bluuebunny/crossref_metadata_2025_split huggingface dataset:
On LP relaxations for the pattern minimization problem
Authors: Aloisio Alessandro , Arbib Claudio , Marinelli Fabrizio 
Published: December 2010

AbstractWe discuss two formulations of the pattern minimization problem: (1) introduced by Vanderbeck, and (2) obtained adding setup variables to the cutting stock formulation by Gilmore‐Gomory. Let z(u) be the bound given by the linear relaxation of (i) under a given vector u of parameters. We show that z(u) ≥ z(u) and provide a class of instances for which the inequality holds strict. We observe that the linear relaxation of both formulations can be solved by the same column generation procedure and discuss the critical role of parameter u. The article is completed by a numerical test comparing the lower bounds obtained through (1) and (2) for different values of u. © 2011 Wiley Periodicals, Inc. NETWORKS, 2011
Influence of diamond nanoparticles on the thermal properties of benzocyclobutene (BCB)
Authors: Gracias A. , Tokranova N. , Thelen B. C. M. , Castracane J. 
Published: December 2010

AbstractThis paper describes the influence of diamond nanoparticles on the modification of the thermal properties of benzocyclobutene (BCB) which is used for three‐dimensional (3D) wafer‐to‐wafer integration. Hybrid nanocomposites containing mixtures of 0.5–10 weight% (wt.%) diamond nanoparticles [average particle size (APS): 10 nm] in BCB were analyzed using thermal gravimetric analysis (TGA) and flash diffusivity techniques. Measurements show that the addition of nanoparticles significantly increases the decomposition temperature. Diffusivity measurements and subsequent calculations of thermal conductivity suggest that the inclusion of nanoparticles only slightly improves the conductivity.
Highly indistinguishable photons from a quantum dot in a microcavity
Authors: Weiler Stefanie , Ulhaq Ata , Ulrich Sven M. , Reitzenstein Stephan , Löffler Andreas , Forchel Alfred , Michler Peter 
Published: December 2010

AbstractWe investigated the indistinguishability of photons emitted by single self‐assembled (In,Ga)As/GaAs quantum dots (QDs) coupled to the fundamental mode (FM) of a pillar microcavity. By systematic pre‐characterization, optimum conditions with respect to fast radiative decay (Purcell enhancement), long coherence time, and close to background‐free single‐photon emission have been derived. For different spectral detunings between QD and FM emission, Hong‐Ou‐Mandel‐type (HOM) two‐photon interference has been measured as a function of temporal photon wavepacket overlap. Detailed analysis of our data (under consideration of setup limitations) anticipates the generation of highly indistinguishable photons with up to VHOM = 0.82 visibility.
Evidence of two disorder scales in Ga(AsBi)
Authors: Imhof Sebastian , Wagner Christian , Chernikov Alexej , Koch Martin , Kolata Kolja , Köster Niko S. , Chatterjee Sangam , Koch Stephan W. , Lu Xiangfeng , Johnson Shane R. , Beaton Daniel A. , Tiedje Thomas , Rubel Oleg , Thränhardt Angela 
Published: December 2010

AbstractTemperature‐dependent photoluminescence in a Ga(AsBi) structure is modelled in an excitonic hopping model and compared to experiment. It is shown that theory and experiment cannot be brought into agreement when using a single energy scale. Thus, a second energy scale is introduced, resulting in a good agreement between theory and experiment. The two scales are identified with spatially large alloy disorder and additional cluster states subdividing this first scale.
A semiconductor model for the single quantum dot laser
Authors: Gies C. , Florian M. , Gartner P. , Jahnke F. 
Published: December 2010

AbstractThe emission properties of a single quantum‐dot laser are studied on the basis of a semiconductor model. Coulomb interaction and excitation‐induced effects like dephasing and screening lead to an interplay of excitonic and biexcitonic emission contributions at the cavity frequency. In the input/output curve and photon statistics, this leads to novel features that cannot be explained in terms of atomic models for a single‐emitter laser. Rather, they are a result of the particular properties of the QD emitter.
First‐principles modeling of the interactions of iron impurities with graphene and graphite
Authors: Boukhvalov Danil W. 
Published: December 2010

