bluuebunny/crossref_metadata_2025 huggingface dataset:
Conjugate Polymer Induced Enhancement of THz Radiation in Semiconductors
Authors: Hwang Jenn-Shyong , Lin Hui-Ching , Huang Yin-Chieh , Lin Kuang-I , Chang Jer-Wei , Guo Tzung-Fang
Published: September 2007

Conjugate polymer induced enhancement of terahertz radiation is observed for the first time in this report. Terahertz radiation (THz) from the surfaces of various semiconductor wafers and microstructures is studied. The intensities of the THz radiation from the surfaces of certain semiconductors with a thin layer of conjugate polymer (2, 3-dibutoxy-1, 4-polyphenylenevinylene (DB-PPV)) deposited on their surfaces are greatly enhanced. The enhancement of THz radiation depends on the mechanism of inducting the THz radiation. Modulation spectroscopy of photoreflectance (PR) is employed to investigate the change in the built-in electric field and surface or interface state densities, which are closely related to the enhancement of the THz radiation.
Growth of InN by Plasma-Assisted Molecular Beam Epitaxy on InN/GaN and p-GaN Templates
Authors: Readinger Eric D. , Chern Grace , Reed Meredith , Shen P. , Wraback Michael , Syrkin Alexander , Usikov Alexander , Kovalenkov Oleg , Ivantsov Vladimir , Dmitriev Vladimir
Published: September 2007

InN is grown by plasma-assisted molecular beam epitaxy on templates prepared by hydride vapor phase epitaxy. These uniques templates consist of InN/GaN and p-GaN epilayers. Homoepitaxy creates challenges for surface preparation prior to growth. Quality InN layers as seen by x-ray diffraction and photoluminescence data are developed when growing on HVPE InN/GaN templates. InN growth on p-GaN provides a novel solution for p-down diodes utilizing InN. The in situ surface preparation of these templates is a challenge preventing undesirable band bending at the hetero-interface. Two in situ surface preparations are attempted with no significant impact on the quality of the InN layer.
Stability Effects of Reflective Mirror on GaN LED/Mirror/Si Via Wafer Bonding and Laser Lift-Off Techniques
Authors: Horng Ray-Hua , Huang Shao-Hua , Wuu Dong-Sing , Lin Chao-Kun , Liu Heng
Published: September 2007

GaN vertical-conducting light-emitting diodes (LEDs) with high thermal stability mirror on Si substrate have been fabricated using a combination of wafer-bonding and laser lift-off techniques. The thermal stabilities of NiO/Ag and NiO/Ag/Ni mirrors in vertical GaN/mirror/Si structure were studied. It was found that the NiO/Ag/Ni mirror presents the best performance, where the specific contact resistance and the reflectivity can achieve 8.37 x 10-3 Ω-cm2 and 92 % at 470 nm after oxidation annealing (500oC for 10 min). The top Ni layer could protect the Ag mirror from degradation of the high temperature annealing. The output powers of GaN/sapphire LED and LEDs with NiO/Au/Ag and NiO/Ag/Ni mirrors show 4.5, 4.3 and 13 mW, respectively.
Influence of Temperature on the Saturation of the Forward Voltage Drift in SiC Pin Diodes
Authors: Caldwell Joshua D. , Stahlbush Robert , Glembocki Orest , Hobart Karl
Published: September 2007

Shockley stacking faults (SSFs) in hexagonal SiC are known to induce an increase in the forward voltage drop of bipolar devices, such as pin diodes. Recent annealing studies have illustrated that propagated SSFs can not only propagate under current or optical injection conditions, but under low temperature (210-7000C) annealing can contract completely. Associated with this contraction is the complete and repeatable recovery of the drift. These observations have brought about questions as to the driving force for SSF propagation and contraction. Here we report that following extended periods of forward bias operation, the drift of 4H-SiC 10kV pin diodes increased until an eventual saturation occurred. At this point, further current injection no longer induced any further SSF propagation or increases in . Furthermore, the maximum attainable drift was inversely proportional to the stressing temperature, meaning that at elevated temperatures, the degree to which the SSFs may propagate is significantly limited.
An Overview of Wide Bandgap SiC Sensor and Electronics Development at NASA Glenn Research Center
Authors: Hunter G. , Neudeck Philip G. , Beheim Glenn , Okojie Robert S. , Chen Liangyu , Spry David J. , Trunek Andrew
Published: September 2007

A brief overview is presented of the sensors and electronics development work ongoing at NASA Glenn Research Center which is intended to meet the needs of future aerospace applications. Three major technology areas are discussed: 1) high temperature SiC electronics, 2) SiC gas sensor technology development, and 3) packaging of harsh environment devices. Highlights of this work include world-record operation of SiC electronic devices including 500{degree sign}C JFET transistor operation with excellent properties, atomically flat SiC gas sensors integrated with an on-chip temperature detector/heater, and operation of a packaged AC amplifier. A description of the state-of-the-art is given for each topic. It is concluded that significant progress has been made and that given recent advancements the development of high temperature smart sensors is envisioned.
High Quality Single Crystal Al-catalyzed Si Nanowire
Authors: Whang Sungjin , Lee Sungjoo , Yang W. , Cho B. J. , Liew Y. F. , Li K , Bera L. K. , Kwong D.-L.
Published: September 2007

