bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface Charging of n-type Gd2O3 and HfO2 thin Films
Authors: Wooten David , Losovyj Ya. B. , Petrosky J. , McClory J. , Tang Jinke , Wang Wendong , Dowben Peter A. 
Published: February 2009

AbstractGd2O3 and HfO2 films exhibit photovoltaic charging that depends on temperature. The dielectric properties of the surface and concomitant photovoltaic surface charging increases following oxygen exposure under ultrahigh vacuum conditions suggesting that the surface conductivity plays a role in the surface photovoltage charging.
An Amorphous IGZO Rare Earth Doped Luminescent Phosphor
Authors: Wellenius Patrick , Suresh Arun , Muth John F. 
Published: February 2009

AbstractIndium gallium zinc oxide (IGZO) has attracted recent attention as a high electron mobility amorphous material for high performance thin film transistors and subsequent use in active matrix backplanes for flexible displays. In this study, Eu:IGZO thin films were pulsed laser deposited at room temperature onto sapphire substrates and were investigated by cathodoluminescence and optical transmission. Photoluminescence was not observed with above band gap excitation. Thin film electroluminescent (TFEL) devices were also fabricated from these thin films. The thin films and devices demonstrate characteristic europium emission, with the most intense emission at 611 nm corresponding to the 5D0 to 7F2 transition. Luminescence was observed to increase with increasing oxygen pressure during deposition of the Eu:IGZO thin films and may be related to the free carrier density in the films. The authors believe this to be the first report of an amorphous oxide electroluminescent phosphor.
Effect of Growth Temperature on Structural and Magneto-Transport Properties of Co-Doped In2O3 Diluted Magnetic Semiconductors
Authors: Ghosh A , Gupta R K , Kahol P K , Ghosh K 
Published: February 2009

AbstractThin films of Co-doped In2O3 diluted magnetic semiconductor have been grown on c-plane sapphire single crystals using pulsed laser deposition technique. Different characterizations such as x-ray diffraction, atomic force microscopy, and magneto-transport have been carried out to study the effect of growth temperature on structural, electrical, and magneto-transport properties of these films. Crystalinity of the films increases with the growth temperature. The films grown at high temperature have preferred orientation along (222) direction, while films grown at low temperature behave more like to nanocrystaline. It is observed that electrical properties of the films strongly depend on growth temperature. The resistivity and magnetoresistance of the films decreases with increase in growth temperature. On the other hand, mobility of the films increases with increase in growth temperature. This could be due to improvement in crystalinity of the films.
A Trade Study for Waste Concepts to Minimize HLW Volume
Authors: Gombert Dirk , Carter Joe , Ebert Bill , Piet Steve , Trickel Tim , Vienna John 
Published: February 2009

AbstractAdvanced nuclear fuel reprocessing can partition wastes into groups of common chemistry. This enables new waste management strategies not possible with the plutonium, uranium extraction (PUREX) process alone. Combining all of the metallic fission products in an alloy and the balance as oxides in glass minimizes high level waste (HLW) volume. Implementing a waste management strategy using state-of-the-art combined waste forms and storage to allow radioactive decay and heat dissipation prior to placement in a repository makes it possible to place almost 10x the HLW equivalent of spent nuclear fuel (SNF) in the same repository space. However, using generic costs based on preliminary studies for waste stabilization facilities and separations modules, this analysis shows that combining the non-actinide wastes and using only one glass waste form is the most cost-effective.
Experimental and Atomistic Modelling Study of Ion Irradiation Damage in Thin Crystals of the TiO2 Polymorphs
Authors: Lumpkin Gregory R , Smith Katherine L , Blackford Mark G , Thomas Bronwyn S , Whittle Karl Rhys , Attard Darren J , Zaluzec Nestor J , Marks Nigel A 
Published: February 2009

AbstractThin crystals of rutile, brookite, and anatase were irradiated in-situ with 1.0 MeV Kr using the IVEM-TANDEM facility. Synthetic rutile and cassisterite (SnO2, rutile structure) remained crystalline up to 5 × 1015 ion cm-2 at 50 K. Natural brookite and anatase with low impurity levels became amorphous at 8.1 ± 1.8 × 1014 and 2.3 ± 0.2 × 1014 ions cm-2, respectively, at 50 K. Irradiation at higher temperature revealed Tc = 170 K for brookite and 242 K for anatase. Natural rutile with about 2 wt% impurities became amorphous at 9.4 ± 1.8 × 1014 ions cm-2 at 50 K and has a Tc = 207 K. The available data reveal both a structural effect in the polymorphs with low levels of chemical impurities and a chemical effect in natural rutile specimens containing up to about 1.7 wt% impurities.
Diffusion of 60Co, 137Cs and 152Eu in Opalinus Clay
Authors: García-Gutiérrez Miguel , Cormenzana José Luis , Missana Tiziana , Mingarro Manuel , Alonso Ursula 
Published: February 2009