AbstractResults of first‐principles modeling of interactions of graphene and graphite with iron impurities predict the colossal difference between these two carbon allotropes. Insertion of the iron atoms between the planes of graphite is much more energetically favorable than adsorption of the iron ad atom at the graphite or graphene surface. High mobility of iron ad atom over graphite surface and within bulk graphite is reported. Calculated values of formation energies for the substitutional iron impurities suggest that iron is more destructive for graphite than for graphene. This effect caused formation of a uniform carbon environment of the iron atom inside the multilayer system. In contrast to graphene, segregation of the substitutional iron impurities in graphite under ambient conditions is not energetically favorable. Enhancement of interlayer bonding in contaminated graphite and purity of graphene from iron impurities are also reported.magnified image
Interstitial iron ad atom (left) and pair of substitutional iron ad atoms (right) inside bulk graphite.
Study of microwave surface resistance of type‐II superconductors carrying transport current
Authors: Yıldız Şükrü , İnanır Fedai , Kölemen Uğur 
Published: December 2010

AbstractWe investigate the microwave surface resistance of an infinitely long type‐II superconductor in the critical state carrying transport DC current, in the absence and in the presence of external magnetic fields. Calculations include both different cooling processes and various current and field arrangements. Theoretical results in field‐cooled sample show that the microwave surface resistance exhibits an initial slow variation followed by a faster one above a threshold current value. This occurs when the current induced magnetic field generates fluxons of opposite directions on the two sample edges.
Hydrogen‐related defects in boron doped p‐type silicon
Authors: Malmbekk H. , Vines L. , Monakhov E. V. , Svensson B. G. 
Published: December 2010

AbstractThe interaction between hydrogen and irradiation‐induced defects in boron‐doped silicon has been investigated in search of a passivation procedure for intrinsic defects, applicable for the solar cell industry. Deep level transient spectroscopy (DLTS) and minority carrier transient spectroscopy (MCTS) have been applied for defect characterization of proton implanted p‐type Fz and Cz‐Si, with a boron concentration of 2x1016 cm–3 and 4x1014 cm–3, respectively. MCTS reveals a dominant electron trap located 0.22 eV below the conduction band edge (Ec) which is commonly ascribed to a boron‐interstitial oxygen‐interstitial complex (BiOi). DLTS reveals several hole traps at 0.09, 0.18, 0.25, 0.35, 0.46 and 0.52 eV above the valence band edge (Ev). The levels at 0.09, 0.18 and 0.35 eV are identified as the carbon‐interstitial carbon‐substitutional pair (CiCs), the divacancy center (V2) and the carbon‐interstitial oxygen‐interstitial pair (K‐center), while the levels located at 0.25 and 0.52 eV have previously been suggested to result from defect complexes containing hydrogen. After annealing at 100‐200 °C for 30 min the measurements show that the H(0.25) level increases in amplitude, while V2 and the K‐center decrease in amplitude. Heat treatment at 125 °C leads to almost complete disappearance of V2 and the K‐center in the Fz samples. The obtained results suggest that the loss of V2 and the K‐center is due to interaction with H. A possible identification of the Ev+0.2 5eV level will be discussed. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dry texturing of mc‐Si wafers
Authors: Agarwal Garima , De Iuliis Simona , Serenelli Luca , Salza Enrico , Tucci Mario 
Published: December 2010

