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Search Publications by: Norman A. Sanford (Fed)

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Displaying 76 - 100 of 319

On the Field Evaporation Behavior of c-axis GaN Nanowires in Laser-Pulsed Atom Probe Tomography

June 26, 2013
Author(s)
Matthew D. Brubaker, Kristine A. Bertness, Norman A. Sanford, Brian Gorman, David R. Diercks, R Kirchofer
GaN has seen use in many applications such as photovoltaics, blue and ultraviolet lasers, and light-emitting diodes with additional research into expanded and new applications. GaN in the form of nanowires present additional possibilities due to their high

Radio-Frequency and DC Electrical Characterization on a Modular MEMS Mechanical Test Platform for Nanomaterials

June 16, 2013
Author(s)
J. J. Brown, Thomas Mitchell (Mitch) Wallis, Pavel Kabos, Kristine A. Bertness, Norman Sanford, Victor Bright
In order to enable radio frequency (RF) data collection from a micromechanical system designed to strain nanomaterials, a coplanar electrical waveguide has been integrated with an actuated microscale stage. RF (100 MHz to 20 GHz) admittance measurements

Studies of photoconductivity and FET behavior in examining drift mobility, surface depletion, and transient effects in Si-doped GaN nanowires examined in vacuum and air

May 3, 2013
Author(s)
Norman A. Sanford, Lawrence H. Robins, Paul T. Blanchard, K. Soria, B. Klein, Kristine A. Bertness, John B. Schlager, Aric W. Sanders
Variable intensity photoconductivity (PC) performed under vacuum at 325 nm was used to estimate drift mobility and negative surface charge density sigma for c-axis oriented Si-doped GaN nanowires (NWs). In this approach we assumed that sigma was

Spatially-Resolved Dopant Characterization with a Scanning Microwave Microscope

March 25, 2013
Author(s)
Thomas M. Wallis, Atif A. Imtiaz, Alexandra E. Curtin, Pavel Kabos, Matthew D. Brubaker, Norman A. Sanford, Kristine A. Bertness
The scanning microwave microscope (SMM) is a tool for spatially-resolved microwave characterization of nanoelectronic materials and devices. The microscope incorporates a sharp, near-field probe, which measures local changes in reflected microwave signals

Gallium Nitride Nanowires for On-Chip Optical Interconnects on Ex-Situ Substrates

January 16, 2013
Author(s)
Matthew D. Brubaker, Paul T. Blanchard, John B. Schlager, Aric W. Sanders, Alexana Roshko, Shannon M. Duff, Jason Gray, Victor M. Bright, Norman A. Sanford, Kristine A. Bertness
In this letter we report on the fabrication, device characteristics, and optical coupling of a two-nanowire device comprising light-emitting diode and photoconductive GaN nanowires. Axial p-n junction GaN nanowires were grown by molecular beam epitaxy

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

Temperature-dependent mechanical-resonance frequencies and damping in ensembles of gallium nitride nanowires

October 22, 2012
Author(s)
Kristine A. Bertness, Norman A. Sanford, J. R. Montague, H.S. Park, Victor M. Bright, Charles T. Rogers
We have measured singly clamped cantilever mechanical-resonances in ensembles of as-grown gallium nitridenanowires (GaN NWs), from 12 K to 320 K. Resonance frequencies are approximately linearly dependent on temperature near 300 K with relative shifts of

Optimization of Dispersion and Surface Pretreatment for Single GaN Nanowire Devices

September 28, 2012
Author(s)
Norman A. Sanford, Kristine A. Bertness, Andrew M. Herrero
The correlation of residual contamination with void formation at the contact/SiO2 interface for single GaN NW devices was investigated. The morphology at the metal/SiO2 interface was observed by removing the annealed Ni/Au films from the SiO2 with carbon

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

Microwave Measurements and Systematic Circuit-Model Extraction of Nanowire Metal Semiconductor Field Effect Transistors

August 24, 2012
Author(s)
Dazhen Gu, Thomas M. Wallis, Pavel Kabos, Paul T. Blanchard, Kristine A. Bertness, Norman A. Sanford
We present detailed on-wafer scattering parameter measurements and equivalent circuit modeling of metal semiconductor field effect transistor (MESFET) that incorporates a GaN nanowire (NW). A systematic procedure is established to extract intrinsic model

Microwave measurements and systematic circuit-model extraction of nanowire metal semiconductor field-effect transistors

August 24, 2012
Author(s)
Dazhen Gu, Thomas M. Wallis, Pavel Kabos, Paul T. Blanchard, Kristine A. Bertness, Norman A. Sanford
We present detailed on-wafer scattering parameter measurements and equivalent circuit modeling of metal semiconductor field effect transistor (MESFET) that incorporates a GaN nanowire (NW). A systematic procedure is established to extract intrinsic model

Microstructure evolution and development of annealed Ni/Au contacts to GaN nanowires

August 21, 2012
Author(s)
Andrew M. Herrero, Paul T. Blanchard, Aric W. Sanders, Matthew D. Brubaker, Norman A. Sanford, Alexana Roshko, Kristine A. Bertness
The development of Ni/Au contacts to Mg-doped GaN nanowires (NWs) is examined. Current-voltage (I-V) measurements of these Mg-doped nanowire devices frequently exhibit a strong degradation after annealing in N 2/O 2. This degradation originates from the

Photoluminescence Polarization in Strained GaN/AlGaN Core/Shell Nanowires

August 17, 2012
Author(s)
G. Jacopin, L. Rigutti, S. Bellei, P. Lavenus, F. H. Julien, Albert Davydov, Denis Tsvetkov, Kristine A. Bertness, Norman Sanford, John B. Schlager, M. Tchemycheva
The polarization properties of GaN/AlGaN core/shell nanowire (NW) heterostructures have been investigated using polarization resolved micro-photoluminescence (µ-PL) and interpreted in terms of a strain dependent 6x6 k.p theoretical model. The NW