bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fabrication of Iron Oxide Nanoparticles by Pulsed-Laser Ablation
Authors: Sasaki Takeshi , Zeng Xiaoyan , Koshizaki Naoto 
Published: April 2011

AbstractNanoparticles of iron oxide were prepared by pulsed laser ablation on carbon coated mica substrates. An ArF excimer laser was used to irradiate a Fe2O3 target in atmospheres of Ar at room temperature. The effects of ambient pressure on size and morphology of nanoparticles were investigated using transmission electron microscopy. The morphology of the deposited nanoparticles was strongly dependent on the ablation pressure. The formations of nanoparticles and their aggregates were observed at pressures higher than 46.7 Pa and 267 Pa of Ar, respectively. The size of the primary nanoparticles ranged from 2 – 9 nm and their size distribution agreed with a log-normal distribution function. The aggregate size increased with ambient pressure and the primary particle size was independent of ambient pressure.
Aerosol Formation and Evolution During Laser Ablation
Authors: Camata Renato P. , Hirasawa Makoto , Okuyama Kikuo , Takeuchi Kazuo 
Published: April 2011

AbstractLow pressure differential mobility analysis and transmission electron microscopy were used to study the aerosol formed during 1064-nm pulsed Nd3+:YAG laser ablation of a solid cesium iodide (CsI) target. Measurements reveal that the aerosol is comprised of particles in three size regimes: particles with approximately log-normal size distributions and Dpg ~ 10 nm, compact spherical CsI particles with Dpg ~ 80 nm, and fractal-like agglomerates with Dpg ~ 1-3 μm.
Analysis of Impurity Diffusion in Ordered Alloys and Intermetallic Compounds of the L12 Type
Authors: Belova I.V. , Murch G.E. 
Published: April 2011

ABSTRACTIn this paper we present a new formalism for impurity diffusion in A3B alloys taking the L12 structure. We analyse two limiting cases, where impurities remain entirely on the α sublattice and where the impurities are distributed between the two sublattices but the actual mobility is largely confined to the α sublattice. Application is made to In diffusion in Ni3Al and Al diffusion (which may itself act like an impurity on the α sublattice) in Ni3Al.
Mechanisms of Al Self- and Al-Substituting Solute Diffusion in Ni3Al
Authors: Frank St. , Divinski S. , Herzig Chr. 
Published: April 2011

ABSTRACTDiffusion of the Al-substituting elements Ga, Ge, Ti and Nb has been investigated in Ni3Al single crystals by the secondary ion mass spectrometry (SIMS). A model for the minority component diffusion by anti-structure defects has been suggested for the Ll2 structure. It involves both nearest neighbor jumps of the solute atoms on the Ni sublattice as anti-structure atoms and the formation of so-called anti-structure bridges which correspond to jumps between different sublattices. The model under consideration was shown to agree with the experimental data on the Al-substituting solute diffusion (X = Ga, Ge, Ti, Nb) in Ni3Al and it allows to explain also the observed ratio of the diffusivities DNi/DX, which may be higher and/or lower than unity in dependence on the solute and temperature.
Measurements of the Diffusion of Iron and Carbon in Single Crystal NiAl using Ion Implantation and Secondary Ion Mass Spectrometry
Authors: Hanrahan R. J. , Withrow S. P. , Puga-Lambers M. 
Published: April 2011

ABSTRACTClassical diffusion measurements in intermetallic compounds are often complicated by low diffusivities or low solubilities of the elements of interest. Using secondary ion mass spectrometry for measurements over a relatively shallow spatial range may be used to solve the problem of low diffusivity. In order to simultaneously obtain measurements on important impurity elements with low solubilities we have used ion implantation to supersaturate a narrow layer near the surface. Single crystal NiAl was implanted with either 12C or both 56Fe and 12C in order to investigate the measurement of substitutional (Fe) versus interstitial (C) tracer diffusion and the cross effect of both substitutional and interstitial diffusion. When C alone was implanted negligible diffusion was observed over the range of times and temperatures investigated. When both Fe and C were implanted together significantly enhanced diffusion of the C was observed, which is apparently associated with the movement of Fe. This supports one theory of dynamic strain aging in Fe alloyed NiAl.
Diffusion in Metals and Intermetallic Compounds: The Impact of AB-INITIO Calculations
Authors: Fähnle M. , Meyer B. , Mayer J. , Oehrens J.S. , Bester G. 
Published: April 2011

