bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Nickel on Magnetic and Electric Properties of Melt-Processed YBa2Cu3Oy/Ni Superconducting Composites
Authors: Kozllwski G. , Oberly C. E. , Maartense I. , Cao X. W. , Ho J. C. 
Published: March 2011

ABSTRACTTo assess a Ni-clad melt-processed YBa2Cu3Oy (YBCO) conductor approach, a systematic study was made on commercially available YBCO powder mixed and co-sintered with nickel oxide (NiO). Our research effort has focused on the effect of nickel on the critical current density in the YBCO/Ni composites. Four series of YBCO samples mixed with 0.3, 0.7, 1, 1.3, 2 and 3 wt% of high purity NiO were prepared, and optimized conditions for the melt process were established. These samples were characterized by resistivity, AC susceptibility and DC magnetization measurements. The highest magnetization critical current density (Jcm∼3×105 A/cm2 at T=4.2K and H=0 was observed in melt-processed samples with ∼ 1 wt% Ni (or -1.3 wt% NiO) subjected to a cooling rate of 2°C/hr from 1040°C to 980°C. This Jcm was found near the middle of the Ni-solubility range (about 2 wt% Ni is the solubility limit of Ni in YBCO) which may be attributed to the local Ni/Cu compositional fluctuation leading to an increased pinning force density in these composites.
High TC Superconducting Switch
Authors: Kalkur T. S. , Ward Dave 
Published: March 2011

ABSTRACTA switch has been developed which uses a thin film of Y-Ba-Cu-O as a switching element. The two important process parameters in the fabrication of the switch - contact resistance between a metal and a superconductor and the passivation of the superconducting films by SiO2 have been studied. The thin film of superconductor is patterned into a narrow line (gate) crossed by a metal control line with a deposited SiO2 as an insulation layer between them. When the control line carries current large enough to switch the gate into the normal state the gate is in the ‘off’ state. When no current is present, the gate is superconducting and it is in the ‘on’ state. The operation of the device was verified by testing at 77 K. Applications of the device include amplifiers, digital logic circuits, and microwave switches.
The Fabrication of High-TC Superconducting Wires, Tapes and Bulk Conductors
Authors: Briggs A , Denton I E , Hooper A , Lee J A , Jmattingley N 
Published: March 2011

ABSTRACTThe results of a UK-based industrial consortium, aimed at the development of high-Tcsuperconducting wires, tapes and bulk conductors, are reviewed. The powder-in-tube method has been used to fabricate 10's of metre lengths of bismuth-based, Ag-clad, single and multi-filamentary wires. Performance highlights include current densities of 23,000Acm-2 [7A] at 77K; (zero field) for 2223 bismuth-based wire and greater than 105Acm-2 [25A] and 104cm-2 at 4.2K, zero field and 15T, respectively, for 2212-based wire. Ag-backed, 2212, tape-cast conductors have carried currents of over 60A [80,000Acnrr-2] at 4.2K; (zero field). Bulk ceramic processing techniques, sol-gel chemistry and plasma-spraying have also been used to fabricate a range of YBCO and bismuth-based components. Currents in excess of 100A have been carried in bulk 2223 bismuth-based samples at 77K.
Superconducting Multilayer Structures Grown by All-Mbe
Authors: Bozovic I. , Eckstein J. N. , Klausmeier-Brown M. E. , Virshup G. F. , Rails K. S. 
Published: March 2011

ABSTRACTThin films of various Bi-Sr-Ca-Cu-O (2201, 2212,…, 2–2–11–12) compounds have been synthesized using atomic-layer-by-layer molecular beam epitaxy (ALL-MBE). Single-crystal films with excellent transport properties, smooth surfaces and atomically sharp interfaces in multilayer structures have been obtained. That made it possible to deposit virtually perfect ultrathin layers and superlattices, and fabricate hysteretic Josephson junctions from SIS multilayers.
Magnetic Anomaly in the YBa2Cu3O7 System at Low External Magnetic Fields
Authors: Bokhimi  
Published: March 2011

ABSTRACTMagnetization curves for low external magnetic fields of field-cooled superconducting YBa2Cu3O7 samples show an increase in the diamagnetic signal when the sample temperature is near the transition to the normal state. The Increase of the diamagnetic signal depends on the external magnetic field (H ≤ 13.5 Oe). The effect is observed when the samples are field-cooled, but not when they are zero-field-cooled, that means that it is related with the behavior of the vortex lattice.
A Thin Barrier Technology for the Integration of YBa2Cu3O7−x Thin Films to Semiconductors
Authors: Mesarwi A. , Wu N. J. , Fredricksen H. , Ignatiev A. 
Published: March 2011

