bluuebunny/crossref_metadata_2025_split huggingface dataset:
Linear finite elements with orthogonal discontinuous basis functions for explicit earthquake ground motion modeling
Authors: Ichimura T. , Hori M. , Wijerathne M. L. L. 
Published: December 2010

AbstractThe dynamic explicit finite element method is commonly used in earthquake ground motion modeling. In this method, the element mass matrix is approximately lumped, which may lead to numerical dispersion. On the other hand, the orthogonal finite element method, based on orthogonal polynomial basis functions, naturally derives a lumped diagonal mass matrix and can be applied to dynamic explicit finite element analysis. In this paper, we propose finite elements based on orthogonal discontinuous basis functions, the element mass matrices of which are lumped without approximation. Orthogonal discontinuous basis functions are used to improve the accuracy and reduce the numerical dispersion in earthquake ground motion modeling. We present a detailed formulation of the 4‐node tetrahedral and 8‐node hexahedral elements. The relationship between the proposed finite elements and conventional finite elements is investigated, and the solutions obtained from the conventional explicit finite element method are compared with analytical solutions to verify the numerical dispersion caused by the lumping approximation. Comparison of solutions obtained with the proposed finite elements to analytical solutions demonstrates the usefulness of the technique. Examples are also presented to illustrate the effectiveness of the proposed method in earthquake ground motion modeling in the actual three‐dimensional crust structure. Copyright © 2010 John Wiley & Sons, Ltd.
A level set based model for damage growth: The thick level set approach
Authors: Moës N. , Stolz C. , Bernard P.‐E. , Chevaugeon N. 
Published: December 2010

AbstractIn this paper, we introduce a new way to model damage growth in solids. A level set is used to separate the undamaged zone from the damaged zone. In the damaged zone, the damage variable is an explicit function of the level set. This function is a parameter of the model. Beyond a critical length, we assume the material to be totally damaged, thus allowing a straightforward transition to fracture. The damage growth is expressed as a level set propagation. The configurational force driving the damage front is non‐local in the sense that it averages information over the thickness in the wake of the front. The computational and theoretical advantages of the new damage model are stressed. Numerical examples demonstrate the capability of the new model to initiate cracks and propagate them even in complex topological patterns (branching and merging for instance). Copyright © 2010 John Wiley & Sons, Ltd.
Synthesis and phase‐separation behavior of α,ω‐difunctionalized diblock copolymers
Authors: Werner Saija , Pospiech Doris , Jehnichen Dieter , Eckstein Kathrin , Komber Hartmut , Friedel Peter , Janke Andreas , Näther Franziskus , Reuter Uta , Voit Brigitte , Taurino Rosa , Messori Massimo 
Published: December 2010

AbstractA series of diblock copolymers of n‐pentyl methacrylate and methyl methacrylate (PPMA/PMMA BCP) with one or two terminal functional groups was prepared by sequential anionic polymerization of PMA and MMA using an allyl‐functionalized initiator and/or and end‐capping with allyl bromide. Allyl functional groups were successfully converted into OH groups by hydroboration. The morphology in bulk was examined by temperature‐dependent small‐angle X‐ray measurements (T‐SAXS) and transmission electron microscopy (TEM) showing that functional groups induced a weak change in d‐spacings L0 as well as in the thermal expansion behavior. T‐SAXS proved that the lamellar morphologies were stable over multiple heating/cooling cycles without order‐disorder transition (ODT) until 300 °C. While non‐functionalized BCP formed parallel lamellae morphologies, additional OH‐termination at the PMMA block forced in very thin films (ratio between film thickness and lamellar d‐spacing below 1) the generation of perpendicular lamellae morphology through the whole film thickness, as shown by Grazing‐incidence small‐angle X‐ray scattering experiments (GISAXS) measurements. Functionalized BCP were successfully used in thin films as templates for silica nanoparticles in an in‐situ sol–gel process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Synthesis of backbone thermo and pH dual‐responsive hyperbranched poly(amine‐ether)s through proton‐transfer polymerization
Authors: Pang Yan , Zhu Qi , Zhou Dongliang , Liu Jinyao , Chen Yan , Su Yue , Yan Deyue , Zhu Xinyuan , Zhu Bangshang 
Published: December 2010

