bluuebunny/crossref_metadata_2025_split huggingface dataset:
Charging and Aging Effects in Porous ULK Dielectrics
Authors: Guedj Cyril , Martinez Eugenie , Imbert Gregory 
Published: April 2011

ABSTRACTThe down-scaling of CMOS interconnects increases dielectric reliability challenges. Porous ULK materials used in advanced interconnects may suffer from charge trapping and detrimental aging during bias-thermal stress experiments. We demonstrate that a threshold between charging and aging domains may occur for an injected electrical energy of 0.1 MJ/cm3. Electron injection in the dielectric induces hydrogen radical formation first. For more damaging current stressing, in-situ Auger experiments demonstrate that the degradation is mostly due to the modification around carbon bonds.
Fatigue of Damascene Copper Lines under AC Loading
Authors: Moreau Stéphane , Maitrejean Sylvain , Passemard Gérard 
Published: April 2011

ABSTRACTFatigue in damascene copper line has been investigated by using alternating currents to generate cyclic temperatures and stresses/strains. Interconnects using beyond 65 nm node design rules and materials have been studied. We demonstrate that cyclic thermal strains lead to Cu or Cu/Co-based cap surface modification and open circuits in Cu lines during the application of an alternating electrical current. We underline that the narrower the copper lines are, the more reliable they are and the major role of the cap layer to improve the Cu lines reliability. Moreover, a statistical approach is presented in this paper in order to discuss about the thermal fatigue associated distribution model (exponential, lognormal and Weibull distributions). At present, the lognormal distribution seems to be the most appropriate one.
Low Temperature CVD of Ru from C6H8Ru(CO)3
Authors: Lazarz Teresa S , Yang Yu , Kumar Navneet , Kim Do Young , Noh Wontae , Girolami Gregory S , Abelson John R 
Published: April 2011

ABSTRACTThin ruthenium films were deposited using chemical vapor deposition from the single-source precursor tricarbonyl(1,3-cyclohexadiene)Ru(0) onto silicon, silicon dioxide and c-plane sapphire substrates in the absence of a carrier gas by thermolysis. Growth rate, resistivity, purity, crystallinity and microstructure were determined. Tricarbonyl(1,3-cyclohexadiene)Ru(0) gave metallic ruthenium films with near bulk resistivities (11-21μΩ-cm), high growth rates (up to 20 nm/min), and nearly featureless microstructures. Nucleation was rapid on all substrates tested. These results suggest that tricarbonyl(1,3-cyclohexadiene)Ru(0) is an excellent, practical precursor to use for practical applications that require depositing thin ruthenium films.
Materials Challenges in Automotive Embedded Non-Volatile Memories
Authors: Prinz Erwin Josef 
Published: April 2011

AbstractSilicon-based nonvolatile memory modules are widely used in microcontrollers, where they are embedded into a monolithic system on a chip (SoC) which also includes high speed logic transistors, cache SRAM, and peripheral circuits for communicating with the external world. The physical principle most widely exploited for nonvolatile code and data storage is charge storage in floating gates. Recently, charge storage in nitride traps and nanocrystals also has been explored.The most demanding use profiles with respect to temperatures, data retention times, and low failure rates are encountered in automotive engine control applications, where junction temperatures up to 150°C are common, for 1000's of hours. Starting with the 130nm technology node, embedded Flash technology has been integrated with copper interconnects, and at the 90nm node, low dielectric constant interlevel dielectrics are also employed to increase circuit performance. To achieve automotive reliability, the materials surrounding the silicon floating gate, nanocrystal, or nitride charge storage area must be evaluated for parasitic charge storage, write/erase stress-induced leakage current, and other parameters important for reliability. Any movement of parasitic charge, potentially over a long period of time, can reduce the sensing window of the Flash EEPROM bitcell.
Resistance Switching In Ferroelectric Materials
Authors: Li Tingkai , Hsu Sheng Teng 
Published: April 2011

