bluuebunny/crossref_metadata_2025_split huggingface dataset:
Particularities of Powerful Ultrasound Action on Nanostructuired Powders
Authors: Khasanov O.L. , Pokholkov Yu.P. , Sokolov V.M. , Dvilis E.S. , Bikbaeva Z.G. , Polisadova V.V. 
Published: April 2011

ABSTRACTThe conditions of in ultrasound (US) transmission through a nanodispersed powder (NP) and possible effects of US-action at compacting of NP ZrO2 − Y2O3 are analyzed. These effLcts include agglomerate crushing, NP particle activation under the conditions of acoustic flows; dense NP compacting with the preservation of a compact nanostructure in the absence of acoustic flows. It was shown that the result of 13S action was dcfined by the compacting pressure P and ItS intensity level I, the values of which were divided into the ranges by the critical parameters PC and IC NP transfers from the state of gas-dispersed medium to the state of a solid porous body at P = PC, and IC characterizes the threshold of acoustic flows appearance in the powder body.
Development and Scale-up of the Low Density Core Process for Ti-64
Authors: Schwartz D. S. , Shih D. S. , Lederich R. J. , Martin R. L. , Deuser D. A. 
Published: April 2011

ABSTRACTThe Low Density Core (LDC) process is a method for making metallic structures with solid surfaces covering a porous core. The development of the LDC process for making Ti-64 sheet based structures is described. Sheets ∼ 2000 × 1200 × 4 mm3 have been made with ∼ 40 vol. % core porosity levels, and several forming techniques have been demonstrated. The LDC billet breakdown and forming behavior was found to be similar to conventional Ti-64 processes, so LDC Ti-64 sheet has the advantage that it can be fabricated into structures using well-established methods.
The Effect of GASAR Processing Parameters on Porosity and Properties in Aluminum Alloy
Authors: Paradies C. J. , Tobin A. , Wolla Jeff 
Published: April 2011

ABSTRACTThe GASAR process involves the dissolution of hydrogen in a molten metal or alloy by controlling the hydrogen pressure and the temperature in a high pressure chamber. The difference between the hydrogen solubility in the melt and the solid is used to control the growth of hydrogen pores within the solidifying structure. Designed experiments have been performed to determine the relative effects of the saturation pressure, temperature, casting pressure, mold temperature and cooling rate on the total porosity, pore size, distribution and shape in pure nickel and aluminum alloys. The shape and distribution of pores was found to depend upon the structure of the primary solid during pore nucleation and growth. Reducing the casting pressure had the strongest effect on increasing the total porosity and pore size.
Evaluation and Comparison of 3.0 nm Gate-Stack Dielectrics for Tenth-Micron Technology NMOSFETs
Authors: Yee K. F. , Osburn C. M. , Masnari N. A. , Hauser J. R. , Parker C. G. , Lucovsky G. , Henson W. K. , Wortman. J. J. , Kippenberg T. , Kuerschner S. 
Published: April 2011

ABSTRACTAs device dimensions continue to scale down into the deep submicrometer regime, there is an increasing challenge for fabricating robust gate dielectrics with low susceptibility to process-induced device degradation and a continuous motivation for the exploration of new options for thin gate dielectrics. This work assesses a variety of gate stack processing techniques as alternatives to conventionally furnace grown gate oxides in the context of a tenth-micron technology, which features LOCOS isolated, two-implant channel, NMOS transistors fabricated with a 3.0 nm thick gate dielectric, 0.15 μm thick polysilicon gate, implanted extension- and contact-junctions of 20 and 50 nm deep, respectively, and effective channel lengths down to 0.12 μm, operating at 1.2 volts. The alternative deposition and oxidation techniques include furnace oxynitride formation, rapid-thermal oxidation (RTO), rapid-thermal chemical vapor deposition (RTCVD) and plasma-assisted chemical vapor deposition (RPECVD). Compared to the 0.25- and 0.18-μm technological nodes, the thermal budgets associated with gate oxide formation are dramatically lower and their impact on channel dopant redistribution is not as strong as in previous technologies. Negligible polysilicon depletion effects were observed in the fabricated devices (Cinv/Cox = 97%). Drive currents and threshold voltage control comparable to furnace oxides were achieved by alternative gate-stack processing techniques.
Nitrogen Profile Engineering in Thin Gate Oxides
Authors: Kuehne J. , Hattangady S. , Piccirillo J. , Xing G. C. , Miner G. , Lopes D. , Tauber R. 
Published: April 2011

