bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation Of K3LI2NB5O15 (KLN) Thin Films by Rf-Magnetron Sputter Process
Authors: Kim Gwang-Tae , Park Myung-Sik , Lee Joon-Hyung , Cho Sang-Hee 
Published: April 2011

AbstractIn this study, the KLN thin films were prepared by RF-magnetron sputtering method onto Coming 1737 glass. The effect of working pressure, substrate temperature, RF-power, sputter gas ratio (Ar/O2) during deposition was investigated. For an optimum deposition condition, the postannealing, RTA(rapid thermal annealing) and IPA(in-situ post annealing)methods were employed. Both RTA and IPA processes, which were conducted at different deposition and annealing temperature influenced surface morphology and optical properties of the films. The films prepared by the IPA process showed a lower crystallization temperature and better optical transmittance.
Progress in Fully Functionalized Photorefractive Materials
Authors: Wang Qing , Wang Liming , Ng Man Kit , Yu Luping 
Published: April 2011

AbstractPhotorefractive (PR) materials are multifunctional materials which combine both photoconductivity and electro-optic response to show a new phenomenon: reversible modulation of the index of refraction by light. In the past years, our group has focused on the development of fully functionalized polymers, oligomers and small molecular materials. We have had success in identifying new materials and in gaining understanding in design principles of better materials. Several new PR material systems have been explored, including conjugated PR polymers containing transition metal complexes as photosensitizers, oligothiophene based PR systems and small molecular PR materials containing carbazole and methine dyes. Large net optical gain and minimized phase separation were achieved. The correlation between molecular structure and physical properties is the focal point of this paper.
A Study Towards the Design of Materials for Nonlinear Optical Applications Using First Principle Calculations
Authors: Nguyen Kiet A. , Day Paul N. , Pachter Ruth 
Published: April 2011

AbstractElectronic structure calculations are carried out to predict properties of reverse saturable absorption (RSA) materials that are important in nonlinear optical (NLO) applications. The RSA dyes under investigation are zinc porphyrins with a combination of halogen and phenyl substituents. The computed data include electronic spectra for the ground and triplet excited states as well as ionization potentials. These properties are important in predicting the performance of NLO materials. Since comprehensive data are not available, we begin with the basic porphyrin unit, then systematically replace the peripheral hydrogens of porphin with halogen and phenyl groups to study the substituent effects. The results of halogenated porphyrins and halogenated tetraphenylporphyrins provide insightful accounts of effects of phenyl, fluoro, chloro, and bromo substituents on the spectra of these systems. The computed spectra and IPs are in excellent agreement with available experimental data.
Wavelength Dispersion of Optical Power Limiting in Stilbene3 Analyzed within a Three Level Model
Authors: Chollet P-A. , Somin A. , Paci B. , Hully V. , Nunzi J-M. , Morel Y. , Baldeck P. 
Published: April 2011

AbstractNonlinear transmission in a dye (stilbene3) exhibiting two-photon absorption (TPA) has been studied has a function of wavelength, in the visible range using nanosecond laser pulses. The results have been analyzed within a three level model: the first excited one is populated by TPA and is excited toward an upper level (excited state absorption, ESA). The TPA and ESA spectra obtained by optical limiting (δ∼10-46 cm4s photon-1molecule-1; δ∼ 10-16 cm2) are in good agreement with those determined by two-photon fluorescence and Kerr ellipsometry. Thus, nonlinear transmission appears as a useful technique to estimate the TPA and ESA contributions in optical limiting.
Porphyrin Dye Media for Optical Limiting
Authors: McEwan K. J. , Robertson J. M. , Anderson H. L. 
Published: April 2011

AbstractIn this report we study nine structurally similar porphyrins and show how the material parameters that control the optical limiting depend on the molecular structure. Optical limiting measurements at 532 nm on the metal-free, zinc and lead analogues of tetraphenyl porphyrin (TPP), tetra(trimethylsilyethynyl) porphyrin (TTMSAP) and tetra(4-n-butylphenylethynyl) porphyrin (TNBBAP) reveal a strong dependence on the molecular structure. A double pump/cw probe technique is used to measure the material parameters that control the optical limiting and the results give a strong insight into how the molecular structure influences the individual parameters. These measurements revealed that one of the materials TTMSAP(Pb) has a σex/σgrratio of ∼45 at 532 rim, which is one of the largest values ever reported. Finally, broadband measurements with a picosecond white-light source show that the excited state absorption profile for the porphyrins examined is much broader than the ground state features and is centred to the long wavelength side of the ground state Soret band.
Biomimetic Preparation of ha Precursors at 37°C in Urea- and Enzyme Urease-Containing Synthetic Body Fluids
Authors: Bayraktar D , Tas A C. 
Published: April 2011

