Publications

Applied Physics Letters

Lu, Tzu-Ming L.; Bishop, Nathaniel B.; Pluym, Tammy P.; Means, Joel L.; Kotula, Paul G.; Cederberg, Jeffrey G.; Tracy, Lisa A.; Lilly, Michael L.; Carroll, Malcolm

Abstract not provided.

NanoLetters?

Bishop, Nathaniel B.; Lilly, Michael L.; Carroll, Malcolm; Young, Ralph W.; Ten Eyck, Gregory A.; Wendt, J.R.; Bielejec, Edward S.; Tracy, Lisa A.

Abstract not provided.

Bishop, Nathaniel B.; Young, Ralph W.; Ten Eyck, Gregory A.; Wendt, J.R.; Lilly, Michael L.; Carroll, Malcolm

Abstract not provided.

Witzel, Wayne W.; Carroll, Malcolm

Abstract not provided.

Rahman, Rajib R.; Nielsen, Erik N.; Muller, Richard P.; Carroll, Malcolm

Abstract not provided.

Grace, Matthew G.; Witzel, Wayne W.; Carroll, Malcolm

Abstract not provided.

Carroll, Malcolm

Abstract not provided.

Nature

Gurrieri, Thomas G.; Hines, Kathleen J.; Carroll, Malcolm

Abstract not provided.

Applied Physics Letters

Young, Ralph W.; Stevens, Jeffrey S.; Lilly, Michael L.; Carroll, Malcolm; Ten Eyck, Gregory A.; Childs, Kenton D.; Wendt, J.R.; Grubbs, Robert K.

Abstract not provided.

Carroll, Malcolm; Tarman, Thomas D.

Qubits demonstrated using GaAs double quantum dots (DQD). The qubit basis states are the (1) singlet and (2) triplet stationary states. Long spin decoherence times in silicon spurs translation of GaAs qubit in to silicon. In the near term the goals are: (1) Develop surface gate enhancement mode double quantum dots (MOS & strained-Si/SiGe) to demonstrate few electrons and spin read-out and to examine impurity doped quantum-dots as an alternative architecture; (2) Use mobility, C-V, ESR, quantum dot performance & modeling to feedback and improve upon processing, this includes development of atomic precision fabrication at SNL; (3) Examine integrated electronics approaches to RF-SET; (4) Use combinations of numerical packages for multi-scale simulation of quantum dot systems (NEMO3D, EMT, TCAD, SPICE); and (5) Continue micro-architecture evaluation for different device and transport architectures.

Young, Ralph W.; Tracy, Lisa A.; Bishop, Nathaniel B.; Carroll, Malcolm; Muller, Richard P.

We have compared simulations using solutions of Poisson's equation to detailed capacitance measurements on a double quantum dot structure. We tabulate the results and show which cases show good agreement and which do not. The capacitance values are also compared to those calculated by a solution of Laplace's equation. Electron density is plotted and discussed. In order to understand relevant potential barriers we compare simulations at 50 Kelvin to simulations at 15 Kelvin. We show that the charge density does not differ greatly, but that the conduction band potential does. However, a method of estimating the potential at 0 Kelvin based on the charge distribution at 50 Kelvin is shown to be close to the potential at 15 Kelvin. This method was used to estimate potential barriers at 0 Kelvin in two quantum dot structures.

Lilly, Michael L.; Carroll, Malcolm; Young, Ralph W.; Ten Eyck, Gregory A.; Childs, Kenton D.; Wendt, J.R.; Grubbs, Robert K.

We report low-temperature transport measurements of a silicon metal-oxide-semiconductor (MOS) double quantum dot (DQD). In contrast to previously reported measurements of DQD's in Si MOS structures, our device has a lateral gate geometry very similar to that used by Petta et al. to demonstrate coherent manipulation of single electron spins. This gate design provides a high degree of tunability, allowing for independent control over individual dot occupation and tunnel barriers, as well as the ability to use nearby constrictions to sense dot charge occupation. Comparison of experimentally extracted capacitances between the dot and nearby gates with electrostatic modeling demonstrates the presence of disorder and the ability to partially compensate for this disorder by adjustment of gate voltages. We experimentally show gate-controlled tuning of the interdot coupling over a wide range of energies, an important step towards potential quantum computing applications.

