bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitridoaluminosilicate CaAlSiN3 and its Derivatives - Theory and Experiment
Authors: Mikami Masayoshi , Watanabe Hiromu , Uheda Kyota , Kijima Naoto 
Published: April 2011

AbstractNitridoaluminosilicate MAlSiN3(M: alkaline-earth element) and its derivatives have attracted more and more attention owing to the fact that the material doped with rare-earth element has intense body color and exhibit efficient luminescence under InGaN diode irradiation. In particular, red phosphor, Eu-doped CaAlSiN3 (CASN), has good thermal property of luminescence and sufficient chemical durability for white LED use. Still, for the lineup of various kinds of white color, it is hoped to tune the red luminescence with other physical/chemical properties kept as possible. Thus the derivatives with different chemical compositions have been intensively explored so far. For the feasibility of such chemical composition change, it is necessary to understand its atomic/electronic structure of the unique crystal, which is a distorted AlN-based wurtzite superstructure (Cmc21, No.36) with Al and Si disordered on 8b site and Ca occupying 4a site. Recently, we have performed first-principles band calculation of CASN and clarified the origin of the Al/Si disorder configuration as well as the feasibility of the virtual crystal approximation of heterovalent cations (Al/Si) for the reproducibility of atomic/electronic structure of CASN.[1] As a natural extension of this study, we have investigated some CASN-derivatives to confirm/predict the crystal structure. The VCA allows us to model the superstructure with various chemical compositions quite easily. In this work, we will present two examples of solid-solution, (Ca,Sr)AlSiN3 and CaAlSiN3-Si2N2O. The agreement between experiment and theory appears quite satisfactory. It is emphasized that the crystal structure of SrAlSiN3 has been successfully predicted by first-principles calculation prior to experimental result. The collaboration of experiment and theory promises us ‘gcrystal-engineering’ to develop new nitrides/oxynitrides effectively and efficiently.
The Reduction Welding Technique Used in Pre-Columbian Times: Evidences from a Silver Ring from Incallajta, Bolivia, Studied by Microscopy, SEM-EDX and PIXE
Authors: Montes Luis Torres , Ruvalcaba Jose Luis , Mendoza Anaya Demetrio , Muñoz Collazo Maria de los Angeles , Franco Velázquez Francisca , Sandoval Pérez Francisco 
Published: April 2011

AbstractA pre-Columbian silver ring from Incallajta, Bolivia, recovered from an archaeological excavation is composed of a thin sheet of silver bent to form the ring. Two small wires in the shape of the infinity sign are joined to the surface of the ring. Four green stone beads were laid inside the four cavities formed by the wires. Energy dispersive spectroscopy (EDX) and Particle Induced X-rays Emission (PIXE) analyses of the beads proved that they were turquoise. Examination with a stereoscopic binocular microscope indicated that the two wires could have been soldered to the ring by reduction welding, because copper corrosion products were found in the interface of the welding, similar to those seen on two modern silver objects from Indonesia, decorated with granulation. Since reduction welding is a technique not reported before in pre-Columbian metallurgy, further analyses were carried out to prove that it was used here. Thus, the ring was analyzed with Scanning Electron Microscopy (SEM-EDX) and external beam PIXE, showing with certainty that the copper content in the area of the welding was higher than in any other part of the ring, with increasing copper amounts towards the center of the weld.
Trace Element Indicators of Fabrication Technology for Coral Red and Black Gloss Decoration on Greek Attic Pottery
Authors: Walton Marc , Trentelman Karen 
Published: April 2011

AbstractLaser ablation inductively coupled plasma time-of-flight mass spectrometry (LA-ICP-TOFMS) was used to study the trace element chemistry of coral red and black gloss slip decoration on Greek Attic pottery (6th century BC). The distribution of trace elements in the body fabric and glaze slips were found to be correlated suggesting the raw materials came from a single source. Furthermore, the so-called high calcium and magnesium (HCM) coral red was found to be a less refined material than black gloss, with trace element characteristics suggestive of a carbonate phase in the raw material. This carbonate component may have imparted refractory properties to the HCM coral red slip material during the three-stage oxidative-reductive-oxidative firing used to produce Attic pottery, allowing it to remain porous and re-oxidize during the final firing step, thus creating its final red color. The so-called low calcium and magnesium (LCM) coral red, on the other hand, was found to be more refined than the HCM coral red slip which suggests that two separate firings would have been needed to produce the red color of this material.
A Ceramic Plaque Representing a Part of the Moses Panel by Lorenzo Ghiberti in the East Baptistery Doors (Florence, Italy)
Authors: Vandiver Pamela B. 
Published: April 2011

