Incomplete Solubility in Nitride Alloys

1996 ◽  
Vol 449 ◽  
Author(s):  
I. H. Ho ◽  
G.B. Stringfellow
Keyword(s):  
Experimental Data ◽  
Nearest Neighbor ◽  
Solubility Limit ◽  
Lattice Parameter ◽  
Miscibility Gap ◽  
Recent Experimental Data ◽  
Virtual Crystal Approximation ◽  
Group V ◽  
Group Iii ◽  
Nitride Alloys

ABSTRACTA model based on the valence-force-field (VFF) model has been developed specifically for the calculation of the irascibility gaps in III-V nitride alloys. In the dilute limit, this model allows the relaxation of the atoms on both sublattices. It was found that the energy due to bond stretching and bond bending was lowered and the solubility limit was increased substantially when both sublattices were allowed to relax to distances as large as the sixth nearest neighbor positions. Using this model, the equilibrium mole fraction of N in GaP was calculated to be 6×l0−7 at 700°C. This is slightly higher than the calculated results from the semi-empirical delta lattice parameter (DLP) model. Both the temperature dependence and the absolute values of the calculated solubility agree closely with the experimental data. The solubility is more than three orders of magnitude larger than the result obtained using the VFF model with the group V atom positions given by the virtual crystal approximation, i.e., with relaxation of only the first neighbor bonds. Other nitride systems, such as GaAsN, AlPN, AlAsN, InPN, and InAsN were investigated as well. The equilibrium mole fractions of nitrogen in InP and InAs are the highest, which agrees well with recent experimental data where high N concentrations have been produced in InAsN alloys. Calculations were also performed for the alloy systems with mixing on the group III sublattice that are so important for device applications. Allowing relaxation to the 3rd nearest neighbor gives an In solubility in GaN at 800°C of less than 6%. Again, this is in agreement with the results of the DLP model calculation. This result may partially explain the difficulties experienced with the growth of these alloys. Indeed, evidence of solid immiscibility has recently been reported. A significant miscibility gap was also calculated for the AlInN system, but the AlGaN system is completely miscible.

Thin-Film Cadmium Sulfide/Cadmium Telluride Alloys

1996 ◽  
Vol 426 ◽  
Author(s):  
D. G. Jensen ◽  
B. E. McCandless ◽  
R. W. Birkmire
Keyword(s):  
Heat Treatment ◽  
Equilibrium Phase ◽  
Phase Segregation ◽  
Solubility Limit ◽  
Lattice Parameter ◽  
Parameter Determination ◽  
Miscibility Gap ◽  
X Ray Diffraction ◽  
Segregation Process ◽  
Two Phases

AbstractThin films of CdTel-xSx with bulk atomic compositions, x≡[S]/([S]+[Te]), ranging from 0 to 0.45 were deposited by vacuum co-evaporation of CdTe and CdS with substrate temperatures of 200 and 250°C. X-ray diffraction analysis revealed that films with x < 0.3 were predominately single phase having the zincblende structure. Films with 0.35 < x < 0.45 contained the wurtzite modification. Lattice parameter determination indicated that each phase exists with compositions well within the miscibility gap shown on published equilibrium phase diagrams. The variation of the optical band gap with x was determined by measuring transmission and reflection of the films. Heat treatment at 415°C in the presence of CdC12 caused the films to segregate into two phases consistent with the phase diagram. If the CdCl2 is assumed to only promote the phase segregation process, then the compositions of the two phases after heat treatment may be taken as measurements of the solubility limits of S in CdTe and Te in CdS respectively. The solubility limit of S in CdTe was thus determined to be 5.8% at 415°C which is the temperature used for the common CdC12 treatment of CdTe-based solar cells. An analysis of CdTe/CdS solar cell device structures shows that the atomic composition of alloys created by interdiffusion are consistent with these solubility limits.

scholarly journals MBE Growth of Nitride-Arsenide Materials for long Wavelength Opto-electronics

2000 ◽  
Vol 5 (S1) ◽  
pp. 474-480 ◽  
Author(s):  
Sylvia G. Spruytte ◽  
Christopher W. Coldren ◽  
Ann F. Marshall ◽  
Michael C. Larson ◽  
James S. Harris
Keyword(s):  
Quantum Wells ◽  
Molecular Nitrogen ◽  
Nitrogen Concentration ◽  
Plasma Source ◽  
Lattice Parameter ◽  
Nitrogen Plasma ◽  
Group V ◽  
Mbe Growth ◽  
Group Iii ◽  
Nitrogen Concentrations

