bluuebunny/crossref_metadata_2025 huggingface dataset:
Fabrication and Characterization of Ultraviolet Light Emitting Diodes with Nanometer Scale Compositionally Inhomogeneous Active Regions
Authors: Sampath Anand V. , Reed Meredith , Chua Christoper , Garrett Gregory , Readinger Eric D. , Usikov Alexander , Kovalenkov Oleg , Shapovalova Lisa , Shen H , Dimtriev Vladimir , Johnson Noble , Wraback Michael
Published: September 2007

In this paper we report on the growth and fabrication of ultraviolet light emitting diodes that employ a novel AlGaN active region containing nanometer scale compositionally inhomogeneous (NCI) regions. These plasma-assisted molecular beam epitaxy grown NCI-AlGaN films exhibit enhanced photoluminescence intensity due to carrier localization and concentration in nanoscale regions of smaller bandgap that suppresses non-radiative recombination and improves radiative efficiency. We observe that the formation, density and size of these NCI regions are modified strongly by growth conditions. The emission wavelength of these alloys may be controllably tuned from 275 to 340 nm by varying growth conditions. Double heterostructure ultraviolet light emitting diodes were fabricated that emit at peak wavelengths of 310nm and 324 nm with output power of 0.11 mW and 0.42 mW for a 100 mA DC drive current. These results demonstrate the potential for NCI-AlGaN active regions to improve the efficiency of III-Nitride based ultraviolet emitters.
Time-Resolved Photoluminescence of Wideband Gap Semiconductor Devices
Authors: Garrett Gregory , Reed Meredith , Sampath Anand V. , Shen P. , Wraback Michael
Published: September 2007

The use of optical gating by frequency downconversion to study UV optoelectronic devices provides information on carrier recombination dynamics with sub-picosecond resolution. Measurement of active LEDs undergoing current injection and measurement of stimulated emission from UV laser cavities is demonstrated.
Reflection Anisotropy Study of ZnTe Around the E1 and E1+Δ1 Critical Points
Authors: Molina-Contreras J. R. , Villalobos-Piña Francisco Javier , Tejo-Vázquez Rodolfo
Published: September 2007

We report on a study of the RA experimental line shape for ZnTe near the E1 and E1+Δ1transition regions. The measured RA spectrum was analyzed using the effective medium theory, the dislocation-induced piezo-optic model, and compared with the calculated normal-incidence reflectance. Results suggest that a simple change of sign in the dislocation-induced piezo-optic model can explain one part of the measured RA spectrum within the studied transitions, and that the first energy derivatives of the measured RA and the calculated R spectra show a similar behavior. No derivative-like, ε-like or 1/ε-like line shapes are observed in the measured RA spectrum.
Simultaneously Enhancing Internal and Extraction Efficiencies of GaN-based Light Emitting Diodes Via Chemical-Wet-Etching Patterned-Sapphire-Substrate (CWE-PSS)
Authors: Lee Y.J. , Chiu C.H. , Kuo H. C. , Lu T.C. , Wang S.C. , Ng K.W. , Lau K.M. , Yang Z.P. , Chang S. P. , Lin S.Y.
Published: September 2007

We report a chemical-wet-etching patterned-sapphire-substrate (CWE-PSS) that simultaneously enhances internal quantum efficiency and light extraction efficiency of gallium nitride based light-emitting-diode (LED). According to transmission electron microscopy (TEM) images, the threading dislocations penetrating into active region was dramatically reduced in the CWE-PSS structure compared to the planar sapphire substrate, i.e. enhancement of internal quantum efficiency. And according to the measurement of angular dependent diffraction power, CWE-PSS also serves as a diffraction grating which diffracts guided light into escaping cones, further improving light extraction efficiency of LED device.
AlGaN/GaN HEMTs Fabricated on Selectively Grown Mesas on Si(111)
Authors: Bardwell J. , Haffouz Soufien , Tang Haipeng , Kochtane Amine , Lester Tim , Wang Rongzhu , Rolfe Stephen
Published: September 2007

AlGaN/GaN HEMT devices on selectively grown mesa structures on Si(111) have been grown and fabricated. A typical strain relief structure was grown over the entire 2" wafer. Subsequently, the epilayer was removed from most of the wafer surface by dry etching, leaving only the patterned mesas intact. Then, the wafer was returned to the growth chamber and the growth of the AlGaN/GaN heterostructure was completed. GaN does not nucleate on the Si(111) surface, thus the growth was highly selective, and moreover, due to the small size of the mesas, was crack-free. A five level mask set, consisting of mesa, ohmic, gate, passivation, and interconnect metal levels was used to complete the working devices. Devices with 0.8 µm gate length showed peak currents of 0.45 A/mm, and transconductance of 130 mS/mm. The devices were essentially free of current collapse and had fT of 9 GHz and fMAX of 22 GHz.
Effect of Al Concentrations on The Properties of ZnO:Al Films Prepared by E-beam Evaporation
Authors: Kim Dae-Hyun , Jeong Eun-Kyung , Kim In-Soo , Choi Se-Young
Published: September 2007

We investigated the effect of Al concentration on the properties of Al doped ZnO transparent electrode as a substitute for ITO. Al doped ZnO thin films were deposited with different Al concentrations on glass substrates by E-beam evaporation. Only (002) diffraction peak was detected from X-ray diffractometer (XRD), so we concluded that the thin films were highly c-axis-oriented perpendicular to the substrate. The SEM images showed that the films had faceted surface structure and atomic force microscopy (AFM) image revealed that root mean square roughness was below 200 Aå. The optical transmittance of the films with substrate glass was above 80% in the visible range and optical band gap energy of the films was above 3.3 eV. The lowest resistivity of 6.5×10-4 Ω•cm was achieved from the thin films prepared with 6 wt.% Al2O3 in the target.
In Situ Corrosion Studies:Tracing Interconnecting Threads
Authors: Isaacs Hugh S.
Published: September 2007

