bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conductance-transient three-dimensional profiling of disordered induced gap states on metal-insulator-semiconductor structures
Authors: Castán H. , Dueñas S. , Barbolla J. , Mártil I. , González-Díaz G. 
Published: April 2011

AbstractAs it has been shown elsewhere, conductance transient measurements provide quantitative information about the disordered induced gap states (DIGS) in metal-insulator-semiconductor (MIS) structures. In this work we report for the first time the DIGS spatial and energetical distribution obtained by recording conductance transients at several temperatures (ranging from 77 to 300 K) and several frequencies (ranging from 100 Hz to 200 KHz). These measurements allow us to obtain three-dimensional defect maps of Al/SiNx:H/InP structures browsing ranges of 0.5 eV in energy and 40 Å in depth. Our results show that this technique is a very useful tool for the electrical characterization of MIS structures and reveals itself as very valuable in the III-V semiconductor-field-effect transistor scenario.
Application of a Buffer Layer for the Dielectric Measurement of Thin Polymer Films
Authors: Chiang C. K. , Sakai Wataru 
Published: April 2011

AbstractA buffered dielectric measurement method is described. We added a thin buffer polymer layer to a polymer film before depositing aluminum electrodes. This is a modification to conventional parallel plate dielectric constant measurement method. It still has well-defined geometric factor for determining the dielectric constant. We designed the buffer layer using a simple RC model. It was determined that the buffer layer should be a high dielectric constant polymer. Two high dielectric constant polymers were selected to be buffer layers. Layered samples with structures ABA and ABC were discussed, where A is the buffer layer. We show that the method not only provides a way to preserve the structure of special polymer films, but also is able to adjust its electrical characterization to a convenient level.
Development of Scanning Microwave Microscope for High-Throughput Characterization of Combinatorial Dielectric Thin Film
Authors: Okazaki Noriaki , Ahmet Parhat , Chikyow Toyohiro , Odagawa Hiroyuki , Cho Yasuo , Fukumura Tomoteru , Kawasaki Masashi , Ohtani Makoto , Koinuma Hideomi , Hasegawa Tetsuya 
Published: April 2011

AbstractA scanning microwave microscope (Sm M) for high-throughput characterization of combinatorial dielectric materials has been developed using a lumped constant resonator probe. The probe consists of a microwave oscillator module equipped with a thin conducting needle and an outer conductor ring, which detects the dielectric constant of the sample just beneath the needle as a frequency shift of the resonator. The quantitative analysis of the dielectric constant for the bulk and the thin-film samples was carried out based on the measurement of gap-length dependence of the frequency shift. The analysis method was successfully applied to the characterization of composition-spread BaxSr1-xTiO3 thin film sample. The evaluation of far-field contribution to the frequency shift was found to be crucial for the accurate determination of dielectric constant especially in the characterization of combinatorial thin films.
Computer-Controlled Fabrication of Concentric Multilayer Fresnel Zone Plate for Synchrotron Radiation Hard X-Ray
Authors: Yasumoto Masato , Tamura Shigeharu , Kamijo Nagao , Suzuki Yoshio , Awaji Mitsuhiro , Takeuchi Akihisa , Takano Hidekazu , Kohmura Yoshiki , Handa Katsumi 
Published: April 2011

AbstractA Fresnel zone plate (FZP) is a micro-focusing optical element of synchrotron radiation hard X-ray. Our developed multilayer FZP produced a sub-micron size spot at the hard X-ray energy and the focusing efficiency is about 25%. However the higher efficiency FZP is required to utilize the sub-micron probe in microscopy, diffraction and imaging applications. A kinoform FZP composed of gradient refractive index phase zones has the advantage of a high focusing efficiency compared to the conventional multilayer FZP. In order to fabricate the kinoform FZP, we developed a computer-control system. The developed computer-control system automatically operates whole combinatorial deposition processes of the kinoform FZP by inputting the optical parameters of the FZP (focal length, X-ray wavelength, number of zones, zone materials).
Artificial Intelligence In Materials Science: Application to Molecular and Particulate Simulations
Authors: Maguire John F. , Benedict Mark , Woodcock Leslie V. , LeClair Steven R. 
Published: April 2011

