bluuebunny/crossref_metadata_2025 huggingface dataset:
Manufacturing and Performance Assessments of Several Applications of Electrotextiles and Large-Area Flexible Circuits
Authors: Cadogan David P. , Shook Lauren S.
Published: April 2011

Numerous applications of electrotextiles and flexible circuits have been identified that can advance systems performance for many commercial, military, and aerospace devices. Several novel uses of electrotextiles have been developed for lab testing, while others have been utilized in products on the commercial market, as well as items that have flown in space. ILC Dover, Inc. has utilized conductive fibers in various inflatable and tensile structures for signal transmission and electrostatic charge protection. Conductive and pressure sensitive textiles have been incorporated in the advanced development space suit (I-Suit) as switch controls for lights and rovers, and as signal transmission cables. Conductive fibers have been used in several stitched applications for electrostatic charge dissipation. These applications include large pharmaceutical containment enclosures where fine potent powders are being captured for transfer between manufacturing facilities, as well as impact attenuation airbags used in landing spacecraft on the surface of Mars. In both cases, conductive threads are uniquely located in seams and panel locations to gather and direct charge through surface fibers and panel interconnects. Conductive fibers have also been utilized in a conformal Sensate Liner garment for the identification of wound locations and medical sensor signal transmission for soldier health monitoring while on the battlefield. The performance challenges of these structures require a careful, systematic application of electrotextiles because of the flexing, straining, and exposure of the materials to harsh environments. ILC has also been developing “gossamer” spacecraft components utilizing unique materials and multi-functional structures to achieve extremely low mass and low launch volumes. Examples of large deployable structures featuring very thin, large flexible circuits for use in space include synthetic aperture radar (SAR) antennas, communications antenna reflectarrays, and active variable reflectance solar sails. Design and materials challenges of electrotextile and large-area flexible circuit membrane structures as demonstrated in engineered applications will be discussed in this paper.
Tailored Nanofiber Morphologies Using Modulated Electrospinning for Biomedical Applications
Authors: Lin David Y. , Johnson Michael A. , Vohden Richard A. , Chen Deborah , Martin David C.
Published: April 2011

The process of electrostatic fiber formation, or electrospinning, was used to generate polymer filaments with diameters in the 50–200 nm range. We have shown that in addition to process parameters such as solution concentration, spinning voltage, and deposition distance, an oscillating electric field can also influence the morphology of the electrospun nanofibers. Specifically, effects of the oscillating field strength and frequency, spinning voltage, and deposition distance on fiber diameter as well as size and number density of the beaded structures in the fibrous thin films are examined.

The results of our study demonstrate that modulated field potential produces more uniform fibers. Increasing either the oscillating field strength or frequency yields more uniform average fiber diameter. Also, for systems with the “beads on a string” fiber morphology, increasing the oscillating field strength produces more uniform bead sizes.

The ability to tailor fiber morphology using an oscillating electric field has promising implications in a wide range of applications including controlled-release drug delivery systems and biocompatible implants. We show here the potential of using electrospun nanofibers as a porous template for growing fuzzy conductive polymers to modify the surface of a neural recording microelectrode device. These hairy nanostructures can increase signal transport and mediate the mechanical property differences between the device and the soft brain tissues.
High Performance Polymer Thin Film Transistors Array Printed on a Flexible Polycarbonate Substrate
Authors: Park Sung Kyu , Han Jeong In , Moon Dae Gyu , Kim Won Keun , Kim Yong Hoon
Published: April 2011

High performance poly (3-hexylthiophene) (P3HT) thin film transistors (TFTs) array was fabricated on a polycarbonate substrate by micro-contact printing method. A thin polyimide layer (40 nm) was applied before silicon oxide deposition to improve the electrical properties of the TFT device. Also, the effects of O2 plasma treatment on the field effect mobility and output current behaviors of the devices were investigated. By plasma treatment, the surface roughness of gate dielectric was improved which accounts for the increased field effect mobility and the hole Schottky barrier height in electrode/semiconductor interface was lowered resulting in large drain current in the device. Based on the experiments, we fabricated P3HT TFTs array with 0.025 cm2/V·s in saturation field effect mobility and on/off current ratio of 103 ∼ 104 on a polycarbonate substrate.
Kondo-excitons and Auger processes in self-assembled quantum dots
Authors: Govorov A. O. , Karrai K. , Warburton R. J. , Kalameitsev A. V.
Published: April 2011

We describe theoretically novel excitons in self-assembled quantum dots interacting with a two-dimensional (2D) electron gas in the wetting layer. In the presence of the Fermi sea, the optical lines become strongly voltage-dependent. If the electron spin is nonzero, the width of optical lines is given by kBTK, where TK is Kondo temperature. If the spin is zero, the exciton couples with the continuum due to Auger-like processes. This leads to anticrossings in a magnetic field. Such states can be called Kondo-Anderson excitons. Some of the described phenomena are observed in recent experiments.
Long-Lifetime Nonlinear Absorption of PbS Quantum Dots
Authors: Huang Feiran , Filin Aleksey , Rao Pratima G.N. , Doremus Robert H. , Persans Peter D.
Published: April 2011

