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Search Publications by: Norman A. Sanford (Fed)

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Displaying 1 - 25 of 161

Atom Probe Tomography Using an Extreme Ultraviolet Trigger Pulse

September 1, 2023
Author(s)
Benjamin Caplins, Ann Chiaramonti Debay, Jacob Garcia, Norman A. Sanford, Luis Miaja Avila
Atom probe tomography (APT) is a powerful materials characterization technique capable of measuring the isotopically resolved three-dimensional (3D) structure of nanoscale specimens with atomic resolution. Modern APT instrumentation most often uses an

Fabrication of Specimens for Atom Probe Tomography using a Combined Gallium and Neon Focused Ion Beam Milling Approach

August 16, 2023
Author(s)
Frances Allen, Paul Blanchard, David Pappas, Russell Lake, Deying Xia, John Notte, Ruopeng Zhang, Andrew Minor, Norman A. Sanford
We demonstrate a new focused ion beam sample preparation method for atom probe tomography. The key aspect of the new method is that we use a neon ion beam for the final tip shaping after conventional annulus milling using gallium ions. This dual-ion

Laser-assisted atom probe tomography of c-plane and m-plane InGaN test structures

April 29, 2022
Author(s)
Norman A. Sanford, Paul T. Blanchard, Alexana Roshko, Ashwin Rishinaramangalam, Daniel Feezell, Albert Davydov
Laser-assisted atom probe tomography (L-APT) was used to measure the indium mole fraction x of c-plane, MOCVD-grown, GaN/InxGa1-xN/GaN test structures and the results were compared with Rutherford backscattering analysis (RBS). Four separate sample types

Bulk-Like Properties Observed From High Density GaN Nanocolumns Grown by Molecular Beam Epitaxy

October 12, 2021
Author(s)
J E. Van Nostrand, R Cortez, J Boecki, J D. Albrecht, C E. Stutz, K L. Averett, Norman Sanford, Albert Davydov
Vertical GaN nanocolumns (NCs) having a width of 90+10 nm and a length of the film thickness were grown by plasma-assisted molecular beam epitaxy on Al_subscript 2)O_subscript 3} (0001). Low temperature photo-luminescence measurements of NC films results

Comparative Apex Electrostatics of Atom Probe Tomography Specimens

April 28, 2021
Author(s)
Qihua Zhang, B. Klein, Norman A. Sanford, Ann Chiaramonti Debay
Laser-assisted atom probe tomography (APT) is the only known analytical method that can simultaneously provide sub-nm 3D spatial resolution and quantitative sensitivity approaching 1 ppm. APT has been applied with great success to the analysis of metals

Crystallographic Polarity Measurements in Two-Terminal GaN Nanowire Devices by Lateral Piezoresponse Force Microscopy

July 23, 2020
Author(s)
Matthew Brubaker, Alexana Roshko, Samuel Berweger, Paul T. Blanchard, Todd E. Harvey, Norman A. Sanford, Kris A. Bertness
Lateral piezoresponse force microscopy (L-PFM) is demonstrated as a reliable method for determining the crystallographic polarity of individual, dispersed GaN nanowires that were functional components in electrical test structures. In contrast to PFM

An Algorithm for Correcting Systematic Energy Deficits in the Atom Probe Mass Spectra of Insulating Samples

April 15, 2020
Author(s)
Benjamin W. Caplins, Paul T. Blanchard, Ann C. Chiaramonti Debay, David R. Diercks, Luis Miaja Avila, Norman A. Sanford
Improvements in the mass resolution of a mass spectrometer directly correlate to improvements in peak identification and quantification. Here we describe a post-processing technique developed to increase the quality of mass spectra of strongly insulating

Atom Probe Tomography using Extreme-Ultraviolet Light

March 27, 2020
Author(s)
Luis Miaja Avila, Ann C. Chiaramonti Debay, Benjamin W. Caplins, David R. Diercks, Brian Gorman, Norman A. Sanford
We present a different approach to laser-assisted atom probe tomography, where instead of using a near-UV laser for inducing a thermal transient, we use an extreme-ultraviolet coherent light source to trigger eld ion emission at the tip's apex. The use of

Field Ion Emission in an Atom Probe Microscope Triggered by Femtosecond-Pulsed Coherent Extreme Ultraviolet Light

