Synthesis of n 8 armchair graphene nanoribbons from four. An armchair ribbon can be thought of as essentially an unrolled zigzag nanotube. Intrinsic spinorbit coupling in zigzag and armchair graphene. We demonstrated an efficient edgereconstruction process, at the atomic scale, for graphitic nanoribbons by joule heating. Starting from a tightbinding model, we derive the energy gaps induced by intrinsic spinorbit iso coupling in the lowenergy band structures of graphene nanoribbons. Graphene nanoribbon arrays, methods of growing graphene nanoribbon arrays and electronic and photonic devices incorporating the graphene nanoribbon arrays are provided. Transport properties of two finite armchair graphene nanoribbons. Graphene nanoribbons gnrs, narrow and straightedged stripes of graphene, attract a great deal of attention because of their excellent electronic and magnetic properties. Results show that the effect of vacancies in zigzag graphene nanoribbon is more profound than in armchair graphene nanoribbon. Jul 23, 2012 according to the geometry of their edge, in their simplest forms, they can be either armchair agnrs or zigzag zgnrs, although more complicated gn. If a graphene nanoribbon runs in the armchair direction, that is, if the long edge of a ribbon shows an armchair pattern, then it is referred to as as an armchair. On adsorption of h 2 s, the variations in original metallic behaviour of zgnr and semiconducting behaviour of agnr has further been analysed by observing the conductance and bandgap variation as a. The propagating modes in each valley contain a single. The graphene nanoribbons with long and reactive edges that are prone to localized electronic states display ferromagnetism at room temperature.
Although ab initio methods have been used to compute the currentvoltage characteristics of deformed nanoribbons, analytical models that embody fundamental quantum electron transmission concepts are needed to support the conceptual design of new nanoelectromechanical devices. Optical imaging and spectroscopy of atomically precise. Ultranarrow metallic armchair graphene nanoribbons nature. It is the first twodimensional material and it was obtained by mechanical exfoliation in 2004 novoselov et al. And depending on how the ribbon is cut out, it results in either an armchair or a zigzag edge. In order to realize highly anisotropic ribbons, it is critical to. Pdf introduction to quantumatk atk reference manual docs tutorials tubes, ribbons and other 1d nanostructures transport in graphene nanoribbons transport in graphene nanoribbons version. Electronic properties of twisted armchair graphene nanoribbons. Graphene is a oneatomiclayer thick twodimensional material made of carbon atoms arranged in a honeycomb structure.
The electronic band structures, geometries, density of states, binding energies, band gap information, and formation energies of related structures are calculated. 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. Armchair graphene nanoribbons might provide the next leap in semiconductor technology. Atoms along the edge of a zigzag gnr zgnr come from the same sublattice of graphene, whereas atoms from two different sublattices form bonds along the edge of an armchair gnr agnr.
For the graphene nanoribbons with all oxygen atoms on the edges, both band. Pdf transport properties of two finite armchair graphene. Electrical properties of carbon structures graphene. The armchair graphene nanoribbons may be either semiconducting or metallic, depending on their widths in the absence of iso interactions. Nanoribbons graphene is a oneatom thick sheet of graphite which made of carbon atoms arranged in a hexagonal lattice.
The d band raman intensity is calculated for armchair edged graphene nanoribbons using an extended tightbinding method in which the effect of interactions up to the seventh nearest neighbor is. Onsurface synthesis and characterization of 9atom wide. Graphene nanoribbons gnrs are quasi one dimensional cuts of graphene. These edge topologies include armchair, chevron, cove, and zigzag. 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. Graphene nanoribbons gnrs are a new class of materials that have promising applications in nextgeneration nanoelectronic and optoelectronic. Scalable and precise synthesis of armchairedge graphene. Graphene ribbons were introduced as a theoretical model by mitsutaka fujita and coauthors to examine the edge and nanoscale size effect in graphene.
