bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of Morphological Instability and Cells During Rapid Solidification of Laser Annealed Silicon Alloys
Authors: Narayan J. , White C. W. 
Published: March 2011

ABSTRACTThe details of morphological instability occurring during rapid solidification have been studied in In+, Ga+, Sb+, Bi+, Ge+, Fe+ and Cr+ implanted silicon specimens after pulsed laser annealing. The average cell sizes were determined at the onset of instability and in the region of well-developed instability using x-section and plan-view electron microscopy. The total and substitutional solute concentration profiles were determined using Rutherford backscattering and channeling techniques. The formation of cells and the critical solute concentrations associated with instability were studied as a function of velocity of solidification, which was varied by controlling the substrate temperature or the laser parameters. The results on the cell formation and the critical solute concentrations were compared with the predictions of the perturbation theory which took into account the dependence of distribution coefficients on the velocity of solidification. A good agreement between the calculations and the experimental results was obtained. We also examined theoretically the effect of reduction in surface tension due to segregation of impurities on cell sizes and critical solute concentrations associated with instability.
Prospects for Monolithic GaAs/Si Integration
Authors: Choi H. K. , Turner G. W. , Tsaur B-Y. 
Published: March 2011

ABSTRACTThe status of monolithic GaAs/Si (MGS) integration is reviewed and its future prospects are discussed. The MGS material now available is satisfactory for majority-carrier devices, but improvement in quality is needed for minority-carrier devices. By using a suitable sequence of processing steps, fabrication of GaAs MESFETs and Si MOSFETs on the same wafer and monolithic integration of GaAs/AlGaAs double-heterostructure LEDs and Si MOSFETs have been achieved. The GaAs and Si FETs show characteristics comparable to those for devices fabricated on separate GaAs and Si substrates. The LEDs have been modulated up to 27 Mb/s by applying a pattern of voltage pulses to the MOSFET gate. Two promising applications of MGS integration are optical interconnects between Si VLSI chips and monolithic microwave integrated circuits. Much better performance should be obtained by operating MGS ICs at liquid nitrogen temperature.
Admittance Measurements at Epitaxial and Nonepitaxial Silicide Schottky Contacts
Authors: Werner J. , Tung R. T. , Levi A. F. J. , Anzlowar M. 
Published: March 2011

ABSTRACTWe report results of an extensive study examining the usefulness of low frequency capacitance measurements for the characterization of interface states at intimate Schottky contacts. Our measurements on epitaxial as well as on nonepitaxial silicides reveal that the imaginary component of the low frequency ac-admittance is usually inductive. This inductance is caused by minority carriers that are injected by the Schottky contact and modulate the conductivity of the series resistance of the bulk silicon. The frequently reported excess capacitances (instead of inductances) that were ascribed to interface states are only reproducible when we use imperfect back-contacts to the bulk Si that add a contact resistance to the equivalent dc-circuit of the Schottky diode. Excess low frequency capacitances at intimate Schottky contacts are therefore not related to interface states but rather to the contact resistance of the back-contact.
Effect of Dy Additions on Microstructure and Magnetic Properties of Fe-Nd-B Magnets
Authors: Ramesh R. , Thomas G. , Ma B. M. 
Published: March 2011

ABSTRACTThis paper addresses the effect of Dy addition upon the magnetic properties, microstructure and microcomposition of Fe-Nd-B magnets. It is shown that increasing additions of Dy causes the remanence, Br to decrease linearly. The intrinsic coercivity, iHc, increases sharply for small additions of Dy, but the increase is not proportional for higher Dy contents. The iHc increases almost linearly with the effective anisotropy field of the RE2Fe14B phase until the Dy content is about 10% of the total rare earth content. Above this concentration, there is a strong deviation from linearity. Various types of possible concentration profiles of the substituted rare earth are suggested. It is also argued that preferential segregation of Dy to the interfaces could be beneficial in increasing the nucleation field. Morphologically there is no apparent effect of Dy on the microstructure. However, in the 5 atomic % Dy sample, Dy rich oxides were observed. It is shown through Energy Dispersive Xray Spectroscopy (EDXS) line profiling that Dy partitions preferentially into the RE2Fe14B phase in all the cases. No segregation of Dy to the interphase interfaces has been detected.
Thin Film Fabrication of R2Fe14B Compounds
Authors: Zasadzinski J. F. , Segre C. U. , Rippert E. D. , Chrzas J. , Radusewicz P. 
Published: March 2011