Highlights from corrosion investigations are described which trace a history starting with a non-standard impedance method and localized measurements using current density mapping. These approaches led to different avenues of research on stainless steel, carbon steels, and aluminum and associated techniques for measuring surface changes.
pH Mapping of Localized Corrosion in Confined Electrolytes by Total Internal Reflection Fluorescence Microscopy
Authors: Loete Florent , Vuillemin Bruno Vuillemin , Oltra Roland
Published: September 2007

A device for pH mapping derived from optical sensors similar to TIRFM (Total Internal Reflection Fluorescence Microscopy) has been developed for future possible applications in the field of localized corrosion. The basic principle of this sensor is based on the excitation of a fluorescent silica polymer film of nanometer dimensions, deposited by sol-gel method on a waveguiding layer. Using this sensor as a crevice former the pH changes have been recorded for a cavity machined in a Fe-17%Cr electrode for different sizes of gap.
Effect of the Metallurgical Parameters on the Relevant Electrochemical Criterion for Localized Corrosion Resistance of Stainless Steels
Authors: Baroux Bernard , Malki Brahim
Published: September 2007

The effects of different metallurgical factors related to the steel making process of stainless steels on their pitting corrosion resistance are investigated from the double point of view of the pitting stages and of the relevance of the electrochemical criteria currently used to compare industrial steels together in view of material selection. It is concluded that alloying elements, impurities (sulfur), cold working process and final annealing may act on all the pitting stages from pit nucleation to pit stabilization. Counting the metastable pitting transients is a relevant technique in most cases, but using pitting potential as a single criterion of pitting resistance can be misleading in the more complex situations.
Local Mechanical-Electrochemical Behaviour of Duplex Stainless Steels: a Novel Approach for Mapping Precursor Sites for Pitting Corrosion
Authors: Vignal Vincent , Delrue Olivier , Peultier Jerome , Oltra Roland
Published: September 2007

The influence of residual surface stresses generated by polishing on the pitting susceptibility of duplex stainless steels was studied by combining microelectrochemical measurements with thermal-mechanical simulation. It has been shown that the surface stress state was the driving force for pit initiation along the austenite/ferrite interface. The local stress gradient was the key-parameter in pit initiation and the local average stress was the parameter governing the transition from metastable to stable pitting.
Simplified Analysis of EIS for Conversion Coated Aluminum Undergoing Pitting
Authors: Kendig Martin W.
Published: September 2007

As part of the development of a simplified method for characterizing the effectiveness of conversion coatings and inhibitors for the corrosion protection of aluminum alloys in neutral aqueous environments, models for the electrochemical impedance of a surface undergoing heterogeneous attack have been considered. Based on the phenomenological results of these models a simplified analytical approach has been proposed and used to rapidly evaluate the efficacy of non-chromate conversion coatings for aluminum 2024-T3.
Degradation of the Mechanical Strength of Al Alloys by Electrochemically Introduced Hydrogen
Authors: Fujimoto Shinji , Kouno Takashi , Tsuji Tomohide , Haruna Takumi
Published: September 2007

The high strength Al alloys, 7N01, 6061 and 5083, were examined using slow strain rate testing in chloride-containing acid to neutral solutions under potentiostatic control. Large amounts of hydrogen absorption occurred at potentials above the breakdown potential. In this potential range, the mechanical strength of the alloys is degraded manly by severe general corrosion but hydrogen embrittlement may also occur. On the other hand, polarisation at more negative potentials where there is intense hydrogen evolution does not necessarily lead to a large amount of hydrogen entry except for the case of the alloy 5083, which suffered from hydrogen embrittlement induced by hydride formation around precipitates.
Following Corrosion-Driven Relocation of Electrically-Connected Copper on AA2024 using Electrogenerated Chemiluminescence (ECL) Imaging
Authors: McMurray Hamilton N. , Barrett Zak
Published: September 2007

A novel electrochemical technique is described, which is capable of imaging the distribution of 'electrically-connected' copper on the surface of alloys such as AA2024 and following the redistribution of copper which accompanies localized corrosion. Here, the term 'electrically-connected' signifies copper that is in electrical contact with both the substrate and overlying electrolyte and therefore capable of influencing substrate corrosion. The imaging process employs luminol (3- aminophthalhydrazide), which emits light through electrogenerated chemiluminescence (ECL) when anodically oxidized in weakly alkaline electrolyte. It also exploits the very large differences in ECL efficiency observable for different metals (copper is many orders of magnitude more efficient than aluminium in this regard).
Modeling of Metastable Pitting: Towards a Better Understanding of the Effect of Alloying Elements
Authors: Malki Brahim , Baroux Bernard
Published: September 2007

Modeling of pit chemistry in applied polarization mode is carried out using analytical calculations. The results lead to the formulation of critical conditions for pit stabilization. More detailed computing is performed to study pit stability behavior in terms of pit geometry and applied potential. The results fairly predict a transition pHT=f(log (σa.λ)) where λ = L2/r (L and r are respectively pit depth and mouth) is the geometrical factor, σa is the physical factor depending on the dissolution law. The consequences of these conditions are explored to throw light particularly on the role of alloying elements in pit stabilization. A key question as far as the durability of passive alloys is concerned.
A Hybrid Scanning Probe Technique for In Situ Imaging Surface Topography and Corrosion Potential of Localized Corrosions
Authors: Lin Chang-Jian , Li Yan , Zhuo Xiang-Dong
Published: September 2007

