bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photoconductivity and Photovoltage Generation in Novel Photocrosslinkable Nonlinear Optical Polymers
Authors: Li Lian , Jeng R. J. , Kamath M. , Kumar J. , Tripathy S. K. 
Published: March 2011

ABSTRACTPhotoconductivity in photocrosslinkable second-order nonlinear optical (NLO) polymeric materials and photovoltage generation in a poled guest-host polymer are reported. These NLO polymers have been functionalized with crosslinkable cinnamoyl groups and show relatively stable second-order optical nonlinearities at room temperature when poled and crosslinked. Without introducing any photosensitizer or charge carrier transport agents, photoconductivity was obtained in these polymer systems. Optical excitations of the NLO chromophores lead to photocarrier generation and it is conjectured that these NLO chromophores also play a role in the carrier transport. In addition to photoconductivity, photovoltage generation was observed in the dye doped polymer upon poling. This poled polymer also exhibits a polarization dependent photovoltage when illuminated by light in the absorption region of the NLO chromophore.
Studies on Ferroelectric Liquid Crystal Tolan Derivatives Designed for Nonlinear Optical Applications
Authors: Walba David M. , Rego James A. , Clark Noel A. , Shao Renfan 
Published: March 2011

ABSTRACTThe structure and properties of a series of ferroelectric liquid crystal (FLC) guests possessing a tolan unit in the core are presented. The data shows that in racemic smectic C hosts, the o-nitroalkoxytolan unit can be oriented along the polar axis in the FLC thin films, affording interesting new materials for NLO applications. The data are consistent with basic expectations regarding the structure of the FLC host-guest system. There are, however, interesting deviations from expectation suggesting that for some guests there is a large and unexplained effect of host structure on the properties of doped FLC phases.
Electronic Transport in Organic Electrophotographic Receptors
Authors: Abkowitz Martin A. , Stolka Milan 
Published: March 2011

ABSTRACTAll organic photoreceptors are now widely deployed in electrophotographic copiers and printers and represent the most important and commercially successful application of electronic organic materials. The need to optimize polymers for this application has stimulated fundamental investigations of charge generation, injection and transport processes in the disordered organic solid state. Electronic transport in a wide variety of glassy polymeric insulators has been studied by the time of flight drift mobility technique. It is typically found to proceed by a field driven chain of thermally activated tunneling events among active, compositionally identical, but energetically inequivalent sites. The inequivalece of site energies is attributed to the combined effect of disorder and site relaxation. Polymeric systems which differ widely in composition and morphology are found to exhibit a remarkably recurrent pattern of features in their transport behavior. Theoretical attempts to account for these universal features have been frustrated by their inability to explain the sublinear field dependence of the drift mobility and its variation with temperature. The drift mobility of polymers can be systematically modified by doping. Doping studies have provided the design rules which enable the fabrication of trap free polymers. The latter are an absolute requirement in electrophotography.
Functional Mimics of the Dimanganese Catalase Enzyme
Authors: Pessiki P. J. , Khangulov S. V. , Dismukes G. C. , Barynin V. V. 
Published: March 2011

ABSTRACTA series of synthetic enzyme mimics of the dimanganese catalase enzyme from bacterial cells has been prepared and the chemical mechanism of their activity has been examined. These are formulated as [LMn2X]Y2, μ2-X = CH3CO2−, ClCH2CO2−, Cl−, OH−; Y = ClO4−, BPh4−, CH3COO−, Cl−, Br−, utilizing the septadentate ligand, HL = N,N,N′,N′-tetrakis(benzimidazole)-1,3-diaminopropan-2-ol. These catalyze the disproportionation of H2O2into O2and H2O by a mechanism indistinguishable from the enzyme mechanism. Like the enzyme three electrons can be removed from Mn to form four oxidation states ranging from Mn2(II,II) to Mn2(III,IV). The electrochemical properties, the energy level spacing between electronic spin states (S =0, 1..5), ligand exchange and disproportionation kinetics can be controlled by the choice of the bridging ligand X. The mechanism involves the cyclic oxidation and reduction of the Mn2(II,II) and Mn3(III,III) species by H2O. An important component of the kinetic barrier in the rate-limiting step appears to be the free energy required for oxidation to the Mn2(III,III) species. This is determined by the Mn ligands. An ENDOR study of the manganese catalase(III,IV) fromT. thermophilushas revealed the Mn coordination environment to be predominantly carboxylate protein residues. This ligand environment greatly lowers the barrier to oxidation, enabling catalysis at rates approaching the diffusion limit.
Atomistic Simulations of Point Defect Properties in Silicon
Authors: Maroudas Dimitrios , Brown Robert A. 
Published: March 2011

