A5043665562- Electron and X-Ray Spectroscopy Techniques
- Advanced Electron Microscopy Techniques and Applications
- Semiconductor materials and devices
- Graphene research and applications
- Integrated Circuits and Semiconductor Failure Analysis
- Carbon Nanotubes in Composites
- Advanced Memory and Neural Computing
- Nanowire Synthesis and Applications
- Advancements in Battery Materials
- Ferroelectric and Negative Capacitance Devices
- Thermal properties of materials
- Thermal Radiation and Cooling Technologies
- Electronic and Structural Properties of Oxides
- Advanced Materials Characterization Techniques
- Force Microscopy Techniques and Applications
- Mechanical and Optical Resonators
- Advanced Battery Technologies Research
- Molecular Junctions and Nanostructures
- Surface and Thin Film Phenomena
- Nanopore and Nanochannel Transport Studies
- Advancements in Semiconductor Devices and Circuit Design
- Electrochemical Analysis and Applications
- Advanced Thermoelectric Materials and Devices
- Semiconductor materials and interfaces
- Anodic Oxide Films and Nanostructures
University of California, Los Angeles
2015-2024
California NanoSystems Institute
2015-2024
IntraMedical Imaging (United States)
2022-2024
Colgate University
2014-2018
University of Southern California
2018
University of Central Florida
2013
UCLA Health
2012
Colorado State University
2011
University of California, Berkeley
1994-2006
Lawrence Berkeley National Laboratory
1994-2006
We present the result of our most recent search for $T$ violation in ${}^{205}\mathrm{Tl}$, which is interpreted terms an electric dipole moment electron ${d}_{e}$. find ${d}_{e}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(6.9\ifmmode\pm\else\textpm\fi{}7.4)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}28}e\mathrm{cm}$, yields upper limit $|{d}_{e}|\ensuremath{\le}1.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}27}e\mathrm{cm}$ with $90%$ confidence. The apparatus a...
Abstract Resistive switching (RS) is an interesting property shown by some materials systems that, especially during the last decade, has gained a lot of interest for fabrication electronic devices, with nonvolatile memories being those that have received most attention. The presence and quality RS phenomenon in system can be studied using different prototype cells, performing experiments, displaying figures merit, developing computational analyses. Therefore, real usefulness impact findings...
Modern microelectronic devices have nanoscale features that dissipate power nonuniformly, but fundamental physical limits frustrate efforts to detect the resulting temperature gradients. Contact thermometers disturb of a small system, while radiation struggle beat diffraction limit. Exploiting same physics as Fahrenheit's glass-bulb thermometer, we mapped thermal expansion Joule-heated, 80-nanometer-thick aluminum wires by precisely measuring changes in density. With scanning transmission...
New results are reported in our search for the electric dipole moment ${\mathit{d}}_{\mathit{e}}$ of electron ground 6 $^{2}$${\mathit{P}}_{1/2}$ state $^{205}\mathrm{Tl}$. The atomic-beam magnetic resonance method is employed with separated oscillating fields. A field B defines axis quantization, and an E, parallel to B, applied region between Laser optical pumping used selection analysis, signal fluorescence accompanying decay excited atoms analyzer region. signature a nonzero dependence...
An ideal technique for observing nanoscale assembly would provide atomic-resolution images of both the products and reactants in real time. Using a transmission electron microscope we image situ electrochemical deposition lead from an aqueous solution lead(II) nitrate. Both deposits local Pb(2+) concentration can be visualized. Depending on rate potential change history, cathode structurally compact layer or dendrites. In cases removed process repeated. Asperities that persist through many...
Growth of graphene on copper (100) single crystals by chemical vapor deposition has been accomplished. The atomic structure the overlayer was studied using scanning tunneling microscopy. A detailed analysis moiré superstructures present in topography reveals that growth occurs a variety orientations over square lattice surface. Transmission electron microscopy used to elucidate crystallinity grown graphene. Pristine, defect-free observed steps, corners, and screw dislocations. Distinct...
A model of electrons hopping from atom to in graphene's honeycomb lattice gives low-energy electronic excitations that obey a relation formally identical $2+1$ dimensional Dirac equation. Graphene's spin equivalent, ``pseudospin,'' arises the degeneracy introduced by lattice's two inequivalent atomic sites per unit cell. Previously it has been thought usual electron and pseudospin indexing graphene sublattice state are merely analogues. Here we show is also real angular momentum. This...
Conductive bridge random access memory (CBRAM) is a leading candidate to supersede flash memory, but poor understanding of its switching process impedes widespread implementation. The underlying physics and basic, unresolved issues such as the connecting filament's growth direction can be revealed with direct imaging, nanoscale target region completely encased thus difficult real-time, high-resolution probes. In Pt/Al2O3/Cu CBRAM devices realistic topology, we find that filament grows...
