A5091194643- Semiconductor materials and devices
- Surface and Thin Film Phenomena
- Force Microscopy Techniques and Applications
- Electron and X-Ray Spectroscopy Techniques
- Molecular Junctions and Nanostructures
- Advancements in Semiconductor Devices and Circuit Design
- Electronic and Structural Properties of Oxides
- Advanced Materials Characterization Techniques
- Semiconductor materials and interfaces
- Integrated Circuits and Semiconductor Failure Analysis
- Quantum and electron transport phenomena
- Semiconductor Quantum Structures and Devices
- Silicon and Solar Cell Technologies
- Diamond and Carbon-based Materials Research
- Advanced Electron Microscopy Techniques and Applications
- Nanowire Synthesis and Applications
- Copper Interconnects and Reliability
- Advanced Memory and Neural Computing
- Magnetic properties of thin films
- Metal and Thin Film Mechanics
- nanoparticles nucleation surface interactions
- Photonic and Optical Devices
- Silicon Nanostructures and Photoluminescence
- Advanced Surface Polishing Techniques
- Mechanical and Optical Resonators
Sandia National Laboratories
2014-2024
Center for Integrated Nanotechnologies
2017-2024
Sandia National Laboratories California
2009-2021
Centre Interdisciplinaire de Nanoscience de Marseille
2010-2016
Aix-Marseille Université
2011-2016
Centre National de la Recherche Scientifique
2010-2012
University of Utah
2004-2007
Utah State University
2004
Beloit College
2001
Siemens (Germany)
1989-1991
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 reliable SiGe-based computing. By convolving data from scanning tunneling microscopy and high-angle annular dark field transmission electron microscopy, we reconstruct 3D interfacial atomic structure employ atomistic multi-valley effective mass theory quantify qubit spectral variability. The results...
Using low-energy electron microscopy movies, we have measured the dewetting dynamics of single-crystal Si(001) thin films on SiO2 substrates. During annealing (T>700 °C), voids open in Si, exposing oxide. The grow, evolving Si fingers that subsequently break apart into self-organized three-dimensional (3D) nanocrystals. A kinetic Monte Carlo model incorporating surface and interfacial free energies reproduces all salient features morphological evolution. is described using an analytic...
Using low-energy electron microscopy (LEEM), we have measured, in real time, the dewetting of single-crystal Si(001) thin films on amorphous silicon dioxide substrates, which transforms two-dimensional (2D) film into three-dimensional (3D) compact Si nanocrystals. The scenario has been reported by Bussmann et al. [New J. Phys. 13, 043017 (2011)]. Analytic 2D and 3D models based simple approximate geometries front developed to analyze LEEM measurements. They enable us estimate driving force...
Spin states in semiconductors provide exceptionally stable and noise-resistant environments for qubits, positioning them as optimal candidates reliable quantum computing technologies. The proposal to use nuclear electronic spins of donor atoms silicon, introduced by Kane 1998, sparked a new research field focused on the precise individual impurity devices, utilising scanning tunnelling microscopy ion implantation. This roadmap article reviews advancements 25 years since Kane's proposal,...
Abstract Spin states in semiconductors provide exceptionally stable and noise-resistant environments for qubits, positioning them as optimal candidates reliable quantum computing technologies. The proposal to use nuclear electronic spins of donor atoms silicon, introduced by Kane 1998, sparked a new research field focused on the precise individual impurity devices, utilising scanning tunnelling microscopy ion implantation. This roadmap article reviews advancements 25 years since Kane’s...
Silicon processing techniques such as atomic precision advanced manufacturing (APAM) and epitaxial growth require surface preparations that activate oxide desorption (typically >1000 $^{\circ}$C) promote reconstruction toward atomically-clean, flat, ordered Si(100)-2$\times$1. We compare aqueous vapor phase cleaning of Si Si/SiGe surfaces to prepare APAM-ready epitaxy-ready at lower temperatures. Angle resolved X-ray photoelectron spectroscopy (ARXPS) Fourier transform infrared (FTIR)...
Abstract 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, making an impact as a powerful prototyping tool for quantum computing. Quantum computing schemes using ( 31 P) spin qubits are compelling future scale-up owing long dephasing times, one- and two-qubit gates nearing high-fidelity thresholds fault-tolerant error correction, emerging routes via proven Si...
Scanning tunneling microscope lithography can be used to create nanoelectronic devices in which dopant atoms are precisely positioned a $\mathrm{Si}$ lattice within approximately $1$ nm of target position. This exquisite precision is promising for realizing various quantum technologies. However, potentially impactful form disorder due incorporation kinetics, the number P that incorporate into single lithographic window manifestly uncertain. We present experimental results indicating...
Sub-10 nm resolution can be obtained in scanning capacitance microscopy (SCM) if the probe tip is approximately of same size. Such observed, although infrequently, with present commercially available probes. To acquire routine sub-10 resolution, a solid Pt metal has been developed radius. The demonstrated by SCM imaging on cross-sectioned 70 gatelength field-effect transistor (FET), shallow implant (n+/p, 24 junction depth), and an epitaxial staircase (p, ∼75 steps). FET device over abrupt...
