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2007

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Articles 1 - 30 of 66

Full-Text Articles in Nanoscience and Nanotechnology

Creating Micro- And Nanostructures On Tubular And Spherical Surfaces, O. Lima, L. Tan, A. Goel, Lmehrdad Negahban, Z. Li Dec 2007

Creating Micro- And Nanostructures On Tubular And Spherical Surfaces, O. Lima, L. Tan, A. Goel, Lmehrdad Negahban, Z. Li

Faculty Publications from Nebraska Center for Materials and Nanoscience

The authors developed a new technique to create micro- and nanometer scale structures on curved free-standing objects by combining embossing/imprinting lithography approaches with mechanical loadings on elastic films. Embossing/imprinting generates small structures and mechanical loading determines shape or geometry of the final object. As a result, a portion of the tubes with a radius between 0.5 and 3.5 mm and a portion of the spheres with a radius between 2.4 and 7.0 mm were fabricated with grating line features (period of 700 nm) and microlens array features (lens radius of 2.5 µm) atop ...


Fabrication Of Robust Superconducting Granular Aluminium/Palladium Bilayer Microbolometers With Sub-Nanosecond Response, Thomas E. Wilson Dec 2007

Fabrication Of Robust Superconducting Granular Aluminium/Palladium Bilayer Microbolometers With Sub-Nanosecond Response, Thomas E. Wilson

Physics Faculty Research

We provide a convenient recipe for fabricating reliable superconducting microbolometers as acoustic phonon detectors with sub-nanosecond response, using imagereversal optical lithography and dc-magnetron sputtering, and our recipe requires no chemical or plasma etching. Our approach solves the traditional problem for granular aluminium bolometers of unreliable (i.e., non-Ohmic) electrical contacts by sequentially sputtering the granular aluminium film and then a palladium capping layer. We use dc calibration data, the method of Danilchenko et al. [1], and direct nanosecond-pulsed photoexcitation to obtain the microbolometer’s characteristic current, thermal conductance, characteristic relaxation time, and heat capacity. We also demonstrate the use of ...


Simulation Of Phonon Transport Across A Non-Polar Nanowire Junction Using An Atomistic Green's Function Method, W Zhang, N Mingo, Timothy Fisher Nov 2007

Simulation Of Phonon Transport Across A Non-Polar Nanowire Junction Using An Atomistic Green's Function Method, W Zhang, N Mingo, Timothy Fisher

Birck and NCN Publications

Phonon transport across a non-polar nanowire situated between two semi-infinite contacts is simulated in this paper using the atomistic Green's function method. Abrupt geometric changes between the nanowire and bulk contacts are handled by self-energy matrices obtained from bare surface Green's functions. Transport properties such as phonon transmission functions and thermal conductances are calculated, and their dependencies on the interatomic potential, length, diameter, shape, and lattice orientation are investigated. The results reveal that the overall thermal conductance of the nanowire-bulk-contact structure increases with nanowire diameter while the normalized thermal conductance approaches an asymptotic value. Thermal conductance decreases significantly ...


Growth-Temperature Optimization For Low Carrier-Density In0.75Ga0.25As-Based High Electron Mobility Transistors On Inp, Paul J. Simmonds, H. E. Beere, D. A. Ritchie, S. N. Holmes Oct 2007

Growth-Temperature Optimization For Low Carrier-Density In0.75Ga0.25As-Based High Electron Mobility Transistors On Inp, Paul J. Simmonds, H. E. Beere, D. A. Ritchie, S. N. Holmes

Paul J. Simmonds

Two-dimensional electron gases (2DEGs) were formed in undoped In0.75Al0.25As / In0.75Ga0.25As / In0.75Al0.25As quantum wells. The optimal growth temperature for this structure is 410°C, with peak 2DEG electron mobility and density values of μ = 221000 cm2/V s and n = 1.36 × 1011 cm−2 at 1.5 K. This electron mobility is equal to the highest previously published for these undoped structures but with a factor of 2 reduction in n. This has been achieved through the use of a ...


