DOCSLIB.ORG

Graphene Nanoribbon Fets: Technology Exploration for Performance and Reliability Mihir R

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Graphene Nanoribbon Fets: Technology Exploration for Performance and Reliability Mihir R IEEE TRANSACTIONS ON NANOTECHNOLOGY, VOL. 10, NO. 4, JULY 2011 727 Graphene Nanoribbon FETs: Technology Exploration for Performance and Reliability Mihir R. Choudhury, Student Member, IEEE, Youngki Yoon, Member, IEEE,JingGuo, Member, IEEE, and Kartik Mohanram, Member, IEEE Abstract—Graphene nanoribbon FETs (GNRFETs) are promis- Although 2-D graphene is a zero band-gap semi-metal, ing devices for beyond-CMOS nanoelectronics due to their a band-gap opens when a FET channel is fabricated on a excellent carrier-transport properties and potential for large- nanometer-wide graphene nanoribbon (GNR) [6]–[9]. In gen- scale processing and fabrication. This paper combines atomistic quantum-transport modeling with circuit simulation to perform eral, the band-gap of a GNR is inversely proportional to its width, technology exploration for GNRFET circuits. Results indicate that and width confinement down to the sub-10-nm scale is essen- GNRFETs offer significant gains over scaled CMOS at the 22-, 32-, tial to open a band-gap that is sufficient for room temperature and 45-nm nodes, with over 26–144× improvement in the energy- transistor operation. Unlike CNTs, which are mixtures of metal- delay product at comparable operating points. A quantitative study lic and semiconducting materials, recent samples of chemically of the effects of variations and defects on the performance and re- liability of GNRFET circuits is also presented. Simulation results derived sub-10-nm GNRs have exhibited all semiconducting indicate that whereas GNRFET circuits promise higher perfor- behavior [9], generating considerable excitement for transistor mance, lower energy consumption, and comparable reliability at applications. The two main types of GNRs, with the edges of the similar operating points to scaled CMOS circuits, they are more ribbons assumed passivated by hydrogen atoms, are armchair- susceptible to variations and defects. These results motivate signif- edge and zigzag-edge GNRs (AGNRs and ZGNRs). ZGNRs icant engineering, modeling, and simulation challenges facing the device and computer-aided design (CAD) communities involved in are predicted to be metallic by a simple tight-binding model, graphene electronics research. but a band-gap exists in more advanced, spin-unrestricted simu- lations [10]. For digital circuits applications, the focus has been Index Terms—Circuit design, defects, energy, energy-delay product, field-effect transistor, graphene, inverter, latch, nanorib- on using AGNRs as the channel material. AGNRs have an elec- bons, performance, quantum transport, reliability, ring oscillator, tronic structure that is closely related to that of zigzag CNTs. variability. The band-gap in AGNRs originates from quantum confinement, and edge effects play a critical role [10]. I. INTRODUCTION This paper first provides an overview of Schottky barrier (SB) RAPHENE, which is a monolayer of carbon atoms GNRFETs with intrinsic AGNR channels (GNRFETs hence- G packed into a 2-D honeycomb lattice, has emerged as a forth, unless specified otherwise). Unlike traditional MOSFETs, promising candidate material for beyond-CMOS nanoelectron- SBFETs use metal or metal silicide contacts at the source and ics. Graphene-based devices offer high mobility for ballistic drain ends, leading to the formation of SBs at these contacts. transport, high carrier velocity for fast switching, monolayer In SBFETs, the gate modulates the quantum tunneling current thin body for optimum electrostatic scaling, and excellent ther- through the SB [11]. Recently fabricated GNRFETs with chan- mal conductivity [1]–[6]. The potential to produce wafer-scale nel lengths of the order of 200 nm delivered about 21% of the graphene films with full planar processing for devices promises ballistic current at VD = 1 V, and about 4.5% of the ballistic high integration potential with conventional CMOS fabrication current at low VD < 0.1 V [12]. Clearly, these are prelimi- processes, which is a significant advantage over carbon nan- nary devices, and it would be natural to expect further advances otubes (CNTs) [6]. such as the integration of ultrathin high-κ dielectrics [13] and aggressive channel length scaling to move the performance of these devices closer to the ballistic limit, with switching speeds, Manuscript received October 18, 2009; revised June 