bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tailored High-Tc Superconducting Thin Films Prepared by Layer-By-Layer Deposition with Excimer Laser
Authors: Kawai Tomoji , Kanai Masaki , Tabata Hitoshi , Kawai Shichio 
Published: March 2011

AbstractBy using 1ayer-by-1ayer successive deposition method with excimer laser ablation, the distance between CuO2 planes in the Bi2Sr2Ca1Cu2Oy superconductor has been controlled and super lattices with concentration modulation of Y and Ca have been formed. From the properties of these ‘Tailored films’, it is suggested that there is an interaction between CuO2 layers across Ca layer to affect the Tc value, but there is a very weak interaction across Bi2O2 blocking layers.
Fabrication of Yy‐Pr1‐y ‐Ba‐Cu‐O Thin Films and Superlattices of ‐Ba‐Cu‐O/Yy‐Pr1‐y ‐Ba‐Cu‐O
Authors: Wu X. D. , Hegde M. S. , Xi X. X. , Li Q. , Inam A. , Schwarz S. A. , Martinez J. A. , Wilkens B. J. , Barner J. B. , Chang C. C. , Nazar L. , Rogers C. T. , Venkatesan T. 
Published: March 2011

AbstractWe have prepared epitaxial thin films of Yy‐Pr1‐y‐Ba‐Cu‐O (y= 1 to 0) and superlattices of Y‐Ba‐Cu‐O/Yy‐Pr1‐y ‐Ba‐Cu‐O using pulsed laser deposition technique. The zero resistance transition temperatures of Yy‐Pr1‐y‐Ba‐Cu‐O bulk samples are reproduced in the films. The composition oscillations in the superlattices are observed by SIMS. The films and superlattices are found to have c‐axis orientations and good crystallinity.
Superconducting and Semiconducting Thin films of La123 and123 and their Superlattices
Authors: Ganapathi L. , Kumar Ashok , Narayan J. , Holland O. W. 
Published: March 2011

AbstractThin films of La123 and their superlattice with Y123 are deposited on various substrates for the first time. Thin films of La123 can be made semiconducting or superconducting within a small range of oxygen stoichiometry. A multiple target holder has been used for insitu processing of superlattice thin films. The ability of the La123 compound to exhibit either semiconductivity or superconductivity has been utilized to construct semiconductor / superconductor superlattice structures with Y123- X-ray diffraction studies have shown clearly the presence of two distinct type of layers in the superlattice films with a individual layer thickness of ∼ 120 and 300 Å, although this did not happen for ∼ 24 Å thickness of the individual layers. Rutherford backscattering experiments showed good quality of the films with channeling yields < 10%. Resistivity measurements showed a Tc (onset) = 90 K and Tc(zero) = 85 K for the La123 as well as superlattice thin films.
Ion Beam Thinning of YBa2cu3o7 Films: Approach to a Limiting Thickness for Superconductivity of One Lattice Constant
Authors: Hebard A.F. , Eick R. H. , Siegrist T. , Coleman E. 
Published: March 2011

AbstractGrazing angle ion-beam milling of c-axis oriented YBa2Cu3O7 films is shown to give smooth films which have metallic-like resistance transitions and superconduct at thicknesses approaching a lattice constant. The zero resistance transition temperature decreases uniformly with increased milling with most of the change occurring for thicknesses less than 100Å. The crossover to non-superconducting behavior occurs at “electrical” thicknesses near 10 Å with a sheet resistance above the onset of the superconducting transition having a value near h/4e2 = 6450Ω, a combination of fundamental constants predicted by theory and observed previously in low-Tc superconductors. Continued milling beyond this limit results in semiconducting behavior without a superconducting transition.
As‐Deposited Superconducting Y‐Ba‐Cu‐0 Films on GaAs Substrate by High Pressure Dc Sputtering Process
Authors: Lin R.J. , Lin Y.L. , Pan F.M. , Wu P.T. 
Published: March 2011