AbstractAn important inorganic phase of synthetic bone applications, calcium hydroxyapatite (HA, Ca10(PO4)6(OH)2), was prepared as a single-phase and sub-micron bioceramic powder. Carbonated HA precursors were synthesized from calcium nitrate tetrahydrate and diammonium hydrogen phosphate salts dissolved in “synthetic body fluid” (SBF) solutions, containing urea (H2NCONH2) and enzyme urease, under the biomimetic conditions of 37°C andpH 7.4, by using a novel chemical precipitation technique.
Borrowing Ideas from Nature: Peptide Specific Binding to Gallium Arsenide
Authors: Whaley Sandra R. , Belcher Angela M. 
Published: April 2011

AbstractBiological systems have a unique ability to control crystal structure, phase, orientation and nanostructural regularity of inorganic materials. An example is seen with the control of crystallographic phase and orientation of calcium carbonate with the polyanionic proteins isolated from shells of the marine gastropod abalone. We are currently investigating the principles of natural biological molecular recognition in materials and developing new methods to pattern useful non-biological electronic and magnetic materials on new length scales. A peptide combinatorial approach has been employed to identify proteins that select for and specifically bind to inorganic structures such as semiconductor wafers, nanoparticles and quantum confined structures. This approach utilizes the inherent self-organizing, highly selective properties of biologically derived molecules. We are currently investigating peptide recognition and interaction with III-V and II-VI semiconductor materials, magnetic materials, calcium carbonates and phosphates. We have selected peptides that can specifically bind and discriminate between zinc-blende III-V semiconductor surfaces. These peptides show crystal face specificity and are being used to organize nanoparticle heterostructures. Long term potential application of these materials would include opto-electronic devices such as light emitting displays, optical detectors, lasers, and nanometer scale computer components.
Proteins From Oyster Shell: Biomineralization Regulators and Commercial Polymer Analogs
Authors: Wheeler A. P. , Sikes C. S. 
Published: April 2011

AbstractMolluscan shell is a composite made up of μm-sized CaCO3 crystals and an organic phase (matrix). This report outlines our studies on the structure and activities of matrix proteins isolated from the inner calcite layer of shell of the Eastern oyster, including their cellular origin and structure and their relationship to the crystalline mineral phase. In addition, we present results of the synthesis and commercialization of polypeptide polymers which are based on the structure and activities of the oyster proteins. Extracted shell proteins are polyanionic and range in size from relatively small soluble forms to those which are crosslinked and insoluble. The soluble forms are capable of adsorbing to calcite in vitro and in the process changing its growth habit and acting as threshold growth inhibitors. Their function in vivo is not understood, but they may serve to control shell crystal morphology. The insoluble protein forms gels readily and may serve to provide resiliency to the shell and, from in vitro and in situ observations, appears to serve as a site for nucleation of crystals. However, from studies in vitro, these gels do not lower the energy of activation for nucleation, as previously expected. Matrix protein aggregates are identifiable by AFM on the surface of crystals, but as such do not serve as nucleation sites for new crystal growth. If the aggregates are removed, then ectopic crystal growth proceeds readily revealing orientation of the underlying crystals. All the matrix proteins contain domains rich in aspartic acid, are heavily phosphorylated, crossreact in antibody studies and may belong to a limited number of gene families with individuals modified post-synthesis. The proteins are made by a specialized group of cells located primarily some distance from the growing edge of the shell and appear to be assembled into sheets soon after secretion. Soluble anti-scalants and crosslinked insoluble water absorbents have been developed based on the structure and activity of the matrix proteins. These are primarily poly(aspartates) which can be made in large scale via thermal polycondensation of aspartic acid. The soluble forms are commercially used as biodegradable water treatment chemicals among other applications.
Learning From Biological Systems: Novel Routes to Biomimetic Synthesis of Ordered Silica Structures
Authors: Chal Jennifer N. , Shimizu Katsuhiko , Zhou Yan , Christiansen Sean C. , Chmelka Bradley F. , Deming Timothy J. , Stucky Galen D. , Morse Daniel E. 
Published: April 2011

