Energy band gap engineering of graphene nanoribbons pdf

A prerequisite for future graphene nanoribbon gnr applications is the ability to finetune the electronic band gap of gnrs. Its fascinating electrical, optical, and mechanical properties ignited enormous interdisciplinary interest from the physics, chemistry, and materials science fields. Graphene nanostructures, where quantum confinement opens an energy gap in the band structure, hold promise for future electronic devices. It is also observed that the dos structure and electronic bandgap are affected by changing the locations of the p impurities. Quasi1d graphene nanoribbons are of interest due to the presence of an effective energy gap, overcoming the gap less band structure of graphene and leading to overall. 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. The tms as substitutional dopant in agnrs are energetically more favorable and minimize the band gap. 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.

We have read this dissertation and recommend that it be approved. 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. We report that the electronic band gap energy of h. Electronic transport in graphene nanoribbons kim group at harvard. Band gap opening of a singlelayer graphene nanoribbon sgnr sitting on another sgnr, fabricated by drop casting gnr solution on au111 substrate in air, was studied by means of scanning tunneling microscopy and spectroscopy in an ultrahigh vacuum at 78 k and 300 k. Strainengineering of band gaps in piezoelectric boron. Band gap engineering in finite elongated graphene nanoribbon. Unfortunately, extrinsic treatments designed to open a band gap seriously degrade device quality, yielding very low mobility and uncontrolled onoff current ratios. Graphene field effect transistor without an energy gap.

Band gap engineering of 2d nanomaterials and graphene. 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. Energy bandgap engineering of graphene nanoribbons melinda y. We investigate electronic transport in lithographically patterned graphene ribbon structures where the lateral confinement of charge. Energy gaps in graphene nanoribbons youngwoo son,1,2 marvin l. Substituting heteroatoms into nanostructured graphene elements, such as graphene nanoribbons, offers the possibility for atomic engineering of electronic properties. Band gap engineering in armchairedged graphene nanoribbons. Energy band gap engineering of graphene nanoribbons core. May 28, 20 thus, previous efforts to realize a field effect transistor for logic applications have assumed that introduction of a band gap in graphene is a prerequisite. Energy bandgap engineering of graphene nanoribbon by. Bottomup fabrication of atomically precise graphene nanoribbons. Low temperature and temperaturedependent measurements reveal a length and orientation.

Pdf spin and bandgap engineering in doped graphene nanoribbons. The sizes of these energy gaps are investigated by measuring the conductance in the nonlinear response regime at low temps. Energy band gap engineering of graphene nanoribbons open. Tuning the band gap of graphene nanoribbons synthesized from. One of the ways to use graphene in field effect transistors is to introduce a band gap by quantum confinement effect. 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. Number of manuscripts with graphene in the title posted on the preprint server. Competing gap opening mechanisms of monolayer graphene. Such control requires the development of fabrication tools capable of precisely controlling width and edge geometry of gnrs at the atomic scale. When lithographically generated graphene ribbons are laterally confined in charge it creates an energy gap near the charge neutrality point. 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 bandgap engineering of graphene nanoribbons nasaads. Low temperature and temperaturedependent measurements reveal a length.

Bandgap engineering of graphene nanoribbons by control. Energy band gap engineering of graphene nanoribbons melinda y. Request pdf energy bandgap engineering of graphene nanoribbons we investigate electronic transport in lithographically patterned. However, the smallest details in the atomic structure of these graphene bands have massive effects on the size of the energy gap and thus on the suitability of nanoribbons as components of transistors. Energy bandgap engineering of graphene nanoribbons request. Graphene nanoribbons gnrs are onedimensional 1d structures that exhibit a rich variety of. In the present paper, several programs of graphene nanoribbons band gap engineering. Gnrs with a width of 45 nm were prepared by unzipping doublewalled carbon nanotubes diameter 15 nm using the. Silicon nitride gate dielectrics and band gap engineering in graphene layers wenjuan zhu, deborah neumayer, vasili perebeinos, and phaedon avouris ibm thomas j. Based on theoretical analysis, it is found that the modification in the columbic potential profiles in the periodic direction is the origin of multiple band gap values in the. We propose that this gap is created when the graphene lattices symmetry is broken as a result of the interaction between the graphene and the substrate, and we believe that these results highlight a promising direction for the bandgap engineering of. Kim energy band gap engineering of graphene nanoribbons phys. Energy band gap engineering of graphene nanoribbons arxiv.

