bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preliminary Performance Assessment for Deep Borehole Disposal of High-Level Radioactive Waste
Authors: Swift Peter N. , Arnold Bill W. , Brady Patrick V. , Freeze Geoff , Hadgu Teklu , Lee Joon H. 
Published: June 2019

ABSTRACTDeep boreholes have been proposed for many decades as an option for permanent disposal of high-level radioactive waste and spent nuclear fuel. Disposal concepts are straightforward, and generally call for drilling boreholes to a depth of four to five kilometers (or more) into crystalline basement rocks. Waste is placed in the lower portion of the hole, and the upper several kilometers of the hole are sealed to provide effective isolation from the biosphere. The potential for excellent long-term performance has been recognized in many previous studies. This paper reports updated results of what is believed to be the first quantitative analysis of releases from a hypothetical disposal borehole repository using the same performance assessment methodology applied to mined geologic repositories for high-level radioactive waste. Analyses begin with a preliminary consideration of a comprehensive list of potentially relevant features, events, and processes (FEPs) and the identification of those FEPs that appear to be most likely to affect long-term performance in deep boreholes. The release pathway selected for preliminary performance assessment modeling is thermally-driven flow and radionuclide transport upwards from the emplacement zone through the borehole seals or the surrounding annulus of disturbed rock. Estimated radionuclide releases from deep borehole disposal of spent nuclear fuel, and the annual radiation doses to hypothetical future humans associated with those releases, are extremely small, indicating that deep boreholes may be a viable alternative to mined repositories for disposal of both high-level radioactive waste and spent nuclear fuel.
Synthesis Design of TiO2 Nanotubes and Nanowires and Photocatalytic Applications in the Degradation of Organic Pollutants in the Presence or not of Microorganisms
Authors: Turki Asma , Ibáñez Pilar Fernández , Ghorbel Abdelhamid , Kochkar Hafedh , Guillard Chantal , Berhault Gilles 
Published: June 2019

ABSTRACT1 D TiO2 nanomaterials (nanotubes, nanowires) were synthesized through hydrothermal treatment of TiO2 powder (P25) in concentrated alkaline solutions (NaOH for nanotubes, KOH for nanowires) followed by calcination at varying temperatures between 400°C and 700°C. Samples were characterized by HRTEM, XRD, Raman spectroscopy, and N2 adsorption-desorption isotherms. High surface area nanotubular TiO2 materials can maintain their 1D morphology up to a temperature of calcination of 400°C while changing their phase from hydrogenotitanate to anatase. The use of KOH leads to a retarded formation of anatase. Photocatalytic results showed that TiO2 anatase nanotubes calcined at 400°C can degrade formic acid with a rate constant four times higher than for P25. A direct correlation between surface area and photocatalytic activity explains the much higher activity of TiO2 anatase nanotubes. On the opposite, for the degradation of phenol, P25 remains more active. In the disinfection of water, contrary to P25, the high surface area of TiO2 nanotubes allows the simultaneous degradation of formic acid and the inactivation of pathogen fungus showing the interest of such materials for the treatment of wastewater.
Smart Hydrogels Designed for use in Microfabricated Sensor Arrays
Authors: Bates Jeffrey S. , Cho Seung Hei , Tathireddy Prashant , Rieth Loren W. , Magda Jules J. 
Published: June 2019

ABSTRACTHydrogels are considered smart materials because they respond to environmental stimuli. Sensors that monitor the body’s pH levels would be helpful for doctors to determine the severity of a patient’s condition, especially if they exhibit signs of shock. The motivation of this project is to create a biomedical device that can be worn sublingually or implanted into the body to help doctors with diagnosing a patient’s condition. The magnitude of the swelling/deswelling behavior can be measured by placing a sample of the hydrogel in a piezoresistive sensor. The degree of swelling/deswelling is directly proportional to the change in pH of the aqueous solution it is placed in. In this study, a variety of compositions of pH responsive hydrogels were designed and tested to determine the response time and magnitude for use in both macro and micro sensor arrays. This pressure sensor has been designed for use with thinner gels than have been used in the past. The results for swelling time and magnitude were compared to determine the effect of the thickness of the hydrogel samples on the swelling/deswelling kinetics of the material in order to find the appropriate composition, thickness and device that will yield the desired response rate and sensitivity.
Dielectric Morphology and RRAM Resistive Switching Characteristics
Authors: Bersuker G. , Butcher B. , Gilmer D. C. , Larcher L. , Padovani A. , Geer R. , Kirsch P. D. 
Published: June 2019