AbstractWe illustrate how emerging methods in artificial intelligence (AI) may be useful in materials science. Historically, these methods were developed in the area of materials process control and, more recently, in the nascent field of materials discovery. However, machine intelligence is of much broader import and our primary objective here is to illustrate how such methods may be used to circumvent some serious roadblocks in the computer simulation of a significant class of computationally hard problems in materials science. This is illustrated by a new approach to solving the dynamics of the N-body problem for large numbers of objects of essentially arbitrarily complex geometry or interaction potential. The approach, based on a particulate artificial neural net dynamics algorithm (PANNDA) is more than two orders of magnitude faster than existing methods when applied to large systems and is only marginally slower (∼10%) than the theoretical lower limiting case of hard spheres. In this method an artificial neural net is trained to predict accurately the time to next collision for binary encounters spanning the Hilbert space of relative positions, orientations and momenta (linear and angular). This approach, which can be extended to soft complex systems, enables construction of exact, albeit numerical, models for the thermodynamic, transport and non-equilibrium properties of very large ensembles of hard or soft objects of arbitrarily complex shape or interaction potential. Our results open up the possibility of immediate application to an usually wide spectrum of contemporary computationally intractable “hard” problems ranging from granular materials with asperities through inclusion of complex many-body terms in the intermolecular interaction in molecular dynamics calculations of complex fluids and polymers.
Heuristic Methods for Finding Ground-states of Ising Models
Authors: Lassalle Hugues J. , Wille Luc T. 
Published: April 2011

AbstractWe describe rhe application of simulated annealing and genetic algorithms to determine the ground-state of various classes of Lsing models. This problem is relevant to finding equilibrium contigurations(at zero Kelvin)of adsorbed monolayers, multi-component alloys, and magnetic systems. Because of the presence of metastable configurations (local minima) the detection of the ground-state (global minimum) is a non-trivial problem, especially in the case of complex interactions or frustrated systems. The speed of convergends analyzed for various model systems.
Simulation of Crystal-Melt Interfaces for a System of Binary Hard Spheres
Authors: Sibug-Aga Rachel , Laird Brian B. 
Published: April 2011

ABSTRACTCrystal-melt interfaces of binary hard spheres are investigated using molecular-dynamics simulation. For a diameter ratio α=0.414, two crystal phases coexisting with the fluid are possible, depending on the pressure. At low pressures, the liquid coexists with a pure fcc crystal of the larger particle, while at high pressures a 1:1 binary crystal of “NaCl” type is the coexisting phase. For both of these systems, we study the structural and dynamical changes as the interface is traversed from bulk crystal to bulk fluid through the calculation of density and diffusion coefficient profiles. It is observed that the total width of the interfacial region is narrower in the “NaCl”/binary fluid interface than in the corresponding lower pressure fcc/binary fluid system.
Applications of Bio-Composites in Industrial Products
Authors: Kandachar Prabhu , Brouwer Rik 
Published: April 2011

ABSTRACTAvailable as agricultural resources in many countries, natural fibers, such as flax, hemp, kenaf, exhibit mechanical properties comparable to those of synthetic fibers like glass. But they are lighter, biodegradable, and are often claimed to be less expensive. Composites with these natural fibers have the potential to be attractive alternative to synthetic fiber composites. The natural fibers, however, exhibit more scatter in their properties, are thermally less stable and are sensitive to moisture absorption. The choice of matrix to reinforce with these fibers therefore becomes critical.Currently, synthetic non-biodegradable polymers, such as polypropylene, polyester, etc., are being explored as matrix materials, for applications in sectors like automobiles and buildings. Biodegradable polymers, if made available in sufficient quantities at affordable prices, pave way for bio-composites in future. With both matrix and fibers being biodegradable, bio-composites become attractive candidates from the environment point of view.Extensive and reliable property data on natural fiber composites and/or on bio-composites, are still lacking, making product design with these materials rather tedious. Once the database is available, design & manufacture of products with natural fiber composites and biocomposites offer several opportunities and challenges.
Laminates From The Soy-Based Polyurethanes and Natural and Synthetic Fibers
Authors: Petrovič Zoran S. , Zhang Wei , Javni Ivan , Guo Andrew 
Published: April 2011

