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Nanoscience and Nanotechnology

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2009

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Articles 1 - 30 of 184

Full-Text Articles in Engineering

Method Of Transferring Strained Semiconductor Structure, Michael Nastasi Dec 2009

Method Of Transferring Strained Semiconductor Structure, Michael Nastasi

Department of Mechanical and Materials Engineering: Faculty Publications

The transfer of strained semiconductor layers from one substrate to another substrate involves depositing a multilayer structure on a substrate having surface contaminants. An interface that includes the contaminants if formed in between the deposited layer and the substrate. Hydrogen atoms are introduced into the structure and allowed to diffuse to the interface. Afterward, the deposited multilayer structure is bonded to a second substrate and is separated away at the interface, which results in transferring a multilayer structure from one substrate at least one strained semiconductor layer and at least one strain-induced seed layer. The strain-induced seed layer can be …

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Thermal Conduction In Molecular Materials Using Coarse Grain Dynamics: Role Of Mass Diffusion And Quantum Corrections For Molecular Dynamics Simulations, Ya Zhou, Alejandro Strachan Dec 2009

Thermal Conduction In Molecular Materials Using Coarse Grain Dynamics: Role Of Mass Diffusion And Quantum Corrections For Molecular Dynamics Simulations, Ya Zhou, Alejandro Strachan

PRISM: NNSA Center for Prediction of Reliability, Integrity and Survivability of Microsystems

We use a mesodynamical method, denoted dynamics with implicit degrees of freedom DID, to characterize thermal transport in a model molecular crystal below and above its melting temperature. DID represents groups of atoms molecules in this case using mesoparticles and the thermal role of the intramolecular degrees of freedom DoFs are described implicitly using their specific heat. We focus on the role of these intramolecular DoFs on thermal transport. We find that thermal conductivity is independent of intramolecular specific heat for solid samples and a linear relationship between the two quantities in liquid samples with the coefficient of proportionality being …

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Fabrication Methods For Creating Flexible Polymer Substrate Sensor Tags, Jack L. Skinner, Harvey Ho Dec 2009

Fabrication Methods For Creating Flexible Polymer Substrate Sensor Tags, Jack L. Skinner, Harvey Ho

Mechanical Engineering

The authors describe the design, fabrication, and testing of a passive wireless sensor platform utilizing low-cost commercial surface acoustic wave filters and sensors. Polyimide and polyethylene terephthalate sheets are used as substrates to create a flexible sensor tag that can be applied to curved surfaces. A microfabricated antenna is integrated on the substrate in order to create a compact form factor. The sensor tags are fabricated using 315 MHz surface acoustic wave filters and photodiodes and tested with the aid of a fiber-coupled tungsten lamp. Microwave energy transmitted from a network analyzer is used to interrogate the sensor tag. Due …

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Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner Dec 2009

Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner

Mikhail Khenner

A mathematical model for the evolution of pulsed laser-irradiated, molten metallic films has been developed using the lubrication theory. The heat transfer problem that incorporates the absorbed heat from a single laser beam or the interfering laser beams is solved analytically. Using this temperature field, we derive the 3D long-wave evolution PDE for the film height. To get insights into dynamics of dewetting, we study the 2D version of the evolution equation by means of a linear stability analysis and by numerical simulations. The stabilizing and destabilizing effects of various system parameters, such as the reflectivity, the peak laser beam …

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Stochastic Analysis Of Electrostatic Mems Subjected To Parameter Variations, Nitin Agarwal, Narayana R. Aluru Dec 2009

Stochastic Analysis Of Electrostatic Mems Subjected To Parameter Variations, Nitin Agarwal, Narayana R. Aluru

PRISM: NNSA Center for Prediction of Reliability, Integrity and Survivability of Microsystems

This paper presents an efficient stochastic framework for quantifying the effect of stochastic variations in various design parameters such as material properties, geometrical features, and/or operating conditions on the performance of electrostatic microelectromechanical systems (MEMS) devices. The stochastic framework treats uncertainty as a separate dimension, in addition to space and time, and seeks to approximate the stochastic dependent variables using sparse grid interpolation in the multidimensional random space. This approach can be effectively used to compute important information, such as moments (mean and variance), failure probabilities, and sensitivities with respect to design variables, regarding relevant quantities of interest. The approach …