We have fabricated PbS particles in glass of average size from 1.2 nm to 3 nm. This allows us to tune the energy of the lowest electron-hole pair transition from 1.7 eV to 0.8 eV respectively. Optical absorption spectra show a pronounced quantum peak, implying a narrow size distribution. We have performed pump-probe spectroscopy where the probe is cw and the pump is nanosecond; this allows us to investigate a wide time scale. We have observed bleaching of the lowest quantum peak with lifetimes of ∼2 microseconds. We interpret this in terms of trapped carriers. Phenomenological description of observed effect is also presented.
Resonant Raman Scattering by Strained and Relaxed Ge Quantum Dots
Authors: Milekhin Alexander G. , Nikiforov Alexander I. , Ladanov Mikhail , Pchelyakov Oleg P. , Tenne Dmitri A. , Schulze Steffen , Zahn Dietrich R.T.
Published: April 2011

Fundamental vibrations in Ge/Si structures with strained and relaxed Ge quantum dots (QDs) grown by molecular beam epitaxy were investigated using resonant Raman spectroscopy. Transmission electron microscopy experiments show that the strained Ge QDs are typical “hut clusters” with base size of 15nm and a height of 2nm. A two mode distribution in size (100–200nm and 3–6nm) is found for relaxed QDs. The Raman efficiencies of the Ge optical phonons as a function of excitation energy reveal maxima at 2.35–2.41eV attributed to the E0 resonance in Ge QDs due to electronic confinement. The frequency positions of optical phonons localized in Ge “hut clusters” under non-resonant conditions correspond to fully strained Ge QDs while the frequency position of optical phonons in relaxed Ge QDs corresponds to the value in bulk Ge. With increasing excitation energy (2.5–2.7eV) the position of the Ge optical phonons shifts downwards due to size-confinement effect of optical phonons in strained and relaxed Ge QDs, indicating the presence of a QD size distribution in Ge dot structures.
Optical Detection of the Charging of InAs Quantum Dots with Different Backgate Configurations
Authors: Su B. , Karsten L. , Schüller C. , Heitmann D. , Zhukov A. A. , Heyn Ch. , Hansen W.
Published: April 2011

We investigate self-assembled InAs quantum dots by photoluminescence (PL) and capacitance spectroscopies. By employing specially designed backelectrode configurations, we can control the number of electrons, which are confined in the quantum dots. With PL experiments we study the dependence of the s-s transition on the electron occupation of the quantum dots. We observe a characteristic redshift of the s-s transition when the s-shell is filled with electrons. However, if the p-shell of the quantum dots starts to fill, the samples with different backelectrode configurations show a different behavior. In one type of samples, the signal stays redshifted, while in the other it blueshifts again. The effect can be explained by different hole capture processes in both types of samples.
Local Strain Effects in Near-Field Spectra of Single Semiconductor Quantum Dots.
Authors: Mintairov A. M. , Blagnov P. A. , Kovalenkov O. V. , Li C. , Merz J. L. , Oktyabrsky S. , Sun K. , Tokranov V. , Vlasov A. S. , Vinokurov D. A.
Published: April 2011

Experimental and theoretical investigations of high-energy shifts of single InAs, InGaAs, InAlAs and InP quantum dot (QD) emission lines induced by contact pressure exerted by a near-field optical fiber tip are reported. “Pressure” coefficients of 0.65–3.5 meV/nm have been measured for ground state emission lines in agreement with numerical calculations. We show that the observed increase of the tip-induced energy shift with increasing aperture diameter is caused by a decrease of the uniaxial strain component. We also report the effect of emission instability of single QD emission intensity under tip-induced pressure.
Mechanisms of Visible Photoluminescence from Size-Controlled Silicon Nanoparticles
Authors: Makino Toshiharu , Suzuki Nobuyasu , Yamada Yuka , Yoshida Takehito , Umezu Ikurou , Sugimura Akira
Published: April 2011

We have observed visible photoluminescence (PL) spectra (peak energy: 3.1 eV) of size-controlled silicon (Si) nanoparticles annealed in oxygen gas. The PL peak energy did not depend on the temperature, and the PL lifetime was relatively fast (on the order of nanoseconds). It was inferred that the visible PL was attributed to localized states in the oxidized surfaces of size-controlled Si nanoparticles. We also observed the PL excitation spectra and studied the excitation process. In order to elucidate mechanisms of the visible PL, excitation and recombination processes are discussed.
Synthesis and size control of Si nanocrystals by SiO/SiO2 superlattices and Er doping
Authors: Heitmann J. , Kovalev D. , Schmidt M. , Yi L.X. , Scholz R. , Eichhorn F. , Zacharias M.
Published: April 2011

The synthesis of nc-Si by reactive evaporation of SiO and subsequent thermal induced phase separation is reported. The size control of nc-Si is realized by evaporation of SiO/SiO2 superlattices. By this method an independent control of crystal size and density is possible. The phase separation of SiO into SiO2 and nc-Si in the limit of ultrathin layers is investigated. Different steps of this phase separation are characterized by photoluminescence, infrared absorption and transmission electron microscopy measurements. The strong room temperature luminescence of nc-Si shows a strong blueshift of the photoluminescence signal from 850 to 750 nm with decreasing crystal size. Several size dependent properties of this luminescence signal, like decreasing radiative lifetime and increasing no-phonon transition properties with decreasing crystal size are in good agreement with the quantum confinement model. Er doping of the nc-Si shows an enhancement of the Er luminescence at 1.54 μm by a factor of 5000 compared to doped SiO2 layers. The decreasing transfer time for the nc-Si to Er transition with decreasing crystal size can be understood as additional proof of increasing recombination probability within the nc-Si for decreasing crystal size.
Transport Properties and Observation of Semimetal-Semiconductor Transition in Bi-based Nanowires
Authors: Lin Yu-Ming , Cronin Stephen B. , Rabin Oded , Ying Jackie Y. , Dresselhaus Mildred S.
Published: April 2011

