Energy gaps in graphene nanoribbons youngwoo son,1,2 marvin l. While graphene a oneatom thick, honeycombshaped carbon layer is normally a conductive material, it can become a semiconductor when in the form of nanoribbons. Bandgap opening of graphene nanoribbons on vicinal sic substrates kan nakatsuji1, takushi iimori 2, tsuguo yoshimura 2, yuya motomura 2, sunghun kim2, toshio miyamachi2, fumio komori2, takashi kajiwara 3, yuzuru nakamori 3, anton visikovskily 3 and satoru tanaka3 1dept. Graphene nanoribbons with zigzag a and armchair b edges. Therefore, it is essential to generate a finite gap in the energy dispersion at dirac point.
In this letter, we show that gnrs with hydrogen passivated armchair or zigzag shaped edges both always have. Graphene nanoribbons gnrs, also called nano graphene ribbons or nanographite ribbons are strips of graphene with width less than 50 nm. Graphene nanoribbons gnrs have been proven to be unique conjugated polymers. Bottomup graphenenanoribbon fabrication reveals chiral. Graphene nanoribbon conductance model in parabolic band. Electronic and transport properties of defected graphene nanoribbons 419 n1 2 3 5 a n1 2 3 8 b fig. Quasi1d graphene nanoribbons are of interest due to the presence of an effective energy gap, overcoming the gapless band structure of graphene and leading to overall. Roomtemperature magnetism and tunable energy gaps in edge. It creates a band gap that allows the graphene to behave as a semiconductor that is, both as an electrical. We investigate electronic transport in lithographically patterned graphene ribbon structures where the lateral confinement of charge. There are many forms of graphene nanoribbon gnr, but the armchair conformation is one the most studied because of their zero band gap and high charge carrier mobility. Although graphene has reached the attention of most researchers in the microelectronic field owing to its outstanding electronic properties 4,5, because graphene is a zero bandgap material and.
Nanosphere lithography for the fabrication of ultranarrow. While band structure is parabola, semiconducting gnrs conductance is a function of fermidirac integral which is based on maxwell approximation in nondegenerate limit especially for a long. By elucidating the molecularassembly mechanism, we. Based on a firstprinciples approach, we present scaling rules for the band gaps of graphene nanoribbons gnrs as a function of their widths. Energy band gap engineering of graphene nanoribbons.
We have read this dissertation and recommend that it be approved. Hydrogenated monolayer graphene with reversible and. Electronic and transport properties of defected graphene. Topological band engineering of graphene nanoribbons nature. This effect could be used for nanoelectromechanical systems nems.
Mind the gap with semiconducting graphene nanoribbons. Here we report the ability to engineer the microscopic edge termination of highquality gnrs via hydrogen plasma etching. Band gap engineering via edgefunctionalization of graphene nanoribbons article in the journal of physical chemistry c 11750. Although graphene has reached the attention of most researchers in the microelectronic field owing to its outstanding electronic properties 4,5, because graphene is a zero band gap material and. Bandgap opening of graphene nanoribbons on vicinal sic. Energy band gap engineering of graphene nanoribbons arxiv. Bandgap engineering of bottomup synthesized graphene nano. Graphene, being a gapless semiconductor, cannot be used in pristine form for nanoelectronic applications. Quasiparticle energies and band gaps in graphene nanoribbons li yang,1,2 cheolhwan park,1,2 youngwoo son,3 marvin l.
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. Energy band gap engineering of graphene nanoribbons melinda y. Pdf spin and bandgap engineering in doped graphene. Request pdf energy bandgap engineering of graphene nanoribbons we investigate electronic transport in lithographically patterned.
A band gap is the range in a solid where no electron state can exist. This, together with graphene s high mobility and highcurrentcarrying capabilities, has motivated a large number of studies of graphene nanoribbons that we. Energy gaps in zerodimensional graphene nanoribbons. In this research, we study the tunability of band gap in single and double layer graphene nano ribbons gnrs of specified widths and edge geometries. Thus, graphene nanoribbons including constrictions show an overall semiconducting behaviour, which makes these quasi1d graphene nanostructures promising candidates for the. The energy gap of the 1 dimensional graphene nanoribbons gnrs, can be produced lithographically by patterning 2 dimensional graphene through a chemical route different crystallographic orientations tuned with varying widths energy gap nahid shayesteh, physics department.