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Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner Dec 2009

Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner

Mathematics Faculty Publications

A mathematical model for the evolution of pulsed laser-irradiated, molten metallic films has been developed using the lubrication theory. The heat transfer problem that incorporates the absorbed heat from a single laser beam or the interfering laser beams is solved analytically. Using this temperature field, we derive the 3D long-wave evolution PDE for the film height. To get insights into dynamics of dewetting, we study the 2D version of the evolution equation by means of a linear stability analysis and by numerical simulations. The stabilizing and destabilizing effects of various system parameters, such as the reflectivity, the peak laser beam …

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Frequency-Domain Simulations Of A Negative-Index Material With Embedded Gain, Yonatan Sivan, Shumin Xiao, Uday K. Chettiar, Alexander V. Kildishev, V. M. Shalaev Dec 2009

Frequency-Domain Simulations Of A Negative-Index Material With Embedded Gain, Yonatan Sivan, Shumin Xiao, Uday K. Chettiar, Alexander V. Kildishev, V. M. Shalaev

Birck and NCN Publications

We solve the equations governing light propagation in a negative-index material with embedded nonlinearly saturable gain material using a frequency-domain model. We show that available gain materials can lead to complete loss compensation only if they are located in the regions where the field enhancement is maximal. We study the increased enhancement of the fields in the gain composite as well as in the metal inclusions and show analytically that the effective gain is determined by the average near-field enhancement.

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Synthesis And Spectroscopic Characterization Of Nanostructured Thermoelectric Materials, Jason Reppert Dec 2009

Synthesis And Spectroscopic Characterization Of Nanostructured Thermoelectric Materials, Jason Reppert

All Dissertations

Bismuth in the bulk form is a semimetal with a rhombohedral structure. It has a small band overlap between the conduction and valence bands and a highly anisotropic electron effective-mass tensor. Thermoelectric materials, in which one of the three dimensions is in the nanometer regime, exhibit unique quantum confinement properties and have generated much interest in recent years. Theoretical investigations have suggested that nanowires with diameters ≤ 10 nm will possess a figure-of-merit ZT > 2. Prior to this study, it has been shown that Bi nanowires with small enough diameters (~10 nm), prepared via the pulsed laser vaporization method, undergo …

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Inter-Tube Bonding And Defects In Carbon Nanotubes And The Impact On The Transport Properties And Micro-Morphology, Keqin Yang Dec 2009

Inter-Tube Bonding And Defects In Carbon Nanotubes And The Impact On The Transport Properties And Micro-Morphology, Keqin Yang

All Dissertations

The transport properties of the carbon nanotubes (CNTs) are affected by the tube-tube interaction and the defects presented in the system. Inter-tube bonding, formed during spark plasma sintering (SPS) process, lowers the electrical/thermal resistivity at the tube-tube junctions and also causes new scattering mechanisms such as strong electron-phonon coupling (EPC) at low temperature. More evidences have been found by changing the SPS temperature and doping the CNTs to support the electron-phonon coupling is Kohn anomaly (KA) in as-SPSed CNTs. The phonon drag, appearing in thermoelectric power (TEP) of the as-SPSed CNTs at low temperature, can be explained in the framework …

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Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner Dec 2009

Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner

Mathematics Faculty Publications

A mathematical model for the evolution of pulsed laser-irradiated, molten metallic films has been developed using the lubrication theory. The heat transfer problem that incorporates the absorbed heat from a single laser beam or the interfering laser beams is solved analytically. Using this temperature field, we derive the 3D long-wave evolution PDE for the film height. To get insights into dynamics of dewetting, we study the 2D version of the evolution equation by means of a linear stability analysis and by numerical simulations. The stabilizing and destabilizing effects of various system parameters, such as the reflectivity, the peak laser beam …

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Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner Dec 2009

Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner

Mathematics Faculty Publications

A mathematical model for the evolution of pulsed laser-irradiated, molten metallic films has been developed using the lubrication theory. The heat transfer problem that incorporates the absorbed heat from a single laser beam or the interfering laser beams is solved analytically. Using this temperature field, we derive the 3D long-wave evolution PDE for the film height. To get insights into dynamics of dewetting, we study the 2D version of the evolution equation by means of a linear stability analysis and by numerical simulations. The stabilizing and destabilizing effects of various system parameters, such as the reflectivity, the peak laser beam …

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Progresses In Electrocatalysis Of Nanomaterials—Tuning The Surface Structure And Property Of Electrocatalysts, Yan-Xia Jiang, Na Tian, Zhi-You Zhou, Sheng-Pei Chen, Shi-Gang Sun Nov 2009

Progresses In Electrocatalysis Of Nanomaterials—Tuning The Surface Structure And Property Of Electrocatalysts, Yan-Xia Jiang, Na Tian, Zhi-You Zhou, Sheng-Pei Chen, Shi-Gang Sun

Journal of Electrochemistry

The property of an electrocatalyst depends strongly on its surface structure.The study of surface structure-catalytic functionality is the base of design and preparation of electrocatalysts of high activity,high stability and high selectivity at microstructure level.In this paper,based mainly on our results concering hydrogen and oxygen adsorption-desorption,ethylene glycol oxidation and CO2 reduction,the research progresses in tuning the surface structure and property of electrocatalysts are summarized.This paper overviews firstly the cyclic voltammetric characteristics,electrocatalytic properties of platinum single crystal planes lying on different crystallographic zones of the unit stereographic triangle of face-centered cubic(fcc) metals.Next,the innovation of electrochemical methods to control the surface structure …

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Synthesis And Electrocatalytic Properties Of Ni-Pd/C Catalysts With Pd-Enriched Surface, Yu-Mei Chen, Zhi-Xiu Liang, Sheng-Li Chen Nov 2009

Synthesis And Electrocatalytic Properties Of Ni-Pd/C Catalysts With Pd-Enriched Surface, Yu-Mei Chen, Zhi-Xiu Liang, Sheng-Li Chen

Journal of Electrochemistry

The Ni-Pd alloy catalysts with Pd-enriched surface were synthesized through a modified polyol process.The synthesized materials were investigated by XRD and electrochemical methods,and tested as electrocatalysts for CH3OH-tolerant oxygen reduction.The results indicated that the synthesized Ni-Pd nanoparticles possess multiple phases containing Pd-Ni alloy and pure Ni.Comparing with Pd/C,the prepared Ni-Pd/C nanoparticles exhibited better resolved voltammetric peaks between the hydrogen absorption and adsorption,and positively shifted current peaks for the reduction of Pd oxide.The prepared Ni-Pd alloys with Pd-enriched surface have significantly enhanced ORR activity and improved CH3OH tolerance as comparing with Pd/C catalysts.

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Complex Reduction Preparation Of Carbon Supported Pd Nanoparticle Catalyst And Its Electrocatalysis For Formic Acid Oxidation, Wei He, Yong-Yin Kang, Chong Du, Zhi-Qing Zou, Xiao-Gang Zhang, Hui Yang Nov 2009

Complex Reduction Preparation Of Carbon Supported Pd Nanoparticle Catalyst And Its Electrocatalysis For Formic Acid Oxidation, Wei He, Yong-Yin Kang, Chong Du, Zhi-Qing Zou, Xiao-Gang Zhang, Hui Yang

Journal of Electrochemistry

A simple procedure involved the complexing of PdCl2 with sodium citrate followed by ethylene glycol reduction has been employed for the preparation of carbon-supported Pd nanoparticles(Pd/C).The XRD and TEM characterizations indicate that Pd nanoparticles with a small particle size were well-dispersed on carbon support.The mean particle sizes of the Pd/C catalysts were found to be increased from 2.7 to 5.8 nm with heat-treatments at different temperature.The mass activity of the Pd/C catalyst for formic acid electrooxidation increased with the decrease in Pd particle size.However,the specific activity increased with Pd particle size.Furthermore,the Pd/C catalyst with a particle size of ca.3.6 nm …