Temperature-dependent resistance measurements of Bi-related nanowire arrays with different wire diameters and Sb concentrations are performed. The variation in the measured R(T) curves of these nanowires is closely related to the unique semimetal-semiconductor transition in Bi, and the results are explained by theoretical simulations. It is found that the special feature of the maximum in the resistance ratio R(10 K)/R(100 K) can be employed to experimentally identify the conditions for the semimetal-semiconductor transition.
Thermoelectric Nanowires By Template Synthesis: Fabrication, Contacts and Properties
Authors: Rabin Oded , Lin Yu-Ming , Cronin Stephen B. , Chen Gang , Dresselhaus Mildred S.
Published: April 2011

Using the technique we have developed to grow porous anodic alumina (PAA) templates on the surface of silicon wafers, we have fabricated arrays of nanowires of thermoelectric materials. By this method we can control both (1) the in-plane geometry by the design of the template and the substrate, and (2) the out-of-plane dimension by control over the electrochemical nanowire growth process. We use several straightforward methods to make electrical contacts to the nanowires. Our transport studies show that both the structure of the nanowire and the contact region have a strong influence on the observed properties of the arrays.
Synthesis by Self-Assembly of Iron-Cobalt Nanoalloys
Authors: Zubris Melissa A. , Tannenbaum Rina
Published: April 2011

In this paper we are proposing the synthesis of iron and cobalt nanoalloys via the codecomposition of iron and cobalt carbonyl precursors in the presence of polystyrene as the surface stabilizing agent. In order to form iron-cobalt nanoalloys with no preferential aggregation of metal atoms resulting in phase segregation, the decomposition kinetics of the iron pentacarbonyl and dicobalt octacarbonyl precursors had to be firmly established. The kinetics of cobalt cluster formation has been thoroughly investigated, but data for iron pentacarbonyl decomposition is relatively scarce. To fully understand the formation of the iron nanoclusters, a kinetic study was performed by varying carbonyl concentrations and reaction media in order to establish reaction order and rate constants. Our results suggest this decomposition to be a higher order process (not first order as previously assumed), with a complicated intermediate mechanism, which has been postulated and experimentally verified. By using this kinetic data, we will be able to predict the necessary conditions for the creation of new in-situ iron-cobalt nanoalloys using carbonyl precursors.
Thermally Evaporated AgGaTe2 Thin Films For Low-Cost p-AgGaTe2/n-Si Heterojunction Solar Cells
Authors: Mandal Krishna C. , Smirnov Anton , Roy Utpal N. , Burger Arnold
Published: April 2011

High quality polycrystalline AgGaTe2 (AGT) thin films were deposited on H-terminated n-Si substrates by controlled thermal evaporation method at various substrate temperatures (300–500 K). X-ray diffraction (XRD) studies showed that all films were of chalcopyrite structure and while the films were deposited at 300 K had random grain orientation, the films deposited at higher substrate temperature (500 K) showed preferred (112) orientation. The composition of the films was thoroughly analyzed by energy dispersive x-ray analysis (EDAX) and by x-ray photoelectron spectroscopy (XPS) with and without argon ion etching. The ultraviolet-visible (UV-Vis) spectra showed the optical bandgap of 1.16 eV, with sharper band edge for the films deposited at higher temperature. The films were p-type and the resistivities of the as deposited at 300 and 500 K were 2.8 × 104 and 1.2 × 103 Ω. cm respectively. p-AgGaTe2/n-Si heterojunction solar cells, having an active area of 0.12 cm2 and without any antireflection coating, were fabricated. It was observed that the films deposited at 500 K produced junctions with improved photovoltaic properties. Under solar simulator AM1 illumination, the improved junctions exhibited an efficiency of 4.8% whereas the films deposited at 300 K showed an efficiency of 2.1%.
The Energy Band Structures of Cd1-xZnx Te Polycrystalline Thin films and their Applications for Photovoltaic Devices
Authors: Jiagui Zheng , Lianghuan Feng , Ye Shao , Yaping Cai , Jingquan Zhang , Wei Cai , Liii Wu , Daoiin Cai , Wenjian Len , Jumu Zhu
Published: April 2011

In the paper, Cd1-xZnxTe polycrystalline films have been prepared by co-evaporation, which can control the zinc content, using CdTe and ZnTe as the evaporation sources. The cubic phase in these films as-deposited and annealed has been demonstrated by XRD. The XRD peaks of Cd1-xZnxTe films are always between the corresponding peaks of CdTe and ZnTe. According to Vegard Formula, x values of Cd1-xZnxTe films have been confirmed from XRD data, which shows that both the calculated and experimental x values are almost identical. The optical transmission of Cd1-xZnxTe films has been measured, and the optical energy gaps have been calculated from the transmission. The band gaps vary in a quadratic way with x values, and increase with annealing temperatures. When application of Cd1-xZnxTe film as a buffer of around 80nm thick in CdS/CdTe solar cells, the structure of the cells becomes CdS/CdTe / Cd1-xZnxTe / ZnTe:Cu and their average conversion efficiency is improved by 40% where x is in the range of 0.55 to 0.65. The mentioned above results are discussed.
Effect of pressure-enhanced single step annealing on the silicon photoluminescence
Authors: Binetti S. , Le Donne A. , Emtsev V.V. , Emtsev V.V , Pizzini S.
Published: April 2011

