Such modification has a significant impact on the zgnr electronic structure. Under a transverse electric field, zigzagedge graphene nanoribbon transforms to an antiferomagnetic halfmetal 21 5,6,8,9, their zigzagedge nanoribbons are metals with halfmetallic ground. Sep 16, 2014 the successful fabrication of single layered graphene has generated a great deal of interest and research into graphene in recent years. Materials design of halfmetallic graphene and graphene nanoribbons. Mar 24, 2016 graphene, the material with a number of miraculous properties, is considered a possible replacement. The epoxy is filled with the gnr stacks, which serve as a conductive additive. Materials design of half metallic graphene and graphene nanoribbons. Louie1,2 1department of physics, university of california at berkeley, berkeley, california 94720, usa 2materials sciences division, lawrence berkeley national laboratory, berkeley, california 94720, usa dated. Ultranarrow metallic armchair graphene nanoribbons. Here we demonstrate a scalable method based on chemical vapor deposition for the direct growth of wellregistered graphene nanoribbons on sio2 substrates with precise control over their width, length, and. The altmetric attention score is a quantitative measure of the attention that a research article has received online. The charge density localized at the edge carbon atoms is given as ec e. Ballistic tracks in graphene nanoribbons dtu orbit. We use electrocharging assisted process which creates graphene nanoribbons and nanosheets in a metal by the application of a high dc current of 150 a to a mixture of the liquid metal and particles of carbon.
Graphene being a zero band gap material hinders the use of its intrinsic form for many applications requiring a moderate band gap, such as field effect transistors and optoelectronic devices. Ultranarrow metallic armchair graphene nanoribbons request pdf. E and u are the energy levels of the band edges corresponding to the edge carbon atoms in the absence and in the presence of electric fields, respectively, with e 1 nov 16, 2006 firstprinciples calculations predict that half metallic behaviour can be found in nanometrescale ribbons of graphene, in practically realistic conditions. The topdown approach consists of modifying a large graphene sheet i. Unveiling the magnetic structure of graphene nanoribbons rebeca ribeiro,1 jeanmarie poumirol,1 alessandro cresti,2 walter escof. To harness these characteristics of gnrs, it is essential to produce them with atomic precision. One of the most recent advancements is the development of graphene nanoribbons gnrs layers of graphene with ultrathin width of less than 50 nm. Graphene is the basic structural element of some carbon allotropes including graphite charcoal. Low temperature and temperaturedependent measurements reveal a length and orientation. From a structural point of view, chiral ribbons combine zigzag and armchair. Under a transverse electric field, zigzagedge graphene nanoribbon transforms to an antiferomagnetic halfmetal 21 5,6,8,9, their zigzagedge nanoribbons are metals with half metallic ground. In their article, the research team demonstrated fabrication of the. The corresponding circuit schematic including the graphene and metallic.
Bottomup fabrication of atomically precise graphene nanoribbons. Electrical current can be completely spin polarized in a class of materials known as halfmetals, as a result of the coexistence of metallic nature for electrons with one spin orientation and insulating for electrons with the other. As reported by the journal nature in its latest issue, researchers from empa, the max planck institute in mainz and the technical university of dresden have for the first time succeeded in producing graphene nanoribbons with perfect zigzag edges from molecules. Halfmetallicity in edgemodified zigzag graphene nanoribbons. Lowpower heterogeneous graphene nanoribboncmos multistate volatile memory circuit 3 section 5 discusses the leakage analysis and mitigation in gntram, followed by physical implementation description in section 6. Graphene nanoribbons with small enough width to impose lateral con. A simple model for an electrostatic potential difference between edges can be introduced for the ab.