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Cyclic Voltammetric And In-Situ Ftir Spectroscopic Studies Of Adsorption And Reduction Of No On Electrode Of Pt Nanoparticles, Qian Cheng, Yan-Xia Jiang, Dong-Mei Zeng, Shi-Gang Sun Nov 2009

Cyclic Voltammetric And In-Situ Ftir Spectroscopic Studies Of Adsorption And Reduction Of No On Electrode Of Pt Nanoparticles, Qian Cheng, Yan-Xia Jiang, Dong-Mei Zeng, Shi-Gang Sun

Journal of Electrochemistry

Adsorption and reduction of NO on electrode of Pt nanoparticles in acid solutions were studied by means of cyclic voltammetry(CV) and in-situ FTIR spectroscopy.The results indicated that the reduction of NO is a complicated process including the adsorption of NO on electrode surface.Two types of surface-bonded NO were determined on Pt nanoparticles.The weakly adsorbed NO was reduced between 0.6 V and-0.05 V,which yielded nitrous oxide(N2O) and ammonium(NH+4) as products;while the strongly bonded NO was reduced at more negative potentials between-0.05V and-0.15V,producing only NH4+ species.

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Preparation Of Pt Nanoflower/Zno Composites Arrays And Their Electrocatalysis For Methanol Oxidation, Li Gao, Yi-Feng E, Lou-Zhen Fan Nov 2009

Preparation Of Pt Nanoflower/Zno Composites Arrays And Their Electrocatalysis For Methanol Oxidation, Li Gao, Yi-Feng E, Lou-Zhen Fan

Journal of Electrochemistry

The Pt nanoflower/ZnO(PtNF/ZnO) nanorod composites arrays were electrochemically prepared by controlling the hydrophobicity and the hydrophilicity of ZnO nanorods arrays.The Pt nanoflowers grew on the tip of ZnO nanorods,which maintain the vertical array of Zno nanorods with a high degree of size uniformity and high surface area.Compared with Pt nanoparticle covered ZnO nanorod arrays,which were prepared by controlling the hydrophilicities of ZnO nanorods and Pt nanoparticles,the PtNF/ZnO displayed highest electrocatalytic activities for the oxidation of methanol.

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Enhanced Visible Light Photoelectrochemical Performances With Nitrogen Doped Tio_2 Nanowire Arrays, Xiao-Jun Lv, Yue-Ming Li, Hao Zhang, Da Chen, Hensel Jennifer, Z Zhang Jin, Jing-Hong Li Nov 2009

Enhanced Visible Light Photoelectrochemical Performances With Nitrogen Doped Tio_2 Nanowire Arrays, Xiao-Jun Lv, Yue-Ming Li, Hao Zhang, Da Chen, Hensel Jennifer, Z Zhang Jin, Jing-Hong Li

Journal of Electrochemistry

Self-organized anodic anatase TiO2nanowire arrays doped with nitrogen have been successfully fabri-cated and their photoelectrochemical(PEC) properties have been characterized and found to be substantially im-proved compared to undoped nanowires or commercial P25 nanoparticles.Photocurrent measured with monochro-matic incident light showed that the incident photon-to-current efficiency(IPCE,%) values of nanowire arrayelectrodes with or without N-doping were obviously higher than that of commercial P25 nanoparticle electrodes,and nitrogen-doped TiO2nanowire arrays(NTNA) had noticeable absorption in the visible region.The NTNAelectrodes showed the highest photocurrent density and power conversion efficiency under 100 mW/cm2visiblelight illumination.A maximumolphotoconversion efficiency of 0.52% was achieved for the NTNA sample at anapplied potential of …

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Self-Consistent Multiscale Modeling In The Presence Of Inhomogeneous Fields, Ruichang Xiong, Rebecca L. Empting, Ian C. Morris, David J. Keffer Nov 2009

Self-Consistent Multiscale Modeling In The Presence Of Inhomogeneous Fields, Ruichang Xiong, Rebecca L. Empting, Ian C. Morris, David J. Keffer