Engineering the band gap of armchair graphene nanoribbons. A molecular dynamics study jiuning hu,1,a stephen schif. Graphene nanoribbons, in contrast to truly twodimensional 2d graphene 1, exhibit an effective energy gap, which overcomes the gapless band structure of graphene. One of the most important features of graphene nanoribbons, from both basic science and application points of view, is their electrical band gap 1. Abstract we investigate electronic transport in lithographically patterned graphene ribbon structures. The absence of a band gap in graphene hinders its use in electronics. A topologically engineered graphene nanoribbon superlattice is presented that hosts a onedimensional array of halffilled, in gap localized electronic states, enabling band engineering. Louie1,2 1department of physics, university of california at berkeley, california 94720, usa 2materials sciences division, lawrence berkeley national laboratory, berkeley, california 94720, usa 3department of physics, konkuk university, seoul 143701, korea. Squeezing a band gap out of graphene materials today. One of the most recent advancements is the development of graphene nanoribbons gnrs layers of graphene with ultrathin width of less than 50 nm. In figure 3, the band gaps were larger in the email protectedn system than in the email protectedn system, illustrating the effect on the band gap in.
One of the fundamental problems for graphene was its lack of a band gap, which left it with a very low onoff ratio measured at about 10 as compared to in the 100s for silicon. The energy gap difference between highest occupied molecular orbital homo and lowest unoccupied molecular orbital lumo dependence for finite width and length is computed for both armchair and zigzag ribbons and compared to their onedimensional. Tuning the thermal conductivity of graphene nanoribbons by edge passivation and isotope engineering. Simulation of energy band gap opening of graphene nano. We present here the tightbinding model hamiltonian taking into account of various interactions for tuning band gap in graphene. Farajian, 2 keivan esfarjani, 3 and y oshiyuki kawazoe 1 1 institute for materials research, t ohoku.
Energy bandgap engineering of graphene nanoribbons melinda y. Graphene nanoribbons 18 display unique electronic properties based on truly twodimensional 2d graphene 9 with potential applications in nanoelectronics 10,11. However, different from the email protectedn when n 3, the band gap was reduced to 0. Tuning the thermal conductivity of graphene nanoribbons by. This is typically done to semiconductors by controlling the composition of alloys or constructing layered materials with alternating compositions. Engineering techniques that use finite size effect to introduce tunable edge magnetism and energy gap are by far the most promising ways for enabling graphene 1 to be used in electronics and. Electronic transport in graphene nanoribbons kim group at harvard. They were just developing a method for getting graphene nanoribbons down on a silicon wafer. Similarly, strain can induce changes in the electronic properties of graphene nanoribbons. The black circles denote sublattice a, while the white circles refer to sublattice b. The tms as substitutional dopant in agnrs are energetically more favorable and minimize the band gap. Widthdependent band gap in armchair graphene nanoribbons. The demand for smaller and smaller electronic devices has led to great strides towards the use of novel materials like graphene. Energy bandgap engineering of graphene nanoribbons.
Sep 16, 2014 the successful fabrication of single layered graphene has generated a great deal of interest and research into graphene in recent years. This dissertation, written by md monirojjaman monshi and entitled band gap engineering of 2d nanomaterials and graphene based heterostructure devices, having been approved in respect to style and intellectual content, is referred to you for judgment. Jun 10, 2014 however, different from the email protectedn when n 3, the band gap was reduced to 0. The model hamiltonian describes the hopping of the. Using a combination of highresolution scanning tunneling microscopy and firstprinciples calculations, we have. Band gap opening of graphene nanoribbons on vicinal sic substrates kan nakatsuji1, takushi iimori 2, tsuguo yoshimura 2, yuya motomura 2, sunghun kim2, toshio miyamachi2, fumio komori2, takashi kajiwara 3, yuzuru nakamori 3, anton visikovskily 3 and satoru tanaka3 1dept. Han, barbaros ozyilmaz, yuanbo zhang, and philip kim. We find that the energy gap scales inversely with the ribbon width, thus demonstrating the ability to engineer the band gap of graphene nanostructures by lithographic processes. Graphene nanoribbons gnrs, also called nanographene ribbons or nanographite ribbons are strips of graphene with width less than 50 nm. Graphene ribbons were introduced as a theoretical model by mitsutaka fujita and coauthors to examine the edge and nanoscale size effect in graphene. Band gap engineering of 2d nanomaterials and graphene.