ABSTRACTIn order to prevent boron penetration in PMOS transistors without degrading channel mobility, it is necessary to engineer the distribution of nitrogen introduced into the gate oxide. We have investigated methods of engineering this distribution using nitric oxide (NO) gas in an RTP system to thermally nitride ultra-thin gate oxides. In one approach, the gate oxide is simultaneously grown and nitrided in a mixture of nitric oxide and oxygen. For a 40 Å film, SIMS depth profiling shows that this process moves the nitrogen peak into the bulk of the oxide away from the oxide silicon interface. In another approach, an 11 Å chemical oxide produced by a standard pre-furnace wet clean is nitrided in NO at 800 deg. C. This film is subsequently reoxidized in either oxygen or steam. For an 1100 deg. C., 120 sec RTP reoxidation in oxygen, the final film thickness is 41 Å. The nitrogen has a peak concentration of 5 at. % and the peak is located in the oxide 25 Åfrom the oxide/silicon interface. Ramped voltage breakdown testing was carried out on MOS capacitors built using reoxidized NO nitrided films. They have breakdown characteristics that are equivalent to conventional furnace grown oxides. These films show considerable promise as gate dielectrics for CMOS technologies at geometries of 0.25um and below.
New Approaches for Formation of Ultra-Thin PtSi Layers for Infrared Applications
Authors: Donaton R. A. , Jin S. , Bender H. , Zagrebnov M. , Baert K. , Maex K. , Vantomme A. , Langouche G. 
Published: April 2011

ABSTRACTIn this work we describe the formation of ultra-thin PtSi layers using sputtering for metal deposition and RTP for the silicidation. The problem associated with the controllability of deposition of ultra-thin metal layers can be circumvented by depositing a thick Pt layer followed by a 2-step RTP process with a selective etch step in between. Continuous and uniform 3 nm thick PtSi layers are formed with this technique. Moreover, in another approach similar to the previous one, but in which the first RTP step is omitted, a much smoother PtSi layer is formed. The importance of the interfacial Pt/Si layer formed during metal deposition is described. These processes are totally compatible with CMOS technologies, as shown below.
Transitions in Critical Island Size in Metal (100) and (111) Homoepitaxy: A Self-Consistent Rate Equation Approach
Authors: Popescu Mihail N. , Amar Jacques G. , Family Fereydoon 
Published: April 2011

AbstractA self-consistent rate equation (RE) approach to submonolayer growth for a restricted pair-bond model that is relevant to low and intermediate temperature metal (100) and (111) homoepitaxy is introduced. In contrast to previous standard rate equation results, the transition temperature from i = 1 to a higher critical island size is well predicted along with the average island and monomer densities. It is shown that the method's implicit introduction of short-range correlations between attachment/detachment rates, together with a careful estimate of the escape rates for small clusters, are important factors for a good agreement with the kinetic Monte Carlo simulation results.
Stress Evolution During Growth of Sputtered Ni/Cu Multilayers
Authors: Ramaswamy Vidya , Clemens Bruce M. , Nix William D. 
Published: April 2011

AbstractResults from in-situ measurements of stress during growth of (111)-textured Ni/Cu multilayers with small and large bilayer periods are presented. In multilayers with small bilayer periods, Ni is in uniform tension and Cu in uniform compression. This behavior is modeled as the growth of a coherent multilayer with alloying in the layers. In multilayers with large bilayer periods, stress relaxation is observed but the measured stresses are much lower than expected based on a Mathews-Blakeslee relaxation process. An alternative stress relaxation mechanism based on high defect densities is presented and discussed.
Accelerating the Dynamics of Infrequent Events: Combining Hyperdynamics and Parallel Replica Dynamics to Treat Epitaxial Layer Growth
Authors: Voter A. F. , Germann T. C. 
Published: April 2011

