bluuebunny/crossref_metadata_2025_split huggingface dataset:
Highly Oriented Very Low Surface Resistance Tl2Ba2Cu2O8 Films on NdGaO3 and LaAlO3
Authors: Holstein William L. , Parisi Louis A. 
Published: March 2011

ABSTRACTLow surface resistance epitaxial Tl2CaCu2O8 thin films were prepared on orthorhombic (001) NdGaO3 and pseudocubic (100) LaAlO3. The films were c-axis oriented on both substrates, with [100] Yl2Ba2CaCu2O8 parallel to [110] NdGaO3 or pseudocubic [100] LaAlO3. The orientation was particularly good on NdGaO3, where the rocking curve full width at half maximum was 0.19°. Films on LaAlO3 exhibit high Tc and exceptional microwave properties: inductive superconducting Tc of 106 ± 2 K, onset of flux exclusion at 107.6 ± 0.5 K, and 10 GHz surface resistance of 130 ± 20 μΩ at 77 K. These results represent the highest reported Tc of any Tl2Ba2CaCu2O8 films and the lowest surface resistance at 77 K of any films of any phase on any substrate reported to date. On NdGaO3, in spite of a substrate-film reaction, films with high Tc and good microwave properties were also produced: inductive Tc of 105 ± 2 K, onset of flux exclusion at 104.0 ± 0.5 K, and 10 GHz surface resistance at 77 K of 600 ± 100 μΩ.
Phase Relationships in ISO- and Aliovalent Analogues of La2CuO4: Implications for Superconductivity
Authors: Mccarron E. M. , Crawford M. K. , Harlow R. L. , Fameth W. E. 
Published: March 2011

ABSTRACTIn addition to the well known I4/mmm and Bmab phases, recent low temperature structural studies of certain T-type (K2NiF4-related) La2CuO4 analogues have revealed two additional structural modifications, one with Pccn and the other with P42/ncm symmetry. Via appropriate iso- and aliovalent substitution chemistry, regions of T-type phase field have been mapped out and the influence of these phase transitions on superconductivity studied.
Magnetic Alignment of Amorphous Coatings of GD:123
Authors: McKittrick Joanna , Contreras Ramiro 
Published: March 2011

ABSTRACTHigh Tc superconducting Gd-Ba-Cu-O materials were synthesized via the acetate precursor process. Aqueous solutions of < 0.6 M of metal cations were applied to substrates of yttria stabilized zirconia. Homogeneous films were applied to the substrates by use of the spin coating technique. The substrates were fired in air at 500°C in between each applied coat. After coating the substrates with 10–30 coats, they were crystallized by heating to 900°C in Ar or O2 with or without a 1 T magnetic field. The applied magnetic field was found to produce c-axis alignment for the thinner coats. Annealing in argon produced alignment but the effect was less pronounced than annealing in oxygen. Substrates with 30 coats were not aligned for either environment.
Transport Study on Overdoped TlBa2CUO6+δ Single Crystal
Authors: Manako Takashi , Shimakawa Yuichi , Kubo Yoshimi 
Published: March 2011

ABSTRACTTl2Ba2Cuo6+δ(T1-2201) single crystals are prepared by a KCI flux method. In-plane and out-of plane resistivities (ρabρc as well as the in-plane Hall coefficient are measured for the single crystal samples with various 7c's. The ρc values are as large as ∼10−1 Ω cm, which is larger than that of YBa2Cu3O7, but smaller than that of Bi2Sr2CaCu2O8. Temperature dependences of ρc show metallic behaviors for both normal metallic and 75-K superconducting samples. Temperature dependence of in-plane resistivity par changes from ∼T2 to ∼T1 with increasing Tc In-plane Hall coefficient RH shows a characteristic maximum at about 100 K for all samples. Although both ρab and RH have rather a complicated temperature dependence, inverse Hall mobility μH(=ρab/RH always exhibits clear T2 dependence for all samples. These results suggest that the intrinsic scattering rate of this material varies as ∼T2, just like in an ordinary Fermi liquid, and that the carrier concentration actually changes with temperature like that observed in nH(=1/RHe).
Off-Axis Growth of Y1Ba2Cu3O7-y on Different Substrates
Authors: Broussard P. R. , Cestone V. C. , Allen Laura H. , Reeves M. E. 
Published: March 2011