Faculty Publications and Other Works -- Chemical and Biomolecular Engineering

Molecular dynamics (MD) simulations of a Lennard–Jones fluid in an inhomogeneous external field generate steady-state profiles of density and pressure with nanoscopic heterogeneities. The continuum level of mass, momentum, and energy transport balances is capable of reproducing the MD profiles only when the equation of state for pressure as a function of density is extracted directly from the molecular level of description. We show that the density profile resulting from simulation is consistent with both a molecular-level theoretical prediction from statistical mechanics as well as the solution of the continuum-level set of differential equations describing the conservation of mass and …

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Manifestation Of Kohn Anomaly In 1/F Fluctuations In Metallic Carbon Nanotubes, Ju Hee Back, Cheng-Lin Tsai, Sunkook Kim, Saeed Mohammadi, Moonsub Shim Nov 2009

Manifestation Of Kohn Anomaly In 1/F Fluctuations In Metallic Carbon Nanotubes, Ju Hee Back, Cheng-Lin Tsai, Sunkook Kim, Saeed Mohammadi, Moonsub Shim

Birck and NCN Publications

Low-frequency noise in metallic single walled carbon nanotubes is shown to be strongly dependent on the Fermi level position and the applied electric field across the nanotube. Resonance-like enhancement observed near optical phonon energy only when the Fermi level lies near the Dirac point is correlated to Raman G-band softening and broadening. The results suggest that the competition between zone-center and zone-boundary phonon scattering is the underlying origin of the large enhancement and resonance-like behavior of 1/f noise.

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Imprinting Polymerfilm On Patterned Substrate, Li Tan, Yen-Peng Kong, Stella W. Pang, Albert F. Yee Nov 2009

Imprinting Polymerfilm On Patterned Substrate, Li Tan, Yen-Peng Kong, Stella W. Pang, Albert F. Yee

Department of Mechanical and Materials Engineering: Faculty Publications

A method of applying a pattern on a topography includes first applying a polymer film to an elastormer member, such as PDMS, to form a pad. The pad is then applied to a substrate having a varying topography under pressure. The polymer film is transferred to the substrate due to the plastic deformation of the polymer film under pressure compared to the elastic deformation of the PDMS member pulls away from the polymer layer, thereby depositing the polymer layer, thereby depositing the polymer layer upon the substrate.

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An Unstructured Finite Volume Method For Incompressible Flows With Complex Immersed Boundaries, Lin Sun, Sanjay Mathur, Jayathi Y. Murthy Nov 2009

An Unstructured Finite Volume Method For Incompressible Flows With Complex Immersed Boundaries, Lin Sun, Sanjay Mathur, Jayathi Y. Murthy

PRISM: NNSA Center for Prediction of Reliability, Integrity and Survivability of Microsystems

A numerical method is developed for solving the 3D, unsteady, incompressible flows with immersed moving soldis of arbitrary geometrical complexity. A co-located (non-staggered) finite volume method is employed to solve the Navier-Stokes governing equeations for flow region using arbitrary convex polyhedral meshes. The solid region is represented by a set of material points with known position and velocity. Faces in the flow region located in the immediate vicinity of the solid body are marked as immersed boundary (IB) faces. At every instant in time, the influence of the body on the flowis accounted for by reconstructing implicitly the velocity the …

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Phase Stability And Transformations In Niti From Density, Karthik Guda Vishnu, Alejandro Strachan Nov 2009

Phase Stability And Transformations In Niti From Density, Karthik Guda Vishnu, Alejandro Strachan

PRISM: NNSA Center for Prediction of Reliability, Integrity and Survivability of Microsystems

We used density functional theory to characterize various crystalline phases of NiTi alloys: (i) high-temperature austenite phase B2; (ii) orthorhombic B19; (iii) the monoclinic martensite phase B190; and (iv) a body-centered orthorhombic phase (BCO), theoretically predicted to be the ground state. We also investigated possible transition pathways between the various phases and the energetics involved. We found B19 to be metastable with a 1 meV energy barrier separating it from B190. Interestingly, we predicted a new phase of NiTi, denoted B1900, that is involved in the transition between B190 and BCO. B1900 is monoclinic and can exhibit shape memory; furthermore, …