ABSTRACTThin Films (≃4000 A) of R2Fe14B compounds have been synthesized by d.c. triode sputtering for R=Nd,Sm and Er. Deposition onto single-crystal substrates heated to 600”C and with rates of 1.3 A/s results in nearly epitaxial film growth such that the c-axis of the tetragonal structure is perpendicular to the film plane. As a consequence, intrinsic anisotropy effects are observed in the magnetic properties of the as-made films. Although sapphire and quartz substrates give the best results, similar directed growth is observed on recrystallized Nb foils. Magneto-optical measurements on the Nd-based compounds give a remnant polar Kerr angle θ=0.22° and coercive field Hc=5.5 k0e. The easy axis is in the film plane for R=Sm and Er and a remnant magnetization greater than 80% of saturation is observed for H applied parallel to the film plane. Electrical resistivity measurements on Nd2Fe14B films indicate that spin-disorder scattering from the rare earth site is important and features from both the Curie and spin reorientation temperatures are observed.
Low-Field Microwave Absorption in High-TC Superconducting Oxides
Authors: Ramakrishna B. L. , Ong E. W. , Iqbal Z. 
Published: March 2011

ABSTRACTLow-field non-resonant microwave absorption in an EPR spectrometer has been observed in the superconducting state of different samples of the new high-T oxides, YBa2Cu3O7-δ and La1.8Sr0.2CuO4. It has been attributed to flux slippage occurring at the Josephson junctions existing in the granular composite material. The dependence on particle size, temperature, microwave power, DC modulation amplitude and magnetic field has been studied.
Theoretical Studies of Oxygen Vacancies in YBa2Cu3O7-y
Authors: Richert Brent A. , Allen Roland E. 
Published: March 2011

ABSTRACTWe have performed semiempirical tight-binding calculations of the electronic structure of YBa2Cu3O7, with dand s orbitals included for all the metal atoms and p and sorbitals for oxygen. Here we report studies of oxygen vacancies on the O(1) chain sites in YBa2Cu3O7-y. The modification of the density of states ρ(E) and the shift of the Fermi energy Ep were calculated for 0 < y ≤ 1.0. The Fermi energy is found to increase monotonically with y, confirming the expectation that oxygen vacancies act as donors. Also, ρ(EF)is found to decrease with y.
3d-Metal Doping (Fe,Co,Ni,Zn) Of The High Tc Perovskite YBa2Cu3O7-y
Authors: Tarascon J. M. , Barboux P. , Greene L. H. , Hull G. W. , Bagley B. G. 
Published: March 2011

ABSTRACTThe structural, magnetic and superconducting properties of the mixed compounds YBa2Cu3−xMxO7-y (M = Ni,Zn,Fe and Co) are reported. Values of y, determined by titration, are found to be dependent on the nature and amount of the doping. The range of solubility is greater for the Fe and Co compounds (x = 1) than for those with Ni or Zn (x = 0.3). The undoped material is orthorhombic and remains orthorhombic after substitution for Cu by Ni or Zn, whereas a tetragonal phase is observed when Fe, Co are substituted for Cu. DC resistance and AC susceptibility measurements show that Tc is depressed from 90K (x = 0) to 45K (x = 0.2) for both the Ni and Zn doped compounds and Tc is destroyed in the Fe and Co doped compounds when x reaches 0.4. We suggest that a valence of 2 be assigned to the Ni and Zn and 3 to the Fe and Co ions.
Ion-Beam-Induced Destruction of Superconducting Phase Coherence in YBa2Cu3O7-δ
Authors: White Alice E. , Short K. T. , Jacobson D. C. , Poate J. M. , Dynes R. C. , Mankiewich P. M. , Skocpol W. J. , Howard R. E. , Anzlowar M. , Baldwin K. W. , Levi A. F. J. , Kwo J. R. , Hsieh T. , Hong M. 
Published: March 2011