The effect of single-step annealing under GPa hydrostatic pressures on the photoluminescence of Cz silicon samples has been investigated at 450, 650 and 1000°C. It has been demonstrated that the effect of applied pressure begins to be detectable at 650°C and significant at 1000°C, where not only the effect of the applied pressure but also that of the dopants was clearly evidenced. In the first case the presence of a gap level associated to self-interstitial clusters could be argued, while in the second case both the oxide segregation and the dislocation formation was shown to be enhanced by the pressure and selectively addressed to the type of doping, respectively.
Complex magnetic response in magnetic tunnel junctions determined via magnetic and transport measurements
Authors: Guerrero R. , Pryadun V. V. , Aliev F. G. , Villar R. , Martinez J. L. , Moodera J.
Published: April 2011

We have studied the low frequency complex magnetization dynamics in Co/Al2O3/Ni80Fe20 magnetic tunnel junctions (MTJs) at temperatures between 4.2K and 300K. The measurements were carried out by using two different experimental techniques. The first method probes directly magnetic properties via DC magnetization and AC susceptibility, while the second one measures AC magnetization dynamics of the ferromagnetic electrodes near the cross area, which is related to the tunnelling resistance.
Study of the Low Field Microwave Response in Yttrium Aluminates Dilutely Doped with Manganese
Authors: Rakhimov Rakhim R. , Jones David E. , Loutts George B.
Published: April 2011

Microwave response near zero magnetic field was observed in YAlO3 and CaYAlO4 crystals dilutely doped with Mn in concentration ranging from 0.05 to 2 atomic %. The response is due to non-resonant microwave absorption, which co-exists with normal electron paramagnetic resonance (EPR) absorption due to different paramagnetic valence states of manganese. Mn2+ and Mn4+ charge states were identified in Mn-doped YAlO3, and Mn2+, Mn4+ and Mn5+ in Mn-doped CaYAlO4. The low field response has the opposite phase with respect to the paramagnetic absorption. This shows that Mn-doped YAlO3 and CaYAlO4 exhibit magnetically induced microwave absorption, which has a minimum at zero magnetic field and increases with the applied magnetic field. This effect is similar to microwave magneto-resistance effects observed in manganite perovskites, where spin-dependent electron tunneling occurs between ferromagnetically coupled manganese ions in different valence states. We show, however, that in the present case of diluted paramagnetic systems, magneto-induced microwave losses are due to intramolecular spin-dependent tunneling, where central paramagnetic ion does not change its charge state and spin-dependent charge migration occurs in the first coordination sphere of paramagnetic ion. Evidences are presented that this ion is Mn2+ exhibiting the highest electron spin S = 5/2.
Metal/Self-Assembled Monolayer/Metal Junctions for Magnetoelectronic Applications.
Authors: Ovchenkov Y. A. , Zhang Chunjuan , Redepenning J. , Doudin B.
Published: April 2011

Metal/organic self-assembled monolayer/metal junctions were investigated for junction areas 10-2 to 102 μm2. Several types and thickness of monolayers are investigated, and magnetic electrodes were made. Electroless deposition was used to make the top metal without disrupting the organic film. This deposition is activated with Pd clusters obtained by evaporation or by chemical reduction of a Pd-based catalyst. This method allows us to obtain a high yield of junctions that are not electrically shorted and are mechanically and electrically stable over a wide temperature range. Low-temperatures investigations reveal strong non-linearity in the IV curves and an increase of resistance with decreasing temperature. Zero bias anomalies observed at low temperatures are attributed to a Coulomb blockade associated with the Pd clusters.
Fabrication of MISFET exhibiting normally-off characteristics using a single-crystalline InGaO3(ZnO)5 thin film
Authors: Nomura K. , Ohta H. , Ueda K. , Kamiya T. , Hirano M. , Hosono H.
Published: April 2011

Transparent metal-insulator-semiconductor field-effect transistors (MISFETs) were fabricated using a single-crystalline thin film of an n-type transparent oxide semiconductor, a homologous compound InGaO3(ZnO)5, grown by a reactive solid phase epitaxy method. The transparent MISFET exhibited good performances with “normally-off characteristics”, “an on/off current ratio as large as 105” and “insensitivity to visible light”. Field-effect mobility was about 2 cm2(Vs)-1, which is larger than those reported previously for MISFETs fabricated in transparent oxide semiconductors. These improved performance is thought to result from the low defect density and intrinsic-level carrier concentration of the single-crystalline InGaO3(ZnO)5 film.
Evaporative Deposition of Aluminum Single Crystals
Authors: Jankowski Alan , Vallier Bob , Bliss Ann , Hayes Jeffrey
Published: April 2011

The classic zone model for growth of evaporated deposits serves a starting point for selecting the process conditions to produce dense crystalline coatings. The columnar structure intrinsic to vapor deposits evolves from the nano-to-millimeter scale as the substrate temperature increases to the melting point. In this paper, the deposition conditions are reviewed for the evolution of a single crystal structure in metal coatings. Experimental results are presented for the electron-beam deposition of aluminum coatings up to 100 μm in thickness. The deposition of a single crystal occurs when the coating temperature exceeds 530 °C, i.e. 85% of the absolute melt point.
Metal-Oxide Interfacial Evolution in Thermally Grown Oxide Films
Authors: Mencer D. E. , Hossain M. A. , Kesmez M. , Naugle D. G. , Cocke D. L.
Published: April 2011

