bluuebunny/crossref_metadata_2025 huggingface dataset:
Process dependence of the thermal conductivity of image reversal photoresist layers
Authors: Hung Ming-Tsung , Ju Y. Sungtaek
Published: February 2007

Thermal transport in polymer layers is an important consideration in various lithography techniques, including immersion lithography and thermolithography. The in-plane thermal conductivity of commercially available photoresist AZ 5214E is determined at each stage of lithography processes using ultrathin (<100nm) freestanding membrane devices. The authors find that UV exposure does not lead to any appreciable change in thermal conductivity whereas cross-linking induced by postexposure bake results in a slight increase (∼5%). The thermal boundary resistance across interfaces between the resist layers and metal films/substrates is also found to be significant. The experimental techniques and data presented here will facilitate a systematic evaluation of thermal phenomena during lithography processes.
High-Q micromachined three-dimensional integrated inductors for high-frequency applications
Authors: Weon Dae-Hee , Jeon Jong-Hyeok , Mohammadi Saeed
Published: February 2007

Three-dimensional micromachined inductors are fabricated on high-resistivity (10kΩcm) and low-resistivity (10Ωcm) Si substrates using a stressed metal technology. On high-resistivity Si substrate with low-k dielectric material (SU-8™), this technology achieves a quality factor Q of 75 for a 1nH inductor at frequencies around 4GHz and a self-resonant frequency fsr above 20GHz. Using Si bulk micromachining to etch away the low-resistivity Si substrate with a combination of deep reactive ion etching and tetramethyl ammonium hydroxide etching methods, a 1.2nH inductor achieves a peak quality factor Q of 140 at a frequency of 12GHz with a self-resonant frequency fsr above 40GHz. The dependence of high-frequency performance on the inductor’s variables, such as the number of turns, turn-to-turn gap, and substrate type, has been investigated. Excellent performance is achieved by removing the substrate due to the complete elimination of substrate losses and the reduction of the parasitic capacitance. This technology is simple and provides high performance integrated inductors on Si or compound-semiconductor platforms.
Effect of plastic fragments on hydraulic characteristics of pretreated municipal solid waste
Authors: Xie Mingliang , Aldenkortt Dirk , Wagner Jean-Frank , Rettenberger Gerhard
Published: February 2007

A systematic study was undertaken of the granular composition and hydraulic properties of municipal solid waste (MSW) produced by mechanical–biological pretreatment (MBP–MSW) from three different treatment plants with the aim of evaluating the potential application of MBP–MSW as an alternative barrier material for landfill final cover systems. Despite its coarse granular composition, MBP–MSW has low hydraulic conductivity. Long-term permeability tests show that the hydraulic conductivity decreases with time. The most likely explanation for the long-term changes in permeability is the swelling of organic material contained within the compost. In the case of saturated flow, the virtually impermeable plastic fragments embedded in the material impede fluid flow. In the unsaturated case, such fragments slow down the drying process by disrupting fluid flow and allowing pooling of water above horizontally oriented fragments. The larger the number and size of the plastic fragments, the greater the influence on hydraulic conductivity and shrinkage. These processes can be better understood with the newly developed conceptual model, the thin-sheet model. Based on this conceptual model, laboratory tests were undertaken to compare natural soil material with mixtures of soil material and plastic fragments. Corresponding numerical simulations of some experiments verified the influence of plastic fragments on the hydraulic properties of MBP–MSW.Key words: mechanical–biological pretreatment, municipal solid waste (MSW), thin-sheet model, plastic fragment, hydraulic conductivity, drying test.
Theoretical basis and numerical simulation of impedance log test for evaluating the integrity of columns and piles
Authors: Yu Chih-Peng , Liao Shu-Tao
Published: February 2007

In this paper, the theoretical capabilities of the impedance log method in profiling the geometry of a column or pile along its length are investigated. The main idea of this method is to introduce a transient stress wave into the member and then utilize the reflected signals to obtain the impedance profile. The impedance profile is then used to recover the equivalent cross-sectional area along the length of the pile. To gain an insight into this nondestructive evaluation technique, this research started with a review of its theoretical background. The dynamic behavior of defective columns or piles with weak zones, bulges, and necks of constant or varying cross sections were then simulated with finite element models. The success in recovering the profiles of this kind of rod-like structural members proved that the impedance log method is a tool with high potential for evaluating the integrity of piles.Key words: impedance log method, nondestructive test, stress wave, column, pile.
Challenges to modelling heave in expansive soils
Authors: Vu Hung Q , Fredlund Delwyn G
Published: February 2007

There are challenges associated with the numerical modelling of unsaturated expansive soils. The challenges are primarily related to the quantification of the void ratio constitutive surface, the characterization of the void ratio constitutive surface at low stresses and (or) suction, and the solution of coupled equations with several nonlinear unsaturated soil property functions. This study suggests that the void ratio constitutive surface of an expansive soil subject to a monotonic wetting path can be estimated from volume change indices obtained from conventional laboratory tests. The constitutive surfaces for both the soil structure and the water phase can be described using mathematical equations that allow net normal stress and suction to be reduced to zero. The solutions for two typical volume change problems are presented using both a coupled approach and an uncoupled approach. The first example problem simulates water leakage from a pipe under a flexible cover. The second example problem simulates the infiltration of water at ground surface. The results of the analyses are in accordance with anticipated behaviour. The results also show that the answers from an uncoupled analysis compared well with those from a coupled analysis. It is suggested that an uncoupled analysis may be adequate for most prediction of heave problems involving unsaturated expansive soils.Key words: heave prediction, numerical modelling, expansive soil, constitutive surface, uncoupled analysis, matric suction.
Evaluation of elementary filtration properties of a cement grout injected in a sand
Authors: Saada Zied , Canou Jean , Dormieux Luc , Dupla Jean-Claude
Published: February 2007

