Request pdf energy bandgap engineering of graphene nanoribbons we investigate electronic transport in lithographically patterned. Energy bandgap engineering of graphene nanoribbons request. Abstract we investigate electronic transport in lithographically patterned graphene ribbon structures. One of the most important features of graphene nanoribbons, from both basic science and application points of view, is their electrical band gap 1.
Topological band engineering of graphene nanoribbons nature. One of the most recent advancements is the development of graphene nanoribbons gnrs layers of graphene with ultrathin width of. 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. 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.
Based on a firstprinciples approach, we present scaling rules for the band gaps of graphene nanoribbons gnrs as a function of their widths. 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. 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. We investigate electronic transport in lithographically patterned graphene ribbon structures where the lateral confinement of charge carriers creates an energy. Electronic and transport properties of defected graphene. Farajian, 2 keivan esfarjani, 3 and y oshiyuki kawazoe 1 1 institute for materials research, t ohoku. Experimentally engineering the edge termination of. The model hamiltonian describes the hopping of the.
Bottomup graphenenanoribbon fabrication reveals chiral. 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. Thus, graphene nanoribbons including constrictions show an overall semiconducting behaviour, which makes these quasi1d graphene nanostructures promising candidates for the. 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. Energy gaps in zerodimensional graphene nanoribbons. The absence of a band gap in graphene hinders its use in electronics. Widthdependent band gap in armchair graphene nanoribbons. Electronic transport in graphene nanoribbons kim group at harvard. Graphene nanoribbons gnrs, also called nano graphene ribbons or nanographite ribbons are strips of graphene with width less than 50 nm. The edges of graphene nanoribbons gnrs have attracted much interest due to their potentially strong influence on gnr electronic and magnetic properties. The demand for smaller and smaller electronic devices has led to great strides towards the use of novel materials like graphene.
However, in this latest work the researchers were not trying to achieve a band gap in graphene nanoribbons. Breakthrough in creating a band gap for graphene promises. Bandgap opening of graphene nanoribbons on vicinal sic. 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. Graphene nanoribbons gnrs have been proven to be unique conjugated polymers. Energy band gap engineering of graphene nanoribbons arxiv. Band gap engineering in doped graphene nanoribbons. We produce precise chiraledge graphene nanoribbons on cu111 using selfassembly and surfacedirected chemical reactions. While graphene a oneatom thick, honeycombshaped carbon layer is normally a conductive material, it can become a semiconductor when in the form of nanoribbons.
These ribbons are found to have small fermi energy differences. A topologically engineered graphene nanoribbon superlattice is presented that hosts a onedimensional array of halffilled, ingap localized electronic states, enabling band engineering. Jun 10, 2014 however, different from the email protectedn when n 3, the band gap was reduced to 0. Graphene nanoribbons with zigzag a and armchair b edges. By elucidating the molecularassembly mechanism, we. 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. The sizes of these energy gaps are investigated by measuring the conductance in the nonlinear response regime at low temperatures. Tuning the thermal conductivity of graphene nanoribbons by. The agnrs are doped with elements like i stype mg, ii ptype b and s and iii 3dtype tms ti and mn. Graphene ribbons were introduced as a theoretical model by mitsutaka fujita and coauthors to examine the edge and nanoscale size effect in graphene.
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. Sep 16, 2014 the successful fabrication of single layered graphene has generated a great deal of interest and research into graphene in recent years. Graphene nanoribbons 18 display unique electronic properties based on truly twodimensional 2d graphene 9 with potential applications in nanoelectronics 10,11. 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. Band gap engineering via edgefunctionalization of graphene nanoribbons article in the journal of physical chemistry c 11750. The gnrs considered have either armchair or zigzag shaped edges on both sides with hydrogen passivation. Band gap engineering of 2d nanomaterials and graphene. Han, barbaros ozyilmaz, yuanbo zhang, and philip kim. Using a combination of highresolution scanning tunneling microscopy and firstprinciples calculations, we have. The finite size effects on the electronic structure of graphene ribbons are studied using first principles density functional techniques.
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. Such control requires the development of fabrication tools capable of precisely controlling width and edge geometry of gnrs at the atomic scale. 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. Quasiparticle energies and band gaps in graphene nanoribbons. Highlights this paper analyzes the stability and electronic properties of armchair graphene nanoribbons agnrs. The black circles denote sublattice a, while the white circles refer to sublattice b. Color online band gap eg as a function of structural parameters of gnms. Simulation of energy band gap opening of graphene nano. It creates a band gap that allows the graphene to behave as a semiconductor that is, both as an electrical. Energy gaps of atomically precise armchair graphene nanoribbons.
