bluuebunny/crossref_metadata_2025_split huggingface dataset:
YBa2 Cu(3-x)CoxOy- A Substrate Material for YBCO Superconductors
Authors: Vienna J. D. , Balachandran U. , Cermignani W. , Poeppel R. B. , Taylor J. A. 
Published: March 2011

ABSTRACTThe physical properties of the ceramic YBa2Cu(3-x)CoxOy have been investigated in order to evaluate its usefulness as a substrate material for YBCO superconductors. YBa2Cu(3-x)CoxOy has been found to be thermally and chemically compatible with 123 and displays adequate electrical properties for a substrate material. A material with the nominal composition of YBa2Cu2.2CO0.8O7 was investigated, extensively. The mechanical properties of this material were found to be poor, e.g., tensile strength was only 60 MPa. A semiconductor-like behavior was observed with a room-temperature resistivity of 70 mμ.cm and a resistivity equal to 4 × 106 mn.cm at 77K. [ Key words: YBa2Cu3Oy, cobalt substitution, substrate, electrical properties, thermal properties, processing]
Rheed Intensity Oscillation During Layer-by-Layer Growth of Bi-Sr-Ca-Cu-O Thin Films
Authors: Yoshikawa K. , Sasaki N. 
Published: March 2011

ABSTRACTUsing in-situ reflection high-energy electron diffraction (RHEED), we studied the growth of Bi-Sr-Ca-Cu-O (BSCCO) thin films prepared by reactive evaporation using layer-by-layer deposition. Bi2Sr2CaCu2Ox(2212) tends to be grown three-dimensionally if it is grown directly on (100) SrTiO3, in contrast to Bi2Sr2CuOx(2201) which is easily grown two-dimensionally on SrTiO3. Two-dimensional 2212 growth can be realized, if a buffer layer of 2201 is deposited on (100) SrTiO3 and growth interruption is utilized after SrO layer deposition. A buffer layer of only two 2201 unit cells improved the surface crystallinity of the substrate for the epitaxial growth of 2212. Growth interruption for two minutes after the 2nd SrO layer in the half unit cell is necessary to keep two-dimensional layered growth. The resulting Tc (zero) is 76 K and Jc (at 4.2 K) is 1.5 × 106 (A/cm2) with these epitaxial films.
Preparation of YBa2Cu4O8 Thin Films by MOCVD
Authors: Sakai H. , Hayashi H. , Uehara K. , Kubota N. , Sugimoto T. , Shiohara Y. , Tanaka S. 
Published: March 2011

ABSTRACTPreparation processing to obtain 124 single phase films has been studied by MOCVD. The YBCO thin films which were fabricated on MgO(100) and SrTiO3(100) substrates, respectively, were obtained under both conditions of Ts(temperature of susceptor)=800°C and Po2(oxygen partial pressure)=17.5torr. It was found that the oriented peaks of 124 c-axis and of 123 a-axis were more prominent than others at the composition ratio(Y/Ba/Cu=l.0/2.7/4.7), using the MgO(100) substrates. The 123 a-axis oriented grain was observed by using SEM and TEM. We have obtained thin films which were dominant in the 124 phase on the SrTiO3(100) substrates. The film surface morphology on the SrTiO3(100) substrate was smoother than that on the MgO(100) substrate. The origin of a-axis oriented grain growth was explained by the surface step(about 10 À) on MgO(100).
Growth of Sr1−xNdxCuOy Thin Films by Rf-Magnetron Sputtering and Pulsed-Laser Deposition
Authors: Sugii Nobuyuki , Ichikawa Michiharu , Kubo Koichi , Sakurai Takeshi , Yamamoto Kiyoshi , Yamauchi H. 
Published: March 2011