AbstractA ceramic plaque was studied that depicts the figurative part of the lower half of the Moses Panel from the gilt bronze doors that Lorenzo Ghiberti and his workshop installed on the east side of the San Giovanni Baptistery in Florence, Italy. The doors were completed in 1452, and thermoluminescence dating of two areas of the ceramic relief panel gave a broad, but consistent fifteenth century date. No differences were found in the composition, microstructure or phase assemblage of the two stylistically distinct parts of the ceramic panel. Microscopy and radiography were used to reconstruct the forming methods and sequence of steps in manufacture and restoration.
Novel Self-Complimentary Tricyclic Heterocycles: Expanding the Chemistry of Self-Assembled Rosette Nanotubes
Authors: Borzsonyi Gabor , Myles Andrew J. , Johnson Ross , Cho Jae-Young , Yamazaki Takeshi , Kovalenko Andriy , Fenniri Hicham 
Published: April 2011

ABSTRACTIn an effort to increase the internal and external diameter of the RNT's, tricyclic GΛC base derivatives (XGΛC) have been synthesized and characterized. Hierchichal self-assembly results in formation of RNT's with an increased diameter, as evidenced by AFM and TEM measurements. Progress on the derivitization and characterization of the XGΛC RNT's will be presented.
A Tight-Binding Hamiltonian for Band Structure and Carrier Transport in Graphene Nanoribbons
Authors: Finkenstadt Daniel , Pennington Gary , Mehl Michael J 
Published: April 2011

ABSTRACTTo understand nanoribbons of graphene, we developed an ab initio parametrized fit to Carbon and Hydrogen chemical data, out to arbitrary neighbor interactions, including relaxations. Our computed band structure confirms the well-known three-family behavior of armchair bangaps but also predicts a similar familial behavior for conductance in nanoribbon transistors. The Boltzmann carrier transport simulations from calculated phonon spectra show, over a range of temperatures, the familial conductance behavior. Both the peak field-effect mobility and the "on" conductance increase with ribbon width, the later being proportional to the width and inversely proportional to the lattice temperature. We will also discuss phonon-limited scattering of charge carriers in graphene.
Metal-Semiconductor-Metal (MSM) Photodetectors Based on Single-walled Carbon Nanotube Film-GaAs Schottky Contacts
Authors: Johnson Jason L. , Behnam Ashkan , Choi Yongho , Noriega Leila , Ertosun Gunhan , Wu Zhuangchun , Rinzler Andrew G. , Kapur Pawan , Saraswat Krishna C. , Ural Ant 
Published: April 2011

ABSTRACTWe experimentally study the dark and photocurrent in metal-semiconductor-metal (MSM) photodetectors based on single-walled carbon nanotube film Schottky contacts on GaAs. We find that above ∼260°K, thermionic emission of electrons with a barrier height of ∼0.54 eV is the dominant dark current transport mechanism. Furthermore, MSM devices with CNT film electrodes exhibit a higher photocurrent-to-dark current ratio while maintaining a comparable responsivity relative to control devices. This work demonstrates that nanotube films can be integrated as Schottky electrodes in conventional semiconductor optoelectronic devices.
Integrated GaN/AlGaN/GaN HEMTs with Preciously Controlled Resistance on Silicon Substrate Fabricated by Ion Implantation
Authors: Nomoto Kazuki , Ohsawa Tomo , Satoh Masataka , Nakamura Tohru 
Published: April 2011

ABSTRACTMultiple ion-implanted GaN/AlGaN/GaN high electron-mobility transistors (HEMTs) and preciously controlled ion-implanted resistors integrated on silicon substrate are reported. Using ion implantation into source/drain (S/D) regions, the performances were significantly improved. On-resistance reduced from 10.3 to 3.5 &#8486;&#8226;mm. Saturation drain current and maximum transconductance increased from 390 to 650 mA/mm and from 130 to 230 mS/mm. Measured transfer curve shows that I/O gain of 4.5 can be obtained at Vdd = 10 V.
The Influence of Growth Temperature on Oxygen Concentration in GaN Buffer Layer
Authors: Dumiszewska Ewa , Strupinski Wlodek , Caban Piotr , Wesolowski Marek , Lenkiewicz Dariusz , Jakiela Rafal , Pagowska Karolina , Turos Andrzej , Zdunek Krzysztof 
Published: April 2011