In this work, a scanning reference electrode technique (SRET) has been integrated with a scanning tunneling microscopy (STM), for in situ studies of localized corrosion of metals. The hybrid scanning system has been established to synchronously image the surface topography in nano scale and the electrochemical potential distribution in micro resolution at the same location through a Pt-Ir micro probe. Based on the design and fabrication of the various scanning micro probes, an in-situ correlative study of topography-reactivity for the localized corrosion has been achieved.
Examination of Corrosion Products and the Alloy Surface after Crevice Corrosion of Alloy C-22
Authors: Shan Xi , Payer Joe H.
Published: September 2007

The corrosion products and the metal surface within the crevice of alloy C-22 after crevice corrosion tests under potentiostatic anodic polarization in 100{degree sign}C 4M NaCl solution were investigated. After exposure, loose black corrosion products were found under the crevice formers, and green deposits were found around the edges of the crevice contacts. During the exposure, the color of the test solution changed from clear to light green. Surface analysis results showed that the solid corrosion products in the crevice were rich in O, enriched in Mo and W, and depleted in Ni and Cr. Solution analyses showed that Ni was the main element dissolved into the solution during the exposure. Surface analysis at sites of varying corrosion penetrations indicated that a 2-8 nm thick chromium oxide rich barrier film was formed on the alloy surface, and the alloy dissolution occurred by a uniform, non- selective dissolution.
Effects of Sliding Wear at Various Loading Conditions on the Local Mechanical-Electrochemical Behaviour of Duplex Stainless Steels
Authors: Krawiec Halina , Vignal Vincent , Ponthiaux Pierre , Wenger Francois
Published: September 2007

The present paper aims at demonstrating the potential of the electrochemical microcell technique, the scanning vibrating electrode technique and local Auger for determining the influence of the surface chemical composition and surface defects on the electrochemical behaviour of each phase of duplex stainless steels in and out of the wear track.
Anodic Oxide Nanotubes on Ti Alloys
Authors: Tsuchiya Hiroaki , Macak Jan , Ghicov Andrei , Schmuki P.
Published: September 2007

The present paper reports the formation of self-organized nanotube oxide layers on Ti alloys such as Ti-6Al-4V, Ti-6Al- 7Nb and Ti-29Nb-13Ta-4.6Zr by anodization in 1M (NH4)2SO4 electrolyte containing 0.5 wt.% NH4F. Resulting morphologies strongly depend on the alloys used. On the binary a + b type Ti alloys, inhomogeneous nanotube formation takes place. Especially, on Ti-6Al-4V, the arrays of nanotubes with a diameter of 100 nm are formed on a phase region while the selective dissolution of b phase occurs, leading an inhomogeneous oxide nanotube layer. On the single b phase Ti- 29Nb-13Ta-4.6Zr, on the other hand, nanotubes are homogeneously formed on the entire surface. Remarkable is the nanotube layer consists of tubes with two distinctly different diameters.
Localized Corrosion of Magnesium in Chloride Containing Electrolyte Studied by a Scanning Vibrating Electrode Technique
Authors: Williams Geraint , McMurray Hamilton N.
Published: September 2007

An in-situ Scanning Vibrating Electrode Technique (SVET) is used to investigate localized corrosion occurring on unpolarised magnesium (Mg) samples immersed in aqueous sodium chloride solutions at concentrations of {greater than or equal to} 0.5% w/v. Localized corrosion of Mg takes the form of circular, dark regions which expand radially at a constant rate with respect to time and evolve hydrogen vigorously. These corrosion features are shown to consist of a strongly cathodically active centre surrounded by a 0.5 mm wide anodic ring. The uncorroded, film-covered Mg surface is largely electrochemically inert and plays no part in the localized corrosion process. The observations are consistent with a mechanism involving cathodic H2 evolution on the dark, film-free region which is galvanically coupled with anodic attack of the intact Mg surface. Enrichment in noble iron-containing impurity phases is thought to lead to cathodic activation of the dark, corroded surface.
Oxygen Electro-Reduction on C22 and C276 Nickel Metal Alloy
Authors: Rogers Stephen P. , Gervasio Dominic F. , Payer Joe H.
Published: September 2007

The C22 and C276 alloy metal surfaces were characterized for eletrochemical activity in alkaline aqueous media in the presence and absence of oxygen and at 30{degree sign}C. The metal was studied by electrochemical impedance spectroscopy (EIS), voltammetry with still electrode and a specialized rotating ring-disk electrode (RRDE) technique, the cyclic potential ring measurement (CPRM) method. The application of the CPRM method to the study of oxygen reduction on C22 and C276 showed strong evidence for a predominantly series 2 step, 2 electron oxygen reduction pathway, where kinetic rate constants k2 (evaluated at -0.7V versus the saturated calomel electrode) and k3 (evaluated at -1.2V) were estimated at 30 {degree sign}C to be 0.001 cm/s and 0.193 cm/s respectively for C22 and 0.013 cm/s and 0.232 cm/s respectively for C276.
The Influence of Irradiated Defect Structures on the Corrosion Behaviour of Nickel
Authors: von Trzebiatowski Oliver , Suter Thomas , Virtanen Sannakaisa
Published: September 2007