Physical Review Letters

Witzel, Wayne W.; Carroll, Malcolm

Abstract not provided.

Bishop, Nathaniel B.; Stevens, Jeffrey S.; Childs, Kenton D.; Ohlhausen, J.A.; Lilly, Michael L.; Carroll, Malcolm; Young, Ralph W.; Bielejec, Edward S.; Ten Eyck, Gregory A.; Wendt, J.R.; Rahman, Rajib R.; Grubbs, Robert K.

We fabricated a split-gate defined point contact in a double gate enhancement mode Si-MOS device, and implanted Sb donor atoms using a self-aligned process. E-beam lithography in combination with a timed implant gives us excellent control over the placement of dopant atoms, and acts as a stepping stone to focused ion beam implantation of single donors. Our approach allows us considerable latitude in experimental design in-situ. We have identified two resonance conditions in the point contact conductance as a function of split gate voltage. Using tunneling spectroscopy, we probed their electronic structure as a function of temperature and magnetic field. We also determine the capacitive coupling between the resonant feature and several gates. Comparison between experimental values and extensive quasi-classical simulations constrain the location and energy of the resonant level. We discuss our results and how they may apply to resonant tunneling through a single donor.

Rahman, Rajib R.; Muller, Richard P.; Levy, James E.; Carroll, Malcolm

Abstract not provided.

Gurrieri, Thomas G.; Hamlet, Jason H.; Levy, James E.; Akinnikawe, Erin M.; Young, Ralph W.; Carroll, Malcolm

Abstract not provided.

Witzel, Wayne W.; Carroll, Malcolm

Abstract not provided.

Doyle, Barney L.; Carroll, Malcolm; Bishop, Nathaniel B.

Abstract not provided.

Carroll, Malcolm

Abstract not provided.

Bielejec, Edward S.; Bishop, Nathaniel B.; Carroll, Malcolm; Doyle, Barney L.

Abstract not provided.

Rahman, Rajib R.; Muller, Richard P.; Carroll, Malcolm

Abstract not provided.

Rahman, Rajib R.; Muller, Richard P.; Carroll, Malcolm

The observation and characterization of a single atom system in silicon is a significant landmark in half a century of device miniaturization, and presents an important new laboratory for fundamental quantum and atomic physics. We compare with multi-million atom tight binding (TB) calculations the measurements of the spectrum of a single two-electron (2e) atom system in silicon - a negatively charged (D-) gated Arsenic donor in a FinFET. The TB method captures accurate single electron eigenstates of the device taking into account device geometry, donor potentials, applied fields, interfaces, and the full host bandstructure. In a previous work, the depths and fields of As donors in six device samples were established through excited state spectroscopy of the D0 electron and comparison with TB calculations. Using self-consistent field (SCF) TB, we computed the charging energies of the D- electron for the same six device samples, and found good agreement with the measurements. Although a bulk donor has only a bound singlet ground state and a charging energy of about 40 meV, calculations show that a gated donor near an interface can have a reduced charging energy and bound excited states in the D- spectrum. Measurements indeed reveal reduced charging energies and bound 2e excited states, at least one of which is a triplet. The calculations also show the influence of the host valley physics in the two-electron spectrum of the donor.

Physical Review B

Nielsen, Erik N.; Carroll, Malcolm; Young, Ralph W.; Muller, Richard P.

Abstract not provided.

Bielejec, Edward S.; Eng, Kevin E.; Bishop, Nathaniel B.; Doyle, Barney L.; Carroll, Malcolm

Abstract not provided.

Lilly, Michael L.; Silva, Beverly L.; Carroll, Malcolm; Stevens, Jeffrey S.; Reno, J.L.; Tracy, Lisa A.; Eng, Kevin E.; Childs, Kenton D.; Ten Eyck, Gregory A.; Wendt, J.R.; Grubbs, Robert K.; Tibbetts, Denise R.

Abstract not provided.