Graphene is the basic structural element of some carbon allotropes including graphite charcoal carbon nanotubes fullerence chemical structures. Graphene nanoribbons gnrs are quasionedimensional strips of graphene with widths on the nanometer scale. Totally organic synthesis and characterization of graphene. Periodically functionalized graphene can mimic electronic behavior of edgemodified zgnrs as the edgemodified zigzag carbon chains effectively divide a graphene. Built from the bottom up, nanoribbons pave the way to onoff states for graphene. The optical conductivity of abstacked bilayer graphene exhibits several interesting infrared features as revealed in recent measurements. Graphene nanoribbons gnr also called nanographite ribbons carbon based material onedimensional structures with hexagonal two dimensional carbon lattices a derivative of graphene graphene ribbons were introduced as a theoretical model by mitsutaka fujita 9. Graphene nanoribbons have been suggested as ideal wires for use in future nanoelectronics. Layerselective halfmetallicity in bilayer graphene. The geometries, formation energies, and electronic and magnetic properties of ndoping defects, including single atom substitution and pyridine and pyrrolelike substructures in zigzag graphene nanoribbons zgnrs, were investigated by means of spinunrestricted density functional theory computations. Due to the interlayer interaction, the electron states localized at the edge carbon atoms in the asublattice are expected to have higher energies than those in the bsublattice 6. Dec 15, 2015 researchers have succeeded in experimentally realizing metallic graphene nanoribbons gnrs that are only 5 carbon atoms wide. Liquidphase exfoliation chemical vapor deposition chemically derived graphene organic synthesis of graphene.
Jun, 20 graphene nanoribbons split from nanotubes in a process created at rice university are now being used to improve the performance of lithium ion batteries. Absorption spectra of monolayer graphene nanoribbons. Tunable phononinduced transparency in bilayer graphene. In their article published in nature communications ultranarrow metallic armchair graphene nanoribbons, the research team demonstrated fabrication of the gnrs and.
Graphene is a oneatomiclayer thick twodimensional material made of carbon atoms arranged in a honeycomb structure. Researchers at aalto university have succeeded in experimentally realizing metallic graphene nanoribbons gnrs that are only 5 carbon atoms wide. Further research can be conducted in characterizing graphene nanoribbons. Dec 16, 2015 researchers at aalto university have succeeded in experimentally realizing metallic graphene nanoribbons gnrs that are only 5 carbon atoms wide. However, 2d graphene has conical points located at the fermi energy e f with zero density of states.
Its fascinating electrical, optical, and mechanical properties ignited enormous interdisciplinary interest from the physics, chemistry, and materials science fields. Mechanically, graphene has been measured to be extremely strong, being approximately 200 times stronger than steel with a young modulus of 1 tpa 17. When the size of the wire is reduced to the atomic scale, graphene is expected to outperform copper in terms of conductance and resistance to electromigration, which is the typical breakdown mechanism in thin metallic wires. Nov 07, 2012 graphene being a zero band gap material hinders the use of its intrinsic form for many applications requiring a moderate band gap, such as field effect transistors and optoelectronic devices. In particular, graphene ribbons have been predicted to be metallic if their edges exhibit a zigzag morphology, whereas armchair edges can give rise to either semiconducting or metallic transport. Graphene nanoribbons with smooth edges behave as quantum wires xinran wang1,2, yijian ouyang3, liying jiao1, hailiang wang1,limingxie1,justinwu1, jing guo3 and hongjie dai1 graphene nanoribbons with perfect edges are predicted to exhibit interesting electronic and spintronic properties14, notably quantumcon. The graphitic structures form a 3d epitaxial structure with the lattice of the metal and bond with atoms in the metal making the. Although many chemical modification schemes for achieving half metallicity in zigzagedged graphene nanoribbons zgnrs have been proposed, practically, halfmetallic transport is hardly observable with them due to the resulting negligible energy difference of the antiferromagnetic af and ferromagnetic f configurations between the two edges. Electrical current can be completely spin polarized in a class of materials known as half metals, as a result of the coexistence of metallic nature for electrons with one spin orientation and insulating for electrons with the other. Graphene ribbons were introduced as a theoretical model by mitsutaka fujita and coauthors to examine the edge and nanoscale size effect in graphene. Work on nanoribbons over the past decade has revolved around using lasers to carefully sculpt ribbons 10 or 20 atoms wide from larger sheets of graphene. Layerselective halfmetallicity in bilayer graphene nanoribbons.