2, 2010; accepted July ION/IOFF, and sub-threshold slope that is competitive with 19, 2010. Date of publication September 9, 2010; date of current version July scaled CMOS. 8, 2011. This work was supported in part by the National Science Foundation under Grant CCF-0916636 and Grant CCF-0916683, and in part by the Office Although most discussions in this paper focus on SB-type of Naval Research. The review of this paper was arranged by Associate Editor GNRFETs [14], [15], simulation studies of MOSFET-type R. Lake. GNRFETs with doped reservoirs have also been reported in M. R. Choudhury and K. Mohanram are with the Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005 USA (e-mail: [16]–[18]. In [19] and [20], SB-type GNRFETs were also com- [email protected]; [email protected]). pared to MOSFET-type GNRFETs. There is consensus that Y. Yoon was with the Department of Electrical and Computer Engineering, in ideal devices, MOSFET-type GNRFETs show better de- University of Florida, Gainesville, FL 32611 USA. He is now with the University of California, Berkeley, CA 94720 USA (e-mail: ykyoon@ufl.edu). vice characteristics over SB-type GNRFETs: larger maximum J. Guo is with the Department of Electrical and Computer Engineering, achievable ION/IOFF, larger ION, larger transconductance, and University of Florida, Gainesville, FL 32611 USA (e-mail: guoj@ufl.edu). better saturation behavior. Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Further, this paper presents extensive results on technology Digital Object Identifier 10.1109/TNANO.2010.2073718 exploration for GNRFET circuits. It couples atomistic quantum- 1536-125X/$26.00 © 2010 IEEE 728 IEEE TRANSACTIONS ON NANOTECHNOLOGY, VOL. 10, NO. 4, JULY 2011 transport modeling in intrinsic GNRFETs with a circuit simulator that includes parasitics and nonidealities that are nec- essary to capture extrinsic effects in fabricated GNRFETs. At the device level, GNRFETs are simulated by self-consistently solving an atomistic quantum transport equation based on the nonequilibrium Green’s function (NEGF) formalism with the 3-D Poisson’s equation. These rigorous simulations provide I– V and Q–V data for intrinsic GNRFETs, which are integrated Fig. 1. NEGF formalism for a generic transistor. into a circuit-level simulation framework based on lookup tables for technology exploration of GNRFET circuits. The simulator This paper is an extended version of [21] and is organized is used to study the delay, power, energy, and noise margins of as follows. Section II provides a background in quantum simu- representative GNRFET circuits including inverters, ring oscil- lation of intrinsic GNRFETs. Section III describes technology lators, and latches. Results indicate that GNRFETs offer signif- exploration for GNRFET circuits based on a large-signal circuit icant gains over scaled CMOS at the 22-, 32-, and 45-nm nodes, model for extrinsic GNRFETs. Sections IV and V discuss how with over 26–144× improvement in the energy-delay product variations and defects impact the performance and reliability of (EDP) at comparable operating points. GNRFET circuits. Section VI is a conclusion. Significant technical challenges, however, remain to be met. Due to the atomically thin and nanometer-wide geometries of II. SIMULATION OF INTRINSIC GNRFETS GNRs, variability and defects are projected to have a larger impact on circuit performance and reliability in comparison As devices scale with technology, a powerful quantum trans- to conventional silicon devices. The framework is extended to port simulation framework based on the NEGF formalism pro- perform a quantitative study of the effects of variations and vides an ideal approach for bottom-up device modeling and defects in intrinsic GNRFETs on the performance and reliabil- simulation [22] for the following reasons: 1) atomistic descrip- ity of GNRFET circuits. Independent variations in GNR width, tions of devices can be readily implemented; 2) open boundaries which is the most common source of variation, and independent can be rigorously treated; and 3) multiphenomena (e.g., inelastic charge impurities in the gate oxide, which is the most com- scattering and light emission) can be modeled. mon source of defects, are considered in this paper. Variation Fig. 1 summarizes the procedure to apply the NEGF approach in GNR width affects GNRFET ION/IOFF nonlinearly, which to a generic transistor. The transistor channel, which can be a in turn impacts circuit performance, power, and noise margins. piece of silicon, a GNR, a nanowire, or a single molecule, is Simulation results indicate that variation in GNR width can in- connected to the source and drain contacts. The gate modulates crease the delay, static power, and dynamic power of inverters the conductance of the channel. One first identifies a suitable by 6%–77%, 313%–643%, and 37%–215%, respectively, while basis set and derives the Hamiltonian matrix H for the isolated reducing the noise margin by 27%–80%. Charge impurities af- channel. Then, the self-energy matrices Σ1 , Σ2 , and ΣS , which fect intrinsic GNRFET characteristics nonlinearly and in an describe how the channel couples