ABSTRACTFilms of Y1Ba2Cu3O7-y have been grown by off-axis DC sputtering onto substrates of (100) SrTiO3. LaAlO, LaGaO3, Yttria-stabilized Zirconia, and MgO. Our best films, grown on SrTiO3 substrates at a temperature of 650°C and a sputtering pressure of 100 mTorr (consisting of 80 mTorr Ar and 20 mTorr O2) have room temperature resistivities of 280 μΩ-cm, an inductive Tcof 88 K and an inductive Jc 'Sof∼ 2.6 × 106 A/cm2 at 77 K and 3.9 × 107 A/cm2at 4.2 K. Films grown on YSZ tend to have higher resistivities (∼ 600 μΩ-cm) but still have Tc's of 86 K and Jc's of - 106 A/cm2 at 77 K. Films down to 550 Å still have Tc's of 86 K and Jc's at 77 K > 106 A/cm2. Films grown at lower temperatures (600°C) on S1TiO3 begin to show a-axis growth, but the superconducting properties deteriorate.
Mechanical Behaviors of Flux Pinning in GdxY1−x-Ba2Cu3Oy
Authors: Zhu J. S. , Li J. , Lu X. M. , Jin X. , Gu M. , Wang Y. N. 
Published: March 2011

ABSTRACTThe mechanical behaviors of flux pinning in GdxY1−xBa2Cu3Oy with various concentration of Gd were studied comparatively by means of a vibrating reed technique. Both the internal friction and the modulus increased with enhanced flux pinning due to the increasing of Gd content in GdxY1−xBa2Cu3Oy. It was in accordance with the results of the magnetic hysteresis measurements using a vibrating sample magnetometer. These results indicated that the substitution of magnetic rare-earth ions is a practicable method for improving the flux pinning in high Tc superconductor and the mechanical measurement of flux pinning as a judgement for the superconductivity of sample was proved.
Grain Boundary Weak Links in High-TC Superconductors
Authors: Shi Donglu , Sengupta S. , Goretta K. C. , Salem-Sugui S. , Smith M. , Lwin Y. N. 
Published: March 2011

ABSTRACTThe transport critical current density (Jc) for high-Tc thin films, bicrystals, and bulk ceramics is shown to be determined by magnetic field penetration into the grain boundaries. The gross grain orientations may not in all cases be an important factor in determining this penetration. The parameter (λG/λj)2can characterize the strength of the grain boundary coupling, which depends mainly on the crystal coherence and connectivity at the boundary area.
The Single Phase Regions and the Phase Stability of the High-Tc Superconducting Compounds Bi2+x(Sr,Ca)3Cu2O8+d (2212) and Bi2−x(Sr,Ca)4Cu3O10+d (2223)
Authors: Majewski Peter , Hettich Bernhard 
Published: March 2011

ABSTRACTThe 2212 phase exhibits an extended single phase region having a variable Sr/Ca ratio and Bi-content of 2.1 < Bi < 2.3. At T = 820°C the single phase region extends between 2.05/0.95 > Sr/Ca > 1.2/1.8, whereas, at T = 870° C the single phase region extends between 2.2/0.8 > Sr/Ca > 1.6/1.4. The 2223 phase exhibits a significant higher Bi-content of Bi ∼ 2.5 compared to the formal composition Bi2Sr2Ca2Cu3O10. The Sr/Ca ratio varies between 2/2 > Sr/Ca > 1.9/2.1 reffering to Cu-content of Cu = 3. Samples with the nominal composition Bi2.5Sr2Ca2Cu3Ox and Bi2.5Sr1.9Ca2.1Cu3Ox have been sintered at 880 – 885°C for 90 h in air and consist of 90 – 95 volume percent 2223 phase. Tc depends on the chemical composition of the phases. With decreasing Ca- and Bi-content of the phases Tc increases. Both phases are metastable at roomtemperature. 2212 and 2223 rapidly decompose at 600 °C and 800 °C in air, respectively. At 300°c two new Bi-Sr-Cuprates have been found.
Post Sintering Oxygen Pressure Effects on the Jc of BPSCCO- Silver Clad Tapes
Authors: Lay K W 
Published: March 2011

