bluuebunny/crossref_metadata_2025_split huggingface dataset:
Grain Boundaries in Yba2 Cu3O7-δ Thin Films
Authors: Norton M. Grant , Tietz Lisa A. , Carter C. Barry , Russek Stephen E , Moeckly Brian H. , Buhrman Robert A 
Published: March 2011

AbstractGrain boundaries in YBa2Cu3O7-δ thin films deposited on (001)-MgO by pulsed laser ablation have been characterized using selected area diffraction. In addition to twin boundaries, the presence of both low-angle and high-angle grain boundaries were characteristic of the film's microstructure. The presence of certain grain boundaries may be responsible for the weak-link Josephson behavior observed in small constrictions formed in superconducting films on MgO.
Preparation of Superconducting Y‐Ba‐Cu‐O Thin Films by Mo‐Cvd
Authors: Ohnishi Hiroshi , Kusakabe Yoshihiko , Kobayashi Minoru , Hoshinouchi Susumu , Harima Hiroshi , Tachibana Kunihide 
Published: March 2011

AbstractHigh‐Tc superconducting Y‐Ba‐Cu‐O films were prepared on Mg0(100) substrate by MO‐CVD technique without post annealing. The highest Tc obtained was 85K. The film was made up of dense matrix and dispersed fine particles. The Y‐Ba‐Cu composition of matrix was nearly equal to the 1:2:3 superconducting phase. The film was highly oriented with c‐axis perpendicular to the substrate. The lattice constant of the film was 11.68A.
Low Temperature Preparation of Y‐Ba‐Cu‐0 High Tc Superconducting Thin Films by Plasma‐Enhanced Organometallic Chemical Vapor Deposition
Authors: Zhao Jing , Marcy Henry O. , Tonge Lauren M. , Wessels Bruce W. , Marks Tobin J. , Kannewurf Carl R. 
Published: March 2011

AbstractWe report here a plasma‐enhanced organometallic chemical vapor deposition process for the preparation of YBa2Cu3O7‐x thin films using two rf plasma coupling configurations. For the films grown under a direct plasma glow, the YBa2Cu3O7‐x phase is not found in the as‐deposited state. However, by employing plasma‐activated nitrous oxide as the reactant gas, superconducting YBa2Cu3O7‐x films having a low carbon content and a mirror‐like surface have been prepared in‐situ at a substrate temperature of 610°C using an organometallic chemical vapor deposition process.
Superconducting yba2cu3o7‐x Thin Film on Metal Substrate by Chemical Vapor Deposition Process.
Authors: Yamaguchi T. , Aoki S. , Sadakata N. , Kohno O. 
Published: March 2011

AbstractSuperconducting YBa2Cu307_x thin films were prepared by chemical vapor deposition using beta‐diketonate chelates on various oxide substrates and metal substrates. According to X‐ray diffraction patterns, the existence of a well‐oriented orthorhombic YBagCUgO^x structure has been confirmed in all specimens. The temperature of complete superconducting transition were observed at 89K on single‐crystalline oxide substrate, and 84K on metal substrate. Reduced critical current density of the film on single‐crystalline substrate in magnetic fields up to 600mT at 77K remained one or two order of magnitude higher than that of the film on metal substrate.
High‐Tc Undoped and Pb‐Doped BI‐SR‐CA‐CU‐O thin Films Prepared by Organometallic Chemical Vapor Deposition
Authors: Zhang J. M. , Marcy H. O , Tonge L .M. , Wessels B. W. , Marks T. J. , Kannewurf C. R. 
Published: March 2011

AbstractFilms of the high‐Tc undoped and Pb‐doped Bi‐Sr‐Ca‐Cu‐O (BSCCO) superconductors have been prepared by low pressure organometallic chemical vapor deposition (OMCVD) using the volatile metal‐organic precursors Cu(acetylacetonate)2, Sr(dipivaloylmethanate)2, Ca(dipivaloylmethanate)2, and triphenyl bismuth. Factors which influence texture and morphology of the OMCVD‐derived films have been investigated, including the effects of annealing, doping, and substrates.
Preparation of Bi‐Sr‐Ca‐Cu‐0 Superconducting Thin Films by Mocvd
Authors: Gohda Shinji , Maeda Yasuhiro 
Published: March 2011

