A5069634247- Graphene research and applications
- Quantum and electron transport phenomena
- Carbon Nanotubes in Composites
- Quantum Dots Synthesis And Properties
- Copper-based nanomaterials and applications
- Advanced Electron Microscopy Techniques and Applications
- Topological Materials and Phenomena
- Mechanical and Optical Resonators
- Electron and X-Ray Spectroscopy Techniques
- Nanowire Synthesis and Applications
- Thermal Radiation and Cooling Technologies
- Graphene and Nanomaterials Applications
- ZnO doping and properties
- Silicon and Solar Cell Technologies
- Plasmonic and Surface Plasmon Research
- Gold and Silver Nanoparticles Synthesis and Applications
- Diamond and Carbon-based Materials Research
- Micro and Nano Robotics
- Chalcogenide Semiconductor Thin Films
- Advancements in Battery Materials
- 2D Materials and Applications
- Biomimetic flight and propulsion mechanisms
- Aerospace Engineering and Energy Systems
- Electronic and Structural Properties of Oxides
- Semiconductor materials and devices
Advanced Research Projects Agency - Energy
2019
University of California, Berkeley
2010-2016
Lawrence Berkeley National Laboratory
2010-2015
United States Department of Energy
2015
Cornell University
2008
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.
Anticorrosion and antioxidation surface treatments such as paint or anodization are a foundational component in nearly all industries. Graphene, single-atom-thick sheet of carbon with impressive impermeability to gases, seems hold promise an effective anticorrosion barrier, recent work supports this hope. We perform complete study the short- long-term performance graphene coatings for Cu Si substrates. Our reveals that although indeed offers short-term oxidation protection, over long time...
We report direct mapping of the grains and grain boundaries (GBs) large-area monolayer polycrystalline graphene sheets, at large (several micrometer) single-atom length scales. Global GB is performed using electron diffraction in scanning transmission microscopy (STEM) or dark-field imaging conventional TEM. Additionally, we employ aberration-corrected TEM to extract images local atomic arrangements GBs, which reveal alternating pentagon−heptagon structure along high-angle GBs. Our findings...
The use of boron nitride (BN) as a substrate for graphene nanodevices has attracted much interest since the recent report that BN greatly improves mobility charge carriers in compared to standard SiO2 substrates. We have explored local microscopic properties on using scanning tunneling microscopy. find substrates result extraordinarily flat layers display Moiré patterns arising from relative orientation and lattices. Gate-dependent dI/dV spectra exhibit spectroscopic features are sharper...
We present a systematic Raman study of unconventionally-stacked double-layer graphene, and find that the spectrum strongly depends on relative rotation angle between layers. Rotation-dependent trends in position, width intensity graphene 2D G peaks are experimentally established accounted for theoretically. Our theoretical analysis reveals changes electronic band structure due to interlayer interaction, such as rotational-angle dependent Van Hove singularities, responsible observed spectra...
The Fermi velocity, vF, is one of the key concepts in study a material, as it bears information on variety fundamental properties. Upon increasing demand device applications, graphene viewed prototypical system for engineering vF. Indeed, several efforts have succeeded modifying vF by varying charge carrier concentration, n. Here we present powerful but simple new way to engineer while holding n constant. We find that when environment embedding modified, (i) inversely proportional its...
Chemical vapor deposited (CVD) graphene is often presented as a scalable solution to device fabrication, but date such has exhibited lower mobility than that produced by exfoliation. Using boron nitride underlayer, we achieve mobilities high 37 000 cm2/V s, an order of magnitude higher commonly reported for CVD and better most exfoliated graphene. This result demonstrates the barrier scalable, not growth technique rather choice substrate minimizes carrier scattering.
A facile method is reported for the direct (polymer-free) transfer of layer-area graphene from metal growth substrates to selected target substrates. The route, by avoiding several wet chemical steps and accompanying mechanical stresses contamination common all presently methods, enables fabrication devices with unprecedented quality. To demonstrate, we directly Cu holey amorphous carbon transmission electron microscopy (TEM) grids, resulting in robust, clean, full-coverage grids ideal high...
The folding of paper, hide, and woven fabric has been used for millennia to achieve enhanced articulation, curvature, visual appeal intrinsically flat, two-dimensional materials. For graphene, an ideal material, may transform it complex shapes with new distinct properties. Here, we present experimental results that folded structures in termed grafold, exist, their formations can be controlled by introducing anisotropic surface curvature during graphene synthesis or transfer processes. Using...
Surface plasmon, with its unique capability to concentrate light into sub-wavelength volume, has enabled great advances in photon science, ranging from nano-antenna and single-molecule Raman scattering plasmonic waveguide metamaterials. In many applications it is desirable control the surface plasmon resonance situ electric field. Graphene, tunable optical properties, provides an ideal material integrate nanometallic structures for realizing such control. Here we demonstrate effective...