ABSTRACTMany processing parameters affect the critical current of silver-clad tapes of Bi2−xPbxSr2Ca2Cu3O10+y (2223) made by the powder in tube process. In this paper the effect of oxygen pressure during cooling from the final sintering step will be considered. It is shown that high oxygen pressures will destabilize the 2223 phase with formation of calcium plumbate and the lower Tc Bi2Sr2Ca1Cu2O8+y (2212) phase. This decomposition can drastically lower the critical current. It is shown that cooling in atmospheres containing about 5 % oxygen will avoid the calcium plumbate formation region.
New Layered Perovskite Vanadium Oxide with Negative Magnetization
Authors: Fukushima Noburu , Takeno Shiro , Tanaka Shigenori , Ando Ken 
Published: March 2011

ABSTRACTA new layered perovskite vanadium oxide Sr4V3O8-d was synthesized and its crystal structure and magnetic properties were studied. Sr4V3O8-d has a novel crystal structure, containing a V-0 octahedron and a two-fold V-0 fence in a unit cell. It exhibits negative magnetization below 30 K. when cooled in a magnetic field. This peculiar magnetism is attributed to N-type parasitic ferrimagnetism.
Electrical Characteristics of All-Oxide S-N-S Junctions in the Normal State
Authors: Tarutani Y. , Hiratani M. , Fukazawa T. , Kabasawa U. , Tsukamoto A. , Suga M. , Takagi K. 
Published: March 2011

ABSTRACTAll-oxide S-N-S (superconductor-normal layer-superconductor) junctions having a planar structure are fabricated and their electrical characteristics in the normal state are investigated. The superconducting electrodes are composed of HoBa2Cu3O7−x, and the normal layer is La1.5Ba1.5Cu3O7-y. Conductance characteristics are measured and their behaviors are explained by the geometrical resonance of quasiparticles. A pair potential distribution in the normal layer is estimated from the resonance structure.
Microstructures of YBCO Thin Films Prepared by Pulsed Organometallic Beam Epitaxy
Authors: Hu J. G. , Miller D. J. , Buchholz D. B. , Duray S. J. , Schulz D. , Marl T. J. , Chang R. P. H. 
Published: March 2011

ABSTRACTThe microstructure of Y1Ba2Cu3Oy films and Y1Ba2Cu3Oy / Pr1Ba2Cu3Oy multilayers prepared by a pulsed organometallic beam epitaxy (POMBE) technique have been characterized by transmission electron microscopy (TEM). The microstructure of the films is observed to vary as a function of substrate temperature. At low temperatures, films are polycrystalline and exhibit some impurity phases. At higher substrate temperatures, films grow epitaxially with smooth surfaces and few impurities. Controlled growth at sufficiently high substrate temperatures allows uniform growth of alternating Y1Ba2Cu3Oy and Pr1Ba2Cu3Oy layers.
Ba1−xKxBiO3 Superconducting Crystals with New Solubility Limit
Authors: Tang H. Y. , Chen W. L. , Wen W. J. , Wu M. K. , Norton M. L. 
Published: March 2011

