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Search Publications by: Michael Stewart (Fed)

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Displaying 1 - 21 of 21

Multi-scale alignment to buried atom-scale devices using Kelvin probe force microscopy

February 24, 2024
Pradeep Namboodiri, Jonathan Wyrick, Gheorghe Stan, Xiqiao Wang, Fan Fei, Ranjit Kashid, Scott Schmucker, Richard Kasica, Bryan Barnes, Michael Stewart, Richard M. Silver
Fabrication of quantum devices by atomic scale patterning with a Scanning Tunneling Microscope (STM) has led to the development of single/few atom transistors, few-donor/quantum dot devices for spin manipulation and arrayed few-donor devices for analog

Alternatives to aluminum gates for silicon quantum devices: Defects and strain

September 15, 2021
Ryan Stein, Zachary Barcikowski, Sujitra Pookpanratana, Joshua M. Pomeroy, Michael Stewart
Gate-defined quantum dots (QD) benefit from the use of small grain size metals for gates materials because it aids in shrinking the device dimensions. However, it is not clear what differences arise with respect to process-induced defect densities and

Reduction of charge offset drift using plasma oxidized aluminum in SETs

October 26, 2020
Yanxue Hong, Ryan Stein, Michael Stewart, Neil M. Zimmerman, Joshua M. Pomeroy
Aluminum oxide (AlOx)-based single-electron transistors (SETs) fabricated in ultra-high vacuum (UHV) chambers using in situ plasma oxidation show excellent stabilities over more than a week, enabling applications as tunnel barriers, capacitor dielectrics

The effect of strain on tunnel barrier height in silicon quantum devices

July 13, 2020
Ryan Stein, Michael Stewart
Semiconductor quantum dot (QD) devices experience a modulation of the band structure at the edge of lithographically defined gates due to mechanical strain. This modulation can play a prominent role in the device behavior at low temperatures, where QD

Electron-electron interactions in low-dimensional Si:P delta layers

June 15, 2020
Joseph Hagmann, Xiqiao Wang, Ranjit Kashid, Pradeep Namboodiri, Jonathan Wyrick, Scott W. Schmucker, Michael Stewart, Richard M. Silver, Curt A. Richter
Key to producing quantum computing devices based on the atomistic placement of dopants in silicon by scanning tunneling microscope (STM) lithography is the formation of embedded highly doped Si:P delta layers (δ-layers). This study investigates the

Atomic-scale control of tunneling in donor-based devices

May 11, 2020
Xiqiao Wang, Jonathan E. Wyrick, Ranjit V. Kashid, Pradeep N. Namboodiri, Scott W. Schmucker, Andrew Murphy, Michael D. Stewart, Richard M. Silver
Atomically precise donor-based quantum devices are a promising candidate for scalable solid- state quantum computing. Atomically precise design and implementation of the tunnel coupling in these devices is essential to realize gate-tunable exchange

Low-resistance, high-yield electrical contacts to atom scale Si:P devices using palladium silicide

March 29, 2019
Scott W. Schmucker, Pradeep Namboodiri, Ranjit Kashid, Xiqiao Wang, Binhui Hu, Jonathan Wyrick, Alline Myers, Joshua D. Schumacher, Richard M. Silver, Michael Stewart
Scanning tunneling microscopy (STM) enables the fabrication of 2-D delta-doped structures in Si with atomistic precision, with applications from tunnel field effect transistors to qubits. The combination of a very small contact area and the restrictive

Machine Learning techniques for state recognition and auto-tuning in quantum dots

January 21, 2019
Sandesh Kalantre, Justyna Zwolak, Stephen Ragole, Xingyao Wu, Neil M. Zimmerman, Michael Stewart, Jacob Taylor
Recent progress in building large-scale quantum devices for exploring quantum computing and simulation paradigms has relied upon effective tools for achieving and maintaining good experimental parameters, i.e. tuning up devices. In many cases, including in

Effect of device design on charge offset drift in Si/SiO2 single electron devices

