1、GrapheneFurther Applications and ResearchTeam #3Phillip KellerKrista MelishMicheal JonesJames Kancewick/images/Art_Gallery/AS-graphene.jpgOverviewIntroductionGraphenes mechanical propertiesGraphenes electrical propertiesCarbon Vs SiliconSupercapacitors and Graphene Gas Detection using low-temperatur

2、e reduced graphene oxide sheetsUltrafast graphene photodetectorElectronics and Magnetism of Patterned Graphene NanoroadsGeneral ConclusionsIntroductionAdvances in electronics have been the result of the continuous miniaturization or scaling of electronic devices, particularly of silicon-based transi

3、stors, that has led to denser, faster and more power-efficient circuitry./_images/elect/circuit.gifCharlier, J.-C., Blase, X., & Roche, S. Electronic and transport properties of nanotubes. Rev. Mod. Phys.The realization of the approaching limits has inspired a worldwide effort to develop alternative

4、 device technologies. Some approaches involve spin-based devices, while others replace a key component of the device, the conducting channel, with carbon nanomaterials, which have superior electrical properties.IntroductionAmong these carbon nanomaterials is graphene. Graphene is a two dimensional a

5、llotrope of carbon arranged like a honeycomb structure made out of hexagons and plays an important role since it is the basis for the understanding of the electronic properties in other allotropes./Science-Articles/Archive/sabl/2007/Nov/assets/img/lrg/graphene_sheet.jpgHistory of GrapheneWallace in

6、1947Created 2D structure to help in the understanding of 3D GraphiteSingle layers of graphite grown epitaxially on metallic substrates in the 1970sTightly bound to substrate, distorted propertiesTerm “graphene” coined in 19872004, Geim and Novoselov mechanically exfoliated sheets of graphene from gr

7、aphiteTransferred to charge neutral silicon substrate First successful electrical properties measuredGeim, A. K. & MacDonald, A. H. (2007). Graphene: Exploring carbon flatland. Physics Today.A Closer Look at Graphene2D hexagonal carbon crystal latticeInfinite boundariesActual 2D structure is debatab

8、leGraphene sandwichThermal effectsNaturally occurringMultilayer in graphiteNanospecs in soot from exhaustCurrently one of the most researched materialsUnique physical and electrical propertiesWide array of potential uses/images/Art_Gallery/ASgraphene.jpgZiegler, K., Robust transport properties in gr

9、aphene. Phys. Rev. Lett.Graphene Mechanical PropertiesBreaking strength 200 times greater than steelYoungs modulus of 1 tPaIncredible rigidity lends themselves to nanoscale pressure sensorsNanoscopic graphene flakes bend with increasing pressure which alters their electrical conductivity which can b

10、e related to the pressureJohn Scott Bunch. Mechanical and Electrical Properties of Graphene. Cornell University 2008./images/CableSpan.JPGThermal properties exceed those of diamondExcellent conductor of heatPhonon dominated although it can be shown that at certain conditions the electrical portion i

11、s significantGraphene Electrical PropertiesAnomalous Quantum Hall EffectQuantization of the Hall effectDirac fermionsCarriers have zero effective massRoom temperature electron mobility of 15,000 cm2/V*sTheoretically higher conductivity at room temp than silver, but unknown forces are limitingPossibl

12、e optical phonon scattering from attached substrateCharlier, J.-C., Blase, X., & Roche, S. Electronic and transport properties of nanotubes. Rev. Mod. Phys./lighting_pictures/lightningbolt_closeup.jpgBoth P and N-type transistors have been createdRecent announcement by IBM that graphene transistor w

13、as operated at a terahertz frequencyTunable band gap from 0 to 0.25 eVExcellent conductivity makes graphene ideal for electrical leads in sensors/capacitors or use in touch screens because of its mechanical strengthGraphene ribbons have tunable electrical conductivity depending on the shapeElectrica

14、l Component: TransistorA transistors operation speed depends on the size of the device smaller devices can run faster and the speed at which electrons travel in it. This size dependence has been one of the major driving forces for making ever smaller silicon transistors.The Consortium of Internation

15、al Semiconductor Companies in its 2001 International Technology Roadmap for Semiconductors projected that transistors have to be smaller than 9 nanometers by 2016 in order to continue the performance trend.Charlier, J.-C., Blase, X., & Roche, S. Electronic and transport properties of nanotubes. Rev.