Gold Nanorods Mediate Tumor Cell Death By Compromising Membrane Integrity, Ling Tong, Yan Zhao, Terry B. Huff, Matthew N. Hansen, Alexander Wei, Ji-Xin Cheng Oct 2007

Gold Nanorods Mediate Tumor Cell Death By Compromising Membrane Integrity, Ling Tong, Yan Zhao, Terry B. Huff, Matthew N. Hansen, Alexander Wei, Ji-Xin Cheng

Other Nanotechnology Publications

Folate-conjugated gold nanorods targeted to tumor cell surfaces produced severe membrane damage upon near-infrared irradiation. Photoinduced injury to the plasma membrane resulted in a rapid increase in intracellular calcium (shown in green) with subsequent disruption of the actin network, featured prominently by the formation of membrane blebs.


Quantum Dot Resonant Tunneling Diodes For Telecom Wavelength Single Photon Detection, H. W. Li, Paul J. Simmonds, H. E. Beere, B. E. Kardynał, D. A. Ritchie, A. J. Shields Sep 2007

Quantum Dot Resonant Tunneling Diodes For Telecom Wavelength Single Photon Detection, H. W. Li, Paul J. Simmonds, H. E. Beere, B. E. Kardynał, D. A. Ritchie, A. J. Shields

Paul J. Simmonds

Single photon detection was realized at a telecom wavelength with quantum dot resonant tunneling diodes grown on an InP substrate. The structure contains a AlAs/In0.53Ga0.47As/AlAs quantum well with InAs quantum dots grown on the top AlAs barrier. The single photon detection efficiency of the device under 1310 nm illumination was measured to be about 0.35% ± 0.07% with a dark count rate of 1.58×10-6 ns-1. This corresponds to an internal efficiency of 6.3%.


Size Effect In Polymer Nanofibers Under Tension, Xiangfa Wu, Yuris A. Dzenis Aug 2007

Size Effect In Polymer Nanofibers Under Tension, Xiangfa Wu, Yuris A. Dzenis

Faculty Publications from Nebraska Center for Materials and Nanoscience

This article studies the size effect on the elastic behavior of solid and hollow polymer nanofibers (e.g., electrospun nanofibers) subjected to uniaxial tension. A one-dimensional nonlinear elastic tension model is proposed that takes into account the coupling effect of fiber elastic deformation and surface tension. The fiber axial force-displacement and stress-strain relations are obtained in explicit forms. It is shown that, at nanoscale, fiber radius has appreciable effect on the elastic response of polymer nanofibers. With consideration of the fiber radial effect, it is shown that the actual contribution of surface energy of the solid polymer fibers to the ...


Novel Method For Mechanical Characterization Of Polymeric Nanofibers, Mohammad Naraghi, Loannis Chasiotis, Harold Kahn, Yongkui Wen, Yuris A. Dzenis Aug 2007

Novel Method For Mechanical Characterization Of Polymeric Nanofibers, Mohammad Naraghi, Loannis Chasiotis, Harold Kahn, Yongkui Wen, Yuris A. Dzenis

Faculty Publications from Nebraska Center for Materials and Nanoscience

A novel method to perform nanoscale mechanical characterization of highly deformable nanofibers has been developed. A microelectromechanical system (MEMS) test platform with an on-chip leaf-spring load cell that was tuned with the aid of a focused ion beam was built for fiber gripping and force measurement and it was actuated with an external piezoelectric transducer. Submicron scale tensile tests were performed in ambient conditions under an optical microscope. Engineering stresses and strains were obtained directly from images of the MEMS platform, by extracting the relative rigid body displacements of the device components by digital image correlation. The accuracy in determining ...


Quantum Dot Resonant Tunneling Diode For Telecommunication Wavelength Single Photon Detection, H. W. Li, B. E. Kardynał, P. See, A. J. Shields, P. Simmonds, H. E. Beere, D. A. Ritchie Aug 2007

Quantum Dot Resonant Tunneling Diode For Telecommunication Wavelength Single Photon Detection, H. W. Li, B. E. Kardynał, P. See, A. J. Shields, P. Simmonds, H. E. Beere, D. A. Ritchie

Paul J. Simmonds

The authors present a quantum dot (QD) based single photon detector operating at a fiber optic telecommunication wavelength. The detector is based on an AlAs/In0.53Ga0.47As/AlAs double-barrier resonant tunneling diode containing a layer of self-assembled InAs QDs grown on an InP substrate. The device shows an internal efficiency of about 6.3% with a dark count rate of 1.58 × 10−6 ns−1 for 1310 nm photons.