This paper presents the results of an experimental study aimed at evaluating the elementary filtration properties of a fine cement grout injected in a sand. In a first step, the experimental setup or filtration cell, specially developed for injecting thin samples of sand put under stress, is presented. Next, the results of an experimental programme carried out with this cell are presented, allowing for the study of the influence of basic parameters (density index, consolidation stress, cement concentration in the grout, and injection flow rate) on the filtration properties of a typical grout composed of fine cement. A filtration coefficient is then defined, allowing for characterization of the elementary filtration properties of the tested grout by the sand matrix. Finally, the respective influence of tested parameters on the value of this coefficient is presented and discussed.Key words: cement grout, suspension, filtration, flow, sand, injection.
Transversely isotropic stiffness parameters and their measurement in Colorado shale
Authors: Gautam Rajeeb , Wong Ron CK
Published: February 2007

Drained stress path triaxial tests and confined torsion tests were conducted on Colorado shale core samples to investigate transversely isotropic stiffness parameters at small strain deformation. Nonlinear plastic behaviour occurred along the primary loading path even at strains less than 0.01%. Nonlinear, hysteric behaviour was only observed during the loading–unloading path. However, the shale material displayed transverse isotropy in deformation, and very small or nondetectable Poisson's ratios in vertical and horizontal directions. This special response alludes to the postulate that the Colorado shale could be approximated by a transversely isotropic elasticity model at small strain levels with negligible yielding.Key words: anisotropy, elasticity, stiffness, triaxial test, torsion test, shale.
A model test and numerical investigation on the shear deformation patterns of deep wall–soil–tunnel interaction
Authors: Lee Yong-Joo , Bassett Richard H
Published: February 2007

In congested urban areas, tunnel excavations have become necessary due to a lack of space. In many cases, such excavations are needed in areas adjacent to existing loaded piles. Therefore, a careful assessment of the wall–soil–tunnel interaction is required. These circumstances are relatively new, however, and only limited information is currently available. The complicated soil behaviour, particularly for the shear failure pattern between the wall and tunnel observed in both physical tests and numerical analyses, has not been clearly identified by other researchers. The authors have conducted laboratory model tests on an idealized granular medium using close-range photogrammetric techniques to measure detailed displacement patterns. The results have been compared with those from numerical analyses. This paper presents shear failure patterns for a number of geometries and shows good agreement between the physical tests and the finite element analyses.Key words: tunnel excavation, shear deformation patterns, wall–soil–tunnel interaction, model tests, photogrammetry, finite element analysis.
MODULAR RANKING ABSTRACTION
Authors: BALABAN ITTAI , PNUELI AMIR , ZUCK LENORE D.
Published: February 2007

Predicate abstraction has become one of the most successful methodologies for proving safety properties of programs. Recently, several abstraction methodologies have been proposed for proving liveness properties. This paper studies "ranking abstraction" where a program is augmented by a non-constraining progress monitor based on a set of ranking functions, and further abstracted by predicate-abstraction, to allow for automatic verification of progress properties. Unlike many liveness methodologies, the augmentation does not require a complete ranking function that is expected to decrease with each helpful step. Rather, adequate user-provided inputs are component rankings from which a complete ranking function may be automatically formed.

The premise of the paper is an analogy between the methods of ranking abstraction and predicate abstraction, one ingredient of which is refinement: When predicate abstraction fails, one can refine it. When ranking abstraction fails, one must determine whether the predicate abstraction, or the ranking abstraction, needs be refined. The paper presents strategies for determining which case is at hand, and methods for performing the apporpriate refinements.

The other part of the analogy is that of automatically deriving deductive proof constructs: Predicate abstraction is often used to derive program invariants for proving safety properties as a boolean combination of the given predicates. Deductive proof of progress properties requires well-founded ranking functions in addition to invariants. We show how the constructs necessary for a deductive proof of an arbitrary LTL formula can be automatically extracted from a successful application of the ranking abstraction method.
REASONING ABOUT TRANSFINITE SEQUENCES
Authors: DEMRI STÉPHANE , NOWAK DAVID
Published: February 2007

We introduce a family of temporal logics to specify the behavior of systems with Zeno behaviors. We extend linear-time temporal logic LTL to authorize models admitting Zeno sequences of actions and quantitative temporal operators indexed by ordinals replace the standard next-time and until future-time operators. Our aim is to control such systems by designing controllers that safely work on ω-sequences but interact synchronously with the system in order to restrict their behaviors. We show that the satisfiability and model-checking for the logics working on ωk-sequences is EXPSPACE-complete when the integers are represented in binary, and PSPACE-complete with a unary representation. To do so, we substantially extend standard results about LTL by introducing a new class of succinct ordinal automata that can encode the interaction between the different quantitative temporal operators.
SUPERCONTINUUM SPECTRUM GENERATION IN THE LIQUIDS WITH DIFFERENT BAND GAP THRESHOLDS
Authors: ZHANG SHIAN , SUN ZHENRONG , DENG LI , WANG ZUGENG
Published: February 2007