The focus of the present study is to evaluate the influence of different material structures on the corrosion behavior on high purity Nickel (99.999%). Four different structural states have been investigated in chloride containing solutions. Highly defected structures were obtained by irradiation of a single crystal with Ni+-ions with 7.5 MeV fluency beam. The behavior of grain boundary defects of sputtered nanocrystalline films (grain size ~ 50 nm) were compared with the behavior of a single crystal [100]. Electrochemical polarization curves showed that the different structural defects led to different passive current densities. Furthermore, microelectrochemical measurements revealed that chemical defects get activated at lower potentials than structural defects of grain boundaries and irradiation sites.
The Nature and Thiknesses of Passive Films on Interface Cu/ NaOH+Alanine
Authors: Kaluzhina Svetlana A. , Orlova Eugenia , Andreeva Nina
Published: September 2007

Thicknesses of films formed on the copper in alkaline solution in the presence of alanine are studied by ellipsometric method. It was found that small additives of β-alanine (10-4-10-3 mol/l) cause additional stabilization of copper passivity due to an increase in the film thickness. The adsorption kinetics of α- and β-alanine is studied. It is shown experimentally that β-alanine adsorbs on copper according to the Frumkin isotherm. By contrast, no definite type isotherm can be obtained for α-alanine due to its higher activity and ability to form soluble complexes with copper ions.
Corrosion of the Braze Affected Zone in Stainless Steel
Authors: Jeffcoate Carol , Pohlman Matthew
Published: September 2007

The corrosion of 347 stainless steel under a BNi3 braze alloy layer is investigated in DI water and borate buffer solution. Samples immersed in borate buffer solution did not show signs of corrosion. When corrosion occurred in samples immersed in DI water the corrosion was limited to the braze affected zone with little or no penetration into the stainless steel substrate. The effect of initiating corrosion in DI water then changing the solution to borate buffer was studied along with the effect of secondary braze cycles.
The Effect of Magnesium Additions on the Microstructure and Cut Edge Corrosion Resistance of Zinc Aluminum Alloy Galvanized Steel
Authors: Elvins Jon , Spittle John A. , Worsley David A.
Published: September 2007

The magnesium levels were varied from 0.0 to 0.05% in 20μm thick 4.5%Al/Zn galvanized coatings applied to 0.7mm gauge steel under continuous galvanizing conditions. These additions increased the total volume fraction of primary zinc phase (from 6 to 22%) and the number of primary zinc dendrites (from 1500 to 3250 mm-2) as a result of the depression of the eutectic temperature. These changes result in increasing cut edge corrosion on the exposed edges of materials embedded in resin to simulate organically coated steels. There is a systematic increase in zinc loss measured using a scanning vibrating electrode technique from 80 to 185 μg in 24 hours exposure to 5% NaCl. This increase in zinc loss results from an increase in active anode numbers (from 600 to 1700 m-1 cut edge) and from an increase in the number of long lived anodes resulting from the corrosion of large numbers of closely spaced dendrites.
Localized Corrosion of Chromium Coated Steel
Authors: Zhang Xiaolong , Beentjes Peter , Mol J. M. , Terryn Herman , de Wit J.H.W.
Published: September 2007

The corrosion behaviour of Cr-coated steel with and without uniaxial deformation was investigated by polarization and scanning vibrating electrode technique (SVET). The Cr coating on low carbon steel is in two different thicknesses, 0.01 and 1.06 micrometers. The chromium-coated steel was elongated up to 25% strain. The results show that the Cr-coated steel has larger corrosion resistance than the uncoated steel. The corrosion resistance increases with the thickness of the chromium coating. The SVET results show that pitting does not initiate at all defects at the same time. The pitting process is unstable. After a pit is covered by corrosion product a new anodic site may start to be active. The uniaxial deformation results in more defects in the coatings and decreases the corrosion resistance of the Cr-coated steel in an environment containing chloride.
Electrochemical Behavior of AF1410 High-Strength Secondary Hardening Steel with/without Cd plating
Authors: Yoon Yuhchae , Hansen Douglas C.
Published: September 2007

The electrochemical behavior of a high-strength secondary hardening steel, AF1410, has been investigated with and without a cadmium-plate coating. During anodic polarization, the anodic behavior of AF1410 was shown to be slightly dependent on the manufacturing process. AF1410 showed no indication of localized corrosion in the chloride solution, however evidence of uniform corrosion was observed after polarization measurements. Cadmium plated AF1410 exhibits an active/passive transition behavior and exhibited no significant galvanic coupling effect with the cadmium plate coating.
Methanol Oxidation on PtRu/C Electrocatalysts Prepared by a Microemulsion Method
Authors: Godoi Denis R.M. , Perez Joelma , Villullas Hebe M.
Published: September 2007

PtRu/C nanocatalysts were prepared by a microemulsion method using different values of water/surfactant molar ratio in order to get different particle sizes. Crystallite sizes and structural properties were determined by X-ray diffraction. Particle size and distribution were characterized by transmission electron microscopy and average composition was determined by energy dispersive X-ray analysis. Differential scanning calorimetry measurements indicated the presence of oxides in the as-prepared catalysts. The general electrochemical behavior was evaluated by cyclic voltammetry in 0.5 M sulfuric acid and the electrocatalytic activity towards the oxidation of methanol was studied in 0.5 M methanol acid solutions by potential sweeps and chronoamperometry.
The Impact of Oxygen Vacancies on the Oxygen Electrode Reaction on Anodic Oxide Films on Titanium
Authors: Roh Bumwook , Macdonald Digby D.
Published: September 2007

