bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface Modifaction of Ultra High Molecular Weight Polyethylene by Low Energy DC Plasma Discharge
Authors: Hargreaves M. S. , Hussey D. S. , Leuchtner R. E. 
Published: April 2011

AbstractSurface effects produced by plasma processing Ultra High Molecular Weight polyethylene (UHMW) were examined. The goal was to enhance adhesion of UHMW to a variety of polar polymers. This research focussed on enhancing adhesion to polyurethane. UHMW samples were immersed in a DC discharge and subjected to various processing conditions. The background gases experimented with were oxygen, nitrogen, and argon, and the pressure was varied between 6-67 Pa. The processing time, discharge current and discharge potential were also varied. A polar polymer (polyurethane) was subsequently applied to the processed UHMW samples and the tensile strength of the bonds was measured. Standard dogbone specimens were fabricated, and the polymer interfaces placed in the middle of the gage section and oriented normal to the tensile axis. The specimens were tested to failure in displacement control at an approximate strain rate of 0.2% per sec. In general, significant enhancement in yield strength was observed over unprocessed samples, where essentially no bonding occurred. Samples subjected to plasma processing in oxygen showed the strongest adhesion, while those in argon were almost as good, followed by nitrogen.The contact angle of water on the processed UHMW samples ranged from about 45° to less than 2°, while unprocessed samples had a contact angle of about 70°. These data correlated with the yield tests. XPS was used to examine the composition of the UHMW surfaces before and after plasma processing with oxygen. It is believed that the plasma etched off surface layers, creating unsaturated carbon bonds that can chemically react with polar polymer groups. Precast, processed UItMW surfaces were found to be reactive for periods of up to one week. Optimum conditions of plasma processing were identified, and will be discussed in light of the chemistry occurring at the interface.
Comparison of Proliferation and Growth of Human Keratinocytes on Plasma CO-Polymers of Acrylic acid/1,7- Octadiene and Self Assembled Monolayers
Authors: Haddow D. B. , France R. M. , Short R. D. , Macneil S. , Dawson R. A. 
Published: April 2011

AbstractHuman keratinocytes have been cultured on plasma co-polymers (PCPs), self assembled monolayers (SAMs), tissue culture poly(styrene) (TCPS) and collagen I. The degree of keratinocyte attachment was measured over 24 hours and cell proliferation and growth monitored over 7 days using optical microscopy and DNA concentrations. Cell attachment and proliferation and growth on the PCP surfaces were compared with 2 self assembled monolayer (SAM) systems. PCP surfaces containing carboxylic acid functionalities promoted keratinocyte attachment, with optimum attachment levels seen on surfaces containing less than 5% acid groups. The level of attachment on these surfaces was comparable to that seen on collagen I, a preferred substratum for the culturing of keratinocytes. After several days in culture the cells were well attached and proliferative. Keratinocytes attached well to acidterminated SAMs but attached poorly to methyl-terminated SAMs.
Boron Containing Polyimides for Aerospace Radiation Shielding
Authors: Ko Stephen C. , Pugh Christopher S. , Kiefer Richard L. , Orwoll Robert A. , VA Williamsburg , Thibeault Sheila A. , King Glen C. 
Published: April 2011

AbstractIn interplanetary travel and high altitude flight, humans will be exposed to high energy charged particles from solar flares and galactic cosmic rays. These particles lose energy in a material by Coulomb interactions and nuclear collisions. In nuclear collisions, large amounts of energy are transferred and secondary particles are formed from both the projectile and the struck nucleus. A significant portion of these particles are neutrons which can only lose energy by collisions or reactions with a nucleus. Hydrogen-containing materials, such as polymers, are most effective in reducing the neutron energy. When reduced to very low energies, neutrons have a high probability of reacting with a nucleus. Such reactions are dangerous in the human body, and can cause electronic equipment failure. Low energy neutrons react particularly well with a stable isotope of boron, 10B. To test structural materials which contain both hydrogen to reduce the energy of neutrons and boron to absorb neutrons of reduced energy, samples of two polyimides were made which contained varying amounts of either amorphous boron powder or boron carbide whiskers. The polymers used were a thermoset, PETI-5 from Imitec, and a thermoplastic, K3B from Fiberite. Both materials were made in pure form and with up to 20% by weight of the boron additives. The addition of boron in either form did not change the thermal properties of these materials significantly. However, the compressive yield strength and the tensile strength were both affected by the addition of the boron materials. A neutron absorption test using a PuBe thermal neutron source showed that a 0.5 cm thick sample of K3B containing 15% amorphous boron powder absorbed over 90% of the incident neutrons.
Multilayer Coatings for Focusing Hard X-ray Telescopes
Authors: Ivan A. , Bruni R. , Byun K. , Everett J. , Gorenstein P. , Romaine S. 
Published: April 2011