ABSTRACTTwo polyols were prepared from soybean oil, one by epoxidation route and the other via hydroformylation. The polyol obtained by epoxidation has secondary groups and has a gel time of more than one hour when reacted with crude MDI to produce polyurethanes. Hydroformylated polyol has a gel time with MDI of several minutes and is more suitable for reinforced reaction injection molding (RRIM). The first group of polyurethanes had a glass transition close to 80 °C while the hydroformylated gave about 30 degrees lower Tg and comparable strength but higher elongation. Adding glycerin as the crosslinker could increase both Tg and strength. Two series of laminates were prepared using several types of glass fabric, carbon fiber, polyester, cotton and jute fabrics r as reinforcements. Hydroformylated polyol based polyurethane composites were softer, with lower Tg, modulus and strength. Composites with organic fibers were lighter and more flexible than the glass reinforced samples. For comparison glass reinforced epoxy and polyester were prepared and tested. Organic fibers gave lower stiffness and strength than the corresponding glass or carbon fiber. Although the neat polyester and epoxy resins had somewhat higher strengths than the polyurethanes from soybean oil, mainly due to the higher crosslinking density, the composites from the soy oil-based resin displayed comparable or better properties. Glass transition and mechanical properties of the soy-based polyurethanes was varied from about 70 °C to 140 °C with added crosslinkers. Processing time of the soy-polyurethanes resins was shorter than that of the other two resins.
The role of the interfaces in the optical effects of large-sized SiCxO1-xN nanocrystallites
Authors: Plucinski K.J. , Kaddouri H. , Kityk I.V. 
Published: April 2011

ABSTRACTThe band energy structure of large-sized (10-25) nm nanocrystallites (NC) of SiCxO1-xN (0.96<x<1.06) was investigated using different band energy approaches, as well as modified Car Parinello molecular dynamics simulations of interfaces. A thin carbon sheet (of about 1 nm) appears, covering the crystallites. This sheet leads to substantial reconstruction of the near-the-interface SiCxO1-xN crystalline layers. Numerical modeling shows that these NC may be treated as quantum dot-like SiCxO1-xN reconstructed crystalline surfaces, covering the appropriate crystallites. All band energy calculation approaches (semi-empirical pseudopotential, fully augmented plane waves and norm-conserving self-consistent pseudopotential approaches) predicted the experimental spectroscopic data. In particular, it was shown that the near-the-surface carbon sheet plays a dominant role in the behavior of the reconstructed band energy structure. Independent evidence for the important role of the dot-like crystalline layers are the excitonic-like states, which are not dependent on the particular structure of the SiC, but are sensitive to the thickness of the carbon layer.
Magic Family of Discretly Sized Ultrabright Si Nanoparticles
Authors: Belomoin G. , Therrien J. , Smith A. , Rao S. , Twesten R. , Chaieb S. , Nayfeh M. H. , Wagner L. , Mitas L. 
Published: April 2011

ABSTRACTWe describe a procedure for dispersion bulk Si into a family discretely sized ultrasmall ultrabright nanoparticles. We demonstrate that electrochemically etched, hydrogen capped SinHx clusters with n larger than 20 are obtained within a family of discrete sizes. These sizes are 1.0 (Si29), 1.67 (Si123), 2.15, 2.9, and 3.7 nm diameter. We characterize the particles via direct electron imaging, excitation and emission optical spectroscopy, chromatography, and colloidal crystallization. The band gaps and emission bands are measured. The smallest four are ultrabright blue, green, yellow, and red luminescent particles. The availability of discrete sizes and distinct emission in the red, green and blue range is useful for biomedical tagging, RGB displays, and flash memories.
Optical Nonlinearity of Sputtered Co3O4-SiO2-TiO2 Thin Films
Authors: Yamamoto Hiroki , Naito Takashi , Hirao Kazuyuki 
Published: April 2011

ABSTRACTOptical non-linearity of cobalt oxide with SiO2-TiO2 additives was investigated, and the change mechanism of the refractive index (n) and extinction coefficient (k), based on the relation between band structure and optical non-linearity of the thin films, was discussed. Refractive index and extinction coefficient of Co3O4 thin films in the ground state were 3.17 and 0.42, respectively. Both n and k decreased by irradiation from a pulse laser with 650 nm of wavelength (1.91eV). These values in the excited state were 2.91 and 0.41, respectively. n2 estimated from the change of n and k was −2.8 ×10−11 m2/W. The film had a band gap corresponding to 2.06eV, indicating that it was widened by the band filling effect during the laser irradiation at 1.91eV, and this led to the decrease in absorption coefficient and refractive index.
Superconductivity of embedded lead nano particles in metallic and amorphous matrices
Authors: Chattopadhyay K. , Bhattacharya V. , Tsai A. P. 
Published: April 2011