The impact of oxygen vacancies on the oxygen electrode reaction has been investigated on anodic titanium oxide (n- type semi-conductor). The anodic oxide films of various oxygen vacancy concentrations at constant film thickness were used as substrates for ascertaining relationships between the oxygen electrode reactions rates and donor (oxygen vacancy) density. The data were analyzed in terms of a model that delineates the roles played by oxygen vacancies in the bulk and at the surface. The results suggest that oxygen vacancies are involved catalytically in the oxygen electrode reaction. Possible mechanisms are postulated to account for the catalytic involvement of the vacancies.
Anodic Reactions of Borohydride in Sodium Hydroxide Solutions
Authors: Santos Diogo M. , Sequeira Cesar A.
Published: September 2007

Borohydrides present interesting options for electrochemical power generation acting either as hydrogen sources or anodic fuels for direct borohydride fuel cells and batteries. Though there have been several papers concerning electrochemical determination of relevant thermodynamic and kinetic parameters to the borohydride system, there are a number of basic aspects that have not been yet systematically studied. This paper reports chronopotentiometric studies of the electrooxidation of sodium borohydride at a gold sphere electrode in 2 M NaOH solutions, at temperatures ranging from 25 to 65 ºC. Gold displayed a rather good borohydride oxidation activity, and the overall oxidation process was shown to be irreversible involving a number of electrons very close to the theoretically expected value of 8. The results suggested that the rate-determining step is an irreversible, diffusion controlled, one-electron oxidation step, for which the transfer coefficients were calculated.
Thermal Oxide Grown on High Index Silicon Wafers
Authors: Rodríguez Ramiro Rogelio , Calleja Arriaga Wilfrido , De la Hidalga Wade Francisco Javier , Rosales Pedro , Torres Alfonso , Kendall Don L.
Published: September 2007

We characterized the oxide thickness of MOS capacitors fabricated on the high index silicon surfaces (1 1 4) and (5 5 12). The low index silicon wafers (0 0 1), (1 1 1), and (1 1 0) were used as a reference. Four fabrication processes were conducted, two with polysilicon gate (600Aå oxide thickness), and two using aluminum gate (600Aå and 150 Aå oxide thickness). Our results show that the oxide thickness increases as the surface goes from (0 0 1) to (1 1 1).
Loading Effects in the Selective Epitaxial Growth of n-Type Doped SiGe-Structures with LPCVD
Authors: Schindler Markus W. , Senftleben Oliver , Eisele Ignaz , Taylor William
Published: September 2007

In the last years, there was growing interest in the selective growth of strained SiGe-structures with n-type doping for source/drain engineering in NMOS. Phosphine (PH3) and arsine (AsH3) were under investigation as dopants (1,2). Howewer, data on homogeneity over the patterned wafer due to the mask layout (loading effects) are still lacking. We investigate selective epi with a dichlorosilane(DCS)-germane(GeH4)-PH3/AsH3- chemistry. The layers were deposited in an Applied Materials Centura Epi system and the characterization was done by SIMS, SEM, Spectral Ellipsometry, mechanical stylus profiling and 4-pt- probing.
Predicting Charge-Times of Internal Cardioverter Defibrillators
Authors: Gomadam Parthasarathy M. , Brown Jason , Scott Erik , Schmidt Craig
Published: September 2007

A novel method of validation of the mathematical model for batteries that power Medtronic's Implantable Cardioverter Defibrillators (ICDs) is presented. In a conventional approach used in the past, the model has been validated against data collected in controlled laboratory conditions. To supplement this approach, we now validate the model against ICD performance data reported from devices used in the field for periods ranging from about five to seven years. The key model output is ICD charge time - the time required to charge a high voltage capacitor in preparation to deliver shock to the heart. This validation is carried out for five of Medtronic's ICD designs and very close agreement is obtained between model predictions and field data.
Electrochemical Studies of Rose Bengal Using the Electrochemical Quartz Crystal Microbalance
Authors: Andrieux Fabrice P. , Boxall Colin
Published: September 2007

We present the results of an Electrochemical Quartz Crystal Microbalance study of the dark electrochemical behavior of rose bengal on gold piezoelectrodes in phosphate buffer at pH=7. Five oxidation and two reduction peaks were identified. The first oxidation process (Epox1=0.52V) is attributed to the formation of a Charge Transfer Complex (CTC) of rose bengal. The second process (Epox2=0.76V) is due to the partial breakdown of that CTC. The third process (Epox3=1.12V) is the electrochemical formation of a rose bengal polymer. Peak four (Epox4=1.24V) is due to the electrochemistry of the underlying gold surface, whilst peak five (Epox5=1.45V) is attributed to a process that facilitates trans-passive polymerization. The first reduction peak (Epred1=0.42V) is due to gold oxide stripping and the second (Epred2=0.36V) is the reduction of residual charge transfer complex formed in the first oxidation process.
Electrochemistry in Water Treatment
Authors: Becker Henry , Cohen Jon
Published: September 2007

Electrolytically driven formation of slow-to-precipitate insoluble salts such as calcium carbonate from meta-stabile, supersaturated solution may be employed to control deposit formation on heat exchange and other surfaces in practical systems such as industrial process water and evaporative cooling water loops. Cathodic fouling due presence of dissolved calcium salts has proven historically troublesome in metal plating and water electrolysis operations. It is perhaps somewhat ironic that this classical nuisance points to a mechanism that may be employed to control troublesome deposition throughout large real-world recirculating water systems and effectively establish a new strategy of water treatment with implications of environmental and economic benefit.
Electroplated Fe-Ni-Co for Use as O2 Evolving Anodes in Water Splitting
Authors: Boxley Chett J. , Steppan James , Bhavaraju Sai , Balagopal Shekar
Published: September 2007