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Generating Integrated-Circuit Patterns Via Cutting And Stitching Of Gratings, Lin Zhao, Yi Xuan, Minghao Qi Nov 2009

Generating Integrated-Circuit Patterns Via Cutting And Stitching Of Gratings, Lin Zhao, Yi Xuan, Minghao Qi

Birck and NCN Publications

Integrated-circuit patterns, such as those of transistor gates, usually consist of multivertex paths whose line segments are along two orthogonal directions. Such patterns are sometimes called "Manhattan structures" and are typically designed to achieve the highest packing density with a given linewidth. Owing to their arbitrary shapes, these patterns are predominantly generated via electron-beam lithography, a serial process which is inherently slow compared to parallel processes. Moreover, throughput is further reduced with the necessity of proximity correction in electron-beam lithography. On the other hand, interference lithography is a low-cost, parallel process that can achieve small linewidths and pitches, yet the …

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A Domain Adaptive Stochastic Collocation Approach For Analysis Of Mems Under Uncertainties, Nitin Agarwal, N R. Aluru Nov 2009

A Domain Adaptive Stochastic Collocation Approach For Analysis Of Mems Under Uncertainties, Nitin Agarwal, N R. Aluru

Other Nanotechnology Publications

This work proposes a domain adaptive stochastic collocation approach for uncertainty quantification, suitable for effective handling of discontinuities or sharp variations in the random domain. The basic idea of the proposed methodology is to adaptively decompose the random domain into subdomains. Within each subdomain, a sparse grid interpolant is constructed using the classical Smolyak construction [S. Smolyak, Quadrature and interpo- lation formulas for tensor products of certain classes of functions, Soviet Math. Dokl. 4 (1963) 240–243], to approximate the stochastic solution locally. The adaptive strategy is governed by the hierarchical surpluses, which are computed as part of the interpolation procedure. …

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Thermodynamics Of Hydrogen Vacancies In Mgh2 From First-Principles Calculations And Grand-Canonical Statistical Mechanics, R Grau-Crespo, K C. Smith, Timothy Fisher, N H. De Leeuw, U V. Waghmare Nov 2009

Thermodynamics Of Hydrogen Vacancies In Mgh2 From First-Principles Calculations And Grand-Canonical Statistical Mechanics, R Grau-Crespo, K C. Smith, Timothy Fisher, N H. De Leeuw, U V. Waghmare

Birck and NCN Publications

Ab initio calculations and statistical mechanics are combined to elucidate the thermodynamics of H vacancies in MgH2. A general method based on a grand-canonical ensemble of defect configurations is presented to model the exchange of hydrogen between crystalline MgH2 and gas-phase H-2. We find that, even at the lowest hydrogen partial pressures at which the hydride phase is stable, MgH2 is capable of accommodating only very small concentrations of hydrogen vacancies. These vacancies are mainly isolated rather than forming clusters, contrary to what is expected from a simple energetic analysis.

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Observation Of Quantum-Hall Effect In Gated Epitaxial Graphene Grown On Sic (0001), T Shen, J J. Gu, M Xu, Michael Bolen, Michael A. Capano, L Engel, P. D. Ye Oct 2009

Observation Of Quantum-Hall Effect In Gated Epitaxial Graphene Grown On Sic (0001), T Shen, J J. Gu, M Xu, Michael Bolen, Michael A. Capano, L Engel, P. D. Ye

Birck and NCN Publications

Epitaxial graphene films examined were formed on the Si-face of semi-insulating 4H-SiC substrates by a high temperature sublimation process. A high-k gate stack on the epitaxial graphene was realized by inserting a fully oxidized nanometer thin aluminum film as a seeding layer, followed by an atomic-layer deposition process. The electrical properties of epitaxial graphene films are retained after gate stack formation without significant degradation. At low temperatures, the quantum-Hall effect in Hall resistance is observed along with pronounced Shubnikov-de Haas oscillations in diagonal magnetoresistance of gated epitaxial graphene on SiC (0001).

