Growth and Characterization of GaPNAs on Si

2003 ◽  
Vol 799 ◽  
Author(s):  
John Geisz ◽  
J. M. Olson ◽  
W. E. McMahon ◽  
T. Hannappel ◽  
K. Jones ◽  
...  
Keyword(s):  
Band Gaps ◽  
Structural Quality ◽  
X Ray ◽  
Photovoltaic Applications ◽  
Line Widths ◽  
Nitrogen Alloy ◽  
Lattice Matched ◽  
Thick Layers

ABSTRACTThe dilute nitrogen alloy GaPNAs can be lattice matched to silicon with band gaps ranging from 2.3 eV to less than 1.7eV making it of special interest for photovoltaic applications. We have studied the growth and structural quality of the alloy grown on vicinal Si(001) and GaP(001) substrates by MOCVD. Using a particular nucleation scheme, we have deposited 1-μm thick layers that are crack-free and exhibit narrow x-ray line widths. The FWHM of the (004) x-ray reflection from a GaP1−xNx epilayer decreases dramatically from ∼300 arcsec for x=0 to 18 arcsec for x = 0.021. The band gap of this alloy is 1.96 eV. With the addition of As (and more N), the x-ray line widths tend to increase slightly to 27 arcsec.

Characterization of CdTe:Zn:V crystals grown under microgravity conditions

2002 ◽  
Vol 17 (12) ◽  
pp. 3037-3041 ◽  
Author(s):  
V. Corregidor ◽  
V. Babentsov ◽  
J. L. Castaño ◽  
M. Fiederle ◽  
T. Feltgen ◽  
...  
Keyword(s):  
Growth Process ◽  
Structural Quality ◽  
Seed Region ◽  
Photoluminescence Spectra ◽  
Positive Role ◽  
X Ray ◽  
Microgravity Conditions

CdTe:Zn:V crystals grown by the seeded Bridgman method in microgravity conditions during the STS95-Spacelab-AGHF-1 mission and in the ground laboratory (l-g) were analyzed and compared. The results obtained clearly show that the structural quality of the space crystal is better. Density of inclusions, concentration of dislocations, and presence of stresses are lower in the microgravity-grown (μ-g) crystal. The l-g crystal contains twins and grains from the beginning of the growth process, that is, from the near-seed region. In general, the concentration of inclusions and amount of segregated impurities on the l-g crystal are larger than in the μ-g crystal. X-ray rocking curves and low-temperature photoluminescence spectra demonstrate the relatively high quality of both crystals on a microscale at the beginning of the growth and show that the l-g conditions were worse at the end. The results of this investigation demonstrate a positive role of contactless growth and μ-g conditions in the melt in suppressing the creation of inclusions and dislocations.

Characterization of epitaxial SrTiO3/YBa2Cu3O7 layers deposited on (001) MgO by laser ablation

1993 ◽  
Vol 8 (11) ◽  
pp. 2780-2784 ◽  
Author(s):  
P. Scardi ◽  
L. Lutterotti ◽  
L. Correra ◽  
S. Nicoletti
Keyword(s):  
Laser Ablation ◽  
Critical Current ◽  
Ybco Film ◽  
Structural Quality ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
X Ray ◽  
Columnar Grains

We discuss the results obtained for SrTiO3/YBa2Cu3O7 layers deposited on (001) MgO substrates by UV pulsed laser ablation. Different samples were prepared to study both the growth of a thin (55 nm) layer of SrTiO3 on MgO and the successive epitaxy of a 220 nm YBa2Cu3O7 (YBCO) film on the SrTiO3 layer. An x-ray diffraction (XRD) texture analysis is reported for the bilayers together with resistivity versus temperature and critical current density (Jc) measurements of the superconducting films. The results show that YBCO grains grow with c-axis normal to the surface; the main in-plane orientations are [100] MgO // [100] SrTiO3 // [100] YBCO ([010] YBCO). The XRD line broadening analysis suggests that YBCO columnar grains grow along the whole thickness of the film, also evidencing dislocations and/or faulting separated by a mean distance of 80 nm. The values obtained for the critical current of the superconductor demonstrate the effectiveness of the SrTiO3 intermediate layer in improving the structural quality of the YBCO film.

