Publications

Ward, Daniel R.; Marshall, Michael T.; Campbell, DeAnna M.; Lu, Tzu-Ming L.; Koepke, Justin K.; Scrymgeour, David S.; Maurer, Leon M.; Baczewski, Andrew D.; Bussmann, Ezra B.; Misra, Shashank M.

Abstract not provided.

Journal of Materials Research

Katzenmeyer, Aaron M.; Luk, Ting S.; Bussmann, Ezra B.; Young, Steve M.; Anderson, Evan M.; Marshall, Michael T.; Ohlhausen, J.A.; Kotula, Paul G.; Lu, Ping L.; Campbell, DeAnna M.; Lu, Tzu-Ming L.; Liu, Peter Q.; Ward, Daniel R.; Misra, Shashank M.

Hydrogen lithography has been used to template phosphine-based surface chemistry to fabricate atomic-scale devices, a process we abbreviate as atomic precision advanced manufacturing (APAM). Here, we use mid-infrared variable angle spectroscopic ellipsometry (IR-VASE) to characterize single-nanometer thickness phosphorus dopant layers (δ-layers) in silicon made using APAM compatible processes. A large Drude response is directly attributable to the δ-layer and can be used for nondestructive monitoring of the condition of the APAM layer when integrating additional processing steps. The carrier density and mobility extracted from our room temperature IR-VASE measurements are consistent with cryogenic magneto-transport measurements, showing that APAM δ-layers function at room temperature. Finally, the permittivity extracted from these measurements shows that the doping in the APAM δ-layers is so large that their low-frequency in-plane response is reminiscent of a silicide. However, there is no indication of a plasma resonance, likely due to reduced dimensionality and/or low scattering lifetime.

Misra, Shashank M.; Ward, Daniel R.; Luhman, Dwight R.; Tracy, Lisa A.; Lu, Tzu-Ming L.; Baczewski, Andrew D.; Gamble, John K.; Moussa, Jonathan E.

Abstract not provided.

Campbell, DeAnna M.; Marshall, Michael T.; Maurer, Leon M.; Koepke, Justin K.; Lu, Tzu-Ming L.; Ward, Daniel R.; Misra, Shashank M.

Abstract not provided.

Bishop, Nathaniel B.; Carr, Stephen M.; Lu, Tzu-Ming L.; Lilly, Michael L.; Carroll, Malcolm; Young, Ralph W.; Nielsen, Erik N.; Muller, Richard P.; Rahman, Rajib R.; Tracy, Lisa A.; Wendt, J.R.

Abstract not provided.

AIP Advances

Sapkota, Keshab R.; Eley, S.; Bussmann, Ezra B.; Harris, C.T.; Maurer, Leon M.; Lu, Tzu-Ming L.

We present the fabrication of nano-magnet arrays, comprised of two sets of interleaving SmCo5 and Co nano-magnets, and the subsequent development and implementation of a protocol to program the array to create a one-dimensional rotating magnetic field. We designed the array based on the microstructural and magnetic properties of SmCo5 films annealed under different conditions, also presented here. Leveraging the extremely high contrast in coercivity between SmCo5 and Co, we applied a sequence of external magnetic fields to program the nano-magnet arrays into a configuration with alternating polarization, which based on simulations creates a rotating magnetic field in the vicinity of nano-magnets. Our proof-of-concept demonstration shows that complex, nanoscale magnetic fields can be synthesized through coercivity contrast of constituent magnetic materials and carefully designed sequences of programming magnetic fields.

Luhman, Dwight R.; Hardy, Will H.; Moussa, Jonathan E.; Maurer, Leon M.; Chuang, Y.C.; Li, J.-Y.L.; Lu, Tzu-Ming L.

Abstract not provided.

Misra, Shashank M.; Ward, Daniel R.; Baczewski, Andrew D.; Campbell, Quinn C.; Schmucker, Scott W.; Mounce, Andrew M.; Tracy, Lisa A.; Lu, Tzu-Ming L.; Marshall, Michael T.; Campbell, DeAnna M.