Abstract To study the effects of hydrocarbon precursor gases, graphene is grown by chemical vapor deposition from methane, ethane, and propane on copper foils. The larger molecules are found to more readily produce bilayer multilayer graphene, due a higher carbon concentration different decomposition processes. Single‐ can be with good selectivity in simple, single‐precursor process varying pressure ethane 250 1000 mTorr. AB‐stacked as shown selected area electron diffraction analysis....
Using scanning transmission electron microscopy we image ∼4 nm platinum nanoparticles deposited on an insulating membrane, where the membrane is one of two electron-transparent windows separating aqueous environment from microscope's high vacuum. Upon receiving a relatively moderate dose ∼104 e/nm2, initially immobile begin to move along trajectories that are directed radially outward center field view. With larger rates particle motion becomes increasingly dramatic. These observations...
Single crystals of doped aniline oligomers are produced via a simple solution-based self-assembly method. Detailed mechanistic studies reveal that different morphologies and dimensions can be by "bottom-up" hierarchical assembly where structures such as one-dimensional (1-D) nanofibers aggregated into higher order architectures. A large variety crystalline nanostructures including 1-D nanowires, 2-D nanoribbons nanosheets, 3-D nanoplates, stacked sheets, nanoflowers, porous networks, hollow...
We present a technique based on scanning transmission electron microscopy (STEM) that is capable of probing nanobubble dynamics with nanometer spatial resolution. A vacuum-tight vessel holds sub-micrometer layer water between two electron-transparent dielectric membranes. Electrical current pulses passing through platinum wire one the membranes inject sufficient heat locally to initiate single bubble formation. In absence power input, all bubbles are observed be unstable against collapse,...
Coherent diffractive imaging (CDI) has been widely applied in the physical and biological sciences using synchrotron radiation, XFELs, high harmonic generation, electrons optical lasers. One of CDI's important applications is to probe dynamic phenomena with spatio-temporal resolution. Here, we report development a general situ CDI method for real-time processes solution. By introducing time-invariant overlapping region as real-space constraint, show that can simultaneously reconstruct time...
A detailed kinetic analysis is used to determine the fundamental energy storage properties and rate capabilities of TiO2 nanosheets. These materials exhibit different compared anatase nanocrystals including a shift lower redox potentials for Li+ reversible charge Na+. Nanosheets are intriguing applications due fact that nearly entire surface material, specific crystal facets, can be exposed electrolyte.
The lithium-ion battery is currently the preferred power source for applications ranging from smart phones to electric vehicles. Imaging chemical reactions governing its function as they happen, with nanoscale spatial resolution and specificity, a long-standing open problem. Here, we demonstrate operando spectrum imaging of Li-ion anode over multiple charge-discharge cycles using electron energy-loss spectroscopy (EELS) in scanning transmission microscope (STEM). Using ultrathin cells,...
Transmission electron microscopy excels at determining a sample's physical structure---the locations and identities of its constituent atoms---, but is typically blind to electronic structure. A combination electron-beam-induced current (EBIC) imaging with scanning transmission (STEM), however, does reveal properties by detecting the emission both secondary electrons corresponding holes, for differential contrast that otherwise inaccessible. Thus STEM EBIC can provide high-resolution images...
Abstract Advanced nanomaterials are at the core of innovation for microelectronics industry. Designing, characterizing, and testing two-terminal devices, such as metal-insulator-metal structures, is key to improving material stack design integration. Electrical biasing within in situ transmission electron microscopy using MEMS-based platforms a promising technique nano-characterization under operando conditions. However, conventional focused ion beam sample preparation can introduce...
Graphene's structure bears on both the material's electronic properties and fundamental questions about long range order in two-dimensional crystals. We present an analytic calculation of selected area electron diffraction from multi-layer graphene compare it with data samples prepared by chemical vapor deposition mechanical exfoliation. A single layer scatters only 0.5% incident electrons, so this kinematical can be considered reliable for five or fewer layers. Dark-field transmission...
We have constructed and operated a nanoscale linear motor powered by single metal nanocrystal ram sandwiched between mechanical lever arms. Low-level electrical voltages applied to the carbon nanotube arms cause grow or shrink in controlled manner. The length of is adjustable from 0 more than 150 nm, with extension speeds exceeding 1900 nm/s. thermodynamic principles governing operation resemble those driving frost heave, natural solid-state motor.
Live imaging of operating multiwall carbon nanotube (MWCNT-) based electronic devices is performed by high resolution transmission electron microscopy. Our measurements allow us to correlate transport with changes in device structure. Surface contamination, contact annealing, and sequential wall removal are observed. Temperature profiles confirm diffusive conduction MWCNTs the bias limit. This technique provides a general platform for studying nanoscale systems, where geometric configuration...
Because of its linear dependence on length scale, surface tension can be a dominant force for small systems. Properly harnessed, this is uniquely suited nanomechanical applications. We have developed nanoelectromechanical relaxation oscillator with surface-tension-driven power stroke. The consists two liquid metal droplets exchanging mass, and frequency directly controlled low-level dc electrical voltage.