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NIST Authors in Bold

Displaying 31351 - 31375 of 74303

Nanowire placement with ink jet heads

September 16, 2007
Author(s)
Kristine A. Bertness, Christopher M. Dodson, Paul T. Blanchard, Norman Sanford, Ross N. Mills
We show that thermal ink jet printheads can be used to place GaN nanowires on patterned substrates. The semiconductor nanowires have diameters ranging from 70 to 300 nm and lengths from 5 υm to 20 υm. They were dispersed in alcohol-water solutions for

Nucleation and propagation mechanisms for catalyst-free growth of GaN nanowires

September 16, 2007
Author(s)
Kristine A. Bertness, Devin M. Rourke, Alexana Roshko, Lorelle Mansfield, Aric W. Sanders, Todd E. Harvey, Norman A. Sanford
Nucleation of GaN nanowires without catalysts in molecular beam epitaxy is shown to be a distinct process from nanowire propagation. Nanowire growth is relatively insensitive to starting conditions once the nanowire morphology is established, and is driven

Persistent photoconductivity studies of c-axis GaN nanowires grown by MBE

September 16, 2007
Author(s)
Norman Sanford, Paul T. Blanchard, Kristine A. Bertness, Alexana Roshko, Beau Burton, Lorelle Mansfield, John B. Schlager, Steven George, Aric Sanders
Photoconductivity (PC) and persistent photoconductivity (PPC) were measured on c-axis GaN nanowires (NWs) grown by catalyst-free nitrogen plasma assisted MBE on Si(111) substrates. Unintentionally doped n-type NWs from two separate growth batches were

Time-resolved photoluminescence study of GaN nanowires grown by catalyst-free MBE

September 16, 2007
Author(s)
John B. Schlager, Kristine A. Bertness, Paul T. Blanchard, Norman A. Sanford
We report steady-state and time-resolved photoluminescence (PL & TRPL) measurements on individual GaN nanowires that were grown by nitrogen-plasma-assisted, molecular beam epitaxy on Si(111) and subsequently dispersed onto fused quartz substrates for

6th Annual PKI R&D Workshop "Applications-Driven PKI" Proceedings

September 13, 2007
Author(s)
William T. Polk, Kent Seamons
NIST hosted the sixth Annual Public Key Infrastructure (PKI) Research Workshop on April 17-19, 2007. The two and a half day event brought together PKI experts from academia, industry, and government had a particular interest in novel approaches to

Area Measurements of Apertures for Exo-Atmospheric Solar Irradiance for JPL

September 13, 2007
Author(s)
Maritoni A. Litorja, Bettye C. Johnson, J B. Fowler
A comparison of the area measurements of the limiting apertures used for total solar irradiance measurements in the Active Cavity Radiometer Irradiance Monitor II (ACRIM II) and Active Cavity Radiometer Irradiance Monitor III (ACRIM III) were conducted

Manipulation of the Collisional Frequency Shift in Caesium Fountain Clocks

September 13, 2007
Author(s)
K Szymaniec, W Chalupczak, S Weyers, R. Wynands, Eite Tiesinga, Carl J. Williams
The frequency shift due to atomic collisions is a major, and in some cases the dominant, limitation to the accuracy of caesium fountain primary frequency standards. A correction for this shift is usually obtained by measuring the frequency of the standard

SDO EVE CCD and Thin Foil Filter Characterization and Selection

September 13, 2007
Author(s)
Matthew Triplett, David Croster, Thomas N. Woods, Francis Eparvier, Phillip Chamberlin, Gregory D. Berthiaume, David Weitz, Robert E. Vest
The NASA Solar Dynamics Observatory (SDO), scheduled for launch in 2008, incorporates a suite of instruments including the EUV Variability Experiment (EVE). The EVE instrument package contains grating spectrographs used to measure the solar extreme

SDO EVE ESP Radiometric Calibration and Results

September 13, 2007
Author(s)
Leonid Didkovsky, D L. Judge, Seth Wieman, T N. Woods, Phillip Chamberlin, Andrew Jones, Francis Eparvier, Matthew Triplett, Donald Woodraska, D R. McMullin, Mitchell L. Furst, Robert E. Vest
The Solar Dynamics Observatory (SDO) Extreme ultraviolet Solar Photometer (ESP), as a part of the Extreme ultraviolet Variability Experiment (EVE) suite of instruments, was calibrated at the National Institute of Standards and Technology (NIST) on the

Universal behaviour of silica suspensions gelled under shear

September 13, 2007
Author(s)
Howard J. Hanley, Chris Muzny, J Bartlett, E. Drabarek
The shear influenced gelation of three aqueous suspensions consisting of silica particles of nominal diameter 7, 12 and 24 nm, respectively, is reported. It is shown that the viscosity/stress of a gelling system increases with time after gel initiation

