bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Plasma Surface Treatment on the Self-forming Barrier Process in Porous SiOCH
Authors: Koike Junichi , Koike Junichi , Tökei Zsolt 
Published: April 2011

ABSTRACTSelf-forming barrier process was carried out on a porous low-k material with the Cu-Mn alloys. The effects of various surface treatments were investigated in the sample having a pore size of 0.9 nm and a porosity of 25%. Before and after annealing, samples were analyzed in cross section with transmission electron microscopy (TEM) and energy dispersive x-ray spectroscopy (EDS). Concentration profile was also analyzed with time-of-flight secondary ion mass spectroscopy (ToF-SIMS). The results indicated the penetration of Cu into the low-k interior during deposition, followed by the segregation of Cu at the low-k/Si interface during subsequent annealing. Although a diffusion barrier layer was formed and no further Cu penetration was not observed during annealing, initial Cu penetration in the deposition process was detrimental and should be prevented by restoring the plasma damage on the low-k surface.
Growth and Integration of High-Density CNT for BEOL Interconnects
Authors: Negreira Ainhoa Romo , Cott Daire J. , Verhulst Anne S. , Esconjauregui Santiago , Chiodarelli Nicolo′ , Ek Weis Johan , Whelan Caroline M. , Groeseneken Guido , Heyns Marc , De Gendt Stefan , Vereecken Philippe M. 
Published: April 2011

ABSTRACTThe integration of high-density CNT bundles as via interconnects in a CNT/Cu-hybrid BEOL stack is evaluated. CNT via-conduits may greatly improve heat dissipation and as such lower interconnect resistance and improve electromigration resistance. Each carbon shell of the nanotube contributes to electrical and thermal conduction and densities as high as 5×1013 shells per cm2 are estimated necessary. CNT growth processes on BEOL compatible metals are presented with tube densities up to 1012cm−2 and shell densities approaching 1013 cm−2 on blanket substrates. Selective growth of CNT bundles with carbon shell densities around 1012cm−2 is demonstrated with high yield. Ohmic behavior of TiN/CNT/Ti contacts is shown with a CNT via resistivity of 1.2 mΩ cm.
Electrical Characterisation of a Low-Density Layer of SnO Nanowires Deposited on a Set of Parallel Pt Electrodes
Authors: Kiselev Ilia , Kiselev Ilia , Sysoev Victor , Schneider Thomas 
Published: April 2011

ABSTRACTLow-density layers of SnO2 nanowires were produced using the vapor solid method and dry-pressed onto surface-oxidized Si-substrates equipped with a set of 39 parallel Pt-electrodes. Current-Voltage (I-V) characteristics of the segments between the electrodes were measured in ambient air at a substrate temperature of 300°C. Statistical analysis of the 38 I-V characteristics allows drawing conclusions, that only Schottky contacts between large nanowires and electrodes are significant for conductometry, and that they have very similar barrier characteristics. The statistical approach and its advantages are demonstrated. The clarity obtained concerning the roles of different resistivity mechanisms involved enables predictions of the nanowire net device behavior in applications, which is demonstrated on an instance of long-term stability examination of gas sensor arrays.
Nanowire Solar Cell Sensitized with II-VI Quantum Dot Layer
Authors: Nadarajah Athavan , Word Robert C. , VanSant Kaitlyn , Könenkamp Rolf 
Published: April 2011

ABSTRACTWe report first results on a new solar cell consisting of a p-i-n hetero-junction formed between n-type transparent nanowires, undoped semiconductor quantum dots and a wide bandgap p-type polymer layer. The overall structure is SnO2/ZnO/CdSe/MEH-PPV with MEH-PPV standing for poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene]. Microscopic studies on the structure of the quantum dot layer before and after anneal indicates a morphology change from a quantum dot assembly to a continuous polycrystalline thin film. The charge transfer between the absorber layer and the adjacent layers is improved as the layer is converted from the quantum dot assembly towards a polycrystalline thin film structure. In optimized devices the spectral photocurrent response shows contributions from the ZnO, the CdSe and the MEHPPV, covering the spectral range from 300 to 700nm with an external quantum efficiency between 30 and 40%. The overall energy conversion efficiency approaches 1%.
The Electronic Structures of Fullerene/Transition-Metal Hybrid Material
Authors: Matsumoto Yoshihiro , Sakai Seiji , Naramoto Hiroshi , Hirao Norie , Baba Yuji , Sugai Isamu , Takanashi Koki , Shimada Toshihiro , Maeda Yoshihito 
Published: April 2011