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A Numerical Fatigue Damage Model For Life Scatter Of Mems Devices, Behrooz Jalalahmadi, Farshid Sadeghi, Dimitrios Peroulis Oct 2009

A Numerical Fatigue Damage Model For Life Scatter Of Mems Devices, Behrooz Jalalahmadi, Farshid Sadeghi, Dimitrios Peroulis

PRISM: NNSA Center for Prediction of Reliability, Integrity and Survivability of Microsystems

This paper presents a fatigue damage model to estimate fatigue lives of microelectromechanical systems (MEMS) devices and account for the effects of topological randomness of material microstructure. For this purpose, the damage mechanics modeling approach is incorporated into a new Voronoi finite-element model (VFEM). The VFEM developed for this investigation is able to consider both intergranular crack initiation (debonding) and propagation stages. The model relates the fatigue life to a damage parameter "D" which is a measure of the gradual material degradation under cyclic loading. The fatigue damage model is then used to investigate the effects of microstructure randomness on …

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Numerical Simulation Of Gas-Phonon Coupling In Thermal Transpiration Flows, Xiaohui Guo, Dhruv Singh, Jayathi Murthy, Alina A. Alexeenko Oct 2009

Numerical Simulation Of Gas-Phonon Coupling In Thermal Transpiration Flows, Xiaohui Guo, Dhruv Singh, Jayathi Murthy, Alina A. Alexeenko

PRISM: NNSA Center for Prediction of Reliability, Integrity and Survivability of Microsystems

Thermal transpiration is a rarefied gas flow driven by a wall temperature gradient and is a promising mechanism for gas pumping without moving parts, known as the Knudsen pump. Obtaining temperature measurements along capillary walls in a Knudsen pump is difficult due to extremely small length scales. Meanwhile, simplified analytical models are not applicable under the practical operating conditions of a thermal transpiration device, where the gas flow is in the transitional rarefied regime. Here, we present a coupled gas-phonon heat transfer and flow model to study a closed thermal transpiration system. Discretized Boltzmann equations are solved for molecular transport …

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Gate-Induced G-Factor Control And Dimensional Transition For Donors In Multivalley Semiconductors, Rajib Rahman, Seung H. Park, Timothy B. Boykin, Gerhard Klimeck, Sven Rogge, Lloyd Cl Hollenberg Oct 2009

Gate-Induced G-Factor Control And Dimensional Transition For Donors In Multivalley Semiconductors, Rajib Rahman, Seung H. Park, Timothy B. Boykin, Gerhard Klimeck, Sven Rogge, Lloyd Cl Hollenberg

Birck and NCN Publications

The dependence of the g factors of semiconductor donors on applied electric and magnetic fields is of immense importance in spin-based quantum computation and in semiconductor spintronics. The donor g-factor Stark shift is sensitive to the orientation of the electric and magnetic fields and is strongly influenced by the band-structure and spin-orbit interactions of the host. Using a multimillion atom tight-binding framework, the spin-orbit Stark parameters are computed for donors in multivalley semiconductors, silicon, and germanium. Comparison with limited experimental data shows good agreement for a donor in silicon. Results for gate-induced transition from three-dimensional to two-dimensional wave-function confinement show …

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Atomistic Full-Band Simulations Of Silicon Nanowire Transistors: Effects Of Electron-Phonon Scattering, Mathieu Luisier, Gerhard Klimeck Oct 2009

Atomistic Full-Band Simulations Of Silicon Nanowire Transistors: Effects Of Electron-Phonon Scattering, Mathieu Luisier, Gerhard Klimeck

Birck and NCN Publications

An atomistic full-band quantum transport simulator has been developed to study three-dimensional Si nanowire field-effect transistors in the presence of electron-phonon scattering. The nonequilibrium Green's function (NEGF) formalism is solved in a nearest-neighbor sp(3)d(5)s* tight-binding basis. The scattering self-energies are derived in the self-consistent Born approximation to inelastically couple the full electron and phonon energy spectra. The band dispersion and the eigenmodes of the confined phonons are calculated using a dynamical matrix that includes the bond and the angle deformations of the nanowires. The optimization of the numerical algorithms and the parallelization of the NEGF scheme enable the investigation of …

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