bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spin-Dependent Transport in Manganite Trilayer Junctions
Authors: Sun Jonathan Z. 
Published: April 2011

AbstractDoped manganite trilayer junction provides a model system for the study of spin-dependent transport across an artificial interface between manganites. Large interface magnetoresistance is observed in manganite trilayer junctions. Further studies reveal a strongly temperature and junction-bias dependent magnetoresistance, as well as a large interaction between the spin-polarized current and the ferromagnetic moment. The physical and materials origin of these and other junction properties are discussed in this brief review.
Epitaxial Growth of Yb2O3 Buffer Layers on Biaxially Textured-Ni (100) Substrates by Sol-Gel Process
Authors: Chirayil T. G. , Paranthaman M. , Beach D. B. , Morrelli J. S. , Sun E. Y. , Goyal A. , Williams R. K. , Lee D. F. , Martin P. M. , Kroeger D. M. , Feenstra R. , Verebelyi D. T. , Christen D. K. 
Published: April 2011

AbstractIn order to develop an alternative buffer layer architecture using the sol-gel process to produce YBCO (YBa2Cu3O7-δ) coated conductors, Yb2O3 has been chosen as the candidate material. Buffer layers of Yb2O3 were epitaxially grown on biaxially textured-Ni (100) substrates by the sol gel process for the first time. The Yb2O3 precursor solution was prepared from an alkoxide sol-gel route in 2-methoxyethanol and was deposited on textured-Ni (100) substrates by either spin coating or dip coating methods. The amorphous film was then processed at 1160°C under flowing (96%)Ar/H2(4%) gas mixture for one hour. The Yb2O3 film exhibited a strong c-axis orientation on the Ni (100) substrates. The phi and omega scans indicated good in plane and out of plane orientations. The X-ray (222) pole figure showed a cube-on-cube epitaxy. High current YBCO films were grown on the Yb2O3 sol-gel buffered-Ni substrates.
Enhancement in Electrical Properties of (Ba,Sr)TiO3 Films Using Tailored Oxide Electrodes
Authors: Choi Duck-Kyun , Park Kyung-Woong , Park Jeong-Hee , Oh Se-Hoon , Kim Boum-Seock , Lee Jae-Bok 
Published: April 2011

AbstractSelection of a proper electrode for high dielectric material such as (Ba, Sr)TiO3 is a great concern because the deposition of BST requires a high temperature and an oxidizing atmosphere. In this study, we suggested the perovskite-type electrodes, which provide a structural match with the BST dielectric material, under the recognition that the high leakage current is associated with the structural mismatch between BST and the electrode. We studied the (Ca,Sr)RuO3 electrode of which the lattice parameter can be tuned to fit into BST by changing the Ca/Sr ratio. We also studied (Ba,Sr)RuO3 electrode which is not only structurally identical but also chemically similar to BST. In addition, the effect of doping in the BSR electrode was investigated to minimize the leakage current by proper modulation of the barrier height. The electrodes were directly deposited on an Si substrate and all the films in the experiments were deposited by RF magnetron sputtering technique. Electrical properties were measured from MIM structure. The main focus was to address the effect of Ca/Sr and Ba/Sr ratio variations in the electrodes on the resulting dielectric constant and the leakage current. The interface characteristics between the BST film and the electrode were examined in order to interpret the electrical properties of BST films.
First-Principles Calculations of Nonlinear Optical Response Functions in Semiconductors
Authors: Rashkeev Sergey N. , Lambrecht Walter R. L. 
Published: April 2011

ABSTRACTWe present our implementation of the length-gauge formalism of Sipe and coworkers (Phys. Rev. B 48, 11705 (1993); ibid 52, 14636 (1995)) using the linearized muffin-tin orbital (LMTO) method and discuss its application to the calculation of second order response functions. The importance of gap corrections beyond LDA is discussed. As primary application, we discuss the second harmonic generation (SHG) coefficients of the SiC polytypes and of the chalcopyrites of both the II-IV-V2 and I-III-VI2 families. These examples illustrate the relation of the second order response function to the modification of the crystal structure and chemical substitutions.
The First Principles Study on Light Emitting Properties of Semiconducting Metal Silicides
Authors: Yamaguchi Kenji , Mizushima Kazuki , Sassa Koichi 
Published: April 2011