Structural Characterization of Bulk AlN Single Crystals Grown from Self-Seeding and Seeding by SiC Substrates

2006 ◽  
Vol 527-529 ◽  
pp. 1521-1524 ◽  
Author(s):  
Balaji Raghothamachar ◽  
Rafael Dalmau ◽  
Michael Dudley ◽  
Raoul Schlesser ◽  
Dejin Zhuang ◽  
...  
Keyword(s):  
Growth Conditions ◽  
Structural Quality ◽  
X Ray Diffraction ◽  
Free Standing ◽  
X Ray ◽  
Highly Strained ◽  
Defect Densities ◽  
High Defect Densities

Using a combination of synchrotron white beam x-ray topography (SWBXT) and high resolution x-ray diffraction (HRXRD), the structural quality of AlN crystals grown by various sublimation-based techniques have been non-destructively analyzed. Spontaneously nucleated AlN crystals are characterized by very low defect densities but their size is small. Self-seeding results in nucleation of multiple grains of different orientations, a few of which are of good quality while most are highly strained. Using readily available commercial 4H and 6H-SiC substrates, several growth runs have been carried out using different growth conditions to obtain thick AlN layers, either attached to the seed or free-standing. While attached layers are typically cracked and highly strained, crack-free free-standing layers can be obtained by delamination or SiC decomposition. X-ray characterization reveals these crystals have good purity but moderately high defect densities.

Characterization of Natural and Synthesized FeTiO3 Crystals With RBS/PIXE/XRD

1997 ◽  
Vol 07 (03n04) ◽  
pp. 265-275
Author(s):  
R. Q. Zhang ◽  
S. Yamamoto ◽  
Z. N. Dai ◽  
K. Narumi ◽  
A. Miyashita ◽  
...  
Keyword(s):  
Single Crystals ◽  
Ion Beam ◽  
Pressure Control ◽  
Floating Zone ◽  
X Ray Diffraction ◽  
X Ray ◽  
Beam Analysis ◽  
Ppm Level

Natural FeTiO 3 (illuminate) and synthesized FeTiO 3, single crystals were characterized by Rutherford backscattering spectroscopy combined with channeling technique and particle-induced x-ray emission (RBS-C and PIXE). The results obtained by the ion beam analysis were supplemented by the x-ray diffraction analysis to identify the crystallographic phase. Oriented single crystals of synthesized FeTiO 3 were grown under the pressure control of CO 2 and H 2 mixture gas using a single-crystal floating zone technique. The crystal quality of synthesized FeTiO 3 single crystals could be improved by the thermal treatment but the exact pressure control is needed to avoid the precipitation of Fe 2 O 3 even during the annealing procedure. Natural FeTiO 3 contains several kinds of impurities such as Mn , Mg , Na and Si . The synthesized samples contain Al , Si and Na which are around 100 ppm level as impurities. The PBS-C results of the natural sample imply that Mn impurities occupy the Fe sublattice in FeTiO 3 or in mixed phase between ilmenite and hematite.

Characterization of WC-Co Coatings Using HP/HVOF Process

1996 ◽  
Author(s):  
S.Y. Hwang ◽  
B.G. Seong ◽  
M.C. Kim
Keyword(s):  
Wear Resistance ◽  
X Ray Diffraction ◽  
High Carbon ◽  
Properties Of Coatings ◽  
X Ray ◽  
Hvof Process ◽  
Number Of Passes ◽  
Oxygen Fuel

Abstract To maintain surface roughness of process rolls in cold rolling steel plants, WC-Co coatings have been known to be effective ones. In this study, a high pressure/high velocity oxygen fuel (HP/HVOF) process was used to obtain WC-Co coatings. To get the best quality of coatings, WC-Co coatings are sprayed with numerous powders made by various processes. These powders include agglomerated sintered powders, fused-crushed powders, extra high carbon WC-Co powders and (W2C, WC)-Co powders. After spraying, properties of coatings such as hardness, wear resistance. X-ray diffraction, and microstructures were analyzed. For coatings produced by agglomerated-sintered powders, hardness of the coating increased as power levels and the number of passes were increased. In case of the coatings produced by fused-crushed powders, a very low deposition rate was obtained due to a low flowablity of the powders. In addition, the WC-Co coatings sprayed with extra carbon content of WC-Co did not show improved hardness and wear resistance. Also, some decomposition of WC was observed in the coating. Finally, the coatings produced by (W2C, WC)-Co powders produced higher hardness and lower wear resistance coating.