Electrical properties of carbon structures graphene nanoribbons. Pdas 1 and 2ac are themselves easily accessed through photochemically initiated topochemical polymerization of diynes 3 and 4ac in the. The carboncarbon bond length in graphene is about 0. The chemical nature or bonding energies between zigzag and armchair graphene nanoribbons differs, which can impact functionalization or forming chemical modifications such as fluorographene, chlorographene, graphene oxide and other functionalized graphene. Ferromagnetism in armchair graphene nanoribbons hsiuhau lin department of physics, national tsinghua university, hsinchu 300, taiwan and physics division, national center for theoretical sciences, hsinchu 300, taiwan toshiya hikihara department of physics, hokkaido university, sapporo 0600810, japan horngtay jeng. Controlled formation of sharp zigzag and armchair edges in. The gnrs considered have either armchair or zigzag shaped edges on both sides with hydrogen passivation. Armchair graphene nanoribbons with different proportions of edge oxygen atoms.
Angleresolved photoelectron spectroscopy and scanning tunneling spectroscopy data from armchair graphene nanoribbons of width n 7 supported on au111 reveal a band gap of 2. Modulating magnetism of nitrogendoped zigzag graphene nanoribbons zhao shangqian, lu yan, lu wengang et al. Also, the effect of double vacancy defect on the ultimate failure stress is greater in zigzag graphene nanoribbons than in armchair graphene nanoribbon due to bond orientation with respect to loading direction. Analytical study of electronic structure in armchair graphene nanoribbons huaixiu zheng,1 zhengfei wang, 2tao luo, qinwei shi,2. Low thermal conductivity of paperclipshaped graphene superlattice nanoribbons lu xing and zhong weirongrecent citations mocl 5 intercalation doping and oxygen. Analytical study of electronic structure in armchair. The unzipping process is schematically shown in figure 3. A unified currentvoltage iv model of uniaxial strained armchair graphene nanoribbons agnrs incorporating quantum confinement effects is presented in this paper. Here, we introduce a novel approach to access the frontier states of armchair graphene nanoribbons agnrs. Department of physics, umea university, 90187 umea, sweden department of physics, university of california, berkeley, california 94720, united states. Box 110v, valpara so, 2390123, chile 1 international iberian nanotechnology laboratory, av. Pdf introduction to quantumatk atk reference manual docs. We report the optical imaging and absorption spectroscopy on atomically precise armchair graphene nanoribbons gnrs on insulating fused silica substrates. We measure the linear absorption spectra of 7 armchair and.
By plasma etching, graphene nanoribbons with smooth edges and a narrow width of 1020 nm were successfully obtained 1. Charge transport mechanism in networks of armchair graphene. Pdas 1 and 2ac are themselves easily accessed through photochemically initiated topochemical polymerization of diynes 3 and 4ac in the crystal. Both armchair graphene nanoribbons agnrs and zigzag graphene nanoribbons. Pdf electronic properties of armchair graphene nanoribbons. Knezevic department of electrical and computer engineering, university of wisconsinmadison, madison, wisconsin 53706, usa received 30 june 2017. In graphene nanoribbons with zigzag edges zigzag nanoribbons, two valleys related to each dirac spectrum are well separated in momentum space. Double vacancy defects were introduced in each graphene nanoribbon at its center or at. Here, we report on the formation of quantum dots embedded in an armchair gnr by substitutional inclusion of pairs of boron atoms into the gnr backbone. Important band structure parameters are computed, e. Lithium adsorption on armchair graphene nanoribbons.
Intrinsic spinorbit coupling in zigzag and armchair. Ab initio study of folded armchair graphene nanoribbons a. Coronenebased graphene nanoribbons insulated by boron. For n7 armchair graphene nanoribbons, the optical response is dominated by absorption features at 2. Since its discovery, graphene attracted extensive attention of researchers because of its extraordinary mechanical ovidko, 20, thermal balandin, 2011, and electrical properties chu et al. Engineering the band gap of armchair graphene nanoribbons. Table of contents 1 transport in graphene nanoribbons 2. We report electronic structure and electric field modulation calculations in the width direction for armchair graphene nanoribbons acgnrs using a semiempirical extended huckel theory. The electronic properties of graphene nanoribbons grown on metal substrates are significantly masked by the ones of the supporting metal surface. Graphene is the basic structural element of some carbon allotropes including graphite charcoal carbon nanotubes fullerence chemical structures. Armchairedged graphene nanoribbons, which are energetically stable, have a ribbonwidthdependent intrinsic energy gap, while zigzagedged ones have spinpolarized nonbonding edge states in the vicinity of the edge region. Ab initio study of ruterminated and rudoped armchair.