ABSTRACTLocal electronic structures of C60-Co hybrid films have been studied by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. XPS spectra of C 1s main and satellite peaks for the C60-Co films show binding-energy shifts and also line-broadening compared to those in a pure C60 film. In addition, XPS spectra in valence band region suggest an appearance of three new components at near Fermi level and HOMO level in the C60-Co film. These results are attributed to hybridizations between Co 3d band and C60 LUMO. The same effects have been observed in NEAXFS spectra at C 1s excitations.
Bimetallic Nanoparticles as Catalysts in Ionic Liquids
Authors: Scott Robert William James , Dash Priyabrat 
Published: April 2011

ABSTRACTWe will show that metallic and bimetallic nanoparticles solubilized in 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquids (IL) can be used as catalysts for a variety of oxidation and hydrogenation reactions. Nanoparticles were either directly synthesized in the IL or transferred to the IL from other solvents. Characterization was carried out by UV-Vis spectroscopy and transmission electron microscopy. Both the activity and selectivity of the hydrogenation reactions could be tuned by varying the composition of AuPd bimetallic nanoparticles. We will also show that the nanoparticle/IL catalysts can be recycled and then reused for further catalytic reactions with minimal loss in activity. In addition, new insights into the stabilization of nanoparticles in ionic liquids will be presented.
Threading and Interlocking: A Mechanism for the Simultaneous Enhancement of Polymer Stiffness, Strength, and Ductility
Authors: Torun Lokman , Paraskos Alex J. , Tsui Nicholas T. , Swager Timothy M. , Thomas Edwin L. 
Published: April 2011

AbstractWe have synthesized polyester systems containing pendant iptycene units and compared their mechanical/structural properties to a homologous reference polymer wherein benzene replaces iptycene units. Iptycenes have unique structural properties called internal molecular free volume (IMFV). The incorporation of iptycene into polyester backbones results in a polymer chain contour resembling “molecular barbed wire.” The contribution of iptycene to the mechanical properties of polyesters is significant and robust across concentration and processing conditions. The triptycene polyester films displayed a nearly 3-fold increase in Young's modulus, an approximately 3-fold increase in strength, and a more than 20-fold increase in strain to failure. We proposed that the presence of triptycene introduces two mechanisms for the enhancement of tensile mechanical properties: molecular threading and molecular interlocking.
LEEM / PEEM Study of Anisotropic Diffusion Fields in the Ag/Si(001) System
Authors: Wall Dirk , Roos Kelly Ryan , Horn-von Hoegen Michael , Meyer zu Heringdorf Frank-Joachim 
Published: April 2011

AbstractWe used direct imaging of diffusion fields in photoemission electron microscopy to study the diffusion (an)isotropy of Ag on flat and vicinal Si(001) surfaces with miscut angles between 0.2° and 4° in the [110] direction. While the diffusion field, represented by its iso-coverage zone, is isotropic on flat Si(001), it becomes elongated on the vicinal surface. The aspect ratio of the iso-coverage zone is used as a measure of the effective diffusion anisotropy on the surface. The aspect ratio of the iso-coverage zone increases continuously with the miscut angle, up to the maximum miscut that was studied. For the 4° miscut surface we find that the shape of the diffusion field is independent of the kink density of the substrate. From the temperature dependence of the aspect ratio, we determine an effective energy of ΔEani ∼ 0.7 eV for the activation energy responsible for the anisotropy.
Versatile Core-Sheath Biofibers using Coaxial Electrospinning
Authors: Han Daewoo , Boyce Steven T. , Steckl Andrew J. 
Published: April 2011

AbstractWe have investigated coaxial electrospinning to produce core-sheath fibers for tissue engineering. We have successfully produced core-sheath structured fibers of poly(ε-caprolactone) (PCL) and gelatin using the coaxial electrospinning technique. The core-sheath scaffold exhibits better mechanical properties compared to gelatin scaffold. We have characterized the resulting core and core-sheath fiber diameters and the scaffold porosity, etc.
Biomorphic Mesoporous Ce1−xZrxO2 Nanostructures Fabricated from Paper Templates
Authors: Ng Dickon H. L. , Li Jia 
Published: April 2011

