Publications

Campbell, Quinn C.; Ivie, Jeffrey A.; Koepke, Justin K.; Brickson, Mitchell I.; Schultz, Peter A.; Muller, Richard P.; Bussmann, Ezra B.; Baczewski, Andrew D.; Mounce, Andrew M.; Misra, Shashank M.

Abstract not provided.

Baczewski, Andrew D.; Pavanello, Michele P.

Abstract not provided.

Morrison, Benjamin M.; Baczewski, Andrew D.; Lutz, Jesse J.; Metodi, Tzvetan S.; Landahl, Andrew J.

Abstract not provided.

Journal of Physical Chemistry C

Campbell, Quinn C.; Ivie, Jeffrey A.; Bussmann, Ezra B.; Schmucker, Scott W.; Baczewski, Andrew D.; Misra, Shashank M.

Diborane (B2H6) is a promising molecular precursor for atomic precision p-type doping of silicon that has recently been experimentally demonstrated [ Škereň et al. Nat. Electron. 2020 ]. We use density functional theory (DFT) calculations to determine the reaction pathway for diborane dissociating into a species that will incorporate as electrically active substitutional boron after adsorbing onto the Si(100)-2×1 surface. Our calculations indicate that diborane must overcome an energy barrier to adsorb, explaining the experimentally observed low sticking coefficient (<1 × 10-4 at room temperature) and suggesting that heating can be used to increase the adsorption rate. Upon sticking, diborane has an ≈50% chance of splitting into two BH3 fragments versus merely losing hydrogen to form a dimer such as B2H4. As boron dimers are likely electrically inactive, whether this latter reaction occurs is shown to be predictive of the incorporation rate. The dissociation process proceeds with significant energy barriers, necessitating the use of high temperatures for incorporation. Using the barriers calculated from DFT, we parameterize a Kinetic Monte Carlo model that predicts the incorporation statistics of boron as a function of the initial depassivation geometry, dose, and anneal temperature. Our results suggest that the dimer nature of diborane inherently limits its doping density as an acceptor precursor and furthermore that heating the boron dimers to split before exposure to silicon can lead to poor selectivity on hydrogen and halogen resists. This suggests that, while diborane works as an atomic precision acceptor precursor, other non-dimerized acceptor precursors may lead to higher incorporation rates at lower temperatures.

Campbell, Quinn C.; Ivie, Jeffrey A.; Bussmann, Ezra B.; Schmucker, Scott W.; Baczewski, Andrew D.; Misra, Shashank M.

Abstract not provided.

Wang, George T.; Lu, Ping L.; Sapkota, Keshab R.; Baczewski, Andrew D.; Campbell, Quinn C.; Schultz, Peter A.; Jones, Kevin S.; Turner, Emily M.; Sharrock, Chappel J.; Law, Mark E.; Yang, Hongbin Y.

This project sought to develop a fundamental understanding of the mechanisms underlying a newly observed enhanced germanium (Ge) diffusion process in silicon germanium (SiGe) semiconductor nanostructures during thermal oxidation. Using a combination of oxidationdiffusion experiments, high resolution imaging, and theoretical modeling, a model for the enhanced Ge diffusion mechanism was proposed. Additionally, a nanofabrication approach utilizing this enhanced Ge diffusion mechanism was shown to be applicable to arbitrary 3D shapes, leading to the fabrication of stacked silicon quantum dots embedded in SiGe nanopillars. A new wet etch-based method for preparing 3D nanostructures for highresolution imaging free of obscuring material or damage was also developed. These results enable a new method for the controlled and scalable fabrication of on-chip silicon nanostructures with sub-10 nm dimensions needed for next generation microelectronics, including low energy electronics, quantum computing, sensors, and integrated photonics.

Jacobson, Noah T.; Harvey-Collard, Patrick H.; Baczewski, Andrew D.; Gamble, John K.; Rudolph, Martin R.; Muller, Richard P.; Nielsen, Erik N.; Carroll, Malcolm

Abstract not provided.

Journal of Computational Physics

Baczewski, Andrew D.; Vikram, Melapudi V.; Shanker, Balasubramaniam S.; Kempel, Leo K.

