bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adamantane Derivative as Host Material for Efficient Deep-Blue Phosphorescent Organic Light Emitting Diodes
Authors: Fukagawa Hirohiko , Yokoyama Norimasa , Irisa Shiro , Tokito Shizuo 
Published: August 2010

AbstractWe report on a high efficiency deep-blue phosphorescent organic light-emitting diode (POLED) based on new electron-transporting host material. The new electron-transporting host material is an adamantane derivative with high triplet energy and high electron mobility. The deep blue POLED that we have developed utilizes a deep-blue phosphorescent guest material, iridium(III)bis(4’,6’,-difluorophenylpyridinato)tetrakis(1-pyrazolyl)borate, and exhibits a power efficiency of about 10.2 lm/W at luminance of 100 cd/m2 and maximum external quantum efficiency (EQE) of about 13 %. The power efficiency of our POLED is much higher than that of POLED using p–bis(triphenylsilyly)benzene (UGH2). The maximum EQE of our POLED was also slightly more than that of POLED using UGH2. The obtained difference in power efficiency originates from the new host material having higher electron mobility than that of UGH2.
Behaviour of Nanocrystalline Silicon Carbide Under Low Energy Heavy Ion Irradiation
Authors: Gosset Dominique , Luneville Laurence , Baldinozzi Gianguido , Simeone David , Audren Auregane , Leconte Yann 
Published: August 2010

AbstractSilicon carbide is one of the most studied materials for core components of the next generation of nuclear plants (Gen IV). In order to overcome its brittle properties, materials with nanometric grain size are considered. In spite of the growing interest for nano-structured materials, only few experiments deal with their behaviour under irradiation. To assess and predict their evolution under working conditions, it is important to characterize their microstructure and structure. To this purpose, we have studied microcrystalline and nanocrystalline samples before and after irradiation at room temperature with 4 MeV Au ions. In fact, it is well established that such irradiation conditions lead to amorphisation of the material, which can be restored after annealing at high temperature. We have performed isochronal annealings of both materials to point out the characteristics of the healing process and eventual differences related to the initial microstructure of the samples. To this purpose Grazing Incidence X-Ray Diffraction has been performed to determine the microstructure and structure parameters. We observe the amorphisation of both samples at similar doses but different annealing kinetics are observed. The amorphous nanocrystalline sample recovers its initial crystalline state at higher temperature than the microcrystalline one. This effect is clearly related to the initial microstructures of the materials. Therefore, the grain size appears as a key parameter for the structural stability and mechanical properties of this ceramic material under irradiation.
Materials Development by a Surface Modification for the Sulfuric Acid Decomposer in Iodine-Sulfur(IS)cycle for Nuclear Hydrogen Production System
Authors: Park Jae-Won , Kim Hyung-Jin , Kim Yong-Wan 
Published: August 2010

AbstractEfforts have been made to develop long term sustainable materials for use above 900°C in the SO3/SO2 environments utilized in Nuclear Hydrogen Production Systems. In this study, the surface of Hastelloy X was serially modified by evaporative SiC coating, ion beam mixing (IBM), additional coatings, and final ion beam hammering (IBH). Subsequent heating above 900°C results in no peeling-off of the SiC coating layer in spite of the huge difference in their coefficients of thermal expansion (CTE). It was also found that ion beam hammering (irradiation) suppresses the vacuum sublimation of the low density (∼40% of bulk) ceramic film (bulk materials begin to sublime at ∼ 750°C in a vacuum of 1.5×10−5 torr). The sublimation rate is ≤ 30% of the bulk rate after an annealing at 950 for 2 hrs but is decreased to ≤10% of the bulk rate after irradiation with 70 keV ions to a total dose of 1×1017 N ions/cm2. Further irradiation (up to 4×1017 N ions/cm2) does not further decrease the rate. Both an immersion test in 98% sulfuric acid and the potentiodynamic polarization test suggest that the surface modified Hastelloy X has a greatly prolonged life time in the corrosive sulfuric acid atmosphere, suggesting the serial surface modification process is applicable to the thermo-chemical system for the nuclear hydrogen production.
Mechanical Properties of Nanostructured Hard Coating of ZrO2
Authors: Sabirianov Renat F. , Namavar Fereydoon , Zeng Xiao Cheng , Bai Jaeil , Mei Wai-Ning 
Published: August 2010

