bluuebunny/crossref_metadata_2025 huggingface dataset:
U. S. Polycrystalline Thin Film Solar Cells Program
Authors: Ullal Harin S. , Zweibel Kenneth , Mitchell Richard L.
Published: March 2011

The Polycrystalline Thin Film Solar Cells Program, part of the United States National Photovoltaic Program, performs R&D on copper indium diselenide and cadmium telluride thin films. The objective of the Program is to support research to develop cells and modules that meet the U.S. Department of Energy's long-term goals by achieving high efficiencies (15% - 20%), low-cost ($50/M2), and long-time reliability (30 years). The importance of work in this area is due to the fact that the polycrystalline thin-film CuInSe2 and CdTe solar cells and modules have made rapid advances. They have become the leading thin films for PV in terms of efficiency and stability. The U.S. Department of Energy has increased its funding through an initiative through the Solar Energy Research Institute in CuInSe2and CdTe with subcontracts to start in Spring 1990.
Annealing Behavior of The Photoluminescence Lines in CdTe and Znx Cd1−x Te Single Crystals
Authors: Gonzalez-Hernandez J. , Reyes-Mena A. , Lopez-Cruz Elias , Allred D.D. , Allred Worth P.
Published: March 2011

The main lines in the photoluminescence spectra of Zn1Cd1−xTe single crystals grown by a modified Bridgman method in the compositional range of 0 ≤ X ≤ 0.25 have been identified. All crystals show only near-band-edge emission. To assist in the identification, various samples with different compositions were annealed under a Cd atmosphere. In the pure crystals, the prominent (A°,X) bound exciton line, as well as the doublet at longer wavelengths, disappear after the annealing. In contrast, the treatments do not change significantly the PL spectra of the mixed crystals.
Measurement of Interfacial Fracture Energy
Authors: Rosenfeld L. G. , Ritter J. E. , Lardner T. J.
Published: March 2011

The contact stresses resulting from indentation of a compliant coating on a rigid substrate cause debond cracks to initiate and propagate along the interface. The indentation debonding behavior of four polymer coatings on glass substrates is investigated. A model is developed for calculating interfacial fracture energy based on data of indenter load vs. debond crack size. Based on the experimental observations and the data for the four coating systems, the limitations of the model are discussed.
Spreading of Liquid Droplets on Cylindrical Surfaces: Accurate Determination of Contact Angle.
Authors: Daniel Wagner H. , Wiesel E. , Gallis H. E.
Published: March 2011

The wetting of cylindrical monofilaments by liquid polymers is a problem of much scientific and technological importance. In particular, the characterization of the physicochemical nature of interfaces is a key problem in the field of advanced fibrous composites. The macroscopic regime contact angle, which reflects the energetics of wetting at the solid-liquid interface, is difficult to measure by usual methods in the case of very thin cylindrical fibers.

In the present article a numerical method is proposed for the calculation of macroscopic regime contact angles from the shape of a liquid droplet spread onto a cylindrical monofilament. This method, which builds on earlier theoretical treatments by Yamaki and Katayama [1], and Carroll [2], very much improve the accuracy of the contact angle obtained. Experimental results with high-strength carbon, para-aramid, and glass fibers, are presented to demonstrate the high degree of accuracy of the method proposed.
Silicon-Based Coatings on Niobium Metal
Authors: Stupik P. D. , Jervis T. R. , Nastasi M. , Donovan M. M. , Barron A. R.
Published: March 2011

Silicon coatings on niobium substrates were subjected to thermal, ion beam and laser mixing, and the effectiveness of the different methods for the synthesis of graded interfaces was compared. The resulting metal/silicon interfaces were characterized by X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and Rutherford backscattering (RBS).
Solid State Reactions in Mechanically Deformed Composites in the Ni-Zr and the Ni-Ti Systems
Authors: White B. E. , Patt M. E. , Cotts E. J.
Published: March 2011

Differential scanning calorimetry and x-ray diffraction analysis were utilized to monitor solid state reactions in mechanically deformed Ni/Ti multilayered composites. Solid state reactions at temperatures less than = 650 K result in the formation of a highly disordered phase which is apparently amorphous.The subsequent nucleation and growth at higher temperatures of intermetallic compounds from the amorphous phase is examined. The relatively small thickness of amorphous material (less than 100 Å) which can be grown by solid state reaction in our Ni/Ti samples, combined with the indication that a disordered interface such as that produced by mechanical deformation facilitates these reactions in the Ni-Ti system, may provide some explanation for the relatively high degree of success experienced in the production of amorphous Ni- Ti by means of ball milling. Comparisons are made to results obtained in the Ni-Zr system.
The Effect of Weak Interface on Transverse Properties of a Ceramic Matrix Composite
Authors: Shimansky R. A. , Hahn H. T. , Salamon N. J.
Published: March 2011

Experimental studies conducted at the NASA Lewis Research Center on silicon carbide reaction-bonded silicon nitride composite system (SiC/RBSN) led to a significant observation regarding their unidirectional tensile properties. It was found that transverse stiffness and strength were much lower than those predicted from existing analytical models based on good interfacial bonding. Since the composite system was designed to have weakened interfaces to improve toughness, it was believed that these weakened interfaces were responsible for the decrease in transverse properties.

