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Article: A Model for Atomic Precision p-Type Doping with Diborane on Si(100)-2×1

Campbell, Quinn / Ivie, Jeffrey A / Bussmann, Ezra / Schmucker, Scott W / Baczewski, Andrew D / Misra, Shashank

Journal of physical chemistry. 2021 Jan. 06, v. 125, no. 1

2021

Abstract: Diborane (B₂H₆) is a promising molecular precursor for atomic precision p-type doping of silicon that has recently been experimentally demonstrated [ŠkereňNat. Electron.2020]. We use density functional theory (DFT) calculations to determine the reaction ... ...

Abstract	Diborane (B₂H₆) is a promising molecular precursor for atomic precision p-type doping of silicon that has recently been experimentally demonstrated [ŠkereňNat. 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.
Keywords	Monte Carlo method ; adsorption ; ambient temperature ; boron ; density functional theory ; dissociation ; energy ; geometry ; halogens ; heat ; hydrogen ; models ; silicon
Language	English
Dates of publication	2021-0106
Size	p. 481-488.
Publishing place	American Chemical Society
Document type	Article
Note	NAL-AP-2-clean
ISSN	1932-7455
DOI	10.1021/acs.jpcc.0c08919
Database	NAL-Catalogue (AGRICOLA)

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Book ; Online: Utilizing multimodal microscopy to reconstruct Si/SiGe interfacial atomic disorder and infer its impacts on qubit variability

Peña, Luis Fabián / Koepke, Justine C. / Dycus, J. Houston / Mounce, Andrew / Baczewski, Andrew D. / Jacobson, N. Tobias / Bussmann, Ezra

2023

Abstract: SiGe heteroepitaxial growth yields pristine host material for quantum dot qubits, but residual interface disorder can lead to qubit-to-qubit variability that might pose an obstacle to reliable SiGe-based quantum computing. We demonstrate a technique to ... ...

Abstract	SiGe heteroepitaxial growth yields pristine host material for quantum dot qubits, but residual interface disorder can lead to qubit-to-qubit variability that might pose an obstacle to reliable SiGe-based quantum computing. We demonstrate a technique to reconstruct 3D interfacial atomic structure spanning multiqubit areas by combining data from two verifiably atomic-resolution microscopy techniques. Utilizing scanning tunneling microscopy (STM) to track molecular beam epitaxy (MBE) growth, we image surface atomic structure following deposition of each heterostructure layer revealing nanosized SiGe undulations, disordered strained-Si atomic steps, and nonconformal uncorrelated roughness between interfaces. Since phenomena such as atomic intermixing during subsequent overgrowth inevitably modify interfaces, we measure post-growth structure via cross-sectional high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). Features such as nanosized roughness remain intact, but atomic step structure is indiscernible in $1.0\pm 0.4$~nm-wide intermixing at interfaces. Convolving STM and HAADF-STEM data yields 3D structures capturing interface roughness and intermixing. We utilize the structures in an atomistic multivalley effective mass theory to quantify qubit spectral variability. The results indicate (1) appreciable valley splitting (VS) variability of roughly $\pm$ $50\%$ owing to alloy disorder, and (2) roughness-induced double-dot detuning bias energy variability of order $1-10$ meV depending on well thickness. For measured intermixing, atomic steps have negligible influence on VS, and uncorrelated roughness causes spatially fluctuating energy biases in double-dot detunings potentially incorrectly attributed to charge disorder. Comment: 12 pages, 6 figures
Keywords	Condensed Matter - Materials Science
Subject code	530
Publishing date	2023-06-27
Publishing country	us
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Electric current paths in a Si:P delta-doped device imaged by nitrogen-vacancy diamond magnetic microscopy.

Basso, Luca / Kehayias, Pauli / Henshaw, Jacob / Saleh Ziabari, Maziar / Byeon, Heejun / Lilly, Michael P / Bussmann, Ezra / Campbell, Deanna M / Misra, Shashank / Mounce, Andrew M

Nanotechnology

2022 Volume 34, Issue 1

Abstract: The recently-developed ability to control phosphorous-doping of silicon at an atomic level using scanning tunneling microscopy, a technique known as atomic precision advanced manufacturing (APAM), has allowed us to tailor electronic devices with atomic ... ...

