Comparative Study Of Gan Movpe Growth Processes Using Two Different “Surface Preparation-Carrier Gas” Combinations

1998 ◽  
Vol 512 ◽  
Author(s):  
P. Vennegues ◽  
S. Haffouz ◽  
A. Bouille ◽  
M. Leroux ◽  
B. Beaumont
Keyword(s):  
Growth Process ◽  
Defect Density ◽  
Three Dimensional ◽  
Surface Preparation ◽  
Photoluminescence Properties ◽  
Carrier Gas ◽  
Luminescence Efficiency ◽  
Growth Modes ◽  
Movpe Growth ◽  
Drastic Effect

ABSTRACTThe growth modes and resulting microstructures of GaN films grown by Metalorganic Vapor Phase Epitaxy (MOVPE) on (0001) sapphire with either a simple nitridation of the surface and N2 as carrier gas or with a treatment of the nitridated surface under silane and ammonia with a mixture of H2 and N2 as carrier gas have been investigated. The second process results in a three dimensional first stage of the growth before a coalescence of the islands and the smoothing of the surface. Using this growth process, the defects density can be decreased down to 3.108 cm−2. This reduction in defect density has a drastic effect on photoluminescence properties of the material, and the luminescence efficiency can be increased by a factor of 20. It is also observed that the strain of this material is much higher as compared with material grown with the first process.

Analysis of SiC CVD Growth in a Horizontal Hot-Wall Reactor by Experiment and 3D Modelling

2007 ◽  
Vol 556-557 ◽  
pp. 61-64
Author(s):  
Y. Shishkin ◽  
Rachael L. Myers-Ward ◽  
Stephen E. Saddow ◽  
Alexander Galyukov ◽  
A.N. Vorob'ev ◽  
...  
Keyword(s):  
Growth Rate ◽  
Growth Process ◽  
Three Dimensional ◽  
Chemical Species ◽  
3D Modelling ◽  
Complete Model ◽  
Cvd Growth ◽  
Dimensional Simulation ◽  
Insight Into ◽  
Hot Zone

A fully-comprehensive three-dimensional simulation of a CVD epitaxial growth process has been undertaken and is reported here. Based on a previously developed simulation platform, which connects fluid dynamics and thermal temperature profiling with chemical species kinetics, a complete model of the reaction process in a low pressure hot-wall CVD reactor has been developed. Close agreement between the growth rate observed experimentally and simulated theoretically has been achieved. Such an approach should provide the researcher with sufficient insight into the expected growth rate in the reactor as well as any variations in growth across the hot zone.

scholarly journals Luminescence of Eu3+ in Some Scandium Phosphates

2021 ◽  
pp. 638-640
Author(s):  
Rajani A. Bhoyar ◽  
A. C. Nayak
Keyword(s):  
Solid State ◽  
Energy Levels ◽  
Concentration Quenching ◽  
Lanthanide Ions ◽  
Photoluminescence Properties ◽  
Trivalent Metal ◽  
Suitable Host ◽  
Relative Ease ◽  
Luminescence Efficiency ◽  
Light Lanthanides

Lanthanide ions are very efficient activators. Due to the presence of shielded 4f shell, the energy levels can be predicted with relative ease. Interaction with the surrounding lattice is minimum and luminescence efficiency is high. For this reason, many important phosphors having various applications have been discovered which use lanthanide activators. For obtaining efficient phosphors, it is important to find a suitable host for lanthanide activators which can accommodate these ions without concentration quenching. The hosts must be transparent to the emitted light. Lanthanides, most commonly occur as trivalent. Thus, hosts constituted by trivalent metals can be suitable. Yttrium compounds have been extensively studied as hosts. Scandium is another trivalent metal. Compared to the yttrium compounds, Scandium compounds have been very scarcely studied as hosts. We are investigating Scandium compounds as luminescence hosts. Synthesis and photoluminescence properties of Sr9 Sc (PO4)7 : Eu3+ and Sr8MgSc(PO4)7:Eu3+ phosphor are described in this work. The phosphors were prepared by solid state reaction. Usually, these phosphors are reduced and results on Eu2+ photoluminescence are reported. However, we have recorded photoluminescence before reduction and thus new results on Eu3+ emission could be obtained.

Growth and Characterization of 2″ 6H-Silicon Carbide

1999 ◽  
Vol 572 ◽  
Author(s):  
Erwin Schmitt ◽  
Robert Eckstein ◽  
Martin Kölbl ◽  
Amd-Dietrich Weber
Keyword(s):  
Silicon Carbide ◽  
Boundary Conditions ◽  
Growth Process ◽  
Defect Density ◽  
Crystal Quality ◽  
Process Conditions ◽  
Thermal Boundary Conditions ◽  
Sublimation Growth ◽  
Defect Densities

ABSTRACTFor the growth of 2″ 6H-SiC a sublimation growth process was developed. By different means of characterization crystal quality was evaluated. Higher defect densities, mainly in the periphery of the crystals were found to be correlated to unfavourable process conditions. Improvement of thermal boundary conditions lead to a decreased defect density and better homogeneity over the wafer area.