Band gap opening of a singlelayer graphene nanoribbon sgnr sitting on another sgnr, fabricated by drop casting gnr solution on au111 substrate in air, was studied by means of. However, the lack of an energy band gap in graphene limits its use in logic applications. The agnrs are doped with elements like i stype mg, ii ptype b and s and iii 3dtype tms ti and mn. Multiple heteroatom substitution to graphene nanoribbon. This manifestation of nontrivial onedimensional topological phases presents a route to band engineering in onedimensional materials based on precise. 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. Avouris 100ghz transistors from waferscale epitaxial graphene science vol. Obviously, the same results can be expected for silicene zigzag nanoribbons siznrs if parallel. Graphene ribbons were introduced as a theoretical model by mitsutaka fujita and coauthors to examine the edge and nanoscale size effect in graphene. Graphene nanoribbons are among the recently discovered carbon nanostructures, with unique characteristics for novel applications. This configuration reduces the overall ribbon energy and readily provides an.

The smallest details in the atomic structure of these graphene bands, however, have massive effects on the size of the energy gap, and thus on how wellsuited nanoribbons are as components of. Watson research center, yorktown heights, new york 10598 abstract we show that silicon nitride can provide uniform coverage of graphene in. Simulation of energy band gap opening of graphene nano ribbons anas m m1, roy paily2 1ece dept. One of the problems that limit the application of graphene in electronic devices is the absence of an intrinsic band gap. In terms of the materials electronic energy band structure, the band gap is the energy difference between the top of the valence band and the bottom of the conduction band. It is the basic structural element of other allotropes, including graphite, charcoal, carbon nanotubes and fullerenes. Coronenebased graphene nanoribbons insulated by boron. Simulation of energy band gap opening of graphene nano ribbons.

Suppression of electronvibron coupling in graphene. The trend in band gap change is consistent with the trend in the formation energy in reflecting the relative stability of the agnrs with different hydrogenations. Angledependent bandgap engineering in gated graphene. We present here the tightbinding model hamiltonian taking into account of various interactions for tuning band gap in graphene. Bandgap engineering or band structure engineering is a term coined in the late eighties to refer to a powerful technique for the design of new semiconductor materials and device. Toward coveedged low band gap graphene nanoribbons journal. Recent progress in fabrication techniques of graphene.

Nevertheless, band gap of graphene nanoribbons gnrs 6,7,8 is critical in addition to its other interesting electronic properties such as quasirelativistic behavior of charge carriers 9, the. Graphene, being a gapless semiconductor, cannot be used in pristine form for nanoelectronic applications. Tightbinding calculations, using a twodimensional model of the graphite lattice, lead to a point of contact of valence and conduction bands at the corner of the reduced brillouin zone. Origin of multiple band gap values in single width nanoribbons. Energy bandgap engineering of graphene nanoribbons. The model hamiltonian describes the hopping of the. Moreover, the band gap of the graphene nanoribbon gnr is dependent on its width and crystallographic orientation 615, rendering graphene based band structure engineering. Engineering the band gap of armchair graphene nanoribbons. The atomic structures, electronic band structures, density of states and electron localization functions of hbnc are examined as hbn concentration ranged from 0 to 100%. That is why narrow graphene nanoribbons gnrs with width less than 50 nm are considered to be essential components in future graphene electronics. Abstract we investigate electronic transport in lithographically patterned graphene ribbon structures. Sep 21, 2015 in terms of the materials electronic energy band structure, the band gap is the energy difference between the top of the valence band and the bottom of the conduction band. Energy gaps of both zigzag and armchair graphane nanoribbons were found to increase as the nanoribbons become narrower.

Energy bandgap engineering of graphene nanoribbons when lithographically generated graphene ribbons are laterally confined in charge it creates an energy gap near the charge neutrality point. Graphene nanoribbons gnrs, also called nano graphene ribbons or nanographite ribbons are strips of graphene with width less than 50 nm. These ribbons are found to have small fermi energy differences. To characterize these substitutions, functionalized atomic force microscopy afma tool to directly resolve chemical structuresis one of the most promising tools, yet the chemical analysis of heteroatoms has been. Widthdependent band gap in armchair graphene nanoribbons.