Supercontinuum spectrum generation by femtosecond laser pulses propagating in transparent liquids with different band gap thresholds is investigated. As the laser energy increases, the laser spectrum is strongly broadened and modulated, and finally a supercontinuum spectrum can be observed. The spectral broadening can be mainly attributed to the optical Kerr effect at low laser energy and the plasma created by the multiphoton excitation of electrons from the valence band to the conduction band at high laser energy. It is found that the spectral broadening and modulation strongly depend on the band gap threshold E gap of the medium.
Advances in Multifunctional I/O
Authors: Kohl Paul , He Ate , Spencer Todd
Published: February 2007

A copper-to-copper bonding process was developed for an all- copper, chip-to-substrate interconnect technology. High aspect ratio, polymer molds for electroplating were formed using a photodefinable polymer on both the chip and the substrate surfaces. Copper pillars were fabricated by electroplating metal in the polymer molds. The chip-to-substrate all-copper connections were formed by joining the two pillars with an electroless copper plating and anneal process. The copper-to- copper bonding of the high aspect ratio pillars does not require the use of solder or other non-copper metals. Mechanical shear force measurements were used to characterize the bonding process as a function of annealing conditions. Excellent bond strength of the electrolessly joined pillars was achieved with a 250{degree sign}C anneal. The bond strength of the copper pillar interconnects exceeded 148 MPa. High aspect ratio of the pillars can provide mechanical compliance and the electroless fabrication method compensates for pillar misalignment and non-planarity of the bonded surfaces.
Advanced Metrology and Control of Copper Electrochemical Deposition I: The Decomposition Chemistry of the Accelerator SPS
Authors: Bailey Thomas H. , Wang Qin , West Michael
Published: February 2007

Future advances in effective control of the chemical composition of copper electrochemical baths will require an understanding and proactive management of the decomposition products of the additives. To this end, we present the results of mass-spectrometric techniques applied to the identification and quantitation of species that accumulate in Cu-ECD baths by irreversible decomposition of the accelerator bis-(sodium 3- sulfopropyl) disulfide (SPS). Most SPS is converted to 1,3- propanedisulfonic acid (PDS) by way of anodic oxidation via four intermediates, some of which participate in competitive side-reactions that yield alternative decomposition products. A different mechanistic route affords 3-sulfopropan-1-ol as the second most abundant by-product. In this paper we propose several models of SPS decomposition that invoke interfering with the key intermediates in the copper electrodeposition mechanism, and speculate on the role of accelerator break-down products in inducing defects in wafer processing.
The Role of Surface Active States in Copper Electrodeposition in Acid Solution.
Authors: Burke Laurence D. , Buckley Claire , Sharna Rezwana
Published: February 2007

Copper metal electrodes in aqueous acid media exhibit two different types of electrochemistries, one related to the redox behaviour of low energy surface metal atoms (Cu/Cu2+) and the other based on the redox behaviour of low coverage, high energy, surface metal atoms (it is assumed that the latter transition involves magic number surface cluster species, Cu2/Cu2
+). The latter transition occurs well within the double layer region and the conversion of Cu2
+ to Cu2in the negative sweep triggers the onset of electrocatalysis, e.g. of nitrate reduction, and the loss of inhibition, in the presence of thiourea or PEG+Cl- ions, of the copper plating reaction. The behaviour of the combination of bath additives used in Damascene copper plating is complex and requires further investigation.
Electrodeposition of Magnetic Multilayers into Micro- and Nano- Recesses
Authors: Podlaha Elizabeth J. , Iyer Diwakar , Murphy Michael , Li Yutong , Mishra Rohit , Moldovan M. , Young D. P.
Published: February 2007

An overview of recent topics at Louisiana State University is reviewed with an emphasis on electrodeposited alloys into deep recessed geometries. Microposts of CoCu/Cu have been fabricated that exhibit magnetoresistance when the current is perpendicular to the layers. Invar-like FeNiCu/Cu microposts having low coefficient of thermal expansion (CTE) are presented and exhibit a negative CTE prior to heat treatment. Microhardness of the Invar-like copper multilayered microposts was comparable to NiW alloys deposited as microposts. The electrodeposition of rare earth-transition metals were found to behave similar to NiW. Nanowire and nanotube deposition of CoGd and CoGd/Cu multilayers were presented.
Detection of Precursor Molecules in the MCR-CVD (metal chloride reduction-chemical vapor deposition) of Copper
Authors: Hibi Atsushi , Susa Akio , Koshi Mitsuo
Published: February 2007

Gaseous metal chlorides can be precursors in a novel CVD method called metal chloride reduction-chemical vapor deposition (MCR-CVD). In the present study, we focused on the etching process of MCR-CVD of copper. There are more than one species in the gas phase of copper chlorides, which are considered to work as precursors. We detected gaseous copper chloride molecules generated by etching of copper surface by mass spectrometry. The composition of gaseous species might change by gas phase reactions. The etching process of copper surface by chlorine could not be regarded as equilibrium process.
In Situ Characterization of Gas-Phase Species Present During Hafnium Oxide Atomic Layer Deposition
Authors: Maslar James E. , Hurst Wilbur , Burgess Donald , Kimes William , Nguyen Nhan
Published: February 2007