AbstractBiological systems have evolved mechanisms that precisely control inorganic structures on both the micro- and nanoscale, operating at ambient pressures and temperatures. In both the calcium carbonate, calcium phosphate and silicon dioxide utilizing organisms, proteins and polysaccharides have been found to play integral roles in the organization of these biominerals[1–3]. The organic constituents generally have been thought to act as direct templates or modulators for the deposition of the particular mineral. We have explored the synthesis and structural control of silica by the marine sponge, Tethya aurantia. Needles of amorphous silica comprise the skeletal system of this organism, representing 75% of the dry weight of the organism. These glassy needles, called spicules, are 2 mm in length and 30 μn in width[4,5]. We have characterized the structure, genetics and functions of the proteins that form an occluded axial filament within each silica spicule. Based on our discovery, a unique structure-directing catalytic mechanism exhibited by these protein filaments, and the structural determinants responsible for the catalytic activity, we have designed novel block copolypeptides that catalyze and spatially direct he condensation of silicon alkoxides to form organized silica structures ranging from transparent spheres to lath-like structures at ambient pressure, low temperature and neutral pH.
Removal Pathway of Bioactive Glass Resorption Products from the Body
Authors: Lai W. , Ducheyne P. , Garino J. , Flaitz C. M. 
Published: April 2011

AbstractWe traced and quantified the silicon released from bioactive glass (BG) granules in vivo (45S5, 300–355 μm). 1500 mg of BG granules were implanted in the paraspinal muscle of 7 four kg rabbits. Blood samples and 24-hour urine samples were obtained over a 24 week period. Local muscle tissue as well as the following organs were harvested for chemical and histological analyses: brain, heart, kidney, liver, lung, lymph nodes, spleen, and thymus. Flame atomic absorption spectrophotometry was used to measure the concentration of elemental silicon in all the samples after digestion. Tissues and fluids from a sham group of 7 rabbits (underwent surgical procedure but received no implants) were obtained in a similar manner.The urinary silicon of the implanted group was significantly higher than in the control group. From the data, the calculated average excretion rate was approximately 2.4 mg/day, and as such, 100 percent of the implanted silicon was excreted in 19 weeks. No elevated concentrations of silicon were found at the implant site or in the other organs after 24 weeks. Histological appearance of all major organs was normal for all animals in the study.The concentrations of silicon measured in the urine were well below saturation and since no significant increase in silicon was found in the kidney or in the other organs, the increased silicon excretion rate was within the physiological capacity of rabbits. Therefore, it can be concluded that the resorbed silica gel is harmlessly excreted in soluble form through the urine.
Investigation of the Transport Mechanism in Doped La-Based Manganite Thin Films by Traveling Wave Method
Authors: Wang L. , Huang S. , Yin J. , Huang X. , Xu J. , Liu Z. , Chen K. 
Published: April 2011

AbstractThe traveling wave (TW) method has been utilized to investigate the transport mechanism in paramagnetic-insulator state of La0.75Sr0.11Ca0.14MnO3 films. The drift mobility of the films increased from 2.5 × 10−2 cm2/Vs at 310 K to about 9.2 × 10−2 cm2/Vs at 400 K. The Arrhenius behaviors of the conductivity and drift mobility indicate that the transport process in manganites above the Curie temperature is dominated by the thermally assisted hopping of small polarons.
Properties of the Ferrimagnetic Double-Perovskites A2FeReO6 (A=Ba and Ca)
Authors: Prellier W. , Smolyaninova V. , Biswas A. , Galley C. , Greene R.L. , Ramesha K. , Gopalakrishnan J. 
Published: April 2011