AbstractA simple and versatile procedure was developed for synthesizing biomorphic mesoporous Ce1-xZrxO2. Aqueous cerium nitrate and zirconium nitrate solutions, and paper were used as the starting materials. Under the structure-directed effect offered by the active hydroxyl radicals of the cellulose in the paper templates, porous and fibrous structures of paper were replicated by the self-assembly of Ce1-xZrxO2 nanocrystallites after the paper underwent chemical infiltration and calcinations. The product, composing of interwoven network of fibers with diameter ranging from 10 to 20 <mu>m, was a replica of the original paper structure only that each fiber was assembled by Ce1-xZrxO2 nanocrystallites with grain size of 3-10 nm. The templating function of cellulose and the mechanism in the formation of nanocrystallites were proposed.
Site-selective immobilization of streptavidin on enzymatically biotinylated bacterial magnetic particles
Authors: Maeda Yoshiaki , Yoshino Tomoko , Takeyama Haruko , Takahashi Masaaki , Ginya Harumi , Asahina Junko , Tajima Hideji , Matsunaga Tadashi 
Published: April 2011

AbstractBiotinylated magnetic nanoparticles were constructed by displaying biotin acceptor peptide (BAP) on the surfaces of bacterial magnetic particles (BacMPs) synthesized by Magnetospirillum magneticum AMB-1. Both BAP and green fluorescent protein (GFP) were fused to Mms13 that was isolated from BacMP membranes. The localization of the fusion protein, BAP-Mms13-GFP, was confirmed by fluorescence analysis. BacMPs that expressed BAP-Mms13-GFP (BAP/GFP-BacMPs) were extracted from bacterial cells and incubated with biotin and Escherichia coli biotin ligase. The in vitro biotinylation of BAP/GFP-BacMPs was confirmed using alkaline phosphatase (ALP)-streptavidin detection. The conjugation system developed in this study provides a method for producing biotin- or streptavidin-labeled magnetic nanoparticles without the use of a crosslinker reagent. Various functional materials can be immobilized site-selectively onto these uniquely designed BacMPs. By combining this site-selective biotinylation technology and protein display methodology, increasingly innovative and attractive magnetic nano-materials can be constructed.
Incorporating Azo-group-functionalized Molecular-Junctions between Metal Nanoelectrodes to produce High-Rectification-Memory Nanodevices
Authors: Jasuja Kabeer , Berry Vikas 
Published: April 2011

AbstractThis report presents the functioning of a molecular memory device with azo-group-functionalized molecular-junctions between metal nanoelectrodes. These junctions are fabricated by a novel electrostatic-assembly process to incorporate azo-group containing polyelectrolyte (AP) between oppositely charged gold nanoparticles (GNP), functioning as nanoelectrodes. The device exhibits a bistable electronic memory effect induced by charge-transfer between AP and GNP, which can be controlled by photo-excitation of the AP. The ON and OFF memory states were found to have a rectification in the range of ∼5000 – 10000. This study will open avenues for development of next-generation molecular systems and devices to produce novel optoelectronic properties.
Microstructure and Hydrogen Absorption/Desorption Behavior of Nanoporous Pd Thin Films
Authors: Li Wen-Chung , Schendel Simone C. , Balk T. John 
Published: April 2011

AbstractNanoporous Pd (np-Pd) prepared from Pd-Ni alloy films on Si substrates was studied to understand hydriding/dehydriding processes in nanoscale Pd. Porous structures of the np-Pd thin films can be changed under different dealloying conditions. Stress measurement of the np-Pd showed that the np-Pd thin films can survive hydrogen pressures from 0 to 1 atm with no blistering, although this problem often occurs in dense Pd films in actual, high-pressure hydrogen environments. These tests indicated that hydrogen atoms can be stored in the np-Pd for much longer times than in fully dense Pd films subjected to ambient conditions. It is proposed that the stress distribution in np-Pd and the small pore size (<10 nm) inhibit hydrogen diffusion to free surfaces and thus prevent hydrogen degassing from the nanoporous structure. Moreover, phase transformation of Pd hydrides and effect of hydrogen trapping are also considered as possible reasons for the slow release of hydrogen.
Studies on Proton Conductivity and Methanol Permeability of Poly(ether sulfone)/Sulfonated Poly(ether ether ketone) Blend Membranes
Authors: Zhu Hong , Yang Wein-Duo , Wei Yong-sheng , Yang Wu-bin , Yu Xue-qing , Cao Xu-dong 
Published: April 2011