In this work, the species present in the gas phase during atomic layer deposition of hafnium oxide were investigated in an attempt to gain insight into the chemistry of this system. Hafnium oxide was deposited on a silicon substrate using tetrakis(ethylmethylamino) hafnium, Hf[N(C2H5)(CH3)]4, and water. In situ infrared absorption spectroscopy measurements were performed in a research-grade, horizontal-flow reactor under a range of deposition conditions. Density functional theory quantum calculations of vibrational frequencies of expected species were used to facilitate identification of observed spectral features.
Non-linear Surface Reaction Kinetics of GaAs MOVPE Explored by Selective Area Growth
Authors: Song Haizheng , Sugiyama M. , Nakano Yoshiaki , Shimogaki Yukihiro
Published: February 2007

Two-dimensional or three-dimensional numerical simulation on growth rate non-uniformity of selective area metalorganic vapor phase epitaxy in sub-millimeter scale can extract real surface kinetics, which is normally hindered by mass transport rate of film precursors. Non-linear surface kinetics is introduced to analyse group-III precursor concentration dependency for the first time and surface reaction rate constant (ksn) of adsorbed species and adsorption equilibrium constant (K) are extracted from GaAs-MOVPE at 575 C. The effect of misorientation angle of GaAs (100) substrate on these kinetic parameters is examined. It is found that ksn is about 3.4×10-5 mol/m2/s independent of the angle, whereas K is 6.9-12×10-5 m3/mol dependent on the angle. The obtained value of ksn can be converted to lifetime of adsorbed species on GaAs surface and it is 0.3 sec. This is mostly the same with gas-phase decomposition rate of trimethylgallium and supports the accuracy of our non-linear kinetic analysis.
The Effect of Process Parameters on CVD Cu Seed Layer Deposition on Ru and Ta Under-layer
Authors: Kim Hoon , Kojima Yasuhiko , Yoshii Naoki , Sato Hiroshi , Hosaka Shigetoshi , Shimogaki Yukihiro
Published: February 2007

To deposit ultra-thin CVD Cu seed layer, Ru is evaluated as new barrier material, and the morphology and adhesion property of CVD Cu deposition on Ru are compared with that on Ta. CVD Cu films on Ru shows higher nuclei density than that on Ta. Lower (90oC) deposition temperature, and high source concentration also improves the nucleation density of CVD Cu. About 20 nm of smooth and continuous CVD Cu seed layer is deposited on Ru under-layer at 90oC and high source concentration condition. CVD Cu on Ru has a good adhesion property because impurity layer, which degrades the adhesion property of CVD Cu, is not formed at the interface. Introducing Ru under-layer and optimizing deposition condition enable thin and smooth CVD Cu seed layer deposition for the future Cu interconnects.
The Role of Alloying Elements in the Corrosion of Cobalt-based Alloys
Authors: Metikos-Hukovic Mirjana , Babić Ranko , Omanović Dario , Milošev Ingrid
Published: February 2007

Co-Cr-Mo alloys have been widely used as biomaterials to assist in the repair or replacement of bone tissue in the human body. In this study the influence of alloying elements on the properties of passive films, which are vital to the alloy's biocompatibility, was studied. In-vitro investigations were performed in a physiological Hank's solution with a pH of 6.8. Electrochemical techniques were used to study the oxido-reduction processes, while the structural properties of the electrified interfaces and the solid-state processes and changes inside the oxide films were studied using electrochemical impedance spectroscopy. The film's composition as a function of the applied potential was examined using X-ray photoelectron spectroscopy. A quantitative analysis of the metallic ions produced during a prolonged immersion of the investigated materials in the Hank's solution was carried out by high-resolution inductively coupled plasma mass spectrometry (HR ICP-MS). A good correlation between the results obtained from the different experimental techniques was obtained.
Composition and Morphology of Product Layers in the Steel/Cement Paste Interface in Conditions of Corrosion and Cathodic Protection in Reinforced Concrete
Authors: Koleva Dessislava , van Breugel Klaas , de Wit J.H.W , Boshkov Nikolai , Fraaij A.L.A
Published: February 2007

The present study explores the formation of corrosion products on the steel surface in reinforced concrete in conditions of corrosion and subsequent transformation of these layers in conditions of cathodic protection (CP). Of particular interest was to investigate if the introduced pulse CP (as cost- effective alternative of CP) will lead to similar (or even better) transformation of the product layers on the steel surface, compared to conventional techniques. Qualification and quantification of the studied layers was performed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray analysis (EDAX), visualization of morphology and products distribution was achieved using environmental SEM (ESEM).
Anodic Copper Oxidation in Alkaline Mediums with α-Alanine and Asparagine Acid Additives
Authors: Kaluzhina Svetlana A. , Skrypnikova Ekaterina , Orlova Eugenia , Kosareva Jlia
Published: February 2007

It was investigated α-alanine and asparagine acid influence on copper anodic process kinetics in alkaline electrolytes. The experiments were carried out at two systems: I - 0.01 M NaOH +X M α-Ala (X=10-4/10-1 M) and II - 0.01 M NaOH +X M Asp (X=10- 5/10-3 M). It was found out that α-alanine (from СAla= 5*10-3 М to 2*10-2 М) and asparagine acid (from СAsp=1*10-5 to 1*10-3 М) stimulate anodic processes at passive region and cause of metal local activation. However except this general regularity, the individual singularity at both systems were found out: at the I system local activation develops under ЕLA=0.10-0.20 V, at the II system two local activation potentials were identified Е1LA=0,23-0,34 V and Е2LA =0.70-0.85 V, which were divided by repassivation region.
Proton Conduction in In3+-doped SnP2O7 with Various P/(Sn+In) Ratios
Authors: Nagao Masahiro , Kamiya Toshio , Heo Pilwon , Hibino Takashi , Sano Mitsuru , Tomita Atsuko
Published: February 2007