AbstractA systematic analysis based on atomistic simulations is presented for the calculation of energies and equilibrium concentrations of intrinsic point defects in silicon. Calculation of Gibbs free energies is based on the quasi-harmonic approximation for the reference state and the cumulant analysis of the enthalpy distribution function from Monte Carlo simulations in the reference state. Results are presented for the temperature dependence of enthalpies, volumes, and free energies of formation and thermal equilibrium concentrations of vacancies and self-interstitials.
Damage in Composite Materials: Experiment Vs a Computational Chaotic Model
Authors: Meloni Franco , Varone Alberto , Ginesu Francesco 
Published: March 2011

AbstractWe present the results of a combined experimental and theoretical study performed using non-linear mechanics schemes to investigate the structural behaviour of a composite macroscopic material. A simple model is considered to define the order of the complexity of the real system represented by a graphite peek polymer under static and dynamic load In particular a relationship has been found between the critical points in the energy-time diagram and in the bifurcation plot.
Conventional and Unconventional Numerical Transfer-Matrix Methods
Authors: Novotny M. A. , Rikvold P. A. 
Published: March 2011

AbstractWe briefly review the numerical transfer-matrix (TM) method and its application to materials science. We report on the conventional use of TM methods to calculate phase diagrams and critical exponents of classical statistical mechanical models in d=2. Examples presented here are spin-1/2 and spin-1 models (two- and three-state lattice-gas models). Discussed are a model for oxygen -ordering in the high temperature superconductor YBa2Cu3O6+x and a model for the electrosorption of an organic substance on a metal. Some results for the spin-1/2 model in d=3 are also presented. Three unconventional applications of the TM method will also be reported. These include a study of the surface tension of spin-1/2 models, a TM formalism for metastability, and a study of a translationally invariant (non-fractal) spin-1/2 model in non-integer dimensions.
A Comparative Analysis of Brittle Fracture in Amorphous and Polycrystalline Materials
Authors: Calomino A. , Brewer D. , Kim A. , Chudnovsky A. 
Published: March 2011

AbstractThe fracture results of an amorphous epoxy resin and polycrystalline silicon nitride tested under monotonically increasing crack mouth opening displacements were compared. A conventional compact tension specimen was used for the epoxy. A new loading system and specimen was designed for the ceramic to permit stable crack growth. Tests conducted on both materials revealed multiple events of subcritical crack growth, dynamic initiation, dynamic growth, and subsequent arrest. The elastic energy release rate at initiation, G11, and arrest, G1a, was evaluated for each event. The value of G11 was found to be higher than G1a for both materials.Also common was the systematic existence of slow growth prior to dynamic initiation. Additionally, both materials showed differences between the fracture surface morphology for slow, 10-6 m/s, and fast, 103 m/s, growth. Although a constant G1a was recorded for the epoxy, large scatter and a possible trend was recorded for G1a in the ceramic.
New Tight-Binding Pair Potentials for Mineral Oxides: Application to β-Cassiterite (110), β-Tridymite (10TO) and Cristobalite (110)
Authors: Godin T. J. , Lafemina John P. 
Published: March 2011

AbstractTight-binding, total-energy (TBTE) methods have successfully predicted surface atomic geometries for a variety of semiconducting and insulating materials that are well described by a nearest-neighbor model of interatomic interactions. However, little work has been done on distant-neighbor models, which are required to study many important mineral oxides. In this paper we demonstrate one way in which the TBTE methodology can be extended to these materials. To illustrate this approach, we calculate surface atomic structures for cassiterite SnO2 (110), β-cristobalite SiO2 (110) and βtridymite SiO2 (10TO).
Discrete Models for Particle Packings
Authors: Jagota A. , Dupont E.I. 
Published: March 2011