Graphene nanoribbons get metallic nanowerk news researchers at aalto university have succeeded in experimentally realizing metallic graphene nanoribbons gnrs that are only 5 carbon atoms wide. Such asymmetric electronic states for the different spins have been predicted for some ferromagnetic metals for example, the heusler. The carboncarbon bond length in graphene is about 0. Graphene nanoribbons gnrs, also called nano graphene ribbons or nanographite ribbons are strips of graphene with width less than 50 nm. Graphene is an important material with potential application in spintronics. Direct growth of graphene nanoribbons for largescale. In the future, we plan to characterize them by measuring photoluminescence, and by observing thermally induced alignment in the gnrs. Graphene nanoribbons exfoliated from graphite surface. Graphene nanoribbons could be the savior of moores law. The existence of curious materials called half metals is predicted.
On the other hand, graphene nanoribbons with armchair edges can display insulating or metallic behaviour depending on graphene nanoribbon gnr width 32, 33. Based on their size and geometry, they possess unique electromagnetic properties and tunable band gaps which are nanodevice relevant. Composites of graphene nanoribbon stacks and epoxy for joule. May 03, 2018 we use electrocharging assisted process which creates graphene nanoribbons and nanosheets in a metal by the application of a high dc current of 150 a to a mixture of the liquid metal and particles of carbon. Synthesis of graphene two distinct strategies have been established to synthesize graphene. The gnr stacks are on average 30 nm thick, 250 nm wide, and 30. Depending on the width of the ribbon and type of adsorbed transition metals, armchair nanoribbon can either become a metal or a semiconductor. Dry transfer and characterization of graphene nanoribbons. Media in category graphene nanoribbons the following 6 files are in this category, out of 6 total.
Networks of graphene nanoribbons and nanosheets formed in. Solid state physics laboratory, eth zurich, 8093 zurich, switzerland email. Physical modeling of graphene nanoribbon field effect. The modifications are realized by saturating the dangling edge bonds by different terminal groups, such as h, nh2, no2, and ch3. Such asymmetric electronic states for the different spins have been predicted for some ferromagnetic metals for example, the heusler compounds and were first. One of the most recent advancements is the development of graphene nanoribbons gnrs layers of graphene with ultrathin width of.
Half metallic graphene nanoribbons youngwoo son, 1,2marvin l. Doping of graphene and graphene nanoribbons is relevant because, depending on the location of the dopants and their concentration, their physicochemical properties could be tuned and controlled. Recently a chemical route has been developed to produce graphene nanoribbons with width. Realizing robust halfmetallic transport with chemically. Fabrication methods and related electronic properties graphene nanoribbons can be synthesized by topdown or bottomup approaches. The successful fabrication of single layered graphene has generated a great deal of interest and research into graphene in recent years. Composites of graphene nanoribbon stacks and epoxy for. Learn more about these metrics article views are the countercompliant sum of full text article downloads since november 2008 both pdf and html across all institutions and individuals. Low temperature and temperaturedependent measurements reveal a length. Materials design of halfmetallic graphene and graphene. Unveiling the magnetic structure of graphene nanoribbons. Direct growth of graphene nanoribbons for largescale device.
Of great concern is the design of graphene nanoribbons gnrs, which allow some gap engineering 4. Under a transverse electric field, zigzagedge graphene nanoribbon transforms to an antiferomagnetic half metal 21 5,6,8,9, their zigzagedge nanoribbons are metals with half metallic ground. Dec 15, 2015 graphene nanoribbons have been suggested as ideal wires for use in future nanoelectronics. Lithographical patterning of large graphene layers allows one to create graphene ribbons 4 with rough edges. Through patterned chemical modification, we show that both graphene sheets and zigzagedged graphene nanoribbons zgnrs can be converted to halfmetals as long as the unmodified carbon strip or width of zgnrs is sufficiently wide.