16、 Mod. Phys.Carbon vs. SiliconFigure (a) is Intels 45 nm silicon transistor which uses a Hafniun based dielectric. Figure (b) is a wafer of the 45 nm transistors photographed with a dime. The processors incorporate 410 million transistors for each dual core chip, and 820 million for each quad core ch

17、ip./pressroom/kits/45nm/photos.htm.Carbon vs. SiliconGraphene could offer a way forward. As well as being extremely thin and a semiconductor, electrons move through graphene at extremely high speeds./textures/Manmade/images/Plastics%20and%20Related/electronic_circuit_board_9131073.JPGGeim, A. K. & N

18、ovoselov, K. S. The rise of graphene. Nature Mater.The cutting edge of silicon-based transistors is at 32 nanometers.Graphene has the potential to fabricate transistors only a few atoms across. British researchers have unveiled the worlds smallest transistor, which measures one atom thick and ten at

19、oms across. This is in the sub-10 nanometer rangePerformance Characteristics for Carbon-Based TransistorAmbipolar transfer characteristics current versus gate voltage: drain bias increases from 0.1 V to 1.1 V in 0.2 V steps. Red line represents -0.1 V and the pink line is -1.1 V. Step size is -0.2 V

20、Left Inset: Schematic of the band structure of a Schottky barrier semiconducting carbon nanotube in a field effect transistor under negative gate bias. Holes areinjected from the source S.Right Inset: Schematic of the band structure of a Schottky barrier semiconducting carbon nanotube in a field eff

21、ect transistor under positive gate bias. Electrons areinjected from the drain D.Anantram, M. P. & Leonard, F. Physics of carbon nanotube electronic devices. Rep. Prog. Phys.Electrical Component: SupercapacitorsSupercapacitors are energy storage systems that are able to store and deliver energy at re

22、latively high rates. They are able to store and deliver energy beyond those accessible by batteries. This is because the mechanism of energy storage is the simple charge-separation at the electrochemical interface between the electrode and the electrolyte.Chen, Y. et al. Supercapacitor Devices Based

23、 on Graphene Materials. J. Phys. Chem. C 2009/WOW/willWebPics/battery/superCap.jpg/2008/12/energizer-bunny.jpgSupercapacitorsAn advantage for supercapacitors is that they have several orders of magnitude higher energy density than that of conventional dielectric capacitors.Furthermore, the deficienc

24、ies of other power sources, such as batteries and fuel cells, could be complemented by supercapacitors, owning to their long cycle life and rapid charging and discharging at high power densities.Chen, Y. et al. Supercapacitor Devices Based on Graphene Materials. J. Phys. Chem. C 2009+/WOW/willWebPic

25、s/battery/superCap.jpg/2008/12/energizer-bunny.jpgSupercapacitorsWhen the practical use of electrochemical capacitors for the storage of electrical charge was demonstrated and patented by General Electric, supercapacitors have generated great interest for a wide and growing range of applications suc

26、h as:Kotz, R.; Carlen, M. Electrochim. Acta 2000, 45, 2483.http:/i.thisislondon.co.uk/i/pix/2008/07/general-electric-415x275.jpgLinks to pictures are in notesLoad cranesForkliftsElectric vehiclesElectric utilitiesFactory power back upSupercapacitorsDifferent materials such as various carbon material

27、s, mixed metal oxides, and conducting polymers have been used as supercapacitor electrode materials./chemistry/elements/images/carbon.jpgPandolfo, A. G.; Hollenkamp, A. F. J. Power Sources 2006, 157, 11.Particularly carbon, in its various forms, has been used as electrode materials of supercapacitor

28、s, aiming at high specific capacitance together with high power density.SupercapacitorsAlthough porous carbon materials have high specific surface area, the low conductivity of porous carbon materials is limiting its application in high power density supercapacitors.Carbon nanotubes (CNTs), with exc

29、ellent electrical conductivity and high surface areas, have been fabricated for supercapacitors since 1997.Diederich, L.; Barborini, E.; Piseri, P.; Podesta, A.; Milani, P. Appl. Phys. Lett. 1999, 75, 2662./opasstore/media/catalog.jpg/home/afv/nanotube.singleframe.begin.gifSupercapacitorsHowever, CN

30、T-based supercapacitors have not met the expected performance; one possible reason is probably due to the observed contact resistance between the electrode and current collector.Hence, many studies have focused on the morphology of the carbon materials to boost the performance of the capacitor, such

31、 as growing CNTs directly on bulk metals to eliminate the contact resistance./DPs/Technology/CircuitBoard_2.jpg/fs24/f/2008/018/e/3/Smoke_Stock_002_by_mross5013.jpgShaijumon, M. M.; Ou, F. S.; Ci, L. J.; Ajayan, P. M. Chem. Commun. 2008, 2373.SupercapacitorsGraphene is emerging as a unique morpholog

32、y carbon material with potential for electrochemical energy storage device applications due to its superb characteristics of chemical stability, high electrical conductivity, and large surface area.Fig (a). Schematic diagram of graphene-based supercapacitor device Chen, Y. et al. Supercapacitor Devi

33、ces Based on Graphene Materials. J. Phys. Chem. C 2009Recently, it has been proposed that graphene should be a competitive material for supercapacitor application. Graphene with less agglomeration should be expected to exhibit higher effective surface area and thus better supercapacitor performance.