AbstractNano-crystalline films of pure cubic ZrO2 have been produced by ion beam assisted deposition (IBAD) processes which combine physical vapor deposition with the concurrent ion beam bombardment in a high vacuum environment and exhibit superior properties and strong adhesion to the substrate. Oxygen and argon gases are used as source materials to generate energetic ions to produce these coatings with differential nanoscale (7 to 70 nm grain size) characteristics that affect the wettability, roughness, mechanical and optical properties of the coating. The nanostructurally stabilized chemically pure cubic phase has been shown to possess hardness as high as 16 GPa and a bulk modulus of 235 GPa. We examine the mechanical properties and the phase stability in zirconia nanoparticles using first principle electronic structure method. The elastic constants of the bulk systems were calculated for monoclinic, tetragonal and cubic phases. We find that calculated bulk modulus of cubic phase (237GPa) agrees well with the measured values, while that of monoclinic (189GPa) or tetragonal (155GPa) are considerably lower. We observe considerable relaxation of lattice in the monoclinic phase near the surface. This effect combined with surface tension and possibly vacancies in nanostructures are sources of stability of cubic zirconia at nanoscale.
Residual Stress Reduction in Sputter Deposited Thin Films by Density Modulation
Authors: Alagoz Arif Sinan , Kamminga Jan-Dirk , Grachev Sergey Yu , Lu Toh-Ming , Karabacak Tansel 
Published: August 2010

AbstractControl of residual stress in thin films is critical in obtaining high mechanical quality coatings without cracking, buckling, or delamination. In this work, we present a simple and effective method of residual stress reduction in sputter deposited thin films by stacking low and high material density layers of the same material. This multilayer density modulated film is formed by successively changing working gas pressure between high and low values, which results in columnar nanostructured and dense continuous layers, respectively. In order to investigate the evolution of residual stress in density modulated thin films, we deposited ruthenium (Ru) films using a DC magnetron sputtering system at alternating argon (Ar) pressures of 20 and 2 mTorr. Wafer’s radius of curvature was measured to calculate the intrinsic thin film stress of multilayer Ru coatings as a function of total film thickness by changing the number of high density and low density layers. By engineering the film density, we were able to reduce film stress more than one order of magnitude compared to the conventional dense films produced at low working gas pressures. Due to their low stress and enhanced mechanical stability, we were able to grow these density modulated films to much higher thicknesses without suffering from buckling. Morphology and crystal structure of the thin films were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). A previously proposed model for stress reduction by means of relatively rough and compliant sublayers was used to explain the unusually low stress in the specimens investigated.
Implications for Ultrafast Reflection Electron Diffraction from Temporal and Spatial Evolution of Transient Electric Fields
Authors: Park Hyuk , Zuo J.M. 
Published: August 2010

AbstractUnderstanding interaction of ultrafast pulsed laser with matter is critical for probing ultrafast processes in materials science, understanding the physics of laser ablation and the laser induced non-equilibrium carrier dynamics in metals and semiconductors, including plasmonics. When an intense laser pulse of femtoseconds (fs) in duration hits the surface of a targeted matter, it excites a hot electron gas. Part of the hot electrons is emitted from the surface in a way similar to thermionic emission. Electrons can also be emitted through multiphoton photoemission (MPPE) or thermally assisted MPPE. The emitted electrons travel at speeds that create transient electric fields (TEFs). To detect TEFs and study the dynamics of emitted electrons, we have developed a time resolved electron beam imaging technique that allows us to measure TEFs above a sample surface at picoseconds time resolution. We have also developed a model of the TEFs based on the propagation of emitted electrons and the percentage of electrons escaping from the surface. We examine the significance of TEFs for ultrafast reflection electron diffraction by examining anomalous effects in ultrafast reflection high energy electron diffraction (RHEED) of silicon surfaces.
Additive Manufacturing Technologies for the 3D Fabrication of Biocompatible and Biodegradable Photopolymers
Authors: Heller Christian , Schwentenwein Martin , Varga Franz , Stampfl Jürgen , Liska Robert 
Published: August 2010

