bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of Ground State Neutral and Ion Transport During Laser Ablation of 1:2:3 Superconductors by Transient Optical Absorption Spectroscopy
Authors: Geohegan David B. , Mashburn Douglas N. 
Published: March 2011

AbstractOptical absorption in the plume produced by excimer laser ablation of Y1Ba2Cu3O7‐x under film growth conditions has been observed for the first time and used to characterize the transport of ground state Y, Ba, and Cu neutrals as well as Y+ and Ba+ ions. Spatially and temporally resolved absorption measurements (0.6 mm, 20 ns resolution) indicate significant ground state number densities at times following the laser pulse that are up to an order of magnitude longer than the duration of fluorescence from excited states. Time‐of‐flight absorbance profiles result in velocity distributions that are broadened significantly toward lower velocities and reveal a low velocity component (<10 5 cm s_1) to the ablation process which is not observed using emission spectroscopy. Electric ion probe measurements of the time dependence of Y+ ions confirm the existence of the new, slow velocity component. Electron densities >1016 cm‐3 in the white plasma close to the pellet have been estimated using spectrally broadened emission lines. The effects of oxygen ambient pressures and the detection of YO, BaO, and CuO also are reported. This technique is applicable as an situ monitor of the kinetic energy of ablated species during low temperature deposition of epitaxial 1:2:3 superconducting thin films.
Pulsed Excimer Laser Deposition of YBaCuO and BisrCaCuO Compounds : Material Distribution and Stoichiometry
Authors: Fuchs Claude , Fogarassy Eric 
Published: March 2011

AbstractWe investigate, in this study, the laser evaporation processes for the deposition of YBaCuO and BiSrCaCuO compounds, using a pulsed ArF (193 nm) excimer laser. The deposition parameters, especially those which are relevant to the geometrical configuration and optical arrangement of the experimental set-up and laser irradiation conditions are examined in details.
A Study of the In Situ Epitaxial Growth of the 123 Ybco Films from a Stoichiometric Target by Rf Magnetron Sputtering
Authors: Meng R. L. , Wang Y. Q. , Sun Y. Y. , Gao Li , Hor P. H. , Chu C. W. 
Published: March 2011

AbstractThe synthesis parameters have been systematically examined for the in situ growth of high temperature superconducting Y‐Ba‐Cu‐0 thin films from a stoichiometric target by rf magnetron sputtering. By properly adjusting the deposition temperature, the total sputtering (O2+Ar)‐pressure and the O2‐partial pressure, we have reproducibly obtained 123 YBCO films with a zero resistivity temperature Tcz = 84 K and a transition width of 3 K°. The films so obtained have excellent surface morphology and a surface roughness better than ∼ 5 nm.
Highly Oriented Yba2Cu3O7-X Thin Films Prepared by Unbalanced Dc Magnetron Sputtering From a Single Stoichiometric Target
Authors: Savvides N. , Andrikidis C. , Hensley D.V. , Drivers R. , Macfarlane J-C , Tan N.X. , Bourdillon A.J. 
Published: March 2011

AbstractHighly oriented films of YBa2Cu3O7‐x have been reproducibly prepared with the correct metal stoichiometry by dc magnetron sputtering from a single target of stoichiometric composition. To circumvent the resputtering effects, the magnetron used an unbalanced magnetic field configuration to direct the plasma away from the substrate. Typical films have sharp superconducting transitions with Tc up to 93 K and △TC(90%.‐10%.)=0.5 K, metallic resistivity above the transition with ρ300/ρ100=2‐4, and Jc>1.5xl06 A cm‐2 at 4.2 K. The temperature dependence of J,. obeys the flux creep model with activation energy U(0)=75 meV.
Growth and Characterization of La2-XSrXCuoY and Bi2-XSr2-ZCuoy Crystals
Authors: Osofsky M.S. , Cohn J.L. , Lechter W.L. , Skelton E.F. , Qadri S. B. , Hoff H.A. , Browning V.M. 
Published: March 2011

