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Search Publications by: Kris A. Bertness (Fed)

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Displaying 76 - 100 of 178

Homoepitaxial n-core: p-shell gallium nitride nanowires: HVPE overgrowth growth on MBE nanowires

October 25, 2011
Author(s)
Aric Sanders, Paul T. Blanchard, Kristine A. Bertness, Matthew D. Brubaker, Ann Chiaramonti Debay, Christopher M. Dodson, Todd E. Harvey, Andrew M. Herrero, Devin M. Rourke, John B. Schlager, Norman Sanford, Albert Davydov, Abhishek Motayed, Denis Tsvetkov
We present the homoepitaxial growth of p-type, magnesium-doped gallium nitride shells using halide vapor phase epitaxy on n-type gallium nitride nanowires grown by plasma-assisted molecular beam epitaxy. Scanning electron microscopy shows clear dopant

Abstract of the presentation: Position- and polarization- resolved microphotoluminescence of GaN/AlGaN core-shell nanowires

October 17, 2011
Author(s)
Albert Davydov, G. Jacopin, S. Bellei, Denis Tsvetkov, Kristine A. Bertness, L. Rigutti, Norman A. Sanford, John B. Schlager, M. Tchernycheva, F. H. Julien
Over the past decade, core-shell nanowires (NWs) have been intensively used as the building blocks of novel optoelectronic devices as solar cells [1], LEds [2], naolasers [3]. Indeed, this geometry not only allows to passivate surface states, but also

Effect of AlN Buffer Layer Properties on the Morphology and Polarity of GaN Nanowires Grown by Molecular Beam Epitaxy

September 8, 2011
Author(s)
Matthew D. Brubaker, Kristine A. Bertness, Norman A. Sanford, Albert Davydov, Igor Levin, Devin M. Rourke, Victor M. Bright
Low temperature AlN buffer layers grown by plasma-assisted Molecular Beam Epitaxy (MBE) on Si (111) were found to significantly affect the subsequent growth morphology of GaN nanowires. The AlN buffer layers exhibited nanowire-like columnar protrusions

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

GaN Nanowires Grown by Molecular Beam Epitaxy

August 1, 2011
Author(s)
Kristine A. Bertness, Norman A. Sanford, Albert Davydov
The unique properties of GaN nanowires grown by molecular beam epitaxy are reviewed. These properties include the absence of residual strain, exclusion of most extended defects, long photoluminescence lifetime, low surface recombination velocity,and high

Highly Selective GaN-nanowire/TiO2-nanocluser Hybrid Sensors for Detection of Benzene and Related Environment Pollutants

July 22, 2011
Author(s)
Geetha G. Aluri, Abhishek Motayed, Albert Davydov, Vladimir Oleshko, Kristine A. Bertness, Norman Sanford
Nanowire-nanocluster hybrid chemical sensors were realized by functionalizing gallium nitride (GaN) nanowires with titanium dioxide (TiO2) nanoclusters for selectively sensing benzene and other related aromatic compounds. Hybrid sensor devices were

Electrical Characterization of Photoconductive GaN Nanowire Devices from 50 MHz to 33 GHz

July 1, 2011
Author(s)
Thomas M. Wallis, Dazhen Gu, Atif A. Imtiaz, Pavel Kabos, Paul T. Blanchard, Norman A. Sanford, Kristine A. Bertness, Christpher Smith
The electrical response of two-port., photoconductive GaN nanowire devices was measured from 50 MHz to 33 GHz. The admittance of individual contacted nanowires showed an increase on the order of 10% throughout the measured frequency range after exposure to

GaN nanowires grown by molecular beam epitaxy

July 1, 2011
Author(s)
Kristine A. Bertness, Norman A. Sanford, Albert Davydov
The unique properties of GaN nanowires grown by molecular beam epitaxy are reviewed. These properties include defect-free growth mode with no residual strain, long photoluminescence lifetime, low surface recombination velocity and high mechanical quality

Deembedding parasitic elements of GaN nanowire MESFETs by use of microwave measurements

June 3, 2011
Author(s)
Dazhen Gu, Thomas M. Wallis, Paul T. Blanchard, SangHyun S. Lim, Atif A. Imtiaz, Kristine A. Bertness, Norman A. Sanford, Pavel Kabos
We present a deembedding roadmap for extracting parasitic elements of a nanowire (NW) MESFET device from full two-port scattering-parameter measurements in the frequency range from 0.1 GHz to 25 GHz. The NW MESFET is integrated in a microwave coplanar