A proton conducting, 10 mol% In3+-doped SnP2O7 was characterized by TGA, TEM measurement, and electrochemical techniques. We prepared Sn0.9In0.1P2{plus minus}xO7{plus minus}x samples with various P/(Sn+In) molar ratios from 1.7 to 2.6. Sn0.9In0.1P2O7 with a stoichiometric P/(Sn+In) molar ratio of 2.0 showed a proton conductivity of about 0.19 S cm-1 at 250oC under unhumidified conditions. When the P/(Sn+In) molar ratios were over 2.0, amorphous layer composed of phosphorus compounds were observed over the surface of Sn0.9In0.1P2O7 particles. The proton conductivity slightly increased with increasing the P/(Sn+In) molar ratios from 2.0 to 2.6. It is considered that the amorphous layer enhanced the proton conductivity by surface conduction. On the other hand, the thermal stability of this amorphous layer during heating- cooling cycle was not enough high to apply to electrochemical devises. It is important to prepare Sn0.9In0.1P2O7 with the P/ (Sn+In) molar ratio of 2.0 to achieve both sufficient proton conductivity and high thermal stability.
Characterization of Surface Preparation for Epitaxial SiGe Process using X-ray Reflectivity
Authors: Agnihotri Dileep , Lee Charlie Cj , Tai Hsin , Chen Arthur , Ma Mike , Baxter Steven , Gallegos Jesus , Kalegaonkar Shrikant
Published: February 2007

This paper discusses applications of X-ray reflectivity [XRR] and X-ray fluorescence [XRF] methods for characterization of SiGe process, including measurement of film thickness and composition as well as for control of the surface preparation for the SiGe process. Various step of a pre-clean process are also characterized using XRR data. Effect of pre-clean process on Si substrate is verified through XRR and TEM measurements.
Photoluminescence as Complimentary Technique for Metals Contamination Monitoring After Thermal Processing
Authors: Rapoport Igor , Taylor Patrick , Kim Seung-Bae , Orschel Benno
Published: February 2007

Photoluminescence (PL) was proposed as non-destructive technique for highly doped silicon material characterization. PL intensity had been observed to decrease for intentionally metal contaminated areas. PL studies were applied to iron contaminated silicon wafers after the thermal treatment at 1150 and 1250oC to validate the PL technique for the quantitative evaluation of bulk iron in silicon. Iron contamination ranged from 109 cm-3 to 1012 cm-3. For lightly doped p-type and n-type silicon a good correlation was found between PCD lifetime, SPV diffusion length (DL) and iron readings and PL intensity readings. PCD, SPV and PL high- resolution mapping was applied to build the point-to-point correlation. PL was shown to be sensitive to iron contamination at concentrations exceeding 1010cm-3 as calibrated by SPV using lightly doped p-type silicon. PL may be used as high-resolution non-destructive technique to track down the metal contamination sources in wafers processing.
Synthesis and Characterization of a New Porphyrin-fullerene Dyad Containing a Beta-pyrrolic Linkage
Authors: Lembo Angelo , Tagliatesta Pietro , Guldi Dirk M.
Published: February 2007

Two new beta-substituted arylethynyl meso- tetraphenylporphyrins, 2-[(4'-formyl)phenyl]ethynyl-5,10,15,20- tetraphenylporphyrin (System A) and 2-[(4'-methyl)phenyl] ethynyl-5,10,15,20-tetraphenylporphyrin (System B) and their zinc derivatives were synthesized. Comparative UV/Visible and cyclic voltammetry studies of such macrocycles reveal the presence of an extensive conjugation between the tetrapyrrolic ring and the linker, through π-π orbitals interaction. This interaction was observed in form of a push-pull effect that moves the electronic charge between the porphyrin and the aldehyde group of the System A. System B, bearing a methyl instead of the formyl group, was synthesized in order to evaluate the effect of the substitution on the charge delocalization, which is necessary to corroborate the push- pull mechanism hypothesis. The new porphyrin, System A, was also used as starting material for the synthesis of new porphyrin-fullerene dyads in which the [60]fullerene is directly linked to the tetrapyrrolic rings by ethynylenphenylen subunits. Fluorescence and transient absorption measurements of the new dyads reveal that ultrafast energy and electron transfer occur respectively in non polar and polar solvents, with high values of the rate constant.
Formation of a Charge-Separated State of a Fullerene-Trinitrofluorenone Dyad by Complexation with Scandium Ion
Authors: Ohkubo Kei , Ortiz Javier , Martín-Gomis Luis , Fernández-Lázaro Fernando , Sastre-Santos Ángela , Fukuzumi S.
Published: February 2007

A long-lived charge-separated state of fullerene-trinitrofluorenone linked dyad (C60- TNF) is formed in the presence of Sc(OTf)3 via intramolecular electron transfer from the singlet excited state of fullerene to TNF and binding of Sc3+ to the resulting TNF radical anion. The lifetime of the charge-separated state is determined as 23 ms in PhCN at 298 K.
DC Characterisation of C60 Whiskers and Nanowhiskers
Authors: Larsson Michael , Kjelstrup-Hansen J. , Lucyszyn Stepan
Published: February 2007