Abstract	The recently-developed ability to control phosphorous-doping of silicon at an atomic level using scanning tunneling microscopy, a technique known as atomic precision advanced manufacturing (APAM), has allowed us to tailor electronic devices with atomic precision, and thus has emerged as a way to explore new possibilities in Si electronics. In these applications, critical questions include where current flow is actually occurring in or near APAM structures as well as whether leakage currents are present. In general, detection and mapping of current flow in APAM structures are valuable diagnostic tools to obtain reliable devices in digital-enhanced applications. In this paper, we used nitrogen-vacancy (NV) centers in diamond for wide-field magnetic imaging (with a few-mm field of view and micron-scale resolution) of magnetic fields from surface currents flowing in an APAM test device made of a P delta-doped layer on a Si substrate, a standard APAM witness material. We integrated a diamond having a surface NV ensemble with the device (patterned in two parallel mm-sized ribbons), then mapped the magnetic field from the DC current injected in the APAM device in a home-built NV wide-field microscope. The 2D magnetic field maps were used to reconstruct the surface current densities, allowing us to obtain information on current paths, device failures such as choke points where current flow is impeded, and current leakages outside the APAM-defined P-doped regions. Analysis on the current density reconstructed map showed a projected sensitivity of ∼0.03 A m
Language	English
Publishing date	2022-10-20
Publishing country	England
Document type	Journal Article
ZDB-ID	1362365-5
ISSN	1361-6528 ; 0957-4484
ISSN (online)	1361-6528
ISSN	0957-4484
DOI	10.1088/1361-6528/ac95a0
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Book ; Online: A model for atomic precision p-type doping with diborane on Si(100)-2$\times$1

Campbell, Quinn / Ivie, Jeffrey A. / Bussmann, Ezra / Schmucker, Scott W. / Baczewki, Andrew D. / Misra, Shashank

2020

Abstract: Diborane (B$_2$H$_6$) is a promising molecular precursor for atomic precision p-type doping of silicon that has recently been experimentally demonstrated [T. {\v{S}}kere{\v{n}}, \textit{et al.,} Nature Electronics (2020)]. We use density functional ... ...

Abstract	Diborane (B$_2$H$_6$) is a promising molecular precursor for atomic precision p-type doping of silicon that has recently been experimentally demonstrated [T. {\v{S}}kere{\v{n}}, \textit{et al.,} Nature Electronics (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$\times$1 surface. Our calculations indicate that diborane must overcome an energy barrier to adsorb, explaining the experimentally observed low sticking coefficient ($< 10^{-4}$ at room temperature) and suggesting that heating can be used to increase the adsorption rate. Upon sticking, diborane has an $\sim 50\%$ chance of splitting into two BH$_3$ fragments versus merely losing hydrogen to form a dimer such as B$_2$H$_4$. 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. Comment: 24 pages, 6 figures
Keywords	Condensed Matter - Materials Science ; Quantum Physics
Subject code	541
Publishing date	2020-09-30
Publishing country	us
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Fabrication and field emission properties of vertical, tapered GaN nanowires etched via phosphoric acid.

Kazanowska, Barbara A / Sapkota, Keshab R / Lu, Ping / Talin, A Alec / Bussmann, Ezra / Ohta, Taisuke / Gunning, Brendan P / Jones, Kevin S / Wang, George T

Nanotechnology

2021 Volume 33, Issue 3

Abstract: The controlled fabrication of vertical, tapered, and high-aspect ratio GaN nanowires via a two-step top-down process consisting of an inductively coupled plasma reactive ion etch followed by a hot, 85% ... ...

Abstract	The controlled fabrication of vertical, tapered, and high-aspect ratio GaN nanowires via a two-step top-down process consisting of an inductively coupled plasma reactive ion etch followed by a hot, 85% H
Language	English
Publishing date	2021-10-27
Publishing country	England
Document type	Journal Article
ZDB-ID	1362365-5
ISSN	1361-6528 ; 0957-4484
ISSN (online)	1361-6528
ISSN	0957-4484
DOI	10.1088/1361-6528/ac2981
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article: AlCl₃-Dosed Si(100)-2 × 1: Adsorbates, Chlorinated Al Chains, and Incorporated Al

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

Journal of physical chemistry. 2021 May 19, v. 125, no. 21

2021

Abstract: 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 ... ...

