bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic Coercivity and Thermal Decay of Magnetic Media
Authors: Rubin Kurt , Goldberg Jason , Rosen Hal , Marinero Ernesto , Doemer Mary , Schabes Manfred 
Published: April 2011

AbstractThermally induced decay of longitudinally recorded magnetic transitions is measured on a spin-stand. The decay rate increases with increased linear density and decreases with increased media coercivity. A new spin-stand experimental technique has been developed which allows measurements of the time dependence of the media coercivity as a function of write times spanning short times characteristic of write times in drives to long times associated with VSM measurements. The ratio of long to short write time coercivity was larger for media which are thermally unstable.
Computer Simulations of Thermal Switching in Small-Grain Ferromagnets
Authors: Novotny M. A. , Brown G. , Rikvold P. A. 
Published: April 2011

AbstractWe present Monte Carlo and Langevin micromagnetic calculations to investigate thermal switching of single-domain ferromagnetic particles. For the Monte Carlo study we place particular emphasis on the probability that the magnetization does not switch by time t, Pnot(t). We find that Pnot(t) has different behaviors in different regimes of applied field, temperature, and system size, and we explain this in terms of different reversal mechanisms that dominate in the different regimes. In the micromagnetic study of an array of Ni pillars, we show that the reversal mode is an ‘outside-in’ mode starting at the perimeter of the array of pillars.
Application of Cathodic Arc Deposited Amorphous Hard Carbon Films to the Head/Disk Tribology
Authors: Anders Simone , Singh Bhatia C. , Fong Walton , Yu Lo Roger , Bogy David B. 
Published: April 2011

AbstractAmorphous hard carbon films deposited by filtered cathodic arc deposition exhibit very high hardness and elastic modulus, high mass density, low coefficient of friction, and the films are very smooth. All these properties are beneficial to applications of these films for the head/disk interface tribology. The properties of cathodic arc deposited amorphous carbon films are summarized, and they are compared to sputter deposited, hydrogenated (CHx), and nitrogenated (CNx) carbon films which are the present choice for hard disk and slider coatings. New developments in cathodic arc coaters are discussed which are of interest to the disk drive industry. Experiments on the nanotribology, mass density and hardness, corrosion behavior, and tribochemical behavior of cathodic arc films are reported. A number of applications of cathodic arc deposited films to hard disk and slider coatings are described. It is shown that their tribological performance is considerably better compared to CHx and CNx films.
Near-Field Magneto-Optic Fiber Probe
Authors: Seigler M.A. , Lambeth D.N. 
Published: April 2011

AbstractA novel near-field magneto-optic fiber probe (NF-MOFP) for readback of ultra high density magnetic recording, or high resolution imaging of magnetic domains is described. This NFMOFP consists of a partially metalized tapered fiber, as used in conventional near-field scanning optical microscopy (NSOM), with the subwavelength sized aperture coated with a reflective magneto-optic (MO) film. This device is then used in a manner similar to conventional NSOM. The properties of the MO film deposited on the fiber tip, the NFMOFP's response to applied fields, and images of magnetic domains taken with the device are described.
Effect of pH and Concentration on the Synthesis of Monodispersed Spherical Fine Zirconia Powders Using Gas–Liquid Phase Reaction
Authors: Kim Chang–Hyun , Ri Chang–Seop , Lee Dae–Hee , Choo Ho–Sung , Lee Byung–Kyo , Chung Jong–Jae , Kim Song–Dae 
Published: April 2011

ABSTRACTAmmonia gas was blown into the solution of zirconium ion to induce homogeneous precipitation of supersaturated zirconium ion at gas-liquid interface with increase in pH. The precipitates formed using interface of gas-liquid phase were decomposed into fine spherical zirconia powder of high purity. As Concentration increase, mean diameter of particles increases to 140, 180, 240, 290 and 630nm. At pH of 4.5, maximum yield of 98.7% was obtained. From the above pH of 4.5, yield has been kept constant. Above pH of 5.0, large aggregates of precipitate consisting of primary particles were formed, and this may have been caused due to the existence of isoelectric point. Below pH of 4.5, almost aggregate-free fine spherical powders with particle size of below 100nm were produced.
Clay Nanolayer Reinforcement of a Glassy Epoxy Polymer
Authors: Massam Jarrod , Pinnavaia Thomas J. 
Published: April 2011