High quality single crystal Si nanowires with diameters ranging from 10 to 200nm have been successfully grown by using Al catalyst via vapor-liquid-solid mechanism. Critical issues such as the effects of surface oxidation of Al seeding layer on the growth of Si nanowires and selective removal of metal- catalyst after nanowire growth have been systematically studied. Results show that the growth of Si nanowire is strongly dependent on the surface oxidation of Al seeding layers. It is also found that metal-contamination-free Si nanowires can be achieved by selective etching of remaining Al particles from nanowires, providing a Si nanowire as a CMOS compatible building block for future nanoelectronics applications.
The Role of Chloride in Al Oxide Surface Transformations and Pitting -an AFM Study
Authors: Vasiljevic Natasa , Copeland Robert G. G. , Missert N. A.
Published: September 2007

In this study we used the in situ AFM technique to examine the Al surface morphological transformations during anodic polarization. In order to elucidate the possible role of chloride in the surface oxide breakdown process, we conducted in situ AFM polarization studies in sulfate (50 mM K2SO4) and chloride (50 mM NaCl) solutions where Al corrosion behavior is known to be different. The results show different changes and structures in two electrolytes: (a) for the case of polarization in sulfate solutions, uniform changes of oxide morphology are observed most likely resulting from oxide hydration and growth; (b) for the case of polarization in chloride solutions, morphological changes are observed to be surface-site energy dependant. The changes of Al-oxide are very pronounced around the regions of faceted edges and grain boundaries i.e. regions of higher local roughness and curvature.
Influence of Cold Working on the Resistance of Stainless Steels to Pitting Corrosion
Authors: Peguet Lionel , Malki Brahim , Baroux Bernard
Published: September 2007

The influence of cold rolling and tensile deformation on the resistance to pitting corrosion of two stainless steels (AISI 304 and AISI 430) has been investigated. Two electrochemical techniques under free corrosion and potentiostatic conditions have been carried out so that pit initiation and propagation could be analysed separately. Plastic deformation is shown to act differently depending on the pitting stage under consideration. (i) The pit-initiation frequency shows a maximum after 20% cold rolling reduction or 10% tensile deformation. (ii) The pit propagation rate increases monotonously with cold rolling reduction. In addition, it is evidenced that strain-induced martensite is not a necessary condition for the susceptibility of cold worked SS to pit initiation. The unexpected behaviour of pitting initiation is more likely related to the dislocations features resulting from the successive cold-working stages.
Corrosion Inhibition of AA2024-T3 by Vanadates
Authors: Iannuzzi Vanadates M. , Frankel Gerald
Published: September 2007

The speciation of vanadate solutions and the resulting inhibition of oxygen reduction and corrosion of AA2024-T3 were investigated. 51V NMR is very useful for assessing vanadate speciation. Clear metavanadate solutions contain no decavanadate, which forms whenever the pH was decreased by the addition of acid. Orange decavanadate solutions contain no monovanadate, even when the pH is adjusted to high values. Monovanadate is a potent inhibitor in contrast to decavanadate. Inhibition by monovanadate seems to result from an adsorption mechanism rather than reduction. Monovanadate effectively protects S phase particles. Aging of high-pH decavanadate solutions does not improve the inhibition performance or result in complete depolymerization of the decavanadate.
Effect of Heat Treatment on Grain Boundary Nanostructure and Corrosion of Low Copper AlMgSi Alloy
Authors: Hurlen Larsen Magnus , Walmsley John C. , Lunder Otto , Nisancioglu Kemal
Published: September 2007

AlMgSi (6000-series) aluminium alloys are generally known to be re-sistant to intergranular corrosion (IGC). However, unfavourable alloy-ing and thermomechanical history may introduce susceptibility to IGC. A model alloy in the 6000-series, with 0.2 wt% Cu, was studied using an accelerated corrosion test. In the naturally aged T4 temper, the ma-terial did not exhibit localized corrosion, while in the underaged state (below peak strength), the alloy became highly susceptible to IGC. Samples aged to peak strength T6 temper or overaged were nearly re-sistant to IGC, exhibiting only shallow, localized IGC and pitting. TEM investigation of the IGC-susceptible material revealed nanosize AlMgSiCu particles along the grain boundaries, along with Cu-enriched nanofilm connecting the particles, indicating the cause of sharp IGC propagation. Further ageing caused coarsening of the grain boundary film thereby destroying its continuity and giving increased resistance against IGC.
Understanding Localized Corrosion through Electrochemical Measurements
Authors: Burstein Gordon T.
Published: September 2007

A discussion is presented of the understanding of localised corrosion which can be gained using simple electrochemical measurements. The discussion centres around the origins of pitting corrosion and its development from a minute site which undergoes dramatic depassivation through rapid dissolution to stable pitting.
Programming Void Populations in the Passive Oxide of Aluminum in an Attempt to Correlate Evolving Nanostructure with Passivity Loss
Authors: Zavadil Kevin R. , Kotula Paul , Soltis Jozef , Krouse Donal
Published: September 2007

Galvanostatic polarization in aqueous chloride media is shown to be a viable method for controlling the characteristics of a void and pore population within the passive oxide on aluminum thin films. Current density and anion type are demonstrated to be effective control parameters of nanoscale feature density and size. The use of the borate anion with chloride regulates the void formation and points to a mechanism where competitive anion adsorption at the barrier layer dictates the fraction of current density that is channeled into void formation versus oxide growth. Preliminary results are presented for microcapillary-based measurements of pit initiation in the presence of a pre-programmed void population. These results show the presence of an induction time with pre-existing voids. These findings suggest that where voids may play a role in pit initiation, other factors may be necessary in a more concerted mechanism of oxide breakdown and pit initiation.
Crevice Corrosion of Ni-Cr-Mo Alloys
Authors: Jakupi Pellumb , Zagidulin Dmitrij , Noël Jaimie , Shoesmith David W.
Published: September 2007

