Ferromagnetism and half metallicity in atomically thin holey nitrogenated graphene based systems. We show that this phenomenon is realizable if inplane homogeneous electric fields are applied across the zigzagshaped edges of the graphene nanoribbons, and that their magnetic properties can be controlled by the external electric fields. Halfmetallicity in edgemodified zigzag graphene nanoribbons. Scalable templated growth of graphene nanoribbons on sic. Ballistic tracks in graphene nanoribbons dtu orbit. Realizing robust halfmetallic transport with chemically. Aug 31, 2018 unsaturated nanoribbons are magnetic metals so that the armchair c 3 n nanoribbons are gapless spin semiconductors in the antiferromagnetic state and half metals in the ferromagnetic state. The spinpolarized electronic structure and halfmetallicity of zigzag graphene nanoribbons zgnrs with asymmetric edge terminations are investigated by using first principles calculations. We investigate theoretically the infrared optical response characteristics of metallic armchairzigzagedge graphene nanoribbons azgnrs to an external longitudinally polarized electromagnetic field at low temperatures. Proximityinduced spin polarization of graphene in contact. The halfmetallic property originates from the agnr energy gap of the up spin located at the fermi energy, while large electronic states are generated for the down spin. Tunable halfmetallic properties and spin seebeck effects in. The modifications are realized by saturating the dangling edge bonds by different terminal groups, such as h, nh2, no2, and ch3. Electronic properties of lidoped zigzag graphene nanoribbons p.
Low temperature and temperaturedependent measurements reveal a length. 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. A new paradigm to halfmetallicity in graphene nanoribbons arxiv. The spinpolarized electronic structure and half metallicity of zigzag graphene nanoribbons zgnrs with asymmetric edge terminations are investigated by using first principles calculations. Spintronic transport in armchair graphene nanoribbon with. Researchers have succeeded in experimentally realizing metallic graphene nanoribbons gnrs that are only 5 carbon atoms wide. Dec 16, 2015 graphene nanoribbons have been suggested as ideal wires for use in future nanoelectronics. Graphene nanoribbons exfoliated from graphite surface. They demonstrated that 7atomwide nanoribbons emit light at a high intensity that.
Although the halfmetallic property is not robust when the hydrogenation ratio is large, this behavior is sustained for partially hydrogenated zigzag bnnrs with a smaller degree of hydrogenation. Controlling halfmetallicity of graphene nanoribbons by using. Graphene is an important material with potential application in spintronics. Thermal spin filtering effect and giant magnetoresistance. Firstprinciples study of linedefectembedded zigzag. In their article, the research team demonstrated fabrication of the.
Many of the known examples of halfmetals are oxides, sulfides, or heusler alloys in halfmetals, the valence band for one. In their article published in nature communications ultranarrow metallic armchair graphene nanoribbons, the research team demonstrated fabrication of the gnrs and. Polyaniline nanoribbons decomposed from the twodimensional polyaniline sheet c 3 n sheet are investigated using a density functional theory. Based on firstprinciples calculations, we present the electronic and magnetic properties of a class of line defectembedded zigzag graphene nanoribbons, with one edge saturated by two hydrogen atoms per carbon atom and the other edge terminated by only one hydrogen atom. Bcn nanoribbons28,33,33,38 only occur in zigzagedged graphene nanoribbons,3941 and not in armchairedged graphene nanoribbons, we investigate the effects of the local geometry of embedded graphene flakes on the electronic structure to unravel the origin of the half metallic electronic structure.
Bcn nanoribbons28,33,33,38 only occur in zigzagedged graphene nanoribbons,3941 and not in armchairedged graphene nanoribbons, we investigate the effects of the local geometry of embedded graphene flakes on the electronic structure to unravel the origin of the halfmetallic electronic structure. To this end, we study, from first principles, six different oxidation schemes of a 1. An effective approach to achieve a spin gapless semiconductorhalf. Periodically functionalized graphene can mimic electronic behavior of edgemodified zgnrs as the edgemodified zigzag carbon chains effectively divide a. Inhomogeneous straininduced half metallicity in bent zigzag graphene nanoribbons. The existence of curious materials called half metals is predicted. Independent of ribbon width, fully hydrogenated armchair bnnrs are nonmagnetic semiconductors, while the zigzag counterparts are magnetic and metallic. Materials design of halfmetallic graphene and graphene nanoribbons.