ABSTRACTSemiconducting metal silicides are potential candidates of silicon-based light emitting materials. In order to carry out screening of the candidates, we calculated the oscillator strength between the valence and excited states near the band gap for various silicides. The electronic states were obtained by the full-potential linear augmented-plane-wave method (FLAPW) based on the local density approximation (LDA). The results show Ru2Si3 and Ca2Si have direct gap at τ point, but the values of the oscillator strength across the gap are evaluated to be zero. Among the indirect gap semiconductors, β-FeSi2, OsSi, and OsSi2 have several peaks and valleys facing each other near the band gap. Among the combinations, we obtained the biggest value of oscillator strength 0.3 at X point for OsSi with the transition energy of 0.42 eV.
Simulation Of Diffuse Light Exposure Of Low Temperature Co-Fired Ceramic Tapes And The Problem Of Sidewall Morphology
Authors: Espinoza-Vallejos P. , Santiago-Aviles J. , Sola-Laguna L. 
Published: April 2011

ABSTRACTWe have simulated the scattering of UV light in a photo-formable ceramic tape and experimentally measured the transport mean free path (random walk step) between scattering events. After processing the tape we have achieved features size of 70 μm in a 150 μm-thick tape. We were able to predict and control the undercut due to scattering of the light by alumina grains. The experimental verification of the model utilizes a modified version of diffuse-Transmission Spectroscopy (DTS) using the material development characteristics as a sensor. The technique involves the measurement of absorption coefficient by measuring the sample thickness as a function of energy. We also simulated the effect of changing the number density of scatter centers in side-wall morphology.
In Situ Morphological Study of The Al/SiO2 Reaction Around The eutectic Point
Authors: Allam Lévy , Fleury Vincent 
Published: April 2011

AbstractIn the context of the electronic industry, thin films of aluminum are deposited on silica. However, the Al/SiO2 interface is unstable. A reaction leading to oxidation of Al and reduction of SiO2 occurs. We present an in situ study of this reaction, in thin films, at temperatures above 500°C. This experiment allows to understand the essential steps of the oxidation of Al by SiO2, and it shows that thermal cycles can be used to generate nucleation centers artificially. More generally, the morphological interpretation of out-of-equilibrium growth patterns gives important insight into the coupling between the thermodynamics and morphological aspects of a thin film chemical reaction.
A DICTRA Simulation of θ – phase Dissolution in Al-Cu Alloys
Authors: Thompson Raymond G. , Malam Curt 
Published: April 2011

AbstractThis paper presents a comparison between the computer simulation dissolution model, DICTRA, and an experimental data set from the literature, Baty, Tanzilli and Heckel, 1970. This was undertaken to support research on the modeling of the weld heat-affected zone where grain growth and Zener pinning control materials properties. BTH present quantitative-microscopy data on the dissolution of 5 size classes in their 4.2μ particle sample and 4 size classes in their 0.44μ sample. The DICTRA example of the 3-cell calculation of cementite particles in steel was used as the model to simulate the BTH experiment.
In Situ STM Observation of the Spiral Growth in the Epitaxial Fe Films on MgO(001)
Authors: Subagyo Agus , Sueoka Kazuhisa , Mukasa Koichi 
Published: April 2011

AbstractWe reported a scanning tunneling microscopy(STM) observation on the growth mode transition from 2D-nucleation to spiral growth in the epitaxial Fe films on MgO(001). As the growth temperature is increased to above 493 K, a temperature region where the Schwoebel barrier is overcome, the Fe films grow in a 2D-nucleation and growth mode formed atomically flat films. The 2D-nucleation transformed into a spiral growth as increasing film thickness. At a growth temperature of 493 K, the transition of 2D nucleation to the spiral growth was observed at a film thickness of 75 Å. The critical thickness of the emergence of growth transition decreased as the growth temperature is increased.
The Effect of Low-Energy Nitrogen Ions on the Growth Modes of Nitrides on Polymers used in the Microelectronics Industry
Authors: Abramowitz P. , Kiene M. , Ho P. 
Published: April 2011

