bluuebunny/crossref_metadata_2025_split huggingface dataset:
Density-Functional Theory Study of Hydrogen Induced Platelets in Silicon
Authors: Bîlteanu Liviu , Crocombette Jean-Paul 
Published: September 2011

ABSTRACTIn this contribution we present the results of Density-Functional Theory (DFT) calculations of platelets as modelled by infinite planar arrangements of hydrogen atoms and vacancies in (100) planes of silicon. From the observation of the relaxed platelet structures and the comparison of their energy with the one of hydrogen molecules dissolved in silicon we were able to evidence several features. A planar arrangement of hydrogen atoms inserted in the middle of Si-Si bonds proves unstable and Si bonds must be broken for the platelet to be stable. In the (100) plane the most stable configuration is the one with two Si-H bonds (a so-called SiH2 structure). It is possible to generate SiH3 structures which are more stable than hydrogen dissolved in Si bulk but less than SiH2 structures but SiH1 or SiH4 sometimes observed in experiments prove unstable.
Absorption Enhancement in Plasmonic Solar Cells by Incorporation of Periodic Nanopatterns
Authors: Wang W. , Wu S. , Lu Y.L. , Reinhardt Kitt , Chen S.C. 
Published: September 2011

ABSTRACTCurrently, the performances of thin film solar cells are limited by poor light absorption and carrier collection. In this research, large, broadband, and polarization-insensitive light absorption enhancement was realized via incorporation of different periodic nanopetterns. By studying the enhancement effect brought by different materials, dimensions, coverage, and dielectric environments of the metal nanopatterns, we analyzed the absorption enhancement mechanisms as well as optimization criteria for our designs. A test for totaling the absorption over the solar spectrum shows an up to ∼30% broadband absorption enhancement when comparing to conventional thin film cells.
Wide-spectral-range, Expanded-beam Spectroscopic Ellipsometer and its Application for Imaging/Mapping of Graded Nanocrystalline Si:H Films
Authors: Nemeth A. , Attygalle D. , Dahal L. R. , Aryal P. , Huang Z. , Salupo C. , Petrik P. , Juhasz G. , Major C. , Polgar O. , Fried M. , Pecz B. , Collins R. W. 
Published: September 2011

ABSTRACTA prototype expanded-beam spectroscopic ellipsometer has been developed that uses uncollimated (non-parallel, diffuse) illumination with a detection system consisting of an angle-of-incidence-sensitive pinhole camera for high-speed, large-area imaging/mapping applications. The performance of this novel instrument is being tested for imaging/mapping of mixed-phase hydrogenated silicon films having graded amorphous (a-Si:H) and nanocrystalline (nc-Si:H) components throughout the film depth. The speed of the measurement system makes the instrument suitable for use on production lines. The precision enables detection of subnanometer thicknesses, and refractive index and extinction coefficient changes of 0.01. Angle-of-incidence and mirror calibrations are made via well-known sample structures. Alternative commercial instrumentation for mapping by spectroscopic ellipsometry must translate the sample or ellipsometer in two dimensions. For this instrumentation, even a 15 × 15 cm2 sample with cm2 resolution requires > 200 measurements and at least 15 min. By imaging along one dimension in parallel, the expanded-beam system can measure with similar resolution in < 2 min. The focus of recent instrumentation efforts is on improving the overall system spectral range and its performance.
Semi reflective biopolymer layers for the detection of biomass hydrolytic enzymatic activities
Authors: Cerclier C. , Moreau C. , Guyomard-Lack A. , Bonnin E. , Bizot H. , Cathala B. 
Published: September 2011

ABSTRACTStructural colors were obtained by the deposition of plant cell walls biopolymers films on reflective support. Multilayered xyloglucan(XG)/cellulose nanocrystals(CN) thin films were obtained by spin-assisted layer-by-layer assembly while arabinoxylan (AX) thin films were elaborated via the spin-coating of AX/melamine formaldehyde resin followed by a cross-linking step. The effects of aqueous solutions on the stability of the structural colors were evaluated. The films were subsequently used to detect cellulase and xylanase activities by the change in the colors due to the film degradation. This enzymatic assay method appeared to be about 150 more sensitive that a standard method. Moreover due its simplicity, the method could be used to detect other biomass-hydrolyzing enzymes and more generally for other heterocatalytic degradations of solid polymer layers.
Hydrogen Production from Ethanol. Comparing Thermal Catalytic Reactions to Photo-catalytic Reactions.
Authors: Scott M. , Nadeem A.M. , Waterhouse G.I.W. , Idriss H. 
Published: September 2011