AbstractIn order to grow large single crystals of the La2‐xSrxCuOy and Bi2+xSr2‐zCuOy families of high Tc superconductors, we have studied the relationships between nominal Sr composition in the starting materials and the Sr compositions of the resulting products. We present growth, x‐ray, and composition data for these samples.
Properties of Thin Films of Yba2Cu3O7 Prepared by Coevaporation of Y, Cu and Baf2
Authors: Raistrick I. D. , Cooke D. W. , Beery J. G. , Garzon F. H. , Javadi H. , Maley M. P. , Rollett A. D. , Roy T. , Sinha D. N. , Wilde D. K. 
Published: March 2011

AbstractThe properties of thin films prepared by coevaporation of Y, Cu and Ba.F2, followed by post anneals in O2/H2O, are described. In particular, we emphasize what is known about. the relationship between the processing variables and the physical and chemical structure of the resulting films.
Y1Ba2Cu3O7‐x Films from Nitrate Solution using Rf Plasma Deposition
Authors: Shah A. , Haugan T. , Witanachchi S. , Patel S. , Shaw D. T. 
Published: March 2011

AbstractA nitrate solution of Y, Ba and Cu was atomized and introduced into an inductively coupled argon ‐ oxygen plasma operated at 4.4 kW and 13.56 MHz under atmospheric pressure. As‐deposited superconducting films were grown on (100) YSZ substrates heated to 650°C. Critical temperatures of 85 K and critical current densities of 7.0 x 104 amp/cm2 at 77 K have been achieved. X‐ray diffraction shows the films to be oriented with the c‐axis perpendicular to the substrate surface. The effects of process parameters, solution composition, and aerosol concentration on the superconducting properties and microstructures will be discussed.
Processing and Characterisation of Single‐Phase Superconducting Thin Films in the Bi‐Sr‐Ca‐Cu‐O System from Chemical Precursors
Authors: Golden S. J. , Bloomer T. E. , Lange F. F. , Segadaes A. M. , Vaidya K. J. , Olson W. L. 
Published: March 2011

AbstractThin films in the Bi‐Sr‐Ca‐Cu‐O system have been synthesized from liquid ethyl hexanoate precursors by spin pyrolysis. An extensive solid solution range was determined for the two Cu‐layer phase through the study of c‐axis oriented, single‐phase thin films fabricated on single‐crystal MgO (100). Extensive cation non‐stoichiometry was observed in all cases. The variation of important thin film properties with composition within the solid solution range have been described.Utilising the results from the thin film study together with data relating to liquid formation in mixtures of bulk material a working model describing the formation of the two‐layer phase has been formulated. The two‐layer phase is formed as the result of precipitation from a fugitive liquid at temperatures exceeding 730 *C.
A Study of Grain Boundaries in High TC Superconducting Yba2Cu3O7-x Thin Films Using High Resolution Analytical Stem
Authors: Shin D. H. , Silcox J. , Russek S. E. , Lathrop D. K. , Buhrman R. A. 
Published: March 2011

AbstractGrain boundaries in thin films of high Tc YBa2Cu3O7-x superconductors have been investigated with high resolution scanning transmission electron microscope (STEM) imaging and nanoprobe energy dispersive x-ray (EDX) analysis. Atomic resolution images indicate that the grain boundaries are mostly clean, i.e., free of a boundary layer of different phase or of segregation, and are often coherent. EDX microanalysis with a 10 Å spatial resolution also indicates no composition deviation at the grain boundaries.
Structural Defects in Thin Films Of High TC Superconductors
Authors: Ramesh R. , Hwang D.M. , England P. , Ravi T.S. , Chen C.Y. , Inam A. , Dutta B. , Nazar L. , Venkatesan T. 
Published: March 2011