AbstractUltra-thin titanium and tantalum nitride layers grown on three different dielectrics were studied to examine how low-energy ions change the chemical composition at and near their interface. Comparisons were made by growing titanium and tantalum nitride under similar conditions both with (ion-assisted) and without (reactive) nitrogen ions. Although the chemical reactions between the nitrides and the three dielectrics under both growth conditions depend on the type of dielectric used, a few general observations were seen. In comparison with the reactively grown samples, all of the ion-assisted growths show a significant increase in the amount of nitride in the nitride layer at and near the nitride/dielectric interface. Moreover, the amount of chemical binding between the titanium nitride and dielectric is increased when low-energy ions are used. Angle resolved x-ray photoemission determined that the enhancement in the deposition process from low-energy ions occurs without inducing significant intermixing between the nitride layer and dielectric. Although thicker layers of titanium nitride show a difference in the grain structure from ion deposition1, the ultra-thin layers grown in this work do not have any dependence with ion-assisted growth for the samples measured.
Incoherent High-Resolution Z-Contrast Imaging of Silicon and Gallium Arsenide Using HAADF-STEM
Authors: Kotaka Y , Yamazaki T. , Kikuchi Y , Watanabe K. 
Published: April 2011

AbstractThe high-angle annular dark-field (HAADF) technique in a dedicated scanning transmission electron microscope (STEM) provides strong compositional sensitivity dependent on atomic number (Z-contrast image). Furthermore, a high spatial resolution image is comparable to that of conventional coherent imaging (HRTEM). However, it is difficult to obtain a clear atomic structure HAADF image using a hybrid TEM/STEM. In this work, HAADF images were obtained with a JEOL JEM-2010F (with a thermal-Schottky field-emission) gun in probe-forming mode at 200 kV. We performed experiments using Si and GaAs in the [110] orientation. The electron-optical conditions were optimized. As a result, the dumbbell structure was observed in an image of [110] Si. Intensity profiles for GaAs along [001] showed differences for the two atomic sites. The experimental images were analyzed and compared with the calculated atomic positions and intensities obtained from Bethe's eigen-value method, which was modified to simulate HAADF-STEM based on Allen and Rossouw's method for convergent-beam electron diffraction (CBED). The experimental results showed a good agreement with the simulation results.
Cutting Single Wall Carbon Nanotubes
Authors: Stepanek I. , Maurin G. , Bernier P , Gavillet J. , Loiseau A. 
Published: April 2011

ABSTRACTIn this contribution, we report on a mechanical method to cut and open single walled carbon nanotubes. This technique is based on using an abrasive material (diamond powder) without any chemical treatments or oxidation in air at high temperature. We present highresolution transmission electron microscopy micrographs, which show firstly that the tubes are unambiguously opened and secondly, that the nanotubes have not suffered the treatment. x-ray diffraction pattern confirms a well-defined bundle organisation. A breaking mechanism of the nanotube bundles is proposed. Nitrogen adsorption measurements at 77K reveal the presence of new microporosities ranging in the average nanotube diameter, which confirm the opening of some tubes.
Plasma Diagnostics During Pulsed Laser Deposition of Diamond-Like Carbon Using Single Crystal Graphite and Amorphous Carbon
Authors: Yamagata Y , Sharma A. , Narayan J. , Mayo R. M. , Newman J. W. , Ebihara K. 
Published: April 2011

ABSTRACTOptical emission study of ablation plasma plumes from single crystal graphite (SCG) and amorphous carbon (a-C) targets during the preparation of diamond-like carbon (DLC) films by KrF excimer pulsed laser deposition (PLD) has been investigated. The C I emission intensity increases with laser energy density (EL) increase, while the C2 emission changes drastically with EL for both ablated plasma plumes. The C2/C emission intensity ratio for the a-C plume decreases with EL increase, while the C2/C ratio for the SCG plume decreases with EL increase up to 3.0 J/cm2, then increases slightly with further EL increase Nanohardness of the DLC films decreases with the C2/C ratio increase. It is suggested that the C2 molecule in the plasma plume does not play an important role in producing high quality DLC films, and that the C2/C ratio is a good parameter to monitor the PLD process.
Dielectric Properties of Amorphous Carbon Nitride Films
Authors: Aono M. , Katsuno T. , Nitta S. , Itoh T. , Nonomura S. 
Published: April 2011

