bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flux Pinning Defects Induced by Electron Irradiation in Y1Ba2Cu3O7–8 Single Crystals
Authors: Giapintzakis J. , Kirk M. A. , Lee W. C. , Rice J. P. , Ginsberg D. M. , Robertson I. M. , Wheeler R. 
Published: March 2011

ABSTRACTSingle crystals of R1Ba2Cu3O7–8, (R=Y, Eu and Gd), have been irradiated with 0.4–1.0 MeV electrons in directions near the c-axis. An incident threshold electron energy for producing flux pinning defects has been found. In-situ TME studies found no visible defects induced by electron irradiation. This means that point defects or small clusters ( ≤ 20 Å) are responsible for the extra pinning. A consistent interpretation of the data suggests that the most likely pinning defect is the displacement of a Cu atom from the CuO2 planes.
Epitaxial Superconductor Film Growth on Ultratffln Silicon Wafers for Infrared Detection
Authors: Li Q. , Fenner D. B. , Johansson M. E. , Hamblen D. G. , Hamblen W. D. , Lynds L. , Karrai K. , Liu S. , Dunmore F. , Drew H. D. , Zhang H. , Xu P. 
Published: March 2011

ABSTRACTEpitaxial YBCO/YSZ thin films have been successfully grown on ultrathin Si(100) wafers as part of an effort to fabricate infrared detectors which are both fast and highly responsive. Single crystal Si wafers with thicknesses ranging from 400 μm to 3μm are used as growth substrates. Detectors are fabricated by patterning the YBCO films into meanderline structures and their IR response is evaluated as a function of substrate thickness. So far, we have achieved a responsivity of 1750 V/W with a 10 Hz chopping rate on the 25 μm substrate, and rise/fall times as fast as 3 msec on the 3 μm substrate. We have also measured the low temperature IR transmission from 15 μm to 300 μm of both the YSZ buffered Si substrate, and the complete YBCO/YSZ/Si sample. This study indicates that silicon is a superior substrate for the fabrication of high performance infrared focal plane detector arrays.
High Tc Tri-Layers for Josephson Junctions
Authors: Eckstein J. N. , Bozovic I. , Klausmeier-Brown M. E. , Virshup G. F. 
Published: March 2011

ABSTRACTAtomic Layer-by-Layer Molecular Beam Epitaxy (ALL-MBE) of high Tc superconducting films can be used to grow defect-free and flat multi-layer structures in which superconducting molecular layers are stacked with molecular layers having other electronic properties. In particular, tri-layers consisting of c-axis Bi2Sr2CaCu2O8 base and counter electrode layers, each several hundred angstroms thick, have been grown separated by single molecular layers of metastable compounds such as Bi2Sr2Can-1CunO2+4 where n ranged from 5 to 11. Furthermore, the electronic properties of such barrier layers have been modified by doping with trivalent cations. Using such structures, tri-layer Josephson junctions have been fabricated which exhibit hysteretic I - V characteristics. Other doping schemes have given insulating layers which dominate c-axis transport, demonstrating the ability of this technique to grow thin, 25 Å, single molecular layers that are free of pinholes.
Transmission Electron Microscopy and X-Ray Diffraction Studies of a,b-Axis Oriented YBa2Cu3O7-δ Films
Authors: Streiffer S. K. , Lairson B. M. , Zielinski E. M. , Bravman J. C. 
Published: March 2011

ABSTRACTQuantitative high resolution transmission electron microscopy and x-ray diffraction have been used to study films of YBa2Cu3O7-δ grown on LaAlO3 substrates at low substrate temperatures. Based on analysis of high-resolution micrographs, it is asserted that the films are b-axis oriented near the film-substrate interface, and switch to a-axis oriented at some distance away from the interface, in a manner which varies from sample to sample. Thus, the films undergo a change in orientation as a function of distance from the substrate. X-ray diffraction confirms that these films contain both a-axis oriented and b-axis oriented components normal to the plane of the substrate, consistent with the high-resolution microscopy data.
Effects of Controlled Defects on the Vortex-Solid Melting Transition of Y-Ba-Cu-O Single Crystals
Authors: Jiang W. , Yeh N. -C. , Reed D. S. , Kotlani U. , Tombrello T. A. , Rice A. P. , Holtzberg F. 
Published: March 2011