Quantum materials have long promised to revolutionize everything from energy transmission (high temperature superconductors) to both quantum and classical information systems (topological materials). However, their discovery and application has proceeded in an Edisonian fashion due to both an incomplete theoretical understanding and the difficulty of growing and purifying new materials. This project leverages Sandia's unique atomic precision advanced manufacturing (APAM) capability to design small-scale tunable arrays (designer materials) made of donors in silicon. Their low-energy electronic behavior can mimic quantum materials, and can be tuned by changing the fabrication parameters for the array, thereby enabling the discovery of materials systems which can't yet be synthesized. In this report, we detail three key advances we have made towards development of designer quantum materials. First are advances both in APAM technique and underlying mechanisms required to realize high-yielding donor arrays. Second is the first-ever observation of distinct phases in this material system, manifest in disordered 2D sheets of donors. Finally are advances in modeling the electronic structure of donor clusters and regular structures incorporating them, critical to understanding whether an array is expected to show interesting physics. Combined, these establish the baseline knowledge required to manifest the strongly-correlated phases of the Mott-Hubbard model in donor arrays, the first step to deploying APAM donor arrays as analogues of quantum materials.

Maurer, Leon M.; Gamble, John K.; Tracy, Lisa A.; Lu, Tzu-Ming L.

Abstract not provided.

Lu, Tzu-Ming L.; Anderson, Evan M.; Campbell, DeAnna M.; Marshall, Michael T.; Lu, Ping L.; Schmucker, Scott W.; Tracy, Lisa A.; Robison, Mitchell R.; Arghavani, Reza A.; Maurer, Leon N.; Baczewski, Andrew D.; Ward, Daniel R.; Misra, Shashank M.

Abstract not provided.

Muller, Richard P.; Bishop, Nathaniel B.; Lu, Tzu-Ming L.; Pluym, Tammy P.; Bielejec, Edward S.; Lilly, Michael L.; Landahl, Andrew J.; Carroll, Malcolm; Young, Ralph W.; Nielsen, Erik N.; Rahman, Rajib R.; Witzel, Wayne W.; Gao, Xujiao G.; Tracy, Lisa A.; Bussmann, Ezra B.

Abstract not provided.

Anderson, Evan M.; Campbell, DeAnna M.; Ivie, Jeffrey A.; Schmucker, Scott W.; Lu, Ping L.; Gao, Xujiao G.; Tracy, Lisa A.; Arghavani, Reza A.; Bussmann, Ezra B.; Baczewski, Andrew D.; Lu, Tzu-Ming L.; Katzenmeyer, Aaron M.; Scrymgeour, David S.; Misra, Shashank M.

Abstract not provided.

Brickson, Mitchell I.; Baczewski, Andrew D.; Hardy, Will H.; Jacobson, Noah T.; Lu, Tzu-Ming L.; Luhman, Dwight R.

Abstract not provided.

Brickson, Mitchell I.; Baczewski, Andrew D.; Hardy, Will H.; Jacobson, Noah T.; Lu, Tzu-Ming L.; Maurer, Leon M.; Luhman, Dwight R.

Abstract not provided.

Misra, Shashank M.; Ward, Daniel R.; Maurer, Leon M.; Lu, Tzu-Ming L.; Marshall, Michael T.; Campbell, DeAnna M.

Abstract not provided.

Lu, Tzu-Ming L.; Maurer, Leon M.; Bussmann, Ezra B.; Harris, Charles T.; Tracy, Lisa A.; Sapkota, Keshab R.

Abstract not provided.

Ward, Daniel R.; Campbell, DeAnna M.; Marshall, Michael T.; Lu, Tzu-Ming L.; Tracy, Lisa A.; Maurer, Leon M.; Baczewski, Andrew D.; Misra, Shashank M.

Abstract not provided.

Lu, Tzu-Ming L.; Bussmann, Ezra B.; Sapkota, Keshab R.; Eley, Serena E.; Tracy, Lisa A.; Maurer, Leon M.

Abstract not provided.

Applied Physics Letters

Lu, Tzu-Ming L.; Gamble, John K.; Muller, Richard P.; Nielsen, Erik N.; Bethke, D.; Ten Eyck, Gregory A.; Pluym, Tammy P.; Wendt, J.R.; Dominguez, Jason J.; Lilly, M.P.; Carroll, Malcolm; Wanke, M.C.