A proposed laser frequency comb based wavelength reference for high resolution spectroscopy

September 12, 2007
Author(s)
Steve Osterman, Scott A. Diddams, Matthew Beasley, Cynthia Froning, Leo W. Hollberg, Phillip MacQueen, Vela Mbele, Andrew Weiner
High resolution spectroscopy is the foundation for many of the most challenging and productive of all astronomical observations. A highly precise, repeatable and stable wavelength calibration is especially essential for long term RV observations. The two

Advances in Chip-Scale Atomic Frequency References at NIST

September 12, 2007
Author(s)
Svenja A. Knappe, V Shah, Alan Brannon, Vladislav Gerginov, Hugh Robinson, Z Popovic, Leo W. Hollberg, John E. Kitching
We present new advances in the development of chip-scale atomic frequency references. Coherent population trapping (CPT) resonances usually exhibit contrasts below 10 %, when interrogated with frequency modulated lasers. A relatively simple way to increase

Better Standards, Built Faster

September 12, 2007
Author(s)
Arthur Griesser
Many information transfer standardization efforts focus excessively on minutiae of the transport format (such as XML), to the detriment of the data model. Information standards could be created more expeditiously if the attention lavished on the transport

Biometric Systematic uncertatinty and the User

September 12, 2007
Author(s)
Mary F. Theofanos, Ross J. Micheals, Shahram Orandi, Brian C. Stanton
Often biometric technology and system evaluators are concerned with capturing accurate performance estimates that predict performance for target populations of interest. Occasionally, predictions, and perhaps adjustments, for subpopulations based on

Experimental determination of the inhomogeneous contribution to linewidth in Permalloy films using a time-resolved magneto-optic Kerr effect microprobe

September 12, 2007
Author(s)
Michael Schneider, Thomas Gerrits, Anthony B. Kos, Thomas J. Silva
We adapted a time-resolved magneto-optic microprobe for use with the pulsed inductive microwave magnetometer apparatus, allowing us to measure the magnetization dynamics of a thin Permalloy film at micrometer and millimeter length scales under exactly the

Lattice-based optical clock using an even isotope of Yb

September 12, 2007
Author(s)
Zeb Barber, C Hoyt, Jason Stalnaker, Nathan D. Lemke, Christopher W. Oates, Tara M. Fortier, Scott A. Diddams, Leo W. Hollberg
We describe progress toward an optical lattice clock based on an even isotope of Yb. The 1S_0 - P_0 clock resonance in 174Yb is accessed using a magnetically induced spectroscopic technique. Using ~1 mT static magnetic fields and ~10 uW of probe light

NIST Cesium Fountains - Current Status and Future Prospects

September 12, 2007
Author(s)
Steven R. Jefferts, Thomas P. Heavner, Thomas E. Parker, Jon H. Shirley
We review the current status of the U.S. Primary Frequency Standard, NIST-F1. NIST-F1 is a laser-cooled cesium fountain based frequency standard with an inaccuracy of less than δ f/f {less than or equal to} 5×10 -16 limited mainly by the radiation field in

Optical frequency standards based on mercury and aluminum ions

September 12, 2007
Author(s)
Wayne M. Itano, James C. Bergquist, Anders Brusch, Scott A. Diddams, Tara M. Fortier, Thomas P. Heavner, Leo W. Hollberg, David Hume, Steven R. Jefferts, Luca Lorini, Thomas E. Parker, Till P. Rosenband, Jason Stalnaker
Single-trapped-ion frequency standards based on a 282 nm transition in 199Hg+ and on a 267 nm transition in 27Al+ have been developed at NIST over the past several years. Their frequencies are measured relative to each other and to the NIST primary

Tunable Ionic-Conductivity of Collapsed Sandia Octahedral Molecular Sieves (SOMS)

September 12, 2007
Author(s)
Jason D. Pless, Terry J. Garino, James E. Maslar, Tina M. Nenoff
The structure-property relationship between atomic cation substitution and bulk scale conductivity in perovskites has been studied systematically. A series of Na-Nb perovskites has been synthesized via two methods (1) ion-exchange or (2) synthetic metal

Covalent Attachment of Photoluminescent Silicon Nanoparticles to Streptavidin

September 11, 2007
Author(s)
Jonghoon Choi, Peter Niarhos, Nam S. Wang, Vytas Reipa
We have covalently attached multiple fluorescent silicon nanocrystals (SNs) to streptavidin molecule. Selective conjugation of SNs to a target protein is accomplished using sequential silicon surface termination chemistry. In the first step, freshly
Displaying 31351 - 31375 of 74303