ABSTRACTWe report systematic studies of the dc transport properties in proton-irradiated Y-Ba-Cu-O single crystals. We find that the onset of vortex dissipation in moderately irradiated samples is associated with the occurrence of a second-order vortex-solid melting transition. In addition, the decreasing zero-field transition temperature and increasing critical current density with the increasing defects reveal the effects of disorder on reducing the electron mean-free-path and on increasing the pinning density.
Microwave Impedance Studies on High Temperature Superconductors Using a Dielectric Sapphire Resonator in High Magnetic Fields
Authors: Kriplani Ushma , Yeh N.-C. , Jiang W. , Reed D. , Strayer D. M. , Gupta A. , Holtzberg F. , Kussmaul A. 
Published: March 2011

ABSTRACTThe vortex dissipation in an Nd-Ce-Cu-Ol epitaxial film is measured at microwave frequencies using the high-Q modes of a sapphire ring resonator, over a large range of temperatures and external DC magnetic fields. The results are qualitatively consistent with a generalized thermally-activated flux-flow (TAFF) model.
Simulation of vortex-line pinning by defects in the Y-Ba-Cu-O system
Authors: Jamison R. , Burmester C. P. , Wille L. T. , Gronsky R. 
Published: March 2011

ABSTRACTThe finite temperature properties of a two-dimensional flux lattice are studied by Monte Carlo simulation, with particular attention to the effects of twin-boundaries. The parameters selected are appropriate for the YBa2Cu3O7 high-temperature superconducting system. The intrinsic properties of the vortex state are investigated by monitoring system evolution at fixed temperature and applied magnetic field. By varying the temperature, the loss of type-II superconductivity via fluxoid lattice melting is also examined. The introduction of model defects induces the creation of metastable and glassy states which reduce overall hexatic order but are found to enhance system resistance to flux-lattice melting.
Thin Film Ag/YBCO Multistructures for Metal Contact Applications
Authors: Powers M. , Gronsky R. , Washburn J. 
Published: March 2011

ABSTRACTA technique is presented where Ag is initially sputter deposited on a single crystal ceramic substrate followed by in situ deposition of YBa2Cu3O7δ The resulting microstructure shows Ag islands amidst a c-axis oriented YBCO film, apparently with intimate contact between the YBCO and substrate. This morphology appears ideal for electrical contact to the {hko} surfaces of the superconductor with current carrying CuO planes in maximum contact with the Ag.
Environmental Testing of High Tc Superconductive Thermal Isolators for Space-Borne Cryogenic Detector Systems
Authors: Wise Stephanie A. , Buckley John D. , Randolf Henry W. , Verbelyi Darren , Haertling Gene H. , Hooker Matthew W. , Selim Raouf , Caton Randall 
Published: March 2011

ABSTRACTNASA's requirements for space-based cryogenic detector systems include the long-term storage of the liquid helium cryogen necessary for the optimized performance of far-infrared (IR) detectors. Significant heat loads on the liquid helium dewars exist due to the numerous electrical connections to the detectors, accounting for approximately 20 percent of the total heat load for some systems. High temperature superconductor lead assemblies are under development to replace the existing manganin wires connecting instruments at 80 K to the detector array at 4.2 K. These superconductive elements provide adequate current transport properties, while decreasing the thermal load on the liquid helium dewar. As a result, mission lifetimes can be extended by 10 percent or more.Thick films of the superconductive material on low thermal conductivity substrates (e.g. yttria stabilized zirconia and fused silica) have been proposed to replace the existing lead assemblies. This work describes some of the design constraints on such a device as well as preliminary analyses of the effects of vibration, gamma irradiation, and long term exposure to high vacuum and liquid nitrogen encountered in operating such a device in space.
Temperature and Frequency Dependence of the Infrared Absorption in Three Kinds of Bi-Based Compounds
Authors: Hayashi Y. , Harada Y. , Sasakura H. , Nagayama M. 
Published: March 2011

ABSTRACTInfrared absorption measurements have been made in three kinds of Bi compounds of a high-Tc family mainly by making use of powdered samples. Two of them are superconductors with Tc's of 108 K and 82 K, respectively, and the remaining one is a semiconductor. In each of the superconducting compounds, there appears Mid-Infrared absorption band: No such absorption band is found in the semiconducting compound. At Far-Infrared region, many absorption peaks due to phonons are clearly detected in all of these samples. Some of the phonon modes have been identified. At very low energy region, free carrier absorption appears in superconductors. Only this part of the absorption shows a temperature dependence. Absorption intensity decreases as the temperature decreases.
Evidence for Weak Link Effects in Epitaxial Thin Films of YBCO on LaAlO3
Authors: Bohandy J. , Kim B. F. , Moorjani K. , Adrian F. J. 
Published: March 2011