ABSTRACTThe connection between the bi-polar hafnia-based resistive-RAM (RRAM) operational characteristics and dielectric structural properties is considered. Specifically, the atomic-level description of RRAM, which operations involve the repeatable rupture/recreation of a localized conductive path, reveals that its performance is determined by the outcome of the initial forming process defining the structural characteristics of the conductive filament and distribution of the oxygen ions released from the filament region. The post-forming ions spatial distribution in the cell is found to be linked to a degree of dielectric oxygen deficiency, which may either assist or suppress the resistive switching processes.
Metastable Phase Equilibria in Co-Deposited Ni1−xZrx Thin Films
Authors: Rubin J. B. , Schwarz R. B. 
Published: June 2019

AbstractWe determine the glass forming range (GFR) of co-deposited Ni1−xZrx (0 < x < 1) thin films by measuring their electrical resistance during in situ constant-heating-rate anneals. The measured GFR is continuous for 0.10 < x < 0.87. We calculate the GFR of Ni-Zr melts as a function of composition and cooling rate using homogeneous nucleation theory and a published CALPHAD-type thermodynamic modeling of the equilibrium phase diagram. Assuming that the main competition to the retention of the amorphous structure during the cooling of the liquid comes from the partitionless crystallization of the terminal solid solutions, we calculate that for dT/dt = 1012 K s−1, the GFR extends to x = 0.05 and x = 0.96. Better agreement with the measured values is obtained assuming a lower ‘effective’ cooling rate during the condensation of the films.
Atom Probe Studies of Interfaces in Metallic Multilayers
Authors: Cerezo Alfred , Hyde Jonathon M. , Hetherington Mark G. , Petford-Long Amanda K. 
Published: June 2019

AbstractThe atom probe field-ion microscope has been used to study the diffusion at interfaces in metallic multilayers deposited directly onto field-ion specimens and to develop models for the solid state reactions occuring at the atomic-scale in multilayer systems. Results are presented for the low temperature annealing of a Co-Ni multilayer. Intermixing over about 2 atomic planes is found even in as-deposited samples, extending to mnm after heating at 300°C for 1 hour. Using atom probe results from bulk alloys, a Monte Carlo simulation has been developed for the Fe-Cr system, in which a miscibility gap exists, and is being used in an attempt to model the behaviour of interfaces in Fe-Cr multilayers. Preliminary results are presented, showing that interfaces which are initially mixed over 10 atomic planes become sharper by an ‘interface spinodal’ reaction.
In SituHvem of Crystallization of Amorphous TiNi Thin Films
Authors: Moberly Warren J. , Busch J. D. , Johnson A. D. , Berkson M. H. 
Published: June 2019

AbstractTiNi alloys have been extensively studied for their shape memory properties, arising from a martensitic transformation between the cubic B2 crystal structure and the monoclinic B19′ structure. However, only recently has the application of TiNi alloys as thin film actuators been considered. Well-controlled thicknesses of TiNi films have been deposited via d.c. magnetron ion sputtering, with as-deposited films exhibiting an amorphous structure. These ductile metallic glass films may be bent into various macroscopic shapes and then heated to crystallize the B2 structure, thereby determining its parent (memory) shape.In situhigh voltage electron microscopy (HVEM) heating and cooling experiments are utilized to observe the crystallization of the B2 structure and the martensitic transformation from B2 to B19∼500°C to ∼600°C. Isothermal annealing determines the kinetics of the crystallization process to be nucleation limited. The nucleation of B2 crystallites in thicker regions of TEM specimens, which occurs prior to nucleation in thinner regions, indicates that nucleation does not occur preferentially at surfaces, but rather homogeneously. After crystallization is completed, the existence of random orientations of B2 grains provides films that will exhibit shape memory in any desired orientation. Video-recording of the crystallization processes has been acquired.
Rapid Thermal-Pulsed Diffusion of Zn into GaAs
Authors: Tiku S.K. , Delaney J.B. , Gabriel N.S. , Yuan H.T. 
Published: June 2019

