bluuebunny/crossref_metadata_2025_split huggingface dataset:
PECVD Synthesis of Silicon Nanowires Assisted by Templates of Gallium Islands
Authors: Gewalt Annika , Kalkofen Bodo , Lisker Marco , Burte Edmund P. 
Published: August 2010

AbstractIn this study, we investigated the growth of silicon nanowires forced by small gallium droplet templates. Those gallium islands previously were deposited by a modified PECVD method. Two different delivery techniques of the trimethylgallium precursor (TMGa) were tested regarding their applicability. On the one hand standard liquid delivery was performed, on the other the precursor was transported by vapor draw out of the heated bubbler. The TMGa then was pulsed into the carrier gas flow. The effects on the deposited islands of both delivery methods were compared. As substrates <111> oriented p-doped silicon wafers were used. For the subsequent growth of the silicon wires similarly PECVD was used as growth method. Silane served as precursor. Argon and hydrogen were used as plasma enhanced gases. The effects of the Ga particles deposited by both process modes upon the generated wires were analyzed.
Atomic layer deposition ZnO film as seed layer for hydrothermal growth of ZnO nanorods
Authors: Li Xianglin , Cheng Chuanwei , Fan Hongjin 
Published: August 2010

AbstractAtomic layer deposition (ALD) ZnO film as seed layer for growing aligned ZnO nanorods arrays is demonstrated. The effects of the deposition temperature and film thickness to the morphology of the ZnO nanorods are studied. The ALD is found to have its advantage over the conventional dip-coating method when being applied to three-dimensional (3D) substrates, as exemplified by the macroporous Si adn CNT arrays. As one example, the CNT-ZnO 3D hybrid nanostructures are obtained which might be useful for energy-related applications.
Magnetic State in Iron Hydride Under Pressure Studied by X-ray Magnetic Circular Dichroism at the FeK-edge
Authors: Ishimatsu Naoki , Matsushima Yasuharu , Maruyama Hiroshi , Tsumuraya Takao , Oguchi Tamio , Kawamura Naomi , Mizumaki Masaichiro , Matsuoka Takahiro , Takemura Kenichi 
Published: August 2010

AbstractIn order to study magnetic states in Fe-hydride under pressure, X-ray magnetic circular dichroism (XMCD) at the FeK-edge has been measured up to 27.5 GPa. As a result, hydrogenation from bcc-Fe to dhcp-FeH occurs within a narrow region of 3.2-3.8 GPa, which is clearly observed by the dichroic profile in dhcp-FeH differing from that in bcc-Fe. Influence of H atoms on Fe 3dand 4pelectronic states is discussed using the pressure-dependent XMCD and the first-principles calculation.
Formation of Methane Hydrates from Super-compressed Water and Methane Mixtures
Authors: Chen Jing-Yin , Yoo Choong-Shik 
Published: August 2010

AbstractUnderstanding the high-pressure kinetics associated with the formation of methane hydrates is critical to the practical use of the most abundant energy resource on earth. In this study, we have studied, for the first time, the compression rate dependence on the formation of methane hydrates under pressures, using dynamic-Diamond Anvil Cell (d-DAC) coupled with a high-speed microphotography and a confocal micro-Raman spectroscopy. The time-resolved optical images and Raman spectra indicate that the pressure-induced formation of methane hydrate depends on the compression rate and the peak pressure. At the compression rate of around 5 to 10 GPa/s, methane hydrate phase II (MH-II) forms from super-compressed water within the stability field of ice VI between 0.9 GPa and 2.0 GPa. This is due to a relatively slow rate of the hydrate formation below 0.9 GPa and a relatively fast rate of the water solidification above 2.0 GPa. The fact that methane hydrate forms from super-compressed water underscores a diffusion-controlled growth, which accelerates with pressure because of the enhanced miscibility between methane and super-compressed water.
Correlating Small Angle Scattering Spectra to Electrical Resistivity Changes in a Nickel-base Superalloy
Authors: Whelchel Ricky L , Kelekanjeri V. Siva Kumar G. , Gerhardt Rosario , Ilavsky Jan , Littrell Ken C. 
Published: August 2010

