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Search Publications by: Ward L. Johnson (Fed)

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Displaying 26 - 50 of 54

Vibrational modes of GaN nanowires in the gigahertz range

November 13, 2012
Author(s)
Ward L. Johnson, Sudook A. Kim, Roy H. Geiss, Colm Flannery, Kristine A. Bertness, Paul R. Heyliger
Monocrystalline nanowires offer an attractive basis for resonant nanoelectromechanical systems (NEMS) for a variety of applications, including mass and force sensing, and, in each of these applications, there are advantages to operation at frequencies

Thermogravimetric Analysis with a Heated Quartz Crystal Microbalance

August 11, 2012
Author(s)
Ward L. Johnson, Elisabeth Mansfield
Thermogravimetric analysis with an SC-cut quartz crystal microbalance (QCM) were demonstrated at temperatures in the range from 20 C to 450 C. A measurement system was built around a crystal sensor head that was mounted in a small tube furnace. Changes in

A thickness-shear MEMS resonator employing electromechanical transduction through a coplanar waveguide

May 21, 2012
Author(s)
Ward L. Johnson, Thomas M. Wallis, Pavel Kabos, Eduard Rocas, Juan C. Collado Gomez, Li-Anne Liew, Albert Davydov, Alivia Plankis, Paul R. Heyliger
The design, modeling, fabrication, and characterization of a vibrationally trapped thickness-shear MEMS resonator is presented. This device is intended to avoid various limitations of flexural MEMS resonators, including nonlinearity, clamping losses

Contributions to anelasticity in langasite and langatate

December 30, 2011
Author(s)
Ward L. Johnson, Sudook A. Kim, Christine F. Rivenbark, Satoshi Uda
Maximization of the quality factors Q of langasite (LGS) and langatate (LGT) is necessary for optimal performance of acoustic resonators of these materials in frequency-control and high-temperature sensing applications. In this report, measurements and

Effects of shape distortions and imperfections on mode frequencies and collective linewidths in nanomagnets

March 28, 2011
Author(s)
Hans T. Nembach, Justin M. Shaw, Thomas J. Silva, Ward L. Johnson, Sudook A. Kim, Robert D. McMichael, Pavel Kabos
We used Brillouin light scattering to show that shape distortions in Ni80Fe20 nanoelements can have a dramatic effect on the measured linewidth of certain modes. By intentionally introducing an amount of “egg-like” shape distortion to an ideal elliptical

Workshop on Quantitative Tools for Condition Assessment of Aging Infrastructure

October 14, 2010
Author(s)
Ward L. Johnson, Thomas A. Siewert, Jessica Terry, Dat Duthinh, Mark Iadicola, William E. Luecke, Joseph D. McColskey
The Quantitative Tools for Condition Assessment of Aging Infrastructure Workshop was held May 4-5, 2010, in Boulder, Colorado. It was organized by a team of researchers within the National Institute of Standards and Technology s (NIST) Materials Science

Elastic constants and dimensions of imprinted polymeric nanolines determined from Brillouin light scattering

January 18, 2010
Author(s)
Ward L. Johnson, Sudook A. Kim, Roy H. Geiss, Colm Flannery, Paul R. Heyliger, Christopher L. Soles, Wen-Li Wu, Chengqing C. Wang, Christopher M. Stafford, B D. Vogt
Elastic constants and cross-sectional dimensions of imprinted nanolines of poly(methyl methacrylate) (PMMA) on silicon are determined nondestructively from finite-element inversion analysis of dispersion curves of hypersonic acoustic modes of these

Surface-plasmon-enhanced electric fields in two-dimensional arrays of gold nanodisks

August 4, 2008
Author(s)
Ward L. Johnson, Sudook A. Kim, Zhandos Utegulov, B. T. Draine
Electric-field distributions in two-dimensional arrays of gold nanodisks on Si3N4 membranes are modeled, using the discrete-dipole approximation, as a function of nanodisk diameter (20 − 50 nm), height (10 − 100 nm), ratio of the array spacing to diameter

Mode-selective acoustic spectroscopy of trigonal piezoelectric crystals

May 1, 2008
Author(s)
Ward L. Johnson, Carlos F. Martino, Sudook A. Kim, Paul R. Heyliger
A noncontacting electromagnetic-acoustic-resonance technique is presented for generating and detecting vibrational modes with prescribed symmetries in piezoelectric trigonal crystals with cylindrical geometry. This technique provides the experimental basis

Vibrational modes of nanolines

March 5, 2008
Author(s)
Paul R. Heyliger, Colm Flannery, Ward L. Johnson
Brillouin-light-scattering spectra previously have been shown to provide information on acoustic modes of polymeric lines fabricated by nanoimprint lithography. Finite-element methods for modeling such modes are presented here. These methods provide a

Characterization of Magnetic Properties at Edges by Edge Mode Dynamics

April 21, 2006
Author(s)
Brian B. Maranville, Robert McMichael, Sudook A. Kim, Ward L. Johnson, C A. Ross, J Cheng
We have used trapped spinwave or edge modes of magnetic precession to probe the magnetic environment near magnetic film edges magnetized perpendicular to the edge. Micromagnetic models of dynamics in stripes reveal that the edge mode frequency-field

Elastodynamic characterization of imprinted nanolines

April 3, 2006
Author(s)
Ward L. Johnson, Colm Flannery, Sudook A. Kim, Roy H. Geiss, Christopher Soles, Paul R. Heyliger
Experimental techniques employing Brillouin light scattering (BLS) and analytical techniques employing finite-element (FE) and Farnell-Adler models are being developed for characterizing acoustic modes and determining elastic moduli and dimensions of

Acoustic Modes and Elastic Properties of Polymeric Nanostructures

October 21, 2005
Author(s)
R Hartschuh, A Kisliuk, V N. Novikov, Alexei Sokolov, Paul R. Heyliger, Colm Flannery, Ward L. Johnson, Christopher Soles, Wen-Li Wu
Fabricating mechanically robust polymer structures with nanoscale dimensions is critical for a wide range of emerging technologies. The rigidity of such structures is expected to change as the feature sizes approach the characteristic dimensions of the

Acoustic Loss in Langasite and Langanite

March 1, 2004
Author(s)
Ward L. Johnson, K Sudook, U Satoshi
Resonant ultrasonic loss 1/Q in plano-convex unplated Y-cut disks of langasite and langanite were measured as a function of freqeuncy and temperature with the aim of identifying dominant internal mechanisms that will degrade electronic oscillator