ABSTRACTA rapid thermal process for the diffusion of Zn into GaAs has been developed
to fulfill the need for highly doped p type layers in GaAs technology. The
process uses a solid Zn:Si:O source layer and a quartz-halogen lamp system
for the thermal drive-in. Surface concentrations of the order of
1020/cm3 have been achieved with good depth
reproducibility and low lateral diffusion. Specific contact resistance of
Au:Zn/Au alloyed contacts fabricated using this process was in the
10−7 ohm-cm2 range.
Thermodynamic and Kinetic Studies of Pulsed-Laser Annealing from
Transient Conductivity Measurements
Authors: Peercy P.S. , Thompson Michael O. 
Published: June 2019

ABSTRACTSimultaneous measurements of the transient conductance and time-dependent
surface reflectance of the melt and solidification dynamics produced by
pulsed laser irradiation of Si are reviewed. These measurements demonstrate
that the melting temperature of amorphous Si is reduced 200 ± 50 K from that
of crystalline Si and that explosive crystallization in amorphous Si is
mediated by a thin (≤ 20 nm) molten layer that propagates at ~ 15 m/sec.
Studies with 3.5 nsec pulses permit an estimate of the dependence of the
solidification velocity on undercooling. Measurements of the effect of As
impurities on the solidification velocity demonstrate that high As
concentrations decrease the melting temperature of Si (~ 150 K for 7 at.%),
which can result in surface nucleation to produce buried melts. Finally, the
silicon-germanium alloy system is shown to be an ideal model system for the
study of superheating and undercooling. The Si50Ge50
alloy closely models amorphous Si, and measurements of layered Si-Ge alloy
structures indicate superheating up to 120 K without nucleation of internal
melts. The change in melt velocity with superheating yields a velocity
versus superheating of 17 ± 3 k/m/sec.
Temperature Dependent Orientational Epitaxy of C60 Films on Noble Metal (111) Surfaces; Au, Ag and Cu
Authors: Fartash A. 
Published: June 2019

ABSTRACTHigh quality C60 films are grown on surfaces of (111) oriented noble metal substrates (i.e., Au, Ag, and Cu) by using a molecular beam deposition method. The structures of these films are compared with each other on substrates that are prepared to have similar in-plane mosaic widths (σ1.25*) as determined by their x-ray diffraction scans. The in-plane structures of these films are studied for substrate temperatures ranging from σ110 to 290°C. Although most materials grow in high symmetry small-lattice-mismatch in-plane orientations, C60 films (depending on their growth temperatures) grow in orientations that are poorly lattice matched with their Au(111) and Ag(111) substrates. In these orientations, C60 structures can be lattice matched only over large unit cells, forming “long-period ” structures. These “long-period ” structures coexist with “commensurate” structures that are almost perfectly lattice matched on twheitshe osur bpsrterdaotems.i naOten Au(111) substrates, a structural transition is observed between two distinct long-period structures (at Tc, σ150 °C). Although Au and Ag have similar lattice spacings, this transition is absent on Ag(111) substrates. The question of orientational epitaxy for C60 layers is examined in the context of several well-known systems in condensed matter physics.
Electrochemical Synthesis and Processing of Materials: From Fractal Electrodes to Epitaxial Thin Films
Authors: Family Fereydoon 
Published: June 2019

ABSTRACTElectrochemical processes hold great promise as flexible and effective tools for synthesis and processing of a wide range of materials from fractal electrodes to epitaxial nanostructures. The key to successful application of electrochemical techniques is in understanding the kinetic processes which control the evolution and the morphology of the surface at the solid-liquid interface. This paper provides a review of recent advances made by different electrochemical communities in recent years in studies of the growth and modification of a wide variety of materials. The topics covered include studies of pattern formation and growth of dendritic and fractal structures in electrode-position, kinetic roughening and dynamic scaling of surfaces fluctuations during electrochemical deposition and dissolution, as well as recent progress in electrochemical growth of epitaxial layers and nanostructures.
Molecular Grafting on Si(111) Surfaces: An Electrochemical Approach
Authors: Henry de Villeneuve C. , Pinson J. , Ozanam F. , Chazalviel J. N. , Allongue P. 
Published: June 2019

ABSTRACTThis works addresses the question of the direct attachment of organic molecules on Si(111) by an electrochemical method. Anodic grafting of -OR group is demonstrated by in-situ STM and the LDOS characterized. The grafting of aryl groups, by reduction of aryl diazonium salts in aqueous solution, is also described. This approach leads to well ordered and close-packed thin molecular films with various functionality. Different chemical and structural characterizations conclude to a Si-C binding, between the Si surface and aryl groups. The stability of films is also investigated.
Characterization of the Silicon / Fluoride Solution Interface by In-Situ Microwave Reflectivity
Authors: Natarajan Arun , Oskam Gerko , Oursler Douglas A. , Searson Peter C. 
Published: June 2019