ABSTRACTWe have explored the effects of ion beam irradiation on the electrical and structural properties of superconducting thin films of YBa2Cu3O7-δ. Damage created by nuclear energy loss processes degrades the superconducting transitions. In general, the onset temperatures do not vary significantly with ion fluence, but the transition widths broaden until the resistance no longer reaches zero. This behavior is strikingly similar to that observed in granular superconducting films where islands of superconductor are progressively decoupled from each other, destroying the phase coherence. Data from resistance measurements as well as from Rutherford Backscattering and channeling measurements suggest that ion bombardment is not changing the volume fraction of superconducting material substantially.
Site Exchange in High Temperature Superconductors
Authors: Li D. J. , Shibahara H. , Zhang J. P. , Marks L. D. 
Published: March 2011

ABSTRACTElectron microscopical analysis of brown powders of composition YBa2Cu3O6.5 produced by oil quenching and conventionally produced orthorhombic GdBa2Cu3O7-δ show in both cases clear evidence for site exchange both between the different heavy metals and the heavy metals and the copper sites. For instance, the brown powder is a mixture of phases which are based upon two trigonal phases, both with a=0.536 and c=0.666 nm, one with the Y atoms stacked on the (111) planes of the parent perovskite structure and the second where the Y atoms of this structure have interchanged with one of the copper sites. The GdBa2Cu3O7-δ, material shows numerous planar defects on (001) planes which can be understood as copper rich regions with additional copper planes in the Ba or Gd sites. These results, together with earlier reports of order-disorder in YBa2Cu3O7-δ, strongly indicate that there exist ordering energies in these materials which may be important with respect to the current indications of the important of grain boundary phases in degrading the performance of some superconductors.
Ion Beam Sputtering and Properties of Superconducting YBaCuO thin Films
Authors: Pavona D. , Baer H. , Berger H. , GasParov V. , Schmidt M. , Vasey F. , Reinhart F-K. 
Published: March 2011

ABSTRACTWe describe single-target ion beam sputtering of superconducting YBaCuO thin films mainly onto R-sapphire and (100) SrTiO3 substrates. We discuss different thermal treatments and consequent X-ray and resistivity results and conclude with X-ray photoelectron spectroscopy data which indicate formation of hydroxydes on the surface of films exposed to atmosphere.
Electrical, Chemical, and Structural Properties of Plasma Sprayed Y-Ba-Cu-Oxide Superconducting Coatings
Authors: Neiser R. A. , Kirkland J. P. , Elam W. T. , Herman H. , Rangaswamy S. , Letourneau V. M. , Osofsky M. 
Published: March 2011

ABSTRACTThick coatings of Y-Ba-Cu-oxide superconductors have been prepared by plasma spray processing. This paper reports a number of the important properties of coatings sprayed at two different power levels. The microstructure, porosity, and chemical composition of the coatings were studied in their as-sprayed and annealed states. Critical current and magnetic susceptibility measurements were made on the annealed coatings. X-ray diffraction was used to identify non-superconducting phases present in the coatings and to determine the superconducting phase's lattice constants.
Microstructural Characterization of Ba2YCu3O7 Films Produced by Co-Evaporation
Authors: Fisanick G. J. , Mankeewicht P. , Skocpolt W. , Howardt R. E. , Dayem A. , Fleming R. M. , White A. E. , Liou S. H. , Moore R. 
Published: March 2011