Ceramatec has developed a novel, tailorable process for electroplating Fe-Ni-Co for use as water-splitting anodes or cathodes in an industrial electrolysis application. This paper focuses on the use of these materials as anodes in our NaSICON electrolysis cell. These materials were developed as alternative anodes to replace expensive Pt-based anode materials currently in use. Our electroplated anode materials offer several advantages over Pt including: lower cost, significantly lower operating voltage, and low corrosion rate. Ceramatec tailored our electrodeposited Fe-Ni-Co anodes for long-term performance in an electrolyte that simulated low- level radioactive waste. Our Fe-Ni-Co electrodes routinely performed well for over 1500 hours in this stimulant with a 1 V reduction in the cell operating voltage.
Transient Multi-Scale Modelling of Ageing Mechanisms in a Polymer Electrolyte Fuel Cell: An Irreversible Thermodynamics Approach
Authors: Franco Alejandro A.
Published: September 2007

In this paper we discuss a multi-scale mechanistic model of the electrochemical aging processes in a PEFC, recently proposed by us. At the present state, this model describes in particular the cathodic oxidation/dissolution of platinum and the carbon-supported platinum electrochemical ripening. These mechanisms are coupled with a novel non-equilibrium thermodynamics description of the cathodic electrochemical double layer, including the H+ and Pt2+ transports in the ionomer diffuse layer, as well as the detailed ORR and water dipoles adsorption in the compact layer. This continuous interfacial model is coupled to a continuous micro-scale model of the oxygen transport through the impregnated Nafion®/water layer, and is designed to be coupled with a continuous micro- scale model of the electrons, H+ and Pt2+ transports through the MEA thickness. The model allows analysing the sensitivity of the membrane/cathode response to the operating conditions, to the platinum/Nafion® loading and to the temporal evolution of the electrochemical activity from ageing mechanisms.
In-Situ Formation of Ag Capping Layer in Copper Chemical Mechanical Polishing
Authors: Kang Mincheol , Cho Sung Ki , Kim Jae Jeong
Published: September 2007

In the metallization process, the top surface of Cu exposed after CMP and exposure Cu is oxidized easily. Also, the additional Cu loss, known as dishing, occurs during over- polishing time. The oxidation and the loss of Cu resulted in the increase of resistivity. In order to improve resistance of Cu against oxidation and restore Cu line against dishing, Ag layer was formed by a displacement reaction during Cu CMP.
Synthesis of Nanoporous Gold Structures via Dealloying of Electroplated Au-Ni Alloy Films
Authors: Rouya Eric , Reed Michael L. , Kelly Robert G. , Bart-Smith Hilary , Begley Matthew , Zangari Giovanni
Published: September 2007

We studied the synthesis of nanoporous gold (NPG) films using electrodeposited Au-Ni as a precursor for dealloying. Potentiostatic dealloying of amorphous Au-Ni (Ni 65, 77, and 85at%) films at 0.7VSCE in 10mM H2SO4, resulted in the formation of nanoporous structures with average pore diameter increasing with Ni content from 69 to 107 nm. Alloy films with high Ni content are more susceptible to surface cracking due to large internal stresses. Potentiostatic dealloying of amorphous Au-Ni 73at% at 1.0V, 1.3V, and 1.5VSCE in 10mM H2SO4 yielded NPG structures with an average pore size which decreased with increasing applied voltage, from 57nm to 36nm. At higher anodic potentials, surface cracks become more apparent. Finally, the NPG structure could be tuned also by potentiostatic dealloying of partially crystallized Au-Ni 73at% at 0.7VSCE in 10mM H2SO4. The average pore size measured about 9nm, much smaller than those observed in dealloyed amorphous Au-Ni films.
Nafion/Prussian Yellow/ITO Multilayer Electrodes
Authors: Vicente Francisco , Sanmatías Ana , Giménez-Romero David , Gregori Juan , García José Juan
Published: September 2007

The reversible electrochemical oxidation of Prussian Blue to Prussian Yellow films is analysed from CV and EIS experiments. The electrochemical quartz microbalance gives also relevant information on the participation of ions in this process. Due to the cation selectivity of Nafion®, this ionomeric material has been deposited on PB films with the aim of elucidate the role of the anions and cations in the PB PY process. However, their respective participation depends on the crystalline degree and on the more or less soluble character of the Prussian Blue deposit. Crystalline and soluble evolves to whit the participation of the potassium as is showed from thermodynamic and instantaneous F(dm/dQ) measurements, whichever the anion participation is put in evidence if the Prussian film not reaches this structure.
Wetting Phenomenon in Nanoporous Gold Films
Authors: Seker Erkin , Tauer Tania , Zhu Jianzhong , Begley Matthew , Bart-Smith Hilary , Zangari Giovanni , Kelly Robert G. , Utz Marcel , Reed Michael L.
Published: September 2007