Load more

Recommended publications
  • Simulations of Graphene Nanoribbon Field Effect Transistor for The
    nanomaterials Article Simulations of Graphene Nanoribbon Field Effect Transistor for the Detection of Propane and Butane Gases: A First Principles Study Muhammad Haroon Rashid * , Ants Koel and Toomas Rang Thomas Johan Seebeck Department of Electronics, Tallinn University of Technology, Ehitajate tee 5, 12616 Tallinn, Estonia; [email protected] (A.K.); [email protected] (T.R.) * Correspondence: [email protected]; Tel.: +372-5391-2599 Received: 7 December 2019; Accepted: 30 December 2019; Published: 3 January 2020 Abstract: During the last few years graphene has emerged as a potential candidate for electronics and optoelectronics applications due to its several salient features. Graphene is a smart material that responds to any physical change in its surrounding environment. Graphene has a very low intrinsic electronic noise and it can detect even a single gas molecule in its proximity. This property of graphene makes is a suitable and promising candidate to detect a large variety of organic/inorganic chemicals and gases. Typical solid state gas sensors usually requires high operating temperature and they cannot detect very low concentrations of gases efficiently due to intrinsic noise caused by thermal motion of charge carriers at high temperatures. They also have low resolution and stability issues of their constituent materials (such as electrolytes, electrodes, and sensing material itself) in harsh environments. It accelerates the need of development of robust, highly sensitive and efficient gas sensor with low operating temperature. Graphene and its derivatives could be a prospective replacement of these solid-state sensors due to their better electronic attributes for moderate temperature applications. The presence of extremely low intrinsic noise in graphene makes it highly suitable to detect a very low concentration of organic/inorganic compounds (even a single molecule ca be detected with graphene).
    [Show full text]
  • Transport of Fullerene Molecules Along Graphene Nanoribbons SUBJECT AREAS: Alexander V
    Transport of fullerene molecules along graphene nanoribbons SUBJECT AREAS: Alexander V. Savin1,2 & Yuri S. Kivshar2 SURFACES, INTERFACES AND THIN FILMS MECHANICAL AND STRUCTURAL 1Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow 119991, Russia, 2Nonlinear Physics Center, PROPERTIES AND DEVICES Research School of Physics and Engineering, Australian National University, Canberra ACT 0200, Australia. MOLECULAR MACHINES AND MOTORS We study the motion of C60 fullerene molecules and short-length carbon nanotubes on graphene CARBON NANOTUBES AND nanoribbons. We reveal that the character of the motion of C60 depends on temperature: for T , 150 K the FULLERENES main type of motion is sliding along the surface, but for higher temperatures the sliding is replaced by rocking and rolling. Modeling of the buckyball with an included metal ion demonstrates that this molecular complex undergoes a rolling motion along the nanoribbon with the constant velocity under the action of a Received constant electric field. The similar effect is observed in the presence of the heat gradient applied to the 27 June 2012 nanoribbon, but mobility of carbon structures in this case depends largely on their size and symmetry, such that larger and more asymmetric structures demonstrate much lower mobility. Our results suggest that both Accepted electorphoresis and thermophoresis can be employed to control the motion of carbon molecules and 29 October 2012 fullerenes. Published 20 December 2012 ver the past 20 years nanotechnology has made an impressive impact on the development of many fields of physics, chemistry, medicine, and nanoscale engineering1. After the discovery of graphene as a novel material for nanotechnology2, many properties of this two-dimensional object have been studied both O 3,4 Correspondence and theoretically and experimentally .