ABSTRACTSr1−xNdxCuOy thin films are grown on SrTiO3 substrates by rf-magnetron sputtering and pulsed-laser deposition. The sputter-deposited film with x=0 has an “infinite-layer” structure whose lattice constants are: α=0.390 nm and c=0.347 nm. When x is larger than 0.1, the films contain a phase of the Sr14CuO24O41 structure. The laser-deposited films of Sr1−xNdxCuOy with x≤.075 were single phase of the “infinite-layer” structure. The lattice parameter c decreased and the lattice parameter αincreased, as the Nd content, x, increased. The films with α=0.10 and 0.125 exhibited superconducting onset temperatures around 26 K. Weak Meissner signals were observed for these films at temperatures below 30 K.
Characterization of DyBa2Cu3O7+δ thin Films Prepared by Ozone-Assisted Co-Evaporation Technique
Authors: Hsieh T. J. , Smilgys R. V. , Chiang C. K. , Robey S. W. , Arsenault R. J. , Salamanca-Riba L. 
Published: March 2011

ABSTRACTSuperconducting thin films of DyBa2Cu3O7-δ_ are deposited on MgO(100) substrates by an ozone-assisted coevaporation technique. At a relatively low substrate temperature (610°C) and with a fixed ozone flux we prepare highly c-axis oriented films with very good superconducting properties. The critical temperatures of the films are commonly above 85 K with critical currents above 10 5 A/cm2. We report on composition, microstructure, electrical resistivity and critical current of two good films.
CO-Sputtered Composite films Of YBa2Cu3O7−xand LaAIO3
Authors: Allen L. H. , Cukauskas E. J. , Sherrill G. K. , Holm R. T. 
Published: March 2011

ABSTRACTWe have grown thin film composites of and YBa2Cu3O7−x and LaAlO3 by co-sputtering. A film with composition of 10% LaAIO3 by volume had a transition temperature of 58K and critical current density of 1.2 × 106 A/cm2 at 4K. We measured the temperature dependence of the critical current and obtained a good fit with Ginzburg-Landau theory for thin films. A perpendicular magnetic field was applied, and the critical current and pinning force measured. At 70 kOe, the critical current was suppressed only a factor of 4 from its zero-field value. The measured pinning force was 2 × 109 dyn/cm3 at 70 kOe and is comparable to that of YBa2Cu3O7−x films.
Electric Field Effect in High-Tc Superconductors, Evaluation of Field-Induced Superconductivity and Device Applications
Authors: Mannhart J. , Kleinsasser A. 
Published: March 2011

ABSTRACTIn the past two years, it has been demonstrated that applied electric fields can be used to modulate significantly the normal state resistivity, the critical temperature and the critical current density of high-Tc films. Whereas earlier publications focussed on experimental aspects of high-Tc field effects, this contribution will discuss the conditions that are required to induce superconductivity on the surface of insulators. In addition, evaluations for performance limits of potential high-Tc field effect devices will be presented.
Temperature Dependent C-V Characteristics of YBCO/YSZ/Si MIS Capacitors
Authors: Qiao Jianmin , Ajimine Eric M. , Patel Paresh P. , Segovia Marco A. , Yang Cary Y. , Fork David K. , Ponce Fernando A. , Tramontana Joseph C. 
Published: March 2011

ABSTRACTMetal-insulator-semiconductor capacitors are fabricated from a YBa2Cu3O7-δ (YBCOVYttria-Stabilized Zirconia(YSZ)/Si structure. Current-voltage(I-V) measurements reveal that thicker YBCO films(≤150Å) tend to result in more stable capacitors. Results of capacitance-voltage(C-V) measurements during bias-temperature cycling suggest the presence of a thermally activated process in the YSZ and/or YSZ/Si interface. This process is probably related to trapping/detrapping mechanisms in the SiOx, layer formed between YSZ and Si. It is shown that the distribution of mobile ions in YSZ can be “set” with biases at room temperature and then “frozen” by lowering the temperature, giving rise to adjustable threshold voltages at 80K.
RHEED-Controlled Unit-Cell by Unit-Cell Layer-Growth of High-Tc Cuprate Films with Laser-Ablation Technique
Authors: Frey T. , Chi C. C. , Tsuei C. C. , Shaw T. , Trafas G. 
Published: March 2011