October 9, 2018
Binhui Hu, Erick Ochoa, Daniel Sanchez, Justin K. Perron, Neil M. Zimmerman, Michael Stewart
We have measured the low-frequency time instability known as charge offset drift of Si/SiO2 single electron devices (SEDs) with and without an overall poly-Si top gate. We find that SEDs with a poly-Si top gate have significantly less charge offset drift

STM patterned nanowire measurements using photolithographically defined implants in Si(100)

January 29, 2018
Aruna N. Ramanayaka, Hyun Soo Kim, Ke Tang, Xiqiao Wang, Richard M. Silver, Michael D. Stewart, Joshua M. Pomeroy
Using photolithographically defined implant wires for electrical connections, we demonstrate measurement of a scanning tunneling microscope (STM) patterned nanoscale electronic device on Si(100), eliminating the onerous alignment procedures and electron

Quantifying Atom-scale Dopant Movement and Electrical Activation in Si:P Monolayers

January 26, 2018
Xiqiao Wang, Joseph A. Hagmann, Pradeep N. Namboodiri, Jonathan E. Wyrick, Kai Li, Roy E. Murray, Frederick Meisenkothen, Alline F. Myers, Michael D. Stewart, Richard M. Silver
Doped semiconductor structures with ultra-sharp dopant confinement, minimal lattice defects, and high carrier concentrations are essential attributes in the development of both ultra- scaled conventional semiconductor devices and emerging all-silicon

Weak localization thickness measurements of embedded phosphorus delta layers in silicon produced by PH3 dosing

January 23, 2018
Joseph A. Hagmann, Xiqiao Wang, Pradeep N. Namboodiri, Jonathan E. Wyrick, Roy E. Murray, Michael D. Stewart, Richard M. Silver
The key building blocks for devices based on the deterministic placement of dopants in silicon are the formation of phosphorus dopant monolayers and the overgrowth of high quality crystalline Si. Lithographically defined dopant delta-layers can be formed

AC Signal Characterization for Optimization of a CMOS Single Electron Pump

January 8, 2018
Roy E. Murray, Justin K. Perron, Michael D. Stewart, Neil M. Zimmerman
Pumping single electrons at a set rate is being widely pursued as an electrical current standard. Much work has been done on pumping using a single AC signal, but using multiple coordinated AC signals may help lower error rates. Whether pumping with one or

Valley blockade in a silicon double quantum dot

November 13, 2017
Justin K. Perron, Michael Gullans, Jacob Taylor, Michael Stewart, Neil M. Zimmerman
Electrical transport in double quantum dots (DQD) is useful for illuminating many interesting aspects of the carrier states in quantum dots. Here we show data comparing bias triangles (i.e., regions of allowed current in DQDs) at positive and negative bias

Towards single atom devices for quantum information and metrology: weak localization in embedded phosphorus delta layers in silicon

June 29, 2017
Joseph A. Hagmann, Xiqiao Wang, Pradeep N. Namboodiri, Jonathan E. Wyrick, Roy E. Murray, Michael D. Stewart, Richard M. Silver, Curt A. Richter
The key building block for devices based on the deterministic placement of dopants in silicon is the formation of phosphorus dopant monolayers and the overgrowth of high quality crystalline Si. Lithographically defined dopant delta-layers can be formed

Stability of Single Electron Devices: Charge Offset Drift

June 29, 2016
Michael D. Stewart, Neil M. Zimmerman
Abstract: Single electron devices (SEDs) afford the opportunity to isolate and manipulate individual electrons. This ability imbues SEDs with potential applications in a wide array of areas from metrology (current and capacitance) to quantum information

A New Regime of Pauli-Spin Blockade

April 7, 2016
Justin K. Perron, Michael D. Stewart, Neil M. Zimmerman
Pauli-spin blockade is a phenomenon that allows for a type of spin to charge conversion often used to probe fundamental physics such as spin relaxation and singlet-triplet coupling. In this paper we theoretically explore Pauli-spin blockade as a function