AbstractWe have synthesized ceramics of A2FeReO6 double-perovskites A2FeReO6 (A=Ba, Ca). Structural characterizations indicate a cubic structure with a=8.0854(1) Å for Ba2FeReO6 and a distorted monoclinic symmetry with a=5.396(1) Å, b=5.522(1) Å, c=7.688(2) Å and β=90.4° for Ca2FeReO6. The barium compound is metallic from 5K to 385K, i.e. no metal-insulator transition has been seen up to 385K, and the calcium compound is semiconducting from 5K to 385K. Magnetization measurements show a ferrimagnetic behavior for both materials, with Tc =315 K for Ba2FeReO6 and above 385K for Ca2FeReO6. At 5K we observed, only for Ba2FeReO6, a negative magnetoresistance of 10% in a magnetic field of 5T. Electrical, magnetic and thermal properties are discussed and compared to those of the analogous compounds Sr2Fe(Mo,Re)O6 recently studied.
The Effects of Substrate-Induced Strains on the Charge-Ordering Transition in Nd0.5Sr0.5MnO3 Thin Films
Authors: Prellier W. , Biswas Amlan , Rajeswari M. , Venkatesan T. , Greene R.L. 
Published: April 2011

AbstractWe report the growth and characterization of Nd0.5Sr0.5MnO3 thin films deposited by the Pulsed Laser Deposition (PLD) technique on [100]-oriented LaAlO3 substrates. X-ray diffraction (XRD) studies show that the films are [101]-oriented, with a strained and quasi-relaxed component, the latter increasing with film thickness. A post-annealing under oxygen leads to a quasi-relaxed film with a metallic behavior. We also observe that transport properties are strongly dependent on the thickness of the films. Variable temperature XRD down to 100 K suggests that this is caused by substrate-induced strain on the films.
A-Site Ordered, Perovskite-Like Manganites Grown by PLD or Laser-MBE: Their Growth, Structural and Physical Characterization
Authors: Mercey B. , Haghiri-Gosnet A.M. , Lecoeur Ph. , Chippaux D. , Raveau B. , Salvador P.A. 
Published: April 2011

AbstractUsing both a “classical” pulsed laser deposition process and a laser-MBE process, superlattices in the Pr0.5Sr0.5MnO3 system were grown from PrMnO3 and SrMnO3 targets. A-site ordering of perovskite-like manganite was achieved using both deposition processes. However the electric and magnetic properties of the superlattices are shown to be strongly dependent on the growth process.
The Oxygen Mobility and Catalytic Activity of LaMO3±δ(M=Cr, Mn, Co) Phases
Authors: Koudriashov I.A. , Borovskikh L.V. , Mazo G.N. , Scheurell S. , Kemnitz E. 
Published: April 2011

AbstractThe activity of LaMO3, where M=Cr, Mn, Co, perovskite-type complex oxides in oxygen diffusion and catalytic processes was investigated. For sample preparation freeze-drying technique was used and dynamic thermal isotope exchange method was used to study exchange reaction between18O from the gas phase and16O from the samples synthesized, and to investigate the methane catalytic oxidation reaction. The results obtained allowed to indicate temperature intervals of different types of reaction taking place and that LaCrO3is far less active in mentioned reactions than LaCoO3and LaMnO3.
Growth and Magnetic Properties of La0.65Pb0.35MnO3 Films
Authors: Xu Q. L. , Liu M. T. , Liu Y. , Borca C. N. , Dulli H. , Dowben P. A. , Liou S. H. 
Published: April 2011

AbstractWe have successfully grown La0.65PbO.35MnO3 thin films by a RF magnetron sputtering method onto (100) LaAlO3 single crystal substrates. X-ray diffraction measurements are consistent with a (100) cubic orientation of the films. The fourfold symmetry showed by LEED(Low Energy Electron Diffraction) patterns indicate that the films have surface order. STM(Scanning Tunneling Microscopy) measurements indicate that the surface of the films were smooth, with approximate 5 nm roughness. XPS (X-ray Photoemission Spectroscopy) shows that the surface defect density in the films is comparatively low. The bulk magnetization of the films at 6K in 1 T magnetic field reached 77 emu/g and a Curie temperature near 354 K, close to maximum resistivity. A negative magnetoresistance of 47% was observed at 320K in 5.5 T magnetic field.
Magnetically Tuned Superconducting Filters
Authors: Oates D. E. , Anderson A. C. , Dionne G. F. 
Published: April 2011