Carbon nanotubes are usually labeled in terms of the chiral vectors which are also the directions that graphene sheets are rolled. Not just carbon nan otubes, the metallic property of graphene sheet limits its application to semiconductor devices. Comparison of fracture behavior of defective armchair and. Graphene is one layer of hexagonal lattice of carbon atoms. We investigate the effects of ruthenium ru termination and ru doping on the electronic properties of armchair graphene nanoribbons agnrs using firstprinciples methods.
Graphene nanoribbons have intriguing electronic structures, which are large edge geometry dependent. Pignedoli, klaus mullen, akimitsu narita2,3, roman fasel1,4, and pascal ruffieux1, 1empa, swiss federal laboratories for materials science and technology, 8600 dubendorf, switzerland. Quantum dots embedded in graphene nanoribbons by chemical. Pdf we investigate the electronic band structure of an undoped graphene armchair nanoribbon. Magnetically coupled spin states in armchair graphene. Mar 27, 2009 graphene nanoribbons can exhibit either quasimetallic or semiconducting behavior, depending on the atomic structure of their edges. 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. Similar to armchair nanotubes, it has been predicted that ribbons with zigzag edges are all metallic7 and may present interesting magnetic properties. Graphene nanoribbons can exhibit either quasimetallic or semiconducting behavior, depending on the atomic structure of their edges. A systematic investigation is performed on the electronic transport properties of armchairgraphene nanoribbon agnr heterojunctions using spinpolarized density functional theory calculations in combination with the nonequilibrium greens function formalism. The d band raman intensity is calculated for armchair edged graphene nanoribbons using an extended tightbinding method in which the effect of interactions up to the seventh nearest neighbor is taken into account. Carbon nanotubes and graphene nanoribbons can be viewed as single molecules in a nanometer scale. Onsurface synthesis and characterization of 9atom wide armchair graphene nanoribbons. Unified drain current model of armchair graphene nanoribbons.
To compute the structural and electronic properties of armchair and zigzag graphene nanoribbons with and without h 2 s gas, near to its surface, the kpoint sampling of 1. We demonstrate that such nanoribbon always has a gap in. Transport properties of two finite armchair graphene. Mar 20, 2019 armchair graphene nanoribbons agnrs with 8 and 10 carbon atoms in width 8. Ab initio study of folded armchair graphene nanoribbons. Dft analysis of h2s adsorbed zigzag and armchair graphene. Conductance of buckled n 5 armchair graphene nanoribbons. It is well founded that the electronic properties of the. August 5, 2010 we present a rst principles approach to the characterization of multiply folded armchair graphene nanoribbons using the vienna abinitio simulation package, along with builtin ultrasoft psue. The properties of graphene nanoribbons are dependent on both the nanoribbon width and the crystallographic orientation of the edges. Thermal conductivity and thermal rectification in graphene. Electronic band structure of armchair and zigzag graphene.
Theoretical investigation on armchair graphene nanoribbons. Agnrs are synthesized on au 111 surfaces via lateral fusion of nanoribbons that belong to different subfamilies. Also, the effect of double vacancy defect on the ultimate failure stress is greater in zigzag graphene nanoribbons than in armchair graphene nanoribbon due to bond orientation with respect. Direct oriented growth of armchair graphene nanoribbons on.