Measurement Of Poisson’S Ratio With Contact-Resonance Atomic Force Microscopy, D.C. Hurley, Joseph A. Turner Aug 2007

Measurement Of Poisson’S Ratio With Contact-Resonance Atomic Force Microscopy, D.C. Hurley, Joseph A. Turner

Faculty Publications from Nebraska Center for Materials and Nanoscience

We describe contact-resonance atomic force microscopy (AFM) methods to quantitatively measure Poisson’s ratio ν or shear modulus G at the same time as Young’s modulus E. In contact-resonance AFM, the frequencies of the cantilever’s resonant vibrations are measured while the tip is in contact with the sample. Simultaneous measurement of flexural and torsional vibrational modes enables E and ν to be determined separately. Analysis methods are presented to relate the contact-resonance frequencies to the tip-sample contact stiffness, which in turn determines the sample’s nanoscale elastic properties. Experimental results are presented for a glass specimen with fused ...


Method To Generate Surfaces With Desired Roughness Parameters, Yilei Zhang, Sriram Sundararajan Jul 2007

Method To Generate Surfaces With Desired Roughness Parameters, Yilei Zhang, Sriram Sundararajan

Mechanical Engineering Publications

A surface engineering method based on the electrostatic deposition of microparticles and dry etching is described and shown to be able to independently tune both amplitude and spatial roughness parameters of the final surface. Statistical models were developed to connect process variables to the amplitude parameters (center line average and root-mean-square) and a spatial parameter (autocorrelation length) of the final surfaces. Process variables include particle coverage, which affects both amplitude and spatial roughness parameters, particle size, which affects only spatial parameters, and etch depth, which affects only amplitude parameters. Correlations between experimental data and model predictions are discussed.


Dielectrophoretically Assembled Polymer Nanowires For Gas Sensing, Yaping Dan, Yanyan Cao, Tom E. Mallouk, A. T. Charlie Johnson, Stephane Evoy Jul 2007

Dielectrophoretically Assembled Polymer Nanowires For Gas Sensing, Yaping Dan, Yanyan Cao, Tom E. Mallouk, A. T. Charlie Johnson, Stephane Evoy

Departmental Papers (ESE)

We measured the electronic properties and gas sensing response of nanowires containing segments of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) that were synthesized using anodic aluminum oxide (AAO) membranes. The nanowires have a “striped” structure of gold-PEDOT/PSS-gold and are typically 8 μm long (1 μm-6 μm-1 μm for each section, respectively) and 220 nm in diameter. Dielectrophoretic assembly was used to position single nanowires on pre-fabricated gold electrodes. A polymer conductivity of 11.5 ± 0.7 S/cm and a contact resistance of 27.6 ± 4 kΩ were inferred from resistance measurements of nanowires of varying length and ...


In Vivo Quantitation Of Rare Circulating Tumor Cells By Multiphoton Intravital Flow Cytometry, Wei He, Haifeng Wang, Lynn C. Hartmann, Ji-Xin Cheng, Phillip S. Low Jul 2007

In Vivo Quantitation Of Rare Circulating Tumor Cells By Multiphoton Intravital Flow Cytometry, Wei He, Haifeng Wang, Lynn C. Hartmann, Ji-Xin Cheng, Phillip S. Low

Other Nanotechnology Publications

Quantitation of circulating tumor cells (CTCs) constitutes an emerging tool for the diagnosis and staging of cancer, assessment of response to therapy, and evaluation of residual disease after surgery. Unfortunately, no existing technology has the sensitivity to measure the low numbers of tumor cells (< 1 CTC per ml of whole blood) that characterize minimal levels of disease. We present a method, intravital flow cytometry, that noninvasively counts rare CTCs in vivo as they flow through the peripheral vasculature. The method involves i.v. injection of a tumor-specific fluorescent ligand followed by multiphoton fluorescence imaging of superficial blood vessels to quantitate the flowing CTCs. Studies in mice with metastatic tumors demonstrate that CTCs can be quantitated weeks before metastatic disease is detected by other means. Analysis of whole blood samples from cancer patients further establishes that human CTCs can be selectively labeled and quantitated when present at approximate to 2 CTCs per ml, opening opportunities for earlier assessment of metastatic disease.