AbstractBi‐Sr‐Ca‐Cu‐0 superconducting thin films have been prepared on MgO substrates by a Metalorganic Chemical Vapor Deposition technique using an infrared lamp. It was found in this study that the film composition ratio could be precisely controlled by using this technique. A zero resistance at 81K was obtained for Bi1Sr1.3Ca0.9Cu1.8Ox film grown at 850°C. The critical current density of this film was 1.0xl03A/cm2 at 77K.
Preparation of Yba2Cu3O7-X. Superconducting Thin Films by Means of Single Target Rf-Sputtering+
Authors: Weyten Herman D.L. , Batist R. De , Nagels P. , Cornelis J. 
Published: March 2011

AbstractHigh Tc superconducting thin films have been deposited on sapphire by means of RF‐sputtering from a single stoichiometric target of YBa2Cu3O7‐x composition. The YBa2Cu3O7‐x films were deposited in an argon‐oxygen atmosphere on a substrate which reached a temperature of s 400°C during deposition. The study of stoichiometry and homogeneity of the as‐deposited films, by means of electromicroprobe analysis (EMPA), was used to optimize the sputtering parameters of the system. To achieve superconductivity, with an onset of s 90 K, a high‐temperature, post‐deposition thermal treatment in oxygen was necessary. Resistivity measurements show that, with respect to the bulk samples, zero resistivity is lowered as a result of substrate interaction. The use of buffer layers can improve the quality of the superconducting thin films.
Partial Reduction/Re-Oxidation Processing of Y-Ba-Cu-O Sputtered Thin Films
Authors: Garzon F.H. , Beery J. G. , Wilde D. K. , Raistrick I. D. 
Published: March 2011

AbstractThin films of Y‐Ba‐Cu‐O were produced by RF sputtering of YBa2Cu3O7‐x ceramic targets, using a variety of plasma compositions, RF power levels, and substrate temperatures. Post annealing of these films in oxygen produced superconducting films with Tc values between 40‐60 K, broad transition widths and semiconductor‐like electrical behavior above Tc. Subsequent annealing at 850°C in an inert gas with a residual oxygen partial pressure of ≤10 ppm followed by an oxygen anneal produced high quality thin films: Tc> 85 K with narrow transition widths. The structure and morphology of these films during reduction‐oxidation processing were monitored using X‐ray diffraction and electron microscopy.
X-Ray Line Broadening Analysis of Ybacuo Superconducting Thin Films
Authors: Ece M. , Vook R.W. , Allen John P. 
Published: March 2011

AbstractThin films of YBaCuO were prepared on MgO and SrTi03/Al2 03 substrates by rf magnetron sputtering. The SrTi03 was deposited onto AI2O3 by flash evaporation. The as‐deposited films on both substrates had an (001) orientation and were superconductors. Annealing the films in O2 improved their crystal 1inity and raised their critical temperatures (Tc). A detailed X‐ray diffraction study of the YBaCuO films was carried out. Values for the particle sizes and nonuniform strains along the c axis were obtained from broadened diffraction lines by using an integral breadth method. It was found that the broadening was mainly caused by nonuniform strain. It was also observed that nonuniform strain decreased as the films were annealed at various temperatures. The Tc's of the films were very sensitive to changes in nonuniform strain.
The Use of BaF2 Buffer Layers for the Sputter-Deposition of Ticabacuo Thin-Film Superconductors
Authors: Hubbard K.M. , Arendt P.N. , Brown D.R. , Cooke D.W. , Elliott N.E. , Fan J.D. , Nastasi M. , Ott K.C. , Peterson E.J. , Reeves G.A. 
Published: March 2011