AbstractA ferroelectric crystal with perovskite structure such as PbZr1−xTixO3 (PZT), SrBi2Ta2O9 (SBT), Bi3La1−xTixO12 (BLT) and non-perovskite structure such as Pb3Ge5O11 (PGO) have two polarization states, which can generate two resistance states: high resistance and low resistance states. These properties can be used for resistance random access memory applications (RRAM). When a ferroelectric capacitor is polarized an internal electric field opposite polarity to the external applied field is generated. As a result there is a large resistance change at a given bias voltage between the two polarization states of the capacitor. It is the purpose of this paper to show that the ferroelectric capacitor may be used as a current memory cell of non-destructive readout (NDRO) non-volatile Random Access Memory array. It will also be shown that each current sensing ferroelectric memory cell stores two bits of memory information and exhibits long memory retention and excellent endurance properties.
The Formation of CuIn(S,Se)2 Thin Film Solar Cell Absorbers from Electroplated Precursors
Authors: Jost Stefan , Hergert Frank , Hock Rainer , Voß Torsten , Schulze Jörg , Kirbs Andreas , Purwins Michael , Probst Volker , Palm Jörg 
Published: April 2011

AbstractIn this article structural properties as well as morphological aspects of CuIn(S,Se)2 thin film solar cell absorbers, produced by annealing of electroplated precursors, are discussed. Real-time X-ray diffraction (XRD) experiments while precursor annealing have shown, that a reduced amount of electrodeposited selenium is the key parameter to realize a chalcopyrite formation mechanism similar to the one known for sputtered stacked elemental layer (SEL) precursors. Absorber layers processed from precursors produced by simultaneous electrodeposition of copper, indium and selenium show a preferable absorber morphology with an average grain size on the micrometer scale when the electrochemically deposited amount of selenium is reduced to [Se] / [In] = 0.1. The amount of selenium, missing for the formation of a stoichiometric chalcopyrite, was deposited in a second process step prior to precursor annealing. Solar cells produced from these absorbers show light conversion efficiencies up to 10%.
Impact of Nonuniformities on Thin Cu(In,Ga)Se2 Solar Cell Performance
Authors: Kanevce Ana , Sites James R. 
Published: April 2011

AbstractSolar-cell performance degradation due to physical nonuniformities becomes more significant as the thickness of polycrystalline absorbers is reduced. “Voltage” nonuniformities such as those due to band-gap fluctuations, variations in the back-contact proximity, and areas where the absorber is completely depleted can have very significant impact on cell performance. Similarly local shunts can seriously degrade the efficiency. “Current” nonuniformities such as optical defects have generally much less impact. The analysis presented is based on Cu(In,Ga)Se2 cells, but the qualitative results should be applicable to thin-absorber devices in general. For lateral nonuniformity studies, the solar cell is simulated by a two dimensional network of parallel diodes separated by resistors. The nonuniformities are approximated by small regions of reduced photovoltage, often referred to as “weak diodes”, and by isolated shunt resistors. The weak-diode approach allows investigation of device performance as a function of the weak-diode voltage deficit, the ratio of weak-to strong-diode area, and the weak diodes' spatial distribution. Increased TCO resistance can isolate weak diodes, thus limiting the voltage loss due to nonuniformities, but increasing fill-factor losses.
Can Grain Boundaries Improve the Performance of Cu(In,Ga)Se2 Solar Cells?
Authors: Rau Uwe , Rau Uwe 
Published: April 2011

AbstractTwo-dimensional numerical device simulations investigate the influence of grain boundaries on the performance of Cu(In,Ga)Se2 solar cells focussing on the question whether or not grain boundaries can improve the efficiency of those devices. The results unveil the following statements: (i) The mere introduction of a grain boundary by adding localized defects into a device that has a high performance from the beginning is not beneficial. (ii) Polycrystalline solar cells can outperform monocrystalline ones, if the total number of defects is equal in both devices. I.e. a given number of recombination centers is better dealt with if these defects are concentrated at the grain boundary rather than homogeneously distributed in the bulk. (iii) A significant improvement of carrier collection via the grain boundaries is found if the bulk of the devices is assumed as relatively poor. In this situation, addition of defects that are not much recombination ac-tive but provide a large charge density at the grain boundaries can improve the device performance. (iv) Passivation of grain boundaries by an internal band offset in the valence band is effective only if the internal barrier amounts at least to 300 meV.
Preserving Intangible Aspects of Cultural Materials: Bonpo Ritual Crafts of Amdo, Eastern Tibet
Authors: Reedy Chandra L. 
Published: April 2011

