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Purdue University

Nanoscience and Nanotechnology

2009

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Articles 1 - 30 of 88

Full-Text Articles in Engineering

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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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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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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Entropy Considerations In Numerical Simulations Of Non-Equilibrium Rarefied Flows, Sruti Chigullapalli, A. Venkattraman, M. S. Ivanov, Alina A. Alexeenko Nov 2009

Entropy Considerations In Numerical Simulations Of Non-Equilibrium Rarefied Flows, Sruti Chigullapalli, A. Venkattraman, M. S. Ivanov, Alina A. Alexeenko

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

Non-equilibrium rarefied flows are encountered frequently in supersonic flight at high altitudes, vacuum technology and in microscale devices. Prediction of the onset of non-equilibrium is important for accurate numerical simulation of such flows. We formulate and apply the discrete version of Boltzmann’s H-theorem for analysis of non-equilibrium onset and accuracy of numerical modeling of rarefied gas flows. The numerical modeling approach is based on the deterministic solution of kinetic model equations. The numerical solution approach comprises the discrete velocity method in the velocity space and the finite volume method in the physical space with different numerical flux schemes: the first-order, …

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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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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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Orbital Stark Effect And Quantum Confinement Transition Of Donors In Silicon, Rajib Rahman, G P. Lansbergen, Seung H. Park, J Verduijn, Gerhard Klimeck, S Rogge, Lloyd Cl Hollenberg Oct 2009

Orbital Stark Effect And Quantum Confinement Transition Of Donors In Silicon, Rajib Rahman, G P. Lansbergen, Seung H. Park, J Verduijn, Gerhard Klimeck, S Rogge, Lloyd Cl Hollenberg

Birck and NCN Publications

Adiabatic shuttling of single impurity bound electrons to gate-induced surface states in semiconductors has attracted much attention in recent times, mostly in the context of solid-state quantum computer architecture. A recent transport spectroscopy experiment for the first time was able to probe the Stark shifted spectrum of a single donor in silicon buried close to a gate. Here, we present the full theoretical model involving large-scale quantum mechanical simulations that was used to compute the Stark shifted donor states in order to interpret the experimental data. Use of atomistic tight-binding technique on a domain of over a million atoms helped …

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Orbital Stark Effect And Quantum Confinement Transition Of Donors In Silicon, Rajib Rahman, G P. Lansbergen, Seung H. Park, J Verduijn, Gerhard Klimeck, S Rogge, Lloyd Cl Hollenberg Oct 2009

Orbital Stark Effect And Quantum Confinement Transition Of Donors In Silicon, Rajib Rahman, G P. Lansbergen, Seung H. Park, J Verduijn, Gerhard Klimeck, S Rogge, Lloyd Cl Hollenberg

Birck and NCN Publications

Adiabatic shuttling of single impurity bound electrons to gate-induced surface states in semiconductors has attracted much attention in recent times, mostly in the context of solid-state quantum computer architecture. A recent transport spectroscopy experiment for the first time was able to probe the Stark shifted spectrum of a single donor in silicon buried close to a gate. Here, we present the full theoretical model involving large-scale quantum mechanical simulations that was used to compute the Stark shifted donor states in order to interpret the experimental data. Use of atomistic tight-binding technique on a domain of over a million atoms helped …

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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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Impact Of Sacrificial Layer Type On Thin-Film Metal Residual Stress, Anurag Garg, Joshua A. Small, Xiaoguang Liu, Ajit Mahapatro, Dimitrios Peroulis Oct 2009

Impact Of Sacrificial Layer Type On Thin-Film Metal Residual Stress, Anurag Garg, Joshua A. Small, Xiaoguang Liu, Ajit Mahapatro, Dimitrios Peroulis

Birck and NCN Publications

In this paper we study the impact of two sacrificial layers on the final residual stress of thin gold films. In particular, we comapre a typical photoresist layer (Shipley SC1827) to single-crystalline silicon. We fabricate and measure cantilever beams on both sacrificial layers and study their residual stresses by analyzing the final displacement profile of the released beams. All samples were fabricated at the same time and under identical conditions. The study clearly shows that the induced stress on thin films is dependent on the sacrificial layer. The gold film deposited over the single-crystalline silicon shows nearly zero gradient stress …

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Molecular Dynamics Simulations Of Lattice Thermal Conductivity Of Bismuth Telluride Using Two-Body Interatomic Potentials, Bo Qiu, X Ruan Oct 2009

Molecular Dynamics Simulations Of Lattice Thermal Conductivity Of Bismuth Telluride Using Two-Body Interatomic Potentials, Bo Qiu, X Ruan