AbstractThis study addresses the diffusion of representative sorbing elements, cobalt, cesium and europium in the Opalinus Clay (OPA). The methodology used here to determine diffusion coefficients is the ‘instantaneous planar source’ method. In this setup, a paper filter impregnated with tracer is introduced between two clay samples, avoiding contact between the tracer and the experimental vessels.
The apparent diffusion coefficients (Da) perpendicular to the bedding plane, obtained with this experimental method and fitting the experimental results with an analytical solution, were Da(Co) = (2.4-3.5)·10-14 m2/s, Da(Cs) = (5.9-8.0)·10-14 m2/s, and Da(Eu) = (1.0-2.1)·10-15 m2/s. With cobalt and cesium, classical in-diffusion experiments were also performed for comparison, and similar Da values were obtained but with a large dispersion.
To analyze the possible effects of the paper filter impregnated with the tracer on the determinations of Da with the analytical solution, one experiment was also analyzed using a detailed stochastic model of the setup. The good agreement between the two modeling approaches confirms the validity of this experimental setup and the analytical model fitting procedure.
In Situ Radiation Damage Studies of Ca3Zr2FeAlSiO12 and Ca3Hf2FeAlSiO12
Authors: Whittle Karl R , Blackford Mark , Lumpkin Gregory R , Smith Katherine L , Zaluzec Nestor J 
Published: February 2009

AbstractGarnets, A3B2C3O12, are considered to be potential host phases for the immobilization of high-level nuclear waste as they can accommodate a number of elements of interest, including Zr, Ti and Fe. The naturally occurring garnet, kimzeyite, Ca3(Zr,Ti)2(Si,Al,Fe)3O12, can contain ˜30wt% Zr. An understanding of the radiation tolerance of these materials is crucial to their potential use in nuclear waste immobilization. In this study two synthetic analogues of kimzeyite of composition Ca3Zr2FeAlSiO12 and Ca3Hf2FeAlSiO12 were monitored in situ during irradiation with 1.0 MeV Kr ions using the intermediate voltage electron microscope-Tandem User Facility (IVEM) at Argonne National Laboratory. The structure of these materials was previously determined by neutron diffraction and 57Fe Mössbauer spectroscopy. Ca3Zr2FeAlSiO12 and Ca3Hf2FeAlSiO12 have very similar structural properties with cubic Ia3d symmetry, the only significant difference being the presence of Zr and Hf, respectively, on the 6 coordinated B sites.
Diffusion Behavior of Organic Carbon and Iodine in Low-heat Portland Cement Containing Fly Ash
Authors: Chida Taiji , Sugiyama Daisuke 
Published: February 2009

AbstractThe diffusion of radionuclides in cementitious materials used as an engineered barrier is an important parameter in the performance assessment of the sub-surface repository system used for low-level radioactive waste disposal in Japan. In particular, organic carbon-14 and iodine-129 would provide large contributions to the dose evaluation, because of their low ability to be adsorbed on cementitious materials. In this study, the diffusion of acetate and iodide in hardened cement pastes was examined by through-diffusion experiments. Low-heat Portland cement containing 30 wt% fly ash (FAC), which is a candidate cement material for the construction of the sub-surface repository, was prepared for the diffusion experiments. The effective diffusion coefficients, De, of the trace ions for hardened FAC cement pastes were estimated to be on the order of 10-13 m2 s-1 at the beginning of the diffusion experiments. Then, the rate of diffusion of the trace ions decreased over the experimental period of 1-15 months. This is probably due to the change in the microstructure of the FAC as the result of a pozzolanic reaction. After a few months, the values of De were estimated to be on the order of 10-14 m2 s-1. These results suggest that an engineered barrier made of FAC can act as an effective barrier inhibiting the diffusion of trace ions such as organic carbon and iodine.
Current Status of Mo-Si-B Silicide Alloys for Ultra-high Temperature Applications
Authors: Heilmaier Martin , Saage Holger , Krüger Manja , Jehanno Pascal , Böning Mike , Kestler Heinrich 
Published: February 2009