ABSTRACTGlassy epoxy-clay nanocomposites (Tg ≈ 82 °C) have been prepared by the reaction of diglycidyl ether of bisphenol A and a polyoxyalkylene amine curing agent in the presence of organo cation exchanged smectite (montmorillonite) clays. Commercially available AMS and CWC montmorillonites purified on the industrial scale (Nanocor, Inc.) afforded nanocomposites with performance properties comparable to those obtained from montmorillonite purified by laboratory methods. We provide the first evidence for clay nanolayer reinforcement of a glassy epoxy matrix under compressive strain. Compression stress - strain experiments revealed substantial improvements in the modulus and yield strength when the clay nanolayers were exfoliated in the glassy matrix. However, no improvement in the modulus or yield strength was observed when the clay component was merely intercalated by the epoxy matrix, signifying that nanolayer exfoliation is an essential feature of reinforcement. Furthermore, the mechanical properties of epoxy-clay nanocomposites prepared with the C18H37NH3+ - exchanged forms of the AMS and CWC clays have been tested by dynamic mechanical analysis and thermal mechanical analysis. The nanocomposites exhibit improved dynamic storage modulus above and below the glass transition temperature, as well as lower coefficients of thermal expansivity compared to the pure polymer. In addition, the solvent resistant properties of the nanocomposites are substantially improved compared to the pristine polymer.
Gel mineralization as a Model for Bone Formation
Authors: Calvert Paul , Frechette Joelle , Souvignier Chad 
Published: April 2011

ABSTRACTExtrusion freeform fabrication is a 3-D layerwise writing technique for forming objects directly under the control of a CAD program. This method is one of a family of rapid prototyping methods which include stereolithography, selective laser sintering and fused deposition modeling. This system can be used to build shapes, layer by layer, from hydrogels of agarose, polyacrylamide or other cross-linked water-soluble acrylic polymers.Mineralization can be induced in these gels by first building a part from an aqueous gel slurry containing calcium sulfate powder. This part is then immersed in a carbonate or phosphate solution which diffuses into the gel and precipitates calcite or calcium phosphates as the sulfate slowly dissolves. The resulting material contains 5-10 vol% mineral, 5 vol% agarose and 85-90 vol% water. On drying a bone-like composite is formed. If the original part is not a solid but a mesh of connected struts, the drying step results in a stronger part.
Radiation-Induced Desorption from the Nanopowder
Authors: Khasanov O.L. , Pokholkov Yu.P. , Bondarenko A.L. , Krivobokov V.P. 
Published: April 2011

ABSTRACTThe mechanisms of radiation-induced desorption (RID) from the nanodispersed powder (NDP) surface under the impulse excitation of heavy-current electron beam (HCEB) were studied. Electron-induced desorption (EID); temperature-induced desorption (TID) as a result of radiation heating of the adsorbent; radiation-induced diffusion of the adsorbed atoms; re-adsorption were considered.It was shown that radiation-induced desorption was observed during the first two pulses. The main mechanism of this process was electron-induced desorption (EID).
Investigation for the Selection of Foaming Agents to Produce Steel Foams
Authors: Yu C. J. , Eifert H. H. , Knuewer M. , Weber M. , Baumeister J. 
Published: April 2011

ABSTRACTDuring earlier investigations conducted at the Fraunhofer Institute for Applied Materials Research (IFAM), concentrating on the metal foaming technology using the powder metallurgy process, it was shown that some steel alloys are foamable with Fraunhofer's patented powder technology approach. To further investigate the foamability of steel alloys, suitable foaming agents need to be identified and characterized. This article reports the finding of two metallic compounds used for steel foaming. The foaming behaviors of the selected foaming agents in the steel powder compacts are also evaluated in terms of different alloying elements.
The Influence of Internal Pore Pressure During Roll Forming of Structurally Porous Metals
Authors: Elzey D. M. , Wadley H. N. G. 
Published: April 2011

ABSTRACTStructurally porous metal sandwich panels consisting of dense face sheets and porous cores of controlled relative density can be manufactured by trapping inert gas during hot isostatic pressing and modifying its distribution via subsequent thermo-mechanical forming. At high pressures, the internal gas is expected to influence the forming response. This paper describes a model for the roll forming of a porous metal panel and its use to explore the effects of internal pore pressure upon rolling response. It is shown that for gas pressures below about half the yield strength of the fully dense matrix material, there is essentially no influence on the forming response. Only in the case of very high initial pore pressures or at relative densities approaching full theoretical does a noticeable effect arise. In this case, a limiting upper density is attainable which depends on the specific rolling conditions and geometry.
In-Situ Boron-Doped Epitaxial Silicon Films Grown by UHVRTCVD: Applications in Channel Engineering & Ultra-Shallow Junction Formation
Authors: Ban I. , Öztürk M. C. , LEE K. L. 
Published: April 2011