AbstractDiscrete computational models for the viscosities, sintering rates, and transport properties of sintering particle packings are presented. The packing is represented by a set of nodes (the particle centroids) connected by links (inter-particle contacts). The models for the mechanical behavior enforce equilibrium for each particle which leads to a set of simultaneous equations for the particle motion. Electrical or thermal transport through inter-particle contacts is modelled by imposing zero net flux at a node which also leads to a set of simultaneous equations for the value of potential at each particle center. The model is used to simulate the compaction of spheres to generate a threedimensional random packing. Statistical properties of the computed packing such as packing fraction, percolation threshold, and coordination number are compared with those of an experimental random packing. Results are also presented for the effective conductivity of mixtures of particles with very different conductivities.
Molecular Dynamics Investigations into the High Permeability of Siloxane Polymers
Authors: Madkour T. , Kloczkowski A. , Mark J. E. , Roe R. J. 
Published: March 2011

AbstractThe polysiloxanes are known to have unusually high permeabilities, and have therefore been much investigated with regard to their possible use as gasseparation membranes. In particular, their permeabilities are much higher than those of n-alkanes such as polyethylene (PE), a polymer which has already been extensively investigated using molecular dynamics simulations. In order to gain insight into the molecular origin of this high permeability, such simulations have been carried out on hypothetical model systems in which the structure of the polyethylene chain [-CH2-CH2-]x is converted step-wise into that of the most important polysiloxane, poly(dimethylsiloxane) (PDMS) [-Si(CH3)2-O-]x. The structural modifications thus investigated include (i) increase in the C-C bond length, (ii) change of the system's density from the density of PE to the density of PDMS, (iii) change of bond angles of PE to the alternate bond angles of PDMS, (iv) replacement of the torsional potential of PE by the torsional potential of PDMS, (v) change of masses of CH2 units along the chain to alternate masses of Si(CH3)2 and 0 units, (vi) change of Lennard-Jones parameters of CH2 groups for the appropriate parameters of Si and 0 units. At each of the six steps the self-diffusion coefficients of polymer segments and penetrant molecules (CO2) were calculated, allowing for the assessment of the influence of the structure of the polymer on the diffusion of the penetrant.
An Application of Flory-Huggins Lattice Theory Through Molecular Simulation
Authors: Fan Cun Feng 
Published: March 2011

AbstractFundamental parameters in the Flory-Huggins theory of binary mixture, including the heat of mixing associated with pairwise interactions ( Δw12) and the coordination number, z, are calculated through molecular simulations. The pair energies (w11, w22, w12) are obtained by averaging a large number of configurations generated by a Monte Carlo approach which includes the constraints associated with excluded volume. The temperature dependence of the interaction parameter X is obtained from this study.
Atomistic Simulation of Crystal-to-Amorphous Transitions in the Intermetallic Alloys NiZr2 and Cu3Au.
Authors: Cleri Fabrizio , Rosato Vittorio , Massobrio Carlo 
Published: March 2011

AbstractThe behaviour of two different systems, NiZr2 and Cu3Au, submitted to a chemical disordering process under various thermodynamical conditions has been investigated by Molecular Dynamics simulations. The role played by volume expansion and elastic softening in the onset of the transition has been discussed in the framework of the percolation model (C.Massobrio and V.Pontikis, Phys.Rev.B 45 (1992) 2484), correlating the elastic instability with the percolation of the distorted regions which establishes in the lattice as a consequence of the external perturbations (introduction of defects, volume expansion, chemical disorder etc.).
High Energy Heavy Ions Irradiation of Thermal SiO2 Films on Si
Authors: Slaoui Abdelilah , Busch Marie-Claude , Doorhyee Eric , Toulemonde Marcel , Siffert Paul 
Published: March 2011

ABSTRACTIn this work, we present experimental observations of radiation damage in thermal SiO2 films grown on silicon, induced by energetic (> 0.2 GeV) O, Ni and Xe ions bombardement. The structural analysis of the SiO2 films, using infrared absorption spectroscopy, ellipsometry and etch rate measurements, points to atomic displacements, broken and strained Si-O bonds induced by irradiation. We have also estimated the damage production cross section and the track radii of the ions in the amorphous SiO2 films as a function of the electronic stopping power.
Role of Oxygen Precipitation Processes in Defect Formation and Evolution in Oxygen Implanted Silicon-on-Insulator Material
Authors: Park J. C. , Lee J. D. , Venables D. , Krause S. , Roitman P. 
Published: March 2011