scholarly journals Crystallization, optimization and preliminary X-ray characterization of a metal-dependent PI-PLC fromStreptomyces antibioticus

2012 ◽  
Vol 68 (11) ◽  
pp. 1378-1386 ◽  
Author(s):  
Michael R. Jackson ◽  
Thomas L. Selby
Keyword(s):  
X Ray Diffraction ◽  
Hanging Drop ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
Streptomyces Antibioticus ◽  
Cell Parameters ◽  
Heavy Atoms ◽  
Hanging Drop Method

A recombinant metal-dependent phosphatidylinositol-specific phospholipase C (PI-PLC) fromStreptomyces antibioticushas been crystallized by the hanging-drop method with and without heavy metals. The native crystals belonged to the orthorhombic space groupP222, with unit-cell parametersa= 41.26,b= 51.86,c = 154.78 Å. The X-ray diffraction results showed significant differences in the crystal quality of samples soaked with heavy atoms. Additionally, drop pinning, which increases the surface area of the drops, was also used to improve crystal growth and quality. The combination of heavy-metal soaks and drop pinning was found to be critical for producing high-quality crystals that diffracted to 1.23 Å resolution.

scholarly journals Исследование этапов превращения кремния в карбид кремния в процессе атомного замещения методами полного внешнего отражения рентгеновских лучей и рентгеновской дифрактомерии

2022 ◽  
Vol 64 (3) ◽  
pp. 326
Author(s):  
С.А. Кукушкин ◽  
А.В. Осипов ◽  
Е.В. Осипова ◽  
В.М. Стожаров
Keyword(s):  
Structural Quality ◽  
Total External Reflection ◽  
X Rays ◽  
Reflection Method ◽  
X Ray Diffraction ◽  
Modified Technique ◽  
Substitution Method ◽  
X Ray ◽  
Sic Films

X-ray diffraction and total external reflection of X-rays (X-ray reflectometry) methods were used to study the successive stages of synthesis of epitaxial SiC films on Si (100) X-ray diffraction and total external X-ray reflection (XRD) methods were used to study successive stages of synthesis of epitaxial SiC films on Si (100) surfaces, (110) and (111) surfaces by the atom substitution method. The data on the transformation evolution of (100) surfaces were studied, (110) and (111) Si, into SiC surfaces. A comparative analysis of the X-ray structural quality of the SiC layers grown on Si by the atom substitution method with the quality of SiC layers grown by Advanced Epi by the standard CVD method. A modified technique for the total outer X-ray reflection method, based on measurements of the intensity of the reflected X-rays using a special parabolic mirror. It is shown that the method of total external reflection method makes it possible to obtain important information about the degree of surface roughness of SiC layers, the evolution of their crystal structure and plasmon energy in the process of Si to SiC conversion.

scholarly journals Regeneration of Planarian Auricles and Reestablishment of Chemotactic Ability

2021 ◽  
Vol 9 ◽  
Author(s):  
Eugene Matthew P. Almazan ◽  
Joseph F. Ryan ◽  
Labib Rouhana
Keyword(s):  
Molecular Mechanisms ◽  
Behavioral Experiments ◽  
X Ray ◽  
Preferential Expression ◽  
Chemical Stimuli ◽  
And Function ◽  
Function Models ◽  
Chemotactic Ability