AbstractStimuli‐responsive hyperbranched polymers have attracted great attention in recent years because of their wide applications in biomedicine. Through proton‐transfer polymerization of triethanolamine and 1,2,7,8‐diepoxyoctane with the help of potassium hydride, a series of novel backbone thermo and pH dual‐responsive hyperbranched poly(amine‐ether)s were prepared successfully in one‐pot. The degrees of branching of the resulting polymers were at 0.40–0.49. Turbidity measurements revealed that hyperbranched poly(amine‐ether)s exhibited thermo and pH dual‐responsive properties in water. Importantly, these responsivities could be readily adjusted by changing the polymer composition as well as the polymer concentration in aqueous solution. Moreover, in vitro evaluation demonstrated that hyperbranched poly(amine‐ether)s showed low cytotoxicity and efficient cell internalization against NIH 3T3 cell lines. These results suggest that these backbone thermo and pH dual‐responsive hyperbranched poly(amine‐ether)s are promising materials for biomedicine. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Atom transfer radical polymerization using activators regenerated by electron transfer of acrylonitrile in 1‐(1‐ethoxycarbonylethyl)‐3‐methylimidazolium hexafluorophospate
Authors: Chen Hou , Chen Lingfang , Wang Chunhua , Qu Rongjun 
Published: December 2010

AbstractAtom transfer radical polymerization using activators regenerated by electron transfer (ARGET ATRP) of acrylonitrile (AN) was first approached with 1‐(1‐ethoxycarbonylethyl)‐3‐methylimidazolium tetrafluoroborate ([ecemim][BF4]) as reaction medium and tin(II) bis(2‐ethylhexanoate) (Sn(EH)2) as reducing agent in the presence of air. When compared with in bulk, an obvious increase of polymer isotacticity was observed for ARGET ATRP of AN in 1‐(1‐ethoxycarbonylethyl)‐3‐methylimidazolium hexafluorophospate ([ecemim][PF6]), the reaction rate of ARGET ATRP of AN in [ecemim][PF6] was higher and the polymerization process was better controlled. The block copolymer polyacrylonitrile‐block‐poly(methyl methacrylate) with molecular weight at 69,750, distribution at 1.34, and isotacticity at 0.36 was successfully obtained in [ecemim][PF6]. [Ecemim][PF6] and the catalyst system were recycled and reused and had no effect on the living nature of polymerization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Kinetics of electron induced desorption of hydrogen in nanostructured porous silicon
Authors: Ruano G. D. , Ferron J. , Arce R. D. , Koropecki R. R. 
Published: December 2010

AbstractWe found that nanostructured porous silicon obtained by anodization desorbs hydrogen under electron bombardment. The kinetics of this electron‐induced effusion can be explained neither in terms of thermal processes nor by direct transference of energy from the impinging electron to the SiH bonds. We show that short lived‐large energy fluctuations (SLEFs), occurring during bimolecular recombination processes of carriers produce both, a midgap increment of the density of electronic defect states and hydrogen desorption.
Influence of the doping concentration on crystallographic pore growth on n‐type InP and GaAs
Authors: Leisner Malte , Dorow‐Gerspach Daniel , Carstensen Jürgen , Föll Helmut 
Published: December 2010

AbstractThe growth of crystallographical pores (crysto pores) in n‐type InP and GaAs has been investigated in detail in this work. The dependence on several experimental parameters, like the substrate doping concentration ND, the etching current density j, nucleation, and etching time lead to a large amount of data. It could be shown that the data can be consistently understood in the framework of a simple model for crysto pore growth developed earlier by the authors. The stochastic nature of the model allowed for its implementation into 3‐dimensional Monte‐Carlo simulations, which were already able to reproduce the major features of crysto pores, as well as many detailed results. In this framework, this work serves as expansion of the parameter space which is subjected to the simulations, since the aforementioned parameters serve as free input parameters for the simulations. First results indicate that the main model parameters, the branching probabilities at pore tips and walls (ktips and kwall) are higher for InP as compared to GaAs. This effect has been interpreted as caused by a stronger passivation of GaAs surfaces by HCl in comparison to InP.
The use of porous silicon layers in thin‐film silicon solar cells
Authors: Van Hoeymissen Jan , Depauw Valerie , Kuzma‐Filipek Izabela , Van Nieuwenhuysen Kris , Payo Maria Recaman , Qiu Yu , Gordon Ivan , Poortmans Jef 
Published: December 2010