34、Gas Detection using low-temperature reduced graphene oxide sheetsBy Ganhua lu Leonidas E. Ocola Junhong ChenGas Detection using reduced graphene sheetshigh-performance gas sensors made of partially reduced graphene oxide sheets obtained through low-temperature step annealing at 300 C in argon flow a

35、t atmospheric pressureWas tested with low concentration NO2 W. Frank, J. Vac. Sci. Technol. B 25, 2558 2007/media/images/large/large_1112_D12_Image.JPGBackgroundThe 2D structure of graphene makes every carbon atom a surface atom so that electron transport can be highly sensitive to adsorbed molecule

36、s.Mechanically exfoliated graphene has demonstrated a potential ability to detect gases down to the single molecular levelThe gas sensing mechanism of graphene is generally attributed to the adsorption/desorption of gaseous molecules which act as donors or acceptors on the graphene surface, leading

37、to changes in the conductance of grapheneS. Novoselov, Y. Zhang, I. V. Grigorieva, and A. A. Firsov, Science 306, 666 2004./graphene-interconnects.jpgChemically Reduced Graphene Oxide using HydrazineHas been used for the detection of acetone, warfare agents, and explosive agents at parts per billion

38、 concentrationsUsing Hydrazine for sensor fabrication involves toxic chemicals and introduce extra nitrogen functional groups which may slow the response of the sensor. Yang, A. Velamakanni, G. Bozoklu, S. Park, M. Stoller, R. D. Piner, S. Stankovich, I. Jung, D. A. Field, C. A. Ventrice, Jr., and R

39、. S. Ruoff, Carbon 47, 145 2009.http:/2./_VyTCyizqrHs/SRoCXZgYZxI/AAAAAAAABoU/64fpjTGIJjw/s1600-h/graphene_sheet.jpgBelow is graphene prepared with HydrazineModified Hummers Method Was used for the creation of the graphene oxide sheets used for sensorsGraphite is first synthesized by oxidative treat

40、mentThen is exfoliated in water to produce suspension of single graphene oxide sheetsFor a detailed explanation of Hummers method please visit /doi/abs/10.1021/ja01539a017 Park, J. An, R. D. Piner, I. Jung, D. Yang, and R. S. Ruoff, Chem. Mater. 20, 6592 2008./Hummer.gifChemistryhttp:/www.physics.um

41、anitoba.ca/tapash/nano/molecule-graphene.jpgFabrication of the Sensing DeviceThe graphene oxide was suspended with Au interdigitated electrodes.Both finger width and interfinger spacing of 1 mDrops of the graphene oxide suspension where then placed on the wafer. H. Lu, L. E. Ocola, and J. H. Chen, J

42、. Nanomater. 2006, 60828 2006/yodhlab/images/research_CMP_Solubilization.jpgThe Fabrication of the ElectrodesThe Au interdigitated electrodes were fabricated using electron-beam lithography on a Silicon wafer. /nanofab/nanofab_equipment/images/leica.jpgThe SensorFIG. 1. Color online SEM image of a G

43、O sheet bridging two neighboring Au fingers of an interdigitated electrode. Gases are detected by measuring the change in the current while applying a constant dc bias to the device.Leonidas E. Ocola, et al, Gas detection using low-temperature reduced graphene oxide sheets 2009 American Institute of

44、 Physics, 2009Figure obtained from articleHow it worksWhen different gases absorb to it the electrical conductance of the Graphene Oxide changes and is used to detect certain gases as extremely low concentrationsFor this experiment it was tested using NO2 After the annealing process at 300 C absorpt

45、ion sites opened allowing for low concentrations of N02 to cause a change in the resistance of the sensor. Gomez-Navarro, R. T. Weitz, A. M. Bittner, M. Scolari, A. Mews, Nano Lett. 7, 3499 2007./images/catalog/live/imageLibrary/35314ECE1517585314A3B395639BAE23M.jpgThe sensorCan detect a single atom

46、 of N02 which is shown in the figure belowWhen the N02 binds to thegraphene the electrical properties change and this canbe detected /images/GrapheneNO2-250_tcm18-95542.jpg24H. A. Becerril, J. Mao, Z. Liu, R. M. Stoltenberg, Z. Bao, and Y. Chen, ACS Nano 2, 463 2008.Problems that need further resear