To support this claim, a two dimensional finite element analysis was performed for a transverse representative volume element. Specifically, the effect of fiber/matrix displacement compatibility at the interface was studied under both tensile and compressive transverse loadings. Interface debonding was represented active gap elements connecting the fiber and matrix.

The analyses show that the transverse tensile strength and stiffness are best predicted when a debonded interface is assumed for the composite. In fact, the measured properties can be predicted by simply replacing the fibers by voids. Thus, the following two conclusions are drawn from the present study: (1) little or no interfacial bonding exists in the SiC/RBSN composite; (2) an elastic analysis can predict the transverse stiffness and strength.
The Influence of Interfacial Modification on Tensile Strength of Gr/Al Composites
Authors: He Cheng , Zhang Guoding , Wu Renjie
Published: March 2011

Varying the composition of the matrix alloy was a useful technique for tailoring the interfacial structure of MMC. In this paper, the influence of different interfacial states on the tensile strength of Gr/Al composites were investigated. Three aluminum alloys, pure Al, Al-Ti alloy (Ti oversaturated) and LY12 (an Al-Cu-Mg alloy) were chosen as the matrix materials. The results showed that the composites with Al-Ti matrix had excellent tensile properties, even after heat-treatment at 600°C, while with LY12 matrix exhibited poor properties compared with pure Al matrix. Microanalysis revealed that the interfacial structures of the composites with the above matrices were different. In addition, an initial study of mechanism of these matrix effects on the properties of the composites was also carried out.
Surface Forces and Adhesion Between Dissimilar Materials Measured in Various Environments
Authors: Smith Douglas T. , Horn Roger G.
Published: March 2011

The Israelachvili surface force apparatus has been used extensively over the past decade to make detailed measurements of surface forces and adhesion between very smooth solids in various liquid and vapor environments. Most of those measurements have been made with mica surfaces, but we have recently developed a method of preparing smooth silica surfaces for use in place of the mica. The silica surfaces adhere in dry and humid atmospheres, but do not adhere when immersed in water.

The use of a second material not only broadens the scope of the Israelachvili technique, but also enables studies of forces and adhesion between dissimilar materials. In this work, we present the results of measurements of adhesion in air and forces in aqueous solution between two silica surfaces; we also report preliminary results of the adhesion between a mica surface and a silica surface.
A Study of Winte Ohmic Contact to n-GaAs
Authors: Dutta R. , Lambrecht V. G. , Robbins M.
Published: March 2011

Electrical, structural and diffusion characteristics of a solid phase reacted ohmic contact to n-GaAs are studied. Attempts were made to form a low band gap interfacial phase of InGaAs to reduce the barrier height at the conductor/semiconductor junction and thus yielding a low resistance, high reliablity contacts. The understanding of the interface is important from the point of view of device performance as well as device reliability. The contacts were fabricated by co-sputtering W, In and Te targets on n-GaAs with subsequent annealing. The as-deposited rectifying contacts became ohmic when annealed to 500°C, and showed a specific contact resistance of ∽5×10-6 ohm cm2. The Auger and Rutherford back scattering analysis of the interface revealed an InGaAs phase formation prior to the onset of ohmic conduction. The contacts were stable up to 500°C and the surface morphology was superior to presently used AuNiGe contacts. The contact pads were patterned by dry plasma etching without adversely affecting the GaAs substrate.
An Investigation on Copper Red Glazes from Jingdezhen of the Ming and Qing Dynasties
Authors: Guozhen Li , Zeyong Liu , Yengyi Guo
Published: March 2011

Copper red glazes made at the pottery center of Jingdezhen during the Ming and Qing dynasties are one of the most famous and precious porcelain products of China. They were based on earlier technology developed in the Tong-guan kiln in Tang dynasty and on the Ru and Jun wares of the Song dynasty. The earliest copper red glazes appeared as early as the late Yuan dynasty. The dazzlingly beautiful altar red and ruby red products were created at Jingdezhen in the Yongle and Xuande periods of the Ming dynasty. Other copper reds created at Jingdezhen were the Longyao red of the Kangxi period and the imitation Jun, flambe amd others of Yongzhen and Qianlong periods of the Qing dynasty. Chinese copper red glazes have been held in high regard throughout the world, and many have wondered at their complex and sophisticated technology. Through analysis, we unlock some of the technical secrets of these famous wares in order that more people may appreciate the technical excellence underlying the visual appearances of these wares and that these glazes may be replicated better by contemporary ceramic factories in Jingdezhen.

Seven examples of Jingdezhen copper red glazes were analyzed by scanning electron microscopy, x-ray diffraction, refiring tests and microprobe analysis to determine the compositions, microstructures and firing temperatures.
Archaeometallurgy: Evidence of a Paradigm Shift?
Authors: Goodway Martha
Published: March 2011

Abtract:

Practitioners of archaeological and historical metallurgy have begun to identify their discipline by a new term: “archaeometallurgy.” Tracing the roots of this discipline shows that up to about 1980 the focus of study was on the technical examination of metal objects and determining site plans of metallurgical installations. Essentially it was a study of ancient metals of interest to historians of art or of technology. The focus then shifted to other materials and their archaeological contexts, processing byproducts such as slag, matte, furnace linings and furnace bottoms, crucibles, molds, cupels and tuyeres which are often more abundant on sites than metal. Thus the field of study has been enlarged beyond metallurgy to an interdisciplinary undertaking of materials science, archaeology, and material culture. Simultaneously with this shift in focus came the application of newly-developed instrumentation which supported a parallel shift in methodology from one emphasizing chemical analysis and microstructure to one of materials charactexrization, emphasising properties and performance.
Fine Metalwork from the Roman Cemetery at Stansted Airport, Essex Tinning and High Tin Alloys
Authors: Northover J. Peter , Brooks Howard , Lister Jan , Lloyd-Morgan Glenys
Published: March 2011

