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Search Publications by: Kris A. Bertness (Fed)

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Displaying 51 - 75 of 178

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

Selective Streptavidin Bioconjugation on Si and SiC nanowires for Biosensor Applications.

January 14, 2013
Author(s)
Elissa H. Williams, John A. Schreifels, Mulpuri V. Rao, Albert Davydov, Vladimir P. Oleshko, Nancy J. Lin, Kristen L. Steffens, Sergiy Krylyuk, Kristine A. Bertness, Amy Manocchi, Yaroslav Koshka
A functionalization method for the specific and selective immobilization of the streptavidin (SA) protein on semiconductor nanowires (NWs) was developed. Silicon (Si) and silicon carbide (SiC) NWs were functionalized with 3-aminopropyltriethoxysilane

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

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

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

Selective Streptavidin Bioconjugation on Si, SiC, and GaN Nanowires for Biosensor Applications.

October 19, 2012
Author(s)
Elissa H. Williams, John A. Schreifels, Mulpuri V. Rao, Albert Davydov, Vladimir Oleshko, Nancy Lin, Kristen L. Steffens, Sergiy Krylyuk, Kristine A. Bertness, Amy Manocchi, Yaroslav Koshka
A functionalization method for the specific and selective immobilization of the streptavidin (SA) protein on semiconductor nanowires (NWs) was developed. Silicon (Si), silicon carbide (SiC), and gallium nitride (GaN) NWs were functionalized with 3

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

UV-Assisted Alcohol Sensing Using SnO_(2) Functionalized GaN Nanowire Devices

September 1, 2012
Author(s)
Ritu Bajpai, Abhishek Motayed, Albert Davydov, Vladimir Oleshko, Geetha G. Aluri, Kristine A. Bertness, Mulpuri V. Rao, Mona E. Zaghloul
A chemiresistor type sensor for selective alcohol sensing has been realized from gallium nitride nanowires (NWs) functionalized with sputter-deposited tin dioxide nanoparticles. Two-terminal devices were fabricated using standard microfabrication

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

A near-field scanning microwave microscope for characterization of inhomogeneous photovoltaics

August 10, 2012
Author(s)
Joel C. Weber, Kristine A. Bertness, John B. Schlager, Norman A. Sanford, Atif A. Imtiaz, Thomas M. Wallis, Pavel Kabos, Kevin J. Coakley, Victor Bright, Lorelle M. Mansfield
We present a near field scanning microwave microscope (NSMM) optimized for imaging photovoltaic samples. Our system incorporates a cut Pt-Ir tip inserted into an open ended coaxial cable to form a weak resonator, allowing the microwave reflection S11

Sensing Trace Amounts of Nitro-Aromatic Explosives using Nanowire-Nanocluster Hybrids

August 1, 2012
Author(s)
Geetha G. Aluri, Abhishek Motayed, Albert Davydov, Vladimir P. Oleshko, Kristine A. Bertness, Norman A. Sanford
The threat of terrorism and the need for homeland security calls for advanced technologies to detect the concealed explosives safely and efficiently. We demonstrated highly sensitive and selective detection of traces of nitro-aromatic explosive compounds

UV-Assisted Alcohol Sensing with Zinc Oxide Functionalized Gallium Nitride Nanowires

July 1, 2012
Author(s)
Ritu Bajpai, Abhishek Motayed, Albert Davydov, Kristine A. Bertness, Mona E. Zaghloul
Alcohol sensors using gallium nitride (GaN) nanowires (NWs) functionalized with zinc oxide (ZnO) nanoparticles have been demonstrated. These sensors operate at room temperature, are completely recoverable and demonstrate a response and recovery time of the

Anisotropic Field Evaporation of Diatomic Species from Oxides and Nitrides

May 21, 2012
Author(s)
Matthew D. Brubaker, David R. Diercks, R Kirchofer, Kristine A. Bertness, Norman A. Sanford, Brian Gorman
Recent work using laser-assisted atom probe tomography on non-metallic materials has indicated that for many data collection conditions, anisotropic evaporation can occur. In some cases this can be attributed to a high laser energy leading to uneven

Methanol, Ethanol, and Hydrogen Sensing using Metal-Oxide and Metal (TiO subscript 2-Pt) Composite Nanoclusters on GaN Nanowires: A New Route towards Tailoring the Selectivity of Nanowire-Nanocluster based Chemical Sensors.

May 12, 2012
Author(s)
Geetha G. Aluri, Abhishek Motayed, Albert Davydov, Vladimir Oleshko, Kristine A. Bertness, Norman Sanford, Mulpuri V. Rao
We demonstrate a new method for tailoring the selectivity of chemical sensors using nanowires decorated with multicomponent nanoclusters (metal and metal-oxide)-based hybrid sensors. In the present study we demonstrate the change of selectivity of titanium

Unconventional structure-assisted optical manipulation of high-index nanowires in liquid crystals

March 20, 2012
Author(s)
Kristine A. Bertness, David Engstrom, Michael C. Varney, Martin Persson, Rahul P. Trivedi, Mattias Goksor, Ivan I. Smalyukh
Stable optical trapping and manipulation of high-index particles in low-index host media is often impossible due to the dominance of scattering forces over gradient forces. Here we explore optical manipulation in liquid crystalline structured hosts and

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

MOSFETs made from GaN nanowires with fully conformal cylindrical gates

December 2, 2011
Author(s)
Paul T. Blanchard, Kristine A. Bertness, Todd E. Harvey, Aric W. Sanders, Norman A. Sanford, Steven M. George, Dragos Seghete
We report novel metal-oxide-semiconductor field effect transistors (MOSFETs) based on individual gallium nitride (GaN) nanowires with fully conformal cylindrical gates. The W/Al 2O 3 gates were deposited by atomic layer deposition. Reverse-bias breakdown

Capacitive readout technique for studies of dissipation in GaN nanowire mechanical resonators

November 11, 2011
Author(s)
Kristine A. Bertness, Joshua R. Montague, Norman A. Sanford, Victor Bright, Charles T. Rogers
A variable-temperature, homodyne reflectometry measurement technique for detecting nanoscale mechanical motion has recently been developed. We have extended this technique to make the first all-electrical measurements of an ensemble of as-grown, c-axis

Gallium nitride nanowires achieve crystalline perfection

October 25, 2011
Author(s)
Kristine A. Bertness, Norman A. Sanford, John B. Schlager
A new method of growing a common semiconductor provides an avenue for fabricating perfect crystals in a form that takes advantage of their unique optical, electrical, and mechanical properties.