    [Show full text]
  • Probing DNA Translocations with Inplane Current Signals in a Graphene Nanoribbon with a Nanopore Stephanie J
    This is an open access article published under a Creative Commons Non-Commercial No Derivative Works (CC-BY-NC-ND) Attribution License, which permits copying and redistribution of the article, and creation of adaptations, all for non-commercial purposes. Article Cite This: ACS Nano 2018, 12, 2623−2633 www.acsnano.org Probing DNA Translocations with Inplane Current Signals in a Graphene Nanoribbon with a Nanopore Stephanie J. Heerema, Leonardo Vicarelli, Sergii Pud, Raymond N. Schouten, Henny W. Zandbergen, and Cees Dekker* Kavli Institute of Nanoscience Delft, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands *S Supporting Information ABSTRACT: Many theoretical studies predict that DNA sequencing should be feasible by monitoring the transverse current through a graphene nanoribbon while a DNA molecule translocates through a nanopore in that ribbon. Such a readout would benefit from the special transport properties of graphene, provide ultimate spatial resolution because of the single-atom layer thickness of graphene, and facilitate high-bandwidth measurements. Previous experimental attempts to measure such transverse inplane signals were however dominated by a trivial capacitive response. Here, we explore the feasibility of the approach using a custom-made differential current amplifier that discriminates between the capacitive current signal and the resistive response in the graphene. We fabricate well-defined short and narrow (30 nm × 30 nm) nanoribbons with a 5 nm nanopore in graphene with a high-temperature scanning transmission electron microscope to retain the crystallinity and sensitivity of the graphene. We show that, indeed, resistive modulations can be observed in the graphene current due to DNA translocation through the nanopore, thus demonstrating that DNA sensing with inplane currents in graphene nanostructures is possible.
    [Show full text]
  • Delft University of Technology Graphene Nanodevices for DNA
    Delft University of Technology Graphene nanodevices for DNA sequencing Heerema, SJ; Dekker, C DOI 10.1038/NNANO.2015.307 Publication date 2016 Document Version Accepted author manuscript Published in Nature Nanotechnology Citation (APA) Heerema, SJ., & Dekker, C. (2016). Graphene nanodevices for DNA sequencing. Nature Nanotechnology, 11(2), 127-136. https://doi.org/10.1038/NNANO.2015.307 Important note To cite this publication, please use the final published version (if applicable). Please check the document version above. Copyright Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons. Takedown policy Please contact us and provide details if you believe this document breaches copyrights. We will remove access to the work immediately and investigate your claim. This work is downloaded from Delft University of Technology. For technical reasons the number of authors shown on this cover page is limited to a maximum of 10. Graphene nanodevices for DNA sequencing Stephanie J. Heerema and Cees Dekker∗ Kavli Institute of Nanoscience Delft, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands. ∗ To whom correspondence should be addressed; email: [email protected] Abstract Fast, cheap, and reliable DNA sequencing could be one of the most disruptive innovations of this decade as it will pave the way for personalised medicine. In pursuit of such technology, a variety of nanotechnology-based approaches have been explored and established including sequencing with nanopores.
