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Search Publications by: Kris A. Bertness (Fed)

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Displaying 26 - 50 of 178

Measurement of the Electrostatic Edge Effect in Wurtzite GaN Nanowires

November 24, 2014
Author(s)
Alex Henning, Benjamin Klein, Kristine A. Bertness, Paul T. Blanchard, Norman Sanford, Yossi Rosenwaks
The electrostatic effect of the hexagonal corner on the electronic structure in wurtzite GaN nanowires (NWs) was directly measured using Kelvin probe force microscopy (KPFM). By correlating electrostatic simulations with the measured potential difference

GaN nanowire coated with atomic layer deposition of tungsten: a probe for near-field scanning microwave microscopy

September 25, 2014
Author(s)
Joel Weber, Paul T. Blanchard, Aric Sanders, Jonas Gertsch, Steven George, Samuel Berweger, Atif A. Imtiaz, Thomas Mitchell (Mitch) Wallis, Kris A. Bertness, Pavel Kabos, Norman A. Sanford, victor bright
We report on the fabrication of a GaN nanowire probe for near-field scanning microwave microscopy. The probe has a capacitive resolution of 0.03 fF, surpassing that of a commercial Pt tip. Imaging of MoS2 sheets found the probe to be immune to surface

Imaging the p-n junction in a gallium nitride nanowire with a scanning microwave microscope

July 2, 2014
Author(s)
Atif A. Imtiaz, Thomas M. Wallis, Joel C. Weber, Kevin J. Coakley, Matthew D. Brubaker, Paul T. Blanchard, Kristine A. Bertness, Norman A. Sanford
We used a broadband, atomic-force-microscope-based, scanning microwave microscope (AFM-SMM) to probe the axial dependence of the depletion in a GaN nanowire (NW) p-n junction structure. The NWs were c-axis oriented and grown by molecular beam epitaxy. The

Influence of morphology on current-voltage behavior of GaN nanowires

July 1, 2014
Author(s)
Paul T. Blanchard, Kristine A. Bertness, Matthew D. Brubaker, Todd E. Harvey, Aric W. Sanders, Norman A. Sanford
We demonstrate the effect that the different morphologies of MBE-grown GaN nanowires (NWs) can have upon current-voltage (I-V) behavior. Two main aspects of NW morphology were investigated. The first aspect was the NW diameter, dNW. For single-crystal Si

Solution-based functionalization of gallium nitride nanowires for protein sensor development

April 17, 2014
Author(s)
Albert Davydov, Elissa H. Williams, Vladimir P. Oleshko, Kristen L. Steffens, Igor Levin, Nancy J. Lin, Kristine A. Bertness, Amy Manocchi, M V. Rao, John A. Schreifels
A solution-based functionalization method for the specific and selective attachment of the streptavidin (SA) protein to gallium nitride (GaN) nanowires (NWs) is presented. By exploiting streptavidin's strong affinity for its ligand biotin, SA

Establishing an upper bound on contact resistivity of ohmic contacts to n-GaN nanowires

April 1, 2014
Author(s)
Paul T. Blanchard, Kristine A. Bertness, Todd E. Harvey, Norman A. Sanford
Contact resistivity ρ c is an important figure of merit in evaluating and improving the performance of electronic and optoelectronic devices. Due to the small size, unique morphology, and uncertain transport properties of semiconductor nanowires (NWs)

Growth and Applications of Single-Nanowire GaN Light Emitting Diodes

March 19, 2014
Author(s)
Kristine A. Bertness
We discuss two applications of single-nanowire GaN light emitting diodes, optical interconnects and multifunction scanning probes. These applications take advantage of the native morphology of nanowires and the high mechanical strength of GaN.

Characterization of InGaN quantum disks in GaN nanowires

March 4, 2014
Author(s)
Alexana Roshko, Roy H. Geiss, John B. Schlager, Matthew D. Brubaker, Kristine A. Bertness, Norman A. Sanford, Todd E. Harvey
Catalyst-free GaN nanowires with InGaN quantum disks (QDs) were characterized by scanning/transmission elec-tron microscopy (S/TEM) and photoluminescence. A va-riety of structures, from QDs with large strain fields to apparently strain free QDs were