ABSTRACTA low-thermal budget, in-situ boron doped silicon epitaxy process for channel engineering and ultra shallow junction formation is presented. Ultra-thin silicon films (100–500 Å) have been deposited in a single-wafer Ultra High Vacuum Rapid Thermal Vapor Deposition (UHV-RTCVD) reactor using disilane (Si2H6), diborane (B2H6), and chlorine (Cl2) at temperatures between 750- 800°C. Boron doping can be varied five orders of magnitude (1016 cm-3 1021 cm3) with very abrupt doping transitions (∼50–70 Å/decade). Short channel (Leff =0.12 /μm) lightly-doped nchannel MOSFETs have been successfully realized free of ion-implantation in the channel region. As another application, ultra-shallow, defect-free, abrupt junctions (<500 Å) through diffusion from selectively-deposited in-situ boron doped films have been demonstrated.
Issues in Emissivity of Silicon
Authors: Abedrabbo S. , Hensel J. C. , Gokce O. H. , Tong F. M. , Sopori B. , Fiory A. T. , Ravindra N. M. 
Published: April 2011

ABSTRACTThe first qualitative results of the effects of backside surface roughness on the radiative properties of silicon as a function of temperature in the wavelength range of 1–20μm are presented in this study. These measurements have been made utilizing a spectral emissometer operating at near- and mid-IR spectral range. Surface roughness of the silicon wafer has been observed to lead to increased emissivities.
Real-Time X-Ray Scattering Study of Surface Dynamics on Au(111) During Ar+ Ion Irradiation
Authors: Murty M.V. Ramana , Curcic T. , Judy A. , Cooper B.H. , Woll A.R. , Brock J.D. , Kycia S. , Headrick R.L. 
Published: April 2011

AbstractX-ray scattering is used to investigate the surface dynamics on Au(111) during Ar+ ion irradiation. During 500 eV Ar+ ion irradiation, we observe the three regimes of step retraction, quasi-layer-by-layer removal and three dimensional rough erosion, analagous to molecular beam epitaxy. The quasi-layer-by-layer sputtering regime has been studied to identify similarities and differences in surface evolution during ion irradiation and molecular beam epitaxy. X-ray measurements suggest that 500 eV Ar+ ion irradiation does not lead to stable adatom island formation. Also, in contrast to molecular beam epitaxy, adatom detachment and diffusion seems important in describing the surface kinetics during ion irradiation.
Lattice Statics Green's Function for Modeling of Dislocations in Crystals
Authors: Tewary V.K. 
Published: April 2011

AbstractA lattice statics Green's function method is described for modeling an edge dislocation in a crystal lattice. The edge dislocation is created by introducing a half plane of vacancies as in Volterra's construction. The defect space is decomposed into a part that has translation symmetry and a localized end space. The Dyson's equation for the defect Green's function is solved by using a defect space Fourier transform method for the translational part and matrix partitioning for the localized part. Preliminary results for a simple cubic model are presented.
Self-Organization of Fullerene Clusters
Authors: Rotkin Slava V. 
Published: April 2011

AbstractThe paper introduces the plasmon-Frenkel-exciton model [1] for the fullerene solids and explains a possible reason for the formation of the van-der-Waals [2] C50 cluster complexes. The interaction of the cluster and the organic (non-polar) liquid solvent will be considered. The motivation of this interest is related also to the experiments on the photoclusterization in the water solution [4] and cluster formation in beams [5].
Characterization of InGaN/GaN-Based Multi-Quantum Well Distributed Feedback Lasers
Authors: Hofstetter Daniel , Thornton Robert L. , Romano Linda T. , Bour David P. , Kneissl Michael , Donaldson Rose M. , Dunnrowicz Clarence 
Published: April 2011

AbstractWe present a device fabrication technology and measurement results of both optically pumped and electrically injected InGaN/GaN-based distributed feedback (DFB) lasers operated at room temperature. For the optically pumped DFB laser, we demonstrate a complex coupling scheme for the first time, whereas the electrically injected device is based on normal index coupling. Threshold currents as low as 1. 1 A were observed in 500 μm long and 10 μm wide devices. The 3rd order grating providing feedback was defined holographically and dry-etched into the upper waveguiding layer by chemically-assisted ion beam etching. Even when operating these lasers considerably above threshold, a spectrally narrow emission (3.5 Å) at wavelengths around 400 nm was seen.
Ion Channeling Analysis of Gallium Nitride Implanted with Deuterium
Authors: Wampler W. R. , Myers S. M. 
Published: April 2011