AbstractDuring the growth of a surface, morphology-controlling diffusion events occur over time scales that far exceed those accessible to molecular dynamics (MD) simulation. Kinetic Monte Carlo offers a way to reach much longer times, but suffers from the fact that the dynamics are correct only if all possible diffusion events are specified in advance. This is difficult due to the concerted nature of many of the recently discovered surface diffusion mechanisms and the complex configurations that arise during real growth. Here we describe two new approaches for this type of problem. The first, hyperdynamics, is an accelerated MD method, in which the trajectory is run on a modified potential energy surface and time is accumulated as a statistical property. Relative to regular MD, hyperdynamics can give computational gains of more than 102. The second method offers a way to parallelize the dynamics efficiently for systems too small for conventional parallel MD algorithms. Both methods exploit the infrequent-event nature of the diffusion process. After an introductory description of these methods, we present preliminary results from simulations combining the two approaches to reach near-millisecond time scales on systems relevant to epitaxial metal growth.
Island Size and Environment Dependence of Adatom Capture: Cu/Co Islands on Ru(0001)
Authors: Bartelt M.C. , Evans J.W. , Schmid A.K. , Hwang R.Q. 
Published: April 2011

AbstractThe rate of capture by stable Co islands on Ru(0001) of additionally deposited Cu atoms is quantified using scanning tunneling microscopy, kinetic Monte Carlo simulations, and diffusion equation analyses. We find strong dependence of the capture rates on Co-island size, larger islands showing larger capture rates, qualitatively distinct from self-consistent mean-field predictions. The observed size dependence is shown to reflect larger island-free areas surrounding bigger islands, i.e., a strong correlation between island sizes and separations neglected in mean-field treatments.
Simulation of the Texture Evolution of Aluminium Alloys During Primary Static Recrystallization Using a Cellular Automaton Approach
Authors: Marx V. , Gottstein G. 
Published: April 2011

AbstractA 3D model has been developed to simulate both primary static recrystallization and recovery of cold worked aluminium alloys. The model is based on a modified cellular automaton approach and incorporates the influence of crystallographic texture and microstructure in respect to both mechanisms mentioned above. The model takes into account oriented nucleation using an approach developed by Nes for aluminium alloys. The subsequent growth of the nuclei depends on the local stored energy of the deformed matrix (i.e. the driving pressure) and the misorientation between a growing nucleus and its surrounding matrix (i.e. the grain boundary mobility). This approach allows to model preferred growth of grains that exhibit maximum growth rate orientation relationship, e.g. for aluminium alloys a 40° <111> relationship with the surrounding matrix. The model simulates kinetics, microstructure and texture development during heat treatment, discrete in time and space.
A Finite Element Method for Simulating Interface Motion
Authors: Yu H.H. , Suo Z. 
Published: April 2011

AbstractThis paper describes our recent progress in developing a finite element method for simulating interface motion. Attention is focused on two mass transport mechanisms: interface migration and surface diffusion. A classical theory states that, for interface migration, the local normal velocity of an interface is proportional to the free energy reduction associated with a unit volume of atoms detach from one side of the interface and attach to the other side. We express this theory into a weak statement, in which the normal velocity and any arbitrary virtual motion of the interface relate to the free energy change associated with the virtual motion. An example with two degrees of freedom shows how the weak statement works. For a general case, we divide the interface into many elements, and use the positions of the nodes as the generalized coordinates. The variations of the free energy associated with the variations of the nodal positions define the generalized forces. The weak statement connects the velocity components at all the nodes to the generalized forces. A symmetric, positive-definite matrix appears, which we call the viscosity matrix. A set of nonlinear ordinary differential equations evolve the nodal positions. We then treat combined surface diffusion and evaporation-condensation in a similar method with generalized coordinates including both nodal positions and mass fluxes. Three numerical examples are included. The first example shows the capability of the method in dealing with anisotropic surface energy. The second example is pore-grain boundary separation in the final stage of ceramic sintering. The third example relates to the process of mass reflow in VLSI fabrication.
Microstructural Evolution and Metastability in Active Materials
Authors: Kinderlehrer David 
Published: April 2011