A three-dimensional manganese(II) coordination polymer with two functional properties: magnetism and photochemical detection

2021 ◽  
Vol 77 (12) ◽  
Author(s):  
Dan Zhao ◽  
Yanyan An ◽  
Tingting Guo ◽  
Juanzhi Yan ◽  
Danmei Song
Keyword(s):  
Coordination Polymer ◽  
Hydrothermal Reaction ◽  
Three Dimensional ◽  
Building Blocks ◽  
Photoluminescence Properties ◽  
X Ray Diffraction ◽  
Detection Mechanism ◽  
Susceptibility Data ◽  
Dichromate Ions ◽  
Ditopic Ligand

Hydrothermal reaction of Mn2+ with the ditopic ligand 2,5-bis(1H-1,2,4-triazol-1-yl)benzoic acid (Hdtba) resulted in the complex poly[aqua[μ3-2,5-bis(1H-1,2,4-triazol-1-yl)benzoato-κ3 N 4:N 4′:O]chloridomanganese(II)] monohydrate], {[Mn(C11H7N6O2)Cl(H2O)]·H2O} n , (I). Coordination polymer I has been characterized by X-ray diffraction, IR spectroscopy, elemental analysis, thermogravimetry and susceptibility measurements. The topology of I corresponds to a three-dimensional (3,6)-conn net linked by {Mn2Cl2(COO)2} building blocks and dtba− anions. Significant antiferromagnetic exchange is observed within the dinuclear {Mn2Cl2(COO)2} subunits. A fit of the susceptibility data resulted in the magnetic parameters g = 1.93 and J = −1.52. Studies of the photoluminescence properties revealed that I represents a promising luminescence sensor for sensitively detecting dichromate ions in aqueous solution. The associated photochemical detection mechanism was studied in detail.

Origin of the Nucleation Rate Empirical Data Inconsistencies for the Vapor-Gas Systems

2008 ◽  
Vol 3 (3) ◽  
pp. 46-52
Author(s):  
Anna A. Volf ◽  
Elena G. Fominykh ◽  
Mikhail P. Anisimov
Keyword(s):  
Nucleation Rate ◽  
Empirical Data ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Diffusion Chamber ◽  
Ambient Atmosphere ◽  
Gas Treatment ◽  
Carrier Gas ◽  
Nucleation Parameters ◽  
Set Up

Independent results for vapor nucleation rates illustrate the nucleation rates inconsistencies for identical vapor-gas systems at the same conditions. Nature of these inconsistencies is not yet understood enough. Assumption is discussed that a reason for the experimental data inconsistencies is appeared in the result of the carrier gas effects on nucleation. It was supposed for a long time that any carrier gas is an ambient atmosphere to keep the nucleation temperature only. The recent experimental results have shown that a vapor-gas nucleation needs to be treated in approximation of binary solutions, i. e. a composition axis is appeared in addition to axes of nucleation rate versus pressure. Each single line of a nucleation rate isotherm is transformed to surface in a three dimensional space of nucleation parameters. Flow diffusion chamber and expansion Wilson type set up data comparison are discussed on the example of the published empirical data. It was shown using a model system that these two experimental realizations produce the inconsistent trajectories in the space of nucleation parameters. That misfit induces the different origin data inconsistencies and demonstrates relevance of gas treatment as an individual component of a nucleating vapor-gas system.

Structures and Photoluminescence Properties of Four Cadmium(II) Coordination Polymers Synthesized by Rigid Ligands and N-Donor Ligands

2015 ◽  
Vol 68 (5) ◽  
pp. 742 ◽  
Author(s):  
Qing-Guo Meng ◽  
Lin-Tong Wang ◽  
Ji-Tao Lu ◽  
Xin Wang ◽  
Wei Lu ◽  
...  
Keyword(s):  
Coordination Polymers ◽  
Three Dimensional ◽  
Photoluminescence Properties ◽  
Thermal Stabilities ◽  
Structure Comparison ◽  
Layer Compound ◽  
Carboxylate Groups ◽  
Secondary Building Units ◽  
Coordinated Water ◽  
Dna 2