AbstractHigh molecular weight vinyl esters and carbonates based on oligo(ethylene glycol), oligomeric fatty acids and poly(hexamethylene carbonate), as alternatives for potentially cytotoxic acrylate based monomers have been structured by Additive Manufacturing Technologies (AMTs) like Microstereolithography (μ-SLA), Digital Light Processing (DLP) and Two-Photon Induced Photopolymerization (TPIP). With these techniques feature resolutions down to 10 μm (μ-SLA and DLP) or even 200 nm (TPIP) can be obtained.
This new class of monomers exhibits LC50 values for cytotoxicity up to two orders of magnitude lower than acrylate references. Beside a high reactivity of the resin, the shrinkage and the mechanical properties of the final part material are another essential parameter. Low molecular weight monomers are very reactive and lead to densely cross-linked materials which suffer from high shrinkage and strains within the cured material. Therefore, mixtures of high molecular weight vinyl esters/carbonates with low molecular weight crosslinkers have been evaluated regarding their photoreactivity and mechanical properties.
Production Nozzle-Less Electrospinning Nanofiber Technology
Authors: Petrik Stanislav , Maly Miroslav 
Published: August 2010

AbstractThe theoretical background and technical capabilities of the free liquid surface (nozzle-less) electrospinnig process is described. The process is the basis of both laboratory and industrial production machines known as NanospiderTM and developed by Elmarco s.r.o. Technical capabilities of the machines (productivity, nanofiber layer metrics, and quality) are described in detail.
Comparison with competing/complementary technologies is given, e.g. nozzle electrospinning, nano-meltblown, and islets-in-the sea. Application fields for nanofiber materials produced by various methods are discussed. Consistency of the technology performance and production capabilities are demonstrated using an example of polyamide nanofiber air filter media.
Controllable Chemical Modification of Polyaniline Nanofibres
Authors: Lahiff Emer , Lynam Carol , Gilmartin Niamh , Wallace Gordon G , O’Kennedy Richard , Diamond Dermot 
Published: August 2010

AbstractA method for simply and controllably modifying the surface of polyaniline nanofibres is described. The technique can be used to attach substituents bearing both acid and amine functional groups, making the materials suitable for further modification. Acid/amine functionalisation is achieved by a simple reflux reaction and therefore is a quick and easily scalable process. The modified nanofibres maintain their ability to switch between different states displaying distinctly different properties, thus making them suitable for adaptive sensing applications. As an example, we demonstrate how biomolecules can be attached to these functionalised nanofibres, to produce conducting polymer-based biosensors.
Poly(3,4-alkylenedioxythiophene) Nanostructures
Authors: Sarac A.Sezai 
Published: August 2010

AbstractElectropolymerization of unsubstituted and substituted propylene - dioxythiophenes (i.e., ProDOT & ProDOT-Bz) on ( ˜7 μm diameter) single carbon fiber microelectrodes (SCFMEs) in different electrolytes resulted the network of nanopore structures.
Surface morphology of coatings were investigated by Scanning Electron Microscopy (SEM), the attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was used for the characterization . Electrochemical impedance spectroscopic investigation of these nanostructures has been indicated the capacitive behavior of electrode system. Data were used to simulate at applied potential and explained by equivalent circuit modeling.
Synthesis and Cytotoxicity of Luminescent InP Quantum Dots
Authors: Wang Yuxuan , Quek Chai Hoon , Leong Kam W. , Fang Jiye 
Published: August 2010

AbstractAs a potential biological imaging probe with a long-wavelength of emission, InP quantum dots were prepared via a high-temperature organic solution approach, and successfully transferred into an aqueous system through a ligand-exchange process using various functional surfactants. Photoluminescence and X-ray characterizations confirmed the desired properties of the InP quantum dots. The cytotoxicity of the water-soluble InP quantum dots against phaeochromocytoma PC12 cells as evaluated by the MTS cell viability assay was low relative to a positive control, poly(ethyleneimine). This study suggests a bright potential for this new type of InP quantum dots in bioimaging applications.
Critical Concentrations of Atmospheric Contaminants in a-Si:H and μc-Si:H Solar Cells
Authors: Merdzhanova Tsvetelina , Woerdenweber Jan , Kilper Thilo , Stiebig Helmut , Beyer Wolfhard , Gordijn Aad 
Published: August 2010