ABSTRACTThin films of PrBa2Cu3O7 and in-situ superconducting YBa2Cu3O7 were grown on (100)-oriented SrTiO3 substrates by laser ablation under molecular beam epitaxial condition. The unit-cell by unit-cell growth of these high-Tc cuprate materials has been indicated by RHEED-oscillations and further confirmed by cross-sectional TEM (X-TEM) and small angle X-ray. Superconductivity with Tc (R = 0) at 35 K was observed for samples with one unit-cell YBa2Cu3O7 layers sandwiched between PrBa2Cu3O7 layers. TC varies with the number of YBa2Cu3O7 unit-cell layers. An eight unit-cell thick YBa2Cu3O7 film is superconducting at 86 K. Substrate temperature is found to be the most crucial parameter in determining the growth mode and superconducting properties.
Degradation and Recovery of Transport Properties of Strained HTS Conductors
Authors: Patel S. , Ye J. , Haugan T. , Chen S. , Li S. S. , Wong F. , Shaw D. T. , Tsuei C. C. 
Published: March 2011

ABSTRACTMechanical bending of HTS tapes can result in the deterioration and destruction of their transport properties. Depending on the magnitude and type of strain (tensile or compressive), the films can be permanently damaged by fracture and recoverable only by post heat treatment, or simply elastically strained with recoverable transport properties upon release of the strain. Here we present results of strain effects on BSCCO (2212) /Ag tape transport properties and post heat treatment recovery of those properties.
Dependence of Critical Current Density on Granular Arrangement in Ceramic Superconductors
Authors: Wang Jui H. , Ren Zhifeng 
Published: March 2011

ABSTRACTThe critical current density Jc of bulk ceramic superconductors is often several orders of magnitude lower than that of a single crystal or oriented fílm of the same material due to the weak links residing at the boundaries between single crystals within the ceramic sample. Assuming that the rate of electron transport within each single crystal is much faster than the average rate of electron transport between adjacent single crystals, a working hypothesis of Jc enhancement by granular reorientation is formulated which includes the“brickwall”model and melt-texturing as special cases with long-range granular alignment which usually leads to rigid and brittle bulk samples. Simple geometric considerations show that only short-range local granular alignment is necessary for high Jc. For mis reason, it should be possible to make flexible superconducting wires and tapes for commercial applications at or above 77K.
The Synthesis of“1223”TL-CA-BA-CU-Oxide Superconducting Films Via the Reaction of Silver-Containing Spray Deposited Oxide Precursors with Thallium Oxide Vapor in a Two-Zone Reactor
Authors: DeLuca J. A. , Karas P. L. , Tkaczyk J. E. , Briant C. L. , Garbauskas M. F. , Bednarczyk P. J. 
Published: March 2011

ABSTRACTSuperconducting films of“1223”Tlx Ca2Ba2Cu3Oy (0.65<×<l.00) have been prepared on polycrystalline yttria stabilized zirconia substrates via the reaction of thallium oxide vapor with spray-deposited Ca-Ba-Cu-oxide films containing silver. The silver addition permits the formation at 860C of oriented, interconnected polycrystalline superconducting films with Tc(0) values of 104–107K. Samples have been prepared routinely with 77K zero-field dc transport critical current densities >10,000A/cm2 with values as high as 105,000A/cm2 having been measured. The range in Jc values measured is believed to be related, at least in part, to inhomogeneities in the films. The excellent in-field characteristics of the“1223”thick films are reflected in the behavior of the“105,000A/cm” sample for which J >10,000A/cm was measured at 60K in a 2 Tesla field applied parallel to the crystallographic c-axis
Critical Current Density of the AG-Clad BI-Based Superconductors
Authors: Dou S. X. , Guo Y. C. , Liu H. K. 
Published: March 2011