ABSTRACTUltra-thin SiO2 barriers have been developed for application to the integration of thin films of YBa2Cu3O7−x (YBCO) superconductors to silicon. The SiO2 barriers are formed by the selective oxidation of Si with 2–5 ML yttrium overlayers. The Y-promoted SiO2, barrier formed by this technique is highly stoichiometric and is an effective buffer which prevents YBCO/substrate interdiffusion. The technique has been applied to YBCO on Si and has resulted in a YBCO transition temperature of TC=78°K for a 70Å Y-promoted SiO2 barrier.This technique has also been applied to the growth of multilayer YBCO films and fabrication of SIS junctions. For this purpose, a Y-promoted SiO2 barrier was prepared by the selective oxidation of a Y/Si/Y sandwich layer grown on thin fdm YBCO deposited on MgO by standard laser deposition. This resulted in a 20–40Å SiO2/Y2O3-, high quality barrier. Following barrier preparation, a second YBCO thin layer was deposited on the barrier yielding a YBa2Cu3O7−x-SiO2-YBa2Cu3O7−x (SIS) structure which was then patterned to yield 100μm diameter SIS junctions. Voltage-current measurements across the SIS junction have shown Joseph son junction behavior.
Pulsed Laser Deposition and Characterization of Superconducting Ba1−xKxBiO3 Thin Films
Authors: Platt C. E. , Teepe M. R. , Ciofl C. , Zhang H. , Dravid V. P. , Schweinfurth R. A. , Van Harlingen D. J. , Eades J. A. , Lin C. H. , Strother D. , Hammond R. 
Published: March 2011

ABSTRACTWe report on high quality Ba1−xKxBiO3 (BKBO) thin films grown by pulsed laser deposition. The best films exhibit resistive and magnetic transition temperatures of 28 K, with a transition width of 0.4 K and critical current densities above 106 A/cm2 measured at 5 K. Surface impedance is measured to be 1 mΩ. Films are single phase and highly oriented in the (100) direction and electron diffraction shows no other phases. Analysis using Moire' fringes shows films to consist of 100 nm size dislocation-free regions which show a high degree of in-plane epitaxy.
Processing and Properties of Silver-Clad Tl-Ba-Ca-Cu-O Wires and Tapes
Authors: Goretta K. C. , Wu C. -T. , Lanagan M. T. , Boling M. A. , Shi Donglu , Miller D. J. , Chen Nan , Hanewald W. G. , Sengupta S. , Wang Z. , Poeppel R. B. , Foong F. , Liou S. H. 
Published: March 2011

ABSTRACTTlBA2Cu3Ox and Tl2Ca2Cu3Ox powders were synthesized, loaded into Ag tubes, and worked into wires and tapes by drawing and rolling. All processing outside of furnaces was in a dry-N2 glovebox. All heat treatments were performed in O2. The Ag-clad wires fabricated from these powders exhibited onset of superconductivity at ≈118 K and critical current densities at 77 K of 2 × 103 to 4 ×103 A/cm2.
Research on Oxide Superconducting Wire
Authors: Ikeno Y. , Doi K. , Kamisada Y. , Hayashi K. , Ogawa T. 
Published: March 2011

ABSTRACTBy using the solid, liquid and vapor processes, such as doctor blade, laser pedestal growth, FZ, plasma spraying, ICB, CVD and laser ablation, wires and tapes were successfully fabricated. These experiments yielded the following results : Bi-2212 seven stranded wire with multi-layer structure by doctor blade method was prepared, and Ic of 270A (77K, OT) was achieved. Bi-2212 wires were prepared by laser pedestal growth, and Ic of 500A (77K, OT) was obtained in the case of 3mm in diameter. The a-b plane aligned Y-123 films-was deposited on Hastelloy, tape by laser ablation, and high Jc of 2.5×10 A/cm2 (77K, OT) and 2.2×10 A/cm2 (77K, 8T) were measured.
Control of a-Axis and c-AXIS Orientation of the YBa2Cu3O7−x Thin Films by Pulsed Laser Deposition
Authors: Sung Gun Yong , Suh Jeong Dae , Kang Kwang Yong , Lee Jeong Yong 
Published: March 2011