The metal-oxide interface is a crucial zone in the fundamental understanding of oxide growth and growth instabilities. However, obtaining fundamental information on this buried interface has proven extremely difficult using modern surface and interfacial characterization methods. Using copper oxide growth over copper metal, examined between RT and 250°C, as a model system, we have delineated the fundamental physical chemical processes that determine the oxide growth and instabilities at the metal-oxide interface. Application of controlled thermal growth studies in combination with linear sweep voltammetry (LSV) has allowed experimental access to the metal-oxide interface with surprising characterization capabilities. The methodologies involved and the physical chemical phenomena will be discussed in context of the application of modern surface characterization methods including pulsed field desorption mass spectrometry, XPS combined with depth profiling and angular resolved methods. The evolution and alteration of the precursor oxide that develops at low temperatures <75°C will be explained on the basis of previously observed metal oxide interfacial phenomena involving coupled bulk and surface reactions. The nature of the interfacial zone will be discussed with electron transfer and oxygen absorption models that are applicable to oxide growth and instabilities in general.
Spontaneous Oscillations During The Electrodeposition of Gold Thin Films
Authors: Ravaine Serge , Saliba Raphaël , Mingotaud Christophe , Argoul Françoise
Published: April 2011

The galvanostatic electrodeposition of two-dimensional (2D) gold films along the surface of aqueous hydrogen tetrachloroaurate solutions coated by a positively charged dimethyldioctadecylammonium (DODA) monolayer is reported. When a constant current is applied to the working electrode, a transition between two-dimensional (2D) growth and three-dimensional (3D) thickening of the deposits is observed. This event occurs when the current density is sufficiently small to allow the 3D process to consume all the injected electrical charges. The application of a current ramp with a rate such as the current density remains during the whole growth close to the limiting value separating the two growth regimes induces the appearance of spontaneous oscillations between the regimes of 2D and 3D growth. Deposits with a well-defined terraced structure are then obtained.
An MBE and Modeling Study of Pulsed Growth on Ge(001)
Authors: Gallivan M. A. , Atwater H. A.
Published: April 2011

Ge molecular beam epitaxy (MBE) and kinetic Monte Carlo (KMC) simulations are used to study time-varying processing parameters and their effect on surface morphology. We focus here on Ge growth on highly-oriented Ge(001) substrates with reflection high-energy electron diffraction (RHEED) as a real-time sensor. KMC simulations are used as the physical model, and physical parameters are determined from growth under pulsed flux. A reduced version of the simulations is generated, and temperature trajectories are computed that minimize surface roughness subject to experimental constraints.
Surfactant Mediated Epitaxial Growth of Co on Au(111) Surface
Authors: Kamiko Masao , Oh Sang-Mun , Chihaya Hiroaki , Mizuno Hiroyuki , Xu Junhua , Yu Lihua , Kojima Isao , Yamamoto Ryoichi
Published: April 2011

We have chosen Bi as the surfactant atom in the heteroepitaxial growth of Co on Au(111). It was found that Bi induces layer-by-layer (LBL) growth at room temperature. With pre-deposition of 0.2 ∼ 0.8Å Bi on Au(111) prior to the evaporation of Co, more long-lasting RHEED intensity oscillations were observed and this implies that it induces the LBL growth of Co film. The result of the dependence of the growth behavior as a function of Bi layer thickness suggests that there is a suitable amount of Bi surfactant layer that induces the smoother LBL growth. A surface segregation of Bi was found at the top of surface and acts as a surfactant by promoting the interlayer transport.
Adsorption of water molecules on the surface of photo-catalyst: a first principles theoretical comparison between InVO4 and rutile TiO2
Authors: Oshikiri M. , Boero M. , Ye J.
Published: April 2011

The adsorption process of water molecules on the surface of InVO4 has been investigated via first principles molecular dynamics simulations and compared with that of the well-known rutile TiO2. We have found that the surface of InVO4 shows a remarked chemical reactivity whenever comes in contact with water and H2O molecules are often adsorbed dissociatively on its surface. The reaction proceeds spontaneously in a way similar to the case of TiO2 and does not require the overcoming of an activation energy barrier. The peculiar atomic connectivity of the InVO4 bulk crystal structure and the changes at the catalyst surface induced by the water adsorption are discussed and compared with the TiO2 system.
Hardness Indentation Studies On Metallic Glasses
Authors: Wesseling Paul , Lowhaphandu Peravudh , Lewandowski John. J.
Published: April 2011

Vickers micro-hardness indentations have been performed on a number of amorphous metals. The effects of changes in indentation load on the hardness and appearance of indents will be discussed for amorphous Al87Ni7Gd6. In addition, the effects of changes in test temperature on the micro-hardness and appearance of indentations in Vitreloy I are presented. A transition in deformation/flow character was detected with increasing test temperature for the Vitreloy I specimens. In addition, preliminary hardness data obtained at room temperature on an iron based metallic glass exhibited values in excess of 12 GPa without cracking.
Progress in Consolidation of Amorphous Zr-based Powder into Bulk Metallic Glass
Authors: Mathaudhu Suveen N. , Im Jae Taek , Barber Robert E. , Anderson Iver E. , Karaman Ibrahim , Ted K.
Published: April 2011