The early Roman cemetery discovered during the construction of London's third airport at Stansted contains the richest Roman burials discovered in Britain this century. The grave goods included a quantity of fine metalwork which forms te subject of this paper. The construction, alloys and finish of the pieces are described and discussed. Tin-plating and niello inlays are identified and described as is the analysis of corroded lead-tin solders and pewter. The manufacture of a high-tin bronze mirror is also discussed.
Conserving Iron Objects from Shipwrecks: A New Approach
Authors: Smith Herman A.
Published: March 2011

Recent experiments in the conservation of iron objects from several shipwrecks have resulted in a new method to arrest corrosion and stabilize the materials for further study or exhibition. The process involves the use of electrolysis and the application of a tannin preparation to neutralize the generation of iron-destructive compounds.
A Modular Approach to Microwave Applicator Design
Authors: Senise José T.
Published: March 2011

Whenever possible, the modular approach to microwave applicator design presents several advantages, both economical and operational, particularly in countries where high-power microwave generators are not manufactured on a commercial scale. In this paper, examples are shown of industrial applicators of simple, modular design, for the processing of liquid and solid materials, coupled to generators built with domestic microwave oven components.
Fiberoptic Sensor for Minimally-Perturbing Measurement of Electric Fields in High Power Microwave Environments
Authors: Sun M. H. , Wickersheim K. A. , Kamal A. , Kolbeck W. R.
Published: March 2011

Recently a small, minimally-perturbing, isotropic, and easy-to-use fiberoptic microwave E-field probe has been developed. This probe senses microwave energy by measuring the Joule heating of a susceptor material. It consists of two Luxtron Fluoroptic sensors. One measures the temperature of the susceptor formed as a thin-walled spherical shell, the other measures the temperature of the air around the susceptor so that any ambient temperature change can be subtracted. The differential temperature (δT) obtained between the two sensors is directly related to the microwave E-field strength or the power density corresponding to that field strength at the probe.
Dielectric Properties of Various Ranks of Coal and Numerical Modeling Under Electromagnetic Irradiation
Authors: Chatterjee I. , Misra M.
Published: March 2011

The dielectric properties of different ranks of Argonne Premium coal samples have been measured using an automated network analyzer system in the frequency range 0.3MHz to 3GHz. These measurements indicate that the inherent moisture present in the various ranks ofcoal has dielectric properties which are different from that of free water. The dielectric properties were also observed to increase with the moisture content as well as with the amount of oxygen present in the coal sample. A mixture model was successfully used topredict these dielectric properties.

The measured dielectric properties have been incorporated into numerical calculations ofthe distribution of absorbed energy in coal irradiated with electromagnetic waves. The numerical technique used is the Method of Moments. Subsequently, the temperature distribution obtained in the coal is evaluated using a Finite Difference technique to solve the heat conduction equation. These calculations should prove very useful in the microwave drying of coal where it is difficult to monitor the temperature using probes.
Technique for Measuring the Dielectric Properties of Minerals as a Function of Temperature and Density at Microwave Heating Frequencies
Authors: Salsman Johanna B.
Published: March 2011

As part of the research effort on investigating the effects of microwave energy absorption on the chemical and physical properties of minerals and ores, the Bureau of Mines, Tuscaloosa Research Center has developed a technique of measuring the dielectric constant and loss tangent of minerals at the common microwave heating frequencies. The objective was to establish a reliable data base to aid in predicting the effects of microwave heating on minerals.

In this phase of microwave research, the Bureau measured the dielectric properties of powdered minerals with medium to high electrical conductivities (a ≥ 0.02 Mho/m) in the frequency range of 300 MHz to 3 GHz using an open-ended coaxial line probe connected to an HP 8753A network analyzer. Since the minerals were prepared as powders, techniques were used to relate the measured dielectric properties of the powdered minerals to the dielectric properties of the mineral at Its theoretical or natural density. Also, these measurements were performed as a function of temperature, from 25° to 325° C.

The measured values of the dielectric constants and loss tangents using this method were accurate within ±5 percent. This report describes the method of measurement and discusses the results of the Bureau's investigations into dielectric properties of minerals.
Geometrical Arrangement of Magnetosomes in Magnetotactic Bacteria
Authors: Shih W.-H. , Sarikaya M. , Shih W. Y. , Aksay I. A.
Published: March 2011

In 1975, Blakemore discovered the freshwater magnetotactic bacterium Aquaspirillum magnetotacticum which navigates along the magnetic-field direction. Electron microscopic work showed that the magnetotactic bacteria contain magnetosomes which are intracytoplasmic membrane-bound particles of magnetite, Fe3 O4. The magnetosomes are within the single-domain size range (∼500 Å) of Fe3O4. The magnetosomes within cells are often arranged in one or more chains with the chain axis more or less parallel to the axis of motility of the cell. A detailed study of the magnetic properties of magnetotactic bacteria can be found in the paper by Moskowitz.
Alpha-Crystallin Protein Quaternary Structure Assembly Model
Authors: Licinio P.
Published: March 2011