AbstractWe have demonstrated magnetically tunable superconducting filters consisting of microwave circuits coupled to ferrite substrates in monolithic structures using both niobium at 4 K and YBCO at 77 K. A three-pole 1% bandwidth filter with 10-GHz center frequency, 1-dB insertion loss, and greater than 10% tunability has been demonstrated. Operation of the ferrite in the partially magnetized state prevents degradation of the surface resistance of the superconductor. This technology has the potential for compact, light weight, multipole filters with very low insertion loss, <0.5 dB, and very rapid tunability, <1 µs, due to the low inductance of the magnetic circuits. We also discuss the use of lightly coupled ferroelectric films to introduce trimming of the individual resonators in the magnetically tuned filters. The materials issues that limit performance and means to improve present performance are discussed.
Frequency Agile Microwave Applications Using (Ba,Sr)TiO3/Y3Fe5O12 Multilayer Grown by Pulsed Laser Deposition
Authors: Kim W.J. , Chang W. , Qadri S.B. , Wu H.D. , Pond J.M. , Kirchoefer S.W. , Newman H.S. , Chrisey D.B. , Horwitz J.S. 
Published: April 2011

Abstract(Ba,Sr)TiO3 (BST) thin films have been deposited by pulsed laser deposition (PLD) onto single crystal Y3Fe5O12 (YIG) substrates with/without an MgO buffer layer. The structure and microwave properties of BST films have been investigated as function of substrate orientation and O2 deposition pressures (5-800m Torr). The orientation of BST film is varies with the deposition conditions. The dielectric constant, loss tangent, and change in dielectric constant with an applied electric field have been measured at room temperature using interdigitated capacitors at 0.1 – 20 GHz. Polycrystalline BST films have a high tunability (∼40%) with a dc bias field of 67kV/cm and a dielectric Q (=l/tanδ) between 30 and 40, while (001) oriented BST films have a lower tunability (∼20%) but higher dielectric Q (∼50). A coplanar waveguide transmission line was fabricated from a (001) oriented BST film on (111)YIG which exhibited a 17° differential phase shift with an applied dc bias of 21 kV/cm. An equivalent differential phase shift was achieved with a magnetic field of 160Guass.
Effect of the Oxygen Partial Pressure on the Microstructure and Properties of Barium Strontium Titanate Thin Films Synthesized by Pulsed Laser Deposition
Authors: Fountzoulas C.G. , Hubbard C. W. , Ngo Eric H. , Kleinmeyer J. D. , Demaree J. D. , Joshi P. C. , Cole M. W. 
Published: April 2011

AbstractBarium strontium titanate (BSTO) films were synthesized by the pulsed laser deposition technique (PLD) on silicon substrates at room temperature. The BSTO film synthesis took place at constant laser energy, 500 mJ, and partial oxygen pressure of 3, 15, 30, 45, 100 mTorr. All films were post annealed at 750 °C in a tube furnace in an oxygen atmosphere. The microstructure, crystallinity and lattice constant of the BSTO films were studied with the aid of scanning electron microscopy (SEM), photon tunneling microscopy (PTM) and Glancing Angle X-ray Diffraction analysis (GAXRD). The hardness and modulus of elasticity of the films were studied with the aid of a nanohardness indenter. The film stoichiometry was determined with the aid of Rutherford Back Scattering (RBS). The results of this research will be combined with the results of our previous work [1] on the effect of substrate temperature on the microstructure and mechanical properties of the BSTO films in order to construct a structural zone model (SZM) of the BSTO films synthesized by PLD.
Nanocrystalline Thin Films for Tunable High Q UHF/VHF Devices
Authors: Win Winston N. , Park Jin-Young , Walser Rodger M. 
Published: April 2011

AbstractRecent studies indicate that reactively sputtered FeCrTaN nanocrystalline thin films have many of the properties [large magnetization (4πMs), anisotropy (Han), and resistivity (ρ)] required for application in high Q (>1000), magnetically tunable devices operating in the VHF/UHF (∼50 MHz to 500 MHz) frequency range. These films had thickness (d) of ∼0.1 -µm, but film thickness of ∼1-µm may be required for many devices. Although most previous research has shown that the magnetic properties of sputtered films are significantly deteriorated when d∼1-µm, there are recent reports that those of reactively sputtered nanocrystalline films of similar alloys (FeTaN, CoAl/SiO) are independent of thickness to d≈1-2-µm. Accordingly, this work investigated the possibility of reactively sputtering FeCrTa alloys in O/N gas mixtures to obtain films with device quality properties, that are independent of thickness to 1-2µm. The correlations between their magnetic and electrical properties, and their nano-heterogeneous microstructure, were studied to determine optimum reactive gas mixtures and sputtering parameters. Cross-section TEM studies were conducted to investigate the origins of the thickness independent properties, and the unexpected increases in anisotropy.