Birck and NCN Publications

Two-body interatomic potentials in the Morse potential form have been developed for bismuth telluride, and the potentials are used in molecular dynamics simulations to predict the thermal conductivity. The density-functional theory with local-density approximations is first used to calculate the total energies for many artificially distorted Bi2Te3 configurations to produce the energy surface. Then by fitting to this energy surface and other experimental data, the Morse potential form is parameterized. The fitted empirical interatomic potentials are shown to reproduce the elastic and phonon data well. Molecular dynamics simulations are then performed to predict the thermal conductivity of bulk Bi2Te3 at …

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Determination Of Size Effects During The Phase Transition Of A Nanoscale Au-Si Eutectic, B J. Kim, J Tersoff, C Y. Wen, M C. Reuter, E A. Stach, F M. Ross Oct 2009

Determination Of Size Effects During The Phase Transition Of A Nanoscale Au-Si Eutectic, B J. Kim, J Tersoff, C Y. Wen, M C. Reuter, E A. Stach, F M. Ross

Birck and NCN Publications

The phase diagram of a nanoscale system can be substantially different than in the bulk, but quantitative measurements have proven elusive. Here we use in situ microscopy to observe a phase transition in a nanoscale system, together with a simple quantitative model to extract the size effects from these measurements. We expose a Au particle to disilane gas, and observe the transition from a two-phase Au + AuSi system to single-phase AuSi. Size effects are evident in the nonlinear disappearance of the solid Au. Our analysis shows a substantial shift in the liquidus line, and a discontinuous change in the …

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

Observation Of Quantum-Hall Effect In Gated Epitaxial Graphene Grown On Sic (0001), T Shen, J J. Gu, Y Q. Wu, M L. Bolen, Michael A. Capano, L W. 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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Molecular Dynamics Simulations Of Lattice Thermal Conductivity Of Bismuth Telluride Using Two-Body Interatomic Potentials, Bo Qiu, X Ruan Oct 2009

Molecular Dynamics Simulations Of Lattice Thermal Conductivity Of Bismuth Telluride Using Two-Body Interatomic Potentials, Bo Qiu, X Ruan

Birck and NCN Publications

Two-body interatomic potentials in the Morse potential form have been developed for bismuth telluride, and the potentials are used in molecular dynamics simulations to predict the thermal conductivity. The density-functional theory with local-density approximations is first used to calculate the total energies for many artificially distorted Bi2Te3 configurations to produce the energy surface. Then by fitting to this energy surface and other experimental data, the Morse potential form is parameterized. The fitted empirical interatomic potentials are shown to reproduce the elastic and phonon data well. Molecular dynamics simulations are then performed to predict the thermal conductivity of bulk Bi2Te3 at …

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Sers In Salt Wells, G. V. Pavan Kumar, Joseph Irudayaraj Oct 2009

Sers In Salt Wells, G. V. Pavan Kumar, Joseph Irudayaraj

Birck and NCN Publications

We report herein a simple, inexpensive fabrication methodology of salt microwells, and define the utility of the latter as nanoparticle containers for highly sensitive surface-enhanced Raman scattering (SERS) studies. AFM characterization of Ag and Au loaded salt microwells reveal the ability to contain favorable nanostructures such as nanoparticle dimers, which can significantly enhance the Raman intensity of molecules. By performing diffraction-limited confocal Raman microscopy on salt microwells, we show high sensitivity and fidelity in the detection of dyes, peptides, and proteins, as a proof of our concept. The SERS limit of detection (accumulation time of 1 s) for rhodamine B …

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Squeeze-Film Damping Of Flexible Microcantilevers At Low Ambient Pressures: Theory And Experiment, Jin Woo Lee, Ryan Tung, Arvind Raman, Hartono Sumali, John Sullivan Sep 2009

Squeeze-Film Damping Of Flexible Microcantilevers At Low Ambient Pressures: Theory And Experiment, Jin Woo Lee, Ryan Tung, Arvind Raman, Hartono Sumali, John Sullivan

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

An improved theoretical approach is proposed to predict the dynamic behavior of long, slender and flexible microcantilevers affected by squeeze-film damping at low ambient pressures. Our approach extends recent continuum gas damping models which were originally derived for a rigid oscillating plate near a wall, to flexible microcantilevers for calculating and predicting squeeze-film damping ratios of higher order bending modes at reduced ambient pressures. Theoretical frequency response functions are derived for a flexible microcantilever beam excited both inertially and via external forcing. Experiments performed carefully at controlled gas pressures are used to validate our theoretical approach over five orders of …