AbstractSeveral multilayer test coatings for hard X-ray telescopes were fabricated using DC magnetron sputtering. The process parameters were selected from a series of trials of single layer depositions. The samples were characterized using X-ray specular reflectivity scans, AFM, and cross-sectional TEM. Additional measurements (stylus profilometry, RBS, and Auger analysis) were used in the optimization of the deposition rate and of the thin film properties (density, composition, surface/interface microroughness). The X-ray reflectivity scans showed that the combinations of reflector and spacer materials tested so far (W/Si and W/C) are suited for graded d-spacing multilayer coatings that present a constant reflectivity bandpass up to 70 keV.
Intrinsic Misfit Dislocations on 120° Interface in TiAl
Authors: Paidar V. , Zghal S. , Couret A. 
Published: April 2011

ABSTRACTThe misfit between 120° rotational variants of the lamellar structure in γ-phase TiAl with the ordered L10 lattice is analysed. It is shown that such a misfit on the (111) interface plane, which has a shear character, can be accommodated by one, two or three arrays of interface intrinsic dislocations. One example of interface dislocation structure observed by transmission electron microscopy is presented.
Deformation of Bi-PST Crystals of TiAl Produced by Diffusion Bonding
Authors: Imamura D. , Hoshikawa H. , Kishida K. , Inui H. , Yamaguchi M. 
Published: April 2011

ABSTRACTDiffusion bonded bi-PST crystals of three different series were prepared and they were deformed in tension at room temperature. Yield stress and elongation exhibited by bi-PST crystals consisting of component crystals with the lamellar microstructure aligned along the tensile axis do not significantly differ from those of component crystals. Plastic strain incompatibility at the interface exerts a strong influence on the deformation behavior of bi-PST crystals when the incompatibility activates additional deformation modes which are much harder than deformation modes operative in each component crystal.
Hexagonal Stacking at Order Interfaces Between Lamellae in TiAl
Authors: Inkson B. J. 
Published: April 2011

ABSTRACTStacking faults at order interfaces in TiAl have been examined by HREM. In addition to very extensive OCISF formation, C-core dislocation complexes spread over two parallel { 111 } planes have been observed at order interfaces lying predominantly parallel to the original (0002)α, planes. Such C-cores, corresponding to 1/2<211] and 1/2<112] interfacial dislocations, have been observed with localised regions of both extrinsic and hexagonal stacking.
Mechanical Disordering of Cubic Intermetallics By Unconventional Methods of Cold-Work and Their Reordering Upon Annealing
Authors: Varin R. A. , Bystrzycki J. , Calka A. 
Published: April 2011

ABSTRACTTwo unconventional methods of cold-work: (a) controlled mechanical (ball) milling (under shear conditions), and (b) shock-wave (explosive) loading at ˜5 GPa shock pressure were applied to two cubic intermetallics: (a) Mn-stabilized cubic (L12) titanium trialuminide (AI3Ti(Mn)) and (b) B2 iron aluminide (FeAl). The long-range order (LRO) parameter S of both intermetallics decreases and their lattice constants increase with increasing milling time providing strong evidence that the mechanical milling disorder is due to antisite-atom pairs. A nanocrystalline structure is being formed in both intermetallics upon milling. A shock-wave loading gives rise to only a partial disorder of both A13Ti(Mn) and FeAl but their lattice constants are not affected (no point defects formation). Annealing at 600°C results in the restoration of LRO and lattice constants as well as microstructural evolution in Fe-45A1.
The Role of Computational Modeling Processes in the Development and Understanding of NiAl-Based Ordered Intermetallic Alloys
Authors: Bozzolo Guillermo , Noebe Ronald D , Honecy Frank S , Good Brian S 
Published: April 2011