AbstractThin films of the Tl‐based superconductors often have relatively poor properties because of film/substrate interdiffusion which occurs during the anneal. We have therefore investigated the use of BaF2 as a diffusion barrier. TICaBaCuO thin films were deposited by dc magnetron sputtering onto MgO <100> substrates, both with and without an evaporation‐deposited BaF2 buffer layer, and post‐annealed in a Tl over‐pressure. Electrical properties of the films were determined by four‐point probe analysis, and compositions were measured by ion‐backscattering spectroscopy. Structural analysis was performed by X‐ray diffraction and scanning electron microscopy. The BaF2 buffer layers were found to significantly improve the properties of the TICaBaCuO thin films.
Characterization of Epitaxial Superconducting YBacuO Thin Films with Three Different Orientations
Authors: Wang X.K. , Li D.X. , Song S.N. , Zheng J.Q. , Chang R.P.H. , Ketterson J.B. 
Published: March 2011

AbstractEpitaxial thin films of YBaCuO were prepared by multilayer deposition from Y, Cu, and BaF2 sources with: (1) the a‐axis perpendicular to (100)SrTiO3; (2) the c‐axis perpendicular to (100)SrTiO3; and (3) the [110] axis perpendicular to (110)SrTiO3. XRD patterns as well as SEM and HREM images confirm that the films are highly oriented, essentially epitaxial. Both the a‐axis oriented and the c‐axis oriented films exhibit zero resistance at 91K. The [110] oriented film shows the sharpest transiton with a transition width of IK and zero resistance at 85K. The zero field critical current density, Jc, determined magnetically, is in excess of 107A/cm2 at 4.4K and 1.04 x 106A/cm2 at 77K for the c‐axis oriented film; for the a‐axis oriented film we obtained 6.7 x 106A/cm2 at 4.4K and 1.2 x 105A/cm2 at 77K. The orientation dependence of the critical current density in the basal plane of the a‐axis oriented film was studied. The largest Jc's occur along the in‐plane <100> axes of the substrate.
Annealing Behavior of Ba2Ycu3+XO7+Y Thin Films
Authors: Siegrist T. , Coleman E. 
Published: March 2011

AbstractThe annealing behavior of Ba2YCu3+xO7+y films grown by coevaporation of BaF2, Y and Cu on SrTiO3 has been studied as a function of temperature. Upon annealing at temperatures below 800°C, the phase forming first is Ba2YCu4O8, independent of the starting stoichiometry. Higher temperatures, above approximately 825 ° C are needed for Ba2YCu3O7 to crystallize.
Microstructures of Y123 Films on Srtio3, Lagao3 and Laaio3
Authors: Roy T. , Raistrick I. D. , Mitchell T. E. 
Published: March 2011

AbstractTransmission electron microscopy(TEM) and scanning electron microscopy (SEM) have been used to study the microstructural features of YBa2Cu3O7 (hereafter referred to as Y123) films grown on various single crystal substrates by electron beam deposition. The films are all of high quality with the best observed Jc value being 10 A.cm‐2 at 7K. Cross‐sectional views in TEM have shown that the morphology of the film depends on its thickness. Thinner films (2500 Å) have a single layer of Y123 oriented with its c‐axis perpendicular to the substrate while thicker films(8000 Å) have this same c‐axis perpendicular layer closest to the interface with a c‐axis parallel layer above it. The interface between the film and the substrate is well defined in all cases with no amorphous region at the interface. Chemical analysis shows evidence of interdiffusion between the film and substrate.
Critical Current Density and Microstructure of Yba2Cu3O7-X Films as a Function of Film Thickness
Authors: Mogro-Campero A. , Turner L.G. , Hall E.L. , Lewis N. 
Published: March 2011

AbstractThin films of nominal composition YBa2Cu3O7‐x (YBCO) were produced on (100) SrTiO3 substrates by coevaporation and furnace annealing. Film thicknesses in the range of 0.2 to 2.4/μm were analyzed. Microstructural investigations by cross sectional transmission electron microscopy (TEM) reveal a continuous layer of about 0.4 μm thickness adjacent to the substrate with c‐axis normal to the substrate plane. In thicker films the remaining top portion has the c‐axis in the film plane. The critical current density (J ) at 77 K decreases with increasing thickness in the thickness range exceeding 0.4 μm, qualitatively consistent with the microstructural observations, but quantitatively inconsistent with a simple model based on the microstructural data.
High Tc Superconductor Films Grown by the Liquid Phase Epitaxial Technique
Authors: Yang C. S. , Yue A. S. 
Published: March 2011