ABSTRACTHydrogen production from renewables such as bio-ethanol is one of the most promising processes for energy carriers in a sustainable way. In this work we review and compare two catalytic systems: one based on thermal activation over bimetallic catalysts (Rh-Pd/CeO2) and the other over photo-excited semiconductor catalysts (Au/TiO2 anatine, rutile and anatase/rutile). It is found that the hydrogen yield is far higher on the thermally activated catalysts (at 773K) when compared to that of the photo-exited catalysts (at room temperature); about 60 times. However, the photo-excited catalysts are a promising way to create a fully sustainable system for future applications if the complete removal of hydrogen atoms from water and ethanol are obtained at room temperature.
Ab initio Study of the Hydrogen Molecule on ZnO Surfaces
Authors: Liu Po-Liang , Wu Yen-Ting , Siao Yu-Jin 
Published: September 2011

ABSTRACTWe conduct first-principles total-energy density functional calculations to study the interaction of H2 on ZnO surfaces. Four surface models of Zn-terminated (0001)-, O-terminated (0001)-, $(10{\bar 1}0)-$, and $(2{\bar 1}{\bar 1}0)-$oriented ZnO planes in the presence of H2 are evaluated. The relative stability of four different surface models is examined as a function of the chemical potentials of oxygen and hydrogen. We find that only surfaces of O-terminated (0001)-oriented ZnO models exhibit active sites for the dissociation of H2, which in turn enables the formation of water from dissociative chemisorption of 2H on the O-terminated ZnO(0001) surface. The surface energy of O-terminated ZnO(0001) surface in the presence of water was found to be negative under the O-rich and H-rich condition. The findings agree with the experimental observations that ZnO epitaxial layers are easily etched by hydrogen at typical growth temperatures.
Control of Crystal Orientation of Epitaxial Si nanowires on Si Substrate Using AAO template
Authors: Shimizu Tomohiro , Wang Qi , Wang Chonge , Inoue Fumihiro , Koto Makoto , Jeon Minsung , Shingubara Shoso 
Published: September 2011

ABSTRACTControl of crystal orientation of vertically grown epitaxial Si (111) and (110) nanowire arrays on Si substrate has been demonstrated using a combination of an anodic aluminum oxide (AAO) template and vapor – liquid – solid (VLS) growth method. The crystal orientation of the nanowire was investigated by transmission electron microscopy. A growth direction of the nanowire arrays was guided perpendicular to the surface of the substrate by the AAO template, and the crystal orientation of the nanowire arrays was selected using the single crystal Si substrate properly cut in desired orientation.
Behavior of Two Titanium Alloys in Simulated Body Fluid
Authors: Mirza Rosca Julia C. , Herrera Santana Eladio D. , Drob S. , Martinez Ortigosa Agurtzane 
Published: September 2011

ABSTRACTTitanium possesses an excellent corrosion resistance in biological environments because the titanium dioxide formed on its surface is extremely stable. When aluminium and vanadium are added to titanium in small quantities, the alloy achieves considerably higher tensile properties than of pure titanium and this alloy is used in high stress-bearing situations. But these metals may also influence the chemostatic mechanisms that are involved in the attraction of biocells. V presence can be associated with potential cytotoxic effects and adverse tissue reactions. The alloys with aluminium and iron or with aluminium and niobium occur to be more suitable for implant applications: it possesses similar corrosion resistance and mechanical properties to those of titanium-aluminium-vanadium alloy; moreover, these alloys have no toxicity.In this paper, pure Ti, Ti-6Al-7Nb and Ti-6Al-4Fe with a nanostructured surface were studied. Data about mechanical behavior are presented. The mechanical behavior was determined using optical metallography, tensile strength and Vickers microhardness.For the electrochemical measurements a conventional three-electrode cell with a Pt grid as counter electrode and saturated calomel (SCE) as reference electrode was used. AC impedance data were obtained at open circuit potential using a PAR 263A potentiostat connected with a PAR 5210 lock-in amplifier. The ESEM and EDAX observation were carried out with an environmental scanning electronic microscope Fei XL30 ESEM with LaB6-cathode attached with an energy-dispersive electron probe X-ray analyzer (EDAX Sapphire). After 3 days of immersion in simulated body fluid the nucleation of the bone growth was observed on the implant surface.It resulted that the tested oxide films presented passivation tendency and a very good stability and no form of local corrosion was detected. The mechanical data confirm the presence of an outer porous passive layer and an inner compact and protective passive layer. EIS confirms the mechanical results. The thicknesses of these layers were measured. SEM photographs of the surface and EDX profiles for the samples illustrate the appearance of a microporous layer made up of an alkaline titanate hydrogel. The apatite-forming ability of the metal is attributed to the amorphous sodium titanate that is formed on the metal during the surface treatment.The results emphasized that the surface treatment increases the passive layer adhesion to the metal surface and improves the biocompatibility of the biomedical devices inducing the bone growth on the implant surface.
Bone-Inspired Multicomponent Bionanocomposites with a Simple Drop-Cast Processing Strategy
Authors: Biswas Abhijit , Biris Alexandru S. , Bayer Ilker S. 
Published: September 2011