ABSTRACTBa2YCu3O7 films produced by co-evaporation of BaF2, Cu and Y onto <100> S1TiO3 substrates in an O2 ambient followed by post-annealing were analyzed using RBS, X-ray diffraction and Auger microscopy. These films exhibit Tc's (R=0) of =90K and a best Jc of > 1.0×106 A/cm2 at 81K for a =2500A thick film. RBS and Auger depth profiling limit the level of F present in the post-annealed films to <5 at. %, although F is evident in the as-deposited material. RBS channeling experiments yield a Xmin=31%, demonstrating the epitaxial quality of the films. X-ray diffraction shows that the films are predominantly oriented with c-axis perpendicular to the substrate, with narrow mosaic spread in-plane. A small portion of the film is in the form of needles oriented with a-axis perpendicular to the substrate, whose areal density is dependent on annealing conditions and local film stoichiometry. Scanning Auger microscopy confirms that the needles and c-axis plateaus have the same metal and oxygen stoichiometry. Also present in the film are insulating balls which appear to nucleate terraces in the c-axis perpendicular structure. Scanning Auger shows that these features are also close to the metals stoichiometry, but are C rich compared to the needles. The plateaus are covered with =11 times more C than the needles, indicating that the basal plane surface is highly reactive. Auger depth profiling and RBS show little evidence for interdiffusion.
Orientation Dependent X-Ray Absorption Near Edge Structure in YBa2Cu3O7 and La1.85Sr0.15ISCUO4
Authors: Heald S. M. , Tranquada J. M. , Moodenbaugh A. R. , Xu Y. 
Published: March 2011

ABSTRACTX-ray absorption measurements have been made on powder samples of YBa2Cu3O7 and La1.85sr0.15CuO4 oriented in a magnetic field. Measurements made at the Cu K edge with the x-ray polarization oriented perpendicular and parallel to the c-axis show distinct differences for both materials, indicating a strong anisotropy of the electronic states about the Cu atoms. The Y edge measurements show a much smaller anisotropy as expected due to its more symmetric environment. Preliminary analysis indicates these measurements should be useful in choosing between the conflicting interpretations of the near edge structure in these materials.
Transport and Meissner Effect Studies for YBa2(Cuy1−xZnx)3O7
Authors: Bloom S. H. , Kuric M. V. , Yao Y. S. , Guertin R. P. , Nichols D. , Jee C. , Kebede A. , Crow J. E. , Mihalisin T. , Myer G. N. , Schlottmann P. 
Published: March 2011

ABSTRACTSingle phase orthorhombic YBa2(Cuy1−xZnx)3O7 samples were formed for 0<x<0.16. The high T superconductivityXfor x=6 (T =90 K) is rapidly depressed with increasing x, and is quenched for x>0.08. Low field (<100 G) cooled magnetization studies show that the superconducting component decreases as x approaches the critical value for suppression of superconductivity, and this is supported by high resolution specific heat measurements in the vicinity of T. Temperature dependent electrical resistivity studies for x<0.08 show metallic behavior; for x>0.10 semiconducting behavior. The electrical resistance was studied at high quasihydrostatic pressures also, and for x=0.08 showed that T is depressed with increasing pressure: T → 0 K for P >10 GPa. This is in°contrast to YBa2(Cuy1−xZnx)3O7 where dT /dP>0. The data support evidence for the high sensitivity to chemical and ice perturbations of the physical properties of samples near the superconducting-normal transition region.
Phonons in YBa2Cu3O7−x Type Materials
Authors: Burns Gerald , Dacol F. H. , Freitas P. , König W. , Plaskett T. S. 
Published: March 2011