Han1, barbaros ozyilmaz2, yuanbo zhang2, and philip kim2 1department of applied physics, columbia university, new york, new york 10027. Han, barbaros ozyilmaz, yuanbo zhang, and philip kim. Introduction graphene nanoribbons gnrs with a tunable band gap, as a. In order to overcome this problem, graphene nanoribbons gnrs have been introduced, where. Bandgap engineering of bottomup synthesized graphene nano. Topological insulators are an emerging class of materials that host highly robust in gap surface or interface states. We find that the energy gap scales inversely with the ribbon width, thus demonstrating the ability to engineer the band gap of graphene. Among organic electronic materials, graphene nanoribbons gnrs offer extraordinary versatility as nextgeneration semiconducting materials for nanoelectronics and optoelectronics due to their tunable properties, including chargecarrier mobility, optical absorption, and electronic bandgap, which are uniquely defined by their chemical structures. Band gap engineering of silicene zigzag nanoribbons with. Band gap of strained graphene nanoribbons springerlink. Therefore, it is essential to generate a finite gap in the energy dispersion at dirac point.

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. We present an ab initio density functional theory dftbased study of hbn domain size effect on band gap of monolayer hbnc heterostructure modeled as b3n3xc61. The application of strain or electric eld, chemical edge functionalization and quantum con nement in graphene nanoribbons and nanomesh, and the introduction of defects have been used in e. Energy gap opening by crossing drop cast singlelayer graphene nanoribbons to cite this article. Wafer scale growth and characterization of edge specific. Nov 16, 2009 the electronic structures of graphane nanoribbons and hybrid graphane. Topological band engineering of graphene nanoribbons nature. Highlights this paper analyzes the stability and electronic properties of armchair graphene nanoribbons agnrs. Topological band engineering of graphene nanoribbons. 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. Building transistors from graphene nanoribbons engineering. Energy bandgap engineering of graphene nanoribbons request pdf. Graphene is widely regarded as a promising material for electronic applications because the exceptionally high mobilities of its charge carriers enable extremely fast transistors. The growth of graphene on sidewalls of sic0001 mesa structures using scalable photolithography was shown to produce high quality.

Silicon nitride gate dielectrics and band gap engineering in. Secondly, we doped hexagonal boron nitride hbn into graphene nanoribbons in the form of superlattice structure. Some general features of the structure of the 7r bands. Fieldeffect tunneling transistor based on vertical. A possible solution is to open a band gap in graphene for example, by using bilayer graphene 8, 9, nanoribbons 10, 11, quantum dots, or chemical derivatives but it has proven difficult to achieve high onoff ratios without degrading graphene s electronic quality. Introduction to the physical properties of graphene. Abstract graphene nanoribbons gnrs make up an extremely interesting class of materials. The fermi level, defined as the top of available electron energy levels, is located halfway between these two bands. Simulation of energy band gap opening of graphene nano. Graphene nanoribbons 18 display unique electronic properties based on truly twodimensional 2d graphene 9 with potential applications in nanoelectronics 10,11. Farajian, 2 keivan esfarjani, 3 and y oshiyuki kawazoe 1 1 institute for materials research, t ohoku. We investigate electronic transport in lithographically patterned graphene ribbon structures where the lateral confinement of charge carriers creates an energy. Thus, previous efforts to realize a field effect transistor for logic applications have assumed that introduction of a band gap in graphene is a prerequisite. 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.

On the one hand, the gap depends on the width of the graphene ribbons, while on the other hand it depends on the structure of the edges. Graphene is a oneatomiclayer thick twodimensional material made of carbon atoms arranged in a honeycomb structure. Pdf spin and bandgap engineering in doped graphene. Here we report a technique for modifying gnr band gaps via covalent selfassembly of a new species of molecular precursors. 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. Graphene nanoribbons gnrs are narrow strips of graphene.

These findings provide a basis for band gap engineering with different edge hydrogenations in agnrs and may find applications in the design of graphene based devices. The sizes of these energy gaps are investigated by measuring the conductance in the nonlinear response regime at low temperatures. Tuning the band gap of graphene nanoribbons synthesized. Study on the energy band regulation of the hbn doped.

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 lithog. The narrower the ribbons result in larger energy gap openings based on temperature dependent conductance. A perturbation calculation which starts, with wave functions of the twodimensional lattice and is applied to the threedimensional lattice is described. Several methods to open a band gap in graphene have been developed, including doping, hydrogenation, and fabrication of nanoribbons, nanomeshes and nanorings. In interpreting these numbers, one must, however, consider that several publica. 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 topologically engineered graphene nanoribbon superlattice is presented that hosts a onedimensional array of halffilled, in gap localized electronic states, enabling band engineering. Toyo kazu yamada et al 2018 nanotechnology 29 315705. Band structure calculations show an appreciable change in the band gap values in nanoribbons of the same width, however their ground state energy are practically the same. A numerical study of lineedge roughness scattering in.