ABSTRACTThe influence of growth temperature on oxygen incorporation into GaN epitaxial layers was studied. GaN layers deposited at low temperatures were characterized by much higher oxygen concentration than those deposited at high temperature typically used for epitaxial growth. GaN buffer layers (HT GaN) about 1 μm thick were deposited on GaN nucleation layers (NL) with various thicknesses. The influence of NL thickness on crystalline quality and oxygen concentration of HT GaN layers were studied using RBS and SIMS. With increasing thickness of NL the crystalline quality of GaN buffer layers deteriorates and the oxygen concentration increases. It was observed that oxygen atoms incorporated at low temperature in NL diffuse into GaN buffer layer during high temperature growth as a consequence GaN NL is the source for unintentional oxygen doping.
Imaging and Elemental Analysis of Polymer/Fullerene Nanocomposite Memory Devices
Authors: Laiho Ari , Baral Jayanta K. , Majumdar Himadri S. , Tobjörk Daniel , Ruokolainen Janne , Österbacka Ronald , Ikkala Olli 
Published: April 2011

AbstractIn this report we study the morphology and chemical composition of a nanocomposite memory device where the active device layer is sandwiched between two aluminum electrodes and consists of a nanocomposite of polystyrene (PS) and [6,6]-phenyl-C61 butyric acid methyl ester (PCBM). The morphology of the active layer is imaged both in plan-view and cross-sectional view by using transmission electron microscopy (TEM). We introduce two techniques to prepare the cross-sections from the active layer, namely, a conventional technique based on microtoming and secondly nanostructural processing with focused ion beam (FIB). Based on the morphology studies we deduce that within the used concentrations the PCBM forms spherical nanoscale clusters within the continuous PS matrix. The chemical composition of the device is determined by using X-ray photoelectron spectroscopy (XPS) and it shows that the thermal evaporation of the aluminum electrodes does not lead to observable inclusion of the aluminum into the active material layer.
The Interfacial States between Metal/Oxide and the RRAM - Part II
Authors: Pan Wei , Evans David Russell 
Published: April 2011

AbstractSwitching resistance of a metal/oxide/metal structure (Pt/PrxCa1-xMnO3/Pt) upon the stimulation of electric pulse has triggered vast research interests and activities for next generation resistive RAM application. Continued from an earlier paper [1] that studied the mechanism of switching resistance, this paper extends to the switching endurance discussion using admittance spectra. Experimental data indicated that there exist interfacial dipoles (or states) at metal/oxide interfaces. Switching resistance comes from the change of interfacial dipoles. However, those interfacial dipoles are all meta-stable indicating the problem of long term switching endurance. We have tested many metal/PCMO contact combinations and characterized those contacts with basic memory criteria: bit separation, data retention, switch endurance, switching speed, and readout limitations. Among them, TiN/PCMO showed large bit separation, excellent data retention, and fast switching speed, but failed long term switching endurance test. Furthermore, the poor switch endurance is discussed using energy-well diagram. Therefore, a material system providing bi-stable states with reasonably large free energy separations is a must for this type of RRAM application. These energy levels can come from either structure or electrochemical potential differences at the metal/oxide interfaces.
Porphyrin Assembly with Fullerenes for Photovoltaic Applications
Authors: Sagawa Takashi , Yoshikawa Osamu , Jintoku Hirokuni , Takafuji Makoto , Ihara Hirotaka , Yoshikawa Susumu 
Published: April 2011

AbstractMorphologically controllable thin-films of a zinc-containing tetraphenylporphyrin (ZnTPP) combined with an L-glutamide lipid has been fabricated and complexation of ZnTPP with fullerene was examined for organic thin-film solar cells, which gave 3 times enhancement of solar energy-to-electricity conversion efficiency through chlorobenzene-annealing in comparison with the conversion efficiency of untreated one.
Thin Film Encapsulated Transparent Organic Light Emitting Diodes
Authors: Tanase Cristina , van de Weijer Peter , Lifka Herbert , Rietjens Gerard 
Published: April 2011

AbstractHighly transparent OLEDs are very attractive for lighting and light beautification applications. While the transparent anode is based on transparent ITO, the transparent cathode is based on a 3-layer approach: (semi)transparent electron injection layer that is a low work function metal, electrically transparent conductor used in order to limit the voltage drop across the OLED area, and overcoat to tune the optical properties without influencing the electrical properties. Transparent encapsulation based on thin film technology is used in order to protect devices from ambient exposure. Using this approach large area (50 cm2) transparent organic light-emitting device having 75% transparency in the off state is demonstrated. The efficiency of the transparent OLED is comparable with that of bottom emission OLED. It is demonstrated that by tuning the thickness and optical properties of both the cathode and the encapsulation the amount of light emitted through the anode and the cathode can be varied while the total amount of light emitted by the OLED remains the same. Moreover device optimization based on optical thin film calculations has been performed such that no angular dependence of emitted light is present both on anode and cathode side.
Influence of Cyclodextrin in the Synthesis of Magnetite
Authors: Cobos Cruz L. A. , Martínez Perez C. A. , Martínez Villafañe A , Matutes Aquino J. A. , Farias Macilla J. R. , García Casillas P. E. 
Published: April 2011