AbstractMetastable systems pose significant problems in both analysis and simulation. We discuss here the evolution of microstructure in a shape-memory alloy where energetic contributions from disparate scales play determining roles. This is a challenge for modelling since the finest length scales cannot be ‘seen’ at macroscopic level. We then provide a mechanism for kinetics that gives a different notion metastability.
Unconditionally Gradient Stable Time Marching the Cahn-Hilliard Equation
Authors: Eyre David J. 
Published: April 2011

AbstractNumerical methods for time stepping the Cahn-Hilliard equation are given and discussed. The methods are unconditionally gradient stable, and are uniquely solvable for all time steps. The schemes require the solution of ill-conditioned linear equations, and numerical methods to accurately solve these equations are also discussed.
Reliabilty of Graded-Index Polymer Optical Fibers
Authors: Blyler L. L. , Salamon T. , Ronaghan C. , Koeppen C. S. 
Published: April 2011

AbstractNewly developed low loss, graded-index polymer optical fibers (GI-POF) are being investigated as high bandwidth media for data transmission in local area networks and for interconnection of large telecommunications and computer systems. These fibers are fabricated by distributing refractive index-raising dopants to form a core profile in a transparent glassy polymer fiber. The long term reliability of the GI-POF depends upon the degree to which the dopant remains immobilized in the polymer glass in service environments. This paper presents a method for assessing the diffusion kinetics of dopants in polymer optical fibers and for relating these measurements to GI-POF profile stability through numerical simulation. Simulated and measured index profile changes are compared to validate the approach.
Chemical Kinetics Models for the Fatigue Behavior of Fused Silica Optical Fiber
Authors: Matthewson M. J. 
Published: April 2011

AbstractThere have been numerous studies of the fatigue and strength behavior of fused silica optical fibers. However, no coherent model has emerged that self-consistently describes the simultaneous effects of stress, temperature and activity of the corroding species (e.g. water). A power law degradation kinetics model (relating the crack growth rate to the applied stress intensity factor, KI) is widely used although various exponential forms based on chemical rate theory have also been proposed. The dependence of fatigue on parameters such as humidity, pH and temperature, has usually been treated in an empirical manner. Sometimes it is even ignored -for example, the service environment is often assumed to be the same as the proof test environment when making lifetime predictions, thus avoiding the need for understanding the humidity dependence; this assumption is often unjustified. This paper reviews the dependence of fatigue on environmental factors and highlights some of the inconsistencies in published data. It is then attempted to present a coherent kinetics model that simultaneously accounts for stress temperature, humidity, etc. Several possible forms of the model are compared to a range of experimental data of several different types. The comparison is made using fitting techniques that account for correlation between fit parameters. It is found that a simple exponential form of the degradation kinetics model gives the best overall description of the temperature, humidity and pH effects on static and dynamic fatigue. It should be noted that the exponential form predicts shorter lifetimes than the ubiquitous power law model. Therefore, under some circumstances, the predictions of “worst case” models based on power law kinetics are unduly optimistic.
Effect of Refractory Particles on the Strength of Optical Fibers
Authors: Wissuchek D. J. 
Published: April 2011

AbstractSilica-clad optical fibers are proof tested in tension at levels of 700 MPa or greater to ensure product quality. The flaws passing proof testing generally are assumed to be ideal; however, some of these flaws are associated with refractory particles that are fully or partially submerged on the silica surface. Residual stresses are generated in the silica due to a thermal expansion mismatch between the particles and the host silica. These stresses can affect the crack growth characteristics and lifetime predictions for silica-clad optical fibers.Residual stresses around refractory particles are quantified using analytical and finite element models. Zirconia particles generate the highest stresses at low aspect ratios. As aspect ratio increases, materials with higher elastic moduli, such as SiC, generate the highest stress levels. The residual stress fields are incorporated into crack stress intensity relations and their effect on optical fiber strength is evaluated for different refractory materials, particle sizes, and particle aspect ratios. The results are compared to the residual stress fields and stress intensity relations for model flaws created by indentation with diamond pyramids.
Strength and Reliability of Metal-Coated Optical Fibers at High Temperatures
Authors: Biriukov A. S. , Bogatyrjov V. A. , Lebedev V. F. , Sysolyatin A. A. , Khitun A. G. 
Published: April 2011