Abstract	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.
Keywords	X-ray photoelectron spectroscopy ; adsorption ; aluminum ; ambient temperature ; density functional theory ; desorption ; mass spectrometry ; models
Language	English
Dates of publication	2021-0519
Size	p. 11336-11347.
Publishing place	American Chemical Society
Document type	Article
Note	NAL-AP-2-clean
ISSN	1932-7455
DOI	10.1021/acs.jpcc.1c00691
Database	NAL-Catalogue (AGRICOLA)

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Book ; Online: Current Paths in an Atomic Precision Advanced Manufactured Device Imaged by Nitrogen-Vacancy Diamond Magnetic Microscopy

Basso, Luca / Kehayias, Pauli / Henshaw, Jacob / Ziabari, Maziar Saleh / Byeon, Heejun / Lilly, Michael P. / Bussmann, Ezra / Campbell, Deanna M. / Misra, Shashank / Mounce, Andrew M.

2022

Abstract: The recently-developed ability to control phosphorous-doping of silicon at an atomic level using scanning tunneling microscopy (STM), a technique known as atomic-precision-advanced-manufacturing (APAM), has allowed us to tailor electronic devices with ... ...

Abstract	The recently-developed ability to control phosphorous-doping of silicon at an atomic level using scanning tunneling microscopy (STM), a technique known as atomic-precision-advanced-manufacturing (APAM), has allowed us to tailor electronic devices with atomic precision, and thus has emerged as a way to explore new possibilities in Si electronics. In these applications, critical questions include where current flow is actually occurring in or near APAM structures as well as whether leakage currents are present. In general, detection and mapping of current flow in APAM structures are valuable diagnostic tools to obtain reliable devices in digital-enhanced applications. In this paper, we performed nitrogen-vacancy (NV) wide-field magnetic imaging of stray magnetic fields from surface current densities flowing in an APAM test device over a mm-field of view with {\mu}m-resolution. To do this, we integrated a diamond having a surface NV ensemble with the device (patterned in two parallel mm-sized ribbons), then mapped the magnetic field from the DC current injected in the APAM device in a home-built NV wide-field microscope. The 2D magnetic field maps were used to reconstruct the surface current density, allowing us to obtain information on current paths, device failures such as choke points where current flow is impeded, and current leakages outside the APAM-defined P-doped regions. Analysis on the current density reconstructed map showed a projected sensitivity of ~0.03 A/m, corresponding to a smallest detectable current in the 200 {\mu}m-wide APAM ribbon of ~6 {\mu}A. These results demonstrate the failure analysis capability of NV wide-field magnetometry for APAM materials, opening the possibility to investigate other cutting-edge microelectronic devices.
Keywords	Physics - Applied Physics ; Physics - Instrumentation and Detectors ; Quantum Physics
Subject code	621 ; 530
Publishing date	2022-07-28
Publishing country	us
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Book ; Online: Robust incorporation in multi-donor patches created using atomic-precision advanced manufacturing

Campbell, Quinn / Koepke, Justine C. / Ivie, Jeffrey A. / Mounce, Andrew M. / Ward, Daniel R. / Carroll, Malcolm S. / Misra, Shashank / Baczewski, Andrew D. / Bussmann, Ezra

2022

Abstract: Atomic-precision advanced manufacturing enables the placement of dopant atoms within $\pm$1 lattice site in crystalline Si. However, it has recently been shown that reaction kinetics can introduce uncertainty in whether a single donor will incorporate at ...

