A5030169722- Graphene research and applications
- Carbon Nanotubes in Composites
- Boron and Carbon Nanomaterials Research
- Quantum and electron transport phenomena
- Molecular Junctions and Nanostructures
- 2D Materials and Applications
- Physics of Superconductivity and Magnetism
- Organic and Molecular Conductors Research
- Fullerene Chemistry and Applications
- Mechanical and Optical Resonators
- Diamond and Carbon-based Materials Research
- Force Microscopy Techniques and Applications
- MXene and MAX Phase Materials
- Advanced Condensed Matter Physics
- Topological Materials and Phenomena
- Advanced Electron Microscopy Techniques and Applications
- Electron and X-Ray Spectroscopy Techniques
- High-pressure geophysics and materials
- Surface and Thin Film Phenomena
- Magnetic and transport properties of perovskites and related materials
- Iron-based superconductors research
- Thermal properties of materials
- Superconductivity in MgB2 and Alloys
- Solid-state spectroscopy and crystallography
- Gas Sensing Nanomaterials and Sensors
Lawrence Berkeley National Laboratory
2016-2025
University of California, Berkeley
2016-2025
Kavli Energy NanoScience Institute
2016-2025
Max Planck Society
2020
Max Planck Institute for Plasma Physics
2020
Material Sciences (United States)
2003-2014
University of California System
2006-2014
Berkeley College
2011-2014
Howard Hughes Medical Institute
2006-2009
University of California, San Francisco
2009
The successful synthesis of pure boron nitride (BN) nanotubes is reported here. Multi-walled tubes with inner diameters on the order 1 to 3 nanometers and lengths up 200 were produced in a carbon-free plasma discharge between BN-packed tungsten rod cooled copper electrode. Electron energy-loss spectroscopy individual yielded B:N ratios approximately 1, which consistent theoretical predictions stable BN tube structures.
The electronic properties of single-walled carbon nanotubes are shown here to be extremely sensitive the chemical environment. Exposure air or oxygen dramatically influences nanotubes' electrical resistance, thermoelectric power, and local density states, as determined by transport measurements scanning tunneling spectroscopy. These parameters can reversibly "tuned" surprisingly small concentrations adsorbed gases, an apparently semiconducting nanotube converted into apparent metal through...
Bimetallic platinum-nickel (Pt-Ni) nanostructures represent an emerging class of electrocatalysts for oxygen reduction reaction (ORR) in fuel cells, but practical applications have been limited by catalytic activity and durability. We surface-doped Pt3Ni octahedra supported on carbon with transition metals, termed M-Pt3Ni/C, where M is vanadium, chromium, manganese, iron, cobalt, molybdenum (Mo), tungsten, or rhenium. The Mo-Pt3Ni/C showed the best ORR performance, a specific 10.3 mA/cm(2)...
Two-dimensional graphene monolayers and bilayers exhibit fascinating electrical transport behaviors. Using infrared spectroscopy, we find that they also have strong interband transitions their optical can be substantially modified through gating, much like in field-effect transistors. This gate dependence of adds a valuable dimension for optically probing band structure. For monolayer, it yields directly the linear dispersion Dirac fermions, whereas bilayer, reveals dominating van Hove...
The local atomic structure of graphene oxide (GO) and reduced annealed (raGO) is determined via ultra-high-resolution transmission electron microscopy. We find that the proposed desired return to from GO not possible through synthetic route employed. detailed GO, previously unknown, revealed as mottled, with few square nanometer graphitic regions separated by highly oxidized regions.
The electrical properties of individual bundles, or "ropes," single-walled carbon nanotubes have been measured. Below about 10 kelvin, the low-bias conductance was suppressed for voltages less than a few millivolts. In addition, dramatic peaks were observed in as function gate voltage that modulated number electrons rope. These results are interpreted terms single-electron charging and resonant tunneling through quantized energy levels composing
We demonstrate the controlled and reversible telescopic extension of multiwall carbon nanotubes, thus realizing ultralow-friction nanoscale linear bearings constant-force nanosprings. Measurements performed in situ on individual custom-engineered nanotubes inside a high-resolution transmission electron microscope demonstrated anticipated van der Waals energy–based retraction force enabled us to place quantitative limits static dynamic interwall frictional forces between nested nanotubes....