ABSTRACTA high-Tc phase formation-decomposition-recovery process(PFDR) through the use of a short period of melting has been developed for fabrication of Ag-clad Bi-Pb-Sr-Ca-Cu-O (BPSCCO) wires. The weak links and flux pinning have been significantly improved and an extended plateau regime in the Jc-H curve has been observed. The PFDR processed tapes exhibit 3 to 10-fold increase in the Jc at 77 K and 1 Tesla over the normally processed tapes. A Jc of 40000 A/cm2 at 77 K and 0 T and 9000 A/cm2 at 77 K and 1 T have been achieved. The Jc correlates well with the degree of grain alignment which can be measured through the Jc dependence on the orientation of the applied field. The improved Jc - H characteristics is attributed to the desirable microstructures consisting of well aligned (Bi,Pb)2Sr2Ca2Cu3O10+y (2223) grains, fraction of (Bi,Pb)2Sr2CaCu2O8+y(2212) and high density of dislocations produced through PFDR process. The superconducting Ag/Bi-Pb-Sr-Ca-Cu-O wires can be made flexible. The Jc remains unchanged when wires of superconductor thickness 25 μm are bent to a strain rate of 1.5%
Relative Reactivity Trends OP High Temperature Superconductor Phases
Authors: Riley David R. , Zhou Ji-Ping , Manthiram A. , McDevitt John T. 
Published: March 2011

ABSTRACTMany of the high temperature superconductor phases degrade rapidly when in the presence of water, acids, carbon dioxide or carbon monoxide. In order to foster more rapid developments in the area of high-Tc research, it will be necessary to acquire a more complete understanding of the surface chemistry of these superconducting materials. In this paper, the relative reactivity of the common cuprate phases toward water is reported. X-ray powder diffraction and scanning electron microscopy measurements are utilized here to establish the reactivity trends.
Controlling the Microstructure of the 2223 Phase Grains for the Fabrication of Silver Clad (Bi,Pb)2Sr2Ca2Cu3Ox Tapes Through the Growth Kinetics of the Superconducting Phases
Authors: Lo Wai , Glowacki B. A. 
Published: March 2011

ABSTRACTOur study concentrated on the relationship between the proportions of the phases in the precursors used to synthesise the Bi-2223 phase and the ultimate microstructures of the 2223 phase materials, although the overall cation stoichiometry fixed. It was found that the final 2223 phase grains were larger, although the bulk density tended to be lower with the grains loosely packed together, when the major phase in the precursor was 2212 phase. This was proved to be partly caused by the fast growth rate of the 2212 phase grains which were eventually converted into the 2223 phase. When 2223 phase was present in the precursor, the bulk density became higher and 2223 phase grains became closely packed together, although the average grain size became smaller. This was explained by the existence of a liquid phase at higher temperatures during the formation of the 2223 phase and the sintering of the 2223 phase grains.
Applications of Parallel Josephson Junction Arrays for the Detection of Magnetic Flux
Authors: Miller J. H. , Gunaratne G. H. , Zou Z. , Huang J. , Golding T. D. 
Published: March 2011

ABSTRACTWe have carried out finite-inductance calculations of the critical current vs, flux(Ic-φ) and voltage vs, flux (V-φ) characteristics of superconducting interferometers with many Josephson junctions (JJ's) in parallel. At least two features of our calculations suggest that interferometers with many junctions, which we call Superconducting QUantum Interference Gratings, or SQUIG's, might be advantageous for the detection of magnetic flux. First, the voltage noise can potentially be reduced significantly as compared to a dc SQUID with the same overall voltage-to-flux transfer coefficient - a feature which might reduce 1/f noise and enhance the magnetic flux sensitivity of both low and high Tc superconducting (HTS) devices. In addition, nonuniformity of the junction critical currents appears to have little adverse effect on the predicted diffraction-grating like enhancement and narrowing of the peaks in the Ic-φcharacteristic, suggesting that flux uniformity, rather that critical current uniformity, is of primary importance.
Some Observations on the Measurement of Transport Critical Current Density in Bulk Ceramic Superconductive Wire
Authors: Samajdar S. , Samanta Shyam K. 
Published: March 2011