AbstractHigh Tc superconducting YBa2Cu3O7 films have been prepared by the Liquid Phase Epitaxial (LPE) technique. The x‐ray diffraction patterns displayed a high degree of (00l) preferred orientations with c‐axes perpendicular to the film surfaces. The in‐situ grown YBa2Cu3O7 films showed zero‐resistivity at 76*K. Examination of the film cross sections by SEM revealed a growth mechanism.
A Crucibleless Liquid Phase Growth Method of Preparing the Y‐Ba‐Cu‐0 Superconducting Films
Authors: Chen K.C. , Perng L.H. , Lin C.H. , Perng T.P. , Wu T.B. , Wu J.M. , Chin T.S. 
Published: March 2011

AbstractSuperconducting Y‐Ba‐Cu‐0 film can be prepared by a liquid phase growth method without crucible on 96 % and 99 % alumina substrates. A buffer layer of sputtered gold or platinum was necessary for the formation of Yba2Cu3Ox phase. The flux of Ba2Cu3O10. was appropriate for this purpose. For a film of 10 mm x 20 mm x 10 micron, 0.6 to 0.8 gm initial weight was optimal, the optimum melting temperature was 1090 to 1110 °C for 20 ‐ 30 minutes. In order to obtain films with superconducting transition, an additional Y2BaCuO5‐underlayer was necessary. The resultant optimal films had Tc‐onset of above 80 % and Tc ‐zero of typically around 60 K.
Spray Pyrolysis Technique for the Deposition of Superconducting Films
Authors: Soller Marc , Moy Larry P. , Squillante Michael R. , Marzik James 
Published: March 2011

AbstractResearch has been performed on the use of chemical spray pyrolysis for depositing films of YBCO. The effects of reagent concentration, deposition rate, substrate temperature and substrate type were investigated. Films from less than 2 to more than 10 microns thick were deposited on single crystal strontium titanate, polycrystalline alumina and type 304 stainless steel.
A Novel Spray Pyrolysis System for the Deposition of High Tc Superconductors
Authors: Cumberbatch Toby J. , Deane Stephen , Barden Paul E. , Yu R. 
Published: March 2011

AbstractA spray pyrolysis system has been developed in which the use of airless atomisation and optical heating permits the deposition of thin film superconductors at growth surface temperatures exceeding 650*C. A comparison between centrifugal and hydrodynamic atomisation techniques shows that each possesses advantages and disadvantages for the deposition of thin films by this technique. The presence of a corona discharge has been found to be an essential ingredient for growth at high substrate temperatures.
Direct Imaging of the Atomic Structure and Chemistry of Defects and Interfaces by Z-Contrast Stem
Authors: Pennycook S. J. , Chisholm M. F. , Jesson D. E. , Norton D. P. , Mccamy J. W. , Lowndes D. H. 
Published: March 2011

AbstractZ-contrast scanning transmission electron microscopy (STEM) is a fundamentally new approach to high-resolution imaging which provides unambiguous, compositionally sensitive images on the atomic scale. Such images are intuitively interpretable, even in thick regions of the sample, tremendously simplifying determination of the structure and chemistry of defects and interfaces. To illustrate this, examples are presented of commonly observed planar defects in laser-ablated thin films of YBa2Cu3O7-x. Film/substrate interfaces are shown to be chemically diffuse on the atomic scale and steps or undulations in the substrate need not result in defects in the film. Low-angle grain boundaries are found to be chemically clean, the drastic reductions in critical currents with tilt angle being due to the array of intrinsic structural defects comprising the boundary.
Mechanism of Twin Formation During the Tetragonal to Orthorhombic Transformation In Yba2Cu3O7-X
Authors: Sarikaya Mehmet , Aksay Ilhan A. , Kikuchi Ryoichl 
Published: March 2011