Creating Unstable Atomic Orbitals A hallmark of atomic Bohr orbitals is that they are stable; is, time independent. However, for a very highly charged nucleus, the electrons must be described with relativistic Dirac equation; motion becomes dependent, spiraling into nucleus and coupling to positrons at large distances from nucleus. In graphene, charge carriers mass-less by equation, could also exhibit “atomic collapse” states. Wang et al. (p. 734 , published online 7 March) created clusters...
The understanding of crack formation due to applied stress is key predicting the ultimate mechanical behavior many solids. Here we present experimental and theoretical studies on cracks or tears in suspended monolayer graphene membranes. Using transmission electron microscopy, investigate crystallographic orientations tears. Edges from mechanically induced ripping exhibit straight lines are predominantly aligned armchair zigzag directions lattice. Electron-beam propagation also observed....
The basal plane of graphene has been known to be less reactive than the edges, but some studies observed vacancies in after reaction with oxygen gas. Observation these typically limited nanometer-scale resolution using microscopic techniques. This work demonstrates introduction and observation subnanometer by heat treatment a flow gas at low temperature such as 533 K or lower. High-resolution transmission electron microscopy was used directly observe vacancy structures, which were compared...
We demonstrate a process for batch production of large-area (100-3000 microm(2)) patterned free-standing graphene membranes on Cu scaffolds using chemical vapor deposition (CVD)-grown graphene. This technique avoids the use silicon and transfers As one application this technique, we fabricate transmission electron microscopy (TEM) sample supports. TEM characterization reveals relatively clean, highly TEM-transparent, single-layer regions ( approximately 50% by area) and, despite...
Hybrid converters could optimally exploit the solar spectrum to realize higher conversion efficiencies and low electricity costs, while ensuring availability of inexpensive dispatchable power.
Abstract We report in situ Joule heating on suspended single‐layer graphene a transmission electron microscope (TEM). Thermally‐driven degradation of pre‐deposited nanoparticles the membrane is monitored and used for local temperature estimation. By extrapolating power relation, we find that has exceptional thermal stability up to at least 2600 K. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effect of charge-carrier screening on the transport properties a neutral graphene sheet is studied by directly probing its electronic structure. We find that Fermi velocity, Dirac point and overall distortion cone are renormalized due to electron-electron interaction in an unusual way. also observe increase electron mean free path charged impurities. These observations help us understand basis for graphene, as well fundamental physics these interesting interactions at crossing.
We report a new and highly versatile approach to artificial layered materials synthesis which borrows concepts of molecular beam epitaxy, self-assembly, graphite intercalation compounds. It readily yields stacks graphene (or other two-dimensional sheets) separated by virtually any kind "guest" species. The material can be "sandwich like", for the guest species are relatively closely spaced form near-continuous inner layer sandwich, or "veil where widely separated, with each individually...
Photovoltaics (PV) are a promising source of clean renewable energy, but current technologies face cost-to-efficiency trade-off that has slowed widespread implementation. We have developed PV architecture-screening-engineered field-effect photovoltaics (SFPV)-that in principle enables fabrication low-cost, high efficiency from virtually any semiconductor, including the hard-to-dope metal oxides, sulfides, and phosphides. Prototype SFPV devices been constructed found to operate successfully...
Insects and hummingbirds remain unmatched in their aerodynamic ability to hover place addition other acrobatic feats such as flying backward sideways by exploiting flapping-wing motion [1]. Although this remarkable is key making small-scale aircraft, flapping-hovering behavior has been difficult reproduce artificially because of the challenging stability, power, aeroelastic phenomena involved. Recent interest unmanned air vehicles, especially those capable hovering like insects hummingbirds,...
We demonstrate cuprous oxide (Cu2O) based metal insulator semiconductor Schottky (MIS-Schottky) solar cells with efficiency exceeding 3%. A unique direct growth technique is employed in the fabrication, and hexagonal boron nitride (h-BN) serves simultaneously as a passivation insulation layer on active Cu2O layer. The devices are most efficient of any MIS-Schottky reported to date.
Snapshots of growth: The use a single graphene layer as the support for S-layer self-assembly proteins provides an ideal, robust flat surface to image expanding boundary by flash freezing and cryo-TEM, capturing conformational states present at (see figure). Image alignment averaging provide view steps leading subunit recruitment maturation in process. As service our authors readers, this journal supporting information supplied authors. Such materials are peer reviewed may be re-organized...
Despite unique and fascinating capability in subwavelength optics, active control of optical plasmon resonance has been hampered by drastically weak response free carriers at frequency. We demonstrate efficient gold nanorod with graphene electrical gating.