ABSTRACTWe have investigated the effect of substrate temperatures ranging from 680 °C to 800 °C on the orientation of pulsed laser deposited YBa2Cu3O7−x.(YBCO) thin films on (100) LaAlO3 substrates. X-ray diffraction studies indicate that there is a progressive change in the dominant orientation of the films from c-axis oriented (c-axis perpendicular to the substrate surface) to a-axis oriented (a-axis perpendicular to the substrate surface) grown as the substrate temperature is lowered. Two YBCO bilayers, which are the a-axis oriented YBCO film on the top of c-axis oriented YBCO film (a/c) bilayer and c-axis oriented YBCO film on the top of a-axis oriented YBCO film (c/a) bilayer, have been grown by in situ two step pulsed laser deposition and were characterized by scanning electron microscopy (SEM), Rutherford backscattering (RBS) spectrum, x-ray diffraction (XRD), and Tc measurements. Through SEM and XRD studies, double layer structures of the a/c and c/a bilayers were confirmed indirectly.
The Systematics of Irreversibility in Superconducting Thallium Cuprates
Authors: Tallon J. L. , Presland M. R. , Buckley R. G. , Mawdsley A. 
Published: March 2011

ABSTRACTThe irreversibility lines, Hirr(T), for the series of superconducting compoundsTlmA2CunO2+m+2n, where A is Ba or Sr, are measured between 0 and 1 tesla for m = 1,2 and n = 1,2,3 and 4 and show a marked steepening with decreasing anisotropy i.e. as m is lowered from 2 to 1. In addition, for m=2 material Hlrr(T) is observed to steepen with decreasing number of CuO2 layers. The hole dependence of the irreversibility line is also investigated in TI2Ba2CuO6+6 by changing the oxygen stoichiometry, 6. Hirr(T) progressively steepens with increasing hole concentration on the overdoped sida of Tc(max). These results are consistent with a model of flux motion arising from a crossover from 3-D vortex lines to 2-D pancake vortices which are decoupled in the c-direction, and provide guidance for materials selection and optimum doping.
Controlled Growth of Superconducting Oxide Films Using Pulsed Laser Deposition
Authors: Gupta A. , Chern M. Y. , Hussey B. W. 
Published: March 2011

ABSTRACT:Reflection high-energy electron diffraction (RHEED) has been used to monitor the homoepitaxial growth of SrTiO3 buffer layer, and subsequent heteroepitaxial growth of YBa2CU3O7-δ (YBCO) films, on (100) SrTiO3 by pulsed laser deposition (PLD). The RHEED pattern during initial growth of SrTiO3 becomes sharper and increases in intensity, suggesting that the smoothness of the substrate is improved by growth of the buffer layer. On the smooth surface, the growth of SrTiO3 occurs in a layer-by-layer mode as indicated by the intensity oscillations of the specular beam. YBCO films have been subsequently grown on the buffer layer using a combination of pulsed molecular oxygen and a continuous source of atomic oxygen, with the average background pressure maintained as low as 1 mTorr. A sharp streaky pattern, and intensity oscillations are also observed during growth of YBCO. The YBCO films after cooling down in 1 atm of O2 are superconducting, with zero-resistance temperature of 80 K.
Fabrication of Silicon-Based Shape Memory Alloy Micro-Actuators
Authors: Johnson A. David , Busch J. D. , Ray Curtis A. , Sloan Charles 
Published: March 2011

ABSTRACTThin film shape memory alloy has been integrated with silicon in a new actuation mechanism for micro-electro-mechanical systems. This paper compares nickel-titanium film with other actuators, describes recent results of chemical milling processes developed to fabricate shape memory alloy micro-actuators in silicon, and describes simple actuation mechanisms which have been fabricated and tested.
Adaptive Damping in Shape Memory TiNi during Cavitation
Authors: Jardine A. Peter 
Published: March 2011

AbstractRecent studies by this author and others has demonstrated that cavitation-erosion of NiTi coatings or bulk NiTi is exceptional. Studies were undertaken to ascertain whether this property is a consequence of either the general intermetallic properties of NiTi or by an adaptive stress-dissipation mechanism of the cavitation-generated shock wave by A microstructural mechanism related to the shape memory effect.In cavitation, an oscillating pressure field causes the formation and implosion of air bubbles. As a surface easily nucleates bubbles, the subsequent implosion of the bubbles generates stresses approaching several MPa, which are large enough to ablate material, and are also high enough to generate stress-induced Martensite or Austenite, depending on whether the applied stress is tensile or compressive. The implication is that the stress wave may be partially accommodated by the stress-induced transformation, which can dissipate the energy as heat on retransformation to the materials unstressed phase.Calculations concerning the variation of the cavitation-induced stresses and temperature distribution with depth into the TiNi coupled with the associated problems of heat transfer will be presented. It will be shown that an adaptive mechanism is plausible.
Ultimate Strain Measurement of Micromachined Membranes Using a Potentiometric Technique
Authors: Goforth R. C. , Ulrich R. K. , Leong Y. K. , Zhao G. 
Published: March 2011