ABSTRACTBy means of statistical mechanics the relations between the effective formation energies, entropies and volumes of atomic defects in ordered compounds which may be obtained experimentally and the parameters characterizing the microscopic properties of the single defects are derived, and the microscopic parameters are determined by the ab-initio electron theory. In a second step, the migration energies for possible self-diffusion paths are calculated by the transition-state theory in combination with the ab-initio electron theory. Results are reported for B2-FeAl and for Fe3Al, Ni3Sb and Fe3Si with D03 structure, and the impact of the calculations on the interpretation of experimental data is discussed.
Fermi-Level Effect, Electric Field Effect, and Diffusion Mechanisms in GaAs Based III-V Compound Semiconductors
Authors: Tan T. Y. , Chen C.-H. , Gösele U. , Scholz R. 
Published: April 2011

ABSTRACTDiffusion mechanisms and point defects in GaAs and related III-V compounds are discussed. An understanding of the As sublattice situation has been arrived at fairly recently and is presently tentative. Understanding of the Ga sublattice situation has become more acceptable in that experimental results are consistently explained by the Fermi-level effect and the As4 pressure effect. On the Ga sublattice, though controversies still exist, some are readily resolved by noting the role of the electric field produced by semiconductor electrical junctions, physical junctions, and surfaces.
Arsenic Diffusion in Intrinsic Gallium Arsenide
Authors: Bösker G. , Stolwijk N.A. , Mehrer H. , Södervall U. , Thordson J.V. , Anderson T.G. , Burchard A. 
Published: April 2011

ABSTRACTSelf-diffusion on the As sublattice in intrinsic GaAs was investigated in a direct way by As tracer diffusion measurements using the radioisotopes 73As and 76As and in an indirect way by annealing of buried nitrogen doping layers in epitaxially grown GaAs/GaAs:N heterostructures. The latter experiments were analyzed by secondary ion mass spectroscopy and interpreted within the framework of the kick-out mechanism yielding the As diffusivities mediated by As interstitials IAs. Comparison of with tracer diffusion coefficients – including data reported in the literature–points to a substantial contribution of IAs to As diffusion in intrinsic GaAs under As-rich ambient conditions.
Impurity Diffusion in SiGe Alloys: Strain and Composition Effects
Authors: Larsen Arne Nylandsted 
Published: April 2011

ABSTRACTThe advent of epitaxial-growth techniques dedicated to the growth of epitaxial layers of group-IV semiconductors and their alloys has opened up new possibilities for novel types of diffusion experiments and thus for critical tests of existing diffusion theories. It is now possible to grow test structures for diffusion consisting of well-defined narrow distributions of tracer impurities in epitaxial layers of biaxial-strained or relaxed alloys of different compositions. This enables studies of alloy effects and/or strain effects on diffusion with varying strain energy for a well-defined type of strain (tensile or compressive). A review is presented on recently published results on impurity diffusion in strained and relaxed, epitaxial SiGe alloy layers. As almost all these studies have focused on boron and antimony diffusion, these two impurities will have the leading roles in this review.
Time Dependence of Arsenic Precipitates' Size Distribution in Low Temperature GaAs
Authors: Hung C.Y. , Harris J.S. , Marshall A.F. , Kiehl R.A. 
Published: April 2011

ABSTRACTThe time dependence of the size distribution of arsenic precipitates during annealing for both large (~10nm) and small size (~4nm) regimes is investigated. A narrowing of the size distribution is observed in the small size regime. This improvement in size uniformity is in marked contrast to what is observed for larger precipitates, which coarsen with a widening distribution similar to that of classical Ostwald ripening. Inverse coarsening caused by an elastic interaction between small precipitates due to coherency strain is a possible mechanism for this interesting and potentially useful behavior.
Ultra-Fast NiSi2 Formation in p+-Si by High Current Densities
Authors: Huang J.S. , Tu K.N. 
Published: April 2011

ABSTRACTAn ultra-fast lateral formation of epitaxial NiSi2 line in heavily doped p+-Si diffused tub was created at room temperature ambient under the application of current densities of 106 A/cm2. A NiSi2 line of 140 μm long and I μm wide linking the cathode and anode contacts to p+-Si was formed within 1 second. Shorter lines were formed with lower current densities. The formation of shorter lines was again completed within 1 second and there was very little subsequent growth upon further stressing. The line length strongly depends upon applied current which tend to suggest that the line formation is limited by driving force rather than by kinetics. We propose that the ultra-fast silicide formation is a result of Ni interstitial diffusion in Si induced by electron-hole recombination heating and electromigration.
Enhanced Oxide Ion Diffusion in the Interlanthanide Perovskite LaTmO3
Authors: Deepa M. , Varadaraju U.V. 
Published: April 2011