AbstractSuperconducting Y‐Ba‐Cu‐0 thin films on (100)GaAs substrate have been successfully prepared by the high pressure DC sputtering process without further post‐annealing treatment. The target was compound Y1Ba2Cu3Ox made by solid‐state reaction. The sputtering gas was Ar‐50%02, and total pressure was 1.5 torr. The substrate temperature was lower than 450°C. The best superconductivity of the film is Tc(onset) = 95K and Tc(R=0) = 40K. There are no mi‐crocracks on the film surface. The interdiffusion between the film and GaAs is limited.
Superconducting Yba2Cu3O7-δ Thin Films on Srtio3 and Si Grown In-Situ by Ion Beam Sputtering
Authors: Kellett B.J. , James J.H. , Gauzzi A. , Affronte M. , Pavuna D. 
Published: March 2011

AbstractSuperconducting YBa2Cu3O7‐δ (YBCO) films 100‐300nm thick have been grown in‐situ on (100) SrTiO3 at 650°C by ion beam sputtering. Targets of Cu, CuO, Y, Y2O3, BaF2, BaCO3 and YBa2Cu3O7‐δ have been studied. Uniform composition throughout the film thickness has been achieved by co‐sputtering. Films are metallic (p300=300μΩcm) and textured, with Tc onsets at 92K and Tco=82K. Jc(77K) exceeds 105 Acm‐2. Films grown in‐situ on Si with ZrOx/Y2O3 and In2O3(10 at.%SnO2) buffer layers show Tc onsets at about 90K and Tco at about 50K, annealing improves Tco to 60K with resistivities p30o=2000μΩcm and 4000μΩcm respectively.
The Effect of Annealing Conditions on Magnetron Sputtered Superconducting Tl-Based Thin Films
Authors: Liou S.H. 
Published: March 2011

AbstractThe annealing steps have been shown to be a crucial determinant of the quality of Tl‐based superconducting films. In this study, we discuss the formation of the superconducting Tl2Ba2CaCu2O8 and Tl2Ba2Ca2Cu3O10 phases with varied post‐annealing temperature and fixed annealing time. A x‐ray, electron micro‐probe, and scanning electron microscopy were carried out to evaluate the structure of superconducting phases formed for each annealing condition. For films deposited on SrTiO3 substrates and heat‐treated at 870°C for 15 min, the lower Tc phase Tl2Ba2CaCu2O8 becomes a major phase. The films consist of nearly pure Tl2Ba2Ca2Cu3O10 phase with Tc (R=0) in the range of 100K to 118K and c‐axis perpendicular to the film plane were obtained after annealing 880‐890°C for 15 min. These films were epitaxy growth on SrTi03 substrates.
In-Situ Preparations and Properties of High Tc Ybco Poly-Crystalline Thin Films
Authors: Harada N. , Sato K. , Yamamoto K. 
Published: March 2011

AbstractHighly oriented YBCO films were produced on MgO(100) single crystal substrates. The direction of c axis was perpendicular to the film plane, whereas those of a and b axes were at random directions. The critical current density of the films was significantly high ca. 7x105 A/cm2. The critical transition temperature (Tc) of the YBCO film formed on a metal substrate, predeposited with YSZ as a buffer layer, was similar to those of the YBCO on MgO substrate. The possibility for the formation of superconductor films on metal substrates is suggested from these results.
In‐Situ Growth of Superconducting Bi‐Sr‐Ca‐Cu‐O Thin Films by Activated Reactive Co‐evaporation
Authors: Yoshikawa K. , Satoh T. , Sasaki N. , Nakano M. 
Published: March 2011

AbstractThe effect of in‐situ cooling conditions on surface roughness and superconducting properties have been studied. Bi‐Sr‐Ca‐Cu‐0 thin films were grown in‐situ on (100) MgO substrates at 700°C by activated reactive co‐evaporation. The films cool‐down in 760 Torr oxygen showed a transition temperature (Tc(onset)) of 100 K and zero resistance temperature (Tc (zero)) of 65 K. Smooth surface was obtained for the sample cooled‐down in oxygen plasma.
Molecular Beam Epitaxy of Rubidium Barium Bismuth Oxide: Structural Phenomena in Perovskite Heteroepitaxy
Authors: Hellman E. S. , Hartford E. H. , Werder D. J. , Fleming R. M. 
Published: March 2011