AbstractWe review the current development status of molybdenum borosilicide (Mo-Si-B) alloys for ultra-high temperature applications in air. The assessment of several ingot and powder metallurgy approaches revealed that (i) the presence of a continuous Mo solid solution matrix is mandatory for adequate low temperature toughness and (ii) wrought processing of such alloys at temperatures established for refractory metals requires the presence of an ultrafine (sub-micron) microstructure. Both prerequisites could be fulfilled using mechanical alloying (MA) as the crucial processing step , however, values for the ductile-to-brittle transition temperature (DBTT) below 800°C could not be obtained due to grain boundary embrittlement by Si segregation. First results on the effect of different microalloying additions on a reduction of this segregation exemplified for the Mo solid solution will be presented and discussed.
In Situ Observation of Nucleation and Growth of Carbon Nanotubes from Iron Carbide Nanoparticles
Authors: Yoshida Hideto , Takeda Seiji , Uchiyama Tetsuya , Kohno Hideo , Homma Yoshikazu 
Published: February 2009

ABSTRACTNucleation and growth processes of carbon nanotubes (CNTs) in iron catalyzed chemical vapor deposition (CVD) have been observed by means of in-situ environmental transmission electron microscopy. Our atomic scale observations demonstrate that solid state iron carbide (Fe3C) nanoparticles act as catalyst for the CVD growth of CNTs. Iron carbide nanoparticles are structurally fluctuated in CVD condition. Growth of CNTs can be simply explained by bulk diffusion of carbon atoms since nanoparticles are carbide.
Self-aligned growth of single-walled carbon nanotubes using optical near-field effects
Authors: Zhou Y.S. , Xiong W. , Mahjouri-Samani M. , Yang W.Q. , Yi K.J. , He X.N. , Lu Yong Feng 
Published: February 2009

ABSTRACTBy applying optical near-field effects in a laser-assisted chemical vapor deposition (LCVD) process, self-aligned growth of ultra-short single-walled carbon nanotubes (SWNTs) was realized in a well controlled manner at a relatively low substrate temperature due to the nanoscale heating enhancement induced by the optical near-field effects. Bridge structures containing single suspending SWNT channels were successfully fabricated. Ultra-sharp tip-shaped metallic electrodes were used as optical antennas in localizing and enhancing the optical fields. Numerical simulations using High Frequency Structure Simulator (HFSS) reveal significant enhancement of electrical fields at the metallic electrode tips under laser irradiation, which induces localized heating at the tips. Numerical simulations were carried out to optimize SWNT growth conditions, such as electrode tip sharpness and film thickness, for maximal enhancement of electrical near field and localized heating.
Gate Controlled Negative Differential Resistance and Photoconductivity Enhancement in Carbon Nanotube Addressable Intra-connects
Authors: Lee Seon Woo , Rotkin Slava , Sirenko Andrei , Lopez Daniel , Kornblit Avi , Grebel Haim 
Published: February 2009

ABSTRACTWe have observed gate-controlled N-shaped negative differential resistance (NDR) and photoconductivity enhancement in carbon nanotube (CNT) based addressable intra-connects. The intra-connects – bridges spanning across planar electrodes – were measured at room temperature. Individual single-walled CNT (SWCNT) channels were grown using chemical vapor deposition (CVD) precisely between very sharp metal tips on the pre-fabricated electrodes without post-processing. The electrodes were made of cobalt. Methane and H2 gas mixture were introduced into quartz tube for an hour at 900 C, with flow rate of 1900 sccm for methane and 20 sccm for H2. We have investigated two different cases: in one case, the source-drain current-voltage, Ids-Vds, characteristics were linear. The other case exhibited nonlinear Ids-Vds characteristics. Raman scattering of the intra-connects indicated that each were made of SWCNT with radial breathing mode (RBM) at 191.9 cm-1 and 176.2 cm-1, respectively. Current-voltage Ids-Vds characteristics were measured for various Vgs from -10 V to +10 V. Negative differential resistance (NDR) was found in the Ids-Vgs curves for gate bias in the region of -3>Vgs>-6 V. The NDR peak was shifted to the negative side as the source-drain voltage was increased from Vds=0 to 0.75 V. Otherwise, the intra-connects exhibited characteristics of an ordinary p-type channel. The experiments were repeated under white light illumination. The light increases the carrier density in the channel but not in the metal electrodes and allowed us to study the effective doping of the channel without affecting the work function of the SWCNT/metal contact. The overall channel conductance increased under the light irradiation. Under illumination, the devices became more stable, as well. In summary, we have investigated contact properties between a SWCNT intra-connect and metal electrodes in a well controlled layout settings.
A New Thermionic Cathode Based on Carbon Nanotubes with a Thin Layer of Low Work Function Barium Strontium Oxide Surface Coating
Authors: Jin Feng , Liu Yan , Little Scott A , Day Chris M 
Published: February 2009