Eye-lens alpha-crystallins are very peculiar In the sense that they present polydispersity, a quality most often shared by man made polymers. Quaternary structure studies reveal that these proteins are assembled from about 50 subunits of two kinds. We developped a mixed aggregation model which renders, for alpha-crystallins, both size and polydispersity, in accordance with data in the litterature. The initial stoichiometry controls stability in the aggregation process and should be a very sensitive parameter to monitor in mixed aggregations.
Advances in Self-Limiting Growth of Wide Bandgap II–VI Semiconductors
Authors: Konagai M. , Takemura Y. , Nakanishi H. , Takahashi K.
Published: March 2011

Recent advances in understanding the ALE (atomic layer epitaxy) growth of ZnSe, ZnS and ZnTe are reviewed. The Ideal ALE growth is obtained in the substrate temperature range of 250–350°C for ZnSe. In the ALE growth of ZnSe and ZnTe, a unique self-limiting mechanism is observed, in which the deposition rate saturates at 0.5 monolayer per cycle. Furthermore, applications of ALE of II–VI compounds to the growth of strained layer superlattices are also reviewed.
Atomic Layer Controlled Substitutional Doping With Lithium in ZnSe
Authors: Zhu Ziqiang , Kawashima Mitsuo , Yao Takafumi
Published: March 2011

The detailed observation of dynamical behaviors of reflection high energy electron diffraction (RHEED) patterns during the adsorption processes of Li, Se and Zn is carried out. It is found that the RHEED intensity variation reflects the Li surface coverage during Li adsorption process on a Secovered surface. This fact enables one to control quantitatively the doping of Li “in situ”. A new method for atomic-layer controlled substitutional doping of ZnSe layers with lithium is proposed based on the RHEED investigations. The method allows the incorporation of Li dopants on Zn-sites of ZnSe by monitoring the RHEED patterns and intensities, and is expected to suppress the compensation by Li interstitials. Photoluminescence spectrum shows the growth of high quality p-type layers.
Growth of ZnSe and ZnSSe at Low Temperature with Aid of Atomic Hydrogen and Alternate Gas Supply
Authors: Gotoh Jun , Shirai Hajime , Hanna Jun-ichi , Shimizu Isamu
Published: March 2011

High quality ZnSe films were successfully grown on GaAs(100) at low temperatures, 200 °C or lower by Hydrogen Radical-enhanced Chemical Vapor Deposition (HRCVD). Defects were makedly eliminated by the following factors: selection of source materials; avoidance of ion bombardment; and suppression of formation of adducts by alternate gas supply. Strained-layer superlattice (SLS) consisting of ZnSe as the well and ZnS0. 1Se0.9 as the barrier was made by this technique. Emission line attributed to the free exciton was dominantly observed in the SLS.
Synthesis and Optical Characterization of New NLO-Active Polyurethanes and a Silver Colloidal Suspension in a Select Polyurethane
Authors: Kitlplchal P. , LaPeruta R. , Korenowskl G. M. , Wnek G. E.
Published: March 2011

NLO-active polyurethanes were developed and optically characterized. We synthesized polyurethanes possessing large hyperpolarlzabilities, which are covalently attached or crosslinked to the polymer backbone. At ambient temperature the d33 values for poled polyurethanes were measured shortly after poling and 6 months later. The second-order nonllnearlty of the poled, crosslinked polyurethane is extremely stable decreasing slightly over 6 months. Also, using a polyurethane bearing a tricyanovinyl moiety as the host, we developed a nonlinear optical silver nanoparticle composite system. A third-order susceptibility was measured for the composite and was determined to be larger than that from the sum of its components. A chemical enhancement mechanism is speculated to be contributing to the large optical nonlinearities.
Materials Requirements for Electro-Optic Polymers (for electronic systems applications)
Authors: Lytel Rick , Lipscomb George F.
Published: March 2011

The field of electro-optic (EO) polymer materials for integrated optics has been developing rapidly during the past several years. Recent advances include the formulation of poled crosslinked epoxies and guest-host polyimides exhibiting thermal stability at temperatures significantly higher than that previously achieved with thermoplastic acrylate chemistry. These developments are an essential first step toward achieving practical materials exhibiting stability to manufacture, assembly, and end-use in modern electronic systems applications.

Despite these developments, there is still much basic research to be performed to achieve a practical EO polymer material system. A polymer material system for integrated optics consists of a set of three compatible materials: cladding polymers, passive core polymers, and active core polymers. The three materials should ideally be derived from the same base polymer so that the layers of the entire waveguide structure have nearly identical thermal, mechanical, chemical, electrical, and optical properties. In an ideal syst', the active core material would consist of passive materials highly loaded with aligned nonlinear optical moieties exhibiting large hyperpolarizabilities and suitable size and shape for thermal stability.