Energy bandgap engineering of graphene nanoribbons request. This work presents theoretical calculation of the band structures of. Tuning the band gap of graphene nanoribbons synthesized. We produce precise chiraledge graphene nanoribbons on cu111 using selfassembly and surfacedirected chemical reactions. Chen5,b 1school of electrical and computer engineering, birck nanotechnology center, purdue university, west lafayette, indiana 47907, usa. Han1, barbaros ozyilmaz2, yuanbo zhang2, and philip kim2 1department of applied physics, columbia university, new york, new york 10027. Band gap of strained graphene nanoribbons springerlink. Both varieties of ribbons are shown to have band gaps. Graphene nanoribbon gnr with parabolic band structure near the minimum band energy terminates fermidirac integral base method on band structure study. The finite size effects on the electronic structure of graphene ribbons are studied using first principles density functional techniques. Graphene is a oneatomiclayer thick twodimensional material made of carbon atoms arranged in a honeycomb structure.
Breakthrough in creating a band gap for graphene promises. One of the most recent advancements is the development of graphene nanoribbons gnrs layers of graphene with ultrathin width of. Graphene nanoribbons have a sufficiently large energy or band gap where no electron states can exist, which means they can be turned on and off and thus could become a key. Nov 10, 2016 the absence of a band gap in graphene hinders its use in electronics. A prerequisite for future graphene nanoribbon gnr applications is the ability to finetune the electronic band gap of gnrs. The gnrs considered have either armchair or zigzag shaped edges on both sides with hydrogen passivation. Graphene nanoribbons get electrons to behave like photons. 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. However, in this latest work the researchers were not trying to achieve a band gap in graphene nanoribbons.
Experimentally engineering the edge termination of. Such control requires the development of fabrication tools capable of precisely controlling width and edge geometry of gnrs at the atomic scale. A topologically engineered graphene nanoribbon superlattice is presented that hosts a onedimensional array of halffilled, ingap localized electronic states, enabling band engineering. Modulation of the electron transport properties in. When graphene is sandwiched between layers of boron nitride bn, an atomicallythin electrical insulator, and the two materials are rotationally aligned, the bn has been shown to modify the electronic structure of the graphene. In lowenergy limit due to the approximation for the graphene band structure near the fermi point, the e k relation of the gnr. Simulation of energy band gap opening of graphene nano ribbons. Highlights this paper analyzes the stability and electronic properties of armchair graphene nanoribbons agnrs. We show that, using specific properties of the substrate, we can change the edge conformation of the nanoribbons, segregate their adsorption chiralities, and restrict their growth directions at low surface coverage. 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. The agnrs are doped with elements like i stype mg, ii ptype b and s and iii 3dtype tms ti and mn.
The sizes of these energy gaps are investigated by measuring the conductance in the nonlinear response regime at low temperatures. Band gap engineering in doped graphene nanoribbons. As the number of bn chains increased, the band gap initially decreased, and then it increased. A modular synthetic approach for bandgap engineering of. Quasiparticle energies and band gaps in graphene nanoribbons. Energy gaps of atomically precise armchair graphene nanoribbons. Nov 24, 2006 based on a firstprinciples approach, we present scaling rules for the band gaps of graphene nanoribbons gnrs as a function of their widths. One of the obstacles to the use of graphene is its lack of band gap, meaning it is difficult to use in digital electronics that. The successful fabrication of single layered graphene has generated a great deal of interest and research into graphene in recent years. In addition, it has been found that the electronic properties, and in particular the band gap of fewlayer graphene is strongly modulated by the interlayer distance.
Energy bandgap engineering of graphene nanoribbons nasaads. The intrinsic simplicity of nsl patterning enables this fabrication approach to be applicable for the. Jul 25, 2007 the finite size effects on the electronic structure of graphene ribbons are studied using first principles density functional techniques. Its fascinating electrical, optical, and mechanical properties ignited enormous interdisciplinary interest from the physics, chemistry, and materials science fields. The edges of graphene nanoribbons gnrs have attracted much interest due to their potentially strong influence on gnr electronic and magnetic properties. Spin and bandgap engineering in doped graphene nanoribbons narjes gorjizadeh, 1, amir a. 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. Spin and band gap engineering in doped graphene nanoribbons narjes gorjizadeh, 1, amir a. An innovative approach for the highthroughput, rapid, and lowcost fabrication of ultranarrow graphene nanoribbons gnrs using nanosphere lithography nsl nanopatterning in combination with lowpower o 2 plasma etching is presented. Bandgap engineering is the process of controlling or altering the band gap of a material. These ribbons are found to have small fermi energy differences. We investigate electronic transport in lithographically patterned graphene ribbon structures where the lateral confinement of charge carriers creates an energy. Color online band gap eg as a function of structural parameters of gnms.
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. Here we report a technique for modifying gnr band gaps via covalent selfassembly of a new species of molecular precursors. This work presents theoretical calculation of the band structures of graphene nano. They were just developing a method for getting graphene nanoribbons down.
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