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Mapping Donor Electron Wave Function Deformations At A Sub-Bohr Orbit Resolution, Seung Park, Rajib Rahman, Gerhard Klimeck, Lloyd Cl Hollenberg Sep 2009

Mapping Donor Electron Wave Function Deformations At A Sub-Bohr Orbit Resolution, Seung Park, Rajib Rahman, Gerhard Klimeck, Lloyd Cl Hollenberg

Birck and NCN Publications

Quantum wave function engineering of dopant-based Si nanostructures reveals new physics in the solid state, and is expected to play a vital role in future nanoelectronics. Central to any fundamental understanding or application is the ability to accurately characterize the deformation of the electron wave functions in these atom-based structures through electric and magnetic field control. We present a method for mapping the subtle changes that occur in the electron wave function through the measurement of the hyperfine tensor probed by Si-29 impurities. We calculate Stark parameters for six shells around the donor. Our results show that detecting the donor …

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Optically Induced Electrokinetic Patterning And Manipulation Of Particles, Stuart J. Williams, Aloke Kumar, Steven Wereley Sep 2009

Optically Induced Electrokinetic Patterning And Manipulation Of Particles, Stuart J. Williams, Aloke Kumar, Steven Wereley

Birck and NCN Publications

The ability to easily and dynamically control fluid mo- tion as well as manipulate particles in suspension is impor- tant for the development and characterization of a variety of lab-on-a-chip processes. Recently, we have introduced an op- tically induced electrokinetic technique termed rapid electro- kinetic patterning (REP) that can rapidly concentrate, trans- late, and pattern colloids of many different sizes and compositions. We have tested polystyrene, latex, and silica beads in sizes ranging from 49 nm to 3.0 um.1,2

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Graphene Formation Mechanisms On 4h-Sic(0001), Michael Bolen, Sara E. Harrison, Laura B. Biedermann, Michael A. Capano Sep 2009

Graphene Formation Mechanisms On 4h-Sic(0001), Michael Bolen, Sara E. Harrison, Laura B. Biedermann, Michael A. Capano

Birck and NCN Publications

Graphene is created through thermal decomposition of the Si face of 4H-SiC in high-vacuum. Growth temperature and time are varied independently to gain a better understanding of how surface features and morphology affect graphene formation. Growth mechanisms of graphene are studied by ex situ atomic force microscopy (AFM) and scanning tunneling microscopy (STM). On the route toward a continuous graphene film, various growth features, such as macroscale step bunching, terrace pits, and fingers, are found and analyzed. Topographic and phase AFM analysis demonstrates how surface morphology changes with experimental conditions. Step-bunched terraces and terrace pits show a strong preference for …

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Graphene Formation Mechanisms On 4h-Sic(0001), Michael Bolen, Sara E. Harrison, Laura Biedermann, Michael A. Capano Sep 2009

Graphene Formation Mechanisms On 4h-Sic(0001), Michael Bolen, Sara E. Harrison, Laura Biedermann, Michael A. Capano

Birck and NCN Publications

Graphene is created through thermal decomposition of the Si face of 4H-SiC in high-vacuum. Growth temperature and time are varied independently to gain a better understanding of how surface features and morphology affect graphene formation. Growth mechanisms of graphene are studied by ex situ atomic force microscopy (AFM) and scanning tunneling microscopy (STM). On the route toward a continuous graphene film, various growth features, such as macroscale step bunching, terrace pits, and fingers, are found and analyzed. Topographic and phase AFM analysis demonstrates how surface morphology changes with experimental conditions. Step-bunched terraces and terrace pits show a strong preference for …

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Strain Energy And Lateral Friction Force Distributions Of Carbon Nanotubes Manipulated Into Shapes By Atomic Force Microscopy, Mark C. Strus, Roya R. Lahiji, Pablo Ares, Vincente Lopez, Arvind Raman, Ron R. Reifenberger Aug 2009

Strain Energy And Lateral Friction Force Distributions Of Carbon Nanotubes Manipulated Into Shapes By Atomic Force Microscopy, Mark C. Strus, Roya R. Lahiji, Pablo Ares, Vincente Lopez, Arvind Raman, Ron R. Reifenberger

Other Nanotechnology Publications

The interplay between local mechanical strain energy and lateral frictional forces determines the shape of carbon nanotubes on substrates. In turn, because of its nanometer-size diameter, the shape of a carbon nanotube strongly influences its local electronic, chemical, and mechanical properties. Few, if any, methods exist for resolving the strain energy and static frictional forces along the length of a deformed nanotube supported on a substrate. We present a method using nonlinear elastic rod theory in which we compute the flexural strain energy and static frictional forces along the length of single walled carbon nanotubes (SWCNTs) manipulated into various shapes …

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