    [Show full text]
  • Topological Carbon Materials: a New Perspective
    Topological carbon materials: a new perspective Yuanping Chen1, Yuee Xie1, Xiaohong Yan1, Marvin L. Cohen2, Shengbai Zhang3 1 Faculty of Science, Jiangsu University, Zhenjiang, 212013, Jiangsu, China 2Department of Physics, University of California at Berkeley, and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, 94720, USA. 3Department of Physics, Applied Physics, and Astronomy Rensselaer Polytechnic Institute, Troy, New York, 12180, USA. Outline: I. Introduction ........................................................................................................................................ 1 II. Carbon structures: from one to three dimensionalities...................................................................... 2 2.1 One dimension: polyacetylene ......................................................................................... 2 2.2 Two dimension: graphene, graphyne and Kagome graphene .......................................... 3 2.3 Three dimension: graphene networks and carbon foams ................................................. 6 III. Topological phases in general ……………………………………...…………………………...9 3.1 Nodal points:Weyl point, Triple point, Dirac point……………………………….…10 3.2 Nodal lines: Nodal ring, Nodal chain/link, Hopf link/chain………………..………..12 3.3 Nodal surfaces: planer surface, sphere surface…………………..…………………..13 IV. Topological properties of carbon .................................................................................................... 14 4.1 Orbital physics
    [Show full text]
  • Large-Scale Solution Synthesis of Narrow Graphene Nanoribbons
    ARTICLE Received 13 Aug 2013 | Accepted 2 Jan 2014 | Published 10 Feb 2014 DOI: 10.1038/ncomms4189 Large-scale solution synthesis of narrow graphene nanoribbons Timothy H. Vo1, Mikhail Shekhirev1, Donna A. Kunkel2, Martha D. Morton1, Eric Berglund1, Lingmei Kong2, Peter M. Wilson1, Peter A. Dowben2,3, Axel Enders2,3 & Alexander Sinitskii1,3 According to theoretical studies, narrow graphene nanoribbons with atomically precise armchair edges and widths of o2 nm have a bandgap comparable to that in silicon (1.1 eV), which makes them potentially promising for logic applications. Different top–down fabrication approaches typically yield ribbons with width 410 nm and have limited control over their edge structure. Here we demonstrate a novel bottom–up approach that yields gram quantities of high-aspect-ratio graphene nanoribbons, which are only B1 nm wide and have atomically smooth armchair edges. These ribbons are shown to have a large electronic bandgap of B1.3 eV, which is significantly higher than any value reported so far in experimental studies of graphene nanoribbons prepared by top–down approaches. These synthetic ribbons could have lengths of 4100 nm and self-assemble in highly ordered few-micrometer-long ‘nanobelts’ that can be visualized by conventional microscopy techniques, and potentially used for the fabrication of electronic devices. 1 Department of Chemistry, University of Nebraska–Lincoln, Lincoln, Nebraska 68588, USA. 2 Department of Physics, University of Nebraska–Lincoln, Lincoln, Nebraska 68588, USA. 3 Nebraska Center for Materials and Nanoscience, University of Nebraska–Lincoln, Lincoln, Nebraska 68588, USA. Correspondence and requests for materials should be addressed to A.S.
    [Show full text]
  • Highly Aligned Polymeric Nanowire Etch-Mask Lithography Enabling the Integration of Graphene Nanoribbon Transistors
    nanomaterials Article Highly Aligned Polymeric Nanowire Etch-Mask Lithography Enabling the Integration of Graphene Nanoribbon Transistors Sangheon Jeon 1,†, Pyunghwa Han 2,†, Jeonghwa Jeong 1, Wan Sik Hwang 3,4,* and Suck Won Hong 1,* 1 Department of Cogno-Mechatronics Engineering, Department of Optics and Mechatronics Engineering, College of Nanoscience and Nanotechnology, Pusan National University, Busan 46241, Korea; [email protected] (S.J.); [email protected] (J.J.) 2 Research Center for S-T/F, Samsung Electro-Mechanics, Busan 46754, Korea; [email protected] 3 Department of Materials Engineering, Korea Aerospace University, Goyang 10540, Korea 4 Smart Drone Convergence, Korea Aerospace University, Goyang 10540, Korea * Correspondence: [email protected] (W.S.H.); [email protected] (S.W.H.) † These authors contributed equally to this work. Abstract: Graphene nanoribbons are a greatly intriguing form of nanomaterials owing to their unique properties that overcome the limitations associated with a zero bandgap of two-dimensional graphene at room temperature. Thus, the fabrication of graphene nanoribbons has garnered much attention for building high-performance field-effect transistors. Consequently, various methodolo- gies reported previously have brought significant progress in the development of highly ordered graphene nanoribbons. Nonetheless, easy control in spatial arrangement and alignment of graphene nanoribbons on a large scale is still limited. In this study, we explored a facile, yet effective method for the fabrication of graphene nanoribbons by employing orientationally controlled electrospun poly- meric nanowire etch-mask. We started with a thermal chemical vapor deposition process to prepare graphene monolayer, which was conveniently transferred onto a receiving substrate for electrospun polymer nanowires.