ABSTRACTCrystalline bismuthates Ba1−xKxBiO3 with x greater than 0.5 are obtained by a low temperature anodic electrocrystallization method in a potassium hydroxide molten flux. The x = 0.56 bismuthate crystal shows 8K superconductivity determined by AC magnetic susceptibility.
Development of Tailored Films and Surfaces for Use in Advanced Chemical Sensors
Authors: Semancik Steve , Cavicchi Richard 
Published: March 2011

ABSTRACTThe microstructure found at the surfaces and interfaces of active sensing materials can strongly affect the performance of solid state chemical sensors. This paper desribes research efforts aimed at improving oxide semiconductor-based gas sensors which utilize changes in conductance and diode current-voltage measurements as detection schemes. Studies of oxide surface modification and the formation of Pd/SnO2(110) and Pd/TiO2(110) interfaces are discussed as are the electrical changes for these systems induced by H2 or O2 adsorption. The fabrication of heteroepitaxial SnO2 films for use in planar sensing arrays is also reported and the expected advantages of these highly-ordered, uniform films for simplifying the transducing process are described.
Micron Sized Arm Using Reversible TiNi Alloy Thin Film Actuators
Authors: Kuribayashi Katutoshi , Taniguchi Takao , Yositake Masaaki , Ogawa Sooichi 
Published: March 2011

ABSTRACTReversible TiNi (= RTiNi) alloy thin film actuator has many advantages for micro sized robot. That is. a micro arm could be fabricated easily on silicon wafer because RTiNi alloy thin film has 3 functions. 1) a frame of the arm, 2) a joint of the arm and 3) an actuator of the arm. and moreover, this film could actuates the arm without friction. A micron sized flexible arm using RTiNi alloy thin film was designed on silicon wafer. IC process for fabricating this arm on silicon wafer was designed. The fabricating process for this arm and its heat treatment process for the RTiNi are presented.
Microheater Made of Heavily Boron Doped Single Crystal Silicon Beam
Authors: Kimura Mitsuteru , Komatsuzaki Kazuhiro 
Published: March 2011

ABSTRACTMicroheater made of heavily Boron doped single crystal Si beam covered with SiO2 film, 1000×300×3 μm, is fabricated on the n type Si substrate by the anisotropic etching technique. As this microheater has an air bridge structure of low resistivity semiconductor material with positive but small temperature coefficient of resistance, a broad heating area up to 800 °C is easily obtained and it has quick response with the thermal time constant t of about 4 ms and has small power consumption. Since this heating area is made of p type layer in the n type substrate,this area can be electrically isolated from the substrate because of the formation of p-n junction.
Organic Polymers with Tunable Charge Carrier Mobilities
Authors: Stolka Milan , Abkowitz Martin A. 
Published: March 2011

ABSTRACTCharge carrier (hole) mobility in amorphous organic polymeric materiats can be changed at will over at least nine orders of magnitude without increasing the conductivity of the polymers, and also without affecting the carrier range, i.e., without introducing deep traps. The changes in the drift mobility can be accomplished by several means: (1) by changing the density of hopping sites (the concentration of transport-active molecules or groups), (2) by light doping the host polymer with low-oxidation potential compounds (for hole transport), and, eventually, (3) by the nature of the host medium and its polarity. Since the carrier mobility is typically activated and electric field dependent, significant changes can also be made by varying the temperature and the electric field. An enhancement of mobility by heavy doping has also been described. Hole mobilities in the small molecule - host polymer composites and also in polymers in which the transport states are backbone-derived can thus be varied from values below the measurement threshold (<10−10 cm2 V− s−1) to fairly high values in the neighborhood of 10−1 cm2 V−1 s−1 at an electric field of E = 105 V cm−1 and at 295 K.
Integrated Linear and Nonlinear Optics with Novel Macromolecular Systems
Authors: Aust E. F. , Hickel W. , Meyer W. H. , Ringsdorf H. , Sawodny M. , Urban C. , Wegner G. , Knoll W. 
Published: March 2011