ABSTRACTA potentiometric method for the measurement of ultimate strain of thin films is presented. In this method, an electric potential is applied between two electrodes located one on each side of the thin film under investigation. The electrodes are immersed in an electrolytic solution. The thin film acts as an electrical current barrier. To determine the ultimate strain, a controlled load is applied to the film. Cracking of the film causes a sharp rise in the current from an initial small leakage value. The applied load at the onset of cracking is used to calculate the ultimate strain.we have previously demonstrated the feasibility of the method for thin silicon nitride films deposited on aluminum strips. The method is very sensitive and can detect cracks too small to be observed with a microscope. We discuss extension of the method to the measurement of the ultimate strain of micromachined membranes. The load is applied by pressurizing one side of the membrane. Micromachined structures are used to determine residual stresses.
Alternative Materials for Micro-Electro-Mechanical Device Construction
Authors: Hackeit R. H. , Larson L. E. 
Published: March 2011

ABSTRACTIn order to integrate micro actuators with III-V semiconductor devices, we have devised Micro-Electro-Mechanical devices (MEM's), constructed from materials and processes common to existing III-V device processing. These processes are substantially different from silicon based processes because of the requirements for low temperature processing and the use of gold-based metallizations.Our material choices include, vacuum deposited and plated metal films, silicon oxide and nitride dielectric layers, and polyimide layers and structures. Sacrificial layers are implemented with photoresist rather than the more common silicon dioxide. The processes available are based on the ‘lift off’ of unwanted areas of the metal films, wet plating of metals through openings in photoresist masks, and wet and plasma etching of metals and dielectrics.This paper will discuss why we are using these materials, the process constraints imposed by the materials, the measurement of some of the material properties, and will relate some progress in applications.
Piezoelectric properties of 0-3 ceramic/polar polymer composites
Authors: Dias C. , Das-Gupta D. K. 
Published: March 2011

ABSTRACTFerroelectric ceramics such as PZT, while exhibiting strong piezoelectric effect, have the disadvantages of a high acoustic impedance, difficulty to miniaturize and not being suitable to broad band ultrasonic applications. Polar ferroelectric polymer such as PVDF and its copolymers which can be obtained in thin film form, have low mechanical Q and low acoustical impedance although their piezoelectric coefficients are significantly lower than those of the piezoelectric ceramics. Composites of piezoelectric ceramic powders, such as PZT and Calcium modified Lead Titanate (PT) in a matrix of P(VDF/TrFE) have been fabricated in our laboratory, in order to Investigate whether these materials could have the low acoustic, broad band properties of the polymers whilst retaining the high piezoelectric coefficients of the ceramics. In the present paper the results of a study of the electromechanical coupling factor (kt), the quality factor (Qm) as well as the gh and dh piezoelectric coefficients of these 0-3 composites poled both by corona and by the conventional method are given.
Organic Charge-Transfer Complexes for High Density Storage Using a Modified Scanning Tunneling Microscope
Authors: Yamaguchi Shoji , Valenzuela Carlos A. , Potember Richard S. 
Published: March 2011

ABSTRACTWe are investigating organometallic materials which exhibit a novel fieldinduced reversible switching phenomenon. Silver and copper salts of tetracyanoquinodimethane (TCNQ) and its derivatives, prepared as polycrystalline thick films and vacuum-deposited thin films, have been imaged using a scanning tunneling microscope (STM). We have recently produced images with molecular resolution of these materials. We also have demonstrated a field-induced, charge-transfer reaction driven by the electric field at the STM tip when the field generated by the STM exceeds the switching threshold of the organic charge-transfer complex. The phase transition induced by the STM tip appears as nanometer to micrometer-sized domains on the metal-TCNQ and derivatives surface. This STM-induced chemical reaction is being explored for use in a molecular-based information storage system.
Thin Film Heater on a Thermally Isolated Microstructure
Authors: Oh Seajin , Chu William , Cahill Sean 
Published: March 2011