ABSTRACTInfrared reflectivity results of YBa2Cu3O7x and SmBa2Cu3O7−x, in the tetragonal semiconducting phase, are reported. At least 10 of the 11 group theoretically allowed modes are observed, and the 11th may be observed in the Sm-material. Due to the fact that the modes are clearly resolved from each other, and, in some cases, have large shifts when Y is replaced by Sm, severial these modes can be assigned to definate vibrations. This and other aspects of the data are discussed.
Normal-State Infrared Anisotropy of Polycrystalline La1.85Sr0.15CuO4-y
Authors: Doll G. L. , Steinbeck J. , Dresselhaus M. S. , Dresselhaus G. , Strauss A. J. , Zeiger H. J. , Phillips G. , Waldman J. 
Published: March 2011

ABSTRACTBy examining the reflectance spectra of polycrystalline La1.85Sr0.15CuO4-y and La2NiO4-y in relation to the results of ir studies on single-crystal La2NiO4-y, we have determined the normal-state (room temperature) optical anisotropy of La1.85Sr0.15CuO4-y in the frequency range 40 cm-1 to 4800 cm-1. Vibrational and electronic properties corresponding to this anisotropy are examined, and a method is presented for extracting the optical properties of the superconducting state of La1.85Sr0.15CuO4-y.
Logarithmic Rounding Above the Superconducting Transition in YBa2Cu3O7 Crystals
Authors: Fiory A. T. , Hebard A. F. , Schneemeyer L. F. , Waszczak J. V. 
Published: March 2011

ABSTRACTThe temperature dependence of the electrical conductivity measured in the a-b basal plane of YB2Cu3O7 crystals displays a weak, nearly logarithmic divergence near Tc, which is weaker than the power-law functions predicted by superconducting fluctuations in 1, 2, or 3 dimensions. On the other hand, we find that quasi-particle fluctuations and pair-breaking in two-dimensions as given by Maki and Thompson, where the pair-breaking parameter δ is assumed to be proportional to temperature, gives by itself an excellent fit to the data.
Use of High-Temperature Superconductors in High Speed Electronic Switches with Current Gain
Authors: Biegel Bryan A. , Singh R. 
Published: March 2011

ABSTRACTRecent developments in superconductivity have taken 77 K superconducting electronics from a dream to a likelihood. Rather than following the conventional path by developing Josephson junction-based devices, this paper discusses the unique possibilities of hybrid superconductor/semiconductor devices. The two devices discussed are a true three-terminal hybrid resonant tunneling transistor and the semiconductor-coupled Josephson junction. Also, a list is given of as yet uninvestigated issues concerning the new superconductors and their proximity effects with semiconductors -issues that are critical to the operation of these hybrid superconductor/semiconductor devices.
Effect of Ambient Atmosphere on YBa2Cu3O7-y
Authors: Horowitz H. S. , Bordia R. K. , Flippen R. B. , Johnson R. E. 
Published: March 2011

The reactivity of sintered samples of YBa2Cu3O7-y with moisture at elevated temperatures has recently been reported [1]. The reaction sequence proposed was:Such instability of the 1–2–3 phase has serious implications regarding not only the use of the sintered material, but powder processing as well. While the need for fine particle 1–2–3 powder exhibiting good sinterability is recognized, it is also anticipated that the degradation of this material will accelerate with decreasing particle size because of the larger surface area. Thus, we have conducted a series of experiments to monitor the effect of ambient atmosphere on fine particle 1–2–3 powder. The powder was monitored as a function of time by x-ray diffraction, scanning electron microscopy, sintering characteristics and magnetic flux exclusion.
Implications of Donor Disseminated Intravascular Coagulation on Kidney Allograft Recipients
Authors: Wang Connie J. , Shafique Shahzad , McCullagh Johanna , Diederich Dennis A. , Winklhofer Franz T. , Wetmore James B. 
Published: March 2011

Summary

Background and objectives
Disseminated intravascular coagulation (DIC) is common in deceased kidney donors and is considered a relative contraindication to donation. The significance of donor DIC on recipient kidney function is poorly understood. Additionally, the significance of thrombocytopenia in recipients of kidneys from DIC-positive donors is understudied.