AbstractThe simple cubic perovskite crystal structure of superconducting (Rb,Ba)BiO3 makes it an ideal system for the study of perovskite heteroepitaxy. We report novel growth phenomena which have been observed in (Rb,Ba)BiO3 films grown by molecular beam epitaxy (MBE). For growth on MgO, the orientation of the film is observed to depend on the substrate temperature during growth, changing from (1 1 0) to (1 0 0) with increasing temperature. For films on SrTiO3, the large (10%) lattice mismatch appears to cause small grain rotations, resulting in a film with many low angle grain boundaries. In at least one growth regime, (2 2 1) oriented grains nucleate and grow on Ʃ3 coincidence boundaries on a faceted (1 0 0) oriented film.
Highly Oriented Superconducting Bi ‐ Sr ‐ Ca ‐ Cu ‐ Oxide Thin Films by the Solution Sol ‐ Gel Process
Authors: Ravindranathan P. , Komarneni S. , Bhalla A. S. , Roy R. 
Published: March 2011

AbstractHighly oriented Bi2Sr2CaCu2O8+x films were prepared on MgO and SrTiO3 substrates by the solution sol ‐ gel (SSG) method. The tetra phasic sol containing bismuth, strontium, calcium and copper oxides was coated on the substrate by spin casting and calcined at 870*C for 10 minutes. X‐ ray diffraction patterns of the films showed the formation of the superconducting phase with preferential orientation along the C‐ axis. The microwave absorbtion data as a funtion of temperature revealed the onset temperature to be 90*K for the film coated on MgO substrate.
Preliminary Investigation of Processing and Phase Diagram Construction in the Y‐Sr‐Cu‐O System
Authors: Rolin T. D. , Cheng F. S. , Ashburn J. R. , Cheng H. Y. , Anderson E. E. 
Published: March 2011

AbstractWe have investigated the Y‐Sr‐Cu‐O system which has been reported to form a K2NiF4‐type superconducting phase (TC∼40K) and a “123”‐type phase (Tc‐80K). Difficulties in preparing single phase materials by standard solid state reaction of carbonates and oxides have compelled us to explore other methods. A two‐stage solid state processing technique in addition to a coprecipitation method will be discussed along with the relative advantages and disadvantages of each. Using data obtained from XRD and EDS, we have mapped some of the YO1.5‐SrO‐CuO ternary phase diagram in anticipation of continued efforts at single crystal growth.
Microstructure and Properties of Mixed Yba2Cu3O7-X and Y2Ba4Cu8O16 Thin Films
Authors: Marshall A.F. , Kapitulnik A. , Char K. , Barton R.W. 
Published: March 2011

AbstractPost-annealed thin films comprised of mixed YBa2Cu3O7-x (123) and Y2Ba4Cu8O16 (248) phases with both faulted and unfaulted microstructures have been characterized by planar and cross-section transmission electron microscopy. The influence of 248-type faults on the 123 structure, possible mechanisms for the higher Tc's of faulted films, and observations of a fourfold ordered structure are discussed.
Structural and Magnetic Properties of Untwinned Yba2Cu3O6+x Single Crystals
Authors: Kaiser Debra L. , Gayle Frank W. , Swartzendruber Lydon J. , Wong-Ng Winnie , Watkins Steven F. , Fronczek Frank R. 
Published: March 2011

AbstractWe have conducted structural and magnetic investigations on thermomechanically-detwinned YBa2Cu3O6+x single crystals. Single crystal x-ray diffraction studies on a fully untwinned crystal with a superconducting onset temperature of 54 K have revealed that oxygen atoms in the basal plane are offset from the crystallographic mirror plane in the a direction, leading to “zig-zag” Cu-O chains. Magnetic measurements on untwinned and twinned crystals at 77 K indicate low levels of flux pinning in both crystals, with a slightly larger amount of pinning in the twinned crystal.
Orthorhombic Splitting and Chemical Etching of Ba2Ycu3O7-δ Crystal Surfaces
Authors: Werder D. J. , Chen C. H. , Gurvitch M. , Miller B. , Schneemeyer L. F. , Waszczak J. V. 
Published: March 2011