Equal channel angular extrusion (ECAE) is used to consolidate amorphous Vitreloy 106a (Zr58.5Nb2.8Cu15.6Ni12.8Al10.3) powder into bulk metallic glass. Consolidations are performed on gas atomized powder containing 1280 ppmw oxygen encapsulated in copper cans and 780 ppmw oxygen powder encapsulated in nickel cans in a 90° die-angle tool at temperatures above the glass transition temperature (Tg) but below the rapid crystallization temperature (Tx), in the supercooled liquid region (ΔT). Results show that V106a is successfully consolidated to nominal full density after one extrusion pass. Good particle-to-particle bonding and significant particle deformation are observed in the consolidated alloy. A lower oxygen content is beneficial due to the larger undercooled region and the additional time for processing. The low oxygen content material shows little change in thermal stability after being consolidated when compared to the original powder but fine interparticle cracks are observed in some of the consolidates. ECAE appears to be a viable method for consolidating amorphous metal powders into bulk amorphous metal.
Comparison between thermal and deformation-induced structural relaxation in atomic glasses
Authors: Nandagopal Magesh , Utz Marcel
Published: April 2011

Plastic yielding in glassy solids has been interpreted as a strain-biased relaxation process, or, equivalently, as a strain-induced glass transition. In the present work, the atomic motions caused by athermal plastic deformation of a binary Lennard-Jones glass are compared to thermal motion in the liquid in terms of the self part of the intermediate structure factor. We find that like at finite temperature, athermal plastic deformation leads to diffusive atomic motion at all length scales beyond about one interatomic distance, effectively promoting structural relaxation. The present approach allows to study the interplay of deformation-induced and thermal relaxation. Preliminary evidence is presented that these two processes occur independently of each other over a wide range of strain rates.
Risks and Uncertainties Associated With High-Level Waste Tank Closure
Authors: Esh David W. , Bradford Anna H. , Banovac Kristina L. , Jennifer Davis B.
Published: April 2011

Closure of tanks containing high-level radioactive waste (HLW) is a challenging problem involving potentially competing influences from economic, societal, and technological considerations. The U.S. Department of Energy (DOE) is faced with protecting public health and the environment while making economically responsible decisions. Risk (i.e., annual dose) is becoming more prominent as DOE's metric to evaluate the economic consequences of its decisions. Risks are assessed through modeling and calculations commonly known as performance assessment (PA). In the process of tank closure, the U.S. Nuclear Regulatory Commission (NRC) is typically consulted to perform an independent review of DOE's PAs.

The NRC staff developed a generic PA model, applicable to HLW tank closure, which NRC utilizes to complete its independent review. The model was developed using the generic simulation software, GoldSim, because of its probabilistic capabilities and its adaptability to different problems [1]. The NRC staff uses the resultant risk from the generic models to evaluate the reasonableness of performance assessment models submitted by DOE. Large differences in the estimates of risk between the generic PA model and the DOE PA would likely indicate a need for stronger technical basis for processes significantly contributing to annual dose (risk) reduction.
Leaching of americium-241, plutonium-238 and matrix elements from perovskite-based ceramics
Authors: Ochkin A. V. , Chizhevskaya S. V. , Archakova N. E. , Merkushkin A. O. , Petukhova I. A. , Mikhailenko N. P. , Stefanovsky S. V.
Published: April 2011

Perovskite-based ceramics ABO3 (A = La or Gd; B = Al or Fe) and a pseudobinary system: LaAlO3 + CaZrTi2O7 are promising matrices for immobilization of actinide fraction of HLW. The ceramic samples containing 241Am, 238Pu or 147Pm were prepared by cold pressing in pellets at 100–300 MPa and sintering at 1300–1500 °C. Leach rates of radionuclides and matrix elements (La, Gd, Al and Fe) from powders were measured using Soxhlet unit. Sintered ceramics in the series: LaAl1-xFexO3 were composed of perovskite phase. Ceramics in the compositional series xLaAlO3 + CaZrTi2O7 (0.4 ≤ x ≤ 6) consisted of perovskite, zirconolite, and baddeleyite at x = 0.4 and x = 0.7, and perovskite and baddeleyite at higher x values. Leach rate of radionuclides and matrix elements from all the ceramics were lower than 10-8 g·cm-2·day.
Selection of Matrices for Immobilization of Actinide Fraction of HLW
Authors: Ochkin A. V. , Stefanovsky S. V. , Rovny S. I.
Published: April 2011

HLW after the separation of U, Pu and Np contains two major radionuclide groups: fission products and TRU elements. The later ones are the most dangerous and should be separated in the special actinide fraction. This process has been realized at PA “Mayak”.

The composition of the actinide fraction depends on a separation method:

A. Radionuclides of Am and Cm with minor amounts of U, Np and Pu.

B. Radionuclides of Am and Cm with minor amounts of U, Np and Pu and also REEs.

C. Radionuclides of Am and Cm with minor amounts of U, Np and Pu and also REEs and perhaps some amount of Zr.

The fraction with composition A can be burned off in fast reactors whereas the fractions with compositions B and C should be immobilized in stable matrices. Alpha-Activity of actinide fraction is subsequently determined by 244Cm, 241Am, 244Am, 239Pu and 242Pu during a long-term storage. The storage time depends on conditions and can reach several hundreds of thousands years. The main requirements to matrices are chemical and radiation resistances. The fraction with composition B can be incorporated in perovskite ceramics whereas in case of composition C the additional zirconolite and/or pyrochlore phases are necessary.
Real and Reciprocal Space Imaging of Radiation-Induced Defects in BCC Fe
Authors: Stoller R. E. , Ice G. E. , Barabash R. I.
Published: April 2011