Brillouin-Zone Unfolding Of Perfect Supercells Having Nonequivalent Primitive Cells Illustrated With A Si/Ge Tight-Binding Parameterization, Timothy B. Boykin, Neerav Kharche, Gerhard Klimeck Jul 2007

Brillouin-Zone Unfolding Of Perfect Supercells Having Nonequivalent Primitive Cells Illustrated With A Si/Ge Tight-Binding Parameterization, Timothy B. Boykin, Neerav Kharche, Gerhard Klimeck

Birck and NCN Publications

Numerical calculations of nanostructure electronic properties are often based on a nonprimitive rectangular unit cell, because the rectangular geometry allows for both highly efficient algorithms and ease of debugging while having no drawback in calculating quantum dot energy levels or the one-dimensional energy bands of nanowires. Since general nanostructure programs can also handle superlattices, it is natural to apply them to these structures as well, but here problems arise due to the fact that the rectangular unit cell is generally not the primitive cell of the superlattice, so that the resulting E(k) relations must be unfolded to obtain the ...


Effects Of Magnetostatic Coupling On Stripe Domain Structures In Magnetic Multilayers With Perpendicular Anisotropy, K. Janicka, John D. Burton, Evgeny Y. Tsymbal Jun 2007

Effects Of Magnetostatic Coupling On Stripe Domain Structures In Magnetic Multilayers With Perpendicular Anisotropy, K. Janicka, John D. Burton, Evgeny Y. Tsymbal

Faculty Publications from Nebraska Center for Materials and Nanoscience

We investigate the effects of magnetostatic interlayer coupling on the formation of magnetic domains in exchange-coupled ferromagnetic films exhibiting perpendicular magnetic anisotropy. Using simple models for the stripe domain structures we investigate how the magnetostatic interlayer interaction affects the domain size. For antiferromagnetically exchange-coupled multilayers, we show that there is a domain overlap due to the magnetostatic interaction which exists only above a critical thickness and below a critical separation between the ferromagnetic films where it is scaled inversely proportional to the antiferromagnetic exchange coupling constant. We show that the magnetostatic coupling is responsible for the periodic “tiger tail” domain ...


Physics Of Ultrathin-Body Silicon-On-Insulator Schottky-Barrier Field-Effect Transistors, Joachim Knoch, M Zhang, Joerg Appenzeller, S Mantl Jun 2007

Physics Of Ultrathin-Body Silicon-On-Insulator Schottky-Barrier Field-Effect Transistors, Joachim Knoch, M Zhang, Joerg Appenzeller, S Mantl

Other Nanotechnology Publications

In this article we give an overview over the physical mechanisms involved in the electronic transport in ultrathin-body SOI Schottky-barrier MOSFETs. A strong impact of the SOI and gate oxide thickness on the transistor characteristics is found and explained using experimental as well as simulated data. We elaborate on the influence of scattering in the channel and show that for a significant barrier the on-state current is insensitive to scattering once the mean free path for scattering is larger than a characteristic length scale. In addition, recent efforts to lower the Schottky barrier at the source/drain channel interfaces are ...


Understanding Coulomb Effects In Nanoscale Schottky-Barrier-Fets, Klaus M. Indlekofer, Joachim Knoch, Joerg Appenzeller Jun 2007

Understanding Coulomb Effects In Nanoscale Schottky-Barrier-Fets, Klaus M. Indlekofer, Joachim Knoch, Joerg Appenzeller

Other Nanotechnology Publications

We employ a novel multiconfigurational self-consistent Green's function approach (MCSCG) for the simulation of nanoscale Schottky-barrier-field-effect transistors (SB-FETs). This approach allows the calculation of electronic transport with a seamless transition from the single-electron regime to room-temperature FET operation. The particular improvement of the MCSCG stems from a self-consistent division of the channel system into a small subsystem of resonantly trapped states for which a many-body Fock space approach becomes numerically feasible and the rest of the system which can be treated adequately on a conventional mean-field level. The Fock space description allows for the calculation of few-electron Coulomb charging ...