This paper provides a detailed review of the material requirements for EO polymer waveguide devices in electronic systems and points to new areas of research required for practical systems.
Dynamic Mechanical Behavior of Photo-Crosslinkable Nonlinear Optical Polymers
Authors: Marturunkakul S. , Lee J. Y. , Sengupta S. K. , Kumar J. , Tripathy S. K.
Published: March 2011

An easily processable photocrosslinking guest-host system with stable second order nonlinear optical properties using polyvinylcinnamate as a host polymer has been developed1–2. Samples were made as free standing films from photo-crosslinkable polyvinylcinnamate and different concentration levels of 3-cinnamoyloxy-4-[4-(N, N'-diethylamino)-2-cinnamoyloxy phenyl azo] nitrobenzene. Photo-crosslinking was carried out by ultraviolet radiation at the major wavelengths viz. 297 and 313 nm subsequent to corona poling. Dynamic mechanical properties of these polymer films were investigated. The changes in the storage and loss moduli, as well as relaxation behavior of the system upon crosslinking and poling are discussed.
Study of the Solid State Properties of an Organic Superconductor
Authors: Fainchtein Raul , D'arcangelo S. T. , Yangt S. S. , Cowant D. O.
Published: March 2011

We have synthesized cooper(I)di[bis(ethylenedithiolo)terathiafulvalene] bis(isothiocyanato), [(BEDT-TTF)2]+[Cu(NCS)2]using standard electrochemical methods. Single crystal samples of the compound were obtained and were found to have superconducting transition temperatures of 10.4 K, using DC conductivity measurements. [(BEDT-TTF)2+[Cu(NCS)2] shows a region between room temperature and 90 K which appears to be“semiconducting”

To characterize the structure of the samples we used Scanning Tunneling Microscopy (STM). STM supplied real-space images of the sample surface in accordance to its electronic structure. Ravy observed diffuse streaks between Bragg spots in his X-ray data of [(BEDT-TTF)2+[Cu(NCS)2]−, which he attributes to a stacking fault at every fourth repetition of the anion in the crystal structure [1]. STM shows no evidence for such disorder in [−(BEDT-TTF)2]+[Cu(NCS)2]−of the type proposed, and in fact illustrates direct evidence to the contrary. An intensity modulation in the STM data supports the possibility of a charge density wave commensurate with the lattice. This interpretation is consistent with the calculated Fermi surface which allows nesting of the wave vector and may explain the peculiar behavior of the temperature dependency of the conductivity data in the normal region.
Superpolaron Model of Metallic Polyacetylene
Authors: Takahashi A. , Yamamoto S. , Fukutome H.
Published: March 2011

We develop a new model for heavily doped metallic polyacetylene. An electron and a hole injected in a doped chain make localized defects called superpolarons (SP's) in the electronic order parameters (OP) in a charged soliton lattice. The SP's can make quantum intrachain translational motion and interchain transfer via dopant ions. They are stabilized by their quantum motions and SP pairs are spontaneously produced in a high doping regime. The SP's are Fermions and can be a Fermi liquid in the doping regime. Some metallic properties of the Fermi liquid of the SP' s are studied.
Synthesis of Heterocyclic Monomers Designed to Produce Conducting Polymer with Specific Redox Requisites and to Evaluate Stereochemical Factors Influencing the Conductivity
Authors: Berlin Anna , Brenna Elisabetta , Pagani Giorgio. A. , Sannicolo Franco , Zotti Gianni , Schiavon Gilberto
Published: March 2011

According to the “spacer” strategy we have previously proposed the monomers candidate for providing conductive polymers endowed with special properties should contain the polymerogenic rings (pyrrole or thiophene), as terminal units, linked to a central π-conjugatively active frame; we describe how it is possible in this way to control the redox potentials E of the polymers derived from such monomers. This control is beneficial because it is possible to increase the E° value of polypyrrole-type systems and decreases the E° value of polythiophene-type systems. Also, the “spacer”may be further functionalised and, being remote from the polymerisation site, cannot alter the conductivity characteristics typical of the polymer derived from the parent heterocycle (pyrrole or thiophene): such a functionalisation may provide the final, tailored, conductive polymer with special properties (e.g. solubility). If the central ring, acting as a spacer, is formed linking two positions of a di-heterocycle with a saturated chain, it is possible to partially control the twist angle between the heterocyclic units. Crystal and molecular structures have shown that dipyrrole units further linked through the nitrogen atoms are quite sensitive to the central ring size. With respect to the conductivity of unsubstituted polypyrrolc, the conductivity of the polymers derived from such monomers is dependent from the twist angle between the rings. This result is relevant to describe conditions of conjugation between the heterocyclic units of a monomer required to produce upon doping a conductive polymer.
Chemical and Electrochemical Doping of PPS in Sulfuric Acid
Authors: Arbizzani C. , Mastragostino M. , Dellepiane G. , Piaggio P.
Published: March 2011

ABSTRACT; Chemical and electrochemical dopings of poly(para-Phenylene SulfideHPPS) in the SO3/H2O system were followed by UV-VIS-NIR spectros-copy. The time evolution of the polymer's absorption bands in concentrated sulfuric acid clearly showed doping-swelling and solubilisation of the material. It was also found that highly concentrated sulfuric acid is necessary for the electrochemical doping of PPS.
The 1.5 eV Polaron Transition of Polyaniline: The Spectra Electrochemical Resolution into Sub-Bands
Authors: Liao Hong , Yang Sze Cheng
Published: March 2011

Polyaniline is an interesting conducting polymer because of its chemical stability and its reversible electrochromic response. A typical cyclic voltammogram [1, 2] in acidic solution shows two voltametric waves marked as d and h in Fig. 1. When the electrochemical potential of the polymer is between these two waves the polymer is a green colored electrical conductor. The polymer changes into a colorless insulator at -0.2 V and changes into a blue insulator when is oxidized beyond +0.7 V related to saturate calomel electrode (SCE).
Fabrication of an Electrically Conducting Full-Interpenetrating Polymer Network
Authors: Wang Yading , Rubner M. F.
Published: March 2011