Diffusion, lossy wave, and Klein–Gordon equations find numerous applications in practical problems across a range of diverse disciplines. The temporal dependence of all three Green’s functions are characterized by an infinite tail. This implies that the cost complexity of the spatio-temporal convolutions, associated with evaluating the potentials, scales as O(N_s²N_t²), where N_s and N_t are the number of spatial and temporal degrees of freedom, respectively. In this paper, we discuss two new methods to rapidly evaluate these spatio-temporal convolutions by exploiting their block-Toeplitz nature within the framework of accelerated Cartesian expansions (ACE). The first scheme identifies a convolution relation in time amongst ACE harmonics and the fast Fourier transform (FFT) is used for efficient evaluation of these convolutions. The second method exploits the rank deficiency of the ACE translation operators with respect to time and develops a recursive numerical compression scheme for the efficient representation and evaluation of temporal convolutions. It is shown that the cost of both methods scales as O(N_sN_tlog²N_t). Furthermore, several numerical results are presented for the diffusion equation to validate the accuracy and efficacy of the fast algorithms developed here.

IEEE Transactions on Antennas and Propagation

Baczewski, Andrew D.; Dault, Daniel D.; Shanker, Balasubramaniam S.

We present an algorithm for the fast and efficient solution of integral equations that arise in the analysis of scattering from periodic arrays of PEC objects, such as multiband frequency selective surfaces (FSS) or metamaterial structures. Our approach relies upon the method of Accelerated Cartesian Expansions (ACE) to rapidly evaluate the requisite potential integrals. ACE is analogous to FMM in that it can be used to accelerate the matrix vector product used in the solution of systems discretized using MoM. Here, ACE provides linear scaling in both CPU time and memory. Details regarding the implementation of this method within the context of periodic systems are provided, as well as results that establish error convergence and scalability. In addition, we also demonstrate the applicability of this algorithm by studying several exemplary electrically dense systems.

arXiv posting

Gamble, John K.; Jacobson, Noah T.; Nielsen, Erik N.; Baczewski, Andrew D.; Moussa, Jonathan E.; Montano, Ines M.; Muller, Richard P.

Abstract not provided.

Journal of Physics Condensed Matter

Owen, J.H.G.; Campbell, Quinn C.; Santini, R.; Ivie, J.A.; Baczewski, Andrew D.; Schmucker, S.W.; Bussmann, Ezra B.; Misra, Shashank M.; Randall, J.N.

Atomically precise ultradoping of silicon is possible with atomic resists, area-selective surface chemistry, and a limited set of hydride and halide precursor molecules, in a process known as atomic precision advanced manufacturing (APAM). It is desirable to expand this set of precursors to include dopants with organic functional groups and here we consider aluminium alkyls, to expand the applicability of APAM. We explore the impurity content and selectivity that results from using trimethyl aluminium and triethyl aluminium precursors on Si(001) to ultradope with aluminium through a hydrogen mask. Comparison of the methylated and ethylated precursors helps us understand the impact of hydrocarbon ligand selection on incorporation surface chemistry. Combining scanning tunneling microscopy and density functional theory calculations, we assess the limitations of both classes of precursor and extract general principles relevant to each.

Journal of Physical Chemistry C

Radue, Matthew S.; Baek, Sungha; Farzaneh, Azadeh; Dwyer, K.J.; Campbell, Quinn C.; Baczewski, Andrew D.; Bussmann, Ezra B.; Wang, George T.; Mo, Yifei; Misra, Shashank M.; Butera, R.E.

The adsorption of AlCl3 on Si(100) and the effect of annealing the AlCl3-dosed substrate were studied to reveal key surface processes for the development of atomic-precision, acceptor-doping techniques. This investigation was performed via scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. At room temperature, AlCl3 readily adsorbed to the Si substrate dimers and dissociated to form a variety of species. Annealing the AlCl3-dosed substrate at temperatures below 450 °C produced unique chlorinated aluminum chains (CACs) elongated along the Si(100) dimer row direction. An atomic model for the chains is proposed with supporting DFT calculations. Al was incorporated into the Si substrate upon annealing at 450 °C and above, and Cl desorption was observed for temperatures beyond 450 °C. Al-incorporated samples were encapsulated in Si and characterized by secondary ion mass spectrometry (SIMS) depth profiling to quantify the Al atom concentration, which was found to be in excess of 1020 cm-3 across a ∼2.7 nm-thick δ-doped region. The Al concentration achieved here and the processing parameters utilized promote AlCl3 as a viable gaseous precursor for novel acceptor-doped Si materials and devices for quantum computing.