Three-dimensional imaging of liquid crystal structures and defects by means of holographic manipulation of colloidal nanowires with faceted sidewalls

June 3, 2011
Author(s)
David Engstrom, Martin Persson, Rahul P. Trivedi, Kristine A. Bertness, Mattias Goksor, Ivan I. Smalyukh
We use nanowires with faceted sidewalls for mapping of the patterns of three-dimensional orientational order and defect structures. In chiral nematics, the nanowires follow the local average orientation of rod-shaped molecules. When spatially translated by

Analysis of high-Q, gallium nitride nanowire resonators in response to deposited thin films

January 1, 2011
Author(s)
J. R. Montague, M. Dalberth, J. M. Gray, D. Seghete, Kristine A. Bertness, S M. George, Victor M. Bright, Charles T. Rogers, Norman Sanford
Gallium nitride nanowires (GaN-NWs) are systems of interest for mechanical resonance-based sensors due to their small mass and, in the case of c-axis NWs, high mechanical quality (Q) factors of 10,000-100,000. We report on singly-clamped NW mechanical

Controlled nucleation of GaN nanowires grown with molecular beam epitaxy

July 13, 2010
Author(s)
Kristine A. Bertness, Aric W. Sanders, Devin M. Rourke, Todd E. Harvey, Alexana Roshko, Norman A. Sanford
The location of GaN nanowires was controlled with essentially perfect selectivity using patterned SiNx prior to molecular beam epitaxy growth. Growth was uniform within mask openings and absent on the mask surface for over 95 % of the usable area of a 76

Application of Microwave Scanning Probes to Photovoltaic Materials

June 20, 2010
Author(s)
Kristine A. Bertness, John B. Schlager, Norman A. Sanford, Atif A. Imtiaz, Thomas M. Wallis, Joel C. Weber, Pavel Kabos, Lorelle M. Mansfield
We demonstrate that near field scanning microwave microscopy (NSMM) can be used to detect photoresponse in photovoltaic materials with potential for submicrometer resolution. In this approach, a radio-frequency scanning tunneling microscopy (RF-STM) tip is

High frequency characterization of a Schottky contact to a GaN nanowire bundle

June 16, 2010
Author(s)
Chin J. Chiang, Thomas M. Wallis, Dazhen Gu, Atif A. Imtiaz, Pavel Kabos, Paul T. Blanchard, Kristine A. Bertness, Norman A. Sanford, Kichul Kim, Dejan Filipovic
A GaN nanowire (NW) Schottky contact was characterized up to 10 GHz. Using a calibration procedure and circuit model a capacitance-voltage (CV) curve was obtained, from which a carrier concentration was calculated for the first time. These results

Tensile measurement of single crystal gallium nitride nanowires on MEMS test stages

April 18, 2010
Author(s)
J. J. Brown, A. I. Baca, Kristine A. Bertness, D. A. Dikin, R. S. Ruoff, Victor M. Bright
This paper reports the first direct tensile tests on nearly defect free, n-type (Si-doped) gallium nitride single crystal nanowires. Here, for the first time, nanowires have been integrated with actuated, active microelectromechanical (MEMS) structures

Steady-state and transient photoconductivity in c-axis GaN nanowires grown by nitrogen-plasma-assisted molecular beam epitaxy

February 12, 2010
Author(s)
Norman A. Sanford, Paul T. Blanchard, Kristine A. Bertness, Lorelle Mansfield, John B. Schlager, Aric W. Sanders, Alexana Roshko, Beau Burton, Steven George
Analysis of steady-state and transient photoconductivity measurements at room temperature performed on c-axis oriented GaN nanowires yielded estimates of free carrier concentration, drift, mobility, surface band bending, and surface capture coefficient for

Atomic layer deposition enabled interconnect technology for vertical nanowire array devices

June 20, 2009
Author(s)
Myongjai Lee, Jen-Hau Cheng, Kristine A. Bertness, Norman Sanford, Dragos Seghete, Steven M. George, Y.C. Lee
We have demonstrated an atomic layer deposition (ALD) enabled interconnect technology for vertical, c-axis oriented gallium nitride (GaN) nanowire (NW, 5-10m in length, 80-200nm in diameter) arrays encapsulated by benzocyclobutene (BCB). The nano-scaled