The crevice corrosion of Alloy-22 has been studied under galvanostatic conditions in 5 mol/L NaCl at 120{degree sign}C, since the process was very difficult to initiate under natural corrosion conditions. Stable propagation could be achieved for applied currents of {greater than or equal to} 10 μA, but not for applied currents {less than or equal to} 5 μA, despite a large number of initiation attempts. Initiation appears to require a potential sufficiently positive (200 mV vs. sat'd Ag/AgCl) for the injection of defects into the Cr2O3 barrier layer. Propagation occurs preferentially at the edge of the creviced area and spreads across, rather than penetrating into, the alloy surface. This may be due to the presence of a protective Mo/W gel layer on the exposed alloy surface.
Electrochemical Testing of Exfoliation Corrosion Sensitivity of Aluminum Alloys
Authors: Marlaud Thorsten , Malki Brahim , Deschamps Alexis , Reboul Max , Baroux Bernard
Published: September 2007

This paper presents an investigation of exfoliation corrosion (EFC) of 7000 series aluminum alloys using a new electrochemical test. For this study two metallurgical states, namely T6 (peak hardness) and T76 (over-aged) of a new high strength 7XXX alloy have been investigated. The experimental protocol consists in a galvanostatic test in an optimized NaCl- NaNO3-AlCl3 electrolyte at pH~4, chosen less aggressive than that used in the standard EXCO test1. The real time fluctuations of the measured potentials, which are expected to contain relevant information on the exfoliation corrosion processes, have been analyzed. SEM observations in the early stages suggest that the measured potential transients are directly related to fracture of surface blisters, commonly evoked in the literature as the predominating mechanism in exfoliation corrosion. This new test opens a new way for quantifying the susceptibility to exfoliation corrosion in aluminum alloys.
SRET Evaluation of the Corrosion Behavior of Thixocast AZ91 Magnesium Alloy in Dilute NaCl Solution at Room Temperature
Authors: Jin Shize , Ghali Edward , Blawert Carsten , Dietzel Wolfgang
Published: September 2007

This work is aimed at examining the corrosion behavior of thixocast (TC) and die cast (DC) AZ91 alloy in dilute chloride solution using scanning reference electrode technique (SRET). The results showed that the as cast skins of TC and DC AZ91 alloy had much higher QEMF values than the bulk samples. The maximum local anode currents (MLAC) of the skins were much higher than those of the bulks. Both the skin and bulk of TC AZ91 alloy were more corrosion resistant than those of DC AZ91 alloy in this medium. The SRET results in 0.014 M NaCl were consistent with those obtained by electrochemical impedance spectroscopy (EIS) in 0.003 and 0.885 M NaCl solutions.
Determination of the Diffusivity of Cation Vacancy in the Passive Film on Ni
Authors: Jang Heejin , Ahn Sejin , Kwon Hyuksang
Published: September 2007

The diffusivity of the cation vacancy (DM) in the passive film formed on Ni in pH 8.5 buffer solution at ambient temperature was estimated using the Mott-Schottky analysis based on the Point Defect Model combined with the high field migration equations. The steady state behaviors of the passive film on Ni, such as current density, film thickness, and acceptor density, agreed with the postulations of the Point Defect Model. From the dependence of the acceptor density and steady state current density on film formation potential, DM for the passive film on Ni was determined to be 3.7×10-18 cm2s-1 by the high-field migration equations combined with the Point Defect Model.
An Analytical Modeling Method for Calculating the Current Delivery Capacity of a Thin-Film Cathode and the Stability of Localized Corrosion under Atmospheric Environments
Authors: Chen Zhuoyuan , Cui Fushuang , Kelly Robert G.
Published: September 2007

Corrosion resistant materials under atmospheric conditions can suffer from localized corrosion. The stability of such a localized corrosion site requires that the site (anode) must dissolve at a sufficient high rate to maintain the critical chemistry and a wetted surrounding area (cathode) provides matching cathodic current. An analytical method for evaluating the stability of localized corrosion of corrosion-resistant alloys under thin-layer (or atmospheric) conditions is presented. The maximum cathode current available depends on the cathode geometry, temperature, relative humidity, deposition density of salt (i.e., mass of salt per unit area of cathode), and interfacial electrochemical kinetics. The anode demand depends on the crevice geometry, the position of attack within the crevice, and the localized corrosion stability product. By coupling these two approaches, the stability of a crevice can be determined for a given environmental scenario. The method has been applied to the atmospheric localized corrosion of Type 316L stainless steel.
Modeling the Effects of Crevice Former, Particulates, and the Evolving Surface Profile in Crevice Corrosion
Authors: Agarwal Arun S. , Landau Uziel , Shan Xi , Payer Joe H.
Published: September 2007

Crevice corrosion may initiate in confined regions due to transport limitations, followed by an accumulation of a highly corrosive chemistry, capable of dissolving the metal. The metal and the crevice former surface roughness, the presence of particulates under the crevice former and the accumulation of solid corrosion products at the corroding site would significantly affect the current and potential distribution at the anode by increasing the ohmic potential drop. Most crevice corrosion models focus on a smooth walled crevice of uniform gap and do not account for the changing profile after crevice corrosion has been initiated. In this work we analyze the crevice (anodic) region and apply current and potential distribution models to examine the effects of the perturbed surface topography. The analysis focuses on three related issues: (i) the effects surface roughness of the metal and the crevice former, (ii) the effects of particulates under the crevice former, and (iii) the evolution of the crevice profile with corrosion product accumulation at the active, anodic region.
The Effect of Anions on the Passive Film Properties and Localized Corrosion Behavior of Alloy C-22
Authors: Pharkya Pallavi , Shan Xi , Payer Joe H.
Published: September 2007