The role of proximity contact with magnetic oxides is of particular interest from the expectations of the induced spin polarization and weak interactions at the graphene magnetic oxide interfaces, which would allow us to achieve efficient spinpolarized injection in graphene based spintronic devices. The intriguing electronic and magnetic properties of fully and partially hydrogenated boron nitride nanoribbons bnnrs were investigated by means of firstprinciples computations. 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. Halfmetallic ferromagnetism in substitutionally doped. Will metallic graphene nanoribbons someday replace copper. So we predict a metal free planar ferromagnetic half metallic holey. More important, edge oxidation is found to lower the onset electric field required to induce half metallic behavior and extend the overall field range at which the systems remain half metallic. Scalable templated growth of graphene nanoribbons on sic m. The magnetic edge state and half metallicity in zigzag graphene nanoribbons are particularly promising son et al 2006 nature 444 347. A transition from a metal to semiconductor is observed in the armchair c 3 n nanoribbons when the edge. 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. 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.
They noted that when doping nanoribbons, edgetype and substitutional doping induce different electronic properties to the systems and, in some cases, halfmetallic behavior. First flashes of light observed from individual graphene. Controlling halfmetallicity of graphene nanoribbons by. Realizing magnetism in graphene nanostructures is a decadelong challenge. Graphene ribbons were introduced as a theoretical model by mitsutaka fujita and coauthors to examine the edge and nanoscale size effect in graphene.
Although all halfmetals are ferromagnetic or ferrimagnetic, most ferromagnets are not halfmetals. Nov 16, 2006 here we predict half metallicity in nanometrescale graphene ribbons by using firstprinciples calculations. Graphene nanoribbons gnrs, also called nanographene ribbons or nanographite ribbons are strips of graphene with width less than 50 nm. Bromination of graphene with pentagonal, hexagonal zigzag. In this study, changes in electronic properties of crystal by doping lithium li atom to zgnr structure are analyzed. 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. Download citation halfmetallic graphene nanoribbons electrical. Although many chemical modification schemes for achieving half metallicity in zigzagedged graphene nanoribbons zgnrs have been proposed, practically, half metallic 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. Within the framework of linear response theory at the perturbation regime, we examine the optical infrared absorption threshold energy, absorption power, dielectric function. 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. On page 1507, guangtao yu, xuri huang, zhongfang chen, and co. Dec 15, 2015 graphene nanoribbons have been suggested as ideal wires for use in future nanoelectronics. Half metal phase in the zigzag phosphorene nanoribbon nature. Thermal spin filtering effect and giant magnetoresistance of halfmetallic graphene nanoribbon codoped with nonmetallic nitrogen and boron.
Here we predict halfmetallicity in nanometrescale graphene ribbons by using firstprinciples calculations. Graphene nanoribbons exfoliated from graphite surface dislocation bands by electrostatic force anton n sidorov1, 23, tanesh bansal,pjouseph1 and gamini sumanasekera1,4 1 department of physics, university of louisville, louisville, ky 40292, usa 2 department of electrical and computer engineering, university of louisville, ky 40208, usa. 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. Graphene nanoribbons gnrs have onedimensional structures. Nov 16, 2006 the existence of curious materials called half metals is predicted. In contrast to graphene nanoribbon29, our proposal does not require. Graphene nanoribbons gnrs, also called nano graphene ribbons or nanographite ribbons are strips of graphene with width less than 50 nm. 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. Edgemodified zigzag graphene nanoribbons zgnr are investigated with density functional theory. 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. The role of proximity contact with magnetic oxides is of particular interest from the expectations of the induced spin polarization and weak interactions at the graphenemagnetic oxide interfaces, which would allow us to achieve efficient spinpolarized injection in graphenebased spintronic devices.
Nano letters enhanced halfmetallicity in edgeoxidized. 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. Once the half metallic state is reached, further increase. Metalmetal transition in zigzag graphene nanoribbons.
Thermal spin filtering effect and giant magnetoresistance of. Based on firstprinciples calculations, we present the electronic and magnetic properties of a class of line defectembedded zigzag graphene nanoribbons, with one edge saturated by two hydrogen atoms per carbon atom and the other edge terminated by only one. Pdf materials design of halfmetallic graphene and graphene. Future studies will focus on allgraphene devices combining both metallic and semiconducting graphene nanostructures.
A combined approach of topmostsurfacesensitive spectroscopy utilizing spinpolarized. Periodically functionalized graphene can mimic electronic behavior of edgemodified zgnrs as the edgemodified zigzag carbon chains effectively divide a graphene. For the first time, researchers have experimentally observed light emission from individual graphene nanoribbons. Once the halfmetallic state is reached, further increase. A half metal 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. The halfmetallicity of zigzag graphene nanoribbons with. Halfmetallic graphene nanoribbons youngwoo son, 1,2marvin l. These results open the door to using graphene in future electronic devices, where these ultranarrow ribbons could replace copper as the interconnect material. Zgnrhalf turns to half metal when it is wider than 12zigzag chains.