Nitride-Arsenide materials were grown by molecular beam epitaxy (MBE) using a radio frequency (rf) nitrogen plasma. The plasma conditions that maximize the amount of atomic nitrogen versus molecular nitrogen were determined using the emission spectrum of the plasma. Under constant plasma source conditions and varying group III flux, the nitrogen concentration in the film is inversely proportional to the group III flux (i. e. the nitrogen sticking coefficient is unity). The relationship between nitrogen concentration in the film and lattice parameter of the film is not linear for nitrogen concentrations above 2.9 mole % GaN, indicating that some nitrogen is incorporated on other locations than the group V lattice sites. For films with these higher nitrogen concentrations, XPS indicates that the nitrogen exists in two configurations: a Gallium-Nitrogen bond and another type of nitrogen complex in which nitrogen is less strongly bonded to Gallium atoms. Annealing removes this nitrogen complex and allows some of the nitrogen to diffuse out of the film. Annealing also improves the crystal quality of GaAsN quantum wells.

scholarly journals An innovative technique for electronic transport model of group-III nitrides

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Anshika Srivastava ◽  
Anshu Saxena ◽  
Praveen K. Saxena ◽  
F. K. Gupta ◽  
Priyanka Shakya ◽  
...  
Keyword(s):  
Density Functional ◽  
Carrier Transport ◽  
Transport Model ◽  
Form Factors ◽  
Experimental Results ◽  
Boltzmann Transport ◽  
Virtual Crystal Approximation ◽  
Group Iii ◽  
Scattering Mechanisms ◽  
Nitride Alloys

Abstract An optimized empirical pseudopotential method (EPM) in conjunction with virtual crystal approximation (VCA) and the compositional disorder effect is used for simulation to extract the electronic material parameters of wurtzite nitride alloys to ensure excellent agreement with the experiments. The proposed direct bandgap results of group-III nitride alloys are also compared with the different density functional theories (DFT) based theoretical results. The model developed in current work, significantly improves the accuracy of calculated band gaps as compared to the ab-initio method based results. The physics of carrier transport in binary and ternary nitride materials is investigated with the help of in-house developed Monte Carlo algorithms for solution of Boltzmann transport equation (BTE) including nonlinear scattering mechanisms. Carrier–carrier scattering mechanisms defined through Coulomb-, piezoelectric-, ionized impurity-, surface roughness-scattering with acoustic and intervalley scatterings, all have been given due consideration in present model. The direct and indirect energy bandgap results have been calibrated with the experimental data and use of symmetric and asymmetric form factors associated with respective materials. The electron mobility results of each binary nitride material have been compared and contrasted with experimental results under appropriate conditions and good agreement has been found between simulated and experimental results.

scholarly journals Measurement and Modeling of Phase Equilibria in Systems Containing Water, Xylose, Furfural, and Acetic Acid

2021 ◽  
Author(s):  
Nadia Galeotti ◽  
Jakob Burger ◽  
Hans Hasse
Keyword(s):  
Experimental Data ◽  
Acetic Acid ◽  
Ternary System ◽  
Phase Equilibria ◽  
Solubility Limit ◽  
Miscibility Gap ◽  
Rich Phase ◽  
Biotechnological Processes ◽  
Solid Liquid ◽  
System Water

Wood hydrolysates obtained in biotechnological processes are typically aqueous solutions that contain, among others, sugars, acetic acid, and furfural. Only little is known on the influence of the sugars on the phase equilibria in those mixtures. Therefore liquid-liquid equilibria (LLE), solid-liquid equilibria (SLE), and solid-liquid-liquid equilibria (SLLE) in the system (water(W) + xylose (X) + furfural (F)) were studied in the present work at 298.15 K and 333.15 K. Additionally, the LLE in the system (W + X + F + acetic acid (AA)) was studied at 298.15 K. The results show that, up to the solubility limit of xylose, adding xylose to mixtures of (W +F) hardly influences the width of the miscibility gap, and that there is practically no xylose in the furfural-rich phase. However, the miscibility gap in the ternary system (W + F + AA) is slightly widened by the addition of xylose. The experimental data on the phase equilibria from the present work were described using the NRTL model. The model describes the experimental data well.