This paper investigates corrosion behavior of Alloy C-22 in hot concentrated brines. The passive film behavior and localized corrosion properties of alloy C-22 as a function of nitrate and sulfate anions in concentrated chloride brines was investigated. Cyclic potentiodynamic polarization tests were used to study the general corrosion behavior of the alloy, Electrochemical Impedance Spectroscopy (EIS) and Mott-Schottky (M-S) were used to examine the electronic properties of the passive films, and constant potential tests were done to study crevice corrosion initiation, propagation and stifling of the alloy. The aim was to investigate the correlation between the electronic properties of the alloy's passive film and the localized corrosion susceptibility of the alloy. The results showed that anions had major impact on the repair- repassivation behavior but did not cause significant effect on the properties of passive film when it was intact.
Localized Corrosion Resistance of LTCSS-Carburized Materials to Seawater Immersion
Authors: Martin Farrel J. , Lemieux Edward , Newbauer Theresa , Bayles Robert , Natishan Paul , Khan Hal , Michal Gary , Ernst Frank , Heuer Arthur
Published: September 2007

The localized corrosion resistance of surface modified 316L austenitic stainless steel is evaluated. The surface modification process, a carburization technology termed Low Temperature Colossal Supersaturation (LTCSS), typically produces surface carbon concentrations of ~ 15 at %. Resistance to seawater pitting and crevice corrosion at ambient temperature is substantially increased. LTCSS treatment increased the seawater pitting potential by more than 600mV. Crevice corrosion did not initiate on LTCSS- treated 316L during week-long polarizations at 300mV in ambient temperature seawater, while untreated 316L initiated crevice corrosion in less than an hour and suffered significant corrosion damage.
Oxygen Reduction Characteristics on Ag, Pt, and Ag-Pt Alloys in Low-Temperature SOFCs
Authors: Huang Hong , Holme Tim P. , Prinz Fritz B.
Published: September 2007

Oxygen reduction reactions on Pt, Ag, and Pt-Ag alloys were investigated at temperatures between 300oC and 500oC with the help of electrochemical impedance spectroscopy. The rate-determining step in oxygen reduction reactions was found to depend on the choice of material as well as porosity and thickness. On 600nm dense Ag, dissociative adsorption/reduction of oxygen was dominant. On porous Pt charge transfer reaction in the vicinity of triple phase boundary is rate determining. Slow oxygen diffusion was rate dominant with 600nm dense Ag3Pt. I-V characterization was also performed at 350oC on fuel cells consisting of different metal cathodes. Silver-based alloys were found not suitable as cathodic catalysts for low temperature solid oxide fuel cells due to formation of silver oxide, in turn leading to a rapid decline in voltage with increasing current densities. Among the investigated metals, thin porous Pt was identified as the best cathode.
Integrated Precision Polysilicon Resistors
Authors: Towner Janet M. , Naughton John J. , Thomason Mike W.
Published: September 2007

Two problems were encountered in the manufacture of precision polysilicon resistors that related to resistance variations across the wafer. In our process, we use boron to counter dope the phosphorus rich n-polysilicon. The first problem encountered involved variation with a circular pattern; the highest resistances were in the center of the wafer. The characteristic pattern indicated the problem could relate to wafer charging during implant. Ultimately this problem was found not to relate to the implant. Good uniformity was obtained by moving the polysilicon anneal to a more innocuous location. A second problem was encountered following resolution of the first problem. Some wafers exhibited horizontal bands of constant resistance with the lowest values in the middle of the wafer. The problem was found to relate to photoresist outgassing and ion neutralization. This was resolved by restricting the process to an implanter with a large endstation, where emitted gases could be more effectively diluted.
Anion Radical of 3,5-bis(1,1-dimethylethyl)-4-oxo-2,5-Cyclohexadienylideneacetonitrile: Dimerization
Authors: ul Haque Inam , Khan Asim , Sadaf Shamaila
Published: September 2007

3,5-Bis(1,1-dimethylethyl)-4-oxo-2,5- cyclohexadienylideneacetonitrile, QM, is an electron acceptor. Simulation of cyclic voltammogram of 3,5-Bis(1,1- dimethylethyl)-4-oxo-2,5-cyclohexadienylideneacetonitrile, QM, in acetonitrile at platinum electrode was carried out, and a scheme was suggested to obtain the heterogeneous rate constants for electron transfer. The results of simulations based on two shareware programs are generally consistent with theoretical and experimental work.
Synthesis of Methyl Aziridine-2-Chloro-2-Carboxyletes through Electroreductive Cross Coupling of Methyl Trichloroacetate with Aromatic Imines
Authors: Nishiguchi Ikuzo , Kendrekar Pravinkumar S. , Maekawa Hirofumi
Published: September 2007

Electroreductive of aromatic imine derivatives (1) with methyl trichloroacetate (2) in N,N-dimethylacetamide (DMAc) containing Et4NBr as a supporting electrolyte using an undivided cell equipped with Zn-plates as the electrodes under constant current conditions brought about stereoselective cross coupling to give the corresponding methyl aziridine 2- carboxylates (3) in good to moderate yields.
Advanced Metrology for Porous Low-k Integration into Cu back-end Processes
Authors: Ryan Paul A. , Bytheway Richard , Gibson Gary , Koga Kazuhiro
Published: September 2007