ABSTRACTRecent studies on Perovskites type compounds revealed an oxide ion conductivity, higher than that of Fluorite structures. The most recent one is doped Lanthanum Gallate, which exhibits a maximum ionic conductivity of 0.14 S cm-1 and is a promising new ion conductor. The objective of this study is to synthesize and investigate the ionic conductivity of a similar compound, namely doped LaTmO3. Single phase compounds of the system La1-xSrxTm1-yMgyO3(X=0-0.2,y=0.1&0.2) were synthesized and the ionic conductivity measured at various temperatures. The results showed that ionic conductivity improved significantly with Sr doping. It showed highest oxygen ion diffusion and catalytic activity for Sr doped LaTmO3.
Localized Diffusional Motion of Hydrogen and Deuterium in Crystalline Pd9Si2
Authors: Karmonik C. , Huang Q. , Udovic T.J. , Rush J.J. , Andersson Y. , Flanagan T.B. 
Published: April 2011

ABSTRACTUsing quasielastic neutron scattering, we have studied the dynamics of hydrogen and deuterium in crystalline Pd9Si2. For both isotopes, a localized motion was found which takes place between two energetically different sites. For the hydrogenated sample, the spatial and temporal parameters characterizing this motion are derived. The results are in agreement with neutron powder diffraction and neutron vibrational spectroscopic measurements.
Diffusion of Carbon into RE2Fe17(RE=RARE Earth) Lattice: A High Temperature Approach
Authors: Venkatesan M. , Varadaraju U.V. , Rao K.V.S. Rama 
Published: April 2011

ABSTRACTThe interstitial carbides HoErFe15Ga2Cy (y=0,0.5,1.0,1.5,2.0) were synthesized by are melting technique and characterized by X-ray diffraction and magnetization measurements. The hexagonal Th2Ni17 type structure persisted in all compounds. Both the Curie temperature TC and unit cell volume v are found to increase monotonically with increasing carbon concentration. The unit cell volume increase of Ga substituted carbide HoErFe15Ga2C2.0 is around 6.1% compared to HoErFe17. The Curie temperature increase is mainly due to the strengthening of exchange interaction. The Ga substitution is found to not only help the formation of single phase but also enhance the uniaxial anisotropy.
Stress Effects and Non-Linearities in Dwfusional Mixing of Multilayers
Authors: Beke D.L. , Nemes P. , Erdélyi Z. , Szabó I.A. , Langer D.G. 
Published: April 2011

ABSTRACTIn classical treatments of diffusional mixing of multilayers it is usually supposed that i) the intrinsic diffiision coefficients, Di, are independent of concentration, and they are equal (the Kirkendall shift is zero) [1]; ii) the stress effects are discussed in the framework of the CahnHilliard--theory [1,2]; iii) the deviation from the continuum description can be analysed for a sinusoidal concentration distribution in the discrete Fick equations. These limitations are discussed here and numerical simulations are used to show the effects of the strong concentration dependence of Di. The role of stresses are discussed in the framework of the treatment given by Stephenson [3], which contains the effect of simultaneous stress relaxation (Kirkendall-shift) as well. For the correct description of the Kirkendall-effect a generalised analytical expression for the gradient energy term is also given. The consequences of above effects on the decay of the intensity of the first small angle Bragg peak, due to the concentration modulation, is illustrated.
Modification of Fibroin Film with A Chimera Fibroin Fragment for Improvement of Cell Adhesion
Authors: Tamada Yasushi 
Published: April 2011