ABSTRACTEtching of silicon in aqueous fluoride solutions can lead to almost atomically flat surfaces with a low density of surface states and recombination centers. The final quality of the surface, however, is strongly dependent on the solution composition and pH. We have performed electrochemical impedance spectroscopy in combination with potential modulated microwave reflectance spectroscopy (PMMRS) to elucidate the processes occurring at the surface during etching. PMMRS is a novel technique that only probes the free carriers in the conduction and valence bands and is, under certain conditions, not affected by processes involving electrically active surface states or charge transfer. This unique feature allows us to separate the energetics of the semiconductor from surface processes. Microwave reflectivity (δR) versus potential curves in HF solutions demonstrate the variation of the flatband potential as a function of pH. The AR response in the narrow potential region around the flatband potential and at more negative potentials is also discussed.
Influence of a silicon cap on SiGe passivation by anodic oxidation
Authors: Rappich J. , Sieber I. , Schöpke A. , Füssel W. , Glück M. , Hersener J. 
Published: June 2019

ABSTRACTWe applied electrochemical oxidation as a low thermal budget process for the passivation of thin SiGe epilayers on Si substrate and compared the results with those obtained on thermally oxidized layers. The use of a thin silicon cap on the SiGe layer reduces the electrochemical corrosion with dissolution of Ge during oxidation and leads to a higher amount of GeO2 in the oxidized SiGe layer than anodic oxidation without a Si cap. The protected SiGe layer shows a slight Ge enrichment at the interface which is different from the behavior of the non-protected SiGe layer. The highest Ge pile-up is achieved by the thermally oxidized samples where the oxide layer is formed by nearly pure SiO2. Using photoluminescence spectroscopy we showed that the passivation and quality of the interface is best if no Ge enrichment occurs. The results suggest that electrochemical oxidation of SiGe layers is preferable to high temperature processing.
Discrete Metal Deposition on Hydrogen Terminated Silicon Surfaces: Kinetics, Morphologies and Sensor Applications
Authors: Chyan Oliver , Chen Jin-Jian , Wu Junjun , Chien Steve , Liu Min 
Published: June 2019

ABSTRACTThe presence of ultra-trace (as low as 1010 – 1013 atoms/cm2) quantities of metal contaminants on silicon substrates is well known to adversely affect the electrical properties of the silicon based microelectronic devices. In this paper, we report our most recent experimental findings on the trace metal deposition mechanisms and its interplays with silicon substrate surface properties at specific chemical environments. The emphases were on the deposition kinetics and morphology, especially at the early stage of metal out-plating process. For instance, our atomic force microscopy results revealed that the Cu deposition on H-Si(100) surface was dominated by nucleation of nanometer-sized Cu nuclei at the initial stage (less than 60 seconds). The growth of the existing Cu nuclei was suppressed for the initial nucleation period until all the nucleation sites were consumed. The number of nucleation sites were found to closely relate to wafer intrinsic properties and solution compositions. A novel sensor which provides direct detection of part-per-trillion level of metal ion impurities in wet cleaning solutions will also be presented.
Electrodeposition of Copper / Cuprous Oxide Nanocomposites
Authors: Swrrzer Jay A. , Bohannan Eric W. , Golden Teresa D. , Hung Chen-Jen , Huang Ling-Yuang , Shumsky Mark 
Published: June 2019

ABSTRACTNanocomposite films of copper metal and cuprous oxide were electrodeposited at room temperature from an alkaline copper(11) lactate solution. The electrode potential oscillated spontaneously during constant-current deposition of the composites. The oscillations were periodic in a stirred solution, but became chaotic in unstirred solution. For a given current density the phase composition was a strong function of solution pH. As the pH was increased, the cuprous oxide content increased. At pH 12, no oscillations were observed, and pure cuprous oxide was deposited. At pH 9, the phase composition varied from pure cuprous oxide at current densities below 0.1 mA/cm2 to 96 mole percent copper at 2.5 mA/cm2.
Nanowires Grown Electrochemically in Porous Templates
Authors: Schönenberger C. , Van Der Zande B. M. I. , Fokkink L. G. J. 
Published: June 2019