AbstractIn the quest for lowering the manufacturing cost of silicon solar cells, imec has been working successfully on two crystalline Si ‘thin‐film’ cell concepts. In a first concept, a 20 µm‐thin Si solar cell is epitaxially grown on top of a porous Si‐based Bragg‐type reflector which is electrochemically etched in a low‐cost UMG Si substrate. Large area solar cells with efficiencies of 15.2% have been made, using (semi‐)industrial processing tools. This clearly demonstrates that this cell concept has almost reached the stage of industrial application. In a second, longer‐term approach, a 1–5 µm‐thin, stand‐alone mono‐crystalline film is created based on the controlled annealing of an ordered macroporous silicon layer (the ‘Epi‐free’ process). With this very thin Si layer, a simple proof‐of‐concept solar cell has been made exhibiting an efficiency of 4%. By optimizing the cell process in terms of light trapping and passivation, efficiencies over 15% can be expected from this technology.
Macro and quasi‐mesoporous silicon by self‐assembling and metal assisted etching
Authors: Boarino L. , Enrico E. , De Leo N. , Celegato F. , Tiberto P. , Sparnacci Katia , Laus M. 
Published: December 2010

AbstractThe combination of two recent techniques developed in the last years demonstrates the possibility to obtain regular and semi‐ordered macro and mesopores on any type of silicon substrates and with holes diameter ranging from 800 to 60 nm and less. Self‐assembling of polystyrene nanospheres (PSNS) is obtained by floating technique, then the 2D crystal is lifted on a silicon substrate with a 30 nm silver thin film deposited by thermal evaporation or sputtering. The nanospheres are then reduced in diameter by reactive ion etching (RIE) in oxygen plasma, then the samples are exposed to Ar ions sputter‐etching (SE) for thin film structuration. At this point of the process the polystyrene nanosphere mask is removed and a metal assisted etching (MAE) of few minutes is performed. Ordered and regular pores of diameters ranging from 500 to 60 nm have been obtained.magnified image
Macropores (450 nm) obtained by self‐assembly nanolithography and metal assisted etching.
Characteristics of SnSe and SnSe2 thin films grown onto polycrystalline SnO2‐coated glass substrates
Authors: Guillén C. , Montero J. , Herrero J. 
Published: December 2010

AbstractTin selenide thin films have been prepared by selenization of sputtered tin layers and have been analyzed comparatively onto bare and SnO2‐coated glass substrates. In particular, the effects of the selenization temperature and the polycrystalline substrate nature on the stoichiometry and physical properties of the layers were investigated. X‐ray diffraction was used to determine the crystalline phases and their structure, scanning electron microscopy to observe the surface topography, energy‐dispersive X‐ray analysis to establish the film composition, and spectrophotometry to determine the optical absorption, all these properties correlated to the experimental parameters. By using polycrystalline tin oxide coatings it is possible to achieve a significant crystalline enhancement for the SnSe and SnSe2 phases identified, being the Se:Sn atomic proportion, as well as the optical absorption, highly dependent on the selenization temperature apart from the substrate nature.
Manipulation of absorption in Si thin films with ordered nanostructures
Authors: Lu Yalin , Reinhardt Kitt 
Published: December 2010

AbstractSilicon thin film solar cells have attracted an increasing attention because of the potential to provide clean energy at relatively low cost. Currently, their performances are limited by poor light absorption and low efficiency carrier collection. In this research with a goal to enhance the light absorption, integration with metallic surface nanostructures to thin film silicon solar cells was investigated. Large, broadband, and polarization‐insensitive light absorption enhancement was verified. The enhancement was explained by a few possible mechanisms such as the planar cavity resonance, surface plasmonic resonance (SPR), planar waveguide coupling, etc. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hall mobility drops in disordered boron‐doped Czochralski silicon compensated by thermal donors activation
Authors: Veirman J. , Dubois S. , Enjalbert N. , Garandet J. P. , Heslinga D. R. , Lemiti M. 
Published: December 2010

