Basically nanoribbons can be classified into two categories, according to the geometry of their edge, armchair, and zigzag, which determine their electronic structure. Such modification has a significant impact on the zgnr electronic structure. One of the most recent advancements is the development of graphene nanoribbons gnrs layers of graphene with ultrathin width of. For the first time, researchers have experimentally observed light emission from individual graphene nanoribbons. The modifications are realized by saturating the dangling edge bonds by different terminal groups, such as h, nh2, no2, and ch3. Graphene nanoribbons gnrs, defined as nanometerwide strips of graphene, have attracted increasing attention as promising candidates for nextgeneration semiconductors. Recently a chemical route has been developed to produce graphene nanoribbons with width. Graphene, the material with a number of miraculous properties, is considered a possible replacement. Although all halfmetals are ferromagnetic or ferrimagnetic, most ferromagnets are not halfmetals. Such asymmetric electronic states for the different spins have been predicted for some ferromagnetic metals for example, the heusler. Electrical current can be completely spin polarized in a class of materials known as halfmetals, as a result of the coexistence of. Firstprinciples calculations predict that halfmetallic behaviour can be found in nanometrescale ribbons of graphene, in practically realistic conditions. With its rst experimental discovery in 2004, graphene takes its place as the two.
We have demonstrated this in graphene nanomeshes gnms with honeycomblike arrays of lowdefect hexagonal nanopores by observing roomtemperature ferromagnetism and spinbased phenomena arising from the zigzagpore edges. The effect of boron and nitrogen substitutional doping at four successive positions on electronic and transport properties of zigzag graphene nanoribbons zgnrs is studied using spinunpolarized density functional theory. The one atom thin carbon film is ultralight, extremely flexible and highly conductive. Low temperature and temperaturedependent measurements reveal a length and orientation. 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. Electronic properties of nanopore edges of ferromagnetic.
Compared to a twodimensional graphene whose band gap remains close to zero even if a large strain is applied, the band gap of a graphene nanoribbon gnr is sensitive to both. The band structures of strained graphene nanoribbons gnrs are examined using a tightbinding hamiltonian that is directly related to the type and magnitude of strain. Halfmetallicity in edgemodified zigzag graphene nanoribbons. Key laboratory for intelligent nano materials and devices of moe and state key. Controlling halfmetallicity of graphene nanoribbons by. On the other hand, when d c d c1, only one of the layers becomes halfmetallic leaving the other insulating, which would happen in wide. Realizing robust half metallic transport with chemically modi. 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. Unveiling the magnetic structure of graphene nanoribbons rebeca ribeiro,1 jeanmarie poumirol,1 alessandro cresti,2 walter escof. Ferromagnetism in zigzag gan nanoribbons with tunable half. 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 received 29 june 2006. Layerselective halfmetallicity in bilayer graphene. A systematic study of various edge modified graphene nanoribbons gnrs have been performed using a density functional theory method. Materials design of halfmetallic graphene and graphene nanoribbons.
Band gap of strained graphene nanoribbons pdf paperity. The carboncarbon bond length in graphene is about 0. However, pristine graphene is gapless which hinders its direct application towards graphenebased semiconducting devices. Download citation halfmetallic graphene nanoribbons electrical current can be completely spin polarized in a class of materials known as halfmetals, as a result of the coexistence of. Graphene nanoribbons have been largely studied theoretically, experimentally and.
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. The halfmetallicity of zigzag graphene nanoribbons with. Six chemical functional groups, namely, oh, nh2, nch32, so2, no2, and cn, are considered for the edge modification. The nanoribbons in a solution with tin oxide have more than double the capacity for lithium than standard graphene anodes in current commercial batteries. Electrical current can be completely spin polarized in a class of materials known as halfmetals, as a result of the.
Electronic and transport properties of boron and nitrogen. Graphene nanoribbons exfoliated from graphite surface. 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. The resulting gnrs are several micrometers in length, with 75% being singlelayer, and 40% being narrower than 20 nm in width. Scalable templated growth of graphene nanoribbons on sic. Halfmetallic graphene nanoribbons internet archive. Exploration of half metallicity in edgemodified graphene. Realizing robust halfmetallic transport with chemically. Graphene nanoribbons split from nanotubes in a process created at rice university are now being used to improve the performance of lithium ion batteries. D c1 and d c2 correspond to the band gap closure in a layer and between layers, respectively, the smaller of the two being the critical electric field d c for a band gap closure in the bizgnrs when d c d c2, halfmetallicity occurs between the two layers. Graphene is a oneatomiclayer thick twodimensional material made of carbon atoms arranged in a honeycomb structure. Edgemodified zigzag graphene nanoribbons zgnr are investigated with density functional theory.
