Facts about Graphene
Molecule detection is indirect: as a gas molecule adsorbs to the surface of graphene, the location of adsorption experiences a local change in electrical resistance.
Utilizing an atomic force microscope, research has recently been able to measure the spring constant of suspended Graphene sheets.
The previous efforts did not result in graphene as we know it now, i.e.
Graphene is presently one of the most expensive materials on Earth, with a sample that can be placed at the cross section of a human hair costing more than $1,000 (as of April 2008).
In 2008, researchers of AMICA and the University of Manchester demonstrated a new switching effect in graphene field-effect devices.
Experimental results from transport measurements show that graphene has a remarkably high electron mobility at room temperature, with reported values in excess of 15,000 cm2V?1s?1.
Graphene's unique electronic properties produce an unexpectedly high opacity for an atomic monolayer, with a startlingly simple value: it absorbs ?? ? 2.3 percent of white light, where ? is the fine-structure constant.
Nanostripes of graphene (in the zigzag orientation), at low temperatures, show spin-polarized edge currents , which also suggests applications in the recent field of spintronics.
Graphene has a high carrier mobility as well as low noise, allowing it to be utilized as the channel in a field-effect transistor (FET).
Graphene is quite different from most conventional three-dimensional materials.
Atomic resolution real-space images of isolated, single-layer graphene on silicon dioxide substrates were obtained by scanning tunneling microscopy.
Based on its properties, researchers have proposed a number of potential applications for graphene.
doped graphene with various gaseous species (some acceptors, some donors), and found the initial undoped state of a graphene structure can be recovered by gently heating the graphene in vacuum.
Current graphene transistors show a very poor on-off ratio, and researchers are trying to find ways for improvement.
Study of the temperature dependence of the Shubnikov-de Haas oscillations in graphene reveals that the carriers have a non-zero cyclotron mass, despite their zero effective mass from the E-k relation.
Interestingly, the first plateau at is absent, indicating that bilayer graphene stays metallic at the neutrality point.
Researchers have observed ripples in suspended layers of graphene, and it has been proposed that the ripples are caused by thermal fluctuations in the material.
Scattering by the acoustic phonons of graphene limits the room temperature mobility to 200,000 cm2V?1s?1 at a carrier density of 1012 cm?2.
The resulting material (circular graphene layers of 5.3 angstrom thickness) is soluble in tetrahydrofuran, tetrachloromethane, and dichloroethane.
The term was also used in early descriptions of carbon nanotubes, as well as for epitaxial graphene, and polycyclic aromatic hydrocarbons.
Such residue may be the "adsorbates" observed in TEM images, and may explain the rippling of suspended graphene.
Planar graphene itself has been presumed not to exist in the free state, being unstable with respect to the formation of curved structures such as soot, fullerenes, and nanotubes.
Despite the zero carrier density near the Dirac points, graphene exhibits a minimum conductivity on the order of .
IBM announced in December 2008 that it has fabricated and characterized graphene transistors operating at GHz frequencies.
Graphene would also be an excellent component of integrated circuits, and graphene nanoribbons could be a way to construct ballistic transistors.
Bilayer graphene also shows the quantum Hall effect, but with the standard sequence where .
Potential for this high conductivity can be seen by considering graphite, a 3D version of graphene that has basal plane thermal conductivity of over a 1000 W/mK (comparable to diamond).
The near-room temperature thermal conductivity of graphene was recently measured to be between (4.84±0.44) Ч103 to (5.30±0.48) Ч103 Wm?1K?1.
Despite its 2-D nature, graphene has 3 acoustic phonon modes.
Graphene sheets, held together by van der Waals forces, were suspended over silicon dioxide cavities where an AFM tip was probed to test its mechanical properties.
Recent experiments have probed the influence of chemical dopants on the carrier mobility in graphene.
A perfect graphene would consist exclusively of hexagonal cells; the presence of pentagonal and heptagonal cells would constitute defects.
Another method uses the atomic structure of a substrate to seed the growth of the graphene, known as epitaxial growth.
The term graphene should be used only when the reactions, structural relations or other properties of individual layers are discussed."
The mobility reduction is reversible on heating the graphene to remove the potassium.
Larger graphene molecules or sheets (so that they can be considered as true isolated 2D crystals) cannot be grown even in principle.
Due to the incredibly high surface area to mass ratio of graphene, one potential application is in the conductive plates of ultracapacitors.