ABSTRACTA detailed understanding of the structure of ordered intermetallic systems is difficult at best, causing a serious disconnect in the typical process-structure-properties approach to alloy development. Basic information, like the site substitution schemes of various alloying elements, partitioning behavior in multiphase alloys, and the dependence of these phenomena with concentration and higher order alloying additions is necessary to predict and understand the effect of various alloying schemes on the physical and mechanical properties of a material. It is only recently that theoretical methods can begin to provide useful insight in these areas, as most current techniques suffer from strong limitations including the type and number of elements that can be considered and the crystallographic structure of the resulting phases. The Bozzolo-Ferrante-Smith (BFS) method for alloys was designed to overcome these limitations, with the intent of providing a useful tool for the theoretical prediction of fundamental properties and the structure of multi-component systems. The role or potential contributions of theoretical procedures like the BFS method to the alloy design process are discussed with a specific emphasis on work that has been conducted on NiAl-based alloys. After a brief description of the method and its range of applications, we will concentrate on the usefulness of BFS as an alloy design tool. The theoretical determination of site substitution schemes for individual as well as collective alloying additions to NiAl, the resulting behavior with respect to solubility limits and second phase formation, and the concentration dependence of the lattice parameter will be demonstrated.
Selective Growth Of Decagonal Ai-Co Thin Films By Reactive Diffusion: Kinetic And Thermodynamic Aspects
Authors: Emeric E. , Bergman C. , Clugnet G. , Gas P. 
Published: April 2011

AbstractWe report on the formation by reactive diffusion of a pure decagonal quasicrystalline film in Al/Co bilayer and multilayer structures of overall composition Al13CO4. We show that this method is highly selective since several stable phases which exist around this composition are never observed. The quasicrystal is not the first reaction product but is obtained as a second reaction step by a peritectoid reaction between Al9Co2 and the remaining cobalt. DSC analysis allows the determination of both the enthalpy of formation of the decagonal quasicrystal (ΔHf = -31500 ± 2000 J/g-atom) and its activation energy of growth (2.6 ± 0.5 eV).
Plastic Deformation Of AI-Cu-Fe Icosahedral Quasicrystals
Authors: Giacometti E. , Baluc N. , Bonneville J. 
Published: April 2011

AbstractPoly-quasicrystalline specimens of the Al-Cu-Fe system have been pre-strained and further deformed at various temperatures, above and below the brittle-to-ductile transition temperature, under constant strain-rate conditions. The experiments have been specially designed to examine the respective contributions of the thermally reversible and structural dependent parts to the total flow stress. We show that the so-called internal stress, which results from the deformation builtin microstructure, has a rather low value, if any. In addition, the flow stress is found to be fully temperature reversible, if one takes into account previous plastic strains. We suggest that these results can be explained by a weakening of the friction stress, due to the formation of soft slip bands.
Observations Of Pure Climb Dislocation Movements IN Al-Pd-Mn
Authors: Caillard D. , Vanderschaeve G. , Bresson L. , Gratias D. 
Published: April 2011

AbstractTEM observations of dislocations and faults in an as-grown Al-Pd-Mn single crystal show that dislocation movements have occurred by pure climb in mirror planes. A comparison with creep properties of h.c.p. metals along their c-axis indicates that pure climb is a realistic deformation mode when glide is inhibited at high temperature.
Growth and Structure of Metallic Barrier Layers and Interconnect Films II: Atomistic Simulations of Film Deposition onto Inclined Surfaces
Authors: Torre J. Dalla , Gilmer G. H. , Windt D. L. , Baumann F. H. , Kalyanaraman R. , Huang Hanchen , Rubia T. Díaz de la , Rouhani M. Djafari 
Published: April 2011

ABSTRACTWe present three dimensional lattice Monte Carlo simulations of sputter deposition onto inclined surfaces. For this purpose, we use a model of an fcc material and we vary the substrate inclination, the texture, and the atomic mobility. In this way we can examine different conditions and mechanisms involved in depositing barrier layer and interconnect films. We obtain results on the density and the roughness of the films. We find that the film texture has dramatic effects on the film density and smoothness. Surprisingly, we find that the surface diffusion coefficients may not be critical parameters; changes in the coefficients by several orders of magnitude may cause only a small change in the film morphology when depositing onto non-wetting substrates.
PVD Growth of FCC Metal Films On Single Crystal Si And Ge Substrates
Authors: Westmacott K. H. , Hinderberger S. , Radetic T. , Dahmen U. 
Published: April 2011