ABSTRACTWe describe an innovative and simple drop-cast processing strategy to create bonelike multicomponent bionanocomposite materials that consist of an organic poly(ε-caprolactone) (PCL) matrix, minerals such as hydroxyapatite (HAP) and CaCO3, and collagen fibers. The process allows morphological and structural control to achieve the desired nanostructure of the bone mimics. The fabrication method involves adding inorganic and organic components sequentially followed by controlling the growth conditions and composition. This enables organization of collagen nanofibers (∼ 100 nm) into scaffolds while simultaneously allowing nucleation and co-alignment of hydroxyapatite spheres (∼ 100 – 500 nm) within aligned, thermally stable collagen fibers in the porous PCL matrix. We achieved high calcium (26%) and oxygen (17%) within the bioscaffold and adequate phosphorous compositions comparable to the levels of bone tissues. Adequate mineralization along with high oxygen content may help maintain the required bone mineral density and revascularization for nutrient and compensate for the loss of oxygen delivered to the bone cells. Furthermore, since the bionanocomposite scaffold is made of natural materials (calcium, phosphorous and collagen) found in bone tissue, the formulation makes it an excellent biocompatible/biodegradable material. Our preliminary results suggest huge potential of these advanced bionanocomposite scaffolds for bone substitutes and tissue engineering applications.
Assessment of marine biofilm attachment and growth for antifouling surfaces under static and controlled hydrodynamic conditions
Authors: Salta Maria , Wharton Julian A. , Stoodley Paul , Wood Robert J.K. , Stokes Keith R. 
Published: September 2011

ABSTRACTThis investigation has assessed natural product antifouling performance of an isolated compound from a terrestrial source against marine biofilm forming bacteria, Cobetia marina and Marinobacter hydrocarbonoclasticus. Novel bioassay protocols using the hydrodynamic system and its well plate microfluidics capability were developed to test the in situ antifouling efficacy of the natural product against biofilm attachment under two shear stresses (0.07 and 0.3 Pa). The hydrodynamic results allowed for the first time the direct observation of the natural product influence on newly attached marine biofilms and the evolution of the antifouling affect with time. Biofilm attachment behaviour appeared to be markedly different in the presence of the natural product, illustrated by limited cluster and extracellular polymeric substance formation which suggests an interference of the bacterial attachment mechanisms. Ultimately, this is fundamental in developing greater understanding of the biofilm kinetics. These observations were confirmed using epifluoresence and confocal microscopy, with the additional corroborative data on bacterial cell integrity using the LIVE / DEAD nucleic acid kit.
Chemical functionalization of carbon nanotubes with aryl diazonium salts
Authors: Golosova Anastasia A. , Papadakis Christine M. , Jordan Rainer 
Published: September 2011

ABSTRACTWe describe a facile and direct method for the functionalization of single-walled carbon nanotubes with4’-substituted phenyls and biphenyls. By means of Raman spectroscopy and thermogravimetric analysis we demonstrate that a simple protocol of a direct chemical grafting in acetonitrile solution of the corresponding diazonium salts at room temperature results in a formation of stable aryl monolayers on carbon nanotubes.
Morphology control of copper indium disulfide nanocrystals
Authors: Kruszynska Marta , Borchert Holger , Parisi Jürgen , Kolny-Olesiak Joanna 
Published: September 2011

