固體物理學(xué)刪

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WhatareNanotubes?FabricationPropertiesApplicationsConclusionsWhatareNanotubes?DiscoveredbyIijima(1991,NEC)RolledupsheetofgrapheneCappedattheendswithhalfafullereneSingleWalledNanotube(SWNT)

SingleatomiclayerwallDiameterof0.4–5nm

MultiWalledNanotube(MWNT)

Concentrictubes~50innumberInnerdiameters:1.5–15nmOuterdiameters:2.5–30nmChiralvector-Definedonthehexagonallatticeaswhereandareunitvectors,andandareintegers.Thediagramhasbeenconstructedfor(n,m)=(4,2)infigure(a).Chiralangle,ismeasuredrelativetothedirectiondefinedby

StructureofCNTNomenclatureofthenanotubesCommonorientations:Armchair(5,5)Zigzag(9,0)Chiral(10,5)FabricationTechniquesArc-dischargeCriticallydependentonPHe,T,I+Goodquality,yield+MWNT,SWNT(ModifiedElectrodes)-CoveredwithamorphousC(unclean)LaserVaporization+LargeandalignedSWNTyield+Greatercontrolovergrowthcondition+absenceofhighelectricfield-expensiveprocessNd:YAGLaserGraphitetargetWaterCooledCopperCollector+-He(50–760torr)V:10–30VI:50–300AHydrocarbonDECOMPOSECatalyticposition+SWNT,MWNTonanysubstratenanotubesweaker,oftenuncappedFaultygraphitization,oftenatthetipsMetalNanoparticlesNanotubepropertiesElectronic:Dresselhausetal.(1995):(n-m)/3:integerMetallicconduction(allarmchairs):non-integerSemiconductor(two-thirdofzigzag,chiral)EffectofmagneticfieldEnergybandgapcanbeaffectedbyincreasingthemagneticfieldalongtheaxisBandgap(localbendingcurvature)-1Bandgap~100meV(IRregion)Magnetic:DiamagneticPronouncedanisotropicsusceptibility

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||BEnergybandgapEEFkykxGraphenekykxNanotubeProperties:contd.Mechanical:YoungModulus~1TPa(SWNT)and1.25TPa(MWNT)(Steel:230GPa)HighAspectRatio:1000–10,000Density:1.3–1.4g/cm3MaximumTensileStrength:30GPThermal:Conductivity:2000W/m.K(Copperhas400W/m.K)Nanotubetorturetest:repeatedbendingtofailure?InterestingFactsAboutMulti-WalledCarbonNanotubesTinyStripsofGraphitesheets,rolledintotubesCappedwithaFullereneateachendAfewnmacrossUpto100minlength100xstrongerthansteel,lightweightCanwith-standrepeatedbucklingandtwistingCanconductelectricitylikeCu,oractasasemiconductorlikeSiTransportsheatbetterthananyknownmaterialCurrentretailprice:~$200/gram1991Discoveryofmulti-wallcarbonnanotubes1992Conductivityofcarbonnanotubes1993Synthesisofsingle-wallnanotubes1995Nanotubesasfieldemitters1997Quantumconductanceofcarbonnanotubes1998ChemicalVaporDepositionsynthesisofalignednanotubefilms1999Hydrogenstorageinnanotubes2000NanotubesasIdealThermalConductorsMacroscopicallyalignednanotubes2001IntegrationofcarbonnanotubesforlogiccircuitsIntrinsicsuperconductivityofcarbonnanotubesCarbonNanotubes-ATimeLineApplicationsMolecularelectronicswithCNTsNanoprobesandsensorsEnergystorageOthersMolecularElectronicswithCNTsDiagramofacarbonnanotubetransistor,anelectronicdevicebasedonasinglerolled-upsheetofcarbonatoms.Inthefigure,acarbonnanotube(red;about1nanometerindiameter)bridgestwocloselyseparatedplatinumelectrodes(labelledinyellowas"source"and"drain"electrodes;spaced400nmapart)atopasiliconsurfacecoatedwithaninsulatingsiliconoxidelayer.Applyinganelectricfieldtothesilicon(viaa"gateelectrode,"notshown)turnsonandofftheflowofcurrentacrossthenanotube,bycontrollingthemovementofchargecarriersontothenanotube.(CourtesyCeesDekker,DelftInstituteofTechnology,theNetherlands.)