ABSTRACTWe have created a thermionic cathode structure that consists of a thin tungsten ribbon; carbon nanotubes (CNTs) on the ribbon surface; and a thin layer of low work function barium strontium oxide coating on the CNTs. This oxide coated CNT cathode was designed to combine the benefits from the high field enhancement factor from CNTs and the low work function from the emissive oxide coating. The field emission and thermionic emission properties of the cathode have been characterized. A field enhancement factor of 266 and a work function of 1.9 eV were obtained. At 1221 K, a thermionic emission current density of 1.22A/cm2 in an electric field of 1.1 V/μm was obtained, which is four orders of magnitude greater than the emission current density from the uncoated CNT cathode at the same temperature. The high emission current density at such a modest temperature is among the best ever reported for an oxide cathode.
Thermo- and chemo-electrical behavior of carbon nanotube filled co-continuous conductive polymer nanocomposites (CPC) to develop amperometric sensors
Authors: Lu Jianbo , Castro Mickaël , Kumar Bijandra , Feller Jean-François 
Published: February 2009

ABSTRACTThe conductive polymer nanocomposite (CPC) of multiwall carbon nanotubes (MWNT) filled Polycaprolactone (PCL) was formulated by melt mixing method. PCL based conductive phase served as disperse phase, blended with polypropylene (PP) and polyamide 12 (PA12) respectively. The thermo- and chemo-electrical properties of mono- and bi-component CPC have been investigated independently. Results show that PP/PCL-CNT CPC is a good temperature sensor whereas no significant response was observed while exposing to toluene vapor. In contrast, PA12/PCL-CNT exhibits good vapor sensing capability instead of temperature sensor. It is assumed that PP phase prevents the diffusion of vapor molecules within PCL conductive phase. The vapor sensing results indicated that PP external matrix provides the CPC with higher barrier effects than PA12.
Aligned-Crystalline Si Films on Non-Single-Crystalline Substrates
Authors: Findikoglu Alp , Holesinger Terry G. , Niemeyer Alyson , Matias Vladimir , Ugurlu Ozan 
Published: February 2009

AbstractWe summarize recent progress in growth and characterization of aligned-crystalline silicon (ACSi) films on polycrystalline metal and amorphous glass substrates. The ACSi deposition process uses, as a key technique, ion-beam-assisted deposition (IBAD) texturing on a non-single-crystalline substrate to achieve a biaxially-oriented (i.e., with preferred out-of-plane and in-plane crystallographic orientations) IBAD seed layer, upon which homo- and hetero-epitaxial buffer layers and hetero-epitaxial silicon (i.e., ACSi) films with good electronic properties can be grown. We have demonstrated the versatility of our approach by preparing ACSi films on customized architectures, including fully insulating and transparent IBAD layer and buffer layers based on oxides on glass and flexible metal tape, and conducting and reflective IBAD layer and buffer layers based on nitrides on flexible metal tape. Optimized 0.4-μm-thick ACSi films demonstrate out-of-plane and in-plane mosaic spreads of 0.8° and 1.3°, respectively, and a room-temperature Hall mobility of ∼90 cm2/V.s (∼50% of what is achievable with epitaxial single-crystalline Si films, and ∼1000 times that of amorphous Si films) for a p-type doping concentration of ∼4×1016 cm−3. By using various experimental techniques, we have confirmed the underlying crystalline order and the superior electrical characteristics of low-angle (<5°) grain boundaries in ACSi films. Forming gas anneal experiments indicate that Si films with low-angle grain boundaries do not need to be passivated to demonstrate improved majority carrier transport properties. Measurements on metal-insulator-semiconductor structures using ACSi films yield near-electronic-grade surface properties and low surface defect densities in the ACSi films. A prototype n+/p/p+–type diode fabricated using a 4.2-μm-thick ACSi film shows minority carrier lifetime of ∼3 μs, an estimated diffusion length of ∼30 μm in the p-Si layer with a doping concentration of 5×1016 cm−3, and external quantum efficiency of ∼80% at 450 nm with the addition of an MgO film anti-reflector.
Development of a simulated earthworm gut for determining bioaccessible arsenic, copper, and zinc from soil
Authors: Ma Wai K. , Smith Ben A. , Stephenson Gladys L. , Siciliano Steven D. 
Published: February 2009