ABSTRACTIn this report, we present a hot-injection strategy for the synthesis of CuInS2 (CIS) nanocrystals with hexagonal, pyramidal and nanorod shapes. For that purpose copper (I) and indium (III) acetates were dissolved in oleylamine as a high-boiling solvent. Tert-dodecanethiol (t-DDT) was used as a sulfur source. It was mixed with 1-dodecanothiol (1-DDT) and injected at a high temperature. The presence of the second dodecanethiol was necessary to control the growth of the synthesized nanocrystals. We observed a strong influence of the t-DDT amount on the morphology of the CIS nanocrystals. By the variation of the injected solution uniform CIS nanorods with different aspect ratio and size were obtained.
Wafer Bonded Ge-Si Heterostructure for Avalanche Photodiode Application
Authors: Byun Ki Yeol , Hayes John , Gity Farzan , Corbett Brian , Colinge Cindy 
Published: September 2011

ABSTRACTIn this study, we investigate directly bonded germanium-silicon interfaces to facilitate the development of high quality germanium silicon integration for Avalanche photodiode application. Angle resolved x-ray photoelectron spectroscopy data is presented which provides the chemical composition of the germanium surfaces as a function of the surface passivation. The hetero-structure is characterized by measuring forward and reverse current and comparing the measured results to TCAD simulation. The physical structure of hetero-junction is supported by high resolution transmission electron microscopy.
Ion implantation of Carbon and Silicon into Ge2Sb2Te5: Ion Profiles and Post Crystallization Redistribution
Authors: Cohen Guy M. , Raoux Simone , Hopstaken Marinus , Maurer Siegfried 
Published: September 2011

ABSTRACTIon implantation of Ge2Sb2Te5 (GST) enables localized doping of the film by using conventional lithography. Although the doped region dimensions and the doping concentration profile are defined by the opening in the mask and the ion energy, longitudinal and lateral straggling of implanted ions leads to a spread in the ions final location. Additionally, a thermal treatment such as one that induces a phase transition may lead to redistribution of the implanted dopants and further increase the spread. In this work we demonstrate doping of GST by ion implantation. Using Secondary Ion Mass Spectrometry (SIMS) we studied the as-implanted doping profiles obtain by ion implantation of carbon and silicon into GST. We also investigated by SIMS the dopant redistribution following a recrystallization annealing. The as-implanted ion profiles were found to be in fair agreement with TRIM simulation. The dopants profiles show little change after a crystallization annealing at 200°C for silicon doping and at 350°C for carbon doping.
Electro-migration of Zinc during current-assisted pressure sintering of β-Zn4Sb3 – effect of process parameters and its influence on the thermoelectric properties
Authors: Dasgupta T. , Stiewe C. , Boettcher L. , Yin H. , Iversen B.B. , Mueller E. 
Published: September 2011

ABSTRACTCompaction of β-Zn4Sb3 was carried out by current-assisted short term sintering under pressure (STS) using different material and process parameters. Surface Seebeck mapping (PSM) of the compacted specimens (along the uniaxial pressing direction) shows a wide gradation ranging from ∼40–180 μV/K due to electro-migration of Zinc along the current direction. The wide distribution of S corresponds to a mixture of Zn-Sb phases [1] which arise depending on the extent of Zinc migration during the STS process. Variation in the material and process parameters (average particle size, heating rate, compaction time/temperature) results in different spatial distribution of S. Measurements of electrical (σ), thermal (κ) conductivities and Seebeck (S) coefficients between room temperature and 523 K were carried out on two specimens having different average S values and distributions as observed by the PSM. The results indicate an increase in the lattice thermal conductivity (κL) and subsequent lower ZT in the specimens compared to the reported values for β-Zn4Sb3.
Investigation into the thermoelectric properties of GaSb/InAs superlattice structures
Authors: Barletta Philip T. , Bulman Gary E. , Dezsi Geza , Colpitts Thomas S. , Venkatasubramanian Rama 
Published: September 2011

ABSTRACTWe report on our investigation into the use of III-V superlattice structures for thermoelectric (TE) applications. Preliminary review of III-V materials trends indicate that the GaSb/InAs superlattice system should offer one of the best potentials for high thermoelectric performance in the 500K-800K range. MOCVD growth of GaSb/InAs superlattice structures was carried out, and relevant structural, thermal, and electrical characterization has been performed. TEM and XRD results demonstrate a well-ordered superlattice structure. Thermal conductivity measurements reveal a reduction in the room-temperature thermal conductivity of GaSb/InAs superlattices (4.4-10.0 W/m-K), relative to either binary GaSb (32 W/m-K) or InAs (27 W/m-K). Additionally, we have worked to optimize the thermoelectric power factor (α2σ), studying both Se- and Te-doping of the superlattice structures, in an effort to demonstrate optimal thermoelectric performance. Our results demonstrate a maximum ZT of 0.36 at 400K for optimally doped n-type GaSb/InAs superlattice structures.
Design and Demonstration of Concentration Cells for Small Scale Energy Harvesting based on Reverse Electrodialysis
Authors: Sadeghian Ramin Banan , Pantchenko Oxana , Tate Daniel Scott , Shabani Javad , Zarandi Mehrdad M. , Shakouri Ali 
Published: September 2011