Anisotropic Strain And Phonon Deformation Potentials In Gan, V. Darakchieva, T. Paskova, Mathias Schubert, H. Arwin, P.P. Paskov, B. Monemar, D. Hommel, M. Heuken, J. Off, F. Scholz, B.A. Haskell, P.T. Fini, J.S. Speck, S. Nakamura May 2007

Anisotropic Strain And Phonon Deformation Potentials In Gan, V. Darakchieva, T. Paskova, Mathias Schubert, H. Arwin, P.P. Paskov, B. Monemar, D. Hommel, M. Heuken, J. Off, F. Scholz, B.A. Haskell, P.T. Fini, J.S. Speck, S. Nakamura

Faculty Publications from Nebraska Center for Materials and Nanoscience

We report optical phonon frequency studies in anisotropically strained c-plane- and a-plane-oriented GaN films by generalized infrared spectroscopic ellipsometry and Raman scattering spectroscopy. The anisotropic strain in the films is obtained from high-resolution x-ray diffraction measurements. Experimental evidence for splitting of the GaN E1(TO), E1(LO), and E2 phonons under anisotropic strain in the basal plane is presented, and their phonon deformation potentials cE1(TO) , cE1(LO) , and cE2 are determined. A distinct correlation between anisotropic strain and the A1(TO) and E1(LO) frequencies of ...


1/F Noise In Carbon Nanotube Devices - On The Impact Of Contacts And Device Geometry, Joerg Appenzeller, Yu-Ming Lin, Joachim Knoch, Zhihong Chen, Phaedon Avouris May 2007

1/F Noise In Carbon Nanotube Devices - On The Impact Of Contacts And Device Geometry, Joerg Appenzeller, Yu-Ming Lin, Joachim Knoch, Zhihong Chen, Phaedon Avouris

Other Nanotechnology Publications

We report on the 1/f noise in various ballistic carbon nanotube devices. A common means to characterize the quality of a transistor in terms of noise is to evaluate the ratio of the noise amplitude A and the sample resistance R. By contacting semiconducting tubes with different metal electrodes we are able to show that a small A/R value by itself is no indication of a suitable metal/tube combination for logic applications. We discuss how current in a nanotube transistor is determined by the injection of carriers at the electrode/nanotube interface, while at the same time ...


Atomic Force Microscope Imaging Of Dna And Multi Walled Carbon Nanotubes, Jacob Hohnbaum May 2007

Atomic Force Microscope Imaging Of Dna And Multi Walled Carbon Nanotubes, Jacob Hohnbaum

Mechanical Engineering Undergraduate Honors Theses

The Micro and Nano System Laboratory at the University of Arkansas currently is equipped with an Atomic Force Microscope (AFM). This device can be used to measure objects with resolution on the nanometer scale, but there are a number of technical difficulties in performing scans of carbon nanotubes and DNA. The goal of this research is to successfully perform scans on both carbon nanotubes and DNA and to also establish laboratory processing protocols to re-perform such scans in the future. Previous works performed by other researchers in the laboratory provided basic protocols with which to begin the present research. These ...


Growth By Molecular Beam Epitaxy Of Self-Assembled Inas Quantum Dots On Inalas And Ingaas Lattice-Matched To Inp, Paul J. Simmonds, H W. Li, H E. Beere, P See, A J. Shields, D A. Ritchie Apr 2007

Growth By Molecular Beam Epitaxy Of Self-Assembled Inas Quantum Dots On Inalas And Ingaas Lattice-Matched To Inp, Paul J. Simmonds, H W. Li, H E. Beere, P See, A J. Shields, D A. Ritchie

Paul J. Simmonds

The authors report the results of a detailed study of the effect of growth conditions, for molecular beam epitaxy, on the structural and optical properties of self-assembled InAs quantum dots (QDs) on In0.524Al0.476As. InAs QDs both buried in, and on top of, In0.524Al0.476As were analyzed using photoluminescence (PL) and atomic force microscopy. InAs QD morphology and peak PL emission wavelength both scale linearly with deposition thickness in monolayers (MLs). InAs deposition thickness can be used to tune QD PL wavelength by 170 nm/ML, over a range of ...