AbstractHermetically metal coated fibers are candidates for applications at high temperatures. To date, various metals with melting point up to 1400 °C have been used to coat fibers by the freezing technique. However, the major problems consist of ensuring mechanical reliability and acceptable optical losses in metal coated fibers at high temperatures. We present an experimental study of the temperature effects at 20 – 1050 °C on the performance of optical fibers with copper coating. Specific fiber degradation mechanism have been revealed
Highly Reliable Operation of InGaAlAs MESA-Waveguide Photodiodes in Humid Ambient
Authors: Nakamura Hitoshi 
Published: April 2011

AbstractReliability of lnGaAlAs mesa-waveguide photodiodes suitable for low-cost surface integration modules applied to access network systems is investigated. A passivation technique including silicone-based polymer encapsulation was used to ensure high reliability. Under a non-humidity condition of 200°C/10 V, a 9,600-hour stable operation was observed, and the estimated median lifetime is more than 100 years at the field service temperature of 85°C. A measured slight change in the dark current is explained in terms of hole accumulation at the semiconductor-insulator interface. Under a humid condition of 85°C/85% RH/10 V, there was no change in the dark current over 10,000 hours. The observed median lifetime at 135°C/85% RH/10 V of 1,500 hours would lead to an estimated median lifetime at 45°C/50% RH of about 50 years. These results suggest that the WG-PD is applicable to low-cost non-hermetic optical modules for optical access networks.
Utlra-Thermostable Long-Period Gratings Written in Nitrogen-Doped Silica Fibers
Authors: Karpov V. I. , Grekov M. V. , Dianov E. M. , Golant K. M. , Khrapko R. R. 
Published: April 2011

AbstractLong-period gratings were written in nitrogen-doped-silica-core optical fibers by point heating. The periodic variations of the effective refractive index were induced via diffusion of nitrogen from the fiber core. It is shown experimentally that such gratings remain functional at temperatures of up to 1200 °C.
Influence of Active Nitrogen Species on the Nitridation Rate of Sapphire
Authors: Ptak A.J. , Ziemer K.S. , Millecchia M.R. , Stinespring C.D. , Myers T.H. 
Published: April 2011

AbstractThe operating regimes of two rf-plasma sources, an Oxford CARS-25 and an EPI Unibulb, have been extensively characterized. By changing the exit aperture configuration and using an electrostatic deflector, the Oxford source could produce either primarily atomic nitrogen, atomic nitrogen mixed with low energy ions, or a large flux of higher energy ions (>65eV) as the active species in a background of neutral molecular nitrogen. The EPI source produced a significant flux of metastable molecular nitrogen as the active species with a smaller atomic nitrogen component. Nitridation of sapphire using each source under the various operating conditions indicate that the reactivity was different for each type of active nitrogen. Boron contamination originating from the pyrolytic boron nitride plasma cell liner was observed.
Defects in GaN Pyramids Grown on Si(111) Substrates by Selective Lateral Overgrowth
Authors: Mao Zhigang , McKernan Stuart , Carter C. Barry , Yang Wei , McPherson Scott A. 
Published: April 2011

AbstractSelective lateral growth of GaN is a promising technique for producing high quality material for microelectronic and optoelectronic devices. Single-crystal GaN/AIN layers have been grown on Si(111) substrates and subsequently used as the seeding layer for selective lateral overgrowth. GaN pyramids are formed above holes patterned in a Si3N4 mask. Transmission electron microscopy (TEM, which also denotes the microscope) of these structures shows that the GaN pyramid, GaN seed layer, and AIN buffer layer in the samples have the following epitactic relationship with respect to the Si substrate: [1120]GaN || [1120]AIN || [110]Si and (0001)GaN || (0001)AIN || (111)Si. In the core of the pyramid (at or above the seed windows), dislocations thread through the pyramid perpendicular to the interface plane with very high density. Some of these threading dislocations, which originate from the GaN/AIN seed layer, form 90° bends and half loops at the edge of the pyramid core. In the lateral growth part of the GaN pyramid, the dislocation density is relatively low. The majority of dislocations thread through the pyramid parallel to the interface plane. Planar defects, usually parallel to the interface plane, were observed near the interface. The defect density decreases with the distance away from the interface, so that the top several microns of material maybe completely defect free. The mechanism of the growth of GaN pyramids is discussed and related to this defect structure.