AbstractPartially Sulfonated Poly(ether ether ketone) (SPEEK) samples were prepared by modification of corresponding poly(ether ether ketone) (PEEK) with concentrated sulfuric acid. Poly(ether sulfone)(PES) was blended into SPEEK to prepare PES/SPEEK blend membranes by solution casting. The glass transition temperature of blend membranes indicated the molecular miscibility between PES and SPEEK. Characteristics of the blend membranes, including water uptake, thermal stability, methanol permeability, swelling degree, proton conductivity, etc, were investigated. PES played an important role in the blend membranes. Though the proton conductivity of PES/SPEEK blend membranes decreased to some extent, their performance for barrier methanol and swelling had remarkably enhanced, showing the feasibility for direct methanol fuel cell.
Thermodynamics of Gaseous Hydrogen and Hydrogen Transport in Metals
Authors: San Marchi Chris , Somerday Brian P 
Published: April 2011

AbstractThe thermodynamics and kinetics of hydrogen dissolved in structural metals is often not addressed when assessing phenomena associated with hydrogen-assisted fracture. Understanding the behavior of hydrogen atoms in a metal lattice, however, is important for interpreting materials properties measured in hydrogen environments, and for designing structurally efficient components with extended lifecycles. The assessment of equilibrium hydrogen contents and hydrogen transport in steels is motivated by questions raised in the safety, codes and standards community about mixtures of gases containing hydrogen as well as the effects of stress and hydrogen trapping on the transport of hydrogen in metals. More broadly, these questions are important for enabling a comprehensive understanding of hydrogen-assisted fracture. We start by providing a framework for understanding the thermodynamics of pure gaseous hydrogen and then we extend this to treat mixtures of gases containing hydrogen. An understanding of the thermodynamics of gas mixtures is necessary for analyzing concepts for transitioning to a hydrogen-based economy that incorporate the addition of gaseous hydrogen to existing energy carrier systems such as natural gas distribution. We show that, at equilibrium, a mixture of gases containing hydrogen will increase the fugacity of the hydrogen gas, but that this increase is small for practical systems and will generally be insufficient to substantially impact hydrogen-assisted fracture. Further, the effects of stress and hydrogen trapping on the transport of atomic hydrogen in metals are considered. Tensile stress increases the amount of hydrogen dissolved in a metal and slightly increases hydrogen diffusivity. In some materials, hydrogen trapping has very little impact on hydrogen content and transport, while other materials show orders of magnitude increases of hydrogen content and reductions of hydrogen diffusivity.
Properties of MgB2 Fabricated by Sintering Mg and B Sandwich Structures
Authors: Yeung Andrew , Ng Dickon H. L. 
Published: April 2011

AbstractMagnesium diboride (MgB2) was successfully produced in a pellet with sandwich-like structure. The sample was prepared by embedding a layer of Mg powder in between layers of boron powder before they were cold-pressed and sintered in argon atmosphere at different temperatures. After sintering, the interfacial regions between the Mg and B layers were examined and hexagonal platelets were observed lying along the interfacial regions in samples sintered at temperatures above 700°C. These hexagonal platelets were confirmed as MgB2. When samples were sintered at higher temperatures, the lateral size of the platelets increased. At 700°C, the average size of the platelets was 0.5 μgm, and it increased to 1.5 μgm in sample sintered at 900°C. In addition, the critical temperature (TC) and the magnetization (M) were also changed from 35.4 K to 37.1 K and −0.7 to −1.8 emu/g, respectively.
Requirements for TCO Substrate in Si-based Thin Film Solar Cells -Toward Tandem
Authors: Oyama Takuji , Kambe Mika , Taneda Naoki , Masumo Kunio 
Published: April 2011