    [Show full text]
  • Graphene Nanoribbons with Zigzag and Armchair Edges Prepared by Scanning Tunneling Microscope Lithography on Gold Substrates
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Repository of the Academy's Library Graphene nanoribbons with zigzag and armchair edges prepared by scanning tunneling microscope lithography on gold substrates P. Nemes – Incze1,2,*, Levente Tapasztó1,2 , G. Zs. Magda1,2 , Z. Osváth1,2, G. Dobrik1,2 , X. Jin2,3, C. Hwang2,3, L.P. Biró1,2 1 Institute of Technical Physics and Materials Science, Centre for Natural Sciences, 1525 Budapest, PO Box 49, Hungary 2 Korean-Hungarian Joint Laboratory for Nanosciences (KHJLN), P.O. Box 49, 1525 Budapest, Hungary 3 Center for Nano-metrology Division of Industrial Metrology Korea Research Institute of Standards and Science, Yuseong, Daejeon 305-340, South Korea Abstract The properties of graphene nanoribbons are dependent on both the nanoribbon width and the crystallographic orientation of the edges. Scanning tunneling microscope lithography is a method which is able to create graphene nanoribbons with well defined edge orientation, having a width of a few nanometers. However, it has only been demonstrated on the top layer of graphite. In order to allow practical applications of this powerful lithography technique, it needs to be implemented on single layer graphene. We demonstrate the preparation of graphene nanoribbons with well defined crystallographic orientation on top of gold substrates. Our transfer and lithography approach brings one step closer the preparation of well defined graphene nanoribbons on arbitrary substrates for nanoelectronic applications. 1. Introduction Graphene has been in the forefront of nanoscience research ever since the experimental observation that the charge carriers in this material are relativistic Dirac quasiparticles [1–3].
    [Show full text]
  • An Electrodeposited Au Nanoparticle/Porous Graphene Nanoribbon Composite for Electrochemical Detection of Alpha-Fetoprotein
    ©2020. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http:// creativecommons.org/licenses/by-nc-nd/4.0/ Journal Pre-proof An electrodeposited Au nanoparticle/porous graphene nanoribbon composite for electrochemical detection of alpha-fetoprotein Lavanya Jothi, Saravana Kumar Jaganathan, Gomathi Nageswaran PII: S0254-0584(19)31324-0 DOI: https://doi.org/10.1016/j.matchemphys.2019.122514 Reference: MAC 122514 To appear in: Materials Chemistry and Physics Received Date: 9 July 2019 Revised Date: 28 November 2019 Accepted Date: 30 November 2019 Please cite this article as: L. Jothi, S.K. Jaganathan, G. Nageswaran, An electrodeposited Au nanoparticle/porous graphene nanoribbon composite for electrochemical detection of alpha-fetoprotein, Materials Chemistry and Physics (2020), doi: https://doi.org/10.1016/j.matchemphys.2019.122514. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier B.V. An electrodeposited Au nanoparticle/porous graphene nanoribbon composite for electrochemical
    [Show full text]
  • Flexible Phototransistors Based on Graphene Nanoribbon Decorated
    Sensors and Actuators A 232 (2015) 285–291 Contents lists available at ScienceDirect Sensors and Actuators A: Physical journal homepage: www.elsevier.com/locate/sna Flexible phototransistors based on graphene nanoribbon decorated with MoS2 nanoparticles Mohsen Asad a,∗, Sedigheh Salimian b, Mohammad Hossein Sheikhi a, Mahdi Pourfath c,d a School of Electrical and Computer Engineering, Shiraz University, Shiraz 71345-1585, Iran b Faculty of Physics, Kharazmi University, Tehran 15719-14911, Iran c School of Electrical and Computer Engineering, University of Tehran, Tehran 14395-515, Iran d Institute for Microelectronics, TU Wien, Gußhausstraße 27–29/E360, A-1040 Wien, Austria article info abstract Article history: This paper presents highly efficient, flexible, and low-cost photo-transistors based on graphene nanorib- Received 28 February 2015 bon (GNR) decorated with MoS2 nanoparticles (NPs). Due to high carrier mobility, GNR has been used Received in revised form 16 June 2015 as carrier transport channel and MoS2 NPs provide strong advantage of high gain absorption and the Accepted 17 June 2015 generation of electron-hole pairs. These pairs get separated at the interface between GNR and MoS Available online 22 June 2015 2 NPs, which leads to electron transfer from NPs towards GNR. The fabricated devices based on GNR-MoS2 −1 hybrid material show a high photo-responsivity of 66 A W and fast rise-time (tr) and decay-time (td) Keywords: of 5 ms and 30 ms, respectively, under blue laser illumination with a wavelength of 385 nm and power Graphene nanoribbon density of 2.1 ␮W. The achieved photo-responsivity is 1.3×105 and 104 times larger than that of the first MoS2 nanoparticles Photo-transistor reported pristine graphene and MoS2 photo-transistors, respectively.