AbstractSilk fibroin is a naturally occurring structural protein with good mechanical properties used in a variety of forms, such as powder, fiber, film, and gel. Although silk fibroin is potentially suitable for use in tissue engineering, it lacks cell regulation functions such as cell adhesion, growth, metabolism, and differentiation. The immobilization of biologically active molecules such as proteins and peptides has been reported as promising in controlling cell behavior. Silk fibroin's phase transition is characterized by a conformational change of protein from a random coil to a beta sheet. During phase transition, biological molecules can be stably entrapped in silk fibroin without the use of chemicals. We designed a novel immobilization using this phase transition mechanism with a chimera fibroin fragment. The chimera fibroin fragment was constructed by linking a bioactive peptide to fibroin fragments including crystal regions. In the first study, a synthetic oligonucleotide encoding Arg-Gly-Asp peptide which promotes cell adhesion, was fused to the fibroin fragment gene through inframe gene fusion, and the chimera fibroin (RGD-fibroin) gene was expressed by E.coli. This paper discusses RGD-fibroin construction, and the results of cell adhesion on fibroin films containing RGD-fibroin.
Positron Annihilation Lifetime Measurements in Collagen Biopolymer
Authors: Siles S. , Moya G. , Li X.H. , Kansy J. , Moser P. 
Published: April 2011

AbstractLifetime measurement in Positron Annihilation Spectroscopy (PAS) is applied to the study of free-volume collagen characteristics as a function of concentration. The lifetimes of positrons were obtained by a conventional fast-fast coincidence system. All lifetime data are fitted in three components by using the computer program POSITRON FIT and resolved. For each concentration, lifetime distributions were analyzed in order to obtain the different components, thus we have observed three components of which a long component τ3. This long lived component can be associated with a pick-off annihilation of ortho-positronium (o-Ps) trapped in free volumes of amorphous region. This investigation shows the potential of the positron annihilation spectroscopy technique in the study of biopolymer microstructures.
Neuronal Outgrowth Guidance on Patterned Organic Films
Authors: Matsuzawa M. M. , Krauthamer V. , Potember R.S. 
Published: April 2011

AbstractGlass substrates were modified with organic thin films to guide the outgrwoth of cultured neurons dissociated from the central nervous system. Embryonic hippocampal neurons, grown on these modified substrates, developed a morphology by following the surface geometries and they formed contacts with each other. We are now investigating technical procedures for forming physiological synapses using goldfish retinal neurons in culture.
Development of A Flexible Cell Targeting System Based on Silica Nanoparticles
Authors: Schiimstel T. , Schirra H. , Gerwann J. , Lesniak C. , Kalaghi-Nafchi A. , Sametik M. , Borchard G. , Haltner E. , Lehr C.-M. , Schmidt H. 
Published: April 2011

AbstractCommercially available and synthesized silica particles were fluorescently labeled with FITC and modified to get a wide variety of particle systems with defined size and surface charge. By a variation of reaction conditions particles with diameters of 10 and 80 nm determined with TEM and with zetapotentials between -50 to +30 mV under physiological conditions (pH: 7.4, PBS-buffer) were available.A further molecular shell consisiting of avidin was obtained by binding the molecules to negatively charged particle surfaces through electrostatic interactions. The amount of avidin coupled to the silica particles was 1.7 μg per mg particle. Starting with particles with an hydrodynamic diameter determined with PCS of 260 nm, the size increased to 500 nm, while the zeta potential was altered to -8 mV under physiological conditions.Biotinylated wheat germ agglutinin (bio-WGA) can be bonded to such particles through avidin / biotin complex formation. Up to 2.8 μg lectin per mg particles could be coupled to the particle surface. This leads to a further increase of hydrodynamic diameter to 650 nm. It could be shown by hemagglutination test, that the bonded lectin is still active. No toxic effects of the silica particles were found at 1 wt.-% particle concentration with various cell types (Caco-2, L132). The binding of lectin-particle complexes to cells was increased by a factor of 4.4 in comparison to uncoated particles.In addition it was found that WGA can directly be coupled to the particle surface. An amount of 1.8 μg Lectin per mg particle was determined. The hydrodynamic diameter increases from 260 nm to 432 rm, while a zetapotential of-28 mV was found under physiological conditions.It could be shown, that negatively charged silica nanoparticles are suitable systems to couple various biomolecules retaining their biological function.
Tailoring Polymer Surfaces for Controlled Cell Behavior
Authors: Mayes A.M. , Irvine D.J. , Griffith L.G. 
Published: April 2011