ABSTRACTCyclodextrin (CD) has been studied intensively due to its ability to form inclusion complexes with a variety of guest molecules in the solid state. A few studies have paid attention to the use of CD to facilitate the synthesis of inorganic nanoparticles. In this work the synthesis of magnetite (M) is made in the presence of CD. The particle size of the inorganic material is controlled by the presence of CD, in which spherical particles of few nanometers are grown. The synthesis of Fe3O4 (M) in the presence of α-cyclodextrin (α-CD) and β-cyclodextrin (βCD) is described. The formation of an M-CD complex is studied in both cases by Fourier transform infrared spectroscopy (FT-IR) in order to elucidate the chemical bonding of the complex. The morphology and size of the particles are determined by Field Emission Scanning Electron Microscopy (FESEM) and software. X-ray diffraction (XRD) is used to confirm the formation of magnetite.
Glass-Ceramics of the Wollastonite - Tricalcium Phosphate-Silica System
Authors: López-Cuevas Jorge , Pech-Canul Martín I. , Rendón-Angeles Juan C. , Rodríguez-Galicia José L. , Gutiérrez-Chavarría Carlos A. 
Published: April 2011

ABSTRACTGlass-ceramics based on hypo-eutectic (GC1) and hyper-eutectic (GC2) compositions of the Wollastonite (W, CaSiO3) - Tricalcium Phosphate [TCP, Ca3(PO4)2] binary system, which are saturated with SiO2 during the glass melting stage, are synthesized by the petrurgic method, using cooling rates of 0.5, 1 or 2°C/h. All synthesized materials are subjected to in vitro bioactivity tests using Kokubo's Simulated Body Fluid (SBF). Primary a-Cristobalite is formed in all cases. Metastable Apatite [Ap, Ca10(PO4)6O] and W phases are additionally formed, in general, in the GC1 glass-ceramics, as well as in the GC2 material obtained at a cooling rate of 0.5°C/h. However, at faster cooling rates, TCP is formed instead of Ap phase in the latter composition. During the bioactivity tests, a hydroxyapatite [HAp, Ca10(PO4)6(OH)2]-like surface layer is formed in all materials. It is proposed that GC2 glass-ceramics cooled at a rate of 1°C/h have the potential to show good in vivo osseointegration properties.
Aem Investigation of Tetrahedrally Coordinated TI4+ in Nickel-Titanate Spinel
Authors: Anderson Ian M. , Bentley Jim , Carter C. Barry 
Published: April 2011

ABSTRACTThe stoichiometry and site distribution of metastable nickel-titanate spinel has been studied with AEM. The results of EDXS and EELS agree that the metastable spinel is nonstoichiometric and titanium-deficient relative to its hypothetical endmember composition, “Ni2TiO4”. The titanium deficiency has been determined by EELS to be Δ = 0.025 ± 0.005. Channeling-enhanced microanalysis and ELNES studies indicate that the Ti4+ and Ni2+ cations are in tetrahedral and octahedral coordination, respectively, so that the metastable spinel has the normal cation distribution: Til−Δ[Ni2(1+Δ)]O4. This result is consistent with neutron powder-diffraction studies and SiO2-solubility measurements of similar equilibrated and quenched spinel-containing specimens. Metastable nickel-titanate spinel therefore contrasts with stable stoichiometric spinels which tend to the inverse cation distribution, Me[MeTi]O4.
Imaging Single Nacreous Tablets with the Atomic Force Microscope
Authors: Giles R. , Manne S. , Zaremba C.M. , Belcher A. , Mann S. , Morse D.E. , Stucky G.D. , Hansma P.K. 
Published: April 2011