ABSTRACTExperimental results are presented to demonstrate feasibility of small scale power generation using static reverse electrodialysis (RED) of CuSO4 solutions. In contrast to conventional macro scale reverse electrodialysis, the concentrated and diluate compartments were not refreshed, resulting in limited power delivery times. This is important in energy harvesting applications from limited supply of ionic concentrations. Maximum output power density of 0.17 μW·cm−2 was recorded using microfiltration membranes. The evolution of the open circuit output voltage with time is accurately modeled at various concentration ratios.
Correlated photoluminescence spectroscopy investigation of grain boundaries and diffusion processes in nanocrystalline and amorphous silicon (nc-Si:H) mixtures
Authors: Fields Jeremy D. , Kiriluk K. G. , Bobela D. C. , Gedvilas L. , Taylor P. C. 
Published: September 2011

ABSTRACTPhotoluminescence (PL) spectra obtained with correlated set of experiments investigating grain boundary characteristics and diffusion processes in nanocrystalline silicon alloys (nc-Si:H), provide insight regarding formation and passivation of electronic defects in these regions. Based upon current results and previous works we believe thermally driven processes induce a PL band centered at 0.7 eV upon thermal annealing, and most likely involve diffusion of hydrogen and oxygen near interfaces. A nc-Si:H sample set with varied crystal volume fraction, Xc, was subject to thermal annealing treatments at different temperatures – each exceeding the deposition temperature. Fourier-transform photoluminescence (FTPL) and Fourier-transform infrared absorption spectroscopy (FTIR), were employed to correlate the relative 0.7 eV defect band emergence with compositional changes indicative of Si–Hx and Si–O species, for each sample, at each temperature, respectively. Hydrogen effusion data provide additional perspective.We find the Xc to strongly affect susceptibility of nc-Si:H to oxygen related effects. The higher the Xc, the more readily oxygen penetrates the nc-Si:H network. We attribute this relationship to elevated diffusivity of oxygen in highly crystalline nc-Si:H materials, owing to their abundance of gain boundaries and interfaces, which serve as pathways for impurity migration. These findings corroborate the expectation that oxygen impurities and diffusion processes contribute to development of microstructural features giving rise to radiative recombination through deep defects in nc-Si:H.
ENHANCING PHOTOCURRENT IN UNANNEALED NiSx/CdS PHOTOELECTROCHEMICAL SYSTEM FOR WATER SPLITTING AND HYDROGEN PRODUCTION
Authors: Zhang Ning , Guo Liejin 
Published: September 2011

ABSTRACTIn this work, NiSx was deposited on FTO by chemical bath and worked as the inner layer in order to enhance the photocurrent of CdS film. It is found the unannealed CdS/NiSx had a higher photocurrent than unannealed CdS, but after annealing, the photocurrent of CdS/NiSx showed dramatical decrease. The mechanism was discussed in detail by UPS and current-potential curves.
Ultra Low-k Materials Based on Self-Assembled Organic Polymers
Authors: Pantouvaki M. , Zhao L. , Huffman C. , Vanstreels K. , Ciofi I. , Vereecke G. , Conard T. , Ono Y. , Nakajima M. , Nakatani K. , Beyer G. P. , Baklanov M. R. 
Published: September 2011

ABSTRACTThe material properties of two ultra low-k organic polymers are characterized for copper interconnect integration. The k-values are 2.2-2.3 for both. Compared to OSG materials of similar k-values, these polymers have lower porosity and smaller pore size, achieved using selfassembled chemistry. Both materials demonstrate excellent resistance to plasma damage: no water uptake was detected after exposure to selected etching plasmas. This characteristic, combined with the small pore size and low porosity, results in the successful integration of the organic low-ks in 80 nm spacing with no significant increase in the integrated k-values.It is found that higher open porosity in polymer A is accompanied by higher leakage current, which is not however linked to lower dielectric breakdown lifetimes.