C60 whiskers exhibit increasing conductivity with decreasing diameter. At diameters of 1 mm and below, a single-crystal structure predominates, and enhanced electrical characteristics are expected; however, no supporting data exists in the literature. Here, results of four-point probe measurements on C60 whiskers and nanowhiskers with diameters in the range 650 nm to 1.3 mm are reported for the first time. Samples are attached to pre-patterned planar and raised electrodes using FIB-deposited tungsten. A low resistivity of 3 Wcm is measured in air, on a C60 whisker having a diameter of 650 nm, indicating strong potential for use in organic electronic applications of the future. Repeated current cycling in air is observed to promote sample degradation, possibly due to progressive oxidation of the carbon structure. A micromachined four-point probe is also used to try to establish non-invasive electrical connections with samples. Preliminary results of such trials are presented, indicating it to be a feasible alternative to the use of deposited electrodes.
Sodium Ion Effect on Photoinduced Electron Transfer of Porphyrin-Crown Ether-Affixed Quaterthiophene-[60]Fullerene Triad as a Gated Molecular Switch
Authors: Ito O. , Zhang Huimin , Oike Takuro , Kurata Tomoyuki , Takimiya Kazuo , Otsubo Tetsuo , Aso Yoshio , Araki Yasuyuki
Published: February 2007

A porphyrin-quaterthiophene-fullerene triad, in which the center of the quaterthiophene spacer is additionally bridged with a crown ether chain in a sash manner has been newly synthesized. Photoinduced charge-separation (CS) and charge-recombination processes in the absence and presence of Na+ have been investigated by time-resolved fluorescence and transient absorption spectroscopic methods.
Synthesis of Trimetasphere Pyrrolidino Derivatives: Reaction of Lu3N@C80 with N-Ethylglycine in the Presence and Absence of Aldehyde
Authors: Zhou Zhiguo , Zhang Jing , Sadler Robert , Yang Jianzhong , Coleman Arthur
Published: February 2007

The [2+3] cycloaddition reaction was studied on Lu3N@C80 with N-ethylglycine in the presence and absence of aldehyde. Both reactions afforded the same symmetrical [5, 6] fulleropyrrolidine adduct. However, the reaction on C60 with N- ethylglycine in the absence of aldehyde formed a methanofullerene derivative and a fulleropyrrolidine derivative.
Wet Chemical Approaches for Fabricating Metal Nanoparticle-Attached Electrodes
Authors: Oyama Munetaka
Published: February 2007

Wet chemical methods are proposed to modify the surfaces of conducting substrates with metal nanoparticles. In the cases of Au, Ag and Pd, a seed-mediated growth method permitted the surface modification of indium tin oxide (ITO) with the nanoparticles via the two-step immersion into the seed solution and the growth solution. In the case of Pt, in situ chemical reductive growth method was successfully applied to modify the surfaces of ITO and glassy carbon with Pt nanoclusters. Furthermore, by changing the component of the growth solution in the seed-mediated growth method, the crystal growth of Au nanoplates were possible on the ITO surface.
π-Complex Formation between Bisporphyrin and Acridinium Ion and the Photodynamics
Authors: Tanaka Makiko , Ohkubo Kei , Gros Claude P. , Guilard Roger , Fukuzumi S.
Published: February 2007

Acridinium ion forms a pai-complex with a free-base bisporphyrin through pai-pai interaction in benzonitrile. Photoinduced electron transfer from a cofacial bisporphyrin to acridinium ion in a pai-complex formed between a cofacial bisporphyrin and acridinium ion results in formation of the persistent electron- transfer state at low temperature.
Simulation of Wet-Dry Cycling of Organic Coatings using Ionic Liquids
Authors: Allahar Kerry N. , Hinderliter Brian , Simoes Alda , Tallman Dennis , Bierwagen Gordon , Croll Stuart
Published: February 2007

The diffusion coefficient of water Din associated with the ingress in an organic coating is an indicator of the rate at which the coating absorbs water. Likewise, the diffusion coefficient associated with water egress Dout is an indicator of the drying rate of the coating. The measurement of Din by gravimetric and capacitance methods have been reported, and so to Dout by gravimetry. Reported recently was a method that employed a hydrophilic room temperature ionic liquid to monitor the capacitance changes associated with the egress of water from which Dout was calculated. Experimental results associated with cyclic dilute NaCl wetting and ionic liquid drying are presented for an epoxy coating on an AA 2024-T3 substrate. The Din and Dout values were calculated using a short-time approximate solution and a series solution to Fick's second law. Electrochemical impedance spectra associated with the ends of wet and dry stages of the cycles are presented.
A Study of Magneto-Rheological Fluid Using AC Electrochemical Impedance Spectroscopy
Authors: Hu Jim , Seitz Martin
Published: February 2007

A Magneto-rheological (MR) fluid was characterized using ac electrochemical impedance spectroscopy in the presence and absence of a magnetic field. It was found that MR fluid was very insulating in the absence of the magnetic field, but became very conductive under the field. The equivalent circuit representation indicated that the interfacial process at the metal/fluid interface was dominated by diffusion in the absence of the field, while it turned to be a constant phase element at the interface under the field.
Study of the Adsorption and Oxidation of Phenol at the Poly-tropism Platinum Electrode
Authors: Feng Yujie , Ding Haiyang
Published: February 2007

