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Displaying 76 - 100 of 200

Low-frequency noise in gallium nitride nanowire mechanical resonators

December 7, 2012
Author(s)
Jason Gray, Kristine A. Bertness, Norman Sanford, Charles T. Rogers
We report on the low-frequency 1/f (flicker) parameter noise displayed by the resonance frequency and resistance of doubly clamped c-axis gallium nitride nanowire (NW) mechanical resonators. The resonators are electrostatically driven and their mechanical

Noncontact measurement of charge carrier lifetime and mobility in GaN nanowires

August 27, 2012
Author(s)
Christopher M. Dodson, Patrick Parkinson, Kristine A. Bertness, Hannah J. Joyce, Laura M. Herz, Norman Sanford, Michael B. Johnston
The first noncontact photoconductivity measurements of gallium nitride nanowires (NWs) are presented, revealing a high crystallographic and optoelectronic quality achieved by use of catalyst-free molecular beam epitaxy. In comparison with bulk material

Determination of graphene work function and graphene-insulator-semiconductor band alignment by internal photoemission spectroscopy

July 11, 2012
Author(s)
Rusen Yan, Qin Zhang, Wei Li, Irene G. Calizo, Tian T. Shen, Curt A. Richter, Angela R. Hight Walker, Xuelei X. Liang, David J. Gundlach, Nhan Van Nguyen, Huili G. Xing, Alan Seabaugh
We determined the band alignment of a graphene-oxide-silicon structure using internal photoemission spectroscopy. From the flatband voltage and Dirac voltage we infer a 4.3  10e11 cm-2 negative extrinsic charge present on the graphene surface. Also, we

Comb-assisted swept laser spectroscopy with a mode-hop free tunable external cavity QCL

May 1, 2012
Author(s)
Kevin O. Knabe, Fabrizio R. Giorgetta, Nathan R. Newbury, Chris Armacost, Michael Radunsky, Sam Crivello, Timothy Day, Paul A. Williams
We demonstrate sub-MHz spectral resolution of N 2O absorption spectra acquired with a swept external-cavity quantum cascade laser (QCL) over 0.87 THz. The QCL frequency is monitored by sum -frequency generation with an optical fiber frequency comb.

Optical fiber-coupled cryogenic radiometer with carbon nanotube absorber

April 1, 2012
Author(s)
David J. Livigni, Nathan A. Tomlin, Christopher L. Cromer, John H. Lehman
A cryogenic radiometer was constructed for direct-substitution optical fiber power measurements. The cavity is intended to operate at the 3 K temperature stage of a dilution refrigerator or 4.2 K stage of a liquid cryostat. The optical fiber is removable

Broad bandwidth trace gas and standoff detection with infrared frequency comb sources

March 11, 2012
Author(s)
Nathan R. Newbury, Alexander M. Zolot, Esther Baumann, Fabrizio R. Giorgetta, Florian B. Adler, Ian R. Coddington, Kevin O. Knabe, Lora L. Nugent-Glandorf, Paul A. Williams, Scott A. Diddams, Tyler W. Neely
An optical frequency comb based on the output of a mode-locked femtosecond laser can be used in spectroscopic studies and sensing applications. The broad array of frequency modes simultaneously provides high spectral resolution and broad wavelength

Catalyst-free GaN Nanowires as Nanoscale Light Emitters

March 1, 2012
Author(s)
Kristine A. Bertness, Norman A. Sanford, John B. Schlager, Alexana Roshko, Todd E. Harvey, Paul T. Blanchard, Matthew D. Brubaker, Andrew M. Herrero, Aric W. Sanders
Catalyst-free growth of GaN nanowires with molecular beam epitaxy produces material of exceptionally high quality with long minority carrier lifetimes and low surface recombination velocity. The nanowires grow by thermodynamic driving forces that enhance

Enhanced coupling between light and surface plasmons by nanostructured Fabry-Perot resonator

September 26, 2011
Author(s)
Brian S. Dennis, Vladimir Aksyuk, Michael Haftel, Stefan T. Koev, Girsh Blumberg
It is recognized that surface plasmons (SPs),which can be present on particulate, smooth, or corrugated metallic surfaces, have enormous potential in the fields of novel nano-optical and opto-electronic devices, as well as in spectroscopic, biological, and