Four porous ultra low-k spin-on dielectric materials from different manufacturers were characterized using X-ray reflectivity (XRR), grazing-incidence small angle X-ray scattering (GI-SAXS), transmission electron microscopy (TEM) and electrical leakage methods and their results are compared. It is shown that X-ray methods can rapidly, accurately and repeatably determine the thickness and density of the low-k film and can provide valuable insights into the pore structure, which may be able to help predict electrical leakage in the low- k material.
Enhanced Cracking Resistance of Plasma Deposited Low-k SiCOH Films with Nano Imbedded Layers Insertion
Authors: Nguyen Son V. , Liniger E. , Ida K. , Herbst B. , Malone K. , Klymko N. , Cohen S. , Simonyi E. , Dziobkowski C. , Lane S. , Grill A. , Restaino D. , Gates S. , Edelstein D. , Nogami T. , Ivers T.
Published: September 2007

With the simple insertion of imbedded nano layer during the deposition of plasma deposited porous low k SiCOH film, the cracking resistance of the hick ILD film can be improved significantly without changing modulus and hardness properties. The reduction in cracking will help to facilitate the implementation of thick ILD in Cu/Low-k ILD for advanced BEOL
Surface Treatment of Indium Tin Oxide (ITO) using Radio Frequency Atmospheric and Low Pressure Plasma for Organic Light Emitting Diodes (OLED)
Authors: Jung Mi-Hee , Choi Ho-Suk
Published: September 2007

We investigated the effect of the atmospheric pressure plasma (APP) and low pressure plasma (LPP) treatments on the performance of organic light emitting diodes (OLED). The increase of surface energy was mainly attributed to polar component and Lewis base interaction, independent of either APP or LPP treatments. O2 LPP-treated surface showed more uniform roughness than Ar/O2 APP-treated surface. All plasma treatments increased the amount of oxygen, which led to the improvement of work function, while decreasing the amount of carbon. All treatments except only Ar APP treatment decreased the amount of dopant-tin. O2 LPP-treated ITO showed the highest value of work function because of the efficient removal of carbon contamination, together with the improvement of In/Sn ratio, and the uniformity of surface roughness. Thus, the organic light-emitting diode fabricated on the surface of O2 LPP-treated ITO substrate exhibited superior brightness.
Sol-gel Synthesis and Characterization of La0.6Sr0.4CoO3 Nanoparticles, Nanotubes, and Thin Films
Authors: Wang Jin , Johnson Christopher , McGraw Adrienne , Wu Nianqiang Nick
Published: September 2007

Nanoparticles, nanotubes and thin films of polycrystalline La0.6Sr0.4CoO3 were synthesized by the sol-gel process. DTA, AFM, SEM/EDAX and X-ray diffraction were utilized to characterize the properties of the products. The nanoparticles were obtained from the precursor sol containing metal nitrates and citric acid. The nanotubes were derived from the same sol with the aid of anodic aluminum oxide template. The thin films were prepared by spin coating the sol containing metal nitrates, citric acid and ethylene glycol on Si (1 1 1) substrate, in which ethylene glycol was employed to enhance the affinity between the sol and the substrate. The perovskite phase was obtained by calcining corresponding precursor products at 650 ºC. The as-calcined nanoparticles were 50~100 nm in size. The as-calcined thin film showed uniform nano- porous morphology with the grain size of around 40 nm and the thickness of around 150 nm. The as-calcined nanotubes were around 100nm in diameter and up to several micrometers long.
Electrochemical Preparation of Alternate Pt-Fe Alloy Nanowires with AAO Templates
Authors: Yuan Ding S. , Hu Xiang , Chen Jun Z. , Yang C. T.
Published: September 2007

AAO templates have been prepared via a two-step anodic oxidization process. The templates possess the size of nanopores, the thickness of template and the density of nanopores is 35nm, 30μm and 6.3×1010 cm-2, respectively. Pt-Fe alloy nanowires have been fabricated via alternating current (AC) technique and characterized by TEM, EDS and vibrating sample magnetometer. The ascorbic acid results in Pt and Fe deposited alternately. Pt-Fe (31:69) alloy possesses larger Hc and higher remanence ratio along the nanowires. Thus, this kind of Pt-Fe alloy nanowires could have potential application as high-density perpendicular recording materials.
Lithium Oxalyldifluoroborate as a Salt for the Improved Electrolytes of Li-Ion Batteries
Authors: Zhang Sheng S.
Published: September 2007

This paper introduces lithium oxalyldifluoroborate (LiODFB) as a salt and an additive, respectively, for the improved electrolytes of Li-ion batteries. Due to its unique chemical structure consisting of the same molecular species of lithium bis(oxalato)borate (LiBOB) and lithium tetrafluoroborate (LiBF4), LiODFB has the combined advantages of LiBOB and LiBF4 salts. Compared with LiBOB, LiODFB has higher solubility in alkyl carbonate solvents and is able to provide the battery with much better rate capability and low temperature cycling performance. Compared with LiBF4, LiODFB is more powerful in facilitating the formation of solid electrolyte interface (SEI) on the surface of graphite anode and is able to offer better high temperature cycleability. It is shown that the Li-ion bat- tery with LiODFB electrolyte can be stably and safely operated in a wide temperature range. Meanwhile, LiODFB can be served as an electrolyte additive to stabilize the SEI. Other unique properties of the LiODFB electrolytes include: (1) the optimized ionic con-ductivity over a wide temperature range, (2) the ability to support reversible cycling of metallic Li on copper anode current collector, and (3) the ability to passivate aluminum cathode current collector.
Changes in the Mechanism of Lithium Extraction by Metal Substitution in High-Voltage Spinel Electrodes
Authors: Alcantara Ricardo , Lavela Pedro , Leon Bernardo , Perez Vicente Carlos , Tirado Jose L.
Published: September 2007