Graphene processed using lithographic techniques is covered by photoresist residue, which must be cleaned to obtain atomic-resolution images.
In 2006, Georgia Tech researchers announced that they had successfully built an all-graphene planar FET with side gates.
Graphene nanoribbons (GNRs) are essentially single layers of graphene that are cut in a particular pattern to give it certain electrical properties.
Due to its high electronic quality, graphene has attracted the interest of technologists who see graphene nanoribbons as a way of constructing ballistic transistors.
The onset of graphene properties, as compared to those of a PAH are not known.
Another method is to heat silicon carbide to high temperatures (1100°C) to reduce it to graphene.
By oxidizing and chemically processing graphene, and then floating them in water, the graphene flakes form a single sheet and bond very powerfully.
Graphene is the strongest substance known to man, according to a study released in August 2008 by Columbia University.
Researchers have developed a method of placing graphene oxide paper in a solution of pure hydrazine (a chemical compound of nitrogen and hydrogen), which reduces the graphite oxide paper into single-layer graphene.
High-quality sheets of graphene exceeding 1 cmІ (0.2 sq in) in area have been synthesized via chemical vapor deposition on thin nickel layers.
Rippling of graphene on the silicon dioxide surface was determined by conformation of graphene to the underlying silicon dioxide, and not an intrinsic effect.
Graphene displays an anomalous quantum Hall effect with the sequence shifted by with respect to the standard sequence.
Graphene is the name given to a single layer of carbon atoms densely packed into a benzene-ring structure, and is widely used to describe properties of many carbon-based materials, including graphite, large fullerenes, nanotubes, etc.
Graphene nanopore rims could be further optimally functionalized for more selective passage of DNA bases, which could also distinguish the DNA bases in time.
Graphene is the basic structural element of several carbon allotropes, including graphite, carbon nanotubes, and other fullerenes.
Electrical spin-current injection and detection in graphene was recently demonstrated up to room temperature.
Later, graphene crystals obtained by using the Manchester recipe were also made suspended and their thickness proved directly by electron microscopy.
The atomic structure of isolated, single-layer graphene was studied by transmission electron microscopy (TEM) on sheets of graphene suspended between bars of a metallic grid.
A recent publication has described a process for producing gram-quantities of graphene, by the reduction of ethanol by sodium metal, followed by pyrolysis of the ethoxide product, and washing with water to remove sodium salts.
The very high surface area to mass ratio of graphene suggests it could be used in the conductive plates of ultracapacitors.
Graphene's high electrical conductivity and high optical transparency make it a candidate for transparent conducting electrodes, useful for such applications as touchscreens, liquid crystal displays, organic photovoltaic cells, and Organic light-emitting diodes (OLEDs).
A series of steps involving oxidation and exfoliation result in small graphene plates with carboxyl groups at their edges.
Graphene is a one-atom-thick planar sheet of carbon atoms that are densely packed in a honeycomb crystal lattice.
In 2008, the smallest transistor so far—one atom thick and 10 atoms wide—was made of graphene.
Electron diffraction patterns showed the expected hexagonal lattice of graphene.
Soluble fragments of graphene can be prepared in the laboratory through chemical modification of graphite.
Graphene exhibits a pronounced response to a perpendicular external electric field, allowing one to build FETs (field-effect transistors).
Transmission electron microscope studies show faceting at defects in flat graphene sheets, and suggest a possible role in this unlayered-graphene for two-dimensional dendritic crystallization from a melt.
Researchers are looking into methods of transferring single graphene sheets from their source of origin (mechanical exfoliation on SiO2 / Si or thermal graphitization of a SiC surface) onto a target substrate of interest.
Suspended graphene also showed "rippling" of the flat sheet, with amplitude of about one nanometer.
Graphene has the ideal properties to be an excellent component of integrated circuits.
Single-walled carbon nanotubes may be considered to be graphene cylinders; some have a hemispherical graphene cap (that includes 6 pentagons) at each end.
Graphene nanoribbons may prove generally capable of replacing silicon as a semiconductor in modern technology.
Within this definition of graphene, it was first isolated by the Manchester group of Andre Geim who in 2004 finally managed to extract single-atom-thick crystallites from bulk graphite.
Graphene is thought to be an ideal material for spintronics due to small spin-orbit interaction and near absence of nuclear magnetic moments in carbon.
Previously, it was assumed that graphene cannot exist in the flat state and should scroll into nanotubes "to decrease the surface energy".