AbstractWe investigated the variation of majority carrier Hall mobility in Boron‐doped Electronic‐Grade Silicon progressively compensated by Double Thermal Donors. We show a strong reduction in Hall mobility around full compensation in both p‐ and n‐type Si. We relate this drop in mobility to a rising inhomogeneity of the electrostatic potential associated with increasing compensation, as revealed by minority carrier diffusion length mapping. Two consequences of this inhomogeneity are considered to explain our data: 1) a physical scattering of carriers by submicronic non‐uniformity of the electrostatic potential and 2) a bias in the determination of the Hall mobility in highly compensated Si. We show that the Hall Effect is indeed affected at high compensation level by the large‐scale inhomogeneity in carrier density related to non‐uniform dopant distributions. In parallel, we also discuss the possible existence of microscopic variations in dopants distribution that could lead to physical reductions in mobility. We eventually suggest suitable experiments that could reveal them. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quantumchemical simulation of diffusion in alloys: diffusion of interstitial oxygen atoms in Si1‐xGex
Authors: Gusakov Vasilii 
Published: December 2010

AbstractIn the present work the results of theoretical analysis of the process of diffusion of covalently bonded atoms (interstitial oxygen atoms) in Si1‐xGex alloys are presented. The diffusion coefficient (activation energy and preexponential factor) was calculated by means of quantumchemical simulations (NDDO PM5) and the dependences of the activation energy and preexponential factor on Ge atoms concentration (x) were analyzed with the use of the percolation theory. It is shown that a significant decrease in the diffusion coefficient of interstitial oxygen atoms in Si1‐xGex (x<0.05) compared to the value in pure silicon is caused not only by changes in activation energy but also by a decrease of the preexponential factor. The alloy‐induced decrease in the preexponential factor is associated with removal of the degeneracy of the number of equivalent diffusion paths. The dependences obtained describe well experimentally observed changes in the diffusion coefficient of interstitial oxygen atoms and in the formation rate of oxygen‐related thermal donors in Si1‐xGex alloys. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phosphorous gettering in acidic textured multicrystalline solar cells
Authors: Montesdeoca‐Santana A. , Jiménez‐Rodríguez E. , González‐Díaz B. , Díaz‐Herrera B. , Rinio M. , Borchert D. , Hernández‐Rodríguez C. , Guerrero‐Lemus R. 
Published: December 2010

AbstractThe influence of phosphorus gettering is studied in this work applied to an acidic textured multicrystalline silicon substrate. The texturization was achieved with an HF/HNO3 solution leading to nanostructures on the silicon surface. It has been demonstrated in previous works that this textured surface decreases the reflectance on the solar cell and increases the surface area improving the photon collection and enhancing the short circuit current. The present study investigates the effect on the minority carrier lifetime of the phosphorous diffusion when it is carried out on this textured surface. The lifetime is measured by means microwave photoconductance decay and quasi steady state phototoconductance devices. The diffused textured wafers are used to fabricate solar cells and their electrical parameters are analyzed. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A comparative study on different textured surfaces passivated with amorphous silicon
Authors: Montesdeoca‐Santana A. , Ziegler J. , Lindekugel S. , Jiménez‐Rodríguez E. , Keipert‐Colberg S. , Müller S. , Krause C. , Borchert D. , Guerrero‐Lemus R. 
Published: December 2010