    [Show full text]
  • Engineering the Electronic Structure of Atomically-Precise Graphene Nanoribbons
    Engineering the electronic structure of atomically-precise graphene nanoribbons by Giang Duc Nguyen A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Physics in the GRADUATE DIVISION of the UNIVERSITY OF CALIFORNIA, BERKELEY Committee in charge: Professor Michael F. Crommie, Chair Professor Feng Wang Professor Junqiao Wu Summer 2016 Engineering the electronic structure of atomically-precise graphene nanoribbons Copyright 2016 by Giang Duc Nguyen 1 Abstract Engineering the electronic structure of atomically-precise graphene nanoribbons by Giang Duc Nguyen Doctor of Philosophy in Physics University of California, Berkeley Professor Michael F. Crommie, Chair Graphene nanoribbons (GNRs) have recently attracted great interest because of their novel electronic and magnetic properties, as well as their significant potential for device applications. Although several top-down techniques exist for fabricating GNRs, only bottom-up synthesis of GNRs from molecular precursors yields nanoribbons with atomic-scale structural control. Furthermore, precise incorporation of dopant species into GNRs, which is possible with bottom-up synthesis, is a potentially powerful way to control the electronic structure of GNRs. However, it is not well understood how these dopants affect the electronic structure of GNRs. Are these effects dependent on the dopant site? Can the band gap be tuned by doping? This dissertation helps to answer these questions through studying the electronic structure of bottom-up grown GNRs with controlled atomic dopants. The effects of edge and interior doping with different atomic species such as sulfur, boron and ketone were investigated and showed significant site dependence. Topographic and local electronic structure characterization was performed via scanning tunneling microscopy & spectroscopy (STM & STS) and compared to first- principle calculations.
    [Show full text]
  • Nano-Engineering of Graphene and Related Materials
    1 Nano-Engineering of Graphene and Related Materials Zhiping Xu Tsinghua University China 1. Introduction Graphene is the ultimately monolayer material with single-atom thickness. It possesses many fascinating properties including massless Dirac electronic structure, anomalous quantum Hall effects, high mobility, extraordinary high thermal conductivity, stiffness and strength (see other chapters in this book). Impressively, these properties have remarkable dependence on its morphology and atomic structure, e.g. its size and shape (Fig. 1, Xu & Buehler, 2010a). Moreover, interior and exterior doping effects from defects, molecular adsorptions or electromagnetic fields are also significant. For example, hydrogenation, oxidation and electrical field significantly tune its structural, mechanical, thermal, electronic and optical structures, which is controllable and even reversible. These sensitive responses of a graphene sheet to structural and environmental cues enable us opportunities to engineer its physical and chemical properties at nanoscale. Fig. 1. A phases diagram for graphene sheets as a function of their geometric parameters: (a) a graphene sheet with length L and width W; (b) a two-dimensional membrane with ripples from thermal fluctuation as L ~ W; (c) a fluctuating one-dimensional ribbon while it has apparent aspect ratio n = L/W; (d) a nanoscroll after a ribbon self-folds due to the van der Waals interactions between adjacent graphene sheet. (Xu & Buehler, 2010a) www.intechopen.com 4 Physics and Applications of Graphene - Experiments 2. Nano-engineering by tailoring nanostructures Fig. 2. Two-dimensional monolayer crystallites of NbSe2 (a), graphite (b), Bi2Sr2CaCu2Ox (c) and MoS2 (d) as prepared by the mechanical exfoliation technique and visualized by atom force microscopy (AFM) (a and b), scanning electron microscopy (c) and optical microscope (d).
    [Show full text]