A5035833074- Graphene research and applications
- Carbon Nanotubes in Composites
- Quantum and electron transport phenomena
- Advanced Chemical Physics Studies
- Molecular Junctions and Nanostructures
- Diamond and Carbon-based Materials Research
- Topological Materials and Phenomena
- Graphene and Nanomaterials Applications
- Boron and Carbon Nanomaterials Research
- Force Microscopy Techniques and Applications
- Magnetism in coordination complexes
- Fullerene Chemistry and Applications
- nanoparticles nucleation surface interactions
- Thermal properties of materials
- Mechanical and Optical Resonators
- Advancements in Battery Materials
- Semiconductor materials and devices
- Silicon Carbide Semiconductor Technologies
- Physics of Superconductivity and Magnetism
- Inorganic Fluorides and Related Compounds
- Inorganic Chemistry and Materials
- Magnetic properties of thin films
- Atomic and Molecular Physics
- Nanotechnology research and applications
- Spectroscopy and Quantum Chemical Studies
Georgia Institute of Technology
2013-2024
Tianjin University
2017-2024
University of Jeddah
2014-2015
State Street (United States)
2012-2013
University of California, Riverside
2009
Centre National de la Recherche Scientifique
2005-2006
Université de Montpellier
2005
University of Illinois Urbana-Champaign
2005
Brazilian Synchrotron Light Laboratory
1997-2005
École Polytechnique Fédérale de Lausanne
1991-2000
Many potential applications have been proposed for carbon nanotubes, including conductive and high-strength composites; energy storage conversion devices; sensors; field emission displays radiation sources; hydrogen media; nanometer-sized semiconductor devices, probes, interconnects. Some of these are now realized in products. Others demonstrated early to advanced one, storage, is clouded by controversy. Nanotube cost, polydispersity nanotube type, limitations processing assembly methods...
Ultrathin epitaxial graphite was grown on single-crystal silicon carbide by vacuum graphitization. The material can be patterned using standard nanolithography methods. transport properties, which are closely related to those of carbon nanotubes, dominated the single graphene layer at interface and reveal Dirac nature charge carriers. Patterned structures show quantum confinement electrons phase coherence lengths beyond 1 micrometer 4 kelvin, with mobilities exceeding 2.5 square meters per...
We have produced ultrathin epitaxial graphite films which show remarkable 2D electron gas (2DEG) behavior. The films, composed of typically three graphene sheets, were grown by thermal decomposition on the (0001) surface 6H−SiC, and characterized science techniques. low-temperature conductance spans a range localization regimes according to structural state (square resistance 1.5 kΩ 225 at 4 K, with positive magnetoconductance). Low-resistance samples characteristics weak in two dimensions,...
A high-intensity electron gun based on field emission from a film of aligned carbon nanotubes has been made. The consists nanotube with 1-millimeter-diameter grid about 20 micrometers above it. Field-emission current densities 0.1 milliampere per square centimeter were observed for applied voltages as low 200 volts, and greater than 100 milliamperes have realized at 700 volts. is air-stable, easy inexpensive to fabricate, functions stably reliably long times (short-term fluctuations are the...
The study of simple metal clusters has burgeoned in the last decade, motivated by growing interest evolution physical properties from atom to bulk solid, a progression passing through domain atomic clusters. On experimental side, rapid development new techniques for producing and probing detecting them resulted phenomenal increase our knowledge these systems. For simplest metals, alkali noble electronic structure is dominated number valence electrons, ionic cores are secondary importance....
Mass spectra are presented for sodium clusters of $N$ atoms per cluster ($N=4\ensuremath{-}100$) produced in a supersonic expansion with argon carrier gas. The show large peaks or steps at $N=8, 20, 40, 58, \mathrm{and} 92$. These can be understood terms one-electron shell model which independent delocalized atomic $3s$ electrons bound spherically symmetric potential well.
The conductance of multiwalled carbon nanotubes (MWNTs) was found to be quantized. experimental method involved measuring the by replacing tip a scanning probe microscope with nanotube fiber, which could lowered into liquid metal establish gentle electrical contact at fiber. arc-produced MWNTs is one unit quantum G0 = 2e2/h (12.9 kilohms)-1. conduct current ballistically and do not dissipate heat. nanotubes, are typically 15 nanometers wide 4 micrometers long, several orders magnitude...
Static and dynamic mechanical deflections were electrically induced in cantilevered, multiwalled carbon nanotubes a transmission electron microscope. The resonantly excited at the fundamental frequency higher harmonics as revealed by their deflected contours, which correspond closely to those determined for cantilevered elastic beams. bending modulus function of diameter was found decrease sharply (from about 1 0.1 terapascals) with increasing 8 40 nanometers), indicates crossover from...