ABSTRACTEvidence of weak link effects in epitaxial thin films of YBa2Cu3O7-yon LaAlO3 is obtained from magnetically modulated resistance (MMR) measurements. This result suggests that weak links could provide a mechanism for the residual microwave loss in high quality superconducting thin films which contain predominantly low angle grain boundaries.
Multilayers and Multiturn Coils of YBaCuO/MgO/YBaCuO Layers Prepared by Multitarget Sputtering
Authors: Wunderlich R. , Kleinitzke J. , Meyer B. , Müller J. 
Published: March 2011

ABSTRACTThe deposition of large area multilayers with smooth surfaces is an important topic for the realisation of high quality multiturn coils for flux transformers. We have developed a co-sputtering process from two metallic targets for the deposition of large areas of extremely smooth YBaCuO thin films. Conditions for epitaxial growth of MgO layers on YBaCuO have been investigated. Epitaxial multilayers with good electrical properties (Tc,o > 82 K) have been fabricated.
Plasma Impulse CVD Deposited TiO2 Waveguiding Films: Properties and Potential Applications in Integrated Optical Sensor Systems
Authors: Heming M. , Danielzik B. , Otto J. , Paquet V. , Fattinger Ch. 
Published: March 2011

ABSTRACTPlasma impulse CVD deposited titania thin films, deposited at low substrate temperatures, exhibit low volume losses of < 0.2 dB/cm and high environmental stability. Their use in novel concepts for integrated optical immunosensors is discussed.
Sol-Gel Coatings for Electrochromic Devices
Authors: Macedo M. A. , Dall'Antonia L. H. , Aegerter M. A. 
Published: March 2011

ABSTRACTAll solid state electrochromic smart windows with the configuration glass/ITO/WO3/electrolyte/TiO2-CeO2/ITO/glass have been realized. These devices have potential applications in architectural and automotive fields to regulate the transmission and reflection of the radiant energy. The ion storage electrode TiO2–CeO2 have been realized by sol-gel process and its electrochemical properties are studied as a function of various parameters (thickness, heat treatment, etc.). The electrochemical and optical performances of two cells are reported.
Alignable Deposition of Thin Film Semiconductor Materials for Integrated Micro-Opto-Electronic Systems
Authors: Camperi-Ginestet C. , Jokerst N. M. , Augustine G. , Hargis M. , Allen M. 
Published: March 2011

ABSTRACTThe selective and alienable deposition of patterned thin film epitaxial GaAs/GaAlAs and InP/InGaAsP devices onto host substrates such as silicon for low cost hybrid integrated micro-opto-electronic systems is reported. Using a combination of semiconductor etch layers and selective etches, the epilayers can be separated from the growth substrate. We use a thin polyimide diaphragm as the transparent transfer medium for these epitaxial materials and devices. Each of these thin film devices or a group of these devices on the polyimide is optically aligned and selectively deposited onto the host substrate. Using this technique, GaAs and InP-based light emitting diodes and optical detectors which are microns thick were grown on lattice matched GaAs and InP substrates, lifted off, aligned and selectively deposited onto a silicon host substrate. The devices were then electrically contacted and tested using standard microelectronic fabrication and testing techniques. This method also enables the manufacturable, sparse distribution of costly photonic devices or the deposition of aligned arrays of devices to fabricate larger arrays. The integration of these light weight devices with microsensors and microactuators will foster micro-opto-electro-mechanical integration.
Characterization of Thin Films using Micromechanical Structures
Authors: Pratt R. I. , Johnson G. C. , Howe R. T. , Nikkel D. J. 
Published: March 2011

ABSTRACTMicromechanical structures designed for material characterization through analysis of their nonlinear dynamic response are presented. The structures consist of a rigid movable mass supported by beams which are attached to the wafer substrate. The structures are designed so that they are geometrically constrained, which is the source of their nonlinearity. The nonlinearity is shown to be well modeled by Duffing's equation for a stiffening spring and it is this model which is used to fit the test data to the desired mechanical properties, namely Young's modulus, intrinsic stress and damping.
Determination of Eigenstresses from Curvature Data
Authors: Ferrari Mauro , Weber Marie 
Published: March 2011