ABSTRACTEpitaxial films of the fcc metals Al, Au, Ag and Ni were grown by physical vapor deposition on Si and Ge (111), (110) and (100) substrates at different deposition temperatures. The epitaxial relationships and morphological features of these films were characterized by transmission electron microscopy and diffraction in plan view and cross section. Ag formed single crystal films on all substrates at all temperatures. Au and Al could be grown as bicrystals, and under some conditions, Al and Ni grew as tricrystal films. The morphological effects of diffusion at the metal/substrate interface are ascribed to diffusion induced grain boundary migration.
Low Temperature Formation of Ultra-Thin SiO2 Layers Using Direct Oxidation Method in a Catalytic Chemical Vapor Deposition System
Authors: Izumi A. , Sohara S. , Kudo M. , Matsumura H. 
Published: April 2011

ABSTRACTThis paper reports a procedure for low-temperature formation of silicon dioxide (SiO2) using a catalytic chemical vapor deposition (Cat-CVD) system. The surface of Si(100) is oxidized at temperatures as low as 200°C and a few nm SiO2 films are formed. Electrical and structural properties of the layers are investigated. It is found that breakdown electric field, leakage current and the density of intermediate oxidation states is comparable with thermally oxidized sample.
Ultrathin Gate Oxides with Shallow Nitrogen Implants as Effective Barriers to Boron Diffusion
Authors: Ono Yoshi , Ma Yanjun , Hsu Sheng-Teng 
Published: April 2011

ABSTRACTPlasma immersion ion implantation (PIII) has been employed to controllably place nitrogen ions from an inductively coupled plasma into a thin furnace grown gate oxide 2.0nm thick with implant voltages from 25 to 500V. Control of the implant energy enables shallow implantation confining the nitrogen mainly within the oxide. Rapid thermal annealing is essential in repairing any damage to the implanted silicon dioxide and silicon while consolidating the bonding of nitrogen into the oxide film prior to gate polysilicon deposition. High frequency capacitance-voltage measurements of capacitors made with BF2+ implanted gates throughout a series of furnace anneals demonstrates the efficiency for blocking boron compared to non-nitrided oxides of similar thickness. Tddb measurements verify excellent reliability compared to a non-implanted oxide for both stress polarities.
Role of Silver Doping in the Improvement of Electrical Properties of (Ba,Sr)TiO3 Thin Films
Authors: Srivastava Anuranjan , Kumar D. , Singh Rajiv K. , Venkataraman Harish , Eisenstadt William R. 
Published: April 2011

ABSTRACTIn this paper we report the fabrication and characterization of Ag/(Ba,Sr)TiO3 /LaNiO3/LaAlO3 capacitors. All the films, including the top (silver) and bottom (LaNiO3) electrodes, were deposited using a pulsed laser deposition technique. The electrical and dielectric properties of (Ba,Sr)TiO3 capacitors were found to improve significantly by means of silver doping. For example, the leakage current density of a Ag/Ag-doped-(Ba,Sr)TiO3 /LaNiO3/ capacitor was about an order of magnitude lower and dielectric constant was ∼40 % higher than that of a Ag/(Ba,Sr)TiO3 /LaNiO3/capacitor over a range of biases. The improvement in the electrical properties of (Ba,Sr)TiO3 films is believed to be caused by a double role of silver. The first one is associated with the reduced oxygen vacancies due to improved oxygenation of BST films in presence of silver and the second one is associated unpinning effect of domain walls again in presence of silver.
Quantitative Measurement of Reduction of Phosphorus Diffusion by Substitutional Carbon Incorporation
Authors: Carroll M. S. , Sturm J. C. , Chang C-L. 
Published: April 2011

ABSTRACTComplete suppression of transient enhanced boron diffusion (TED) and oxidation enhanced boron diffusion (OED) in silicon have been achieved using substitutional carbon to reduce the excess point defect concentration in the dopant region [1]. Recent efforts have focused on removing the carbon from the active regions of the device [2,3] to avoid device degradation due to electrically active carbon defects [4] and exploring remote carbon's effect on boron TED and OED, while using the boron diffusion to probe point defect concentrations.In this paper we measure quantitatively the effect of remotely located carbon on phosphorus and boron diffusion above a buried SiGeC layer at 850°C in oxygen or nitrogen ambients. Remote carbon, located 1250 A below the phosphorus edge, is found to reduce the phosphorus diffusion enhancement factor due to OED from 8 to 2. The effect of the remotely located SiGeC buried layer on the excess interstitial concentration profile, which is responsible for the enhanced dopant diffusion, is probed by measuring boron and phosphorus diffusivites of in-situ doped boron and phosphorus layers above a buried SiGe(C) layer after oxidation or nitrogen anneals at 850°C. The enhanced boron diffusivity during oxidation is found to have a near linear dependence on depth ranging from 5–1.25. Finally, using x-ray diffraction and photoluminescence measurements of as-grown, buried, strained SiGe(C) structures and annealed SiGe(C) structures in oxygen or nitrogen ambient at 850°C the number of substitutional carbon atoms effectively consumed by oxidation is unambiguously correlated to the absolute number of injected interstitials using published values for the interstitial injection rate during oxidation [5].
Ultra-Low Energy Boron Implants in Crystalline Silicon: Atomic Transport Properties and Electrical Activation
Authors: Napolitani E. , Carnera A. , Privitera V. , Magna A. La , Schroer E. , Priolo F. , Mannino G. , Moffatt S. 
Published: April 2011