ABSTRACTDielectric properties of amorphous carbon nitride films made by the layer-by-layer method, (LLa-CNx) consisting of a cyclic process with (A) the deposition of an amorphous carbon nitride layer by sputtering and with (B) the etching by atomic hydrogen, have been compared with that of amorphous carbon nitride (a-CNx) films prepared without the hydrogen etching process. It is found that the nitrogen in a-CNx and LLa-CNx could decrease the refractive index n and the dielectric constant ε at 1 MHz. The nitrogen could create less dense structure in a-CNx and LLa-CNx compared to diamond-like carbon (DLC). The sp3 bonds between carbon atoms seem to increase by the atomic hydrogen treatment in LLa-CNx. The refractive index of LLa-CNx increases with sp3content. Preliminary experiments adding oxygen in amorphous carbon nitride to create a-CNxOy film are tried and discussed briefly.
Hyperbranched Conductive Polymers Constituted of Triphenylamine
Authors: Tanaka S. , Takeuchi K. , Asai M. , Iso T. , Ueda M. 
Published: April 2011

AbstractA hyperbranched conjugated polymer containing triphenylamine was prepared by the Grignard reaction of tris(4-bromophenyl)amine 1, via the coupling of N, N-bis(4-bromophenyl)-N-(4-bromomagnesiophenyl)amine 2 with the catalytic amount of Ni(acac)2. Grignard reagent 2 reacted as an AB2-type monomer to give hyperbranched conjugated polymer 3 in a one-step process. Polymer 3 was also obtained via the Pd-catalyzed coupling of N, N-bis(4-bromophenyl)-4-animobenzeneboronic acid 4. Polymer 3 had an average molecular weight of 4.0–6.3×103 and was found to be soluble in organic solvents such as THF and CHC13. A cast film had an anodic peak at 0.95–1.20 V vs. Ag wire. It was dark blue above the oxidation potential and brown-yellow in the neutral state. When polymer 3 was doped with iodine, its conductivity rose to 0.8–3.0 S/cm
The Constitutive Response of Active Polymer Gels
Authors: Marra S. P. , Ramesh K. T. , Douglas A. S. 
Published: April 2011

AbstractActive polymer gels can achieve large, reversible deformations in response to environmental stimuli, such as the application of an electric field or a change in pH level. Consequently, great interest exists in using these gels as actuators and artificial muscles. The goal of this work is to characterize the mechanical properties of ionic polymer gels and to describe how these properties evolve as the gel actuates. Experimental results of uniaxial tests on poly(vinyl alcohol)-poly(acrylic acid) gels are presented for both acidic and basic environments. These materials are shown to be to be slightly viscoelastic and compressible and capable of large recoverable deformations. The gels also exhibit similar stress in response to mechanical deformation in both the acid and the base.
Structural Change in Ferroelectric Phase Transition of Vinylidene Fluoride Copolymers as Studied by Waxs, Saxs, IR, Raman, and Computer Simulation Techniques
Authors: Tashiro K. 
Published: April 2011

AbstractStructure changes in the ferroelectric phase transitions of vinylidene fluoride-trifluoroethylene (VDF-TrFE) copolymers were investigated on the basis of a set of experimental data of WAXS, SAXS, IR and Raman measurements. An intimate relation has been clarified between the structural changes in the crystal lattice and the morphological changes. These structural changes were found to originate ultimately from the remarkable change in the molecular conformation between trans and gauche forms. In order to extract the essentially important factors governing this trans-gauche conformational change in the phase transition, the molecular dynamics calculation was carried out, giving relatively good reproduction of the observed structural changes.
Manufacturing Aluminum Sandwich Structures by Means of Superplastic Forming
Authors: Impiö P. , Pimenoff J. , Hänninen H. , Heinäkari M. 
Published: April 2011

AbstractThis paper examines the possibilities of manufacturing large-scale aluminium sandwich structures using superplastic forming. The materials tested were Mg-alloyed production quality aluminium (Al 5083-0, Al 5083-H321) and Aluminium 1561. Tensile tests at elevated temperatures were performed in order to establish the suitability of the test materials for superplastic forming. The microstructural changes in the test material specimens were examined. Thereafter numerical simulation of the Al 5083-0 forming process was conducted based on the tensile test results. The numerical simulation results were subsequently used to estimate forming parameters and the feasibility of manufacturing large-scale structures by superplastic forming.The results indicate that higher strain can be reached at higher temperatures for the test materials. Aluminium alloy 1561 exhibited the largest elongation to fracture and Al 5083-H321 the smallest. Strain appeared to be temperature dependent but not much affected by the strain rate. Metallographic examination clarified that Al-5083-0 and AI-5083-H321 showed susceptibility for cavity forming whereas Aluminium 1561 formed relatively few voids. The numerical simulation indicated that Al 5083-0 can be superplastically formed using relatively low forming pressure (0.9 – 1.4 bar).
A TEM Study of Dynamic Continuous Recrystallization in a Superplastic AL-4MG-0.3SC Alloy
Authors: Dougherty L.M. , Robertson I.M. , Vetrano J.S. 
Published: April 2011