AbstractNewly developed SnO2:F films having “double–texture (W-texture)” were evaluated in terms of optical and electrical properties and compared with Asahi type-U substrate. “W-textured” transparent conductive oxide (TCO) film was composed of a combination of 300-500nm large hills and small pyramidal texture covering them. “W-textured” TCO could show a large haze value exceeding 80% even at 800nm. Microcrystalline Si (μc-Si:H) thin film solar cells were fabricated on these TCOs and characterized. The result showed that a quantum efficiency of μc-Si:H solar cells was improved with “W-textured” TCOs significantly in longer wavelength region.
Design and Numerical Simulation on the Optical and Electrical Behavior of a ZnO:Al Nanowire Array a-Si pin Solar Cell
Authors: Liu Chang-Wei , Pei Zingway , Chang Shu-Tong , Ho Ren-Yui , Ho Min-Wei , Chen Yi-Chan , Chen Chi-Lin 
Published: April 2011

AbstractOne of the parameters that limit the efficiency of a thin film solar cell, especially the a-Si and the nc-Si solar cell is the cell thickness. Although thicker film can absorb most of the sun light, the optical generated carriers will recombination through the numerous gap states in the film that obtained lower short circuit current and fill factor. In the controversy, thinner film could not absorb enough sun light that also limit the short circuit current. In this works, we utilize nanowire structure to solve the conflict between the light absorption and the carrier transport. The designed structure has ZnO:Al nanowire array on the substrate. The p-i-n a-Si solar cell structure is grown along the surface of each ZnO: Al nanowire sequentially. Under sunlight illumination, the light is absorbed in the axis direction of the nanowire. However, the carrier transport is along the radial direction of the solar cell. Therefore, the long nanowire could absorb most of the solar light. In the mean time, the thickness of the solar cell still is thin enough for photo-generated carrier transport. The dependence of short circuit current, open circuit voltage and fill factor to the length, diameter and density of ZnO:Al nanowires were simulated.
Light Trapping in Thin Film Silicon n-i-p Solar Cells - Gains and Losses
Authors: Schropp Ruud E.I. , Li Hongbo , Rath Jatin K. , Franken Ronald H. 
Published: April 2011

AbstractThin film silicon solar cell technology frequently makes use of rough or textured surfaces in order to enhance light absorption within the thin absorber layers by scattering and total internal reflection (“light trapping”). The rough morphology of the optically functional internal surfaces both in superstrate and substrate cells however, not only has a beneficial effect on light scattering properties, but on the other hand may also have deleterious effects on the microscopic structure of the deposited layers, in particular if these layers are nanocrystalline. The narrow valleys in the surface morphology may lead to structural defects, such as cavities and pinholes. By adjusting the morphology, these defects can be avoided.However, even when structural defects in layers directly deposited on rough interfaces are avoided, the obtained optically defined maximum current density is still much lower than expected. For instance, in n-i-p structures the rough interface (the textured back reflector consisting of nanostructured Ag coated with ZnO) is located at the back of the cell, where only long wavelength light is present. The natively textured Ag film is sputtered at elevated temperature and optimized for diffusely reflecting this long wavelength light. From experiments we infer that the nanostructured metallic surface also gives rise to plasmon absorption in the red and near IR, and that this leads to a parasitic absorption, i.e. at least part of the absorbed energy is not re-emitted to the active layers.
Periodic Structures for Improved Light Management in Thin-film Silicon Solar Cells
Authors: Krc Janez , Campa Andrej , Luxembourg Stefan L. , Zeman Miro , Topic Marko 
Published: April 2011

AbstractAdvanced light management in thin-film solar cells is important in order to improve the photo-current and, thus, to raise up the conversion efficiencies of the solar cells. In this article two types of periodic structures ¡V one-dimensional diffraction gratings and photonic crystals,are analyzed in the direction of showing their potential for improved light trapping in thin-film silicon solar cells. The anti-reflective effects and enhanced scattering at the gratings with the triangular and rectangular features are studied by means of two-dimensional optical simulations. Simulations of the complete microcrystalline solar cell incorporating the gratings at all interfaces are presented. Critical optical issues to be overcome for achieving the performances of the cells with the optimized randomly textured interfaces are pointed out. Reflectance measurements for the designed 12 layer photonic crystal stack consisting of amorphous silicon nitride and amorphous silicon layers are presented and compared with the simulations. High reflectance (up to 99 %) of the stack is measured for a broad wavelength spectrum. By means of optical simulations the potential for using a simple photonic crystal structure as a back reflector in an amorphous silicon solar cell is demonstrated.