ABSTRACTWe investigated the atomic transport properties and electrical activation of boron in crystalline epitaxial silicon after ultra-low energy ion implantation (0.25–1 keV) and rapid thermal annealing (750–1100 °C). A wide range of implant doses was investigated (3×1012-1×105/cm2). A fast Transient Enhanced Diffusion (TED) pulse is observed involving the tail of the implanted Boron, the profile displacement being dependent on the implant dose. The excess of interstitials able to promote enhanced diffusion of implanted boron occurs, provided the implant dose is high enough to generate a significant total number of point defects. The Boron diffusion following the fast initial TED pulse can be described by the equilibrium diffusion equations.The electrical activation of ultra-shallow implants is hard to achieve, due to the high concentration of dopant and point defects confined in a very shallow layer that significantly contributes to the formation of clusters and complex defects. Provided a correct combination of annealing temperatures and times for these ultra-shallow implants is chosen, however, a sheet resistance 500 Δ/square with a junction depth below 0.1μm can be obtained, which has a noteworthy technological relevance for the future generations of semiconductor devices.
Comparison of Ultra-low-energy Ion Implantation of Boron and BF2
Authors: Park Jihwan , Hwang Hyunsang 
Published: April 2011

ABSTRACTWe have compared the electrical characteristics and the depth profile of an ultrashallow junctions formed by boron implantation at 0.5 keV and BF2 implantation at 2.2 keV. The modeling of the boron profile was performed using the Monte Carlo method for an as-implanted profile and the computationally efficient method for transient-enhanced diffusion. A junction depth of BF2 is shallower than that of boron after annealing. HF dipping prior to rapid thermal annealing causes a significant loss of dopant and high sheet resistance. Considering the 0.1 νn metal-oxide-semiconductor field-effect-transistor (MOSFET) application, the optimizations of implantation and annealing conditions are necessary to satisfy the requirement ofjunction depth and sheet resistance.
Experimental Study of Self-Diffusion in Silicon Using Isotopically Enriched Structures
Authors: Ural Ant , Griffin Peter B. , Plummer James D. 
Published: April 2011

ABSTRACTSelf-diffusion in silicon has been studied using epitaxially grown isotopically enriched structures under nonequilibrium concentrations of intrinsic point defects created by thermal oxidation and nitridation. Comparison of identical anneals for self, antimony, and phosphorus diffusion in silicon enables us to determine bounds on the fractional contributions of microscopic mechanisms for Si self-diffusion in the temperature range 800–1100°C. We obtain direct experimental evidence for a dual vacancy-interstitial mechanism of self-diffusion in silicon and show that the fractional contribution of each mechanism has a weak dependence on temperature.
Modeling The Evolution of Ellipsometric Data During The Thermally Induced Pt-Silicide Formation: Activation Energies and Prefactors
Authors: Ley L. , Stark T. , Hundhausen M. , Gruenleitner H. 
Published: April 2011

ABSTRACTThe formation of Pt silicide (PtSi) by the thermally activated reaction of a 23 nm Pt layer on Si was monitored in situ by ellipsometry. Characteristic changes in the ellipsometric angles as a function of temperature signal the approach of two reaction fronts to the surface: one belonging to the Pt/Pt2Si and the other to the Pt2Si/PtSi interface. An analysis of the evolution of the ellipsometric angles as a function of temperature for different heating rates allows the accurate determination of the average activation energies of the two reactions. From a modeling of the optical data in terms of a specific reaction model further kinetic parameters such as the reaction rate constants and the actual distribution of activation energies have been deduced.