Cyclic voltammetric (CV), Tafel curve and Electrochemical impedance spectra were applied to investigate phenol electrochemical oxidation process on the poly-tropism platinum electrode. It was determined that the electrochemical oxidation of phenol on platinum electrode was irreversible process and the position of oxidation peak lies at 0.926V(vs. Ag/AgCl) at the scanning rate of 50mV·s-1. The relationship between the oxidation peak current of phenol and the scanning rate was also got and it could be concluded that the phenol oxidation process was controlled by both of the diffusion and adsorption step. In the sulfuric acid system, the Tafel curve of platinum electrode was obtained and the results might indicate that single electron transfer on the process of phenol electrochemical reaction on the platinum might be the dominated step. Electrochemical impedance spectra showed a semicircle of capacitor resistance due to the phenol adsorption in high frequency.
Crosstalk Effect in Electrochemical Impedance of Micro-Patterned Pt Electrodes on YSZ Thin Film
Authors: Dubbe Andreas , Näfe Helfried
Published: February 2007

Inductive effects in the impedance of stripe-shaped patterned Pt micro electrodes on YSZ thin films on sapphire were ascribed to a crosstalk effect between adjacent electrodes via oxygen diffusion in the gas phase. A model assuming a reaction sequence with oxygen radical ion intermediates could explain the experimentally observed inductive part of the impedances. The evaluation of the experimental data resulted in plausible model parameters.
Electrochemical Impedance Spectroscopic Study of Passive Zirconium in High Temperature De-aerated Aqueous Solutions
Authors: Macdonald Digby D. , Ai Jiahe , Chen Yingzi , Macdonald Mirna
Published: February 2007

The Point Defect Model (PDM) was further developed to account for the properties of passive films comprising oxide barrier layers and porous oxide outer layers that form on zirconium and Zircaloys under simulated boiling water reactor operating conditions. The model parameter values were extracted from electrochemical impedance spectroscopic data for zirconium in de-aerated, borate buffer solution (pH 6.94) at 250C by optimization. The results indicate that the corrosion resistance of zirconium in high temperature, de-aerated aqueous solutions is dominated by the outer layer. The impedance model based on the PDM provides a good account of the growth of the bi-layer passive films, and the extracted model parameter values might be used, for example, for predicting the accumulation of general corrosion damage to Zircaloy fuel sheath in BWR operating environments.
Anodic Dissolution of Ni in a Polymer+Graphite Matrix
Authors: Gregori Joan , Garcia-Jareño Jose Juan , Peña Maria Pilar , Sanz Concepcion , Escrig C , Vicente Francisco
Published: February 2007

The electrodissolution processes for a nickel powder randomly dispersed in a graphite+polyproylene composite electrode has been studied by means of impedance and voltammetric techniques in acid media. Evidences of an electrodissolution process through an electrogenerated film on the electrode surface are visible in the recorded impedance spectra. The capacitive behaviour at low frequencies tends to a diffusion limited one for more anodic stabilization potentials. This evolution has been quantified in terms of the values of the elements of an equivalent circuit which considers a Warburg/Capacitance parallel arrangement. Finally, the differences in the redox activity for a Prussian Blue film deposited on the composite and polycrystalline nickel electrode have been analyzed in order to test this new material as a useful work electrode.
Application of Electrochemical Impedance Spectroscopy in the Evaluation of Corrosion and Cathodic Protection in Reinforced Concrete
Authors: Koleva Dessislava , van Breugel Klaas , de Wit J.H.W , Fraaij A.L.A , Boshkov Nikolai
Published: February 2007

The electrochemical behavior of steel reinforcement in conditions of corrosion and cathodic protection (CP) was studied, using electrochemical impedance spectroscopy (EIS) and compared to reference (non-corroding) conditions. Polarization resistance (PR) method and potentio-dynamic polarization (PDP) were employed as well, in addition to AC 2 pin electrical resistance monitoring, thus deriving a comparison of the involved parameters. It was found out that EIS is readily applicable for evaluating electrochemical behavior of the steel surface not only for corroding or passive state, but also in conditions of CP, although the interpretation of derived parameters is not straightforward and is related to the properties of the product layers, formed on the steel surface in the different conditions. The evaluation of the electrochemical behavior of the steel surface, should take into account the crystallinity, morphology and composition of the surface layers, which were investigated by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX).
EIS Investigations of Transpassive Dissolution of Ferritic Steels in Aqueous and Molten Electrolytes
Authors: Bojinov Martin S. , Betova Iva , Tzvetkoff Tzvety
Published: February 2007

The present paper compares the kinetics of transpassive dissolution of ferritic steels in a phosphoric acid-based electropolishing solution and in molten KH2PO4. Voltammetric and impedance measurements point to two parallel pathways of the process, the first corresponding to oxidative dissolution of Cr. The second path is identified as the isovalent dissolution of Fe mediated by a chemical step involving interaction with an electrolyte-originating species. Kinetic models involving only surface reactions have been found to reproduce successfully the steady-state and the small amplitude ac response of the steels in both electrolytes. The kinetic parameters are estimated by a calculation procedure involving simultaneous fitting of the impedance spectra at several polarisation potentials and the steady state current vs. potential curve for a particular material-electrolyte combination to the model equations. The ability of the kinetic models proposed for aqueous solutions to account for the behavior of materials in molten salt medium is discussed.
Hot-wire Chemical Vapor Deposition of WO3 and MoO3 Nanoparticles and the Performance of Nanostructured WO3 Electrochromic Films
Authors: Dillon Anne , Deshpande Rohit , Lee Se-Hee , Parilla Philip A. , Jones Kim , Mahan Harv , To Bobby , Mitra Saibal
Published: February 2007