First, a short introduction of graphene crystal structure and phonon dispersion is given. Halfmetallicity in hybrid grapheneboron nitride nanoribbons with dihydrogenated edges. A metalfree ferromagnet with charge and spin current rectification. The successful fabrication of single layered graphene has generated a great deal of interest and research into graphene in recent years. Lithographical patterning of large graphene layers allows one to create graphene ribbons 4 with rough edges. Many of the known examples of halfmetals are oxides, sulfides, or heusler alloys in halfmetals, the valence band for one.
Read tunable halfmetallic properties and spin seebeck effects in zigzagedged graphene nanoribbons adsorbed with v atom or vbenzene compound, organic electronics on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at. Materials design of halfmetallic graphene and graphene nanoribbons article pdf available in applied physics letters 9422. Moreover, two kinds of studied zgnrs present massless diracfermion band structure when they behave like halfmetals. Certain doping concentrations caused halfmetallic graphene. Efficient synthesis of graphene nanoribbons sonochemically. 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. For the other half of electrons, with the opposite spin, a halfmetal is insulating. A new paradigm to halfmetallicity in graphene nanoribbons arxiv. Graphene nanoribbons with small enough width to impose lateral con. Toward coveedged low band gap graphene nanoribbons. Chemical functionalization of graphene nanoribbons. This results in a single type of spin state at the fermi. Raman in bulk graphene is discussed for numbers of layers with different.
Materials design of halfmetallic graphene and graphene. 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. Particular attention is placed on the possibility of achieving halfmetallicity in the graphene nanostructures. Graphene nanoribbons reach out to the molecular world. We report a facile approach to synthesize narrow and long graphene nanoribbons gnrs by sonochemically cutting chemically derived graphene sheets gss. Periodically functionalized graphene can mimic electronic behavior of edgemodified zgnrs as the edgemodified zigzag carbon chains effectively divide a. Intrinsic halfmetallicity in modified graphene nanoribbons. Graphene is an important material with potential application in spintronics. Graphene nanoribbons gnrs are expected to display extraordinary properties in the form of nanostructures. First flashes of light observed from individual graphene. 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.
These characteristics of gnrs are in stark contrast to those of graphene, which is a carbon sheet with semimetal, zero band gap characteristics. Pascual adds that the spanish collaborators have demonstrated that small variations in the way the graphene nanoribbons are attached to a molecule can alter its magnetic properties. Theoretical exploration of the half metallicity of graphene nanoribbons boron nitride bilayer system. A halfmetal is any substance that acts as a conductor to electrons of one spin orientation, but as an insulator or semiconductor to those of the opposite orientation.
Magnetic boron nitride nanoribbons with tunable electronic. Firstprinciples calculations predict that half metallic behaviour can be found in nanometrescale ribbons of graphene, in practically realistic conditions. The halfmetallic nature of the ribbons under an external inplane. Graphene ribbons were introduced as a theoretical model by mitsutaka fujita and coauthors to examine the edge and nanoscale size effect in graphene. Its fascinating electrical, optical, and mechanical properties ignited enormous interdisciplinary interest from the physics, chemistry, and materials science fields. Firstorder and the double resonance raman scattering mechanism in graphene are discussed to understand the most prominent raman peaks. The calculated band gaps are listed in the first part. Researchers have succeeded in experimentally realizing metallic graphene nanoribbons gnrs that are only 5 carbon atoms wide. Yuling liu, xiaojun wu, yu zhao, xiao cheng zeng, and jinlong yang. 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.
Considering that, the spin polarization becomes particularly important in this situation. Unveiling the magnetic structure of graphene nanoribbons. Graphene nanoribbons are strips of graphene, the honeycomb lattice of carbon with sp 2 hybridization. Energy gaps in graphene nanoribbons youngwoo son,1,2 marvin l. Consequently, the ground state of such zgnrs is very close to halfmetallic state, and thus a smaller critical electric field is required for the systems to achieve the halfmetallic state. Graphene nanoribbons have been suggested as ideal wires for use in future nanoelectronics. Graphene is the basic structural element of some carbon allotropes including graphite charcoal. 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. Metalmetal transition in zigzag 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. Graphene nanoribbons gnrs, also called nanographene ribbons or nanographite ribbons are strips of graphene with width less than 50 nm. Graphene is a single layer of carbon atoms bound in a honeycomb arrangement.
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