Terahertz metrology and instrumentation

August 29, 2011
Author(s)
Erich N. Grossman, Zoya Popovic
This paper gives an overview of measurement techniques used in the THz region of the electromagnetic spectrum, from about 100 GHz to several THz. Currently available components necessary for THz metrology, such as sources, detectors and passives, are

Catalyst-free GaN nanowire growth and optoelectronic characterization

August 19, 2011
Author(s)
Kristine A. Bertness, Norman A. Sanford, John B. Schlager
We discuss the present state-of-the-art concerning the growth mechanism, optical luminescence and electrical properties for GaN nanowires grown with catalyst-free molecular beam epitaxy. These nanowires are essentially defect-free and display long

Gallium nitride nanowire electromechanical resonators with piezoresistive readout

August 11, 2011
Author(s)
Kristine A. Bertness, Jason M. Gray, Norman A. Sanford, Charles T. Rogers
We report on the fabrication, piezoresistive readout, and frequency response of doubly-clamped c-axis gallium nitride (GaN) nanowire (NW) resonators that show mechanical quality factors exceeding 10,000. The devices are fabricated using a combination of

ALD for reliable nanowire self-assembly on microfabricated electrodes

August 10, 2011
Author(s)
Joseph J. Brown, Kristine A. Bertness, Alicia I. Baca, Bright M. Victor
The use of ALD TiO 2 surface coating improves dielectrophoretic assembly yield of individual GaN nanowires on micro-fabricated structures by as much as 67%. With titanium dioxide coating, individual nanowires were placed across suspended electrode pairs in

Microwave near-field probes for photovoltaic applications

June 19, 2011
Author(s)
Joel C. Weber
The photoresponse of three different photovoltaic Cu(In, Ga)Se 2 (CIGS) samples as well as GaAs and silicon bulk samples is measured using near-field scanning microwave microscopy (NSMM). Modeling predicts light-dependent conductivity values for bulk

A general approach to low noise readout of terahertz imaging arrays

June 16, 2011
Author(s)
Erich N. Grossman, Jonathan D. Chisum, Zoya Popovic
This article describes the theory and design of an ultra-low noise electronic readout circuit for use with room temperature video-rate terahertz imaging arrays. First, the noise characteristics of various imaging detectors, including low resistance

Comparison of absolute measurements of laser power using next generation NIST high power radiometer and Air Force high power calorimeter

June 8, 2011
Author(s)
Marla L. Dowell, Christopher L. Cromer, Xiaoyu X. Li, John Bagford, Dan Seibert, John Eric, David Cooper, Steven Comisford, Ernie Cromwell, Richard Bowling
We report comparisons of laser power measurements between the new NIST radiometer, also known as the BB Prime, and the current Air Force standards, known as the BB calorimeter. [1] These measurements were performed using high power laser sources in the Air

Spatial dependence of output pulse delay in a niobium nitride nanowire superconducting single-photon detector

May 16, 2011
Author(s)
Sae Woo Nam, J. A. O'Connor, Michael Tanner, C. M. Natarajan, G. S. Buller, R. J. Warburton, S Miki, Z. Wang, Robert Hadfield
We report on the position-dependent variation in output pulse timing across a superconducting single- photon detector. Our device consists of a single niobium nitride nanowire meander (100 nm width, 4 nm film thickness, 2 mm length). We use a confocal

Dual-wavelength transfer standard for laser peak-power measurement

May 9, 2011
Author(s)
Rodney W. Leonhardt, Daniel King
The National Institute of Standards and Technology (NIST) and the Naval Surface Warfare Center – Corona Division (NSWC) have jointly developed a low-level peak-power radiometer (D-ESR) which functions as a transfer standard for measuring laser pulses at

Spectroscopy with a coherent dual frequency comb interferometer at 3.4 mm

August 1, 2010
Author(s)
Esther Baumann, Fabrizio R. Giorgetta, Ian R. Coddington, William C. Swann, Nathan R. Newbury
A coherent dual fiber-comb spectrometer centered at 1.5 µm wavelengths is transferred to 3.4 µm by difference-frequency generation with a 1064 nm cw laser. It is shown that the residual linewidth between the comb teeth at 3.4 µm is resolution-limited to

Calibration service for instruments that measure laser beam diameter

July 1, 2010
Author(s)
Shao Yang
This document describes the calibration service for instruments that measure laser beam diameter. An overview of the measurement procedures, measurement system, and uncertainty analysis is presented. A sample measurement report is included in this document
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