Four metal–organic coordination polymers, [Cd2(dna)2(2,2′-bpy)2]n (1), {[Cd4(dna)4(im)3]·5H2O}n (2), {[Cd2(dna)2(4,4′-bpy)(H2O)2]·2EtOH}n (3), and {[Cd4(dna)4(1,3-dpp)4(H2O)4]·2H2O}n (4) (H2dna = 4,6-dimethyl-5-nitroisophthalic acid; 2,2′-bpy = 2,2′-bipyridine; im = imidazole; 4,4′-bpy = 4,4′-bipyridine; 1,3-dpp = 1,3-di(4-pyridyl)propane; and EtOH = ethanol, have been solvothermally synthesized and characterized. Compound 1 displays a one-dimensional (1D) ladder structure and the neighbouring ladders are further stabilized by π···π interactions to form a two-dimensional (2D) layer. Compound 2 forms a 2D layer based on infinite 1D [Cd2(COO)4]n chain and the im ligands act as terminal ligands, preventing expansion of the dimensionality. Compound 3 features a 2D 44-sql layer based on binuclear [Cd2(COO)4] secondary building units as 4-connected nodes, and is further linked to be an unusual three-dimensional (3D) supramolecular architecture by hydrogen bonds involving the coordinated water molecules, carboxylate groups, and lattice ethanol molecules. Compound 4 possesses a 2-fold interpenetrated dia net. The diverse structures and topologies of compounds 1–4 indicate that the N-containing ligands have significant effects on the formation of the final network structures. In addition, the thermal stabilities, structure comparison, and photoluminescence properties of the complexes have been investigated.

K3Eu5(PO4)6: hydrothermal synthesis, crystal structure and photoluminescence properties

2019 ◽  
Vol 75 (7) ◽  
pp. 883-890 ◽  
Author(s):  
Ya-Li Xue ◽  
Ai-Yun Zhang ◽  
Xiao-Yang Han ◽  
Xiao-Qi Cui ◽  
Ling Deng ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Hydrothermal Synthesis ◽  
Uv Light ◽  
Three Dimensional ◽  
Visible Region ◽  
Monoclinic Space Group ◽  
Photoluminescence Properties ◽  
X Ray Diffraction ◽  
Strong Luminescence ◽  
Light Excitation

An anhydrous orthophosphate, K3Eu5(PO4)6 (tripotassium pentaeuropium hexaphosphate), has been prepared by a high-temperature solid-state reaction combined with hydrothermal synthesis, and its crystal structure was determined by single-crystal X-ray diffraction analysis (SC-XRD). The results show that the compound crystallizes in the monoclinic space group C2/c and the structure features a three-dimensional framework of [Eu5(PO4)6]∞, with the tunnel filled by K+ ions. The IR spectrum, UV–Vis spectrum and luminescence properties of polycrystalline samples of K3Eu5(PO4)6, annealed at temperatures of 650, 700, 750, 800 and 850 °C, were investigated. Although with a full Eu3+ concentration (9.96 × 1021 ions cm−3), the self-activated phosphor K3Eu5(PO4)6 shows s strong luminescence emission intensity with a quantum yield of 37%. Under near-UV light excitation (393 nm), the series of samples shows the characteristic emissions of Eu3+ ions in the visible region from 575 to 715 nm. The sample sintered at 800 °C gives the strongest emission and its lifetime sintered at 800 °C (1.88 ms) is also the longest of all.

An Infrared Interferometer for Elastoplastic Crack-Tip Field Investigation of Homogeneous and Bimaterial Beams: A Study of Three-Dimensional Effects and J-Dominance

1998 ◽  
Vol 65 (4) ◽  
pp. 1032-1041
Author(s):  
J. K. Sinha ◽  
H. V. Tippur
Keyword(s):  
Plane Deformation ◽  
Three Dimensional ◽  
Surface Preparation ◽  
Field Measurements ◽  
Sample Surface ◽  
Field Investigation ◽  
Crack Tip Field ◽  
Full Field ◽  
Infrared Wavelength ◽  
Dimensional Effects

An infrared interferometer capable of performing real-time full-field noncontacting deformation field measurements on optically rough surfaces is proposed as a tool for elastoplastic fracture mechanics investigations. The choice of the infrared wavelength allows interferometric measurements on fracture samples with little or no surface preparation and is more tolerant of the damage accumulation near the crack. The interferometer also bridges a sensitivity gap among existing techniques for out-of-plane deformation measurement. First, a rigorous Fourier optics analysis is provided for the interferometer and the range of surface roughness that can be studied using this interferometer is examined. The interferometer is then used for mapping deformations near elastoplastically deformed cracks in aluminum beams and solder-copper bimaterials. The regions of dominant three-dimensional effects and J-dominance are examined on the sample surface by evaluating measurements along with companion finite element analyses and the HRR fields.

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