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Search Publications by: Thomas Mitchell Wallis (Fed)

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Displaying 51 - 75 of 158

Vector-Network-Analyzer Calibration Using Line and Multiple Coplanar-Waveguide Offset Reflects

December 9, 2016
Author(s)
Arkadiusz C. Lewandowski, Wojciech Wiatr, Dazhen Gu, Nate Orloff, Thomas Mitchell (Mitch) Wallis, Pavel Kabos
We present the application of our newly developed multi-reflect-thru technique to vector-network-analyzer calibration in the on-wafer environment. This technique uses a set of highly-reflective one-port devices, referred to as offset-reflects, and a single

Near-field microwave microscopy of one-dimensional nanostructures

May 23, 2016
Author(s)
Samuel Berweger, Paul T. Blanchard, Rebecca C. Quardokus, Frank W. DelRio, Thomas Mitchell (Mitch) Wallis, Pavel Kabos, Sergiy Krylyuk, Albert Davydov
With the ability to measure sample conductivity with nanometer spatial resolution, scanning microwave microscopy (SMM) is a powerful tool to study nanoscale electronic systems and devices. Here we demonstrate the general capability to image electronic

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

Microwave characterization of ink-jet printed CPW on PET substrates

December 3, 2015
Author(s)
Thomas M. Wallis
This paper describes microwave characterization of coplanar waveguide (CPW) lines formed by ink-jet printed technology on flexible polyethylene terephthalate (PET) substrates. The reel-to-reel printing process uses inkjet printing as a precursor for 2$\mu

Introduction to the Special Issue

May 1, 2015
Author(s)
Thomas M. Wallis, Goutam Chattopadhyay, Fabio Cocetti, Luca Pierantoni
In the inaugural editorial of these IEEE Transactions on Terahertz Science and Technology – September 2011, the editor-in-chief anticipated that the work published in this journal would push beyond topics that are familiar to the traditional RF and

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

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

Measurement Techniques for RF Nanoelectronics

January 20, 2014
Author(s)
Thomas M. Wallis, Luca Pierantoni
In 1882, in a lecture at the University of Leiden, Nobel prize-winner Heike Kammerlingh Onnes coined the motto: “Through Measurement to Knowledge” [1]. In that same lecture, he gave many historical examples of how measurements have fostered insight

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