The edge carbon atoms are more easily substituted with n atoms, and threenitrogen vacancy. The one atom thin carbon film is ultralight, extremely flexible and highly conductive. The energy level shifts of the band edges of the energy bands, occupied by the edge. Through patterned chemical modification, we show that both graphene sheets and zigzagedged graphene nanoribbons zgnrs can be converted to half metals as long as the unmodified carbon strip or width of zgnrs is sufficiently wide. Apr 18, 2016 graphene nanoribbons gnr also called nanographite ribbons carbon based material onedimensional structures with hexagonal two dimensional carbon lattices a derivative of graphene graphene ribbons were introduced as a theoretical model by mitsutaka fujita 9 10. Electronic transport in graphene nanoribbons melinda young han this dissertation examines the electronic properties of lithographically fabricated graphene \nanoribbons gnrs with widths in the tens of nanometers. Researchers have succeeded in experimentally realizing metallic graphene nanoribbons gnrs that are only 5 carbon atoms wide. Here we demonstrate a scalable method based on chemical vapor deposition for the direct growth of wellregistered graphene nanoribbons on sio2 substrates with precise control over their width, length. Energy and transport gaps in etched graphene nanoribbons f molitor, c stampfer, j guttinger, a jacobsen, t ihn and k ensslin. Technology exploration for graphene nanoribbon fets. A widebandgap metalsemiconductormetal nanostructure. Graphene, the material with a number of miraculous properties, is considered a possible replacement. Spintronic transport in armchair graphene nanoribbon with.
Aug 10, 2018 quantum chains in graphene nanoribbons. Abstract graphene nanoribbons gnrs make up an extremely interesting class of. Graphene nanoribbons split from nanotubes in a process created at rice university are now being used to improve the performance of lithium ion batteries. Graphene nanoribbons gnrs, also called nanographene ribbons or nanographite ribbons are strips of graphene with width less than 50 nm.
Edgemodified zigzag graphene nanoribbons zgnr are investigated with density functional theory. Firstprinciples calculations predict that halfmetallic behaviour can be found in nanometrescale ribbons of graphene, in practically realistic conditions. Electrical current can be completely spin polarized in a class of materials known as halfmetals, as a result of the coexistence of. It is well known that the energy gap can be engineered by cutting a 2d graphene sheet into a onedimensional 1d graphene nanoribbon gnr, where the edge carbon atoms. High quality graphene nanoribbons epitaxially grown on the sidewalls of silicon carbide sic mesa structures. Coreprotective halfmetallicity in trilayer graphene. Nano letters bulk production of a new form of sp2 carbon. Electronic transport in graphene nanoribbons melinda young han this dissertation examines the electronic properties of lithographically fabricated graphene anoribbons gnrs with widths in the tens of nanometers. The earliest theoretical studies of graphene nanoribbons, using a simple tightbinding method, predicted that of the armchair nanoribbons, whose width index satisfies is an integer, are metallic, and another are semiconductor with band gaps depending on their width, while all zigzag nanoribbons are metallic, a similar behavior as carbon nanotubes cnts. Electrical current can be completely spin polarized in a class of materials known as halfmetals, as a result of the. Periodically functionalized graphene can mimic electronic behavior of edgemodified zgnrs as the edgemodified zigzag carbon chains effectively divide a. A conductive composite of graphene nanoribbon gnr stacks and epoxy is fabricated. Intrinsic halfmetallicity in modified graphene nanoribbons.
1380 375 184 629 317 1095 901 1560 1239 600 865 454 195 1523 807 1523 819 1326 209 1293 72 250 1239 1418 395 300 1559 1371 198 463 204 1001 615 120 583 327