The successful fabrication of single layered graphene has generated a great deal of interest and research into graphene in recent years. This work presents theoretical calculation of the band structures of. Energy band gap engineering of graphene nanoribbons. A prerequisite for future graphene nanoribbon gnr applications is the ability to finetune the electronic band gap of gnrs. Both varieties of ribbons are shown to have band gaps. Energy bandgap engineering of graphene nanoribbons. Graphene is a oneatomiclayer thick twodimensional material made of carbon atoms arranged in a honeycomb structure. Nov 10, 2016 the absence of a band gap in graphene hinders its use in electronics. Graphene nanoribbons gnrs, also called nanographene ribbons or nanographite ribbons are strips of graphene with width less than 50 nm. Spin and bandgap engineering in doped graphene nanoribbons narjes gorjizadeh, 1, amir a. Pdf spin and bandgap engineering in doped graphene.
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. As the number of bn chains increased, the band gap initially decreased, and then it increased. This effect could be used for nanoelectromechanical systems nems. 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. They were just developing a method for getting graphene nanoribbons down on a silicon wafer. One of the most recent advancements is the development of graphene nanoribbons gnrs layers of graphene with ultrathin width of less than 50 nm. We present here the tightbinding model hamiltonian taking into account of various interactions for tuning band gap in graphene. Band gap of strained graphene nanoribbons springerlink.
Han1, barbaros ozyilmaz2, yuanbo zhang2, and philip kim2 1department of applied physics, columbia university, new york, new york 10027. The tms as substitutional dopant in agnrs are energetically more favorable and minimize the band gap. However, different from the email protectedn when n 3, the band gap was reduced to 0. Electronic and transport properties of defected graphene nanoribbons 419 n1 2 3 5 a n1 2 3 8 b fig. 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. Engineering the band gap of armchair graphene nanoribbons. This is typically done to semiconductors by controlling the composition of alloys or constructing layered materials with alternating compositions. Modulation of the electron transport properties in. Chen5,b 1school of electrical and computer engineering, birck nanotechnology center, purdue university, west lafayette, indiana 47907, usa. Mind the gap with semiconducting graphene nanoribbons.
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. The intrinsic simplicity of nsl patterning enables this fabrication approach to be applicable for the. Tuning the thermal conductivity of graphene nanoribbons by edge passivation and isotope engineering. In lowenergy limit due to the approximation for the graphene band structure near the fermi point, the e k relation of the gnr. 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. A band gap is the range in a solid where no electron state can exist. Squeezing a band gap out of graphene materials today. Spin and band gap engineering in doped graphene nanoribbons narjes gorjizadeh, 1, amir a. Here we report the ability to engineer the microscopic edge termination of highquality gnrs via hydrogen plasma etching.
Here we report a technique for modifying gnr band gaps via covalent selfassembly of a new species of molecular precursors. Energy bandgap engineering of graphene nanoribbons nasaads. Graphene nanoribbon conductance model in parabolic band. 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. 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. Nanosphere lithography for the fabrication of ultranarrow.
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. Tuning the band gap of graphene nanoribbons synthesized. Its fascinating electrical, optical, and mechanical properties ignited enormous interdisciplinary interest from the physics, chemistry, and materials science fields. 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. 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. We have read this dissertation and recommend that it be approved. A molecular dynamics study jiuning hu,1,a stephen schif. Graphene nanoribbons get electrons to behave like photons. This work presents theoretical calculation of the band structures of graphene nano. 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.
We investigate electronic transport in lithographically patterned graphene ribbon structures where the lateral confinement of charge. Jul 25, 2007 the finite size effects on the electronic structure of graphene ribbons are studied using first principles density functional techniques. 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. 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. Graphene, being a gapless semiconductor, cannot be used in pristine form for nanoelectronic applications. In this letter, we show that gnrs with hydrogen passivated armchair or zigzag shaped edges both always have. Energy band gap engineering of graphene nanoribbons melinda y. A modular synthetic approach for bandgap engineering of. 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. A topologically engineered graphene nanoribbon superlattice is presented that hosts a onedimensional array of halffilled, in gap localized electronic states, enabling band engineering. Graphene nanoribbons, in contrast to truly twodimensional 2d graphene 1, exhibit an effective energy gap, which overcomes the gapless band structure of graphene.
Energy gaps in graphene nanoribbons youngwoo son,1,2 marvin l. This, together with graphene s high mobility and highcurrentcarrying capabilities, has motivated a large number of studies of graphene nanoribbons that we. Therefore, it is essential to generate a finite gap in the energy dispersion at dirac point. Bandgap engineering of bottomup synthesized graphene nano. Roomtemperature magnetism and tunable energy gaps in edge. 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.
Graphene nanoribbon gnr with parabolic band structure near the minimum band energy terminates fermidirac integral base method on band structure study. Quasiparticle energies and band gaps in graphene nanoribbons li yang,1,2 cheolhwan park,1,2 youngwoo son,3 marvin l. Energy bandgap engineering of graphene nanoribbons melinda y. They were just developing a method for getting graphene nanoribbons down. 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. Bandgap engineering is the process of controlling or altering the band gap of a material. Similarly, strain can induce changes in the electronic properties of graphene nanoribbons.
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