ABSTRACTAfter describing some recent developments in atomic force microscopy (AFM), a specific application to the study of shell ultrastructure is examined in detail. By embedding bleached nacreous tablets in epoxy and imaging them with the atomic force microscope (AFM) during in situ dissolution, it was possible to visualize the topography of both the top faces of the tablets and the impressions in epoxy made by the bottom faces of the tablets. This epoxy imprint reproduced tablet features down to the 10 nm scale. Using this technique it should be possible to measure correspondence between topographic features on the proximal and distal faces of tablets, which is necessary to form a three-dimensional picture of the nacreous region. In addition to these dissolution experiments, growth experiments (in modified sea water) on bleached, embedded tablets indicated that aragonite grows on a tablet as asperities oriented along the c axis, normal to the tablet surface. No change was seen on the surface of the epoxy, which confirmed that the crystals were growing on the tablet surface, not spontaneously nucleating out of solution.
Experimental and Simulated Scanning Tunneling Microscopy of the Cleaved Rb1/3WO3 (0001) Surface
Authors: Lu Weier , Rohrer Gregory S. 
Published: April 2011

ABSTRACTAtomic-scale resolution scanning tunneling microscope (STM) images of cleaved (0001) surfaces of the hexagonal tungsten bronze, Rbl/3WO3, show two distinct contrast patterns. We have interpreted these images using simulated constant current STM topographs. These simulations are constructed based on calculations of the tunnel current as a function of the lateral and vertical position above the surface. By calculating simulated images for the limiting cases of different termination layers, different tip sizes, and different electronic structures, it is possible to systematically explore the important parameters and choose a model that most closely matches the experimental observations. In this case, we conclude that two distinct termination layers have been imaged, a W-O terminated surface and a Rb-O terminated surface. Also, we have found that the O atoms on the W-O surface relax to new positions nearer the 6-fold axis of rotational symmetry. Some of the advantages and disadvantages of this model are discussed.
The Role of Hydrogen in Current-Induced Degradation of GaAs/AlGaAs Heterojunction Bipolar Transistors
Authors: Ren F. , Abernathy C. R. , Chu S. N. G. , Lothian J. R. , Pearton S. J. 
Published: April 2011

ABSTRACTCarbon-doped base GaAs/AlGaAs HBTs display current-induced decreases in dc gain which are correlated with the amount of hydrogen incorporated in the base layer during growth by Metalorganic Molecular Beam Epitaxy (MOMBE). During device operation, minority carrier injection induced debonding of hydrogen from neutral C-H complexes leads to an increase in effective base doping level and therefore to a decrease in gain. Post-growth in-situ or ex-situ annealing eliminates this effect by breaking up the C-H complexes. Properly designed HBTs are stable even for very high collector current densities (105 A · cm−2)
W/Si1-xGex Schottky Barrier: Effect of Stress and Composition
Authors: Meyer F. , Aubry V. , Warren P. , Dutartre D. 
Published: April 2011

ABSTRACTThe Schottky barrier height of W on Si1-xGex/ Si has been investigated as a function of composition and strain retained in the alloy for a given composition. The barrier height to ntype films does not vary significantly while that to p-type films follows the same trends than the band gap: it decreases with x and the strain. These results suggest that the Fermi level at the interface is pinned relative to the conduction band.
Comparing the Structure and Behavior of Point Defects in Silicon Oxynitride Gate Dielectrics formed by NH3-Nitridation and N2O-Growth/Nitridation
Authors: Yount J. T. , Lenahan P. M. , Saks N. S. , Brown G. A. 
Published: April 2011

ABSTRACTIn this work, an electron spin resonance study of NH3-nitrided, N2O-nitrided, and N2O-grown oxides yields information relating the process history, point defect structure, and electrical behavior. NH3-nitridation is responsible for the introduction of bridging nitrogen centers, high capture cross section neutral electron traps, while N2O-processed dielectrics never exhibit these defects. In addition, structural changes at the interface due to nitridation result in observable differences in the interfacial defects.
The Microstructure and Electromigration behaviour of Al-0.35%Pd Interconnects
Authors: Elliott L.J. , Paine D.C. , Rose J.H. 
Published: April 2011

ABSTRACTAl-Pd alloys have shown promise for improved IC interconnect manufacturability and reliability. However, there has been little detailed evaluation of microstructure and conductor failure reported for this material. Microstructure and electromigration behaviour of Al-0.35%Pd unpassivated interconnect was studied on films deposited at 250°C or 450°C and patterned into test structures of varying width. Samples were electrically stressed to failure at l×106A/cm2 or 2×106A/cm2. At 450°C, AlPdx precipitates form while at 250°C, palladium remains in solution and a larger grain size is obtained. Slit voids were found in 1μm and 3μm wide lines, though only in the finer lines were the failures transgranular. A very large increase in lifetime of 1μm wide lines with a decrease in current density from 2×106A/cm2 to l×106A/cm2 suggests a critical current effect due to grain boundary clusters in the these lines.