AbstractIn this work it is studied the influence of different texturizations on minority carrier lifetime of n‐type Fz silicon wafers passivated with thin amorphous silicon layers (a‐Si:H). For amorphous‐crystalline silicon based heterojunction solar cells a good light trapping is essential. Therefore a front side texturization is needed as it can increase the photocurrent due to its low reflectance. The interface between the amorphous emitter and the crystalline base plays an important role for two reasons: firstly, the micromorphic surface topology can generate different deposition regimes that results in different lifetimes, and secondly, the nanomorphic structure also show influences on the lifetime. We compare two different types of wet chemical texturizations by different carbonate solutions and a plasma texturization subsequently covered by a thin layer of a‐Si:H by means of plasma‐enhanced chemical vapor deposition. The surface morphology produced by the texturization on the silicon wafers is analyzed by scanning electron microscopy and atomic force microscopy. The quality of the passivation of the textured silicon surface by the a‐Si:H deposition is evaluated by measuring minority carrier lifetimes with a microwave photo‐conductance decay and quasi steady state photo‐conductance devices. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variation in the structure and optical properties of polymorphous silicon thin films using dichlorosilane as silicon precursor
Authors: Remolina A. , Hamui L. , Monroy B. M. , García‐Sánchez M. F. , Ponce A. , Picquart M. , Santana G. 
Published: December 2010

AbstractPolymorphous silicon thin films were obtained by plasma enhanced chemical vapor deposition using dichlorosilane as silicon precursor. The RF power and the dichlorosilane to hydrogen flow rate ratio were varied to obtain different crystalline fractions and average sizes of silicon nanocrystals embedded in the amorphous silicon matrix. Microscopy images confirmed the existence of nanocrystallites with averages sizes between 2 and 6 nm. Broader size distributions were obtained with increasing RF power. Raman results confirmed that different nanocrystalline fractions (from 12% to 54%) can be achieved in these films by regulating the selected growth parameters. The optical band gap calculated by the Tauc model from UV‐visible transmittance measurements varies between 1.8 to 2.3 eV. The relationship between the optical properties is discussed in terms of the different nanostructures of the samples. Depending on their absorption properties and effective band gap, these materials can be suitable for application in thin film solar cell devices (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optoelectronic enhancement of monocrystalline silicon solar cells by porous silicon‐assisted mechanical grooving
Authors: Ben Rabha Mohamed , Mohamed Seifeddine Belhadj , Dimassi Wissem , Gaidi Mounir , Ezzaouia Hatem , Bessais Brahim 
Published: December 2010

AbstractOne of the most important factors influencing silicon solar cells performances is the front side reflectivity. Consequently, new methods for efficient reduction of this reflectivity are searched. This has always been done by creating a rough surface that enables incident light of being absorbed within the solar cell. Combination of texturization‐porous silicon surface treatment was found to be an attractive technical solution for lowering the reflectivity of monocrystalline silicon (c‐Si). The texturization of the monocrystalline silicon wafer was carried out by means of mechanical grooving. A specific etching procedure was then applied to form a thin porous silicon layer enabling to remove mechanical damages. This simple and low cost method reduces the total reflectivity from 29% to 7% in the 300 ‐ 950 nm wavelength range and enhances the diffusion length of the minority carriers from 100 µm to 790 µm (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ulrich Gösele – 35 years of research: From defects and diffusion to nanomaterials
Authors: Zacharias Margit 
Published: December 2010

AbstractQuite inconceivable for all his friends, colleagues and co‐workers Prof. Ulrich Gösele, Director of the Max Planck Institute of Microstructure Physics at Halle/Saale, died unexpectedly on November 8th 2009. We mourn for Ulrich Gösele as an outstanding scientist who was all the time full of new ideas. With 650 papers and a similar number of conference papers, more than 20.000 citations in 2009 and an impressive H factor of 67 at the time of his dead, he put his foot prints actually into a number of fields in physics and material science. His opinions were widely sought by scientists as well as politics. He was an advisor for local and state government, changing the scientific and innovative perspective of the Halle/Saale area. He did not fail to give advice to the best of his knowledge. And even if not all agreed with all of his opinions, his statements were mostly going to the core of the topic. It was inspiring talking to him. He had a deep sense of responsibilities for the sources entrusted to him, being its funding or peoples. From my own experience I can say, that in all the long discussions we had during the years I had the pleasure to be in his institute, I enjoyed his spirit in science but also how he was able to give confidence for the research plans we had (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)