AbstractAn Al-4Mg-0.3Sc alloy, aged at 280°C for 8 hours and cold rolled to a 70% reduction, exhibited dynamic recrystallization during superplastic forming at 460°C and at a strain rate of 10−3sec−1. To understand the progression of recrystallization during forming, specimens were deformed under these same conditions to 0.1, 0.2, 0.4 and 0.8 true strain and studied postmortem using optical microscopy, transmission electron microscopy and orientation imaging microscopy. The microstructural evolution that occurred between each strain state was directly observed during deformation experiments at a nominal temperature of 460°C in the transmission electron microscope. These in-situ experiments showed the migration, coalescence, disintegration and annihilation of subboundaries. This combination of post-mortem analysis of specimens strained in bulk with real time observations made during these in-situ experiments allows the mechanisms operating during dynamic continuous recrystallization to be ascertained.
Creep deformation in a 3mol% Y2O3-Stabilized Tetragonal Zirconia
Authors: Morita K. , Hiraga K. , Sakka Y. 
Published: April 2011

AbstractThe high temperature deformation behavior of a 3mol% yttria-stabilized tetragonal zirconia (3Y-TZP) is examined. The analysis of creep strain rate, which was monitored directly with an optical extensometer and corrected for the current grain size, reveals a sigmoidal feature in the true stress-creep rate relationship. At lower stresses, a stress exponent n of ∼1.6 incorporated with a grain size exponent of 2.0 suggests the intervention of a lattice diffusion creep mechanism. For higher stresses where n ∼2.7, evidence of intragranular dislocation activities suggests that dislocations may play an important role in the accommodation process for grain boundary sliding in 3Y-TZP.
A Mechanism for Magnetically Driven Shape Memory Alloys
Authors: Ferreira P. J. , Vander Sande J. B. 
Published: April 2011

AbstractA mechanism for shape memory alloys driven by a magnetic field is proposed. The mechanism involves the motion of twin dislocations in response to the application of a magnetic field. As a consequence, twin variants oriented favorably with respect to the magnetic field direction will grow. The maximum pressure that can be exerted at the twin dislocations is when the magnetic field is at angle . The shape memory effect is significantly affected by the presence of impurities, second-phase particles and grain boundaries
Magnetoimpedance: a Choice Property for Smart Materials
Authors: García K.L. , Valenzuela R. 
Published: April 2011

AbstractA phenomenon known as Giant Magnetoimpedance (GMI) is attracting interest both for its technological applications in magnetic field sensors and for its physical basis. In this paper, a review of GMI is presented: first, a brief description of the main characteristics of GMI is discussed, an overview of the main applications is presented, and finally, an interpretation of the physical basis underpinning GMI is proposed
Structural Changes on Photochromism of Organic-Inorganic Hybrid Materials
Authors: Kuboyama Keiichi , Matsushige Kazumi 
Published: April 2011

AbstractSome transition metal oxides are known to exhibit the reversible coloration phenomena. Tungsten oxide is one of such materials and exhibits the photochromism and the electrochromism. It is known that the coloration phenomena in the tungsten oxide hydrate are caused by the redox reaction. We found that the photochromic efficiency became extremely higher by addition of some organic materials to the tungsten oxide hydrate and we have studied the mechanism of such a remarkable photochromic enhancement. In some spectroscopic measurement as FT-IR (Fourier transform infrared spectroscopy) and XPS (X-ray photoelectron spectroscopy), we obtained interesting features as follows. The addition of an organic material leads to reducing the tungsten oxide hydrate to smaller pieces, that is, the surface area of the pieces that can react with the additive increases. Moreover, it was found that specific sites in the additive are oxidized when the sample colors. The fact suggests that the additives having such specific sites can enhance the photochromism of the tungsten oxide hydrate