In this article, by using the first principle calculations based on the density functional theory, we present a detailed investigation of the energy band and. Firstprinciple studies of armchair graphene nanoribbons iopscience. Dec 14, 2015 graphene nanoribbons gnrs are a new class of materials that have promising applications in nextgeneration nanoelectronic and optoelectronic devices 1,2,3. Distinguishing zigzag and armchair edges on graphene. We have investigated the effects of edge chirality and found that nanoribbons with zigzag edges have appreciably larger thermal conductivity than nanoribbons with armchair edges. Its fascinating electrical, optical, and mechanical properties ignited enormous interdisciplinary interest from the physics, chemistry, and materials science fields. Electronic structure of oxygen functionalized armchair graphene. Electromechanical coupling in graphene nanoribbons has been the focus of much basic research. Ultranarrow metallic armchair graphene nanoribbons.
The boron inclusion is achieved through the addition of a small amount of boron substituted precursors during. Analytical study of electronic structure in armchair graphene. We extensively characterize the electronic structure of ultranarrow graphene nanoribbons gnrs with armchair edges and zigzag termini that have five carbon atoms across their width 5agnrs, as synthesized on au111. Electronic transport in graphene nanoribbons kim group at harvard. Graphene nanoribbons are fundamental components to the development of graphene nanoelectronics. The nanoribbons are selfaligning 3 from the geh110i directions, are selfde. Graphene is the basic structural element of some carbon allotropes including graphite charcoal. At the nanoscale, electronic confinement effects and electronic edge states become essential to the. D band raman intensity calculation in armchair edged. Low temperature and temperaturedependent measurements reveal a length and orientation. The iv model is enhanced by integrating both linear and saturation regions into a unified and precise model of agnrs.
Thus, it is important to control the morphology and crystallinity of these edges for practical purposes. Armchair a and zigzag z type graphene nanoribbons gnr have been investigated for its suitability to sense the toxic h 2 s gas, by using density functional theory dft based abinitio approach. Pdf ferromagnetism in armchair graphene nanoribbons. Electronic transport properties of graphene nanoribbons. Armchair graphene nanoribbons e suhendi, r syariati, f a noor et al. Rationalizing and reconciling energy gaps and quantum confinement in narrow atomically precise armchair graphene nanoribbons. Pdf on mar 22, 2011, erjun kan and others published graphene nanoribbons. This is achieved by controlling light polarization on macroscopically aligned gnrs which greatly enhances the optical contrast of the submonolayer gnrs on the insulating substrates.
Coronenebased graphene nanoribbons insulated by boron nitride nanotubes. The relative stability of different adsorption sites is investigated taking into account different ribbon widths, adsorbate densities, and. The derivation originates from energy dispersion throughout the entire brillouin zone of uniaxial strained agnrs. Armchair graphene nanoribbons agnrs with 8 and 10 carbon atoms in width 8. Revealing the electronic structure of silicon intercalated. Charge transport mechanism in networks of armchair. Transport in graphene nanoribbons transport in graphene nanoribbons version. We demonstrate a highly efficient thermal conversion of four differently substituted polydiacetylenes pdas 1 and 2ac into virtually indistinguishable n 8 armchair graphene nanoribbons 8agnr. They can form zigzag, armchair, or chiral edge patterns. There are many forms of graphene nanoribbon gnr, but the armchair conformation is one the most studied because of their zeroband gap and high charge carrier mobility. The complex band structure for armchair graphene nanoribbons. Graphene nanoribbons with zigzag and armchair edges.
Structure of armchair and zigzag nanoribbons since gnrs are stripes of. Graphene nanoribbons gnrs have attracted attention as promising materials for nanosize electronics such as fieldeffect transistors. Low temperature and temperaturedependent measurements reveal a length. Scanning tunneling spectroscopy measurements on the ribbons, recorded on both the metallic substrate and a decoupling nacl layer, show welldefined dispersive bands and ingap. For the metallic ones, the gaps induced by iso coupling decrease with increasing ribbon. Graphene nanoribbons gnrs, also called nano graphene ribbons or nanographite ribbons are strips of graphene with width less than 50 nm. We report electronic structure and electricfield modulation calculations in the width direction for armchair graphene nanoribbons acgnrs using a. Both varieties of ribbons are shown to have band gaps. Finite, narrow strips of graphene are cut out from a twodimensional sheet of graphene to create the nanoribbons. Electronic structure and stability of semiconducting.
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