The ordered Li0.5Ni0.5Mn1.5O4 phase with P213 symmetry is formed during lithium extraction from the spinel in the 5-V region. For LiCoMnO4 and LiFe0.5Mn1.5O4 the existence of the ordered intermediate is not observed. The formation of the ordered phase is inhibited by the presence of iron as a second element replacing manganese, but is retained in the presence of titanium. In triple substituted systems with Ni and Fe (> 0.05) and Ti, V or Co, a single-phase extraction takes place. The origin of these divergences result from the presence of some iron in tetrahedral sites, which puts obstacles to lithium ordering and stabilizes the spinel structure. The changes in mechanism by the presence of iron improve capacity retention in the presence of Ti and Co, and decreases polarization in the presence of vanadium.
Electronic Conductivity, Lithium Diffusion and Particle Size Effect on the Rate Capability of Fd3m and P4332 LiMn1.5+xNi0.5-xO4
Authors: Kunduraci Muharrem , Amatucci G. G.
Published: September 2007

The electronic conductivity and lithium-ion diffusivity of cation ordered P4332 and disordered Fd3m phases of LiMn1.5+xNi0.5-xO4 were evaluated to identify the origin of the electrochemical disparity in the rate capabilities of two spinel phases. The physical measurements and electrochemical experiments performed under varying conditions revealed that the ordered phase, which was earlier found to be inferior to its disordered counterpart at high discharge rates, is both electronically (when Mn3+ - free) and ionically limited.
Transient Overgrowth of a Resistive Barrier Layer by Electrodeposited Metal in the Presence of Additives
Authors: Willis Matthew , Alkire R.
Published: September 2007

In this paper, a novel, high throughput experimental and theoretical technique was developed to extract additive influences on the dual-kinetic deposition of a metal onto a foreign substrate based on key transition points in chronopotentiometry curves. A finite difference (FD) 1-D growth mode simulation was developed to predict the overgrowth of an electrodeposited metal onto a resistive substrate in the presence of additives based on the experimental results. The simulations were employed to study thin film overgrowth on the wafer scale. Results indicated that the deposit profile was more uniform over a broader range of deposition rates as the rate on the coalesced deposit (ξCu) decreased. Other key parameters forpromoting thin film growth included a low coalescence thickness, high substrate conductivity, and an intermediate applied current.
Via Filling Electrodeposition by Using Periodic-Reverse Current
Authors: Kondo Kazuo N. , Nakamura Taichi , Mikami Daisuke , Okubo Toshikazu
Published: September 2007

The optimized electrodeposition condition of via filling was obtained with the potential measurement. This measurement corresponds well with via cross section. We adopted two step electrodeposition method. The first step is via filling by the periodical-reverse pulse current of Ion / Irev / Ioff= -20/ 40 / 0 [mA/cm2] and Ton / Trev / Toff = 200 / 10 / 200 [ms]. Thirty minutes periodical-reverse pulse current perfectly fills the via of 40μm in diameter and 25μm in depth. The second step is etching by the periodical-reverse pulse current of Ion / Irev / Ioff= 20/ -40 / 0 [mA/cm2] and Ton / Trev / Toff = 200 / 10 / 200 [ms], in order to etch the copper film. Nine minutes was required to etch. The via are perfectly filled and the uniform via surface of 6 to 7[μm] was obtained within 39 minutes.
Electroless Copper Deposition on Ruthenium for Damascene Interconnects
Authors: Chen Qingyun , Lin Xuan , Valvede C. , Paneccasio V. , Hurtubise R. , Ye P. , Kudrak E. , Abys J.
Published: September 2007

Nucleation and growth behavior of electroless copper on different Ru substrates, PVD Ru and CVD/ALD Ru, were investigated. Possibility of using electroless copper as seeding on Ru followed by ECP gapfill and as direct gapfilling for damascene interconnect applications was explored. Effect of Ru substrate microstructure on electroless copper grain orientation and texture was discussed.
Localized Gold Electrodeposition onto p-type Silicon surfaces
Authors: Santinacci Lionel , Djenizian Thierry , Etcheberry A. , Schmuki Patrik
Published: September 2007

In this paper, we report selective electrochemical gold deposition onto p-type Si (100) into nanoscratches produced through a thin oxide layer using an atomic force microscope. A detailed description of the substrate engraving process is presented. The influence of the main scratching parameters such as the normal applied force, the number of scans and the scanning velocity are investigated as well as the mechanical properties of the substrate. Gold deposition is carried out by cathodic steps for various durations. The electrodeposition mechanism is investigated by cyclic voltammetry. Reactivity enhancement at the scratched locations is studied by comparing the electrochemical behavior of intact and engraved surfaces using a microelectrochemical setup. Selective electrochemical gold deposition is achieved. Metallic patterns with a sub-500 nm lateral resolution are obtained demonstrating therefore the bearing potential of this patterning technique.
Li2RuO3 and LiFePO4: Towards a Low Impedance Composite Cathode
Authors: Stux Arnold M. , Swider-Lyons Karen
Published: September 2007