AbstractWaspaloy specimens aged at 800°C from 0.5h to 88.5h were evaluated via small angle neutron scattering (SANS), ultra small angle X-ray scattering (USAXS), electrical resistivity, and SEM. The average γ' precipitate size and volume fraction, obtained from modeling the small angle scattering data, was used to calculate a figure of merit of electron scattering. This figure of merit is designed to correlate the electron scattering ability of the material to the precipitate microstructure. The USAXS data shows a secondary precipitate population at smaller diameters that is absent from the SANS data, since the SANS measurements were not obtained at high enough values of Q. It is believed that this secondary population makes the USAXS-derived figure of merit more sensitive to the actual measured resistivity response than the SANS-derived values; however, the SANS derived primary precipitate sizes are believed to more accurate due to a larger sample volume.
Point Defects and Swelling Induced in Yttria-stabilized Zirconia by Swift Heavy Ion Irradiations
Authors: Costantini Jean-Marc , Beuneu François 
Published: August 2010

AbstractWe present a study of point-defect creation in yttria-stabilized zirconia (ZrO2: Y) or YSZ exposed to various heavy ions (from C to U) covering an energy range from 100 MeV to several GeVs. It is concluded that F+-type centers (involving singly-ionized oxygen vacancies) are produced by elastic-collision processes. The ion-induced out-of-plane expansion is found to be small (< 0.2%) and to increase linearly as a function of the average F+-type center concentration with a large slope compatible with small oxygen vacancy clusters. The large defect volume and <100> axial symmetry of the F+-type centers hint that these color centers might actually be divacancies (i.e. F2+centers).
Contribution of Electronic Energy Deposition to the Atomic Cascade Damage in Nanocrystals
Authors: Backman Marie , Djurabekova Flyura , Pakarinen Olli H , Nordlund Kai , Toulemonde Marcel 
Published: August 2010

AbstractUsing Molecular Dynamics we study the role of electronic excitations in the radiation damage caused by an energetic ion in Ge nanocrystals embedded in amorphous SiO2. The electronic effects are included as heating along the ion path modeled by the thermal spike model. In an ion energy regime where the electronic stopping power is larger than the nuclear, we find that the electronic effects enhance the defect creation significantly. We conclude that the electronic excitations below the track production threshold due to an energetic ion cannot be disregarded as a source of radiation damage.
AFM Study of the Fluence-Dependent Modification of the Surface of YSZ Due to Argon Ion Irradiation
Authors: Hawley Marilyn E. , Usov Igor O. , Won Jonghan , Sickafus Kurt E. 
Published: August 2010

AbstractYittria stabilized zirconia (YSZ) has long been of interest as a promising material for nuclear energy applications. It is the cubic form of zirconium oxide stabilized at room temperature by the addition of yttria. Previous studies of radiation damage in YSZ focused primarily on microstructural changes in the bulk or in the near surface layer whereas irradiation induced changes on the surface received little attention. Here we use atomic force microscopy, AFM, to study the fluence-dependent generation of surface modifications to YSZ due to 150 keV Ar+ ion implantation at fluences from 3×1015 to 1×1017 ions/cm2. The microstructural changes in the near surface region were previously investigated by Rutherford backscattering spectrometry in channeling geometry (RBS/C). Further, we investigated implantation in (100), (110), and (111) oriented single crystals of YSZ to explore differences in crystal orientation sensitivity to damage to ion irradiation. At the highest fluence, a dense packing of large round surface hillocks was observed. The ion induced surface modifications revealed by AFM differ slightly from the bulk lattice damage measured by RBS, although both indicate that under these implantation conditions, the (110) oriented crystal shows the most radiation damage resistance. The mean size of the hillocks scaled with concentration of implanted Ar atoms.
Surface Deformation Nanostructures and Stress Corrosion Crack Precursors Originating from Surface Grinding
Authors: Olszta Matthew , Thomas Larry , Bruemmer Stephen 
Published: August 2010

AbstractStress corrosion cracking (SCC) in light water reactor components has long been studied from a post mortem perspective, yielding insights into water chemistries and effects on crack propagation. Analysis of a cracked component does not effectively provide information on the corrosion events or on SCC initiation. It is important that microstructures of these early stages be understood because the original surface of the component formed during fabrication is often not the final surface condition that is exposed to reactor water. Pre-service grinding of reactor components and welds is performed for a variety of reasons, from aesthetics to preparation for non-destructive testing. It is this final surface microstructure that often controls SCC initiation. Surface and near-surface characteristics have been investigated in 304SS metal coupons on which controlled grinding was performed. These examinations indicate the extent of subsurface microstructural damage before high-temperature water exposure. Analytical electron microscopy techniques have been used to gain insights into possible surface precursors to corrosion damage and SCC initiation. Nanocrystalline grains were commonly found at the surface in lightly ground to heavily abraded materials within the first ˜0.5-10 ųm along with high dislocation densities, twinning and lath structures.
Electrospray ionization mass spectrometry of the cerium(III)-phosphomolybdate complex (NH4)11Ce(PMo11O39)2
Authors: Bray Travis Henry , Copping Roy , Shuh David K. , Gibson John 
Published: August 2010