AbstractTexturing of mc‐Si is a prevailing research topic to improve solar cell efficiency in production. Surface texturing for enhanced absorption in Si has been historically obtained by creating randomly distributed pyramids using anisotropic etchants; but this preferential etching works only on single crystalline silicon because of its crystallographic orientations. A low‐cost, large area, random, mask‐less texturing scheme is expected to significantly impact terrestrial PV technology and reduce the amount of wet‐chemical waste. We propose an approach based on randomly etched mc‐Si by RIE system using NF3 instead of SF6 or CF4 to reduce the detrimental formation of carbonaceous or sulfurous contamination at the silicon surface, which results in a surface recombination. To obtain a fast process we have investigated the effect of the chemical etching due to the NF3 radicals and the ion bombardment induced by Ar. We have found that Arions promote a helpful surface pre‐conditioning, while fluorine radicals, produced by NF3 dissociation, are needed to increase the Si etching rate. Different combinations of flux ratios, gas pressures and RF power have been explored. Efforts have been devoted in obtaining a homogeneous texture on large area wafers, which is inescapable for industrialization. After 10 minutes process effective reflectance values have been measured within the range of 12‐14%, and with a‐Si/SiNx the value reduced to 7%. Post‐processing minority carrier lifetime values in the range of 10 microseconds have been measured without applying any further chemical cleaning. Additionally, microscopic analysis has been performed to evaluate the surface microstructure morphology (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulations of silicon nanocrystals embedded in oxide for nanoelectronic applications
Authors: Armeanu Dumitru , Leroy Yann , Cordan Anne‐Sophie 
Published: December 2010

AbstractThe purpose of this paper is to report the results of a study on single electron charging of a nanocrystal floating gate in a metal‐oxide‐semiconductor transistor. Our model is based on the geometrical and physical parameters of hypothetically spherical nanocrystals embedded in oxide (nanocrystal radius, distance between nanocrystals, oxide thickness, bulk band structure). This model can be numerically solved through a two‐dimensional finite element approach.The channel and gate electrodes are described through energy subbands, and the silicon nanocrystal through discrete energy levels. Two types of tunnel transport are considered here: indirect tunneling from the channel to the nanocrystal and then from the nanocrystal to the gate, and direct tunneling from the channel to the gate. We show that the latter type can be neglected for the current range of nanocrystal densities used for memory applications (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Scanning tunneling microscopy investigations of the epitaxial growth of ZrB2 on Si(111)
Authors: Fleurence Antoine , Yamada‐Takamura Yukiko 
Published: December 2010

AbstractBy means of Scanning Tunneling Microscopy (STM), elongated structures observed in ZrB2 thin films epitaxially grown on Si(111) have been determined to be ZrB2 crystallites misoriented from the dominant orientation of ZrB2(0001)//Si(111). The epitaxial relationships ZrB2(11$ \bar 2 $0)//Si(111) and ZrB2(1$ \bar 1 $00)//Si(111) were identified together with the in‐plane ZrB2[0001]//Si[1$ \bar 1 $0] orientation. The surface of these crystallites exhibits a well‐defined ZrB2 (1$ \bar 1 $00) – (2 × 6) surface re‐ construction, which is observed for the first time. The presence of large ZrB2(1$ \bar 1 $00) facets indicates that this surface contributes significantly to the growth of misoriented ZrB2 crystallites as well as to their elongated shape. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Research on efficiency limiting defects and defect engineering in silicon solar cells ‐ results of the German research cluster SolarFocus
Authors: Riepe Stephan , Reis Isolde E. , Kwapil Wolfram , Falkenberg Marie Aylin , Schön Jonas , Behnken Herfried , Bauer Jan , Kreßner‐Kiel Denise , Seifert Winfried , Koch Wolfgang 
Published: December 2010

AbstractDefects in multicrystalline silicon for photovoltaic applications and their impact on solar cell parameters have been investigated in the material research network project SolarFocus. A series of multicrystalline silicon ingots of ultrapure feedstock material were cast with intentional addition of typical transition metal impurities (Fe, Cu, Cr) and Ge as doping elements. The results of lifetime measurements, NAA and FTIR analysis, solar cell processing and microscopic investigations are presented in this study. For ingots intentionally contaminated with transition metals, the combined analysis reveals that despite the overall high impurity content, good solar cell efficiencies can be reached. A strong influence of the in‐diffusion of metal impurities from the crucible as well as the back‐diffusion from the top region of the ingot ca still be observed. All metals show a strong precipitation behaviour throughout the whole ingot. The solar cell efficiency is both limited by multiple recombination active defects and shunts, induced by a high metal contamination via indirect mechanisms. Solar cells with efficiencies up to 15.2% for material contaminated with 20 ppma Fe in the melt, 15.7% for 20 ppma Cu and 15.1% for 20 ppma Cr were processed. A positive effect of Cu added to the feedstock could not be found. Ge‐rich ingots showed strong effects of increasing silicon carbide and silicon nitride formation with increasing Ge content larger than 0.5 wt.% thus reducing solar cell efficiency. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Chemical characterization of SiC and Si3N4 precipitates in multicrystalline silicon by NIR microscopy and ToF‐SIMS
Authors: Richter Susanne , Kaufmann Kai , Hagendorf Christian 
Published: December 2010