High-density crystalline WO3 nanoparticle bulk synthesis using a simple hot-wire chemical vapor deposition (HWCVD) technique has been previously demonstrated. Recent efforts have been focused on incorporation of WO3 nanoparticles into a thin film to determine its electrochromic (EC) performance. Compared to state-of-the-art amorphous films, nanostructured WO3 films show greater charge density for proton intercalation. Optical measurements indicate coloration efficiency (CE) values comparable to amorphous films and significantly better than crystalline films. New data also suggest enhancement in the EC performance for more sub-stoichiometric nanostructured WO3 films. Finally, we have also employed HWCVD technique for MoO3 nanoparticle synthesis. Depending on synthesis conditions, nanospheroids having diameters between ~ 5-20 nm and nanorods having diameters between ~20-50 nm and lengths between ~100-400 nm are obtained as indicated by transmission electron microscopy (TEM). Raman spectroscopy revealed the nanoparticles are highly crystalline a-phase MoO3.
Effect of Organic Additives on Magnetic Properties of Electroplated Cu/Co Thin Films
Authors: Hong Kimin , Bae Jonghak , Bang Wonbae , Kim Jin-Gyu
Published: February 2007

We fabricated thin Cu/Co multilayers by electroplating and investigated the magnetic properties. Structure analyses have shown that an organic additive in the plating electrolyte could improve the interface of Cu- and Co-layers and reduced the coercivity from ~75 Oe to ~20 Oe.
Synthesis and Durability of Improved Fuel Cell Catalysts
Authors: Van Zee John W. , Beard Kevin D. , Monnier John R.
Published: February 2007

A study of oxygen reduction reaction (ORR) catalysts prepared by the electroless deposition (ED) of PtCl62- on a carbon support is presented. The ED procedure used functionalized carbon that was seeded with a precursor (Pd or Rh) and dimethylamine borane (DMAB) as the reducing agent and citrate as the stabilizing agent. It is shown that the DMAB concentration and precursor loading affect the rate of ED proportionally and that high pH conditions inhibit ED. Over our concentration range, the citrate had no effect on rate of ED. The ED catalyst was characterized using transmission electron microscopy, cyclic voltammetry and these revealed that smaller particles with greater surface area could be synthesized with ED. However, no increase on ORR activity was observed.
An Enhanced Long-Persistent Red Phosphor: CaS:Eu2+, Tm3+, Ce3+
Authors: Jia Dongdong
Published: February 2007

Calcium sulfide singly and/or codoped with Eu2+, Ce3+ and Tm3+ phosphors were prepared by using a solid state chemical reaction method. Emission and excitation spectra of the samples were investigated. CaS:Eu2+ emission was found at 648 nm and CaS:Ce3+ emission was found at 515 nm. CaS:Eu2+,Tm3+ was long persistent and the persistence time was ~1 hour. By the doping Ce3+, CaS:Eu2+,Tm3+,Ce3+ persisted 22% longer than that of CaS:Eu2+,Tm3+. Strong energy transfer from Ce3+ to Eu2+ was found at a low doping concentration 0.1%. The brightness of Eu2+ emission was enhanced for about 20% by codoping with Ce3+.
Electrochemical Synthesis of Fluoro-Organic Compounds Using Iodine Compounds
Authors: Yoneda Norihiko , Fukuhara Tsuyoshi , Takahashi Yukio , Okimoto Mitsuhiro
Published: February 2007

The selective fluorination of alkyl iodide (1) having functional groups such as ketone, ester, chloro and tosylate takes place effectively at the iodide position in the presence of Et3N-3HF as an electrolyte affording alkyl fluoride (2) RF in high yields. Also, the iodofluorination of unsaturated hydrocarbons (3) has been successfully carried out using electro-chemically generated iodonium ion (I+) from a variety of iodide anion sources in the CH2Cl2 in Et3N-5HF electrolyte at room temperature to yield iodofluorination products (4).
Carbon-Acylation of Benzoic Anhydride Derivatives by Electroreduction
Authors: Matsunami Masato , Nishiguchi Ikuzo , Maekawa Hirofumi , Mizoguchi Shun
Published: February 2007

Electroreduction of benzoic anhydride derivatives in the presence of aliphatic acid anhydrides gave the corresponding C- and O-diacylated products or 1,2-diacetoxy olefins depending upon the reaction conditions. Particularly, nucleophilic acylation of carbonyl carbon atoms may be an interesting reaction in organic synthesis. C- and O-diacylated products are useful as starting materials of sympathomimetic drugs such as epinephrine and ephedrine derivatives.
Electrochemical Study of Aromatic Ketones in 1-Ethyl-3-methylimidazolium tetrafluoroborate
Authors: Cheek Graham T. , Canby Dana , Sanders Eli
Published: February 2007

The electrochemical reduction of 9-fluorenone and benzophenone has been studied in the 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) ionic liquid. A comparison of potential separation for successive 9-fluorenone reduction processes in EMIBF4 at 100 mV/s with those in acetonitrile provides evidence for complexation of the 9-fluorenone dianion by the EMI+ cation. Complexation of the 9-fluorenone carbonyl oxygen by added BF3 etherate has also been studied, producing a positive potential shift for the reduction process. The reduction of benzophenone in EMIBF4 shows two successive electron transfers only at higher scan rates (1 V/s), suggesting that proton transfer and / or complexation of benzophenone reduction products by the EMI+ cation may be involved. The peak potential separation for the benzophenone reduction processes at 1 V/s is similar to that for 9- fluorenone at 100 mV/s, indicating that the EMI+ cation also complexes the benzophenone dianion.