AbstractAn ideal surface for many biomaterials applications would resist nonspecific protein adsorption while at the same time providing a means for specifically signaling cells to guide survival, growth, migration, and differentiation. This work was directed towards the investigation of model systems and clinically-applicable materials which provide both of these surface requirements. Model systems were prepared by chemically grafting end-functionalized star poly(ethylene oxide) (PEO) to surfaces. The end-grafted polymers provide a means for cell-signaling through coupling of peptides to the free chain ends. Protein adsorption on star vs. linear grafted layers was compared. To further understand these results, neutron reflectivity studies were carried out in situ for solvated PEO surfaces to determine the concentration profiles of the swollen grafted layers. Surprisingly, grafted PEO layers which resist protein adsorption have low concentrations of polymer segments throughout the swollen layer. We find that dense star architectures which might be expected to impart improved protein resistance in fact allow small proteins to adsorb. For clinical materials, a novel approach to the surface modification of poly(lactide) (PLA) has been taken by surface segregating a comb copolymer containing a PLA backbone and poly(ethylene glycol) teeth. The ends of the teeth provide sites for surface tethering of peptide ligands. Comb surfaces without tethered ligands are cell adhesion resistant, indicating strong protein adsorption resistance. By then incorporating an adhesion ligand, modulation of cell morphology on comb surfaces has been demonstrated. Finally, the surface segregation of the comb to the surface of PLA was shown via cell attachment assays and XPS measurements.
Determining the Enthalpy of Formation of A Si Interstitial Using Quantitative Tem and Sims
Authors: Bharatan S. , Haddara Y. M. , Law M. E. , Jones K. S. 
Published: April 2011

ABSTRACTSome of the key parameters used in process simulators are formation energy, diffusivity and the concentration of Si self-interstitials. Unfortunately, experimental verification of these parameters is lacking. This work is therefore designed to determine the equilibrium concentration of self-interstitials at various temperatures and thus compute the formation energy for selfinterstitials in Si. Samples with thin (10 nm) buried boron layers were grown by MBE and samples with a buried type II dislocation loop layer were produced by Ge+ implantation into undoped MBE. These samples were subjected to a 40 KeV 1E14 /cm2 Si+ implant followed by anneals at temperatures between 685°C and 815°C for varying times. The loop layer was investigated to monitor the total flux of the interstitials as a function of time while the broadening of the B layer profile was analyzed by SIMS to determine the interstitial supersaturation. A combination of these two values provides an estimate of the equilibrium concentration of the Si interstitials. The results at various temperatures are then used to extract the enthalpy of formation of the Si interstitial.
Investigation of the Growth and Chemical Stability of Composite Metal Gates on Ultra-thin Gate Dielectrics
Authors: Claflin B. , Binger M. , Lucovsky G. , Yang H.-Y. 
Published: April 2011

ABSTRACTThe growth of reactively sputtered TiNx and WNx compound metal films on ultra-thin, remote plasma enhanced chemical vapor deposited SiO2 and SiO2/Si3N4 (ON) stack dielectrics is investigated from initial interface formation to bulk film by interrupted growth and on-line Auger electron spectroscopy (AES). Growth of both metals occurs uniformly without a seed layer on both dielectrics. The chemical stability of these metal/dielectric interfaces is studied by sequential on-line rapid thermal annealing treatments up to 850 °C and AES. TiNx reacts with SiO2 above 850 °C but the addition of a Si3N4 dielectric top-layer makes the TiNx/ON interface chemically stable at 850 °C. WNx/SiO2 and WNx/Si3N4 interfaces are both stable below 650 °C. MOS capacitors using TiNx or WNx metal gates and thermal SiO2 gate dielectrics exhibit excellent capacitance-voltage characteristics. The work function for TiNx lies near midgap in Si while for WNx it lies closer to the valence band.
Properties of Vacancies in Silicon Determined by Out-Diffusion of Zinc from Silicon
Authors: Giese A. , Bracht H. , Walton J. T. , Stolwijk N. A. 
Published: April 2011

ABSTRACTWe present out-diffusion of Zn in Si as a new method to study properties of Si vacancies. Out-diffusion experiments were performed on homogeneously Zn-doped Si samples at 1107°C and 1154°C. The resulting concentration-depth profiles were measured by means of spreading-resistance profiling. Based on a diffusion model in which Zn migrates simultaneously via the kick-out and the dissociative mechanism all experimental profiles were modeled by computer simulations. The calculations reveal that out-diffusion of Zn from Si occurs to a considerable extent via the dissociative mechanism. Hence, vacancy properties like the equilibrium concentration CVeq and the transport capacity CveqDV can be extracted from profile fittings. The results are compared with literature data deduced from in-diffusion experiments.