Characterization of InGaN quantum disks in GaN nanowires

February 27, 2014
Author(s)
Alexana Roshko, Roy H. Geiss, John B. Schlager, Matthew D. Brubaker, Kristine A. Bertness, Norman A. Sanford, Todd E. Harvey
Catalyst-free GaN nanowires with InGaN quantum disks (QDs) were characterized by scanning/transmission electron microscopy (S/TEM) and photoluminescence. A variety of structures, from QDs with large strain fields to apparently strain free QDs were observed

Laser-assisted atom probe tomography of MBE grown GaN nanowire heterostructures

February 24, 2014
Author(s)
Norman A. Sanford, Paul T. Blanchard, Matthew D. Brubaker, Kristine A. Bertness, John B. Schlager, R Kirchofer, David R. Diercks, Brian Gorman
Laser-assisted atom probe tomography (L-APT) was performed on GaN nanowires (NWs) and axial GaN/InGaN nanowire heterostructures. All samples were grown by MBE on Si(111) substrates. The laser pulse energy (PE) at 355 nm used in L-APT analysis of GaN NWs

In situ temperature measurements for selective epitaxy of GaN nanowires

February 17, 2014
Author(s)
Kristine A. Bertness, Matthew D. Brubaker, Todd E. Harvey, Shannon M. Duff, Aric W. Sanders, Norman A. Sanford
We demonstrate with spatially resolved, in situ temperature measurements and ex situ reflectance measurements that differences in appearance for masked and unmasked surfaces on patterned growth substrates arise from wavelength-dependent emissivity

Gallium Nitride Nanowire Probe for Near-Field Scanning Microwave Microscopy

January 15, 2014
Author(s)
Joel C. Weber, Paul T. Blanchard, Aric W. Sanders, Atif A. Imtiaz, Thomas M. Wallis, Kevin J. Coakley, Kristine A. Bertness, Pavel Kabos, Norman A. Sanford, Victor M. Bright
We report on the fabrication of a GaN nanowire probe for near-field scanning microwave microscopy. A single nanowire was Pt-bonded to a commercial Si cantilever prior to evaporation of a Ti/Al coating to provide a microwave signal pathway. Testing over a

Isn’t it time to get serious about standards?

November 18, 2013
Author(s)
Kristine A. Bertness
Current methods of composition measurement lack the ability to produce consistent results from laboratory to laboratory and across companies. NIST has developed AlGaAs SRMs to make standardization possible, but the standards need to be used. This opinion

Atom probe tomography evaporation behavior of C-axis GaN nanowires: Crystallographic, stoichiometric, and detection efficiency aspects

November 13, 2013
Author(s)
Norman A. Sanford, David R. Diercks, Brian Gorman, R Kirchofer, Kristine A. Bertness, Matthew D. Brubaker
The field evaporation behavior of c-axis GaN nanowires was explored in two different laser-pulsed atom probe tomography (APT) instruments. Transmission electron microscopy imaging before and after atom probe tomography analysis was used to assist in

Analysis of Contact Interfaces for Single GaN Nanowire Devices

November 1, 2013
Author(s)
Andrew M. Herrero, Paul T. Blanchard, Kristine A. Bertness
Single GaN nanowire (NW) devices fabricated on SiO 2 can exhibit a strong degradation after annealing due to the occurrence of void formation at the contact/SiO 2 interface. This void formation can cause cracking and delamination of the metal film, which

Trace water vapor analysis in specialty gases: sensor and spectroscopic approaches

July 1, 2013
Author(s)
Kristine A. Bertness, Mark W. Raynor, Kevin C. Cossel, Florian B. Adler, Jun Ye
The analysis of water vapor impurity is important in a number of specialty gas applications. However the main driver for the development and advancement of trace H 2O analysis techniques has been the microelectronics industry. The International Technology

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

AlGaAs Composition Standards at NIST

May 30, 2013
Author(s)
Kristine A. Bertness
High-accuracy comparison standards for Al mole fraction x in AlxGa1–xAs have been available at NIST since 2006 via the Standard Reference Material (SRM) program. This extended abstract describes the development history and technology behind these SRMs.

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

Nitro-Aromatic Explosive Sensing Using GaN Nanowire - Titania Nanocluster Hybrids

May 1, 2013
Author(s)
Albert Davydov, Geetha G. Aluri, Abhishek Motayed, Vladimir P. Oleshko, Kristine A. Bertness, Mulpuri V. Rao
A highly sensitive and selective detection of traces of nitro-aromatic explosive compounds by functionalizing gallium nitride (GaN) nanowires with anatase phase titania (titanium dioxide, TiO2) nanoclusters is demonstrated. The ultraviolet light photo

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