It is important to determine the number and configuration of point defects that survive atomic displacement cascades in irradiated materials since only those defects that escape recombination are able to contribute to radiation induced property changes such as void swelling, hardening, embrittlement, and irradiation creep. Simulations of displacement cascades using molecular dynamics are being used to provide a description of the most probable surviving defects. In the case of interstitial-type defects in iron, these are predicted to be <110> and <111> type dumbbells and <111> crowdions, along with small clusters of these same defects. Diffuse x-ray and neutron scattering provides a direct method for obtaining detailed information on the displacement fields both near to and far away from the defects in addition to information on the particular position of the defect. To analyze such radiation damage with diffuse scattering we have modeled reciprocal space diffraction from crystals with variously oriented dumbbells and small clusters. Diffuse scattering measurements between and close to Bragg reflections are sensitive to the orientation of the dumbbells, and the size and type of the small clusters at sizes that are too small to analyze by electron microscopy. Displacement of the near neighbors induces diffuse scattering in regions between the Bragg peaks, whereas the long range part of the displacement field results in Huang scattering close to the Bragg reflections. Simulation of diffuse scattering by different interstitial defects around (h00), (hh0), (hhh), (3h,h, 0) reflections demonstrates that each defect type leads to distinct isointensity contours. These scattering signatures can be used to determine the type and configuration of the surviving interstitials.
Corrosion and Stress Corrosion Cracking of Alloy 22 in Lead-Containing Solutions
Authors: Pan Yi-Ming , Dunn Darrell S. , Yang Leitai , Cragnolino Gustavo A.
Published: April 2011

The susceptibility of Alloy 22 to localized corrosion and stress corrosion cracking was evaluated in lead-containing solutions. Speciation calculations indicate that aqueous dissolution of PbCl2 resulted in the formation of Pb2+ and Pb-Cl complexes. PbCl2 was selected among several lead compounds for its high solubility and dissociation rate. The total dissolved lead species concentration was measured by inductively coupled plasma-atomic emission spectrometry. Comparative anodic polarization tests were conducted in a range of deaerated, acidified PbCl2 solutions. The presence of lead species in a super-saturated PbCl2 solution with apH of 0.5 promotes the occurrence of apronounced anodic peak and significantly increases the passive current density. Enhanced dissolution of Alloy 22 resulted, as characterized by the presence of randomly distributed etch pits. At an applied potential of -100 mVSCE, which is the potential corresponding to the anodic peak, Alloy 22 was found to be resistant to stress corrosion cracking when tested in super-saturated PbCl2 solutions (pH 0.5) at 95 °C [203 °F]. Moreover, no deleterious effect of lead species on localized corrosion was observed in crevice specimens over a wide range of lead concentrations with the exception of acidified, super-saturated PbCl2 solutions. Provided that these high lead concentrations are not attainable in the anticipated repository environments, Alloy 22 is unlikely to be susceptible to stress corrosion cracking or localized corrosion.
Characteristics of the Oxides Films formed on Alloy C-22
Authors: Szmodis Alan W. , Anderson Kelly L. , Farmer Joseph C. , Lian Tiangan , Orme Christine A.
Published: April 2011

The passive corrosion rate of Alloy C-22 is exceptionally low in a wide range of aqueous solutions, temperatures and electrochemical potentials. Alloy C-22 contains approximately 22% chromium (Cr) by weight; thus, it forms a Cr-rich passive film in most environments. A study of the composition, thickness and other properties of the passive film was undertaken to better understand the role of the protective oxide in preventing corrosion. In general the oxide film is expected to be a function of solution pH, temperature and applied electrochemical potential. In this work we focus on the oxide films that form at pH=8.
U- and Hf-Bearing Pyrochlore and Zirconolite and their Leached Layers Formed in Acidic Solution: Tem Investigation
Authors: Xu Huifang , Wang Yifeng , Zhao Pihong , Bourcier William L. , Van Konynenburg Richard , Shaw Henry F.
Published: April 2011

Transmission electron microscopy results from a sintered ceramics with stoichiometry of Ca(U0.5Ce0.25Hf0.25)Ti2O7 show the material contains both pyrochlore and zirconolite phases and structural intergrowth of zirconolite lamellae within pyrochlore. (001) plane of zirconolite is parallel to (111) plane of pyrochlore because of their structural similarities. The pyrochlore is relatively rich in U, Ce, and Ca with respect to the coexisting zirconolite. Average compositions for the coexisting pyrochlore and zirconolite at 1350 °C are Ca1.01(Ce3+0.13Ce4+0.19U0.52Hf0.18)(Ti1.95Hf0.05)O7 (with U/(U+Hf) = 0.72) and (Ca0.91Ce0.09)(Ce3+0.08U0.26Hf0.66Ti0.01)Ti2.00O7 (with U/(U+Hf) = 0.28) respectively. A single pyrochlore (Ca(U,Hf)Ti2O7) phase may be synthesized at 1350 °C if the ratio of U/(U+Hf) is greater than 0.72, and a single zirconolite (Ca(Hf,U)Ti2O7) phase may be synthesized at 1350 °C if the ratio of U/(U+Hf) is less than 0.28. An amorphous leached layer that is rich in Ti and Hf forms on the surface after the ceramics has been leached in pH 4 buffered solution. The thickness of the layer ranges from 5 nm to 15 nm. The leached layer functions as a protective layer and therefore reduces the leaching rate.
Development of Parallel Dip Pen Nanolithography Probe Arrays for High Throughput Nanolithography
Authors: Bullen David A. , Wang Xuefeng , Zou Jun , Chung Sung-Wook , Liu Chang , Mirkin Chad A.
Published: April 2011