March 12, 2020
Author(s)
Ann C. Chiaramonti Debay, Luis Miaja Avila, Benjamin W. Caplins, Paul T. Blanchard, Norman A. Sanford, Brian Gorman, David R. Diercks
This paper reports construction of an extreme ultraviolet (EUV) radiation-triggered atom probe tomograph and describes the results from initial experiments on amorphous SiO2. Femtosecond-pulsed coherent EUV radiation of 29.6 nm wavelength (41.85 eV photon

An Atom Probe Tomograph Incorporating a Wavelength-Tuneable Femtosecond-Pulsed Coherent Extreme Ultraviolet Light Source

June 19, 2019
Author(s)
Ann C. Chiaramonti Debay, Luis Miaja Avila, Paul T. Blanchard, David R. Diercks, Brian Gorman, Norman A. Sanford
Pulsed coherent extreme ultraviolet (EUV) radiation is a potential promising alternative to pulsed infra-red, visible, and near- ultraviolet laser sources for atom probe tomography. In addition to having the benefit of high absorption across the periodic

Laser-assisted atom probe tomography of Ti/TiN films deposited on Si

December 21, 2016
Author(s)
Norman A. Sanford, Paul T. Blanchard, Ryan M. White, Michael R. Vissers, Albert Davydov, D R. Diercks, David P. Pappas
Laser-assisted atom probe tomography (L-APT) was used to examine superconducting TiN/Ti/TiN trilayer films with nominal respective thicknesses of 5/5/5 (nm). The trilayers were deposited on Si substrates by reactive sputtering. Electron energy loss

Raman spectroscopy based measurements of carrier concentration in n-type GaN nanowires grown by plasma-assisted molecular beam epitaxy

September 30, 2016
Author(s)
Lawrence H. Robins, Elizabeth Horneber, Norman A. Sanford, Kristine A. Bertness, John B. Schlager
The carrier concentration in ensembles of n-type GaN nanowires (NWs) grown by plasma-assisted molecular beam epitaxy was determined by curve-fitting analysis of Raman spectra, based on modeling of the carrier concentration dependence of the longitudinal

Spontaneous growth of GaN nanowire nuclei on N- and Al-polar AlN: A piezoresponse force microscopy study of crystallographic polarity

March 2, 2016
Author(s)
Matthew D. Brubaker, Alexana Roshko, Paul T. Blanchard, Todd E. Harvey, Norman A. Sanford, Kristine A. Bertness
The polarity of gallium nitride (GaN) nanowire nuclei grown on AlN layers was studied by piezoresponse force microscopy (PFM). N- or Al-polar AlN layers were grown by molecular beam epitaxy (MBE) on Si (111) substrates by use of Al- or N-rich growth

Near-field control and imaging of free charge carrier variations in GaN nanowires

February 15, 2016
Author(s)
Samuel Berweger, Paul T. Blanchard, Matthew Brubaker, Kevin J. Coakley, Norman A. Sanford, Thomas Mitchell (Mitch) Wallis, Kris A. Bertness, Pavel Kabos
Despite their uniform crystallinity, the shape and faceting of semiconducting nanowires (NWs) can give rise to variations in structure and associated electronic properties. Here we investigate local variations in electronic structure across individual n

Polarity-Controlled GaN/AlN Nucleation Layers for Selective-Area Growth of GaN Nanowire Arrays on Si(111) Substrates by Molecular Beam Epitaxy

December 18, 2015
Author(s)
Matthew D. Brubaker, Shannon M. Duff, Todd E. Harvey, Paul T. Blanchard, Alexana Roshko, Aric W. Sanders, Norman A. Sanford, Kristine A. Bertness
We have demonstrated dramatic improvement in the quality of selective-area GaN nanowire growth by controlling the polarity of the underlying nucleation layers. In particular, we find that N- polarity is beneficial for the growth of large ordered nanowire

Microwave Near-Field Imaging of Two-Dimensional Semiconductors

January 27, 2015
Author(s)
Samuel Berweger, Joel Weber, Jimmy J. Li, Jesus M. Velazquez, Adam Pieterick, Norman A. Sanford, Albert V. Davydov, Thomas Mitchell (Mitch) Wallis, Pavel Kabos
Optimizing new generations of 2D devices based on van der Waals materials will require techniques capable of measuring variations in electronic properties in situ and with nanometer spatial resolution. We perform scanning microwave microscopy (SMM) imaging