Abstract
Soil physicochemical characteristics and contamination levels alter the bioavailability of metals to terrestrialinvertebrates. Current laboratory-derived benchmark concentrations used to estimate risk do not take into account site-specific conditions, such as contaminant sequestration, and site-specific risk assessment requires a battery of time-consuming and costly toxicity tests. The development of an in vitro simulator for earthworm bioaccessibility would significantly shorten analytical time and enable site managers to focus on areas of greatest concern. The simulated earthworm gut (SEG) was developed to measure the bioaccessibility of metals in soil to earthworms by mimicking the gastrointestinal fluid composition of earthworms. Three formulations of the SEG (enzymes, microbial culture, enzymes and microbial culture) were developed and used to digest field soils from a former industrial site with varying physicochemical characteristics and contamination levels. Formulations containing enzymes released between two to 10 times more arsenic, copper, and zinc from contaminated soils compared with control and 0.01 M CaCl2 extractions. Metal concentrations in extracts from SEG formulation with microbial culture alone were not different from values for chemical extractions. The mechanism for greater bioaccessible metal concentrations from enzyme-treated soils is uncertain, but it is postulated that enzymatic digestion of soil organic matter might release sequestered metal. The relevance of these SEG results will need validation through further comparison and correlation with bioaccumulation tests, alternative chemical extraction tests, and a battery of chronic toxicity tests with invertebrates and plants.
A quasiclassical approach to strongly correlated quantum dots
Authors: Matulis Algirdas , Jarema Denis , Anisimovas Egidijus 
Published: February 2009

Abstract
The adiabatic approximation and reaction-coordinate method is applied to the quasiclassical description of nanostructures. In a two-electron model quantum dot, the Schrödinger equation is solved in the vicinity of the transition path connecting two equivalent potential-energy minima. The obtained results demonstrate the formation of a Wigner crystallite.
Stochastic resonance induced by a multiplicative periodic signal in a logistic growth model with correlated noises
Authors: Bai Chunyan , Du Luchun , Mei Dongcheng 
Published: February 2009

Abstract
The stochastic resonance (SR) phenomenon induced by a multiplicative periodic signal in a logistic growth model with correlated noises is studied by using the theory of signal-to-noise ratio (SNR) in the adiabatic limit. The expressions of the SNR are obtained. The effects of multiplicative noise intensity α and additive noise intensity D, and correlated intensity λ on the SNR are discussed respectively. It is found that the existence of a maximum in the SNR is the identifying characteristic of the SR phenomena. In comparison with the SR induced by additive periodic signal, some new features are found: (1) When SNR as a function of λ for fixed ratio of α and D, the varying of α can induce a stochastic multi-resonance, and can induce a re-entrant transition of the peaks in SNR vs λ; (2) There exhibits a doubly critical phenomenon for SNR vs D and λ, i.e., the increasing of D (or λ) can induce the critical phenomenon for SNR with respect to λ (or D); (3) The doubly stochastic resonance effect appears when α and D are simultaneously varying in SNR, i.e., the increment of one noise intensity can help the SR on another noise intensity come forth.
Stochastic dynamics and mean field approach in a system of three interacting species
Authors: Valenti Davide , Spagnolo Bernardo 
Published: February 2009

Abstract
The spatio-temporal dynamics of three interacting species, two preys and one predator, in the presence of two different kinds of noise sources is studied, by using Lotka-Volterra equations. A correlated dichotomous noise acts on the interaction parameter between the two preys, and a multiplicative white noise affects directly the dynamics of the three species. After analyzing the time behaviour of the three species in a single site, we consider a two-dimensional spatial domain, applying a mean field approach and obtaining the time behaviour of the first and second order moments for different multiplicative noise intensities. We find noise-induced oscillations of the three species with an anticorrelated behaviour of the two preys. Finally, we compare our results with those obtained by using a coupled map lattice (CML) model, finding a good qualitative agreement. However, some quantitative discrepancies appear, that can be explained as follows: i) different stationary values occur in the two approaches; ii) in the mean field formalism the interaction between sites is extended to the whole spatial domain, conversely in the CML model the species interaction is restricted to the nearest neighbors; iii) the dynamics of the CML model is faster since an unitary time step is considered.