Design, setting, participants, & measurements
In a retrospective cohort of 162 kidney transplants, the presence of DIC in donors, the occurrence of thrombocytopenia in recipients, and risk factors for delayed or slow graft function (DGF/SGF) were assessed. The effects of DIC donor status on DGF/SGF in the study sample as a whole, and of thrombocytopenia on DGF/SGF in recipients of DIC-positive kidneys specifically, were examined using multiple logistic regression.

Results
DIC donor status was not associated with occurrence of DGF/SGF, but thrombocytopenia was significantly associated with DIC-positive donor status (P = 0.008). Thrombocytopenia was independently associated with DGF/SGF only in the recipients of DIC-positive kidneys (P = 0.005). Patient and graft survival at 1 year were not affected by donor DIC status or by thrombocytopenia status.

Conclusions
Donor DIC was not associated with short-term suboptimal graft function, defined as DGF/SGF, nor with long-term patient or graft survival. However, thrombocytopenia appears to portend DGF/SGF in recipients of DIC-positive kidneys and may be a clinical sign on which the basis of therapeutic decisions could be undertaken.
Preparation of electrospun titania nanofibers
Authors: Dong Hongying , He Xiaodong , Teng Yingyue , Song Fengyu , Ma Wen 
Published: March 2011

Abstract
In this study, titanium dioxide (TiO2) nanofibers with diameters ranging from 200–500 nm are successfully prepared via an electrospinning technique using a solution that contains polyvinyl pyrrolidone (PVP) and tetrabutyl titanate (TBT). Three key processing parameters are evaluated on the morphology of the fibers formed. Firstly, the PVP: TBT molar ratio is strongly correlated with the morphology of the fibers formed, and two extremes in the fiber morphology are observed as a result of varying the PVP: TBT molar ratio. Secondly, the electric field strength has been found to most strongly affect the fiber diameter, which increases as the electric field strength increases. Thirdly, the electrospun TiO2/PVP composite nanofibers are calcined at different temperatures. The process of removing organic components, the phase formation and the phase transition of the inorganic TiO2 are investigated using thermo-gravimetry–differential scanning calorimetry, infra-red and X-ray diffraction analyses.
Influence of oxygen partial pressure on the growth of Al-doped zinc oxide films by reactive MF magnetron sputtering
Authors: Hong Rui-jiang , Jiang Xin 
Published: March 2011

Abstract
Aluminum-doped zinc oxide thin films have been fabricated by reactive mid-frequency magnetron sputtering from Zn/Al metallic targets (Al 2 wt.%) with a dual magnetron (TwinMag™) configuration. The dependence of the structure, composition, electrical and optical properties of the films on the oxygen partial pressure has been investigated. It is shown that films with low resistivity and high optical transmittance could only be deposited under a narrow range of oxygen partial pressure. The film prepared at a partial pressure of 25 mPa exhibited highly c-axis oriented growth and a lowest resistivity of 4.6 · 10−4 Ω cm.
Phase equilibria studies in alumina-containing high zinc fayalite slags with CaO/SiO2 = 0.55 Part 1
Authors: Zhao Baojun , Hayes Peter C. , Jak Evgueni 
Published: March 2011

Abstract
The phase equilibria and liquidus temperatures in the ZnO–“FeO”–Al2O3–CaO–SiO2 system in equilibrium with metallic iron have been determined experimentally in the temperature range 1343 to 1553 K and for compositions relevant to a number of different non-ferrous smelting slags. The results are presented in the form of a pseudo-ternary section ZnO–“FeO”–(Al2O3 + CaO + SiO2) with CaO/SiO2 = 0.55 and (CaO + SiO2)/Al2O3 = 7.0. It was found that wustite and spinel are the major primary phases in the composition range investigated. Wustite (Fe2+, Zn)O and spinel (Fe2+, Zn)O · (Al, Fe3+)2O3 solid solutions are formed in this system, and the ZnO in slag partitions preferentially to the spinel phase.