AbstractThe formation of twins in the YBa2Cu3O7‐x system has been studied theoretically on the basis of transmission electron microscopy observations. The shape of the lips of the twinned domains is determined from two elastic strains, one associated with the twin boundary and the other with the lattice distortion at the lip region. The tangent of the angle at the tip which was calculated from the model agrees with experimental observations sufficiently well. The growth mechanism of the twinned domains is analyzed with an energy minimization approach. The similarities of transformation characteristics in this system to those of other systems are briefly discussed.
On the Resistive State of High Temperature Superconductors in Magnetic Field
Authors: Iye Y. , Nakamura S. , Tamegai T. , Terashima T. , Bando Y. 
Published: March 2011

AbstractExperimental studies of the resistive state of high temperature superconductors in the mixed state were carried out on thin film samples of YBa2Cu3O7‐y and Bi2Sr2CaCu2Os+y. Precise angular dependence measurements on Yba2Cu3O7‐y epitaxial film have revealed not only the critical field anisotropy with respect to the a, b, and c‐axes but also a feature associated with twin boundaries. Dependence on the angle between the transport current and the magnetic field is investigated and discussed in terms of flux dynamics in highly anisotropic layered superconductors. Peculiar behavior of the Hall effect in the resistive state is reported.
Critical Current Densities in Bi2Sr2Cacu2O8+D
Authors: Nomura Shunji , Yamada Yutaka , Yamashita Tomohisa , Yoneda Eriko , Yoshino Hisashi , Ando Ken 
Published: March 2011

AbstractCritical current densities and upper critical fields were measured for a single crystal of the high Tc oxide superconductor, Bi2Sr2CaCu2O8+d, within the ab basal plane and along the c axis. The anisotropy in critical current densities was observed to be Jc⊥/Jc//=10 in agreement with the anisotropy in resistivity for the normal state. The magnetic field dependence of the critical current densities can be interpreted by the anisotropy in the upper critical fields. The scaling of the critical current density with the magnetic field was found. The critical current density scaled to zero at fields Bc2 in the ab plane and along the c axis which were in good agreement with the upper critical fields measured by transport.The anisotropy in flux pinning force density along the b axis, Fp//b, and along the a axis, Fp//a, was found to be Fp//b/Fp//a=3. The data provided strong evidence for flux pinning by the modulated structure in this system.
Comparison of Flux Dynamics in Two Samples of YBa2Cu3O7 with Different Pinning
Authors: Turchinskaya M. , Bennett L.H. , Swartzendruber L.J. , Roitburd A. , Chiang C.K. , Hill M. , Blendell J.E. , Sawano K. 
Published: March 2011

AbstractThe kinetics of magnetization in two samples of YBa2Cu3O7 prepared by different methods, are studied. Magnetization vs. time data were obtained at various temperatures for a number of applied fields. The data display (after some short period of time) logarithmic behavior and (after a sufficiently long time) exponential behavior. The pinning parameter “activation volume” was determined from the experimental data for both samples.
Transport Critical Current of Sintered YBa2Cu3Ox in Time-Varying Magnetic Fields
Authors: Hambourger P. D. , DiCillo J. , Gibberman M. , Marino J. , Valek L. P. , Centanni Michael A. 
Published: March 2011

AbstractThe transport critical current of bulk sintered YBa2Cu3Ox has been measured at 77 K in the presence of static and sinusoidally-time-dependent (10–100 Hz) magnetic fields. In all cases, the field required for a given reduction of critical current density was independent of frequency to within ~10%.
Some Physical Properties of Suspendable Superconducting 123-Ag Composites
Authors: Huang C. Y. , Tai H. H. , Yao Y. D. , Li T. J. , Wu M. K. 
Published: March 2011