AbstractDuring the crystallization process of multicrystalline silicon precipitates may be formed, which can cause electrical and mechanical problems in the later manufacturing process of solar cells. Typical precipitates in multicrystalline silicon (mc‐Si) ingots are SiC and Si3N4, the exact chemical composition is not known until now, especially regarding dopants. After localization with near infrared (NIR) microscopy, we used Time‐of‐Flight Secondary Ion Mass Spectrometry (ToF‐SIMS) for chemical investigations. Reproducible fingerprints of the elemental composition for several SiC and Si3N4 precipitates were determined and it is shown that characteristic polyatomic fragments can be assigned to each type of precipitate. Doping elements in the different precipitates explain the origin of the electrical conductivity. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
FEM for modelling 193 nm excimer laser treatment of SiO2/Si/Si(1‐x)Gex heterostructures on SOI substrates
Authors: Conde J. C. , Martín E. , Chiussi S. , Gontad F. , González P. 
Published: December 2010

AbstractResearch on epitaxial crystaline silicon (c‐Si) and silicon‐germanium (Si1‐xGex) alloys growth and annealing for microelectronic purposes, such as Micro‐ or Nano‐Electro‐Mechanical Systems (MEMS or NEMS) and Silicon–On‐Nothing (SON) devices is continuously in progress. Laser assisted annealing techniques using commercial ArF Excimer Laser sources are based on ultra‐rapid heating and cooling cycles induced by the 193 nm pulses of 20 ns, which are absorbed in the near surface region of the heterostructures. During and after the absorption of these laser pulses, complex physical processes appear that strongly depend on sample structure and applied laser pulse energy densities. The control of the experimental parameters is therefore a key task for obtaining high quality alloys. The Finite ElementsMethod (FEM) is a powerful tool for the optimization of such treatments, because it provides the spatial and temporal temperature fields that are produced by the laser pulses. In this work, we have used a FEM commercial software, to predict the temperatures gradients induced by ArF excimer laser over a wide energy densities range, 0.1<Φ <0.4 J/cm2, on different SiO2/Si/Si(1‐x)Ge(x) thin films deposited on SOI substrate. These numerical results allow us to predict the threshold energies needed to reach the melting point (MP) of the Si and SiGe alloy without oxidation of the thin films system. Therefore, it is possible to optimize the conditions to achieve high quality epitaxy films. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The source of room temperature ferromagnetism in granular GaMnAs layers with zinc blende clusters
Authors: Lawniczak‐Jablonska K. , Libera J. , Wolska A. , Klepka M. T. , Dluzewski P. , Sadowski J. , Wasik D. , Twardowski A. , Kwiatkowski A. , Sato K. 
Published: December 2010

AbstractGranular GaAs:(Mn,Ga)As films were prepared by annealing the Ga0.985Mn0.015As/GaAs layers at 500 °C or 600 °C. It is commonly accepted that this processing should result in the formation of cubic or hexagonal MnAs clusters, respectively. We demonstrate that such a priori assumption is not justified. If in the as grown sample there are not many defects with the interstitial Mn atoms, only small cubic clusters can be formed even after annealing at 600 °C. Moreover, in a sample containing solely cubic GaMnAs clusters, the Mn ions are ferromagnetically coupled at room temperature. This fact was explained by the existence of GaMnAs solid solution in the clusters, with content of Mn close to 20% (higher than ever found in the layers) as was confirmed by experiment and theory. Extended X‐ray absorption spectroscopy studies excluded the possibility of formation of the hypothetic zinc blende MnAs clusters. Not more than one Mn atom was detected in the second shell around central Mn atom. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
New developments at the recent update of the IIW recommendations for fatigue of welded joints and components
Authors: Hobbacher Adolf F. 
Published: December 2010