ABSTRACTThis paper deals with the application of some recently developed evanescent waveoptical techniques for the characterization of novel macromolecular host-guest systems. In particular, surface plasmon- and guided optical wave-spectroscopies and -microscopies are used to determine the linear and nonlinear optical properties of these materials in thin film form.
Preparation and Third-Order Nonlinear Optical Properties of Host-Guest Molecular Composites
Authors: Jenekhe Samson A. , Roberts Michael F. , Meth Jeffrey S. , Vanherzeele Herman 
Published: March 2011

ABSTRACTHost-guest molecular composites of conjugated rigid-rod polymers in the matrix of flexible-chain polymers were prepared from blend solutions of the Lewis acid complexes of the component polymers. Molecular composites of poly(p-phenylene benzobisthiazole) (PBZT) with the polyamides Nylon 66 and PTMHT were prepared and their linear and nonlinear optical properties were investigated by optical absorption and third harmonic generation spectroscopy, respectively. Dispersion of PBZT in a polyamide matrix was found to result in reduced π-electron interactions as evidenced by the narrowing of the main absorption band. The χ(3) spectra of composites were measured in the wavelength range 0.8–2.4μm which spans the resonant and nonresonant regions. Nonresonant χ(3) at 1.9μtm was studied as a function of composite composition and linear and nonlinear dependences of χ(3) with mole fraction of PBZT were observed for nylon 66 and PTMHT composites respectively. Our findings that both χ(3) and χ(3)/α can be enhanced in molecular composites suggest that this is an important approach to optimize materials for nonlinear optics. Preliminary results of our studies of other new molecular composites of rigid-rod and ladder polymers are also discussed.
Simulation and Modeling of Amorphous Silicon Thin-Film Devices
Authors: Shaw John G. , Hack Mike G. 
Published: March 2011

AbstractWe describe a computer program which solves the complete set Of transport equations for device-quality amorphous silicon in two spatial dimensions and time. When modeling amorphous silicon devices, it is extremely important to account for the high concentration of time-dependent trapped charge present due to the continuous distribution of localized states in the semiconductor's bandgap. Our model is based on a realistic density-of-states distribution and includes a detailed description of the trap occupation functions for electrons and holes. These occupation functions are calculated self-consistently with respect to the electrostatic potential and free-carrier concentrations within the semiconductor.
Dislocation Generation and Crack Propagation in Metals Examined in Molecular Dynamics Simulations
Authors: Rifkin J. A. , Becquart C. S. , Kim D. , Clapp P. C. 
Published: March 2011

AbstractWe have carried out a series of atomistic simulations on arrays of about 10,000 atoms containing an atomically sharp crack and subjected to increasing stress levels. The ordered stoichiometric alloys B2 NiAl, B2 RuAl and A15 Nb3AI have been studied at different temperatures and stress levels, as well as the elements Al, Ni, Nb and Ru. The many body interactions used in the simulations were derived semi-empirically, using techniques related to the Embedded Atom Method. Trends in dislocation generation rates and crack propagation modes will be discussed and compared to experimental indications where possible, and some of the simulations will be demonstrated in the form of computer movies.
Kinetic Roughening in Surface Growth
Authors: Yan Hong , Kessler David A. , Sander Leonard M. 
Published: March 2011

AbstractIn nonequilibrium surface growth processes, such as molecular beam epitaxy and chemical vapor deposition, kinetic roughening plays a significant role in determining surface morphology. The stochastic dynamics in the processes induce novel scaling in surface roughness with respect to growth time and system sizes. We present here a series of numerical simulation studies of simple theoretical models, such as ballistic deposition model and biased solid-on-solid model, to demonstrate the dynamical scaling and phase transitions in a class of surface growth problems in the context of the Kardar-Parisi-Zhang theory. Different dynamical processes, such as desorption and surface diffusion, are shown to have dramatic effects on the scaling and thus the surface structures.
Electronic Structure of Substitutionally Disordered Alloys: Direct Configurational Averaging
Authors: Wolverton C. , Fontaine D. De , Dreysse H. , Ceder G. 
Published: March 2011