ABSTRACTThe transition temperature and the critical current density of a bulk YBa2Cu3O7−x-Ag microcomposite superconductive wire, prepared by powder processing followed by warm extrusion, have been measured employing the standard AC four probe technique. Measurements were performed, at 15K and zero applied field, with varying distance between the voltage contacts, while the current contacts remained a constant distance apart. It is observed that the resistance-temperature behavior remained identical in all the cases. Interestingly, the critical current density, determined from the experimentally recorded current-voltage characteristic by applying a constant electric field criterion, is seen to increase significantly, smoothly and steadily with increasing voltage tap length. However, the critical current density remains virtually unchanged if a constant voltages criterion is applied for its determination. This paradoxical dependence of critical current density, a material property, on measurement length has been explained with the help of a simple theoretical treatment, taking into account the nature of current-voltage chracteristics as well as the phenomenon of current transfer through the metallic to the superconducting ceramic phase. It is suggested that the constant electric field criterion may not be an appropriate one to use in the evaluation of critical current density of metal-ceramic superconductive composites.
Weakening of Flux-Pinning Strength for High Tc Superconductors in an Alternating Magnetic Field
Authors: Chen Q. Y. 
Published: March 2011

ABSTRACTThe flux-pinning forces in high temperature superconductors were found to be weakened in an ac field as the applied field strength or the frequency increases. In the weakly pinned regime, flux dynamics could be described widi the concept of magnetic diffusion. Flux-motion-induced finite resistivity could lead to significant skin-effect which was reflected in the ac screening effectiveness. The frequency dependence of the relative local field within a superconducting hollow cylinder were used to deduce the flux-motion resistivity (ρ). For superconducting YB2Cu3O7−x compounds at 77K it was found that ρ≈ 1μΩ-cm. The corresponding magnetic diffusion coefficient was ≈224 cm2/s. At 750 Hz the skin depth is around 1.54 mm as compared with the 2-mra sample wall thickness.
Superconductivity of Dc Reactive Magnetron Sputtered Epitaxial TiN/NbN Superlattices
Authors: Shinn M. , Hong B. -S. , Barnett S. A. 
Published: March 2011

ABSTRACTEpitaxial B1-structure TiN/NbN superlattices have been grown by reactive magnetron sputtering On MgO(001). X-ray diffraction and transmission electron microscopy (TEM) diffraction spectra exhibited up to nine orders of superlattice reflections, indicating that the superlattice interfaces were relatively sharp. TEM images also showed well-defined layers. The superlattice wavelength (∧) dependence of the superconducting transition temperature (Tc), critical Current density (Jc), and electrical resistivity (ρ) have been investigated. Tc values increased from 12 K to 17 K with increasing ∧. Jc in a magnetic field perpendicular to the film surface ranged from 104 to 106 A/cm2, increasing with increasing wavelength and decreasing with increasing applied magnetic field. Jc in a field parallel to the film surface was > 10 times higher, ≈ 107 A/cm2. The resistivity exhibited different ∧ dependencies in three different A ranges.
Transformation of a vortex lattice and an inclusion in superconductors
Authors: Tokuono Shinya , Tanaka Shoji , Fukuyama Hidetoshi 
Published: March 2011

ABSTRACTInteraction between vortices and inhomogeneity in superconductors is studied. As a typical example, we investigated the case of a single vortex and some vortices near an inclusion of the cylindrical shape and derived the interaction potential for the vortices as a function of the distance by use of the solution of London equation.
Long Time Power Law Magnetic Relaxation in Detwinned YBa2Cu3O7-δ Single Crystals
Authors: Zhang Lu , Liu J. Z. , Lan M. D. , Klavins P. , Shelton R. N. 
Published: March 2011