AbstractAncient and historic products of past technologies exist in the form of material culture and archaeological finds, available for materials analysis. Technical studies and analytical work, coupled with the study of historical texts and archival documents, can help in reconstructing past technologies. But the act of making an object is, by its very nature, also an intangible part of human heritage. Production of material culture may be accompanied by specific rituals, social behaviors and relationships, music, knowledge gained from oral histories, meanings, intents, beliefs, and reasoning processes. For ancient objects, gaining access to these intangible aspects of cultural heritage may be extremely difficult, if not impossible. However, there are many societies where traditional crafts are produced within a context where the intangible aspects can still be recorded. Yet, these opportunities are disappearing at an alarming rate as development and globalization rapidly overtake more and more traditional communities. Documenting intangible data about craft processes can promote fuller understanding of the objects themselves, and aid long-term preservation of both the objects and the processes used to make them. Examples here are drawn from fieldwork conducted in 2007 at a Bonpo monastery (Serling) and nearby villages in the Amdo region of the eastern Tibetan culture area (in Sichuan Province, China). Bonpo practices, which pre-date the introduction of Buddhism into Tibet, incorporate a variety of ritual crafts that are strongly rooted in a complex web of intangible relationships, behaviors, meanings, purposes, and beliefs. This paper focuses on votive clay objects (tsha-tshas) and barley-dough offering sculptures (tormas). Processes encompassing intangible aspects that are explored include the decision to make an object, when to make it and in what form, selection of raw materials, methods for processing the raw materials, fabrication procedures, selection of who will be involved in fabrication steps, where to place the finished object, and whether it will be preserved for the long term or considered to be only a temporary object. Results are placed in the context of larger theoretical issues regarding documentation and preservation of intangible elements of cultural heritage as part of a study of materials and technological processes.
Replications of Critical Technological Processes and the Use of Replicates as Characterization Standards: An Experiment in Undergraduate Education
Authors: Vandiver Pamela B. , Raftery Heather , Ratcliffe Stephanie , Moskalik Brian T. , Andaloro Michelle , Sandler Katelyn , Retamoza Alicia 
Published: April 2011

AbstractThe technology of artifacts is analyzed and reconstructed by comparison with known craft practices, the physical and chemical constraints imposed by the raw materials, and the sequence and steps for processing those materials to achieve certain optical and mechanical properties. Understanding of craft knowledge is best pursued by practice, coupled with technical analysis. Six case studies of hands-on, undergraduate student laboratory projects are presented. The studies include testing parameters for the making of stenciled hand images similar to those at caves such as Gargas from the Upper Paleolithic period in France, the variation in processing required to produce Egyptian blue pigments and objects, controlling composition to form either green or turquoise-blue colors in Islamic lead-containing glazes, optimizing the ratio of various pigments to gum Arabic medium in tomb paintings to evaluate the application and durability, molding East Asian gokok beads in imitation of jade, and making and radiographing a mock-up of a damaged statue on the facade at the San Xavier Mission as a standard for comparison with the original. In each case, various parameters are varied to model the appearance, structure and composition of an object, and the students benefited from the experience of developing research questions and from their involvement in original research projects.
Copper Alloys Used in Barye's Hunt Scenes in the Surtout de Table of the Duc d'Orleans
Authors: Giaccai Jennifer , Lauffenburger Julie , Boulton Ann 
Published: April 2011

AbstractThe copper alloys of the statues by Antoine-Louis Barye were examined with energy-dispersive x-ray fluorescence. Barye experimented with casting techniques in his own workshop and regularly worked with the foundry of Honoré Gonon, who re-introduced lost wax casting to 19th century Paris. Two of the technically complex Barye sculptures in the surtout de table of the Duc d'Orleans were difficult to cast using the more common sand casting technique. Problems with the sand casts sent to other foundries resulted in Gonon completing the casting for problematic statues in the surtout, after Gonon had completed lost wax casting of the three hunt scenes initially sent to his foundry. Examination of the copper alloy compositions differentiates the casts from the various foundries and determines which parts of the surtout were ultimately cast by Gonon.
Self-assembled Multi-walled Carbon Nanotube Coatings
Authors: Behler Kristopher , Havel Mickael , Mattia Davide , Gogotsi Yury 
Published: April 2011