Enhancement-mode Si/SiGe electron quantum dots have been pursued extensively by many groups for their potential in quantum computing. Most of the reported dot designs utilize multiple metal-gate layers and use Si/SiGe heterostructures with Ge concentration close to 30%. Here, we report the fabrication and low-temperature characterization of quantum dots in the Si/Si0.8Ge0.2 heterostructures using only one metal-gate layer. We find that the threshold voltage of a channel narrower than 1 μm increases as the width decreases. The higher threshold can be attributed to the combination of quantum confinement and disorder. We also find that the lower Ge ratio used here leads to a narrower operational gate bias range. The higher threshold combined with the limited gate bias range constrains the device design of lithographic quantum dots. We incorporate such considerations in our device design and demonstrate a quantum dot that can be tuned from a single dot to a double dot. The device uses only a single metal-gate layer, greatly simplifying device design and fabrication.

Luhman, Dwight R.; Lu, Tzu-Ming L.; Gamble, John K.; Muller, Richard P.; Nielsen, Erik N.; Bethke, Donald T.; Ten Eyck, Gregory A.; Pluym, Tammy P.; Wendt, J.R.; Dominguez, Jason J.; Lilly, Michael L.; Carroll, Malcolm; Wanke, Michael W.

Abstract not provided.

Allemang, Christopher R.; Anderson, Evan M.; Baczewski, Andrew D.; Bussmann, Ezra B.; Butera, Robert E.; Campbell, DeAnna M.; Campbell, Quinn C.; Carr, Stephen M.; Frederick, Esther F.; Gamache, Phillip G.; Gao, Xujiao G.; Grine, Albert D.; Gunter, Mathew M.; Halsey, Connor H.; Ivie, Jeffrey A.; Katzenmeyer, Aaron M.; Leenheer, Andrew J.; Lepkowski, William L.; Lu, Tzu-Ming L.; Mamaluy, Denis M.; Mendez Granado, Juan P.; Pena, Luis F.; Schmucker, Scott W.; Scrymgeour, David S.; Tracy, Lisa A.; Wang, George T.; Ward, Dan W.; Young, Steve M.

While it is likely practically a bad idea to shrink a transistor to the size of an atom, there is no arguing that it would be fantastic to have atomic-scale control over every aspect of a transistor – a kind of crystal ball to understand and evaluate new ideas. This project showed that it was possible to take a niche technique used to place dopants in silicon with atomic precision and apply it broadly to study opportunities and limitations in microelectronics. In addition, it laid the foundation to attaining atomic-scale control in semiconductor manufacturing more broadly.

ECS Transactions

Hardy, Will H.; Su, Y.H.; Chuang, Y.; Maurer, L.N.; Brickson, M.; Baczewski, Andrew D.; Li, J.Y.; Lu, Tzu-Ming L.; Luhman, Dwight R.

In the field of semiconductor quantum dot spin qubits, there is growing interest in leveraging the unique properties of hole-carrier systems and their intrinsically strong spin-orbit coupling to engineer novel qubits. Recent advances in semiconductor heterostructure growth have made available high quality, undoped Ge/SiGe quantum wells, consisting of a pure strained Ge layer flanked by Ge-rich SiGe layers above and below. These quantum wells feature heavy hole carriers and a cubic Rashba-type spin-orbit interaction. Here, we describe progress toward realizing spin qubits in this platform, including development of multi-metal-layer gated device architectures, device tuning protocols, and charge-sensing capabilities. Iterative improvement of a three-layer metal gate architecture has significantly enhanced device performance over that achieved using an earlier single-layer gate design. We discuss ongoing, simulation-informed work to fine-tune the device geometry, as well as efforts toward a single-spin qubit demonstration.

Hardy, Will H.; Su, Yi-Hsin S.; Chuang, Yen C.; Maurer, Leon M.; Brickson, Mitchell I.; Baczewski, Andrew D.; Li, Jiun-Yun L.; Lu, Tzu-Ming L.; Luhman, Dwight R.

Abstract not provided.

Hardy, Will H.; Su, Y-H S.; Chuang, Y C.; Maurer, Leon M.; Brickson, Mitchell I.; Baczewski, Andrew D.; Li, J-Y L.; Lu, Tzu-Ming L.; Luhman, Dwight R.

Abstract not provided.

Hardy, Will H.; Su, Y-H S.; Chuang, Y C.; Maurer, Leon M.; Brickson, Mitchell I.; Baczewski, Andrew D.; Li, J-Y L.; Lu, Tzu-Ming L.; Luhman, Dwight R.

Abstract not provided.