Enhanced half metallicity in the zigzag graphene nanoribbons by adsorption of the zigzag hydrogen fluoride molecular chains. Materials design of half metallic graphene and graphene nanoribbons. Electronic states of graphene nanoribbons and analytical. Materials design of halfmetallic graphene and graphene nanoribbons menghao wu university of nebraskalincoln. 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. A metal free ferromagnet with charge and spin current rectification. Intrinsic halfmetallicity in modified graphene nanoribbons. Although all half metals are ferromagnetic or ferrimagnetic, most ferromagnets are not half metals. 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. Low temperature and temperaturedependent measurements reveal a length and orientation. Among those methods, dft calculations adopt parameterfree self consistent field. Intrinsic half metallicity in modified graphene nanoribbons.
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. They noted that when doping nanoribbons, edgetype and substitutional doping induce different electronic properties to the systems and, in some cases, half metallic behavior. Sep 01, 2015 read tunable half metallic 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 your fingertips. More important, edge oxidation is found to lower the onset electric field required to induce halfmetallic behavior and extend the overall field range at which the systems remain halfmetallic. The bromination reactivity of azulene, naphthalene, and graphene with pentagonal, hexagonal zigzag and armchair, and heptagonal edges was theoretically estimated by density functional theory calculation and experimentally clarified by analyzing bromination of azulene and naphthalene using gas chromatographymass spectrometry and ultravioletvisible spectroscopy. 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. Metal free magnetism and halfmetallicity of carbon nitride nanotubes. High spin filter efficiency is expected to be realized in halfmetallic materials with one metallic spin component and the other semiconducting or. Free energy analysis suggests that edgemodification is a practical way in experiment to. Nov 16, 2006 firstprinciples calculations predict that half metallic behaviour can be found in nanometrescale ribbons of graphene, in practically realistic conditions.
Graphene nanoribbons have been suggested as ideal wires for use in future nanoelectronics. In summary, we observe the halfmetallic property in an armchair graphene nanoribbon in contact with ni electrodes. Utilizing firstprinciples theory, we demonstrate that halfmetallicity can be realized in a junction composed of nonmagnetic armchair graphene nanoribbon agnr and ferromagnetic ni electrodes. Electronic properties of lidoped zigzag graphene nanoribbons. It is the basic structural element of other allotropes, including graphite, charcoal, carbon nanotubes and fullerenes. Enhanced halfmetallicity in edgeoxidized zigzag graphene. Half metallic graphene nanoribbons youngwoo son, 1,2marvin l. Half metallic materials are characterized by the coexistence of metallic behaviour for one electron spin and insulating behaviour. Materials design of halfmetallic graphene and graphene. Zigzag graphene nanoribbons zgnrs are known to exhibit metallic behavior. Dec 15, 2015 researchers have succeeded in experimentally realizing metallic graphene nanoribbons gnrs that are only 5 carbon atoms wide. Hui wu, guanghui chen, yunpeng yu, di wu and qiang wang. 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. All the calculations presented in this work were carried out.
Born january 9, 1928 in paris german chemist professor emeritus in ludwigmaximillians university in munich,germany pioneer of graphene research. Theoretical exploration of the halfmetallicity of graphene nanoribbonsboron nitride bilayer system. Jan 10, 2018 for the first time, researchers have experimentally observed light emission from individual graphene nanoribbons. So we predict a metal free planar ferromagnetic halfmetallic holey. Such modification has a significant impact on the zgnr electronic structure. Depending on structural properties such as edge status, doping and width of nanoribbons, the electronic properties of these structures may vary. It can also be considered as an indefinitely large aromatic molecule, the ultimate case of the family of. Oct, 2016 utilizing firstprinciples theory, we demonstrate that half metallicity can be realized in a junction composed of nonmagnetic armchair graphene nanoribbon agnr and ferromagnetic ni electrodes. Tunable halfmetallic properties and spin seebeck effects.
High quality graphene nanoribbons epitaxially grown on the sidewalls of silicon carbide sic. The existence of nitrogen atoms in the edge of the ribbons increases the stability and magnetization of the ribbons and make them different from graphene nanoribbons. Firstprinciples calculations predict that half metallic behaviour can be found in nanometrescale ribbons of graphene, in practically realistic conditions. Infrared optical response of metallic graphene nanoribbons. However, its experimental realization has been hindered by the stringent requirement of the monohydrogenated zigzag edge. The half metallic property originates from the agnr energy gap of the up spin located at the fermi energy, while large electronic states are generated for the down spin. Prediction of twodimensional materials with half metallic dirac cones. This article is brought to you for free and open access by the published research department of chemistry at. Edgeinsensitive magnetism and half metallicity in graphene.
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