AbstractIon channeling and transmission electron microscopy were used to examine the microstructure of GaN implanted with deuterium (D) at high (>1 at. %) and low (< 0.1 at. %) D concentrations. At high concentrations, bubbles and basal-plane stacking faults were observed. Ion channeling showed the D was disordered relative to the GaN lattice, consistent with precipitation of D2 into bubbles. At low D concentrations, bubbles and stacking faults are absent and ion channeling shows that a large fraction of the D occupies sites near the center of the c-axis channel.
Tem Study of Defects in Laterally Overgrown GaN Layers
Authors: Liliental-Weber Z. , Benamara M. , Swider W. , Washburn J. , Park J. , Grudowski P. A. , Eiting C. J. , Dupuis R. D. 
Published: April 2011

AbstractTransmission electron microscopy was applied to study defects in laterally overgrown GaN layers, with initial growth on A12O3 substrates followed by further growth over SiO2 masks. Dislocations found in the overgrown areas show changes in line direction. Most dislocations propagate along c-planes. In the overgrown material planar defects (faulted loops) are present on c-planes and their presence is most probably related to segregation of excess point defects and impurities present in this material. They appear to be initiated by the fast lateral growth. Some dislocations with screw orientation become helical resulting from climb motion.Formation of voids and also a high dislocation density was observed at the boundaries where two overgrowing fronts meet. Tilt and twist components were observed for these boundaries that were different for different overgrown strips grown in the same crystallographic direction suggesting that the GaN subgrain orientations on the two sides of a SiO2 mask are responsible for the final tilt and twist value.
Electronic Structure and Optical Properties of ZnGeN2
Authors: Limpijumnong Sukit , Rashkeev Sergey N. , Lambrecht Walter R. L. 
Published: April 2011

AbstractThe electronic band structure, structural and bonding, and some linear and nonlinear optical properties are calculated for a new ternary nitride compound ZnGeN2 using first-principles methods. Good agreement is obtained with crystallographic data and with absorption data on the band gap. The prospects for use as nonlinear optical material are discussed.
Effect of Oxygen ION Implantation in Gallium Nitride
Authors: Jiang W. , Weber W.J. , Thevuthasan S. , Exarhos G.J. , Bozlee B.J. 
Published: April 2011

AbstractEpitaxial single crystal GaN films (2.0 μtm thick) were implanted 60° off the <0001> surface normal with 600 keV O+ ions at 190 or 210 K over a range of ion fluences from 4.8x 1017 to 5.0 × 1020 ions/m2. The implantation damage, as determined by in-situ Rutherford Backscattering Spectrometry in a <0001> channeling geometry (RBS/C), ranged from dilute defects up to the formation of a disorder saturation state that was not fully amorphous. The relative disorder on the Ga sublattice exhibited a sigmoidal dependence on ion fluence. Results show that GaN crystals are extremely resistant to the ion implantation damage as compared to other ceramic materials like SiC. An asymmetric shape in the angular scan curve around the <0001> axis, which might be associated with the Ga lattice distortion in the crystal structure, was observed for the as-irradiated material to the highest ion fluence (5.o× 1020 O+/m2) at 210 K. Comparisons of Ga disorder depth-profiles from the experiment and SRIM97 simulations suggest that the damage peaks shift to greater depths at the low irradiation temperature (210 K). Significant recovery of these defects was not observed in the isochronal annealing steps (20-min) up to 970 K.
Contact Resistance of InGaN/GaN Light Emitting Diodes Grown on the Production Model Multi-Wafer Movpe Reactor
Authors: Chuang R.W. , Zou A.Q. , Lee H.P. , Dong Z.J. , Xiong F.F. , Shih R. , Bremser M. , Juergensen H. 
Published: April 2011