A blend of Li2RuO3 and carbon-coated LiFePO4 is examined as a low impedance cathode for high power lithium-ion microbatteries. A lithium metal cell with a composite positive electrode of LiFePO4/C and Li2RuO3 showed a greater specific capacity and specific energy at 1C discharge than at C/5. A specific capacity of 145 mAh/g was observed for the blend of 40% Li2RuO3 and 60% LiFePO4/C when discharged at C/5, whereas 160 mAh/g was observed for 1C discharge rate. Discharge rates greater than 1C showed progressively decreased specific capacities.
HQ Asymmetric Super Capacitor: Graphite-Li4Ti5O12/Ionic Liquid/Carbon
Authors: Zaghib K. , Charest Patrick , Guerfi Abdelbast , Dontigny Martin , Kinoshita Kim
Published: September 2007

Hybrid supercapacitor that contain high-surface-area carbon and metal oxide electrodes are attracting interest for use in electrochemical devices. Metal oxide electrodes containing Li4Ti5O12 in liquid electrolytes (ionic liquid or nonaqueous liquid) were investigated. A new procedure developed at Hydro Quebec produced Li4Ti5O12 powders with diameters in the range of 100 nm. At high-rate (1 minute) charge-discharge, the hybrid supercapacitor had an average voltage of about 2.21 V, with 85% nominal capacity. These hybrid supercapacitors also exhibited a very long cycle life of >20,000 cycles at high- rate charge-discharge. The results of this study demonstrate that the Li4Ti5O12-based electrochemical system has attractive characteristics for high-power application such as in portable devices and HEVs
Structure, magnetic and electrochemical properties of LiFe1.5P2O7 synthesized by sol-gel method
Authors: Ait-Salah Atmane , Ramana Chintalapalle V. , Gendron Francois , Morhange Jean Francois , Mauger Alain , Julien C.
Published: September 2007

We present the structural, magnetic and electrochemical properties of the pyrophosphate LiFe1.5P2O7 synthesized by sol- gel method. The structure was determined by X-ray diffraction, high-resolution transmission electron microscopy, Raman scattering, and magnetometry. Electrochemical properties of LiFe1.5P2O7 were carried out in lithium cells with LiPF6-EC- DEC electrolyte at 25 {degree sign}C.
A New Approach Toward Local Structure of Spinel Compounds Using Vibrational and Magnetic Properties
Authors: Kopec Monika , Dygas Jozef R. , Krok Franciszek , Gendron Francois , Mauger Alain , Julien C.
Published: September 2007

The Li1+xMn2-xO4 (0{less than or equal to}x{less than or equal to}⅓) spinel phases have been synthesised by wet-chemistry technique using metal acetates and succinic acid as polymeric agent. Precursors were decomposed at 400 {degree sign}C and heat-treated at 750 {degree sign}C. Additionally stoichiometric powders were heat-treated at 800 {degree sign}C. The physical properties of the synthesised products have been investigated by X-ray diffraction, Raman spectroscopy, electrical and magnetic measurements. The analysis of the intrinsic magnetic properties show that the magnetic interactions are Mn3+-O-Mn3+ interactions in a geometrically frustrated lattice, while the Mn4+-Mn4+ interactions are negligible, with the consequence that the paramagnetic Curie temperature vanishes in the limit x ≈⅓, where only Mn4+ ions remain. A consistent description of both the extrinsic and the intrinsic properties including former investigations of electron paramagnetic resonance has been achieved.
Synthesis, Structure and Electrochemical Properties of LiNi0.33Mn0.33Co0.33O2 Positive Electrode for Rechargeable Lithium Batteries
Authors: Abdel-Ghany Ashraf , Zaghib K. , Mauger Alain , Massot Michel , Gendron Francois , Ramana Chintalapalle V. , Julien C.
Published: September 2007

The layered LiNi0.33Mn0.33Co0.33O2 materials were prepared by wet chemical method using oxalic acid as a polymeric agent. The positive LiNi0.33Mn0.33Co0.33O2 powders were characterized by means of X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and magnetometry. Electrochemical features of LiNi0.33Mn0.33Co0.33O2 positive electrodes were investigated as a function of synthesis conditions, cutoff voltage limit, and C-rate discharge current. Electrochemical properties are discussed in relation with the local structure and morphology of the layered materials.
Cathodic Electrodeposition of Manganese Oxides for Electrochemical Supercapacitors
Authors: Wei Janice , Cheong Marco , Nagarajan Nandakumar , Zhitomirsky Igor
Published: September 2007

Manganese oxide films for electrochemical supercapacitors (ES) have been prepared by cathodic electrolytic and electrophoretic deposition. The cathodic reduction of KMnO4 solutions resulted in the formation of manganese oxide deposits. In another approach electrophoretic deposition (EPD) has been utilized for the deposition of manganese oxide nanoparticles prepared by a chemical precipitation method. The films exhibited pseudocapacitive behavior in a potential window of 0-1 V versus SCE in aqueous 0.5 M Na2SO4 and 0.5 M K2SO4 solutions. The deposition methods allowed the formation of porous films which exhibited a specific capacitance (SC) in the range of up to 240 F/g. The SC decreased with increasing scan rate. The films prepared by electrolytic deposition showed higher SC compared to the SC of EPD deposits.
Characterization of Activated Nanoporous Carbon as Electrical Double Layer Capacitor Electrode Materials
Authors: Janes Alar , Kurig Heisi , Lust Enn
Published: September 2007