Jacobson, Noah T.; Harvey-Collard, Patrick H.; Baczewski, Andrew D.; Gamble, John K.; Rudolph, Martin R.; Nielsen, Erik N.; Muller, Richard P.; Carroll, Malcolm

Abstract not provided.

Technical Digest - International Electron Devices Meeting, IEDM

Harvey-Collard, Patrick; Jock, Ryan M.; Jacobson, Noah T.; Baczewski, Andrew D.; Mounce, Andrew M.; Curry, Matthew J.; Ward, Daniel R.; Anderson, John M.; Manginell, Ronald P.; Wendt, J.R.; Rudolph, Martin R.; Pluym, Tammy P.; Lilly, Michael L.; Pioro-Ladrière, Michel; Carroll, Malcolm

Qubits based on transistor-like Si MOS nanodevices are promising for quantum computing. In this work, we demonstrate a double quantum dot spin qubit that is all-electrically controlled without the need for any external components, like micromagnets, that could complicate integration. Universal control of the qubit is achieved through spin-orbit-like and exchange interactions. Using single shot readout, we show both DC- and AC-control techniques. The fabrication technology used is completely compatible with CMOS.

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.

Katzenmeyer, Aaron M.; Goldflam, Michael G.; Beechem, Thomas E.; Jarzembski, Amun J.; Baczewski, Andrew D.; Young, Steve M.

Abstract not provided.

Moussa, Jonathan M.; Baczewski, Andrew D.

Abstract not provided.

Schmucker, Scott W.; Frederick, Esther F.; Campbell, Quinn C.; Ivie, Jeffrey A.; Anderson, Evan M.; Dwyer, Kevin J.; Baczewski, Andrew D.; Wang, George T.; Butera, Robert E.; Misra, Shashank M.

Abstract not provided.

MRS Bulletin

Bussmann, Ezra B.; Butera, Robert E.; Owen, James H.G.; Randall, John N.; Rinaldi, Steven R.; Baczewski, Andrew D.; Misra, Shashank M.

A materials synthesis method that we call atomic-precision advanced manufacturing (APAM), which is the only known route to tailor silicon nanoelectronics with full 3D atomic precision, is making an impact as a powerful prototyping tool for quantum computing. Quantum computing schemes using atomic (31P) spin qubits are compelling for future scale-up owing to long dephasing times, one- and two-qubit gates nearing high-fidelity thresholds for fault-tolerant quantum error correction, and emerging routes to manufacturing via proven Si foundry techniques. Multiqubit devices are challenging to fabricate by conventional means owing to tight interqubit pitches forced by short-range spin interactions, and APAM offers the required (Å-scale) precision to systematically investigate solutions. However, applying APAM to fabricate circuitry with increasing numbers of qubits will require significant technique development. Here, we provide a tutorial on APAM techniques and materials and highlight its impacts in quantum computing research. Finally, we describe challenges on the path to multiqubit architectures and opportunities for APAM technique development. Graphic Abstract: [Figure not available: see fulltext.]

Koepke, Justin K.; Scrymgeour, David S.; Simonson, Robert J.; Schultz, Peter A.; Baczewski, Andrew D.; Muller, Richard P.; Misra, Shashank M.; Carroll, Malcolm

Abstract not provided.

Koepke, Justin K.; Scrymgeour, David S.; Simonson, Robert J.; Marshall, Michael T.; Ward, Daniel R.; Muller, Richard P.; Schultz, Peter A.; Baczewski, Andrew D.; Carroll, Malcolm; Misra, Shashank M.; Bussmann, Ezra B.

Abstract not provided.

Hansen, Stephanie B.; Kononov, Alina K.; Baczewski, Andrew D.; Hentschel, T H.

Abstract not provided.

Baek, S.B.; Farzani, A.F.; Radue, M.S.R.; Campbell, Quinn C.; Dwyer, K.J.D.; Baczewski, Andrew D.; Mo, Y.M.; Misra, Shashank M.; Butera, R.E.B.

Abstract not provided.

Hansen, Stephanie B.; Hentschel, T H.; Kononov, Alina K.; Baczewski, Andrew D.

Abstract not provided.

Russo, Antonio R.; Baczewski, Andrew D.; Morrison, Benjamin M.; Rudinger, Kenneth M.

Abstract not provided.