ABSTRACTMulti-walled carbon nanotube (MWCNT) grafting onto electrospun poly(acrylonitrile) (PAN) nanofibers yields a layer by layer deposition of self assembled (LBL-SA) nanotube filaments or nanowires. PAN fibers were first functionalized with carboxylic groups through a sodium hydroxide treatment. Then, poly(diallyldimethylammonium chloride) (PDDAC), a positively charged polyelectrolyte was adsorbed onto the fibers via electrostatic interaction. When placed in contact with the modified fibers, acid treated MWCNT (ac-MWCNT) self-assemble, producing a dense and continuous layer onto the polymer nanofibers, while the inherent structure and morphology of the polymer nanofibers are retained. This method is being investigated as a universal approach applicable to a variety of materials. By producing layers of nanotubes, the electrical conductivity of polymers may be improved due to formation of a continuous MWCNT monolayer on the surface as opposed to traditional incorporation of large amounts of nanotubes into the bulk of the polymer. This method can further be implemented on polymer systems that promote a positively charged surface for COOH functionalized MWCNT to attach. Polyamides offer a perfect scenario in which they do not need to be modified to allow hydrogen bonding between the polymer and the ac-MWCNTs. Electrospun polyamide 11 (PA 11) provides a network of 100 nm and greater, fibers for deposition of ac-MWCNTs. These MWCNT coated nanofibers possess high electrical conductivity, about 0.1 S/cm, resulting from a dense coverage of MWCNTs on the polymer surface.
Growth of AlGaN/GaN HEMTs on 3C-SiC/Si(111) Substrates
Authors: Cordier Yvon , Portail Marc , Chenot Sébastien , Tottereau Olivier , Zielinski Marcin , Chassagne Thierry 
Published: April 2011

ABSTRACTIn this work, we study cubic SiC/Si (111) templates as an alternative for growing GaN on silicon. We first developed the epitaxial growth of 3C-SiC films on 50mm Si(111) substrates using chemical vapor deposition. Then, AlGaN/GaN high electron mobility transistors were grown by molecular beam epitaxy on these templates. Both the structural quality and the behavior of transistors realized on these structures show the feasibility of this approach.
Roll-to-Roll Fabrication of Bulk Heterojunction Plastic Solar Cells using the Reverse Gravure Coating Technique
Authors: Tobjork Daniel , Aarnio Harri , Mäkelä Tapio , Österbacka Ronald 
Published: April 2011

AbstractThe roll-to-roll reverse gravure (RG) coating technique was used to produce thin homogeneous films (∼100 nm) for organic bulk heterojunction solar cells. The conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and the active layer regioregular poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) were successfully subsequently RG coated on an ITO covered plastic substrate in ambient air. Working solar cells were achieved after annealing and thermal evaporation of the top contact. The AM1.5 power conversion efficiency (PCE) of the RG coated organic solar cells was determined to 0.74% (at 100 mW/cm2). This was very similar to the results of a reference device that was spin coated on a glass substrate in a nitrogen glove box.
Microwave-assisted Synthesis of Perylene-3,4-dicarboximides: Highly Photostable Fluorescent Dyes
Authors: Guthrie Brian , Wang Zixing , Li Jian 
Published: April 2011

AbstractA new method for synthesis of perylene-3,4-dicarboximides (PDCIs) is reported. Modified from a literature reported synthetic method, microwave assisted heating was used to perform the reaction, which not only shortened the original reaction time, from 18 hours to 30 min, but also increased the corresponding reaction yield. A variety of PDCI derivatives were synthesized in order to correlate the influence of substituents on the reaction outcome. Moreover, the photophysical and electrochemical properties of PDCIs are characterized and reported.
The Synthesis and Magnetoelectric Properties of Tubular Polyaniline
Authors: Liu Yingli , Li Yuanxun , Zhang Huaiwu 
Published: April 2011