Full-interpenetrating polymer networks (IPN) comprised of a styrene crosslinked polythiophene derivative and a crosslinked polystyrene network were synthesized and characterized. The IPNs were prepared by first crosslinking the pendant groups of a vinyl derivatized polythiophene with styrene monomer and then polymerizing and crosslinking styrene monomer in a swollen gel of the crosslinked polythiophene network. The doped forms of these full-IPNs reached conductivities as high as 0.5 S/cm. Conductivity stability studies showed that the IPNs are more stable than the as-prepared conjugated polymer at 40 °C but somewhat less stable at 80 °C.
Investigation of Polymer Relaxation after Deformation by Positron Annihilation
Authors: Tishin Sergey A. , Tsapovestsky Mihail I. , Tishin Vladimir A. , Kestelman Vladimir N.
Published: March 2011

The relaxation of polyimid films after the axial tension has been investigated by measuring life-time of positrons and angular correlation of annihilation photons. The nonmonotonic change of mean life-time while relaxing the free film has been found. Two range of changes of positron-sensitive properties can be seen: “rapid” relaxation for 4–5 hours (characterized by reducing life-time of short-lived component) and “slow” relaxation (characterized by reducing the intensity of long-lived component). The results of this investigation have been compared with those of measuring of sample density and dielectric losses. The possible explanations and the- changes of mechanizms of relaxation with the conditions of deformation and “the rest” of polymers are analyzed.
Molecular Precursors to Boron Nitride then Films: the Reactions of Diborane with Ammonia and with Hydrazine on Ru(0001)
Authors: Truong Charles M. , Rodriguez José A. , Wu Ming Cheng , Goodman D. W.
Published: March 2011

The coadsorption and reaction of diborane with ammonia and with hydrazine on Ru(0001) have been studied using X-ray photoelectron spectroscopy (XPS) and thermal desorption mass spectroscopy (TDS). Diborane is found to decompose to atomic boron and hydrogen upon adsorption at T>200K. Multilayers of diborane and ammonia, deposited at 90K on Ru(0001), react when annealed to 600K. The XPS results indicate that boron-nitrogen adlayers can be formed by this reaction. These boron-nitrogen films are boron-rich and.decompose at temperatures higher than 1100K. Our TDS studies reveal that hydrazine decomposes extensively to NH3, N2, N and H on Ru(0001). Due to its higher reactivity, boron-nitrogen films of B/N stoichiometric ratio near unity are obtained when hydrazine is used rather than ammonia. In our studies, these films were formed by either simultaneously dosing B2H6 and N2H4 at 450K or by coadsorption of the reactants at 90K and subsequent annealing to 450K. These studies have shown that diborane and hydrazine can be successfully used as molecular precursors in the low temperature deposition of boron nitride thin-films.
Advances in Modeling of the Chemical Vapor Infiltration Process
Authors: Starr Thomas L.
Published: March 2011

The technology of chemical vapor infiltration (CVI) has progressed dramatically over the past twenty-five years and stands now as the leading process for fabrication of high temperature structures using ceramic matrix composites. Modeling techniques also have advanced from extensions of catalyst theory to full 3-D finite element code with provision for temperature and pressure gradients. These modeling efforts offer insight into critical factors in the CVI process, suggest opportunities for further advances in process technology and provide a tool for integrating the design and manufacture of advanced components.

Early modeling identified the competition between reaction and diffusion in the CVI process and the resulting trade-off between densification rate and uniformity. Modeling of forced flow/thermal gradient CVI showed how the evolution of material transport properties provides a self-optimizing feature to this process variation.

“What-if” exercises with CVI models point toward potential improvements from tailoring of the precursor chemistry and development of special preform architectures.

As a link between component design and manufacture, CVI modeling can accelerate successful application of ceramic composites to advanced aerospace and energy components.
Effects of Fiber Orientation and Overlapping on Knudsen, Transition, and Ordinary Regime Diffusion in Fibrous Substrates
Authors: Tomadakis Manolis M. , Sotirchos Stratis V.
Published: March 2011

We prescnt effective diffusion coefficients of gases in porous media whose structure can be represented as an assemblage of cylindrical fibers, such as the media used as substrates in chemical vapor infiltration. Structures consisting of non-, partially, or freely overlapping fibers of various orientation distributions are considered, and effective diffusion coefficients are computed by means of a Monte Carlo simulation scheme. In order to be able to examine the interrelation of ordinary, transition, and Knudsen diffusivities and tortuosities, computations are carried out over the whole diffusion regime, i.e., from bulk to Knudsen. Our simulation results are compared with variational bounds and experimcntal values of tortuosity of fibrous beds reported by other investigators.
MOCVD Growth of Copper and Copper Oxide Films from Bis-β-Diketonate Complexes of Copper. The Role of Carrier Gas on Deposit Composition.
Authors: Rees William S. , Caballero Celia R.
Published: March 2011