We have fabricated nanoporous gold (np-Au) films on silicon wafers by dealloying films formed by simultaneous sputter deposition of gold and silver. We report an interesting wetting phenomenon observed after placing a droplet of liquid on the np-Au film surface. As a droplet was dispensed onto the surface, wetting equilibrium was quickly reached and a wetting halo appeared with its perimeter equidistant from the perimeter of the droplet. Non-porous gold control samples did not display such behavior. This phenomenon was systematically studied by dispensing liquid droplets with different surface tensions and then measuring the width of the wetting halo. It was observed that halo width increased with surface tension. Experiments were extended to observe the effects of film thickness and porosity on the halo width. The width increased as film thickness increased. The relationship between the width and porosity was inconclusive due to large data scatter.
Investigating Porosity and Stress Evolution in Nanoporous Gold Films by Timed Thermal Treatment
Authors: Seker Erkin , Begley Matthew , Bart-Smith Hilary , Zangari Giovanni , Kelly Robert G. , Reed Michael L.
Published: September 2007

The stress evolution in nanoporous gold (np-Au) films and the influence of annealing temperature and duration was studied. Pore morphology was controlled by simply annealing the np-Au films. To study the relationship between porosity and stress evolution, np-Au films were fabricated on silicon wafers and the porosity was varied by thermal annealing at temperatures 200, 300, and 400{degree sign}C with durations of 2.5, 10, and 20 minutes. Analysis of porosity (via digital image processing of scanning electron microscope images) revealed that the average pore radii of samples increased non-monotonically with the annealing temperature and reached a steady-state value with time. Wafer curvature tests showed that the tensile residual stress in films increased with temperature, and leveled off with time (except for 400{degree sign}C, where it increased). While thicknesses of the np-Au films remained relatively unchanged for 200 and 300{degree sign}C cases, it decreased for 400{degree sign}C.
An Overview on Stabilized Lithium Metal Powder (SLMP), an Enabling Material for a New Generation of Li-Ion Batteries
Authors: Fitch Brian B. , Yakovleva Marina , Li Yangxing , Plitz Irene , Skrzypczak Adam , Badway Fadwa , Amatucci G. G. , Gao Yuan
Published: September 2007

The current Li-ion battery technology has reached its maturity and incremental improvements in energy density can not meet the increasing demand for more energy and power for portable electronic applications. Stabilized Lithium Metal Powder (SLMPTM) is an enabling material and technology that creates opportunities for more choices of active materials to be used in Li-ion batteries resulting in systems with improved performance in energy, safety and possibly cost. In this work we have discussed the initial results for SLMP stability in selected solvents. Material has been incorporated into Li-ion cells and results indicate that SLMP could be used as an independent source of lithium. Examples of using SLMP to improve the first cycle efficiency in silicon composite material and of Li-ion cell built with non-lithium providing cathode, such as the first Li-ion battery fabricated with a metal fluoride, are discussed. Approaches for synthesis of tin and silicon nanocomposites are presented.
Detrimental Surface Films on Electrode Materials: Investigation and Inhibition
Authors: Lucht Brett L. , Li Wentao , Xiao Ang
Published: September 2007

An investigation of the effect of various thermal stabilizing additives on thermally abused lithium-ion batteries was conducted. Vinylene Carbonate (VC) and Dimethyl Acetamide (DMAc) were found to diminish the effects of thermal abuse.
Electrolytes for Low Temperature Operations of Li-Ion Batteries
Authors: Jow R. , Zhang Sheng S. , Xu Kang , Allen Jan
Published: September 2007

The factors that limit the low temperature performance of Li- ion batteries were examined using an impedance analysis technique. The charge transfer resistance, Rct, obtained by this technique was increased with decreasing temperature following an Arrhenius relationship and it was the predominant resistance at low temperatures. The limiting step in the charge transfer process was discussed by comparing the activation energy of the charge transfer process and the activation energy obtained at a model interface designed by Abe et al. We also explored some electrolyte systems containing ester/carbonate solvent mixtures and/or LiBF4 salt. Lower Rct and activation energy were obtained for MCMB electrode in these electrolytes. Improved low temperature cell performance was also obtained for cells using these electrolytes.
Lithium-Conducting Ionic Melt Electrolytes from Polyether-Functionalized Fluorosulfonimide Anions
Authors: Creager Stephen , Hallac Boutros B. , Geiculescu Olt , Rajagopal Rama , DesMarteau Darryl D.
Published: September 2007

Ionic melt electrolytes consisting of lithium salts of fluorosulfonamide and fluorosulfonate anions covalently attached to oligomeric polyether chains were synthesized and characterized with respect to structure and ion transport characteristics. Conductivities are high relative to true polymer electrolytes. Galvanostatic DC polarization studies suggest that salt concentration polarization does not occur in the ionic melt electrolytes, whereas it does occur in otherwise similar electrolytes consisting of binary lithium salts dissolved in a liquid oligomeric polyether solvent.
A Study on Surface Treatment of Layered LiNi1/3Mn1/3Co1/3O2 Materials in Lithium Secondary Batteries
Authors: Kim Hyun Soo , Kong Mingzhe , Kim Ke-Tack , Kim Woo-Seong
Published: September 2007

Surface of LiNi1/3Mn1/3Co1/3O2 was coated with amorphous carbon to enhance the conductivity of the material. Electrochemical studies were performed by assembling 2032 coin cells with lithium metal as an anode. The carbon was coated irregularly on the surface of the material. The carbon-coated LiNi1/3Mn1/3Co1/3O2 cathode material showed the improved rate capability, thermal stability and cycle performance.
Electrochemical Features of LiNiyMnyCozO2 Cathodes for Li-ion batteries
Authors: Abdel-Ghany Ashraf , Zaghib K. , Mauger Alain , Gendron Francois , Eid Ahmed , Abbas H , Hashem Ahmed , Ramana Chintalapalle V. , Julien C.
Published: September 2007