Abstract	Atomic-precision advanced manufacturing enables the placement of dopant atoms within $\pm$1 lattice site in crystalline Si. However, it has recently been shown that reaction kinetics can introduce uncertainty in whether a single donor will incorporate at all in a minimal 3-dimer lithographic window. In this work, we explore the combined impact of lithographic variation and stochastic kinetics on P incorporation as the size of such a window is increased. We augment a kinetic model for PH$_3$ dissociation leading to P incorporation on Si(100)-2$\times$1 to include barriers for reactions across distinct dimer rows. Using this model, we demonstrate that even for a window consisting of 2$\times$3 silicon dimers, the probability that at least one donor incorporates is nearly unity. We also examine the impact of size of the lithographic window, finding that the incorporation fraction saturates to $\delta$-layer like coverage as the circumference-to-area ratio approaches zero. We predict that this incorporation fraction depends strongly on the dosage of the precursor, and that the standard deviation of the number of incorporations scales as $\sim \sqrt{n}$, as would be expected for a series of largely independent incorporation events. Finally, we characterize an array of experimentally prepared multi-donor lithographic windows and use our kinetic model to study variability due to the observed lithographic roughness, predicting a negligible impact on incorporation statistics. We find good agreement between our model and the inferred incorporation in these windows from scanning tunneling microscope measurements, indicating the robustness of atomic-precision advanced manufacturing to errors in patterning for multi-donor patches. Comment: Main text 24 pages, 5 figures + Appendecies 8 pages, 3 figures
Keywords	Condensed Matter - Mesoscale and Nanoscale Physics ; Condensed Matter - Materials Science
Subject code	612
Publishing date	2022-07-21
Publishing country	us
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Book ; Online: AlCl$_{3}$-dosed Si(100)-2$\times$1

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

Adsorbates, chlorinated Al chains, and incorporated Al

2021

Abstract: The adsorption of AlCl$_{3}$ on Si(100) and the effect of annealing the AlCl$_{3}$-dosed substrate was studied to reveal key surface processes for the development of atomic-precision acceptor-doping techniques. This investigation was performed via ... ...

Abstract	The adsorption of AlCl$_{3}$ on Si(100) and the effect of annealing the AlCl$_{3}$-dosed substrate was 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, AlCl$_{3}$ readily adsorbed to the Si substrate dimers and dissociated to form a variety of species. Annealing of the AlCl$_{3}$-dosed substrate at temperatures below 450 $^{\circ}$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 $^{\circ}$C and above, and Cl desorption was observed for temperatures beyond 450 $^{\circ}$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 10$^{20}$ cm$^{-3}$ across a $\sim$2.7 nm thick $\delta$-doped region. The Al concentration achieved here and the processing parameters utilized promote AlCl$_{3}$ as a viable gaseous precursor for novel acceptor-doped Si materials and devices for quantum computing. Comment: 35 pages, 8 figures
Keywords	Condensed Matter - Materials Science ; Physics - Chemical Physics
Subject code	530
Publishing date	2021-01-22
Publishing country	us
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Book ; Online: Atomic Precision Advanced Manufacturing for Digital Electronics

Ward, Daniel R. / Schmucker, Scott W. / Anderson, Evan M. / Bussmann, Ezra / Tracy, Lisa / Lu, Tzu-Ming / Maurer, Leon N. / Baczewski, Andrew / Campbell, Deanna M. / Marshall, Michael T. / Misra, Shashank

2020

Abstract: An exponential increase in the performance of silicon microelectronics and the demand to manufacture in great volumes has created an ecosystem that requires increasingly complex tools to fabricate and characterize the next generation of chips. However, ... ...

Abstract	An exponential increase in the performance of silicon microelectronics and the demand to manufacture in great volumes has created an ecosystem that requires increasingly complex tools to fabricate and characterize the next generation of chips. However, the cost to develop and produce the next generation of these tools has also risen exponentially, to the point where the risk associated with progressing to smaller feature sizes has created pain points throughout the ecosystem. The present challenge includes shrinking the smallest features from nanometers to atoms (10 nm corresponds to 30 silicon atoms). Relaxing the requirement for achieving scalable manufacturing creates the opportunity to evaluate ideas not one or two generations into the future, but at the absolute physical limit of atoms themselves. This article describes recent advances in atomic precision advanced manufacturing (APAM) that open the possibility of exploring opportunities in digital electronics. Doing so will require advancing the complexity of APAM devices and integrating APAM with CMOS.
Keywords	Physics - Applied Physics ; Condensed Matter - Mesoscale and Nanoscale Physics ; Condensed Matter - Materials Science
Subject code	621
Publishing date	2020-02-25
Publishing country	us
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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