Dip Pen Nanolithography (DPN) is a lithographic technique that allows direct deposition of chemicals, metals, biological macromolecules, and other molecular “inks” with nanometer dimensions and precision. This paper addresses recent developments in the design and demonstration of high-density multiprobe DPN arrays. High-density arrays increase the process throughput over individual atomic force microscope (AFM) probes and are easier to use than arrays of undiced commercial probes. We have demonstrated passive arrays made of silicon (8 probes, 310 μm tip-to-tip spacing) and silicon nitride (32 probes, 100 μm tip-to-tip spacing). We have also demonstrated silicon nitride “active” arrays (10 probes, 100 μm tip-to-tip spacing) that have embedded thermal actuators for individual probe control. An optimization model for these devices, based on a generalized multilayer thermal actuator, is also described.
Characterisation of Collagen Scaffolds using X-ray Microtomography
Authors: Smith Patrick J. , Sachlos Eleftherios , McDonald Samuel , Reis Nuno , Derby Brian , Mummery Paul M. , Czernuszka Jan T.
Published: April 2011

Collagen scaffolds have been produced that incorporate predefined internal channels. The scaffolds were obtained with the aid of sacrificial moulds that have been manufactured using a rapid prototyping technique. A computer aided design file of the mould was created and then realised using an ink-jet printer. A dispersion of collagen was then cast into the mould and frozen. Ethanol was used to dissolve the mould leaving the collagen, which was then freeze dried to produce the final product. The scaffold was then analysed using X-ray microtomography (XMT) to determine whether the desired internal structure was obtained. It was found necessary to add saturated potassium iodide (KI) solution to the scaffold in order to analyse it satisfactorily by XMT. The resultant images indicate that the desired internal structure was obtained.
Poly-SiGe, a superb material for MEMS
Authors: Witvrouw Ann , Gromova Maria , Mehta Anshu , Sedky Sherif , Moor Piet De , Baert Kris , Hoof Chris van
Published: April 2011

In this overview article several MEMS applications of poly-SiGe are discussed: thermal applications, the application as a capping layer for MEMS wafer-level packaging and the use as MEMS structural layer for processing MEMS devices on top of CMOS. For all these applications also different deposition processes have been developed: chemical vapor deposition at reduced pressure (RPCVD), at low pressure (LPCVD) and with plasma enhancement (PECVD). Special techniques to reduce the processing temperature to the absolute minimum are reviewed as well: the use of hydrogenated microcrystalline SiGe, of metal-induced crystallization and of laser annealing. The latter methods are important when one wants to process SiGe MEMS above advanced CMOS with low-permittivity dielectrics.
Optimization of Mesoporous Silicon Microcavities for Proteomic Sensing
Authors: DeLouise L. A. , Miller B. L.
Published: April 2011

To expand the utility of p+ mesoporous silicon devices in proteomic biosensor applications, we have conducted in-depth studies to quantify the impact of employing a strong base post etch process to modify the microstructure of microcavity sensors tuned to operate in the visible spectrum. Changes in the optical response and quality of the cavity are quantified as a function of potassium hydroxide (KOH) exposure and initial porosity. Our results show that an aqueous ethanol solution containing millimolar concentrations of KOH is an effective means not only to increase the porosity and pore size, thereby enhancing pore infiltration of large (40–50kDa) proteins, but also to fine tune the optical properties of a passive optical devices.
A Novel AFM Chip for Fountain Pen Nanolithography - Design and Microfabrication
Authors: Kim Keun-Ho , Moldovan Nicolaie , Ke Changhong , Espinosa Horacio D.
Published: April 2011

A novel atomic force microscopy (AFM) probe has been developed to expand the capability and applications of dip-pen nanolithography (DPN) technology. This new probe has integrated microchannels and reservoirs for continuous ink feed, which allow “fountain-pen” writing called “Fountain Pen Nanolithography” (FPN). Ink is transported from the reservoirs through the microchannels and eventually dispensed onto substrates via a volcano-like dispensing tip. Numerical simulations have been performed to select optimal materials and suitable tip shapes providing a stable fluid-air interface in the tip. Microchannel and dispensing tip have been fabricated by surface micromachining, in particular employing 3 layers of thin films. Fluid flow through the microchannels has been experimentally examined. The probe was used to write on a gold substrate.
Electrical Porous Silicon Microarray for dna Hybridization Detection
Authors: Archer Marie , Christophersen Marc , Fauchet Philippe M. , Persaud Deoram , Hirschman Karl D.
Published: April 2011

The sensitivity of Porous Silicon (PSi) to the presence of charged molecules and its large internal surface area represent two important properties that make this material and ideal candidate for electrical biosensor development. We have demonstrated the use of a macroporous silicon electrical sensor for label-free detection of DNA hybridization in real time as well as identification of organic solvents in liquid phase. Binding of DNA inside the PSi matrix induces a change in capacitance and conductance. Having demonstrated the suitability of macroporous silicon layers for real time detection of DNA hybridization on single devices, we have extended our findings to the fabrication of a microarray with individual device electrical addressing capabilities. On a crystalline p-type silicon wafer, process steps such as KOH etching and electrochemical dissolution are employed in selected regions to create a free-standing porous membrane for sensing applications. Individual electrical contacts are made on the front side of the wafer while the infiltration of the probe and target molecules is done from the back avoiding any direct interaction of the molecules with the contact sites. We will report on the design considerations of the electrical porous silicon array and the preliminary results obtained using synthetic DNA as a model molecule.