AbstractThe polyaniline was synthesized by in situ polymerization in the presence of ¦Â-naphthalenesulfonic acid which acts as template. The structure, morphology and magnetoeletric properties of samples were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), the standard Van Der Pauw DC four-probe method and vibrating sample magnetometer (VSM) techniques. The results indicated that polyaniline exhibited the hysteresis loops of the ferromagnetic nature and the conductance is high at 53.35 S/cm which possess both magnetic properties and electrical properties.
On the Solidification and Feeding of a Ductile Iron Casting
Authors: Ramos Gómez Eudoxio A. , Ramírez-Argáez Marco A. , González-Rivera Carlos 
Published: April 2011

ABSTRACTSolidification of a simple casting made of ductile iron is mathematically modeled in this work. The model is able to numerically simulate the cooling rate and solidification of the whole casting system composed by a cubic piece, a blind riser connected through a rectangular neck, and immersed in a green sand mold. The center of the neck acts as a valve that allows the flow of liquid metal between the casting and the riser based on the feeding technique known as Pressure Control Risering (PCR). The developed model couples the energy conservation equation and the solidification kinetics of ductile iron, through the statement of proper nucleation and growth laws. This model is satisfactorily validated by comparing the thermal histories predictions with experimental cooling curves obtained in the foundry laboratory for the same casting. According to a process analysis developed in this work, the pouring temperature is the variable that affects the most the solidification and the feeding behavior, since it increases significantly the solidification times in all regions of the casting system.
Thermochemical Method for Coating AISI 316L Stainless Steel with Ti
Authors: López-Cuevas Jorge , Camacho-Martínez José L. , Rendón-Angeles Juan C. , Pech-Canul Martín I. , Méndez-Nonell Juan 
Published: April 2011

ABSTRACTThis paper presents a thermochemical method, based on a mixture of molten alkaline halides to produce a Ti coating on AISI 316L stainless steel. The thickness of the coatings is a function of temperature and time. It is observed that the physical form of the Ti source employed affects both coating thickness and morphology. The formation of several inter-diffusion layers is detected, each having a characteristic chemical composition, morphology and location at the substrate/coating interface. It is proposed that some of the produced Ti coatings can be employed to improve osseointegration of stainless steel for potential prosthetic devices.
Titanium Coatings on AISI 316L Stainless Steel Formed by Thermal Decomposition of TiH2 in Vacuum
Authors: López-Cuevas Jorge , Rodríguez-Galicia José L. , Rendón-Angeles Juan C. , Pech-Canul Martín I. , Méndez-Nonell Juan 
Published: April 2011

ABSTRACTTi-coated AISI 316L stainless steel, for potential biomedical applications, is obtained by thermal decomposition of TiH2 under vacuum. The presence of hydrogen in the coating material facilitates the sintering process of Ti particles, with simultaneous formation of several inter-diffusion layers at the substrate/coating interface, whose thickness and chemical composition depend mainly on the treatment temperature. Coatings prepared at 1100°C exhibit formation of a wide zone at the substrate/coating interface, which is associated with the appearance of cracks, and which consists of a mixture of λ + χ + α-Fe phases. Formation of abundant microporosity is also observed in this region, which is attributed to the Kinkerdall effect.
A Cbed Procedure for Determining Local Residual Stresses from Nanoscale Areas in Cermets
Authors: Kim Gyeung Ho , Sarikaya Mehmet 
Published: April 2011

ABSTRACTA convergent beam electron diffraction method was used in a transmission electron microscope to determine residual thermal stresses from nanometer-scale areas in a ceramic-metal (cermet) composite material. It is demonstrated that the method is simple, but requires a standard sample for each of the phases in the composite. The principle of the technique is that the stresses are determined by comparing higher order Laue zone line shifts, due to lattice strain, in high-symmetry zone-axis electron diffraction patterns recorded under the same experimental conditions from the unknown phases and the standards. The application of the method to composite systems containing dissimilar phases, such as ceramic-metal composite systems, demonstrates the universality of the technique in obtaining local structural information of anisotropic strain unambiguously with a high accuracy. The procedure involved is described in detail with application to B4C-AI, a three-dimensional intertwined ceramic-metal composite.