We show that a scanning capacitance microscope (SCM) can image buried delta-doped donor nanostructures fabricated in Si via recently developed atomic-precision tunneling microscopy (STM) lithography technique. A critical challenge completing nanoelectronic devices is to accurately align mesoscopic metal contacts the STM defined nanostructures. Utilizing SCMs ability dopant nanostructures, we have technique by which are able position electrodes on surface form underlying with measured...
We describe an all-optical lithography process that can make electrical contact to nanometer-precision donor devices fabricated in silicon using scanning tunneling microscopy (STM). This is accomplished by implementing a cleaning procedure the STM allows integration of metal alignment marks and ion-implanted contacts at wafer level. Low-temperature transport measurements patterned device establish viability process.
Abstract The ability to place atoms one by at specific atomic sites was first used create functioning electronic devices in the late 1990s. Since then, process known as precision advanced manufacturing (APAM) has been further developed and both academic commercial interest its potential grown. This article describes nuances of process, explaining that it places dopants into silicon using surface chemistry, a mechanism not typically microfabrication. It also discusses ongoing efforts develop...
A tunneling spectroscopy technique to measure the energy level of an electronic state in a completely nonconducting surface is demonstrated. Spectroscopy performed by electrostatic force detection single-electron between scanning probe and as function applied voltage. An near SiO2 film found 5.5±0.2eV below conduction band edge. random telegraph signal, caused sporadic back-and-forth tunneling, observed Fermi passes through energy.
The adsorption of AlCl$_{3}$ on Si(100) and the effect annealing AlCl$_{3}$-dosed substrate was studied to reveal key surface processes for development atomic-precision acceptor-doping techniques. This investigation performed via scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), density functional theory (DFT) calculations. At room temperature, readily adsorbed Si dimers dissociated form a variety species. Annealing at temperatures below 450 $^{\circ}$C produced...
The controlled fabrication of vertical, tapered, and high-aspect ratio GaN nanowires via a two-step top-down process consisting an inductively coupled plasma reactive ion etch followed by hot, 85% H3PO4crystallographic wet is explored. vertical are oriented in the[0001]direction bound sidewalls comprising of{336¯2}semipolar planes which at 12° angle from the [0001] axis. High temperature H3PO4etching between 60 °C 95 result smooth semipolar faceting with no visible micro-faceting, whereas 50...
Diborane (B2H6) is a promising molecular precursor for atomic precision p-type doping of silicon that has recently been experimentally demonstrated [Škereň Nat. Electron. 2020]. We use density functional theory (DFT) calculations to determine the reaction pathway diborane dissociating into species will incorporate as electrically active substitutional boron after adsorbing onto Si(100)-2×1 surface. Our indicate must overcome an energy barrier adsorb, explaining observed low sticking...
Single-electron tunneling events between a metal probe and an insulator surface are measured by frequency detection electrostatic force microscopy. typically cause 1–10Hz shifts in the 300kHz resonance of oscillating probe. The appear only within sub-2nm tip–sample gap their magnitude is roughly uniform under fixed experimental conditions. An model probe–sample system yields results consistent with measurements.
Using low-energy electron microscopy (LEEM), we investigate the ultrahigh vacuum annealing of silicon-on-insulator (SOI) samples capped by a chemically-prepared oxide layer. Consistent with previous reports: (1) for T > 750°C, capping-oxide decomposes void nucleation and growth, then (2) 850°C, Si thin-film dewets from SiO2 substrate. Here, show that morphological evolution surface during dewetting process is dependent on preparation SOI surface. Two pathways are evident in recent...
In this paper, we present a brief survey of stress effects on dewetting. For purpose, i) develop simple thermodynamic model to illustrate effects; ii) study in strained–Silicon–On–Insulator (s–SOI) thin films by means Low Energy Electron Microscopy, and Atomic Force Microscopy; iii) discuss some available data. particular, show that while for s–SOI the strain only provides relatively small contribution total driving force dewetting, other cases can really dominate
Using scanning tunneling microscopy, we determine that the one-dimensional diffusion of Si adatoms along Si(111)-(5 x 2)-Au surface reconstruction occurs by a defect-mediated mechanism. Distinctive statistics, especially correlations between sequential adatom displacements, imply displacements are triggered an interaction with defect is localized to adatom. The intrinsic and thermally activated. measured statistics modeled accurately Monte Carlo simulation. activation barrier 1.24 +/- 0.08 eV.
The thermal decomposition of Si dioxide layers formed by wet chemical treatment on Si(001) has been studied low-energy electron microscopy. Independent nucleations voids occur into the oxide that open reaction at void periphery. Depending voids, rates exhibit large differences via occurrence a nonlinear growth radius. This non-steady state regime is attributed to accumulation defects and silicon hydroxyl species SiO2/Si interface enhances
Localized electronic states near a nonconducting SiO(2) surface are imaged on approximately 1 nm scale by single-electron tunneling between the and scanning probe tip. Each electron is detected electrostatic force. The images represent number of electrons at each spatial location. resolution single force microscope determined quantum mechanical tunneling, providing new atomic-scale access to in dielectric surfaces nanostructures.