AbstractIn this short report, we describe some of the structural defects present in laser deposited Y‐Ba‐Cu‐O thin films. Many of the defects observed are polytypoidic variants, related to the layered structure of these cuprates. One possible model by which flux pinning can be achieved is presented.
Microstructural Evolution of Ba2Ycu3O7 Superconductor by Electron Irradiation in a Transmission Electron Microscope
Authors: ShiraiShi Kensuke , Itoh Hiroshi 
Published: March 2011

AbstractMicrostructural changes in a Ba2YCu3O7 pellet were continuously observed during electron irradiation in a transmission electron microscope operating at 200 kV. Twin lamellae of 2~10 nm in thickness with 1~50 nm spacings were seen parallel to the lattice image of (001) plane with 1.17 nm in lattice spacing. The tip of the twin was lenticular and the (001) lattice fringes were distorted around the tip. Upon intense electron beam illumination, the lamellae faded at the tip and the thickness gradually decreased which increased the spacing in the high density region. Defect clusters of about 10 nm in size were produced in the very early stage of electron illumination.
Critical Current Density of Narrow Superconducting Thin Films Fabricated by Laser Ablation Techniques
Authors: Song L. W. , Kao Y. H. , Ying Q. Y. , Zheng J. P. , Kwok H. S. , Zhu Y. Z. , Shaw D. T. 
Published: March 2011

AbstractThe variations of critical current density Jc of narrow Y‐Ba‐Cu‐O films as a function of temperature and magnetic field are investigated. Films with thickness of 150‐200 nm and width of 20‐100 urn were prepared by laser ablation and laser etching. For t (=T/TC) < 0.75, the temperature dependence of Jc shows a (1‐1) linear behavior, in sharp contrast to that of a Josephson junction. Near Tc, Jc varies with (1‐ t)n where n=3/2 or 2 depending on the morphology of films. The magnetic field dependence of Jc above a characteristic field value Hc’ can be described by a model based on flux creep.
Critical Current Density, Flux Creep, and Microstructure in A Bi-Sr-Ca-Cu-O System
Authors: Shi Donglu , Boley M. S. , Chen J. G. , Xu Ming , Fang M. M. , Welp U. , Vandervoort K. , Hong J. M. 
Published: March 2011

AbstractWe measured magnetization hysteresis and zero-field-cooled magnetic relaxation for liquid-quenched Bi-Sr-Ca-Cu-O samples at various temperatures. We found that there is a close correlation between the magnetic behavior and the microstructures of the samples. The magnetization hysteresis greatly increases in the samples with a large amount of crystal defects such as precipitates and stacking faults in the matrix of the material. We also found that the flux creep is reduced as a result of these microstructural changes.
Ir Laser-Induced Deposition of Silicon Thin Films
Authors: Gattuso T. R. , Meunier M. , Adler D. , Haggerty J. S. 
Published: March 2011

ABSTRACTThe deposition of a-Si:H by means of CO2 laser-induced pyrolysis of silane gas is described. Deposition rates were found to increase with increasing silane flow rate, reactor pressure, laser power and substrate temperature. Spin density decreased and both optical gap, and hydrogen content increased with decreasing substrate temperature. Electrical conductivities are reported.
Submicrometer-Linewidth Laser Doping
Authors: Tsao J. Y. , Ehrlich D. J. 
Published: March 2011

ABSTRACTDopant patterns of 250-nm linewidth have been written in silicon by localized heating with a cw laser beam, and then transferred into positive and negative surface-relief patterns by preferential etching. The tightly focused beam both generates free dopant atoms and simultaneously promotes solidstate diffusion into the substrate. Because of the nonlinear dependence of diffusion rates on temperature, the linewidths of the patterns are substantially narrower than those of both the temperature and the laser-beam profiles on tile surface. In addition, an enhancement is observed in diffusion rates under the strong thermal gradients associated with highly localized heating.
Laser-Pulsed Plasma Chemistry: Surface Oxidation of Niobium
Authors: Marks R.F. , Pollak R.A. , Avouris Ph. 
Published: March 2011