ABSTRACTCurvature measurements are generally employed in conjunction with elementary structural analysis to estimate deposition stresses in miniaturized electro-mechanical systems. In this paper the validity of this procedure is discussed by presenting a closed form solution for a bilayer subject to nonuniform intrinsic straining, and comparing the exact stress-curvature relations with the oft-used formulae of Stoney and Brenner-Senderoff.
Theoretical Calculation for the Young's Modulus of Poly-Si and a-Si Films
Authors: Guo Shuwen , Zou Daowen , Wang Weiyuan 
Published: March 2011

ABSTRACTA newly theoretical calculation for the Young's modulus Eyof poly-Si and a-Si thin films based on the combination of grain and grain boundary effects as well as the dependance of crystalline orientations is presented. The calculated results are in agreement with the experimental results in a wide range of grain size and hydrogen concentrations published in the literatures. The reason for aberration among experimental data of poly-Si and a-Si films caused by different hydrogen concentrations, texture and grain size has been discussed. The results offer a better understanding of. the effects of film structures on elastic properties of poly-Si and a-Si films.
Ferroelectric Thin Films for Microelectromechanical Device Applications
Authors: Polla D. L. , Robbins W. P. , Tamagawa T. , Ye C. 
Published: March 2011

ABSTRACTFerroelectric thin films of the lead zirconate titanate family have been integrated with silicon-based micromachined structures in the fabrication of microelectromechanical devices. Sol-gel deposition techniques have been applied in the formation of ferroelectric thin films with high piezoelectric and pyroelectric coefficients for physical forces sensors and infrared detectors, respectively. Knowledge of both electrical and mechanical properties is important in realizing microelectromechanical devices with predictable performance. This pape reports piezoelectric coefficient, pyroelectric coefficient, dielectric constant, and Young's modulus for lead zirconate titanate and lead titanate thin films.
Physical, Electrical, and Piezoelectric Properties of Hot-Forged Sr2(NbTa)2O7 Ceramics
Authors: Fuierer Paul A. , Shrout Tom R. , Newnham Robert E. 
Published: March 2011

ABSTRACTSolid solution compositions of Sr2(NbxTa1−x)2O7 ceramics with Tr ranging from 450°C to 1342°C were fabricated utilizing a hot-forging technique to achieve preffered grain orientation and thus enhance poling. Translucent samples with greater than 99% theoretical density were obtained using this process. Depending on composition, the degree of orientation as determined by x-ray diffraction was found to be 75% to 95%. The thermal expansion, resistivity, and dielectric constant were shown to be very anisotropic. The direction perpendicular to the forging axis proved to be the ferroelectric “easy” direction, exhibiting hysteresis behavior. Piezoactivity in PLS polycrystals was measured for the first time. Hot-forged samples were electrically poled and the electromechanical properties determined using the five different modes of vibration. For Sr2(Nb0.5Ta0.5)2O7: N24=1504 Hz-m, s44=18.2×10-12m2/N, k24=3.0%, d24=2.6 pC/N, g24=6.3×10-3 Vm/N, and Qm=1100. This material was also shown to resist depoling when exposed to temperatures as high as 650°C.
Stress and Microstructure in Phosphorus Doped Polycrystalline Silicon
Authors: Krulevitch P. , Johnson G. C. , Howe R. T. 
Published: March 2011

ABSTRACTThe research presented here is an investigation of the effects of phosphorus doping on residual stresses and microstructure in polycrystalline silicon. Undoped polycrystalline silicon films were deposited on phosphosilicate glass layers and annealed at 1050 °C for 5 to 60 minutes. The stress gradient through the film thickness was measured from wafer curvature, and microstructure was examined with cross-sectional TEM. A 20 minute anneal is sufficient for stress relief in initially tensile films and produces a uniform microstructure consisting of 0.1-0.2 µm equi-axed grains.
Zeolates: A Coordination Chemistry View of Metal-Ligand Bonding in Intrazeolite MOCVD Type Precursors and Semiconductor Nanoclusters
Authors: Ozin Geoffrey A. , Bowes Carol L. , Steele Mark R. 
Published: March 2011