AbstractWe find by transmission electron diffraction (TED) that the orthorhombic splitting of the upper surface layers (< 1 μm) of single crystal Ba2YCu3O7-δ(YBCO) is reduced, differing by 10 to 30 percent from the bulk value. We also find by transmission electron microscopy (TEM) that in general the surfaces are of inferior quality, and thus, not representative of the bulk. These results have important consequences for those experiments that probe only the upper surface layers. By etching with either Br/ethanol or HClO4/NaClO4 the poor quality surfaces can be removed.
Grain Boundary Modelling and Correlation with Critical Current Densities in High‐Tc Superconductors
Authors: Jagannadham K. , Narayan J. 
Published: March 2011

AbstractGeometrical modelling of grain boundaries in 123‐YBaCuO and 2223‐TlBaCaCuO systems is carried out for several misorientat‐ions. The a‐b and the a‐c type coincidence boundaries are analyzed to determine the fraction of Cu‐O planes that are continuous and the excess charge present at the boundary voids. The interg‐rain critical current density is determined as a function of the misorientation and the width of the boundary. The tunneling of superconductor pairs through the regions of distortions, giving rise to depression of the order parameter at the boundaries,is used to determine the critical current density in the weak coupling limit.
In-Situ Transmission Electron Microscopy and Computer Simulation Study of the Kinetics of Oxygen Loss in Yba2Cu3OZ
Authors: Burmester C. P. , Wille L. T. , Gronsky R. , Ahn B. T. , Lee V. Y. , Beyers R. , Gür T. M. , Huggins R. A. 
Published: March 2011

AbstractHigh resolution transmission electron microscopy during in‐situ quenching of YBa2Cu3Oz is used to study the kinetics of microdomain formation during oxygen loss in this system. Image simulations based on atomic models of oxygen‐vacancy order in the basal plane of this material generated by Monte Carlo calculations are used to interpret high resolution micrographs of the structures obtained by quenching. The observed domain structures agree well with those obtained from the simualtions.
Superconducting Phases and Modulated Structures in (Bi, Pb)-Sr-Ca-Cu-O Wires
Authors: Feng Y. , Smallman R. E. , Jones I. P. , Wellhofer F. , Alford N. Mcn. , Button T. W. 
Published: March 2011

Abstract(Bi, Pb)-Sr-Ca-Cu-O ‘2223’ wires with varying Bi/Pb ratios and sinter times have been investigated by parallel physical measurements and analytical electron microscopy. The numbers of phases present, their relative amounts, compositions and structures are reported and correlated with the superconducting properties. In particular, the recently reported long period (010) modulation (2b*/q*=7.7) is found to be connected with the “2223” high Tc phase.
Crystal Chemical and Functional Representation of High‐Tc Superconductors and Related Phases
Authors: Sigalovsky J. , Giessen B.C. 
Published: March 2011

AbstractUsing crystallographic data on HTSC's and a recently developed description of many HTSC's as intercalation compounds, we review briefly the structural evidence and develop some structural correlations involving the dimensions, coordination and connectivities of functional units.
In‐Situ Patterning and Critical Current Density Measurements in Laser Deposited High‐Tc Superconducting Thin Films
Authors: Singh R. K. , Lee C. B. , Tiwari P. , Narayan J. 
Published: March 2011

AbstractWe have performed transport critical current density, Jc, measurements on epitaxial superconducting thin films which were in‐situ patterned during the laser deposition process. Shadow masks of various dimensions were placed close to the substrate to generate different patterns. Epitaxial films of YBa2Cu3O7 on (100) SrTiO3, (100) YSZ, and (100) LaA1O3 substrates were fabricated at low processing temperatures (500‐650°Q by the biased laser deposition technique in an oxygen ambient of 200 mtorr. Excellent quality superconducting thin films were formed on patterned areas. The critical temperature of the films was found to be in the range of 88 to 90 K, and the best critical current density values (at 77K, and zero magnetic field) greater than 6.5 x106 Amps/cm2 were obtained for silver doped YBa2Cu3O7 films on (100)LaAlO3 substrates.
Macroscopic Persistent Currents in Laser Ablated YBa2Cu3O7-X Films
Authors: Stritzker B. , Leiderer P. , Feile R. , KrÜGer U. , Zander W. 
Published: March 2011