ABSTRACTLaser irradiation of a solid surface under an oxidizing ambient gas can activate localized, heterogeneous chemical reactions which modify the surface. Under suitable conditions, the laser initiates a reactive plasma near the gas/solid interface. This plasma mechanism is proposed as the basis for a new surface chemical technique which we denote laser-pulsed plasma chemistry (LPPC). LPPC experiments on niobium metal under one atmosphere of oxygen employed a pulsed CO2 laser and displayed single-pulse, self-limiting, oxide growth. Product oxide thickness increased with optical intensity. Surface layer thickness and chemical composition were determined for oxide layers between 1 nm and 5 nm thick using x-ray photoelectron spectroscopy (XPS or ESCA). Composition of these niobium oxide (Nb2O5−δ) surfaces was similar to the composition produced by RF plasma oxidation, but the valence defect, δ, for LPPC oxides was approximately two to five times lower. At high laser intensity (≥4 × 106 W/cm2), direct optical heating or plasma-mediated thermal coupling to the solid activates interdiffusion at the oxide/metal interface.
Laser Chemical Etching of Conducting and Semiconducting Materials
Authors: Chuang T. J. 
Published: March 2011

ABSTRACTThe purpose of the paper is to examine the basic processes involved in the laser-enhanced chemical etching of solids. Specifically, the process of chemisorption, the reaction between the adsorbate and substrate atoms and the vaporization of product species affected by the laser radiation are discussed. It is shown that the laser method can provide important insight into the gas-surface reaction mechanisms. In addition, a number of examples are given to demonstrate the potential of the technique for applications to material processing. Some current studies on the laser-induced chemical etching of materials relevant to microelectronics are reviewed. Certain practical experimental approaches are also considered.
Molecular Composites of Rodlike/Flexible Polyimides
Authors: Rojstaczer S. R. , Yoon D.Y. , Volksen W. , Smith B.A. 
Published: March 2011

ABSTRACTMixtures of a rodlike and a flexible polyimide were prepared by solution-blending of the respective poly(amic alkyl ester) and poly(amic acid), followed by solvent evaporation and thermal imidization. The size scale of the phase separation, as measured by light scattering, is primarily set during the demixing of the precursor polymers, with no significant coarsening observed due to the imidization performed at 400°C. The observed variation of the domain size with parameters such as composition, molecular weight and film thickness is discussed in terms of the miscibility of the precursor polymers as well as the thermal history to which these were exposed.
Miscibiuty in Blends of Polybenzimidazole and Fluorine Containing Polyimides
Authors: Yamaoka Hiroaki , Aubrey Norman E. , MAcknight William J. , Karasz Frank E. 
Published: March 2011

ABSTRACTBlends of polybenzimidazole (PBI) with either of two fluorine-containing polyimides were prepared by casting from solution and by precipitation. Dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC) were used to study miscibility in the two blend systems.The blends of PBI with the first polyimide, the polysulfonimide Pl-1, consisted of a single phase when the blends contained less than 30 wt% Pl-1; above 50 wt% Pl-1, phase separation occurred even at room temperature. The PBI blends containing the second polyimide, Pl-2, were immiscible.
X-Ray Reflectivity and Fluorescence Measurements From Polystyrene-Co-Bromostyrene/Polystyrene Interfaces
Authors: Sokolov J. , Rafailovich M. , Zhao X. , Yun W.B. , Jones R.A.L. , Kramer E.J. , Composto R.J. , Stein R.S. , Bommannavar A. , Engbretson M. 
Published: March 2011