AbstractWe have measured the M-H hysteresis loops of n YBa2Cu3Oy: Ag (n = 3,5, and 7), and 3RBa2Cu3Oy:Ag (R = rare earth) as a function of temperature. We have found that the residual magnetization and, hence, pinning, is strong and is independent of n and R, but dependent on the metallurgy. The giant creep rates have been measured and are greater than those of pure 123 samples. Scanning electron microscopy and polarized light microscopy have shown that the presence of silver gives rise to the growth of large grains (~1 mm) in the 123-Ag samples. The field dependence of the critical current density is not strong at high field. We have also measured the resistance in field up to 200 kOe. The resistance remains zero even at 80 K and 200 kOe. The field dependence of the superconducting transition is discussed in terms of phase slippage.
The Dependence of Tc on Structural and Electronic Parameters for Ceramic High-Tc Superconductors
Authors: Giessen B.C. , Markiewtcz R.S. 
Published: March 2011

AbstractBased on the description of high-Tc cuprate superconductors as intercalation compounds and the van Hove singularity (vHs) concept for these phases, [with its consequences concerning their density of states (dos)] we give a model that explains T2 semi-quantitatively as a function of both hole concentration and stage number and, in a simplified variation, yields a functional dependence of T2 on the CuO2 layer fraction of the unit cell that shows a maximum, as observed.
High Resolution Laser Diagnostics for Direct Gap Semiconductor Materials
Authors: Salathe R.P. , Gilgen H.H. 
Published: March 2011

ABSTRACTThe laser-induced luminescence of direct gap semiconductors can be measured with high spatial (1 μm) and temporal (< 1 ns) resolution. A profiling technique is described for in-situ measurements during laser processing. It allows the evaluation of temperature, carrier density and band gap energy within the focal zone. The technique has been applied to (Al,Ga)As heterostructure material subjected to highly focused cw-Kr-ion laser radiation. The measurements reveal low temperature rises (<200 deg.C) at high excitation densities (>1kw/cm2) and an inhomogeneous distribution of optically excited carriers for concentrations above 2.1017 cm−3.
Laser Photolytic Deposition of Thin Films
Authors: Boyer P. K. , Moore C. A. , Solanki R. , Ritchie W. K. , Roche G. A. , Collins George J. 
Published: March 2011

ABSTRACTAn excimer laser is used to photochemically deposit thin films of silicon dioxide, silicon nitride, aluminum oxide, and zinc oxide at low temperatures (100–350deg;C). Deposition rates in excess of 3000 Å/min and conformal coverage over vertical walled steps were demonstrated. The films exhibit low defect density and high breakdown voltage and have been characterized using IR spectrophotometry, AES, and C-V analysis. Device compatibility has been studied by using photodeposited films as interlayer dielectrics, diffusion masks, and passivation layers in production CMOS devices.Additionally, we have deposited metallic films of Al, Mo, W, and Cr over large (>5 cm2) areas using UV photodissociation of trimethylaluminum and the refractory metal hexacarbonyls. Both shiny metallic films as well as black particulate films were obtained depending on the deposition geometry. The black films are shown to grow in columnar grains. The depositions were made at room temperature over pyrex and quartz plates as well as silicon wafers. We have examined the resistivity, adhesion, stress and step coverage of these films. The films exhibited resistivities at most ∼20 times that of the bulk materials and tensile stress no higher than 7 × 109 dynes/cm2
Characteristics of Laser Implantation Doping
Authors: Ibbs K G , Lloyd M L 
Published: March 2011

ABSTRACTUV laser photochemical dissociation and laser enchanced thermal dissociation have been used to generate free metal dopant species from a variety of organometallic molecules near a semiconductor substrate surface. Simultaneous laser annealing via a localised melt phase allows diffusion driven implantation of the metal atoms and subsequent electrical activation in the regrowing material. High levels of dopant concentration and activation are readily achieved in this way.Results will be presented on doping of silicon by boron using an ArF laser. These will include data on junction depths, number density and carrier density as a function of depth and interpretation of the data in terms of calculated temperature profiles.The possibility of tailoring junction characteristics by control of laser and gas flow parameters will be considered with preliminary experimental data.