AbstractThe International Institute of Welding (IIW) has published its first comprehensive recommendation on fatigue design of welded structures in 1996. The document appeared in English, French, German and Japanese. The idea was to describe the fatigue properties of welded joints and components independently from application groups with their specific preferences and interests. So, a comprehensive code was established, which covered all current methods of verification, such as component testing, nominal stress, structural stress, notch stress method as well as fracture mechanics assessment procedures. Detailed guidance for assessment of weld imperfections was also given. The outlined safety philosophy covers the different strategies and provides a detailed choice for the designer. The document had a considerable impact on code making bodies and thus it became an important source for the Eurocode. After more than one decade, a new update of the IIW recommendations has been published. The main areas of update are firstly a new consideration of high cycle fatigue in the grid of the Woehler S‐N curves, a standardized meshing for the structural hot‐spot stress concept, which allows now an economic and coarser meshing in finite element analysis, further on the extension of the effective notch stress concept to welded aluminium structures, followed by a numerical assessment of post weld treatments for improving the fatigue properties, and finally a new approach to cumulative damage in connection with multi‐axial stress. The update is a result of a worldwide collaboration of leading research institutions and it is expected that the new update will have the same impact on design and codes as the preceding document.
A longitudinal examination of positioning strategies in a liberalized developing African economy: The case of Ghana
Authors: Blankson Charles , Strutton David 
Published: December 2010

AbstractThis article examines the nature of positioning strategies pursued by companies (domestic and foreign) conducting business in a liberalized developing African economy, Ghana, over a ten‐year period. Specifically, this research deals with the aggregate behaviors of firms operating in Ghana's post‐SAP (structural adjustment program)‐induced environment. The findings reveal that the dominant positioning strategies are the brand name (branding tactics) and value for money (affordability). However, more recently, attractiveness, which implies elegance about the offering, has also emerged as a prominent positioning strategy. Evidence that supports the robustness of companies' adoption of positioning strategies within sub‐Saharan African economies is also developed. The results also suggest that firms doing business in sub‐Saharan African marketplaces characterized by an open and liberalized business climate have no choice but to become competitive in their positioning and with the aim of targeting the mass market and the lower‐middle‐class target audiences. © 2011 Wiley Periodicals, Inc.
Laparoscopic Organ‐Sparing Resection of Von Hippel‐Lindau Disease‐Associated Pancreatic Neuroendocrine Tumors
Authors: von Dücker Laura , Walz Martin K. , Voss Christian , Arnold Georg , Eng Charis , Neumann Hartmut P. H. 
Published: December 2010

AbstractBackgroundPancreatic neuroendocrine tumors (PNETs) are a characteristic feature of the tumor syndromes multiple endocrine neoplasia type 1 (MEN‐1) and von Hippel‐Lindau disease (VHL). With VHL, about 10% of the patients exhibit PNETs by age 40 years. Metastatic potential is high if the tumors have grown to >3 cm in diameter. Optimal surgical treatment is still a challenge.MethodsWe report three cases, all women, ages 22, 30, and 39 years, respectively, who had known VHL, confirmed by classic organ manifestations and germline mutations of the VHL gene. All were diagnosed, in an asymptomatic stage, with solid tumors of the pancreatic tail or tail/corpus area measuring 2.9–5.6 cm diameter. All accepted the offer of laparoscopic organ‐sparing removal of the tumors.ResultsIn all three cases, the tumor was entirely removed. In two cases, resection of the spleen was also necessary as dissection of the tumor from the major splenic vessels was impossible. Operating time was 215–365 min, and blood loss was 200–700 ml. Histolopathology revealed benign PNETs in two cases, but the third patient had regional lymph node metastases. There were no complications, and the hospital stay was 4–7 days.ConclusionsOrgan‐sparing laparoscopic surgery is an important option for treating VHL‐associated PNETs of the pancreatic tail.