ABSTRACTNanodispersed lead in metallic and amorphous matrices was synthesized by rapid solidification processing. The optimum microstructure was tailored to avoid percolation of the particles. With these embedded particles it is possible to study quantitatively the effect of size on the superconducting transition temperature by carrying out quantitative microstructural characterization and magnetic measurements. Our results suggest the role of the matrices in enhancement or depression of superconducting transition temperature of lead. The origin of this difference in behavior with respect to different matrices and sizes is discussed.
Synthesis of Epoxy and Block Oligomer Modified Clay Nanocomposite
Authors: Chen Kang Hung , Yang Sze Ming 
Published: April 2011

ABSTRACTAcrylic triblock (AxMyBz) and diblock (MyBz) oligomers containing methyl methacrylate (MMA, M), methacrylic acid (MAA, A) and dimethylaminoethyl methacrylate (DMAEMA, B) groups are intercalated into the layers of montmorillonite. The results indicate that the block oligomer lay flatly between the clay layers. ICP analyses of Na+ content indicate no unexchanged sodium ions are left in the intercalated clay.Nanocomposites of epoxy and clay modified with block oligomers were synthesized. Glass transition temperature (Tg) of the nanocomposite is 129.6°C (M18B2424+ modified clay) compared to 84.1°C for the physical mixture of epoxy and unmodified clay. Tg increases with decreasing amount of modified clay. When modified clay content are below 2 phr, Tg higher than 131.7 °C can be obtained. Water resistance and light transmittance of the nanocomposite is also improved over composite of epoxy and unmodified clay.
Growth of Highly Oriented ZnO Nanorods by Chemical Vapor Deposition
Authors: Liu Sai-Chang , Wu Jih-Jen 
Published: April 2011

ABSTRACTHighly-oriented ZnO nanorods were grown on the fused silica substrates by a thermal CVD technique using Zinc acetylacetonate (Zn(C5H7O2)2). The substrate was heated to 500°C and the vaporization temperature of Zn(C5H7O2)2 was keep at around 135°C. X-ray diffraction and TEM analyses reveal that the nanorods are preferentially oriented toward the c-axis direction. Photoluminescence (PL) and absorption measurements show a strong emission at around 380nm which corresponds to the near band-edge emission of the bulk ZnO. Moreover, the negligible green emission band in PL spectrum and the absence of E1(LO) mode of the ZnO crystal in Raman spectrum indicate a low concentration of oxygen vacancy in the highly-oriented ZnO nanorods.
Sol-Gel Processing of Low Dielectric Constant Nanoporous Silica Thin Films
Authors: Kim Deok-Yang , Du Henry , Bhandarkar Suhas , Johnson David W. 
Published: April 2011

ABSTRACTTetramethyl ammonium silicate (TMAS) is known as a structuring agent in zeolite synthesis. We report its first use to prepare porous silica films for low k dielectric applications in microelectronics. A solution of TMAS 18.7 wt. % was spin coated on silicon substrates with a 3000 Å thick thermal oxide. The spin coated films were subsequently heat-treated at 450°C to obtain porous silica. The use of TMAS solution without gelation led to films of only moderate porosity value of 10%. The addition of methyl lactate, a gelling agent, significantly increased film porosity and improved the pore size distribution. For example, 50% porosity and uniform pore size distribution (average pore size ∼ 40 Å) has been achieved. Dielectric constants (k) of our porous films are as low as 2.5.
Deposition of Polymer Thin Films on ZnO Nanoparticles by a Plasma Treatment
Authors: He Peng , Lian Jie , Wang L. M. , Ooij Wim J. van , Shi Donglu 
Published: April 2011

ABSTRACTUltrathin acrylic acid polymer films have been deposited on the surfaces of nanoparticles of ZnO using a plasma polymerization treatment. The average size of nanoparticles is on the order of 50 nm in irregular shapes. High-resolution transmission electron microscopy (HRTEM) experiments showed that an extremely thin film of the acrylic acid layer (15 nm) was uniformly deposited on the surfaces of the nanoparticles. In particular, the particles of all sizes exhibited equally uniform ultrathin films indicating a well-dispersed nanoparticles in the fluidized bed during the plasma treatment. The deposition mechanisms and the effects of plasma treatment parameters are discussed.
Nanostructured Hydroxyapatite Coatings for Improved Adhesion and Corrosion Resistance for Medical Implants
Authors: Zhang Zongtao , Dunn Matthew F. , Xiao T. D. , Tomsia Antoni P. , Saiz E. 
Published: April 2011