AbstractThin films of YBa2Cu3O7-x have been produced in situ by laser ablation. As the condensation of the superconducting film is done onto hot substrates (600 - 780°C) at high oxygen pressures (~ 1 mbar), this techniques does not require any special postannealing step. Thus the total process time amounts to less than 10 min. Films were found to be polycrystalline with the c-axis preferentially oriented normal to the substrate plane on single crystalline (001) SrTiO3 and (random) ZrO2, as measured by ion channeling (Xmin = 5.5 % on SrTiO3), x-ray scattering and TEM. Complete superconducting transitions above 90 K with transition widths of about 1 K have been observed even on YSZ substrates. Critical current densities, jc (77 K), of more than 2 x 106 A/cm2 could be obtained on SrTiO3-substrates. The high quality of the thin films over large areas was demonstrated by the measurement of persistent superconducting current densities at 77 K in the order of 105 A/cm2 in a 1.5 mm broad ring of 9 mm diameter. No dissipation of this persistent current could be observed during one hour. Measurements of the same film after 8 months in normal air showed a 40 % decrease of jc and a stronger decrease of jc with an externed magnetic field, suggesting that in the meantime the macroscopic ring current density is dominated by intergranular weak links.
Magnetic Flux Pinning in YBa2Cu3O7 Films
Authors: Kerchner H. R. , Feenstra R. , Thomson J. O. , Thompson J. R. , Christen D. K. , Sekula S. T. , Boatner L. A. 
Published: March 2011

AbstractThe magnetic hysteresis was studied for YBa2Cu3O7 films of different epitaxial orientations on single-crystal SrTiO3 and KTaO3 substrates. Deposition by coevaporation of Y, BaF2, and Cu was followed by annealing in flowing, wet oxygen at 800-850°C. The critical current density Jc deduced from magnetic hysteresis loops was compared with four-terminal transport-current results. Thermally activated magnetic flux flow was manifest in the audio-frequency data. Jc fits a scaling law similar to one used for describing Nb3Sn and other A15 materials.
Critical Current Enhancement in Single-Crystal Ba2Ycu3O7
Authors: van Dover R. B. , Gyorgy E. M. , Schneemeyer L. F. , White A. E. , Glarum S. , Felder R. J. , Waszczak J. V. 
Published: March 2011

AbstractThe critical current density, Jc, of single crystals of Ba2YCu3O7 is comparable to that of melt-textured-growth materials as well as to the intragrain Jc of bulk polycrystalline Ba2YCu3O7. Typical values at 77 K and 9 kOe are near 5x 103 A/cm2, and are presumably limited by weak pinning. We have obtained a significant enhancement of this pinning-limited Jc by three techniques: 1) a short reannealing procedure, 2) fast neutron irradiation, and 3) proton irradiation. Interestingly, the combination of the first technique followed by either irradiation is not as effective as the iradiation alone. That is, the best candidates for irradiation are not necessarily those with the highest initial Jc.
Significantly Enhanced Flux-Pinning in Y-Ba-Cu-O by Simple Processing
Authors: Jin S. , Tiefel T. H. , Nakahara S. , Graebner J. E. , O'Bryan H. M. , Fastnacht R. A. , Kammlott G. W. 
Published: March 2011

AbstractSignificantly improved flux-pinning has been achieved in bulk YBa2Cu3O7-δ superconductor (‘123’ compound) containing fine-scale defects (<~50 A thick). The measured Jc(magn.) of ~l05 A/cm2 at 77K, H = 0.9T is about ten times higher than the typical values for bulk Y-Ba-Cu-O. The improved structure was produced by rapid decomposition at 920°C of the YBa2Cu4O8 (‘124’) precursor.
Hysteretic Dependence of Critical Current on Applied Magnetic Field and Magnetic Irreversmujty Line Crossings in Polycrystalline YBa2Cu3C7
Authors: Askew Thomas R. , Flippen Richard B. 
Published: March 2011