ABSTRACTMetallic nanowires are synthesized by electrochemical growth in nanopores of either track-etched polycarbonate membranes or anodized aluminum films. The potentiostatic growth is systematically investigated for track-etched membranes with nominal pore diametersdN between 10 and 80 nm. For this model system, the cross-section of the metallic wires is found to vary: the wire diameter, which is argued to directly reflect the pore diameter, is observed to be substantially larger in the middle than at both ends. Therefore, the pores are not cylindrical with constant cross-section, but appear to be ‘cigar-like’. Inside the membranes, the pores are wider by up to a factor 3.The aluminum oxide template has successfully been used to prepare a colloidal suspension of gold needles (anisotropie metallic colloid) by growing Au wires in the pores, dissolving the aluminum oxide and finally stabilizing and dispersing the ‘nano-rods’ in water. Visible near-infrared absorption spectroscopy reveal two absorption maxima caused by the anisotropy of these scatterers. The maxima can be assigned to a longitudional and transversal plasma resonance.
Defect Structure and Crystallographic Texture of Polycrystalline Electrodeposits
Authors: Merchant H. D. , Girin O. B. 
Published: June 2019

ABSTRACTThe polycrystalline electrodeposits of metals and alloys are characterized by exceptionally fine, equiaxed grain structure; the grain sizes two to four orders of magnitude smaller than those encountered in the bulk metals are generally obtained. Under the conditions of high cation discharge rate, twins accommodate interface growth; elongated grains and columnar morphology then become the common features. The dislocation density can be very high; the dislocations reside primarily as complex substructural configurations which are inherently unstable to thermal or mechanical stimuli. Vacancies, microvoids and vacancy/impurity complexes are endemic to deposits. The defect structure infrastructure (dislocation density and configuration, twinning frequency and hydrogen bubbles) is controlled by the deposition overpotential which also determines the preferred crystallographic texture. When the texture axis is parallel to the twin plane, anisotropie grain structure and columnar morphology are promoted; when the texture axis is perpendicular to the twin plane, a layered structure forms. The textured electrodeposit generates a duplex grain and subgrain structure. The random grains are small and defect saturated; the oriented grains are much larger and relatively free from crystal defects. The incidence of random grains, their size and defect concentration also depend upon the melting temperature of the metal.
Composite Films of Copper / Boron Nitride and Nickel / Boron Nitride
Authors: Hepel Maria , Tannatoli Tania , Baxter Christopher , Stephenson Richard 
Published: June 2019

ABSTRACTThe formation and characterization of composite films of copper/boron nitride (Cu/BN) and nickel/boron nitride (Ni/BN) are described. Composite Cu/BN and Ni/BN films were synthesized by a metal electrodeposition from suspensions of boron nitride particles on carbon steel substrates. The effects of concentration of boron nitride in the solution, temperature, potential and various additives on the morphology of composite films have been investigated. The morphology of these films was examined using Scanning Electron Microscopy. The elemental analysis for boron, nitrogen, copper and nickel was performed using Energy Dispersive X-ray Spectroscopy (EDS), and a Microprobe X-ray Analyzer. The Vickers hardness of Cu/BN and Ni/BN films prepared under different conditions was also investigated. It has been found that the composite Cu/BN and Ni/BN films have an increased microhardness as compared to the respective pure metal films. The effects of deposition potential, temperature, concentration of BN and presence of various additives on the microhardness of Cu/BN and Ni/BN films have been investigated.
Time-Resolved Measurements of Overlayer Ordering in Electrodeposition
Authors: Finnefrock A. C. , Bullert L. J. , Ringland K. L. , Tingi P. D. , Abruña H. D. , Brock J. D. 
Published: June 2019

ABSTRACTWe report in situ time-resolved surface x-ray scattering measurements of the underpoten-tial deposition of Cu2+ on Pt(111) in the presence of Cl− in HClO4 solution. Chronoamperometric (current vs. time) measurements indicate that after a potential step, the electrode-position current decays to 1/e of its initial value in at most 0.12 seconds. In contrast, our simultaneous time-resolved surface x-ray scattering data reveal that the overlayer requires on the order of two seconds to develop long-range periodic order. These results demonstrate that the kinetics of surface ordering can be significantly different from the kinetics of charge-transfer and illustrate the power of time-resolved surface x-ray scattering for in situ studies of electrodeposition.