ABSTRACTA microheater was fabricated on a thermally isolated silicon (Si) membrane and its electrical and thermomechanical properties were assessed. The sensor design was adjusted for good thermal isolation and good resistance to thermal shock. The heater was a platinum (Pt) thin-film meandering filament deposited with electron beam evaporation and patterned with lift-off methods. In order to operate the heater at high temperatures with minimum loss of Pt by evaporation, the heater was encapsulated with a ceramic film. During the heater operation, most of the heat was dissipated via conduction through the Si membrane which supported the multi-layered heater. When the Si membrane was completely etched away to suspend the heater, the power needed to heat the filament to strong incandescence (about 700–800°C) was 110 mW. Structural failure was not observed when the device was subjected to thermocycling up to approximately 500°C. The importance of the thermomechanical match of layers in a multi-layered heater structure, especially for use at high temperatures, is addressed.
Characterization of Sputtered Tungsten Silicide as a Micromechanical Material
Authors: Ger Muh-Ling , Brown Richard B. 
Published: March 2011

ABSTRACTRefractory metal silicides, such as tungsten silicide (WSix), have been used for integrated circuit interconnect and self-aligned MESFET gates because of their low resistivity and thermal and chemical stability. These same characteristics make refractory metal silicides interesting materials for prospective use in micromechanical structures. However, little information on residual stresses, elastic moduli, or other micromechanical properties has been available for refractory metal silicide films.This paper presents morphology and stress characteristics of sputter-deposited tungsten silicide films, including orientation-dependent variations, as functions of deposition parameters. The biaxial elastic modulus and thermal coefficient of expansion are found for our sputtered films. Stress-measurement methods and annealing are discussed. Released diaphragms of different sizes and shapes, having controlled residual stress, have been fabricated.
Mechanical and Piezoresistive Properties of Graphite-Filled Polyimide Thin Films
Authors: Frazier A. Bruno , Khan M. R. , Allen Mark G. 
Published: March 2011

ABSTRACTThe piezoresistive effect of materials is used as the basis for many types of microsensors. Polyimide, a material widely used in microelectronic fabrication, may be made to exhibit this effect by addition of small graphite particles to form a composite material. Polyimide / graphite based piezoresistive films have the advantage of being spin-castable, plasma-processable, highly chemically resistant, and thermally stable up to 400 °C in nitrogen atmospheres. In this work, piezoresistive polyimide films are formed by addition of various amounts (loadings) of graphite particles one micron in diameter or less to DuPont PI-2555 polyimide. Thin films of these materials are spin-cast on silicon wafers, and an in-situ load-deflection measurement technique is used to evaluate the following film properties: piezoresistive coefficient as a function of both strain and graphite loading; Young's modulus as a function of graphite loading; and residual film stress as a function of graphite loading. The observed piezoresistive coefficient is a strong function of graphite loading, with good piezoresistive properties exhibited in the loading range of 15–25 wt% graphite.
Smart Building Materials which Prevent Damage or Repair Themselves
Authors: Dry Carolyn M. 
Published: March 2011

ABSTRACTWe developed designs in which hollow porous fibers filled with chemicals release them into a matrix over time. A coating covering the fibers is degraded by chemicals, pH change, or broken by structural loading, thus, releasing the chemicals. These stimuli for release are the very agents of environmental attack.The design to alleviate cracking consists of hollow porous fiberglass fibers containing crack-closing chemicals. The chemicals are released from the fibers when the outer sheath cracks or the fibers flex due to loading. This is the ideal situation in which the agent of environmental degradation, namely loading, is the stimulus to release the repair chemical.The design to prevent corrosion consists of an anticorrosion chemical in hollow porous polypropylene fibers. Change in chloride ion concentration dissolves the polyol coating and allows the chemical to be released from the fiber wall. The cause of deterioration, change in chloride level which causes corrosion, is the sensor (coating deterioration) and also the activator for the remedial or preventive action (release of anticorrosion chemical).These are distributed systems responding to environmental stimuli for sensing and repairing when and where they are needed. The control of the amount of chemical released is being researched mainly as a function of coating design and also fiber type.
The Effect of Temperature and Pressure on Residual Stress in LPCVD Polysilicon Films
Authors: Oei D-G. , McCarthy S. L. 
Published: March 2011

ABSTRACTMeasurements of the residual stress in polysilicon films made by Low Pressure Chemical Vapor Deposition (LPCVD) at different deposition pressures and temperatures are reported. The stress behavior of phosphorus (P)-ion implanted/annealed polysilicon films is also reported. Within the temperature range of deposition, 580 °C to 650 °C, the stress vs deposition temperature plot exhibits a transition region in which the stress of the film changes from highly compressive to highly tensile and back to highly compressive as the deposition temperature increases. This behavior was observed in films that were made by the LPCVD process at reduced pressures of 210 and 320 mTORR. At deposition temperatures below 590 °C the deposit is predominantly amorphous, and the film is highly compressive; at temperatures above 610 °C (110) oriented polycrystalline silicon is formed exhibiting high compressive residual stress.