47、chExploring methods to enhance sensor recoveryCurrently it takes the sensors longer than 30 minutes to recover under normal conditions Methods to be explored Low temperature heating UV illumination Leenaerts, B. Partoens, and F. M. Peeters, Phys. Rev. B 77, 125416 2008/uv%20600 x450.jpgUltrafast gra

48、phene photodetectorByFengnian XiaThomas MuellerYu-ming LinAlberto Valdas-GarciaPhaedon Avouris/images_di/photo-g/photodetector-27819.jpgGraphenes photonic abilitiesAbility to absorb 2% of incident light over a broad wavelength Multiple graphene layer absorb additively The absorption range of a syste

49、m can be tuned by changing the Fermi energy using an external gate fieldWang, F. et al. Gate-variable optical transition in graphene. Science 320, 206209 (2008)./images/NANOIDENTPhotodetectorFunction300.jpgField-Effect Transistors (FETs)Zero bandgap,large-area single or few-layers of graphene as FET

50、s are used in this paper Internal fields are shown in this paper to produce an ultrafast photocurrent response in graphene/weblib/ST%20Micro/Web%20Photos/New%20Photos/POWERSO-10jpg.jpg/objects/phw/news/thumb/14/2/10/graph1.jpgXia, F. et al. Photocurrent imaging and efficient photon detection in a gr

51、aphenetransistor. Nano Lett. 9, 10391044 (2009).Applications of Photonic applications High-speed optical communicationsInterconnectsTerahertz detectionImagingRemote sensingSurveillanceSpectroscopy http:/www.sflp.co.uk/xhtml-css/images/surveillance1.jpghttp:/www.delen.polito.it/var/optics/html/pics/o

52、ptics-main4.jpgGeim, A. K. & Novoselov, K. S. The rise of graphene. Nature Mater. 6, 183191 (2007).SEM and optical images of High-bandwidth graphene photodetector The graphene shown here has two to three layersTwo types of wirings are shown: groundsignal (GS) and groundsignalground(GSG)Optical botto

53、m left, SEM is the remaining black and white imageChuang, S. Physics of Optoelectronic Devices (Wiley, 1995).Figure obtained from articleSchematic of a PhotodetectorDevice schematics and electrical model in the high-frequency domainThe green symbols, from top to bottom, represent Cp, Cg and Rg, resp

54、ectively The purple sheet represents the graphene, and a pair of dark red strips denote the microwave probe tipsIshibashi, T. et al. InP/InGaAs uni-travelling-carrier photodiodes. IEICE Trans.Electron. E83-C, 938949 (2000).Image was obtained from paperThe High speed Impedance Impedance is an importa

55、nt relation of the physical set up of the device in order to filter out the low frequency signals from registering on the deviceThis equation is what sets the gate bias for the photodetector. Ryzhii, V., Mitin, V., Ryzhii, M., Ryabova, N. & Otsuji, T. Device model forgraphene nanoribbon phototransis

56、tor. Appl. Phys. Exp. 1, 063002 (2008).Photodetectors Magnitude of the photocurrent is strong function of the location of the optical illumination and also on the gate bias which are calculated with the impedance equationThe figure to the right displays the absolute a.c. photoresponse as a function

57、of light intensity modulation frequency up to 26 GHz with the gate bias varying from -40 to 80VMeric, I. et al. Current saturation in zero-bandgap, top-gated graphene fieldeffecttransistors. Nature Nanotech. 3, 654659 (2008).Future research for PhotodetectorsEnhancing the ability of the photodetecto

58、rs to detect a broader light position.The incorporation of photodetectors into useLarge scale manufacture of photodetectorsUse of photodetectors as transistors/en-us/um/people/jpwang/full_images/led_brdf.jpgElectronics and Magnetism of Patterned Graphene NanoroadsBy Abhishek K. Singh Boris I. Yakobs

59、on/media/2010/04/graphene-20100402.jpgNanoroadsCarving Graphene roads out of fully hydrogenated carbon sheets create “Nanoroads”This is a method in which the individual characteristics depending upon the zigzag and orientation can be studied to their corresponding affects. Graphane is shown to the l

60、eft and is full hydrogenated graphene Chen, Z.; Lin, Y.; Rooks, M. J.; Avouris, P. Physica E 2007, 40, 228./ceramictechtoday/tag/graphene/Graphene Vs. Graphanehttp:/www.afs.enea.it/project/cmast/Documenti/web/foto/Pulci_fig1.jpgPapers ConceptCan hydrogenation be used to form geometrical areas, such