A series of LiNiyMnyCozO2 layered materials was synthesized by chimie douce and investigated as positive electrodes in rechargeable lithium batteries. Electrochemical performance of LiNiyMnyCozO2 oxides is tested cell using non-aqueous 1M LiPF6 dissolved in EC-DEC. Charge-discharge profiles are investigated as a function of the rate capability and the voltage window. A relation is found between the gravimetric capacity and the cation disorder of the positive electrode as indicated by structural analysis. A quite fast lithium extraction attributed to the larger interslab space has been observed in the cobalt-rich oxides.
Recent Developments in Transmission Electron Microscopy Techniques to the Characterization of Cycled Li-Ion Electrode Materials
Authors: Dupont Loic , Laffont Lydia , Grugeon Sylvie , Laruelle Stephane , Bodenez Vincent , Tarascon Jean-Marie
Published: September 2007

Battery performance depends on many factors amongst which the selection of the appropriate electrode material and the control of the electrode/electrolyte interface upon cycling. In order to address these issues, electrochemists have to design new electrode materials, and 'enter the private life' of a battery. Transmission Electron Microscopy (TEM) is a powerful tool to help scientists to characterize each part of the device. Recent developments in TEM techniques have been proposed and developed, through the Alistore Electron Microscopy platform (AEMP), to allow the observation of Li-ion air sensitive electrode materials. Our team is now going one step further by using High Resolution Electron Energy Loss Spectroscopy (HREELS) and nanoprobe EDS as well as other TEM techniques exhibiting the advantage of high lateral resolution for chemical analysis and for structural determination (by means of electron diffraction and high-resolution imaging). The AEMP holds at the same time the equipment and the skills to run such experiments
Effect of Catalyst on the Performance of Rechargeable Lithium/Air Batteries.
Authors: Debart Aurelie , Bao Jianli , Armstrong Graham , Bruce Peter G.
Published: September 2007

Rechargeable lithium batteries are now a major technology, driven by their superior energy density compared with alternative rechargeable batteries. There is much interest in increasing further the energy density. This is limited by the positive electrode, LiCoO2, which can cycle only around 0.5 Li per formula unit. Intensive research world-wide on new intercalation cathodes will increase the amount of Li that may be stored, but only by a factor of 2. Replacing the intercalation cathode with an O2 electrode could raise the capacity 5-10-fold. Here we explore the influence of the catalyst could have on the performance of a non-aqueous O2 electrode on a Li/O2 cell. Of the catalysts studied, the highest capacity retentions were observed with Fe3O4, CuO and CoFe2O4 (6.67% per cycle). Co3O4 gives the best compromise between initial capacity (2000mAhg-1) and capacity retention (6.5% per cycle), as well as the lowest charging voltage 4V.
Cathode Structure/Property Relationships: Electrochemistry and Mechanics
Authors: Babinec Susan J. , Tang Houxiang , Meyers Greg , Stajdl Jeremy
Published: September 2007

The electrochemical responses of battery electroactive materials are evaluated with formulations which yield porous electrodes. In this study we detail the effects of the choice of binder, homopolymer PVDF and its copolymers, and its loading level on the electrochemical performance of LiCoO2 cathodes, coupling the analysis to electrode porosity. Electrode mechanical properties are also examined and correlated with the electrochemical responses. We establish a fundamental trade-off between mechanical durability and electrochemical performance based in the need for complex porous microstructures to provide Li+ transport.
The Study of Electronically Conducting Polymers with Highly Reversible p- & n-Doping
Authors: Levi Mikhael D. , Aurbach Doron
Published: September 2007

Poly[3-(3,4,5)-trifluorophenyl]thiophene (PTFPT) and poly[(2,7- fluoren-9-one)-alt-(5,5'-(3,3'-di-n-octyl-2,2'bithiophene))] (PFDO BT-HH, HH=head-to-head) were used to compare the relative stability of their electrochemical p- and n-doping. Both polymers were expected to exhibit an optimized π-electron density in the polymeric backbone of polythiophene either by attaching a pendant (redox-inactive) electron-withdrawing group in the 3-position of the heterocyclic monomer, or by obtaining a co-monomer containing π-conjugated bithiophene and a redox- active subunit. It is shown that PTFPT is sensitive to over- reduction at high cathodic polarizations whereas PFDOBT-HH, in which n-doping occurs in two steps, is much more stable with respect to over-reduction. This is explained by the fact that bithiophene and fluoren-9-one subunits in PFDOBT-HH are conjugated, and hence, the injected negative charge is distributed on both subunits, thus stabilizing the doped polymeric structure.
Liquid Cooling System for Advanced Microelectronics
Authors: Datta Madhav , Lin Eric , Choi Hae-Won. , McMaster Mark , Brewer Rick , Werner Doug , Hom James , Upadhya Girish , Gopalakrishnan Sudhakar , Rebarber Fred
Published: September 2007

Heat removal from advanced microelectronic devices is becoming a major packaging challenge. Thermal management solutions such as microchannel liquid cooling are now becoming commercially available. The use of a liquid cooling system is attractive because of higher heat transfer coefficients or lower thermal resistance as compared to traditional heat pipe or heat sink solutions. In this paper we present a description of the key features of Cooligy's closed loop Liquid Cooling System (LCS). Two key components of the LCS, namely a microheat exchanger and an electrokinetic pump are discussed in detail. Published literature on advanced thermal interface materials and nanofluids are briefly reviewed. Wherever applicable, the importance and impact of electrochemical processing and materials aspects are highlighted.