semiconductor formed pseudobinary systems with at least two different intermetallic compounds. The bulk phase diagrams determined in this study provide frameworks within which much of the experimental data in the literature concerning the products of reactions at Au/III-V interfaces can be understood.

Role Of The Fibrinolytic System In Renal Transplantation

1981 ◽  
Author(s):  
P Glas-Greenwalt ◽  
M H Goldman
Keyword(s):  
Renal Transplantation ◽  
Endothelial Damage ◽  
Fibrinolytic System ◽  
The Other ◽  
Group Vi ◽  
Significant Drop ◽  
Group V ◽  
Group Iii ◽  
Group I ◽  
Before And After

To determine the importance of the fibrinolytic system in renal transplantation on the one hand, and to establish a correlation between possible endothelial damage due to treatment of the renal graft and fibrinolytic parameters on the other, dogs were divided in six groups. Group I dogs were subjected to anesthesia only. Group II was sham operated. In group III, kidneys were perfused with the supernatant of either autologous or homologous cryo-precipitated plasma, and in group IV with albumin. In group V kidneys were cold stored. This was followed by autotransplantation. In group VI kidneys were perfused with albumin and allografted. Before and after transplantation, total plasma plasminogen (pro) activator activities in systemic and renal circulations were measured on fibrin plates after the addition of dextran sulfate and flufenamate to euglobulin fractions. Vascular activator (VA) was measured by adding Cl-inactivator. There was no marked difference between groups III, IV and VI. In comparing, however, group V with any of the perfused groups, an overall higher fibrinolytic activity was recorded both for intrinsic activators (p<.001) and VA (p<.001). in group I a significant drop in both activities (p<.01 -<.02) could be directly related to the duration of anesthesia with recovery within 24 hours. This pattern, though highly accentuated, revealed itself in all the other groups studied, with VA temporarily reaching zero-levels in the renal circulation in group VI. This data indicates the participation of the fibrinolytic system, in particular of the VA, in determining the fate of renal grafts.

Group III Metal Clusters on (001) III-V Compound Semiconductors

1993 ◽  
Vol 317 ◽  
Author(s):  
S. Puddephatt ◽  
T.D. Lowes
Keyword(s):  
Thermal Decomposition ◽  
Metal Clusters ◽  
Compound Semiconductors ◽  
Compound Semiconductor ◽  
Knudsen Cell ◽  
Semiconductor Substrate ◽  
Significant Cluster ◽  
Group V ◽  
Group Iii ◽  
Excess Concentration

ABSTRACTThe interaction of group III Metal clusters with the underlying III-V compound semiconductor substrate is examined. Specifically, both In and Ga on InP and GaAs (001) are discussed. Two Methods of obtaining an excess concentration of the group III Metal are treated: thermal decomposition in UHV where preferential group V dissociation and vaporization leaves a supersaturation of metal and Knudsen cell deposition in an MBE system. It is shown that the resulting morphologies for all cases are attributable to significant cluster/substrate interactions.

Tris [(trimethylsilyl)oxy] antimony

1994 ◽  
Vol 49 (7) ◽  
pp. 855-858 ◽  
Author(s):  
Michael Baier ◽  
Klaus Angermaier ◽  
Hubert Schmidbaur
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Gas Phase ◽  
Structure Determination ◽  
Spectroscopic Data ◽  
Mass Spectrometric ◽  
Unit Cell ◽  
The Other ◽  
X Ray ◽  
Trigonal Bipyramidal

Abstract Tris[(trimethylsilyl)oxy]antimony (Sb(OSiMe3)3, 1) has been prepared from SbCl3 and 3 equiv. of LiOSiMe3 in diethylether. According to mass spectrometric and NMR spectroscopic data, 1 appears to be a monomer in solution and in the gas phase. Dimerisation occurs, however, in the solid state as verified by an X-ray crystal structure determination. The unit cell contains three crystallographically independent monomers, two of which form one type of dimer, while the other is part of a centrosymmetrical dimer. In both types of dimers two Sb atoms are connected via two OSiMe3 groups to form distorted Sb2O2-squares. Together with the remaining 4 OSiMe3 groups and the two stereochemically active lone pairs, each Sb exhibits a trigonal bipyramidal coordination.

Numerical Investigation of Pulsed Chemical Vapor Deposition of Aluminum Nitride to Reduce Particle Formation

2011 ◽  
Author(s):  
Derek Endres ◽  
Sandip Mazumder
Keyword(s):  
Gas Phase ◽  
Direct Contact ◽  
Gas Flow ◽  
Film Growth ◽  
Chemical Vapor ◽  
Particle Formation ◽  
Group V ◽  
Flow Rates ◽  
Group Iii ◽  
Reactor Pressure

Particles of aluminum nitride (AlN) have been observed to form during epitaxial growth of AlN films by metal organic chemical vapor deposition (MOCVD). Particle formation is undesirable because particles do not contribute to the film growth, and are detrimental to the hydraulic system of the reactor. It is believed that particle formation is triggered by adducts that are formed when the group-III precursor, namely tri-methyl-aluminum (TMAl), and the group-V precursor, namely ammonia (NH3), come in direct contact in the gas-phase. Thus, one way to eliminate particle formation is to prevent the group-III and the group-V precursors from coming in direct contact at all in the gas-phase. In this article, pulsing of TMAl and NH3 is numerically investigated as a means to reduce AlN particle formation. The investigations are conducted using computational fluid dynamics (CFD) analysis with the inclusion of detailed chemical reaction mechanisms both in the gas-phase and at the surface. The CFD code is first validated for steady-state (non-pulsed) MOCVD of AlN against published data. Subsequently, it is exercised for pulsed MOCVD with various pulse widths, precursor gas flow rates, wafer temperature, and reactor pressure. It is found that in order to significantly reduce particle formation, the group-III and group-V precursors need to be separated by a carrier gas pulse, and the carrier gas pulse should be at least 5–6 times as long as the precursor gas pulses. The studies also reveal that with the same time-averaged precursor gas flow rates as steady injection (non-pulsed) conditions, pulsed MOCVD can result in higher film growth rates because the precursors are incorporated into the film, rather than being wasted as particles. The improvement in growth rate was noted for both horizontal and vertical reactors, and was found to be most pronounced for intermediate wafer temperature and intermediate reactor pressure.