ABSTRACTVarious MOCVD (metal-organic chemical vapour deposition) type precursors and their self-assembled semiconductor nanocluster products [1] have been investigated in zeolite Y hosts. From analysis of in situ observations (FTIR, UV-vis reflectance, Mössbauer, MAS-NMR) of the reaction sequences and structural features of the precursors and products (EXAFS and Rietveld refinement of powder XRD data) the zeolite is viewed as providing a macrospheroidal, multidendate coordination environment towards encapsulated guests. By thinking about the α- and β-cages of the zeolite Y host effectively as a zeolate ligand composed of interconnected aluminosilicate “crown ether-like” building blocks, the materials chemist is able to better understand and exploit the reactivity and coordination properties of the zeolite internal surface for the anchoring and self-assembly of a wide range of encapsulated guests. This approach helps with the design of synthetic strategies for creating novel guest-host inclusion compounds having possible applications in areas of materials science such as nonlinear optics, quantum electronics, and size/shape selective catalysis.
Double Rotation 23Na NMR Study of Guest-Host Interactions and Nanoscale Assemblies in Sodium Zeolite Y
Authors: Jelinek R. , Ozkar S. , Ozin G. A. 
Published: March 2011

ABSTRACT23Na double rotation NMR (DOR) provides information on site-specific adsorption of guest molecules within the porous framework of sodium zeolite Y. Anchoring of molybdenum-hexacarbonyl to extraframework Na+ cations in particular locations within the large α-cavities is detected. Changes of the chemical environments of the Na+ cations are observed upon loading trimethylphosphine molecules. Spin-lattice relaxation measurements yield insight on dynamic aspects of the anchoring sodium cations.
Ultrafast Excited-State Dynamics in a Fluoro-Aluminum Phthalocyanine Thin Film
Authors: Williams V. S. , Armstrong N. R. , Mazumdar S. , Sandalphon  , Peyghambarian N. 
Published: March 2011

ABSTRACTUsing femtosecond pump-probe spectroscopy, bleaching of the π-π* absorption Q-band, and photo-induced absorption on the high energy side of the Q-band, have been observed and time-resolved in a nearly-amorphous thin film of fluoro-aluminum phthalocyanine. Following excitation, the induced absorption signal develops as the absorption saturation signal diminishes, suggesting exciton decay into a subgap state. The different bimolecular decay dynamics observed for the absorption saturation (τeff ≈700 fs) and induced absorption (τeff ≈ 2 ps) signals support this conclusion. Possible origins of the subgap state are discussed. In addition, polarization-dependent spectral hole burning is observed at very early times. These results suggest the need for exploration of thin phthalocyanine films which are ordered in three dimensions over distances of at least 200–300 Å. Initial femtosecond results for epitaxially-grown chloro-indium phthalocyanine structures, which meet these criteria, are similar to those for the nearly-amorphous film, but indicate an additional polarization-dependent photo-induced absorption within the Q-band.
Polyion Complexed Langmuir-Blodgeet (LB) Films for Optical Memory
Authors: Fujihira Masamichi 
Published: March 2011

ABSTRACTA stable monolayer was formed by spreading a chloroform solution of a photosensitive ionic amphiphilic compound on an aqueous subphase containing an ionic polymer with opposite charge. In addition to the increase in stability, the cross sectional area of the amphiphilic molecule usually increased on polyion complexation from that of the same amphiphilic molecule in the absence of the ionic polymer. Deposition of the monolayer onto the solid substrate as a very homogeneous LB film was possible. The increase in molecular area allows various photochemical reactions, which otherwise do not occur due to the steric hindrance, to proceed in the resulting LB films. A rapid decrease in emission of the polyion complexed pyrene LB films was observed upon UV irradiation in air. Application of this very sensitive quenching procedure to optical memory will be also presented.
Optical Properties of Lanthanide Metal Ion Polymer Complexes
Authors: Okamoto Yoshi , Kido Junji 
Published: March 2011

ABSTRACTThe fluorescent characteristics of lanthanide chelates are of considerable interest in connection with electronic energy transfer processes and with their use in laser systems. We have synthesized various chelating groups, such as diketone and bypyridyl containing polymers and prepared their Tb3+ and Eu3+ complexes. Their fluorescent properties in connection with a possible laser action were investigated.Electroluminscence (EL) in organic compounds has been investigated from fundamental as well as practical point of views. Various organic dyes were utilized as emitter materials in EL devices. In these examples, owing to the broad nature of the luminescence spectra of organic dyes, the luminescent colors are dull. We have utilized lanthanide metal ion complexes as a luminescent emitter.Tb and Eu ion complexes emitted sharp green and red light, respectively. The configuration of the EL cell and experimental results are described.