Detection of chemical stimuli is crucial for living systems and also contributes to quality of life in humans. Since loss of olfaction becomes more prevalent with aging, longer life expectancies have fueled interest in understanding the molecular mechanisms behind the development and maintenance of chemical sensing. Planarian flatworms possess an unsurpassed ability for stem cell-driven regeneration that allows them to restore any damaged or removed part of their bodies. This includes anteriorly-positioned lateral flaps known as auricles, which have long been thought to play a central role in chemotaxis. The contribution of auricles to the detection of positive chemical stimuli was tested in this study using Girardia dorotocephala, a North American planarian species known for its morphologically prominent auricles. Behavioral experiments staged under laboratory conditions revealed that removal of auricles by amputation leads to a significant decrease in the ability of planarians to find food. However, full chemotactic capacity is observed as early as 2 days post-amputation, which is days prior from restoration of auricle morphology, but correlative with accumulation of ciliated cells in the position of auricle regeneration. Planarians subjected to x-ray irradiation prior to auricle amputation were unable to restore auricle morphology, but were still able to restore chemotactic capacity. These results indicate that although regeneration of auricle morphology requires stem cells, some restoration of chemotactic ability can still be achieved in the absence of normal auricle morphology, corroborating with the initial observation that chemotactic success is reestablished 2-days post-amputation in our assays. Transcriptome profiles of excised auricles were obtained to facilitate molecular characterization of these structures, as well as the identification of genes that contribute to chemotaxis and auricle development. A significant overlap was found between genes with preferential expression in auricles of G. dorotocephala and genes with reduced expression upon SoxB1 knockdown in Schmidtea mediterranea, suggesting that SoxB1 has a conserved role in regulating auricle development and function. Models that distinguish between possible contributions to chemotactic behavior obtained from cellular composition, as compared to anatomical morphology of the auricles, are discussed.

Characterization and Granulometric Correction Soil for the Production of Soil-Cement Blocks for Two Method, Particle Size and X-Ray Florescence to be Inserted in Phase Change Materials (PCMS)

2014 ◽  
Vol 798-799 ◽  
pp. 355-359 ◽  
Author(s):  
Valter Bezerra Dantas ◽  
U.U. Gomes ◽  
A.B. Vital ◽  
G.S. Marinho ◽  
Ariadne de Souza Silva
Keyword(s):  
Particle Size ◽  
Phase Change Materials ◽  
Clay Content ◽  
Particle Size Analysis ◽  
Liquid Limit ◽  
Size Analysis ◽  
X Ray ◽  
Soil Cement

This paper presents the results of tests for characterization of soil samples collected in Mossoró-RN, UFERSA-RN Campus (5 ° 12'34 .68 "South latitude, 37 ° 19 '5.74 "west longitude), for the purpose of producing soil-cement for the manufacture of pressed blocks. Objective of improving the quality of soil-cement, and provide conditions for the use of the soil making it ideal for the production of soil-cement block. Tests of compaction, particle size analysis, plastic limit, liquid limit and correct particle size, X-ray fluorescence and morphology by scanning electron microscopy (SEM). It was concluded that the soil needs correction particle size, due to the high clay content. The method combined grading, sieving, sedimentation and blooming X-ray as the fastest and most accurate in correcting soil particle size.

Growth and Characterization of Single Crystal Epitaxial CoGa on MBE Grown III-V Semiconductors

1988 ◽  
Vol 144 ◽  
Author(s):  
K. C. Garrison ◽  
C. J. Palmstrøm ◽  
R. A. Bartynski
Keyword(s):  
Substrate Temperature ◽  
Single Crystal ◽  
Single Crystals ◽  
Structural Quality ◽  
High Quality ◽  
Auger Analysis ◽  
Post Deposition

ABSTRACTWe have demonstrated growth of high quality single crystal CoGa films on Ga1−xAlxAs. These films were fabricated in-situ by codeposition of Co and Ga on MBE grown Ga1−xAlxAs(100) surfaces. The elemental composition of the films was determined using Rutherford Backscattering (RBS) and in-situ Auger analysis. The structural quality of the films' surfaces was studied using RHEED (during deposition) and LEED (post deposition). RBS channeling was used to determine the bulk crystalline quality of these films.For ∼500 Å CoGa films grown at ∼450°C substrate temperature, channeling data showed good quality epitaxial single crystals [χmin ∼7%] with minimal dechanneling at the interface.

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