The Quantitative Ultrastructure of the Heart Muscle of Japanese Quail by Hypergravitation, Hypodynamy and Combination

1990 ◽  
Vol 48 (3) ◽  
pp. 188-189
Author(s):  
Anton Bózner ◽  
Mikuláš Gažo ◽  
Jozef Dostál
Keyword(s):  
Japanese Quail ◽  
Heart Muscle ◽  
Relative Size ◽  
Combination Group ◽  
Control Group ◽  
Group V ◽  
Group Iii ◽  
Space Flights ◽  
Group I ◽  
Quantitative Ultrastructure

It is anticipated that Japanese quail /Coturnix coturnix japonica/ will provide animal proteins in long term space flights. Consequently this species of birds is of research interest of international space program INTERCOSMOS. In the year 1987 we reported on an experiment /2/ in which the effect of chronic acceleration of 2 G hypergravitation, the hypodynamy and the simultaneous effect of chronic acceleration and the location in the centre of the turntable of the centrifuge on the protein fractions in skeletal muscles was studied. The ultrastructure of the heart muscle was now in this experiments examined as well.Japanese quail cockerels, aged 48 days were exposed to 2 G hypergravitation /group IV/ in a 6,4 m diameter centrifuge, to hypodynamy /group III/ and their combination /group V/, respectively for 6 days / Fig.1/. The hypodynamy in group III was achieved by suspending the birds in jackets without contact the floor. The group II was located in the centre ofthe turntable of the centrifuge. The control group I. was kept under normal conditions. The quantitative ultrastructure of myocard was evaluated by the methods of Weibel/3/ - this enables to determine the number, relative size and volume of mitochondria volume of single mitochondria, defficiency of mitochondrial cristae and volume of myofibrils.

Fusion and Breakup Reactions of 17S + 208Pb and 15C + 232ThHalo Nuclei Systems

2015 ◽  
Vol 11 (2) ◽  
pp. 2972-2978
Author(s):  
Fouad A. Majeed ◽  
Yousif A. Abdul-Hussien
Keyword(s):  
Experimental Data ◽  
Cross Section ◽  
Fusion Reaction ◽  
Fusion Cross Section ◽  
Reaction Cross ◽  
Recent Experimental Data ◽  
Barrier Distribution ◽  
Coupled Channel ◽  
Total Fusion ◽  
Full Quantum

In this study the calculations of the total fusion reaction cross section have been performed for fusion reaction systems 17F + 208Pb and 15C + 232Th which involving halo nuclei by using a semiclassical approach.The semiclassical treatment is comprising the WKB approximation to describe the relative motion between target and projectile nuclei, and Continuum Discretized Coupled Channel (CDCC) method to describe the intrinsic motion for both target and projectile nuclei. For the same of comparsion a full quantum mechanical clacualtions have been preforemd using the (CCFULL) code. Our theorticalrestuls are compared with the full quantum mechaincialcalcuations and with the recent experimental data for the total fusion reaction  checking the stability of the distancesThe coupled channel calculations of the total fusion cross section σfus, and the fusion barrier distribution Dfus. The comparsion with experiment proves that the semiclassiacl approach adopted in the present work reproduce the experimental data better that the full quantal mechanical calcautions. 

scholarly journals Effect of commercially available and experimental potassium oxalate-based dentin desensitizing agents in dentin permeability: influence of time and filtration system

2006 ◽  
Vol 17 (4) ◽  
pp. 300-305 ◽  
Author(s):  
Sérgio Lima Santiago ◽  
José Carlos Pereira ◽  
Ana Christina Bonato Figueiredo Martineli
Keyword(s):  
Hydraulic Conductance ◽  
Potassium Oxalate ◽  
Group V ◽  
Significance Level ◽  
Group Iii ◽  
Dentin Permeability ◽  
Group I ◽  
Filtration System ◽  
Desensitizing Agents

This study evaluated the influence of time after application of oxalate solutions in reducing dentin hydraulic conductance. Fifty dentin discs were obtained from extracted human third molars and assigned to 5 groups (n=10), according to the desensitizing agent used: Group I: OxaGel; Group II: experimental agent DD-1: Group III: experimental agent DD-2. In Groups IV and V, a placebo gel and deionized water were used as control, respectively. The agents were applied for 3 min, washed out and the hydraulic conductance was measured immediately and at 5-, 15- and 30-min intervals, and after acid etching. Data were analyzed statistically by two-way ANOVA and Duncan's test at 5% significance level. Groups I, II and III did not differ significantly from each other in any of the time intervals (p>0.05). Likewise, Groups IV and V were statistically similar to each other (p>0.05). The active agents reduced significantly dentin permeability in comparison to control groups (p<0.05). Dentin permeability measured in vitro decreased significantly with time regardless of the agent applied (either active or control agents). The results of Group V, in which no dentin desensitizing agent was employed, indicates that the assessment of dentin permeability by this method must be interpreted with caution.

Group III-nitride alloys as photovoltaic materials

2004 ◽  
Author(s):  
Joel W. Ager III ◽  
Junqiao Wu ◽  
Kin M. Yu ◽  
R. E. Jones ◽  
S. X. Li ◽  
...  
Keyword(s):  
Group Iii ◽  
Photovoltaic Materials ◽  
Nitride Alloys ◽  
Group Iii Nitride
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