AbstractThe transport critical current density Jc has been measured in high quality poly-crystalline YBa2Cu3C7 as a function of temperature and for various sweeps of sub-Tesla applied magnetic fields. Large increases over the virgin response were observed in Jc at fields of a few hundred gauss and are attributed to trapped flux in the samples. The amount of trapped flux was measured and correlated to the change at Jc at various temperatures. The position of the magnetic irreversibility line was measured by field induced absorption shift in AC susceptibility. The various data are discussed in the context of the weak link conduction model.
Harmonic Generation in the Alternating Magnetic Response of High-Temperature Superconductors
Authors: Shaulov A. , Bhargava R. , Dorman D. 
Published: March 2011

AbstractWe report a novel ac technique for characterizing the magnetic behavior of high-temperature superconductors. This technique is based on monitoring the spectrum of the magnetic response of these materials to small sinusoidal fields. A nonlinear magnetic behavior is indicated by the appearance of harmonic components in the spectrum. Measurements of these harmonics as a function of bias field, temperature and frequency provide valuable information about the processes of flux penetration, flux pinning and motion in these materials.
Ac Susceptibility Studies of the High Tc Superconductors: Dissipative Effects in La2.xSrxCuO4-Y and YBa2Cu3O7-Y Systems
Authors: Ling Xinsheng , Filipkowski M. E. , Heller E. K. , Budnick J. I. 
Published: March 2011

AbstractWe have studied the variation of dissipative effects with doping in the high Tc superconductors La2-xSrxCuO4-y and YBa2Cu3O7-y by studying the lossy component of ac susceptibility as a function of temperature. We find relatively strong excess losses at low temperature in both systems, which indicate stronger flux creep at grain boundaries, in lower level doped ceramic samples produced by a similar process. This effect is more significant in the La2-xSrxCuO4-y (214) system than in the YBa2Cu3O7-y(123) system. We suggest that the microscopic mechanisms of weakening of the order parameter in the grain boundaries may be different in the two systems. In the 214 system, as the charge carrier density in the CuO2 planes is reduced, the spatial fluctuation of the order parameter in the CuO2 planes is enhanced. In the 123 system, the initial removal of O from the sample, which weakens the coupling between planes and increases the spatial fluctuation of the order parameter between CuO2 planes. The grain boundaries are degraded in both systems. The degradation in the 214 samples is more significant than in the 123 samples.
The Effects of Oxygen and Strontium Vacancies on the Superconductivity of Single Crystals of Bi2sr2‐Xcuo6‐Y
Authors: Sales B. C. , Sonder Edward , Chakoumakos B. C. 
Published: March 2011

AbstractSingle crystals of Bi2Sr2‐xCuO6‐y were grown from CuO‐rich melts. The Sr content in the crystals was varied from x=0.1 to x=0.5 by varying the starting composition of the melt and the oxygen content was adjusted using an appropriate heat treatment of the crystals in a thermogravimetric system. With decreasing Sr content the superconducting transition temperature,Tc, of the crystals decreased rapidly from 10 K to below 4.2 K and the resistivity in the a‐b plane changed from metallic (linear in T from 30 to 300 K) to semiconducting. Reducing the oxygen content in the crystals had a similar effect on the resistivity. Only crystals with close to the maximum oxygen content (y=0) were superconducting, and removal of oxygen from previously superconducting crystals resulted in a rapid decrease of Tc , and the eventual loss of superconductivity (Tc &#X003C; 4.2 K). Although crystals of Bi2Sr2‐xCuO6‐y could be made sequentially superconducting‐semiconducting‐superconducting by the addition‐removal‐addition of oxygen, the process was not totally reversible. After only one such cyclic heat treatment x‐ray diffraction indicated that for some compositions such cycling resulted in the appearance of CuO and an another layered structure that has been identified previously and is slightly deficient in CuO. The new layered structure is semiconducting and has a layer‐stacking repeat distance that is 1 &#X00E5; smaller than the superconducting “221” phase.