Interface Proximity Effects In Current-Perpendicular-To-Plane Magnetoresistance, R.J. Baxter, David G. Pettifor, Evgeny Y. Tsymbal Apr 2007

Interface Proximity Effects In Current-Perpendicular-To-Plane Magnetoresistance, R.J. Baxter, David G. Pettifor, Evgeny Y. Tsymbal

Faculty Publications from Nebraska Center for Materials and Nanoscience

Using a tight-binding model that takes into account a realistic electronic band structure and includes defect scattering we investigate spin-dependent transport in Co/Cu/Co trilayers when current flows perpendicular to the plane. We show that resistance of the Co/Cu interface depends on the proximity of another interface, which makes the parameters characterizing the spin-dependent interface resistance ARF/N* and γF/N, to be dependent on the layer thickness separating the two interfaces. This leads to a decrease in the measurable quantity SR=√(ARAP)(ARAP-ARP) with the Cu layer thickness and, therefore, to ...


Elasticity Of Planar Fiber Networks, X.-F. Wu, Yuris A. Dzenis Apr 2007

Elasticity Of Planar Fiber Networks, X.-F. Wu, Yuris A. Dzenis

Faculty Publications from Nebraska Center for Materials and Nanoscience

A micromechanics model is proposed for the elasticity of planar fiber networks (FNs). The FN is created by random deposition of linearly elastic straight rods within a region. The rods are bonded rigidly at contacts. Under external in-plane loading, the FN deformation consists of fiber bending, elongation, and contraction. An effective constitutive relation for fiber network is developed by averaging the strain energy dissipated by all possible fiber deformations in all directions. Numerical calculations are performed to analyze the effects of fiber aspect ratio and fiber concentration on the effective stiffness of the planar random FN. Finite element analysis (FEA ...


Guided Self-Assembly Of Diblock Copolymer Thin Films On Chemically Patterned Substrates, Xiang-Fa Wu, Yuris A. Dzenis Apr 2007

Guided Self-Assembly Of Diblock Copolymer Thin Films On Chemically Patterned Substrates, Xiang-Fa Wu, Yuris A. Dzenis

Faculty Publications from Nebraska Center for Materials and Nanoscience

We study the guided self-assembly of symmetric/asymmetric diblock copolymer (BCP) films on heterogeneous substrates with chemically patterned surface by using a coarse-grained phase-separation model. During the procedure, the free energy employed for the BCP films was modeled by the Ginzburg-Landau free energy with nonlocal interaction, and the flat, chemically patterned surface was considered as a heterogeneous surface with short-range interaction with the BCP molecules. The resulting Cahn-Hilliard equation was solved by means of an efficient semi-implicit Fourier-spectral algorithm. Effects of pattern scale, surface chemical potential, and BCP asymmetry on the self-assembly process were explored in detail and compared with ...


Interfaces, Volume 9, Issue 1 - Spring 2007 Apr 2007

Interfaces, Volume 9, Issue 1 - Spring 2007

INTERFACES: The Newsletter of the Nebraska Center for Materials and Nanoscience

CONTENTS
From the Director
Facility Focus: Crystallography
Recent Achievements of Center Researchers
Catalysts For Carbon Monoxide Conversion
NCMN Welcomes Li Tan
Research Spotlight: Christian Binek
LNK Chemsolutions Receives Funding


Effect Of Ferroelectricity On Electron Transport In Pt/Batio3/Pt Tunnel Junctions, Julian P. Velev, Chun-Gang Duan, Kirill D. Belashchenko, Sitaram Jaswal, Evgeny Y. Tsymbal Mar 2007

Effect Of Ferroelectricity On Electron Transport In Pt/Batio3/Pt Tunnel Junctions, Julian P. Velev, Chun-Gang Duan, Kirill D. Belashchenko, Sitaram Jaswal, Evgeny Y. Tsymbal

Faculty Publications from Nebraska Center for Materials and Nanoscience

Based on first-principles calculations, we demonstrate the impact of the electric polarization on electron transport in ferroelectric tunnel junctions (FTJs). Using a Pt/BaTiO3 /Pt FTJ as a model system, we show that the polarization of the BaTiO3 barrier leads to a substantial drop in the tunneling conductance due to changes in the electronic structure driven by ferroelectric displacements. We find a sizable change in the transmission probability across the Pt/BaTiO3 interface with polarization reversal, a signature of the electroresistance effect. These results reveal exciting prospects that FTJs offer as resistive switches in nanoscale electronic devices.