An examination of thermal chemical vapor deposit elemental composition by EDAX has been completed for material films grown from Cu(acac)2 and Cu(tmhd)2 (acac = pentane-2,4-dionate; tmhd = 2,2,6,6-tetramethylheptane-3,5-dionate), using both hydrous and anhydrous carrier gas steams each of reducing (H2), inert (H2), and oxidizing (O2) composition.
Deposition and Characterization of Metalorganic Chemical Vapor Deposition ZrO2 Thin Films Using Zr(Thd)4
Authors: Si Jie , Peng Chien H. , Desu Seshu B.
Published: March 2011

Excellent quality ZrO2 thin films were successfully deposited on single crystal silicon wafers by metalorganic chemical vapor deposition (MOCVD) at reduced pressures using tetrakis(2,2,6,6—tetramethyl—3,5—heptanedionato) zirconium, [Zr(thd)4]. For substrate temperatures below 530°C, the film deposition rates were very small (≤ 1 nm/min). The film deposition rates were significantly affected by: (1) source temperature, (2) substrate temperature, and (3) total pressure. As—deposited films are stoichiometric (Zr/O = 1/2) and carbon free. Furthermore, only the tetragonal ZrO2 phase was identified in as—deposited films. The tetragonal phase transformed progressively into the monoclinic phase as the films were subjected to high temperature post—deposition annealing. The optical properties of the ZrO2 thin films as a function of wavelength, in the range of 200 nm to 2000 nm, are reported. The measured value of the dielectric constant of the as—deposited ZrO2 films is around 19 in the frequency range of 5 kHz to 1000 kHz.
Kinetic Characteristics of Si3N4 CVD
Authors: Lee W. Y. , Strife J. R. , Veltri R. D.
Published: March 2011

The CVD of Si3N4 from SiF4 and NH3 gaseous precursors was studied using a hotwall reactor in the temperature range of 1340 to 1490°C. The effects of temperature, time, flow rate, and SiF4/NH3 molar ratio on deposition rate and axial and radial deposition profiles were identified. The decomposition characteristics of pure NH3 and SiF4 were studied utilizing mass spectroscopy and compared to thermodynamic predictions.
Effects of Silicon Ion Implantation upon Thin Gate Oxide Integrity
Authors: Lee G. -S. , Park J. -G. , Choi S. -P. , Shin C. -H. , Sun Y. -B. , Kwak Y. -S. , Shin C. -K. , Smith W. L. , Hahn S.
Published: March 2011

In this study, using oxide breakdown voltage and time-dependent-dielectric breakdown measurements, thermal wave modulated reflectance and chemical etching/optical microscopy, we investigated effects of Si ion implantation upon formation of D-defects and thin gate oxide integrity. Our data show that addition of Si ion implantation with a dose of up to 1013 ions/cm2 improves oxide integrity if the implantation is done at a certain step just before sacrificial oxidation in the Mb DRAM process. However, no improvement in oxide integrity is observed when the same implantation is done on the virgin wafer surfaces at the start of the same Mb DRAM process. We discuss our hypothesis that the improvement in oxide integrity is due to a reduction in the D-defect density in the near-surface region of the wafer.
In-Situ Quality Control of the Production of Semiconductor Devices by Microwave Photoconductivity Measurements
Authors: Swiatkowski C. , Sanders A. , Kunst M. , Seidelmann G. , Haffer C. , Emmelmann K.
Published: March 2011

The application of transient photoconductivity measurements in the microwave frequency range to the characterization of semiconductors and semiconductor devices is analyzed. Quality control and in-situ optimization are discussed from a more general point of view and as a concrete example the optimization of the deposition of amorphous silicon films is presented.
Simulation of Sintering Experiments in Single-Mode Cavities
Authors: Chapman B. , Iskander M.F. , Smith R. L. , Andrade O. M.
Published: March 2011

The use of single-mode cavities has been recognized as a viable technique for sintering and joining ceramics and for creating microwave plasma for materials processing. It is often reported, however, that tuning these cavities at lower and higher temperatures critically depends on the types of materials being processed, the variation of ε* as a function of temperature, the size and shape of samples, and the overall heating system configuration with and without insulation.

In this paper we use the finite-difference time-domain technique to address the performance of the single-mode cavity heating system under a wide variety of heating conditions and system configurations. Specifically, practical issues such as limiting values of sample sizes, the dependence of optimal sample sizes on the complex permittivity of materials under test, the role of sample shape on enhancing uniformity of heating patterns, and various tradeoffs involved in utilizing various cavity modes and/or SiC rods as stimulus for heating large samples are evaluated.
Single Frequency Microwave Dielectric Heating and Measuring
Authors: Tian B.Q. , Tinga W.R. , Xi W.
Published: March 2011

Traditional microwave heating and measuring are mostly conducted using two different channels, i.e., a single frequency high power channel for heating and a sweeping frequency low power channel for measuring. Here, a different single frequency system is discussed, by which heating and measuring are conducted simultaneously using one high power source. The theoretical basis emphasizing Q determination at a single frequency is presented. A re-entrant resonator serves as the applicator. Without the normally required swept frequency channel, the experimental system is greatly simplified.
Steady State Temperature Profile in a Sphere Heated by Microwaves
Authors: Barmatz M. , Jackson H.W.
Published: March 2011