ABSTRACTThe role of precipitation processes in defect development in high temperature implanted single and multiple implant/anneal SIMOX was studied by transmission electron microscopy. The differences in defect type, density and location were compared. The dominant defects in single implanted and annealed material are pairs of narrow stacking faults (NSFs) at a density of ∼ 106 cm−2 while stacking fault pyramids (SFPs) at a similar density dominate multiple implant/anneal material. However, SFPs are confined to the buried oxide interface and thus the density of through-thickness defects is about two orders of magnitude lower in multiple implant (<104 cm−2) than in single implant material (∼106 cm−2). SFPs are formed from a collection of four NSFs pinned to residual oxide precipitates. This transformation is energetically possible only below a critical NSF length which is dictated by the relative location of the residual precipitates. In turn, the residual precipitate location is determined by the location of as-implanted defects on which SiO2 preferentially nucleates and grows. Thus, the synergistic interaction between precipitation and defect formation and evolution processes plays a key role in determining the final defect microstructure of SIMOX.
Stability and Relaxation of Point Defects in amorphous silicon
Authors: Lutz Raymond , Lewis Laurent J. 
Published: March 2011

ABSTRACTWe have used molecular-dynamics to investigate the stability and relaxation of point defects — vacancies and interstitials — in a model of amorphous silicon, with the interactions between atoms described by the Stillinger-Weber empirical potential. The annihila-tion of point defects has been proposed as an important mechanism by which relaxation proceeds in amorphous silicon. Starting with a Wooten-Winer-Weaire model of a-Si, we “manually” create vacancies in the structure by removing a number of randomly-selected four-fold coordinated atoms. The system is then allowed to relax. Our calculations reveal unambiguously that, of a number of vacancies introduced in the model at low temperature, roughly a third are stable; these anneal out upon heating at room temperature. The vacancies seem, in most cases, to consist of a relatively large empty volume bounded by four atoms of which at least one is undercoordinated. Our study of interstitials seems to indicate that they diffuse through a “jump-and-bump” process, eventually annihilating when a large enough, properly coordinated, vacant volume is encountered.
Computer Simulation of Atomic Collision Processes in Solids
Authors: Robinson Mark T. 
Published: March 2011

ABSTRACTComputer simulation is a major tool for studying the interactions of swift ions with solids which underlie processes such as particle backscattering, ion implantation, radiation damage, and sputtering. Numerical models are classed as molecular dynamics or binary collision models, along with some intermediate types. Binary collision models are divided into those for crystalline targets and those for structureless ones. The foundations of such models are reviewed, including interatomic potentials, electron excitations, and relationships among the various types of codes. Some topics of current interest are summarized.
TiSi2 Integrity within a Doped Silicide Process Step
Authors: Crean G. M. , Cole P. D. , Stoemenos J. 
Published: March 2011

ABSTRACTDegradation of arsenic implanted titanium suicide (TiSi2) thin films as a result of thermal processing for shallow junction formation is investigated. Significant arsenic diffusion from the suicide overlayer into the silicon substrate has been detected by Rutherford Backscattering Spectrometry at drive-in temperatures > 1050°C. Cross-sectional transmission electron micrographs have shown the suicide film become increasingly non-uniform as the thermal budget increases, ultimately leading to discontinuities forming in the suicide film. This observed degradation of the titanium suicide film is also supported by sheet resistance measurements which show the film to degrade significantly above a threshold thermal budget
High-Current and Low Acceleration Voltage Arsenic Ion Implanted Polysilicon-Gate and Source-Drain Electrode Si MOS Transistor
Authors: Saito Yasuyuki , Sugimura Yoshiro , Sugihara Michiyuki 
Published: March 2011