AbstractElectrospray ionization quadrupole ion trap mass spectrometry of the ammonium lanthanide(III) phosphomolybdate complex (NH4)11Ce(III)(PMo11O39)2 has been conducted revealing the Ce-POM complexes H2Ce(III)P2Mo22O753- and Ce(III)PMo11O382- as the primary Ce species in 10 mM solutions. From the complex isotopic fingerprints produced through the assembly of multiple molybdenum atoms, a transition metal with seven naturally occurring isotopes, the identities of larger ions were confirmed via successive collision induced dissociation (CID) studies of the gas phase ions. The result of these CID studies was the production of smaller ions with reduced molybdenum content, allowing for comparison between calculated and experimental isotopic distributions. CID studies also provided insights into favored fragmentation pathways. These studies provide a basis to explore speciation and ESI behavior of actinide cluster complexes.
5f Electronic Structure and Fermiology of Pu Materials
Authors: Joyce John J. , Durakiewicz Tomasz , Graham Kevin S. , Bauer Eric , Moore David P. , Mitchell Jeremy N. , Kennison John A. , McCleskey T Mark , Jia Quanxi , Burrell Anthony , Bauer Eve , Martin Richard L. , Roy Lindsay , Scuseria Gustavo E. 
Published: August 2010

AbstractWe examine the electronic structure of δ-Pu, PuCoGa5, and PuO2 using high resolution as well as angle-resolved photoelectron spectroscopy. The fermiology of the strongly correlated metals δ-Pu and PuCoGa5 is investigated by determining the primary quasiparticle peak position with respect to the Fermi energy as well as the crystal momentum dependence of this peak for PuCoGa5. For the Mott insulator PuO2, the photoemission results are compared against the hybrid functional calculations and the prediction of significant covalency, is found to be reasonable.
Plutonium Environment in Lanthanide Borosilicate Glass
Authors: Stefanovsky Sergey , Shyriaev Andrey , Zubavichus Yan V. , Marra James C. 
Published: August 2010

AbstractTwo lanthanide borosilicate (LaBS) glasses containing 9.5 and 5.0 wt.% PuO2 prepared at 1500 °C consisted of a vitreous phase and minor crystalline PuO2 (or PuO2-HfO2 solid solution with minor HfO2) and britholite-type phases. X-ray absorption spectra of Pu LIII edge in the as-prepared and stored for various periods LaBS glasses were recorded, analyzed and compared with the spectra of crystalline PuO2. Pu in the as-prepared glass existed in predominantly tetravalent form (Pu4+ ions) but its storage in air results in partial oxidation as was seen from shift of peak energy values. In the structure of the as-prepared glass, Pu4+ ions had a co-ordination number (CN) close to 6 (˜6.3) and were located within the axially squeezed octahedra with five equidistant oxygen ions at a distance of 2.265±0.015 Å and one – at shorter distance (2.130±0.010 Å) from the Pu4+ ion. The Pu—Pu(M) distance (second co-ordination shell) was 3.675±0.015 Å. “Aging” of the LaBS glass with transformation of some fraction of Pu into penta- or/and hexavalent form was accompanied by a structural transformation.
Design and Synthesis of One and Two Dimensional Thermoelectric Nanomaterials Composed of Bismuth, Antimony, and Tellurium
Authors: Mott Derrick , Thuy Nguyen Thi Bich , Mai Nguyen Thanh , Maeda Youjiro , Phan Thuy Linh Tran , Koyano Mikio , Maenosono Shinya 
Published: August 2010