ABSTRACTThe time-dependent magnetic relaxation was measured in a full field penetrated YBa2Cu3O7-δ detwinned crystal for long times up to 5×105 sec. The relaxation data exhibit a power-law time dependence over a wide range of temperatures and magnetic fields indicative of flux creep with logarithmic dependence of the effective creep activation barrier U(J). A theoretical model is employed to analyze the data and to determine the activation energy.
Studies of Crystalunity for Sputter Deposited Bi-Based Oxide Films
Authors: Mizuno Koichi , Ichikawa Yo , Setsune Kentaro 
Published: March 2011

ABSTRACTCrystalline quality of Bi-based oxide films has been evaluated by means of X-ray diffraction (XRD) and ion-channeling on the Rutherford backscattering (RBS). The films were sputter deposited 2201-phase Bi2Sr2Cu1O8-δ (BSCO) and 2212-phase Bi2Sr2Ca1Cu2O8-δ (BSCCO). They were prepared on MgO(100) and SrTiO3(100) substrates at the low temperature of 650°C during the deposition. The best quality, however thin films had poor crystallinity compared to single crystals, was obtained with the 2201-phase BSCO film that was deposited on a SrTiO3(100) substrate. The full width at half maximum (FWHM) value of the rocking curve on XRD for the film was estimated as 1560 (arc sec).
Smart Ferroelectric Films and Fibers; Applications in Micromechanics
Authors: Brooks Keith G. , Udayakumar K. R. , Chen Jiayu , Selvaraj Ulagaraj , Cross L. Eric 
Published: March 2011

ABSTRACTSmart electroceramics, in the form of ferroelectric thin films show great potential for applications in the field of microelectromechanical systems. Ferroelectric thin films will become a key player due to their optical, mechanical, electrical and thermal sensing with actuating capabilities. Recent results on electromechanical transduction in piezoelectric (e.g. PZT), electrostrictive (e.g. PLZT), and antiferroelectricferroelectric phase switching (e.g. PLZSnT) thin films and their potential applications in smart micromechanical systems are discussed. The possibility of three dimensional structures exists in the emerging technology of ferroelectric fibers. Some exciting applications for these films and fibers include microvalves, ultrasonic micromotors, microrobotic actuators and micropumps.
A Silicon-Based Shape Memory Alloy Microvalve
Authors: Ray Curtis A. , Sloan Charles L. , Johnson A. David , Busch John D. , Petty Bruce R. 
Published: March 2011

ABSTRACTA new actuator for silicon micro-valves has been developed and tested. A thin film shape memory alloy provides for large deflections with high speed, low power, and small size. The actuator is batch fabricated with planar processes.
Metallization at Microindentations
Authors: Gilman John J. 
Published: March 2011

ABSTRACTIt is shown that quite generally there is a correlation between insulator-metal transition pressures and indentation hardness numbers for covalent crystals. They are numerically equal for the Group IV elements. Three elements plus five III–V compounds acquire the β-Sn structure upon metallizing. Bondbending, rather than bond-shortening, appears to lead to their transformations. A simple version of the theory of covalent bonds gives the critical transformation bond-angle correctly.
Charactervation of Adhesion in Thin-Film Materials by the Blister Test
Authors: Chu Y Z. , Jeong H. S. , White R. C. , Durning C. J. 
Published: March 2011

ABSTRACTIn this work a blister test is applied to study the adhesion of thin films to substrates. In the blister test one injects a fluid at constant rate at the interface between the substrate and an overlayer to create a “blister”. The fluid pressure is measured as function of time. An analysis gives a reliable way of calculating the adhesion energy Ga. from the time-dependent pressure data. The method was applied to a variety of systems including polymer/polymer, polymer/silicon and polymer/metal interfaces. The results show that the test is very sensitive and is able to determine small adhesion energies inaccessible in conventional peel tests. This work demonstrates that the blister test provides a means of relating the mechanical strength of an interface to its microscopic dynamic and structural features.