ABSTRACTThe fabrication process of high current arsenic (As) ion implanted poly-silicon (Si) gate and source-drain (SD) electrode Si n-channel metal-oxide-semiconductor field-effect-transistor (MOSFET) was examined. Poly-Si film n-type doping was performed by using high current (typical current: 2mA) and relatively low acceleration voltage (40keV) As ion implantation technique (Lintott series 3). It was observed that high dose-As implanted poly-Si films as is show refractoriness against radical fluorine excited by microwave. Using GCA MANN4800 (m/c ID No.2, resist: OFPR) mask pattern printing technique, the high current As ion implantation technique and radical fluorine gas phase etching (Chemical dry etching: CDE) technique. the n-channel poly-Si gate (ps=∼L00ft/o) enhancement MOSFETs(ps-source-drain = =50n/o, SiO2 gate=380A) with off-leak-less were obtained on 3”Czochralski-grown 2Ωcm boron-doped p-type wafers (Osaka titanium). By the same process, a 8-bit single chip μ-processor with 26MHz full operation was performed.
Trim Simulations and Possible Studies for Edge-on Ion Irradiation of Electron Microscope Specimens
Authors: Thompson Loren J. , Allen Charles W. , Frischherz Marcus C. , Otero Mauro P. 
Published: March 2011

ABSTRACTA TRIM code [1] has been modified to simulate a special technique, first described at the Spring 92 MRS Meeting [2], for in situ transmission electron microscope (TEM) experiments involving simultaneous ion irradiation, in which the resultant phenomena are observed as in a cross-section TEM specimen without further specimen preparation. Instead of ion-irradiating the film or foil specimen normal to the major surfaces and observing in plan view (i.e., in essentially the same direction), the specimen is irradiated edge-on (i.e., parallel to the major surfaces) and is observed normal to the depth direction of the irradiation. The results of calculations utilizing the modified TRIM code are presented for cases of 200 and 500 keV Co impinging onto the edge of Si films 200 and 600 nm thick. The limitations of the technique are discussed and the feasibility of experiments involving implantation of Co into Si and the formation of COSi2, which employ this technique, are briefly discussed.
Phase and Structural Transformations in Iron and Carbon Steel Induced by Megavolt High-Current Electron Beam
Authors: Efremov A. M. , Ivanov Yu. F. , Itin V. I. , Lykov S. V. , Markov A. B. , Rotshtein V. P. , Tukhfatullin A. A. 
Published: March 2011

ABSTRACTUsing X-ray structural and transmission electron microscopy analyses, specific features of the phase and structure transformations in armco-iron and steel 45 affected by a high-current electron beam up to 1011 W/cm2 power density have been studied. It was revealed that hardening of steel with martensite structure has a quasi-periodic character that is caused by the action of a shock wave. The action of a shock wave results in formation of a thin layer on the rear side of the samples. The layer is composed of subgrains of ot-ferrite of a regular hexagonal shape with thin layers of graphite on their boundaries.
The Influence of Ion Beam Implantation on Electrical Properties of Polycrystalline MnNiCuFeO
Authors: Binbin Li , Hui Tan , Ying Han , Wei Tao , Chenglu Lin 
Published: March 2011

ABSTRACTPolycrystalline MnNiCuFeO was implanted by B+, P+ and Si+ ion beams and thermally annealed. The structure and electrical properties of the sample were measured using SEM, Microprobe (MP), Low Frequency Impedance Analyzer (LFIA) and Spreading Resistance Probe (SRP). The results show that the resistance of grain boundaries is much higher than that of grains. The spreading resistance of the implanted samples is lower by factor of 2 than that of the unimplanted ones. The ratio of the real part Rs (grain effect) to imaginary part Xs (grain boundary effect) decreases with ion beam implantation. From these results, we came to the conclusion that the behavior of the grain boundaries is important to the bulk properties of polycrystalline MnNiCuFeO.
Aluminum Ion Implantation in Silicon Carbide at High Temperature of Target
Authors: Suvorov Alexander V. , Plotkin D. A. , Makarov V. N. , Svetlov V. N. 
Published: March 2011

ABSTRACTSingle crystals and epitaxial films of SiC - 4H and 6H were implanted at an energy of 40 and 90 KeV by ions of Al at various temperatures and high dose.The implanted layers were studied before and after annealing by Raman scattering, Auger electron spectroscopy and SIMS. Results of this investigation show intensive graphitization of the implanted layer surface, the formation of great associations of defects in the implanted layer and shallow defects. It was found that recrystallization of the implanted layer pushes out a considerable part of aluminum atoms. The nature of the processes in silicon carbide during implantation and annealing is discussed.