ABSTRACTX-ray fluorescence using synchrotron radiation at glancing angles of incidence was used to measure interface widths for the highly immiscible polymer blend system polystyrene/polybromostyrene (PS/PBrxS, with bromination level x = 0.8 bromine atoms per monomer). The interfacial widths are for bilayers annealed for 4 hours and 24 hours at 141±1C are found to be 100± 20Å and 110±20Å respectively.
A Mew Variable Angle Ft—ir Ellipsometer
Authors: Stehle J.L. , Thomas O.T. , Piel J.P. , Evrard P. , Lecat J.H. , Hammond L.C. 
Published: March 2011

ABSTRACTUse of a Fourier—transform interferometer integrated with a variable incidence angle ellipsometer extends the spectral range and the capabilities of spectroscopic ellipsometry into the infrared. With a spectral range of 600 to 6600 cm—1, thick layers, such as epitaxial doped layers and polymers can be analysed.A full description of this novel instrument will be given. Incidence angle can be variedautomatically to enhance signal/noise and the ellipsometric data can be obtained together with vibrational absorption bands information to give a characteristic “fingerprint ” of the layers.Examples of spectra of HCN polymer on nickel, DMHS on aluminium and PMMA on silicon willbe presented for various incidence angles and layer thickness.
Determination of Particle Size of a Dispersed Phase by Small-Angle X-ray Scattering
Authors: Wilson Frank C. 
Published: March 2011

ABSTRACTA method for determining particle diameters up to ca 500 rnm is described. X-ray data are obtained with an ultra-high resolution Bonse-Hart diffractometer and subsequently desmeared. The resultant data, viewed as the invariant argument h l(h), are interpreted as arising from a log-normal distribution of independent spherical particles. The distribution is characterized by its median value and breadth.
Synthetic Polymers in Water-in-Oil Microemulsions
Authors: Candau Francoise 
Published: March 2011

ABSTRACTHigh molecular weight water-soluble polymers are usually supplied in the form of water-in-oil emulsions which have advantages of low viscosity and easy storage and dissolution. Most uses in water treatment, flocculation, paper manufacture or mining fields require polymer latexes formed of finely dipersed particles. Polymerization in reverse micelles or microemulsions appears to be an attractive technique because it can lead, under appropriate formulations, to high molecular weight polymers entrapped within small-sized stable particles. The main characteristics and properties of the latexes and polymers formed by this process are described.
Stabilized Nanoparticles Obtained from Synthetic Polykerizable Micelles and Vesicles.
Authors: Paleos Constantinos M. 
Published: March 2011

ABSTRACTThe structural characteristics and the formation of monomeric and stabilized polymeric micelles and vesicles are reviewed. Characterization of these nanoparticles involved stability studies, molecular weight determination, permeability and fluorescence investigations, as well as electron microscopy and DSC studies.
The Characterization of Infrared Transmitting Optical Fibers
Authors: Driver R. D. , Leskowitz G. M. , Curtiss L. E. , Moynihan D. E. , Vacha L. B. 
Published: March 2011

AbstractThe authors will review the methods used to characterize infrared transmitting optical fibers. The use of FTIR spectroscopic techniques for the measurement of fiber loss will be discussed. Fiber end preparation and fiber cleaving techniques will be reviewed. Data will be presented on silica fiber in the extended IR region, heavy metal fluoride, chalcogenide, silver halide fibers and sapphire crystalline fiber.
Preparation and Properties of Selenium-Tellurium Based Chalcogenide and Chalcohalide Glasses
Authors: Tuzzolo M. T. , Mcenroe D. J. , Drexhage M. G. 
Published: March 2011

AbstractChalcogenide and chalcohalide glasses were prepared and the resulting glass Tg's and spectra were investigated. Some chalcogenide glasses were prepared from thermally and chemically pretreated raw materials. Pretreatment steps produced a reduction in impurity absorptions caused by oxygen bonding to the constituent elements. Additions of small amounts of iodine improved attenuations by acting as a hydrogen getter material which eliminated H-Se absorptions. Due to low transition temperatures, chalcohalide glasses containing iodine may not meet commercial requirements.
31P Dipolar NMR Approaches Towards the Development of Structural Principles in Non-Oxidic Glasses.
Authors: Eckert Hellmut , Franke Deanna , Lathrop David , Maxwell Robert , Tullius Michael 
Published: March 2011