Molecular beam deflection measurements of small iron, cobalt, and nickel clusters show how magnetism develops as the cluster size is increased from several tens to hundreds atoms for temperatures between 80 1000 K. Ferromagnetism occurs even smallest sizes: with fewer than about 30 magnetic moments are atomlike; up 700 atoms, approach bulk limit, oscillations probably caused by surface-induced spin-density waves. The trends explained in a shell model. A crystallographic phase transition high...
The electronic properties of epitaxial graphene grown on SiC have shown its potential as a viable candidate for post-CMOS electronics. However, progress in this field requires detailed understanding both the structure and growth graphene. To that end, review will focus current state research it relates to SiC. We pay particular attention similarity differences between two polar faces, (0001) , hexagonal Growth techniques, subsequent morphology graphene/SiC interface stacking order are...
The addition of nitrophenyl groups to the surface few-layer epitaxial graphene (EG) by formation covalent carbon-carbon bonds changed electronic structure and transport properties EG from near-metallic semiconducting.
We show experimentally that multilayer graphene grown on the carbon terminated SiC(0001[over ]) surface contains rotational stacking faults related to epitaxial condition at graphene-SiC interface. Via first-principles calculation, we demonstrate such produce an electronic structure indistinguishable from isolated single sheet in vicinity of Dirac point. This explains prior experimental results showed single-layer properties, even for films tens layers thick.
We report on the field emission properties of single-wall carbon nanotube films, with emphasis current–versus–voltage (I–V) characteristics and current stability. The films are excellent emitters, yielding densities higher than 10 mA cm−2 operating voltages that far lower for other film but show a significant degradation their performances time. observed deviations from Fowler-Nordheim behavior in I–V point to presence nonmetallic density states at tip nanotubes.
Multilayer epitaxial graphene is investigated using far infrared transmission experiments in the different limits of low magnetic fields and high temperatures. The cyclotron-resonance-like absorption observed at temperature below 50 mT, probing nearest vicinity Dirac point. carrier mobility found to exceed 250,000 cm2/(V x s). In limit temperatures, well-defined Landau level quantization up room 1 T, a phenomenon unusual solid state systems. A negligible increase width cyclotron resonance...
Far infrared transmission experiments are performed on ultrathin epitaxial graphite samples in a magnetic field. The observed cyclotron resonance-like and electron-positron-like transitions excellent agreement with the expectations of single-particle model Dirac fermions graphene, an effective velocity c=1.03 x 10(6) m/s.
Open carbon nanotubes were filled with molten silver nitrate by capillary forces. Only those tubes inner diameters of 4 nanometers or more filled, suggesting a capillarity size dependence as result the lowering nanotube-salt interface energy increasing curvature nanotube walls. Nanotube cavities should also be less chemically reactive than graphite and may serve nanosize test tubes. This property has been illustrated monitoring decomposition within in situ an electron microscope, which...
Application of a magnetic field to conductors causes the charge carriers circulate in cyclotron orbits with quantized energies called Landau levels (LLs). These are equally spaced normal metals and two-dimensional electron gases. In graphene, however, carrier velocity is independent their energy (like massless photons). Consequently, LL not include characteristic zero-energy state (the n = 0 LL). With use scanning tunneling spectroscopy graphene grown on silicon carbide, we directly observed...
We investigate the ultrafast relaxation dynamics of hot Dirac fermionic quasiparticles in multilayer epitaxial graphene using optical differential transmission spectroscopy. observe spectra which are well described by interband transitions with no electron-hole interaction. Following initial thermalization and emission high-energy phonons, electron cooling is determined electron-acoustic phonon scattering, found to occur on time scale 1 ps for highly doped layers, 4-11 undoped layers. The...
Angle-resolved photoemission and x-ray diffraction experiments show that multilayer epitaxial graphene grown on the SiC(0001) surface is a new form of carbon composed effectively isolated sheets. The unique rotational stacking these films causes adjacent layers to electronically decouple leading set nearly independent linearly dispersing bands (Dirac cones) at K point. Each cone corresponds an individual macroscale sheet in stack where AB-stacked sheets can be considered as low density faults.
After the pioneering investigations into graphene-based electronics at Georgia Tech (GT), great strides have been made developing epitaxial graphene on silicon carbide (EG) as a new electronic material. EG has not only demonstrated its potential for large scale applications, it also become an invaluable material fundamental two-dimensional electron gas physics showing that is route to define future science. It was long known mono and multilayers grow SiC crystals high temperatures in...
Magnetic moments \ensuremath{\mu}(N) of iron clusters in a molecular beam, with temperatures ranging from 100 to 1000 K are investigated their Stern-Gerlach deflections. We find that at temperature 120 K, \ensuremath{\mu} (25\ensuremath{\le}N\ensuremath{\le}130) is 3${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$ per atom, decreasing about the bulk value (2.2${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$ atom) near N=500. For all sizes, decreases increasing temperature, and approximately constant...