A new theory has been developed to calculate the microwave absorption and resultant temperature profile within a sphere positioned in a single mode rectangular cavity. This theory is an extension of a total absorption model based on Mie scattering results. Temperature profiles have been computed for alumina spheres at the center of a rectangular cavity excited in the TM354 mode. Parametric studies reveal significant structure in those profiles under special conditions that are associated with electromagnetic resonances inside the spheres. Anomalous behavior similar to thermal runaway occurs at moderate temperatures when there is enhanced absorption associated with resonant conditions in the sphere.
Fullerenes Doped with Thallium Alloys
Authors: Kraus M. , Baenitz M. , GÄrtner S. , Vieth H.M. , Werner H. , SchlÖgl R. , KrÄtschmer W. , Kanowski M. , Thommen V. , GÜntherodt H.-J. , LÜders K.
Published: March 2011

Prompted by earlier work showing that graphite intercalation compounds form superconducting ternary compounds in which thallium plays an important role C60 has been doped with Tl-alloys. Results of dc-magnetization, ac-susceptibility, X-ray analysis and NMR investigations will be presented.
Neutron Spectroscopy of Superconducting Fullerides
Authors: Prassides Kosmas , Christides Christos , Tomkinson John , Rosseinsky Matthew J. , Murphy D. W. , Haddon Robert C.
Published: March 2011

The phonon spectra of pristine fullerene, superconducting K3C60 and saturation-doped Rb6C60 measured by inelastic neutron scatteringin the energy range 2.5 - 200 meV at low temperatures reveal substantial broadening of five-fold degenerate Hg intramolecular vibrational modes both in the low-energy radial and the high-energy tangential part of the spectrum. This provides strong evidence for a traditional phonon-mediated mechanism of superconductivity in the fullerides but with an electron-phonon coupling strength distributed over a wide range of energies (33-195 meV) as a result of the finite curvature of the fullerene spherical cage.
Growth and Characterization of InxGa1−xP(x≤0.38) on GaP(1OO) with a Linearly Graded Buffer Layer by Gas-Source Molecular Beam Epitaxy
Authors: Chin T. P. , Chang J. C. P. , Kavanagh K. L. , Tu C. W. , Kirchner P. D. , Woodall J. M.
Published: March 2011

InxGa1−xP(x>0.27) grown on a GaP substrate has a large direct-bandgap, which is suitable for yellow light emission on a transparent substrate. Because of the large lattice mismatch, usually a thick (10–20 μm) graded buffer layer was required to reduce the threading dislocation density. In this work we report that a thin (1.2 μm for x≃0.35), linearly graded buffer layer can filter out dislocations effectively. The structures were grown by gas-source molecular beam epitaxy. Reflection high-energy electron diffraction (RHEED) intensity oscillations and X-ray double-crystal diffraction were used to control and determine the composition, respectively. Threading dislocations are well confined in the buffer layer, as shown under transmission electron microscopy. Dislocation loops injected into the substrate were observed, similar to those observed in the Six Ge1−x/Si system. X-ray analysis also shows that the 3% mismatched buffer layer is fully relaxed. This relaxed buffer layer then can serve as a substrate for further growth. Homojunction and heterojunction light emitting diodes were fabricated to demonstrate the material quality.
Carbon Incorporation in Gaas grown by UHVCVD Using Trimethylgallium and Arsine
Authors: Park Seong-Ju , Ro Jeong-Rae , Sim Jae-Ki , Lee El-Hang
Published: March 2011

We present results of a study on the effect of unprecracked arsine(AsH3) and trimethylgallium(TMGa) on carbon incorporation in UHVCVD(Ultra High Vacuum Chemical Vapor Deposition) grown GaAs epilayers on GaAs(100). Three distinct temperature-dependent regions of growth rates were identified as growth temperature was increased from 570 to 690°C. The growth rates were also strongly dependent on V/III ratio in a range of 5 to 30, which clearly indicates that the growth rate is determined by the amount of arsenic adsorbed on the surface at low V/III ratio and adsorption of TMGa or decomposition process at high V/III ratio. Hall concentration measurements and low temperature photoluminescence data show that the films are all p-type and their impurity concentrations are reduced by two orders of magnitude compared to those of epilayers grown by CBE(Chemical Beam Epitaxy) which employs TMGa and arsenic(precracked arsines) as source materials. Our results indicate that the hydrogen atoms dissociated from adsorbed arsine may remove hydrocarbon species resulting in a significant drop in hole concentration.
Time-Resolved Reflectivity Study of Solid-Phase Epitaxial Regrowth in Relaxed and Strained Si1−xGex Epilayers
Authors: Haynes T. E. , Lee C. , Jones K. S.
Published: March 2011

The rate of solid-phase epitaxial regrowth has been studied using time-resolved reflectivity in three different types of SiGe/Si epilayers amorphized by ion implantation. In two of these cases, the alloy epilayer contained either 12% or 20% Ge, and the amorphization depth was greater than the thickness (2000 Å) of the SiGe alloy layer. Time-resolved reflectivity measurements showed that the rate of regrowth was not constant in these two cases, but first decreased after passing the SiGe/Si interface, and then increased. The minimum regrowth rate occurred closer to the SiGe/Si interface in the epilayers with the larger Ge atomic fraction. In the third type of sample, the alloy epilayer thickness was ∼7μm, so that the initial epilayer (15% Ge) had the lattice constant of the bulk alloy. Furthermore, amorphization and regrowth occurred entirely within the relaxed alloy layer. In this case, the regrowth rate was constant. The composition dependence of the regrowth-rate transient in the strained layers is discussed in the context of a ‘critical-thickness’ model of strain relaxation.