AbstractWe report on a direct comparison of the effect of the atmospheric contaminants on a-Si:H and μc-Si:H p-i-n solar cells deposited by plasma-enhanced chemical vapor deposition (PECVD) at 13.56 MHz. Nitrogen and oxygen were inserted by two types of controllable contamination sources: (i) directly into the plasma through a leak at the deposition chamber wall or (ii) into the process gas supply line. Similar critical concentrations in the range of 4-6×1018 cm-3 for nitrogen and 1.2-5×1019 cm-3 for oxygen were observed for both a-Si:H and μc-Si:H cells for the chamber wall leak. Above these critical concentrations the solar cell efficiency decreases for a-Si:H solar cells due to losses in the fill factor under red light illumination (FFred). For μc-Si:H cells the losses in FFred and in short-circuit current density deteriorate the device performance. Only for a-Si:H the critical oxygen concentration is found to depend on the contamination source. Conductivity measurements suggest that at the critical oxygen concentration the Fermi level is located about 0.05 eV above midgap for both a-Si:H and μc-Si:H.
A New Approach to Light Scattering from Nanotextured Interfaces For Silicon Thin-film Solar Cells
Authors: Battaglia Corsin , Escarre Jordi , Söderström Karin , Haug Franz-Josef , Dominé Didier , Feltrin Andrea , Ballif Christophe 
Published: August 2010

AbstractWe investigate the influence of refractive index contrast on the light scattering properties of nanotextured interfaces, which serve as front contact for p-i-n thin-film silicon solar cells. We here focus on ZnO surfaces with randomly oriented pyramidal features, known for their excellent light trapping performance. Transparent replicas, with a different refractive index, but practically identical morphology compared to their ZnO masters, were fabricated via nanoimprinting. Within the theoretical framework we recently proposed, we show how the angular and spectral dependence of light scattered by nanostructures with identical morphology but different refractive index may be related to each other allowing direct comparison of their light trapping potential within the device.
Influence of Hydrogen on the Germanium Incorporation in a-Si1-xGex:H for Thin-film Solar Cell Application
Authors: Wang Chien-Ming , Huang Yen-Tang , Kuo-Hsi Yen , Hsu Hung-Jung , Hsu Cheng-Hang , Zan Hsiao-Wen , Tsai Chuang-Chuang 
Published: August 2010

AbstractIn this work, we examined the Ge incorporation and the accompanied defect formation during PECVD deposition of hydrogenated amorphous silicon-germanium alloys (a-Si1-xGex:H). In particular, we studied the effect of hydrogen on film growth, defect formation, Ge and Si incorporation efficiencies, and the H-bonding configuration. Our results indicate that hydrogen has a strong effect on improving the a-Si1-xGex:H film quality and the Ge incorporation in a-Si1-xGex:H. With adequate hydrogen dilution, the a-Si1-xGex:H thin-film quality significantly improved. However, excessive hydrogen dilution degraded the film properties. A number of analytical tools were employed, including FTIR, XPS, UV-Visible spectroscopy, photoconductivity, etc. The a-Si1-xGex:H material having 24% Ge content and a bangap of 1.61ev produced the solar cell with a conversion efficiency of 7.07%.
Ultrafast Deposition of Crystalline Si Films Using a High Density Microwave Plasma
Authors: Jia Haijun , Kondo Michio 
Published: August 2010

AbstractA multi-pressure microwave plasma source is developed and is applied for the fast deposition of crystalline silicon films. In this paper, the plasma source is diagnosed firstly. Electron density, electron temperature and discharge gas temperature of the plasmas generated in ambient air are studied using optical emission spectroscopy (OES) method. By using the high density microwave plasma source, depositions of crystalline silicon films from SiH4+He mixture at reduced pressure conditions are investigated systematically. After optimizing the film deposition conditions, highly crystallized Si films are deposited at a rate higher than 700 nm/s. We also find that the deposited films are fully crystallized and crystalline structure of the deposited film evolves along the film growth direction, i.e. large grains in surface region while small grains in the bottom region of the film. Based on the observed results, a possible mechanism, the annealing-assisted plasma-enhanced chemical vapor deposition, is proposed to describe the film growth process.
FDTD Simulation of Light Propagation Inside a-Si:H Structures
Authors: Fantoni Alessandro , Pinho Pedro 
Published: August 2010