AbstractWith the advent of nanotechnology, the field of thermoelectric (TE) materials has been re-invigorated with many recent advances towards materials with high thermoelectric efficiency (dimensionless figure of merit, ZT). The realization of such materials opens up new avenues to the creation of devices that can be used in freon-less refrigeration, micro-electronic cooling, or for harnessing lost heat energy from sources such as car engines. In our own research work, we have successfully synthesized thermoelectric nanoscale materials composed of bismuth, antimony, and tellurium. By using a wet chemical thermal reduction procedure, we were able to create bismuth, antimony, and tellurium composite particles. What's more, by employing different molecular encapsulating agents in the synthesis, we were able to control the resulting shapes of the nanomaterials, resulting in both one and two dimensional bismuth, antimony, and tellurium nanoparticles. The one dimensional nanowires exhibit a micron scale length and ∼20-50nm diameter, while the two dimensional nanodiscs exhibit a diameter of ∼100nm and a thickness of ∼25nm. The unique morphology of these materials make them ideal candidates for processing into functional thermoelectric devices. This paper focuses on our recent study of the synthesis of bismuth, antimony, and tellurium composite nanomaterials of a nanowire and nanodisc morphology, which was directed by the capping agents used in the synthesis. Part of our preliminary study includes analysis of the thermoelectric efficiency of the materials. The resulting nanomaterials are characterized using techniques such as HR-TEM, XPS, XRD, and SEM the results of which provide insight into the design and synthesis of nanoscale materials with enhanced thermoelectric properties.
Thermoelectric Figure of Merit Calculations for Nanowires –The Moderate Confinement Regime
Authors: Cornett Jane , Rabin Oded 
Published: August 2010

AbstractWe report room temperature ZT calculations for silicon and indium antimonide nanowires of varying radii. Interestingly, some systems deviate significantly from the anticipated trend of ZT vs. radius. The InSb results are particularly remarkable due to the non-monotonic relationship seen between n-type ZT and wire radius; where typically we expect to see only a decrease with increasing radius, for InSb ZT increases between 20 and 100 nm wire radii. This is thought to be due to the high level of degeneracy of subbands for larger nanowire radii. These results indicate that the monotonic relationship between ZT and wire radius observed under strong confinement conditions cannot be assumed, but must be tested on a case-by-case basis for each materials system.
Impact of Dopants on the PbTe Thermoelectric Efficiency
Authors: Xiong Ka , Gupta Rahul P , White John B , Gnade Bruce , Cho Kyeongjae 
Published: August 2010

AbstractWe investigated the impact of doping group III elements (Al, Ga, In and Tl) on the electronic structure of PbTe by first principles calculations. The impurity-induced defect level changes with respect to the charge state of the impurity. We find that among the four elements, Tl is the best candidate for the enhancement of thermoelectric efficiency, consistent with the experimental data.
Indentation Testing of Bulk Zr0.5Hf0.5Co1-xIrxSb0.99Sn0.01 Half-Heusler Alloys
Authors: Verges Melody A , Schilling Paul J , Germond Jeffrey D , Upadhyay Puja , Miller William K , Takas Nathan J. , Poudeu Pierre F. P. 
Published: August 2010

AbstractIndentation tests were performed to assess the influence of compositional changes on the mechanical properties of several half-Heusler compounds with the general composition Zr0.5Hf0.5Co1-xIrxSb0.99Sn0.01 (x=0.0,0.1,0.3,0.5,0.7). These samples were synthesized by high temperature solid-state reactions and were consolidated by hot-pressing. Indentation measurements were obtained using both microhardness testing (Vickers) and depth-sensing nanoindentation. These measurements were used to determine the microhardness and the elastic modulus of each half-Heusler compound. The Vickers hardness values were found to range between 876 and 964. A slight increase in hardness was observed with the addition of iridium. The elastic stiffness values ranged from 229 GPa to 246 GPa. Here, a slight decrease in stiffness was observed with the addition of iridium.
Microstructure Investigation of Non-equilibrium Synthesized Filled Skutterudite CeFe4Sb12
Authors: Zhou Juan , Jie Qing , Li Qiang 
Published: August 2010

AbstractWe have prepared a variety of filled skutterudites through non-equilibrium synthesis by converting melt-spun ribbons into single phase polycrystalline bulk under pressure. In general, better thermoelectric properties are found in these samples. In this work, we performed microstructure characterization of non-equilibrium synthesized p-type filled skutterudite CeFe4Sb12 by X-ray diffraction, scanning electron microscopy and transmission electron microscopy in order to understand the structural origin of the improved thermoelectric properties. It is found that the non-equilibrium synthesized samples have smaller grain size and cleaner grain boundaries when compared to the samples prepared by the conventional solid-state reaction plus long term annealing. While smaller grain size can help reduce the lattice thermal conductivity, cleaner grain boundaries ensure higher carrier mobility and subsequently, higher electrical conductivity at the application temperatures.
Correlation of Microstructural Properties With Thermoelectric Performance of Bi0.5Sb1.5Te3 Films Fabricated by Electroplating
Authors: Koukharenko Elena , Li Xiaohong , Kuleshova Jekaterina , Fowler Marcel , Frety Nicole , Tudor John M , Beeby Steven P , Nandhakumar Iris , White Neil M 
Published: August 2010