Thermodynamical and electrochemical characteristics for the non-aqueous electrolyte | nanoporous carbide-derived carbon (CDC), activated carbon cloth (ACC) or commercial activated nanoporous carbon RP-20 (from Kuraray Chemical Co.) interface have been established by XRD, Raman spectroscopy, BET, cyclic voltammetry and electrochemical impedance spectroscopy. The gas adsorption measurements have been used for the obtaining the specific surface area, pore size distribution, nanopore volume and other characteristics, dependent on the nanoporous carbon used (nanopores are pores in the range of 2 nm and below - i.e. micropores according to IUPAC classification).
Redox Deposition of Nanoscale MnO2 on Ultraporous Carbon Nanoarchitectures: Correlation of MnO2 Deposition Time and Electrochemical Performance
Authors: Fischer Anne , Long Jeffrey W.
Published: September 2007

The redox reaction of aqueous permanganate with carbon nanofoam substrates at neutral solution pH produces nanoscale MnO2 deposits throughout the nanofoam structure. The MnO2 deposits become thicker with increasing deposition time (5 min to 20 h), with a corresponding enhancement in the electrode capacitance as the deposition progresses. The MnO2 capacitance enhancement is limited at high mass loadings during high rate operation, presumably due to the buildup of thicker MnO2 deposits on and within the carbon nanofoam structure.
Molecular Chemisorption at Electrocatalyst Surfaces. A Bibliography
Authors: Kar P , Cummins K , Baricuatro J. , Hossain M. , Li K , Soriaga M. P.
Published: September 2007

Presented here is a bibliography of empirical studies published in the past fifteen years on the molecular structure, chemical composition and catalytic reactivity of a wide cariety of compounds chemisorbed on iridium, palladium, platinum, rhodium and ruthenium surfaces. The references cited are limited to experimental work directly relevant to electrocatalysis and exclude publications on other aspects related to surface science in general; theoretical studies have likewise not been included. This bibliography may be considered as an update to two previously published compilations† that covered the literature in earlier years.
Manipulation of citrulline availability in humans
Authors: Rougé Carole , Des Robert Clotilde , Robins Alexander , Le Bacquer Olivier , Volteau Christelle , De La Cochetière Marie-France , Darmaun Dominique
Published: September 2007

To determine whether circulating citrulline can be manipulated in vivo in humans, and, if so, whether citrulline availability affects the levels of related amino acids, nitric oxide, urinary citrulline, and urea nitrogen, 10 healthy volunteers were studied on 3 separate days: 1) under baseline conditions; 2) after a 24-h treatment with phenylbutyrate (0.36 g·kg−1·day−1), a glutamine “trapping” agent; and 3) during oral l-citrulline supplementation (0.18 g·kg−1·day−1), in randomized order. Plasma, erythrocyte (RBC), and urinary citrulline concentrations were determined by gas chromatography-mass spectrometry at 3-h intervals between 1100 and 2000 on each study day. Regardless of treatment, RBC citrulline was lower than plasma citrulline, with an RBC-to-plasma ratio of 0.60 ± 0.04, and urinary citrulline excretion accounted for <1% of the citrulline load filtered by kidney. Phenylbutyrate induced an ∼7% drop in plasma glutamine ( P = 0.013), and 18 ± 14% ( P < 0.0001) and 19 ± 17% ( P < 0.01) declines in plasma and urine citrulline, respectively, with no alteration in RBC citrulline. Oral l-citrulline administration was associated with 1) a rise in plasma, urine, and RBC citrulline (39 ± 4 vs. 225 ± 44 μmol/l, 0.9 ± 0.3 vs. 6.2 ± 3.8 μmol/mmol creatinine, and 23 ± 1 vs. 52 ± 9 μmol/l, respectively); and 2) a doubling in plasma arginine level, without altering blood urea or urinary urea nitrogen excretion, and thus enhanced nitrogen balance. We conclude that 1) depletion of glutamine, the main precursor of citrulline, depletes plasma citrulline; 2) oral citrulline can be used to enhance systemic citrulline and arginine availability, because citrulline is bioavailable and very little citrulline is lost in urine; and 3) further studies are warranted to determine the mechanisms by which citrulline may enhance nitrogen balance in vivo in humans.
Effect of systemic B-type natriuretic peptide on cardiac vagal motoneuron activity
Authors: Toader E. , McAllen R. M. , Cividjian A. , Woods R. L. , Quintin L.
Published: September 2007

Intravenous B-type natriuretic peptide (BNP) enhances the bradycardia of reflexes from the heart, including the von Bezold-Jarisch reflex, but its site of action is unknown. The peptide is unlikely to penetrate the blood-brain barrier but could act on afferent or efferent reflex pathways. To investigate the latter, two types of experiment were performed on urethane-anesthetized (1.4 g/kg iv) rats. First, the activity was recorded extracellularly from single cardiac vagal motoneurons (CVMs) in the nucleus ambiguus. CVMs were identified by antidromic activation from the cardiac vagal branch and by their barosensitivity. Phenyl biguanide (PBG), injected via the right atrium in bolus doses of 1–5 μg to evoke the von Bezold-Jarisch reflex, caused a dose-related increase in CVM activity and bradycardia. BNP infusion (25 pmol·kg−1·min−1 iv) significantly enhanced both the CVM response to PBG ( n = 5 rats) and the reflex bradycardia, but the log-linear relation between those two responses over a range of PBG doses was unchanged by BNP. The reflex bradycardia was not enhanced in five matched time-control rats receiving only vehicle infusions. In five other rats the cervical vagi were cut and the peripheral right vagus was stimulated supramaximally at frequencies of 1–20 Hz. The bradycardic responses to these stimuli were unchanged before, during, and after BNP infusion. We conclude that systemic BNP in a moderate dose enhances the von Bezold-Jarisch reflex activation of CVM, in parallel with the enhanced reflex bradycardia. That enhancement is due entirely to an action before the vagal efferent arm of the reflex pathway.