AbstractWhile the utility of solid state NMR to provide structural information in amorphous systems is well established in silicate and borate glasses, the systematic application of modern NMR techniques to non-oxidic systems has just begun. One of the central issues in these types of glasses is the question of the chemical bond distribution and the existence of short range order. The present study utilizes the selective measurement of homonuclear 31p.31P dipole-dipole couplings via spin echo decay to address this issue in the glass systems P-Se, PSe- Ge and CdGeAs2-xPx. The results indicate that the first two systems are characterized by a high degree of chemical ordering. The chemical bond distribution in CdGeAs2-xPx glasses is found to deviate considerably from that in the stoichiometry-analog crystalline materials.
Advance of Plastic Optical Fibers
Authors: Ide Fumio , Yamamoto Takashi 
Published: March 2011

AbstractPlastic optical fibers (so called POF) are already in wide use in a large number of fields. This paper gives an overview of the field including the advantages of plastic optical fibers, the various types of fibers and the materials in them.Then, the properties of three types of fibers which have recently been developed, are discussed. The first is fibers with a poly-methyl-methacrylate (PMMA) core, which have a low transmission loss. Another is heat resistant fibers for use in automobiles. And the third is the multi-fiber type for image guides. And finally, the applications of these fibers and their future prospect are discussed.
Analysis of Thermal Variation of Length and Refractive Index of Lead Fluoride to Study its Optical Properties
Authors: Aurora T. S. , Pederson D. O. , Day S. M. 
Published: March 2011

AbstractLinear thermal expansion and refractive index variation have been measured in lead fluoride with a laser interferometer as a function of temperature. Data has been analyzed using the Lorentz-Lorenz relation. Molecular polarizability, band gap, variation of refractive index with density, and strain-polarizability parameter have been studied as a function of temperature. They exhibit a small variation with temperature except near the superionic phase transition where the variation appears to be more pronounced. The results are in good agreement with the published data near room temperature.
Concentration and Distribution of ER, AL and P in Silica-Based Optical Fiber Preforms by Sims
Authors: Oblas D. W. , Wei T. , Miniscalco W. J. , Hall B. T. 
Published: March 2011

AbstractSecondary ion mass spectrometry (SIMS) was used to measure the Er, Al and P distributions across (perpendicular to) and along (parallel to) the axis of Er3+-doped silica based preforms and fibers prepared by a solution doping technique. Specially prepared low-melting silicate glass standards containing known concentrations of Er were used to calibrate the spectrometer to obtain a semi-quantitative measurement of the Er concentration. It was found that the Er concentration can vary along a 4-cm section of the preform by as much as a factor of two. The Al concentration also changed along the length of the preform, but to a smaller degree. Finally, instrumental limitations for measuring the Er, Al and P distributions in the optical fiber samples were determined.
Excited State Absorption and Cross Sections for Er-Doped Glasses
Authors: Zemon S. , Lambert G. , Miniscalco W. J. , Andrews L. J. , Hall B. T. 
Published: March 2011

AbstractPump-excited-state-absorption (ESA) measurements on Er3+-doped phosphates, fluorophosphates, and silicate bulk glasses indicate that ESA cross sections are approximately equal to ground state absorption (GSA) cross sections in the 800-nm band. The oscillator strengths of the ESA and GSA bands are also approximately equal, in qualitative agreement with Judd-Ofelt calculations. Fluorozirconate samples were found to have substantial populations in the upper excited states for the measurement conditions used and ESA transitions originating from four excited states were identified. Fluorozirconate fiber amplifiers and lasers at 1.55 μm, therefore, would have decreased efficiency for 800-nm pumping.