Calculations Of Spin-Disorder Resistivity From First Principles, Aleksander L. Wysocki, Kirill D. Belashchenko, Julian P. Velev, Mark Van Schilfgaarde Mar 2007

Calculations Of Spin-Disorder Resistivity From First Principles, Aleksander L. Wysocki, Kirill D. Belashchenko, Julian P. Velev, Mark Van Schilfgaarde

Faculty Publications from Nebraska Center for Materials and Nanoscience

Spin-disorder resistivity of Fe and Ni is studied using the noncollinear density functional theory. The Landauer conductance is averaged over random disorder configurations and fitted to Ohm’s law. The distribution function is approximated by the mean-field theory. The dependence of spin-disorder resistivity on magnetization in Fe is found to be in excellent agreement with the results for the isotropic s-d model. In the fully disordered state, spin-disorder resistivity for Fe is close to experiment, while for fcc Ni it exceeds the experimental value by a factor of 2.3. This result indicates strong magnetic short-range order in Ni ...


Determination Of Young’S Modulus Of Individual Electrospun Nanofibers, Philip A. Yuya, Yongkui Wen, Joseph A. Turner, Yuris A. Dzenis, Zheng Li Mar 2007

Determination Of Young’S Modulus Of Individual Electrospun Nanofibers, Philip A. Yuya, Yongkui Wen, Joseph A. Turner, Yuris A. Dzenis, Zheng Li

Faculty Publications from Nebraska Center for Materials and Nanoscience

The authors report a technique for measuring Young’s modulus of a single electrospun nanofiber using the vibrations of two microcantilevers coupled with the nanofiber. The modulus is calculated from the resonant frequency shift resulting from the nanofiber. Polyacrylonitrile nanofibers (200 nm diameter) were collected during electrospinning and wrapped on two similar microcantilevers causing a shift in first resonance from 10.0 to 19.4 kHz. Finite element analysis was used to analyze the frequency shift using images from a scanning electron microscope giving a modulus of the as-spun polyacrylonitrile nanofiber of 26.8 GPa.


Improved Carrier Injection In Ultrathin-Body Soi Schottky-Barrier Mosfets, M Zhang, Joachim Knoch, Joerg Appenzeller, S Mantl Mar 2007

Improved Carrier Injection In Ultrathin-Body Soi Schottky-Barrier Mosfets, M Zhang, Joachim Knoch, Joerg Appenzeller, S Mantl

Other Nanotechnology Publications

The impact of the gate oxide and the silicon-on-insulator (SOI) body thickness on the electrical performance of SOI Schottky-barrier (SB) MOSFETs with fully nickel silicided source and drain contacts is experimentally investigated. The subthreshold swing S is extracted from the experimental data and serves as a measure for the carrier injection through the Sills. It is shown that decreasing the gate oxide and body thickness allows to strongly increase the carrier injection and hence, a significantly improved ON-state of SB-MOSFETs can be obtained.


Accessibility Of Home Blood Pressure Monitors For Blind And Visually Impaired People, Mark M. Uslan, Darren M. Burton, Thomas E. Wilson, Steven Taylor, Bruce S. Chertow, Jack E. Terry Mar 2007

Accessibility Of Home Blood Pressure Monitors For Blind And Visually Impaired People, Mark M. Uslan, Darren M. Burton, Thomas E. Wilson, Steven Taylor, Bruce S. Chertow, Jack E. Terry

Physics Faculty Research

Background: The prevalence of hypertension comorbid with diabetes is a significant health care issue. Use of the home blood pressure monitor (HBPM) for aiding in the control of hypertension is noteworthy because of benefits that accrue from following a home measurement regimen. To be usable by blind and visually impaired patients, HBPMs must have speech output to convey all screen information, an easily readable visual display, identifiable controls that are easy to use, and an accessible user manual.

Methods: Data on the physical aspects and the features and functions of nine Food and Drug Administration-approved HBPMs (eight of which were ...