MOVPE GaN Gas-Phase Chemistry for Reactor Design and Optimization

1996 ◽  
Vol 449 ◽  
Author(s):  
S. A. Safvi ◽  
J. M. Redwing ◽  
A. Thon ◽  
J. S. Flynn ◽  
M. A. Tischler ◽  
...  
Keyword(s):  
Growth Rate ◽  
Gas Phase ◽  
Growth Rates ◽  
Operating Conditions ◽  
Gas Phase Reactions ◽  
Group V ◽  
Group Iii ◽  
Design And Optimization ◽  
Gas Phase Chemistry ◽  
Phase Chemistry

ABSTRACTThe results of gas phase decomposition studies are used to construct a chemistry model which is compared to data obtained from an experimental MOVPE reactor. A flow tube reactor is used to study gas phase reactions between trimethylgallium (TMG) and ammonia at high temperatures, characteristic to the metalorganic vapor phase epitaxy (MOVPE) of GaN. Experiments were performed to determine the effect of the mixing of the Group III precursors and Group V precursors on the growth rate, growth uniformity and film properties. Growth rates are predicted for simple reaction mechanisms and compared to those obtained experimentally. Quantification of the loss of reacting species due to oligmerization is made based on experimentally observed growth rates. The model is used to obtain trends in growth rate and uniformity with the purpose of moving towards better operating conditions.

Effect of Growth Parameters and Local Gas-Phase Concentrations on the Uniformity and Material Properties of GaN/Sapphire Grown by Hydride Vapor-Phase Epitaxy

1996 ◽  
Vol 449 ◽  
Author(s):  
S. A. Safvi ◽  
N. R. Perkins ◽  
M. N. Horton ◽  
T. F. Kuech
Keyword(s):  
Gas Phase ◽  
Vapor Phase ◽  
Growth Parameters ◽  
Ammonia Concentration ◽  
Vapor Phase Epitaxy ◽  
Operating Conditions ◽  
Hydride Vapor Phase Epitaxy ◽  
Crystal Quality ◽  
Group V ◽  
Group Iii

ABSTRACTThe effects of flowrate variation and geometry on the growth rate, growth uniformity and crystal quality were investigated in a horizontal Gallium Nitride vapor phase epitaxy reactor. To better understand the effects of these parameters, numerical model predictions are compared to experimentally observed values. Parasitic gas phase reactions between group III and group V sources and deposition of material on the wall are shown to lead to reduced overall growth rates and may be responsible for inferior crystal quality. A low ammonia concentration is correlated with the deposition of polycrystalline films. A low V/III ratio and an ammonia concentration lead to poor crystalline quality and increased yellow luminescence. An optimum HVPE growth process requires selection of reactor geometry and operating conditions to minimize these parasitic reactions and wall deposition while providing a uniform reactant distribution across the substrate.

The structure of chloromethyl thiocyanate, CH2ClSCN, in gas and crystalline phases

2015 ◽  
Vol 17 (24) ◽  
pp. 15805-15812 ◽  
Author(s):  
Y. Berrueta Martínez ◽  
L. S. Rodríguez Pirani ◽  
M. F. Erben ◽  
C. G. Reuter ◽  
Y. V. Vishnevskiy ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Low Temperature ◽  
Single Crystal ◽  
Gas Phase ◽  
Solid Phase ◽  
Gas Electron Diffraction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Conformational Properties

The structural and conformational properties of chloromethyl thiocyanate, CH2ClSCN, were studied in the solid phase and in the gas phase usingin situlow-temperature single-crystal X-ray diffraction experiments (XRD) and gas electron diffraction (GED), respectively.

scholarly journals MOVPE Growth and Structural Characterization of AlxGa1−xN

1997 ◽  
Vol 2 ◽  
Author(s):  
S. Ruffenach-Clur ◽  
Olivier Briot ◽  
Bernard Gil ◽  
Roger-Louis Aulombard ◽  
J. L. Rouviere
Keyword(s):  
Gas Phase ◽  
Molar Ratio ◽  
Structural Quality ◽  
X Rays ◽  
X Ray Diffraction ◽  
Directional Growth ◽  
X Ray ◽  
Group Iii ◽  
Al Content ◽  
Aln Buffer

The ternary alloy GaAlN has been grown by low pressure MOVPE (76 Torr) using triethylgallium, trimetylaluminum and ammonia as precursors. The alloy layers were grown on (0001) sapphire substrates using a low temperature AlN buffer. All layers were deposited at a growth temperature of 980°C. Only the aluminum/gallium ratio in the gas phase was changed, keeping the total group III molar flow rate and V/III molar ratio constant.The aluminum incorporation versus gas phase composition was determined experimentally, using energy dispersive analysis of X-rays (EDAX), and X-ray diffraction. We propose a model, taking into account kinetically limited mass transport of group III species in the gas phase, which describes well the data.The structural quality of the layers was investigated using X-ray diffraction and TEM experiments.A degradation of the materials quality is observed with increasing Al content. In this case, growth originate on the buffer grains facets resulting in a “ two directional » growth. This phenomenon, being markedly enhanced when increasing the Al content will be detailed in this paper.

Sign in / Sign up

Export Citation Format

Share Document