AbstractWe have developed a computer program based on the Finite Difference Time Domain (FDTD) algorithm able to simulate the propagation of electromagnetic waves with wavelengths in the range of the visible spectrum within a-Si:H p-i-n structures. Understanding of light transmission, reflection and propagation inside semiconductor structures is crucial for development of photovoltaic devices. Permitting 1D analysis of light propagation over time evolution, our software produces results in well agreement with experimental values of the absorption coefficient. It shows the light absorption process together with light reflection effects at the incident surface as well as at the semiconductor interfaces. While the effects of surface reflections are easily taken into account by the algorithm, light absorption represents a more critical point, because of its non-linear dependence from conductivity. Doping density, density of states and photoconductivity calculation are therefore crucial parameters for a correct description of the light absorption-transmission phenomena through a light propagation model.The results presented in this paper demonstrate that is possible to describe the effect of the light-semiconductor interaction through the application of the FDTD model to a a-Si:H solar cell. A more general application of the model to 2D geometries will permit the analysis of the influence of surface and interface roughness on the device photovoltaic efficiency.
Self-catalyzed Tritium Incorporation in Amorphous and Crystalline
Authors: Liu Baojun , Kherani Nazir , Chen Kevin P , Kosteski Tome , Leong Keith , Zuktynski Stefan 
Published: August 2010

AbstractTritiated amorphous and crystalline silicon is prepared by exposing silicon samples to tritium gas (T2) at various pressures and temperatures. Total tritium content and tritium concentration depth profiles in the tritiated samples are obtained using thermal effusion and Secondary Ion Mass Spectroscopy (SIMS) measurements. The results indicate that tritium incorporation is a function of the material microstructure rather than the tritium exposure condition. The highest tritium concentration attained in the amorphous silicon is about 20 at.% on average with a penetration depth of about 50 nm. In contrast, the tritium occluded in the c-Si is about 4 at.% with a penetration depth of about 10 nm. The tritium concentration observed in a-Si:H and c-Si is higher than reported results from post-hydrogenation experiments. The beta irradiation appears to catalyze the tritiation process and enhance the tritium dissolution in silicon material.
Light-triggered Silicon-carbon Pi'npin Devices for Optical Communications: Theoretical and Electrical Approaches
Authors: Vieira Manuela , Vieira M. A. , Costa João , Louro Paula , Fernandes Miguel , Fantoni Alessandro 
Published: August 2010

AbstractIn this paper a light-activated multiplexer/demultiplexer silicon-carbon device is analysed. An electrical model for the device operation is presented and used to compare output signals with experimental data. An algorithm that takes into accounts the voltage and the optical bias controlled sensitivities is developed. The device is a double pi'n/pin a-SiC:H heterostructure with two optical gate connections for light triggering in different spectral regions. Multiple monochromatic pulsed communication channels were transmitted together, each one with a specific bit sequence. The combined optical signal was analyzed by reading out, under different applied voltages and optical bias, the generated photocurrent across the device. Experimental and simulated results show that the output multiplexed signal has a strong nonlinear dependence on the light absorption profile, i.e. on the incident light wavelength, bit rate and intensity under unbalanced light generation of carriers. By switching between positive and negative voltages the input channels can be recovered or removed from the output signal.
Evolution of Stacking Faults Defects During Epitaxial Growths: Role of Surface Kinetics
Authors: Camarda Massimo , La Magna Antonino , Canino Andrea , La Via Francesco 
Published: August 2010

AbstractThree dimensional kinetic Monte Carlo simulations on super-lattices are applied to study the evolution of stacking faults during epitaxial growths. We show that, in the case of misoriented close packed substrates, these defects can either extend throughout the entire epilayer (i.e. extended from the substrate up to the surface) or close in dislocation loops, in dependence of the deposition conditions. We explain this behavior in terms of a surface kinetic competition between these defects and the surrounding crystal: if the local growth rate of the defect is larger compared with that of the perfect crystal the defect will expands, otherwise it will closes. This mechanisms allows to explain several experimental results on homo and hetero epitaxies.