ABSTRACTHydroxyapetite (HA) coating on medical implant has been used in commercial application for several decades. The coating, commercially made by thermal spray method, functions as a intermediate layer between human tissues and the metal implant. The coating can speed up early stage healing after operation but the life span is much limited by low interfacial bond strength, which comes from the dissolution of amorphous HA in human body fluid during its service. This amorphous phase is formed in coating process under high temperature. To overcome these problems, we have developed a novel room temperature electrophoretic deposition process to fabricate nanostructured HA coating. This nanostructured HA coating significantly improved coating's bond strength up to 50-60 MPa, 2-3 times better than the thermal sprayed HA coating. The nanostructured HA coating also has corrosion resistance 50-100 times higher than the conventional HA coating. X-ray diffraction shows that all the HA coating is fully crystalline phase. It is expected that the implants with the nanostructured HA coating will have much longer service life. Other benefits derived from this process include room temperature deposition, the ability to control the coating microstructure and phases, and low cost for production.
Characterization of Self-Assembled SnO 2 Nanoparticles for Fabrication of a High Sensitivity and High Selectivity Micro-Gas Sensor
Authors: Ghan R.C. , Lvov Y. , Besser R.S. 
Published: April 2011

ABSTRACTIn order to refine further the material technology for tin-oxide based gas sensing we are exploring the use of precision nanoparticle deposition for the sensing layer. Layers of SnO2 nanoparticles were grown on Quartz Crystal Microbalance (QCM) resonators using the layer-by-layer self-assembly technique. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Electron Diffraction Pattern (EDP) analyses were performed on the self-assembled layers of SnO2 nanoparticles. The results showed that SnO2 nanoparticle films are deposited uniformly across the substrate. The size of the nanoparticles is estimated to be about 3-5 nm. Electrical characterization was done using standard current-voltage measurement technique, which revealed that SnO2 nanoparticle films exhibit ohmic behavior. Calcination experiments have also been carried out by baking the substrate (with self-assembled nanoparticles) in air at 350°C. Results show that 50%-70% of the polymer layers (which are deposited as precursor layers and also alternately in-between SnO2 nanoparticle monolayers) are eliminated during the process.
Topology and Electronic Structure of Onion-Like Carbon and Graphite/Diamond Nanocomposites
Authors: Bulusheva Lyubov G. , Okotrub Alexander V. , Kuznetsov Vladimir L. , Chuvilin Andrew L. , Butenko Yuriy V. , Heggie Malcolm I. 
Published: April 2011

ABSTRACTAnnealing of nanodiamond at moderate temperature makes it possible to produce structures being intermediate in the carbon transformation from sp3- to sp2-state (graphite/diamond nanocomposites) and onion-like carbon (OLC). Electron microscopy shows such structures involve cage shells with spacing close to graphite. X-ray emission spectroscopy has been applied to examine the electronic structure of OLC and graphite/diamond nanocomposites. The CKα-spectra of OLC produced in the temperature range of 1600-1900 K were found to be markedly different from the spectrum of particles formed at 2140 K and characterized by better ordering of graphitic shells. The latter spectrum was shown to be very similar to the CKα-spectrum of polycrystalline graphite, while the former ones exhibited a significant increase of high-energy maximum that might be caused by the holed defect structure of graphitic networks forming at the intermediate annealing temperatures. To interpret experimental spectra, the quantum-chemical semiempirical AM1 calculation of icosahedral C540 cage and that with holed defects was carried out. The lack of at least 22% atoms in an internal carbon cage was found to be essential to provide an increase of density of high-energy electronic states similar to that observed in the spectrum of OLC produced at 1900 K.
Mechanical Properties of Unsaturated Polyester / Montmorillonite Composites
Authors: Inceoglu A. Baran , Yilmazer Ulku 
Published: April 2011

ABSTRACTNanocomposites composed of unsaturated polyester matrix and organically modified clay filler were prepared. After the synthesis, XRD patterns showed that the interlayer spacing expanded from 1.25 nm to 4.5 nm. The mechanical properties of the nanocomposites were determined and it was found that adding only 3 w/w % organically modified clay improved the flexural modulus of unsaturated polyester by 35%. From DSC diagrams, it was found that Tgvalues of the nanocomposites also increased with the clay content. It is concluded that partially exfoliated / intercalated nanocomposites were formed at relatively low clay contents.