AbstractThe method of direct configurational averaging (DCA) has been proposed to study the electronic structure of disordered alloys. Local density of states and band structure energies are obtained by averaging over a small number of configrations within a tight-binding Hamiltonian. Effective cluster interactions, the driving quantities for ordering in solids, are computed for various alloys using a tight-binding form of the linearized muffin-tin orbital method (TB-LMTO). The DCA calculations are used to determine various energetic and thermodynamic quantities for binary and ternary alloys.
A First-Principles Study of the Phase Stability of FCC-Based Ti-Al Alloys
Authors: Asta Mark , Fontaine Didier De , Schilfgaarde Mark Van , Sluiter Marcel , Methfessel Michael 
Published: March 2011

AbstractIn this paper we present results of a first-principles phase stability study of fcc-based Ti-Al alloys. In particular, the full-potential linear muffin tin orbital method has been used to determine heats of formation and other zero-temperature properties of 9 fcc ordered superstructures as well as fcc and hcp Ti, and fcc Al. From these results a set of effective cluster interactions are determined which are used in a cluster variation method calculation of the thermodynamic properties and the composition-temperature phase diagram of fcc-based alloys.
Interatomic Interactions for BCC Metals Based on the Low Order Moments of the Density of States
Authors: Foiles Stephen M. 
Published: March 2011

AbstractA model of the energetics of bcc transition metals based on the low-order moments of the electronic density of states is presented. The new feature of the model is an additional energy term related to the fourth moment of the density of states. This term reflects the coarse shape of the density of states. The model is tested by the computation of point defect properties, phonon dispersions, structural energy differences and surface properties. The results are compared to experiment, ab-initio calculations and other model interatomic potentials. The results indicate that the inclusion of the fourth moment term in the energy does not significantly improve the description of properties of the bulk bcc metals. However, the fourth moment term substantially improves the description of large deviations from the bcc bulk such as surfaces and alternative crystal structures.
Properties of Complex Materials: A Computer Aided Structural Classification
Authors: Pascale Teresa M. de , Meloni Franco , Serra Marina 
Published: March 2011

AbstractWe discuss the validity of the usually used orbital radii capable to separate differently coordinated compounds in efficient structural maps. In order to account for the real dependence on the angular momentum, we redefine the atomic terms by including the d-states contribution, previously ignored. The choice of the right amount of the correction has been performed thanks to a series of structural maps obtained through a computer-aided code.
Topological Stability of 2-D Vanishing Grains
Authors: Fradkov V. E. , Glicksman M. E. , Nordberg J. , Palmer M. , Rajan K. 
Published: March 2011

AbstractGrain growth in polycrystals occurs by decreasing the total number of grains as a result of the disappearance of small ones. That is why the both the kinetic and topological details of shrinking of small grains are important.In 2-D, “uniform boundary model” assumptions imply the von Neumann-Mullins law, and all grains having less than 6 neighbors tend to shrink. The mean topological class ef vanishing grains was found experimentally to be about 4.3. This result suggests that most vanishing grains are either 4- or 5-sided, not transforming to 3-sided ones.Shrinking of 4- and 5-sided 2-D grains was studied experimentally on transparent, pure SCN, (succinonitrile) polycrystalline films and by direct computer simulation of grain boundary capillary motion together with triple junctions. It was found that the grains which are much smaller than their neighbors are topologically stable.
Molecular Dynamics Modeling of Polymer Flammability
Authors: Nyden Marc R. , Brown James E. , Lomakin S. M. 
Published: March 2011

AbstractMolecular dynamic simulations were used to identify factors which promote char formation during the thermal degradation of polymers. Computer movies based on these simulations, indicate that cross-linked model polymers tend to undergo further cross-linking when burned, eventually forming a high molecular weight, thermally stable char. This prediction was confirmed by char yield measurements made on γ and e - irradiated polyethylene and chemically cross-linked poly(methyl methacrylate).