AbstractWe report both the device fabrication and characterization of InGaN/GaN single quantum well LEDs grown on sapphire substrates using multi-wafer MOVPE reactor. To improve current spreading of the LEDs, a self-aligned process is developed to define LED mesa that is coated with a thin, semi-transparent Ni/Au (40 Å/40 Å) layer. A detailed study on the ohmic contact resistance of Ni/Cr/Au on p-GaN versus annealing temperatures is carried out on transmission line test structures. It was found that the annealing temperatures between 300 to 500°C yield the lowest specific contact resistance rc (0.016 Ω-cm2 at a current density of 66.7 mA/cm). Based on the extracted rc from the transmission line measurement, we estimate that the contact resistance of the p-type GaN accounts for ∼ 88% of the total series resistance of the LED.
Amplification Path Length Dependence Studies of Stimulated Emission from Optically Pumped InGaN/GaN Multiple Quantum Wells
Authors: Schmidt T.J. , Bidnyk S. , Cho Yong-Hoon , Fischer A.J. , Song J.J. , Keller S. , Mishra U.K. , DenBaars S.P. 
Published: April 2011

AbstractOptically pumped stimulated emission (SE) from InGaN/GaN multiple quantum wells (MQWs) grown by metalorganic chemical vapor deposition has been systematically studied as a function of excitation length (Lexc). Two distinct SE peaks were observed from these structures: one that originates at 425 nm at 10 K (430 nm at 300 K) and another that originates at 434 nm at 10 K (438 nm at 300 K). The SE threshold for the high energy peak was observed to always be lower than that of the low energy peak, but the difference was found to decrease greatly with increasing Lexc. A detailed study of the emission intensity of these two SE peaks as a function of excitation density shows that the two peaks compete for gain in the MQW active region.
Piezoelectric Properties of GaN Self-Organized Quantum Dots
Authors: Daudin B. , Widmann F. , Simon J. , Feuillet G. , Rouvi&re J. L. , Pelekanos N. T. , Fishman G. 
Published: April 2011

AbstractIt is demonstrated that GaN quantum dots with the wurtzite structure grown by molecular beam epitaxy on AIN exhibit optical properties which, depending on the size of the dots, may be dominated by piezoelectric effects. In “large” quantum dots with an average height and diameter of 4.1 and 17 nm, respectively, the photoluminescence peak is centered at 2.95 eV, nearly 0.5 eV below the bulk GaN bandgap, which is assigned to a piezoelectric field of 5.5 MV/cm present in the dots. The decay time of the photoluminescence was also measured. A comparison is carried out with theoretical calculation of the radiative lifetime.
On the Triggering of Shear Faults During Brittle Compressive Failure: A New Mechanism
Authors: Schulson E. M. , Iliescu D. , Renshaw C. E. 
Published: April 2011

AbstractDirect observations are presented of the micromechanical events that contribute to the localization of deformation within brittle compressive shear faults. The observations were made on ice and show that faults are composed of both wing cracks and splay cracks. The latter features initiate from one side of inclined parent cracks and create sets of slender microcolumns fixed on one end and free on the other. It is proposed that the fault-triggering mechanism is the breaking of near-surface microcolumns owing to frictional sliding across their free ends. A lower-bound estimate of the compressive strength of ice is found to be in order of magnitude agreement with experiment.
Creep Cavitation Enhanced by Glass Pocket Formation in a Tetragonal Zirconia Doped with 0.3 WT% Pure Silica
Authors: Morita K. , Hiraga K. , Sakka Y. 
Published: April 2011

AbstractThe relationship between intergranular microstructures and cavitation is examined in a yttria-stabilized tetragonal zirconia doped with 0.2-0.4 wt% SiO2 under constant stress loading in tension. An increase in the initial grain size for a constant SiO2-addition or an increase in SiO2-addition for a constant grain size enhances the precipitation of a glass phase at the multiple grain junctions during deformation. Simultaneously with the enhanced glass phase precipitation, intergranular cavitation is also enhanced. This is because the precipitated glass phase act as the site of cavity formation.
Plastic Dynamics and Brittle vs. Ductile Failure in Noncrystalline Solids
Authors: Falk M.L. 
Published: April 2011

AbstractWe simulate fracture in two amorphous solids with different inter-particle potentials. These small changes in potential result in significant changes in dissipation near the crack tip. While one might expect these effects to arise from a change in flow stress, measurements reveal this is not the case. To understand why, we consider the relationship between crack dynamics, rate-dependent plasticity, and molecular-level structures in the glassy solid. In particular we discuss the macro-scale continuum theory of dynamic brittle fracture in a viscoplastic solid developed by Freund and Hutchinson and the meso-scale theory of viscoplasticity proposed by Falk and Langer. We further consider a simplified model on the molecular scale as a first-step toward the construction of first-principles models of dynamic plasticity and the brittle ductile transition in noncrystalline materials.