AbstractThis study shows for the first time, the correlation between the microstructural properties (chemical composition and its homogeneity) and the thermoelectric properties for p-type Bi0.5Sb1.5Te3 electroplated films (10-15 μm thickness). High microstructural quality of Bi0.5Sb1.5Te3 electroplated films (a close to stoichiometry chemical composition with its high homogeneity elements distribution) was achieved by using an additive in the plating solution (sodium ligninsulfonate) as a surfactant agent. A fine-grained microstructure of 280 nm to 1μm has been observed for these materials, which half that of the plated films without a surfactant. The thermoelectric properties of electrodeposited Bi0.5Sb1.5Te3 films obtained without microstructural optimisation, show modest Seebeck coefficient values of 20-120 μm/K, electrodeposited film with an optimised microstructure exhibits very high values of Seebeck coefficient of 220-300 μm/K.
Electrically Active and Electrically Inactive 3d Transition Metal Centers in Si
Authors: Estreicher Stefan K , Backlund Daniel J 
Published: August 2010

AbstractSystematic first-principles calculations on transition metal (TM) impurities of the 3d series in Si have been performed. The equilibrium sites, migration energies, electrically-active gap levels, charge and spin states are predicted. While the properties of the isolated interstitials are experimentally well-known, much less experimental information is available about the consequences of their interactions with vacancy-like defects. We discuss here the properties of isolated interstitial Ti, Fe, and Ni, their interactions with vacancies and divacancies, the properties of the resulting substitutional impurities, and of the TM-divacancy {V-TM-V} complexes. In equilibrium, interstitial Ti, Fe, and Ni do not become substitutional, but a number of processing steps commonly used in PV manufacturing introduce highly mobile vacancies into the bulk. These vacancies strongly interact with interstitial TMs. At the substitutional site, Ti, Fe, and Ni have very different electrical properties than at the tetrahedral interstitial site. In particular, the electrical activity (and stable spin state) of Ti and Fe are greatly reduced, suggesting that the passivation by vacancies plays an unrecognized role during a variety of high-temperature processes.
Effects of 2nd Phases, Stress, and Na at the Mo/Cu2ZnSnS4 Interface
Authors: Johnson Jeffrey L. , Nukala Haritha , Bhatia Ashish , Oo W.M. Hlaing , Rieth Loren W , Scarpulla Michael A , Lund Elizabeth A 
Published: August 2010

AbstractCu2ZnSnS4 (CZTS) is an alternative material to Cu(In,Ga)Se2 (CIGSe) for use in thin film photovoltaic absorber layers composed solely of commodity elements [1,2]. Thus, if similar material quality and performance can be realized, its use would allow scale-up of terrestrial thin film photovoltaic production unhindered by material price or supply constraints. Here we report on our research on the deposition of CZTS by RF sputtering from a single CZTS target and co-sputtering from multiple binary sources on Mo-coated glass. We find some samples delaminate during post-sputtering furnace annealing in S vapor. Samples on borosilicate glass (BSG) delaminate much more frequently than those on soda-lime glass (SLG). We investigate the influences of the formation of frangible phases such as MoS2 at the CZTS/Mo interface and residual and thermal mismatch stress on delamination. We implicate fracture in a layer of MoS2 as the mechanism of delamination between the Mo and CZTS layers using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Wafer curvature measurements show significant (˜400 MPa) deposition stress for minimally optimized Mo deposition; however nearly stress-free Mo layers with good adhesion can be deposited using a multi-step Mo deposition recipe. Co-sputtering CZTS adds 100 MPa of stress on both BSG and SLG, however delamination is nearly absent for samples deposited on low-stress Mo layers. We investigate metallic diffusion barrier layers to prevent the formation of MoS2 at the interface. Lastly we discuss the importance of removing Mo oxide by sputter etching before CZTS deposition and its effects on adhesion and series resistance.