Although the physics of materials at surfaces and edges has been extensively studied, movement individual atoms an isolated edge not directly observed in real time. With a transmission electron aberration-corrected microscope capable simultaneous atomic spatial resolution 1-second temporal resolution, we produced movies dynamics carbon hole suspended, single layer graphene. The rearrangement bonds beam-induced ejection are recorded as grows. We investigated mechanism reconstruction...
Junctions consisting of two crossed single-walled carbon nanotubes were fabricated with electrical contacts at each end nanotube. The individual identified as metallic (M) or semiconducting (S), based on their two-terminal conductances; MM, MS, and SS four-terminal devices studied. MM junctions had high conductances, the order 0.1 e(2)/h (where e is electron charge h Planck's constant). For an MS junction, nanotube was depleted junction by nanotube, forming a rectifying Schottky barrier. We...
We present a transmission electron microscopy investigation of graphene membranes, crystalline foils with thickness only 1 atom. By using aberration-correction in combination monochromator, 1-A resolution is achieved at an acceleration voltage 80 kV. The low crucial for the stability these membranes. As result, every individual carbon atom field view detected and resolved. observe highly lattice along occasional point defects. formation annealing Stone-Wales defects observed situ. Multiple...
Nanoimaged Polaritons Engineered heterostructures consisting of thin, weakly bound layers can exhibit many attractive electronic properties. Dai et al. (p. 1125 ) used infrared nanoimaging on the surface hexagonal boron nitride crystals to detect phonon polaritons, collective modes that originate in coupling photons optical phonons. The findings reveal dependence polariton wavelength and dispersion thickness material down just a few atomic layers.
We have measured the temperature-dependent thermal conductivity $\ensuremath{\kappa}(T)$ of crystalline ropes single-walled carbon nanotubes from 350 K to 8 K. decreases smoothly with decreasing temperature, and displays linear temperature dependence below 30 Comparison electrical experiments indicates that room-temperature a single nanotube may be comparable diamond or in-plane graphite, while ratio conductance for given sample is dominated by phonons at all temperatures. Below K, estimated...
We introduce a new type of liquid cell for in situ transmission electron microscopy (TEM) based on entrapment film between layers graphene. The graphene facilitates atomic-level resolution imaging while sustaining the most realistic conditions achievable under electron-beam radiation. employ this to explore mechanism colloidal platinum nanocrystal growth. Direct atomic-resolution allows us visualize critical steps process, including site-selective coalescence, structural reshaping after and...
We demonstrated nanoscale solid-state thermal rectification. High-thermal-conductivity carbon and boron nitride nanotubes were mass-loaded externally inhomogeneously with heavy molecules. The resulting system yields asymmetric axial conductance greater heat flow in the direction of decreasing mass density. effect cannot be explained by ordinary perturbative wave theories, instead we suggest that solitons may responsible for phenomenon. Considering important role electrical rectifiers...
We describe the synthesis of very thin sheets (between a few and ten atomic layers) hexagonal boron nitride (h-BN), prepared either on SiO2 substrate or freely suspended. Optical microscopy, force transmission electron microscopy have been used to characterize morphology samples distinguish between regions different thicknesses. Comparison is made previous studies single- few-layer graphene. This opens door experimentally accessing two-dimensional phase nitride.
A scanning tunneling microscope (STM) was used to explore the local electrical characteristics of single-wall carbon nanotubes. As STM tip moved along length nanotubes, well-defined positions were found where transport current changes abruptly from a graphitic-like response one that is highly nonlinear and asymmetrical, including near-perfect rectification. The observations are consistent with existence localized, on-tube nanodevices type proposed theoretically.