CarbonNanotubeTransistorCarbonNanotubeIntramolecularLogicGatesV.Derycke,NanoLetter(2001)CarbonNaotubeSingle-ElectronTransistorsatRoomTemperatureC.Dekker,Science(2001)CarbonNanotubeInter-molecularLogicGatesNanotubeElectronicsChipsmadefromtubes.Addingatoms(blueandred)toanall-carbonnanotubemakesthenanoworldequivalentofasemiconductorjunction--thebasisforcomputerchips.Nanotubesfore-beamsourcesColorNanotubeDisplayAfield-emissiondisplayusingcarbonnanotubes

Acrosssectionimage,madewithascanningelectronmicroscope,ofacarbonnanotubecathode.Thenanotubesarealignedperpendiculartothesubstrateandareembeddedintoametalelectrode.(Courtesy,SamsungAdvancedInstituteofTechnology,Korea)Carbonnanotubebasedfieldemissionx-raytubesNanotubeSensors:AFM,STM,CFMAFMtipsHighaspectratioenabletoreachdeeptrenchesCrashsurvival,mechanicallyrobustHighflexibilityCanresolvebiologicalstructure,chemicalfunctionalgroups(CFM)LowEulerBucklingforceUseinwatermediumSTM:useselectricalconductivityofnanotubeMeasureschargedensitywavesonthesurface(e.g.TaS2)Hafneretal.,Nature(1996)Nanotweezers:SeparationbetweentweezerarmsdependsonappliedpotentialMeasureelectricalpropertiesofnanoparticles(SiC),nanowires(GaAs)KimandLieber,Science(1999)Resonator,NanobalanceDeflectionofMWNTVs2IfVsisalternating:resonanceoccurs(sameaselastictheoryofbeams)Nanobalance:canmeasurepicogram–femtogrammasses.Pictureshowsv=968KHz,m=226fgPoncharaletal.,

Science(1999)NanotubeSpringChemicalSensorAdvantagesHighadsorptionsurfaceareaChangingelectricalpropertiesatroomtemp.Detectverysmallconcentrations(ppm)ofO2,NO2,NH3SemiconductingnanotubeDepletionoraccumulationofcarriersdependingonspeciesChangeofelectricalresistanceofSWNTwithexposuretoO2V-IcurvesforNH3andNO2exposureCollinsetal.,Science(2000);Kongetal.,Science(2000)ChemicalActuatorConstruction-NanotubesheetsstuckonoppositesidesoftapeSuspendedin1MNaClPrincipleOperatesbydifferentialelectronicchargingduetoanappliedpotentialDimensionalchangesinthecovalentlybondeddirectionsDeflections-upto1cmDynamic–upto15HzChargeinjectioninnanotubeCantilever-basednanotubeactuatorBaughmanetal.,Science(1999)Thermalpositionofacetyleneonnanochannelalumina(NCA)templatePrinciple:RadiationgreaterthanbandgapabsorbedIncreasesconductanceAdvantages:Broadwavelengthrange(~1–15μm)–easytunabilityIncreasingthicknessofCNTarrayfilmincreasesabsorptionHighlyorderedCNTarray=>improvedSignaltoNoiseRatioHundredsofindependentCNTsforeverypixel=>guardagainstfailureIRDetectorMetalcontactAluminamatrixTransparentelectrodehυXu,InfraredPhys.&Tech.(2001)MechanicalDeformationSensorIndividualSWNTbridgesmetalelectrodesonSiO2/Sisubstrate,partlyoveratrenchfabricatedinSiO2DeformationbyAFMtipDropinconductancebytwoordersLocalbondingdeformationsp2sp3Decreaseofπ(delocalized)electrons

DeformationConductanceTombleretal.,

Nature(2000)CarbonNanothermometerContinuous,unidimensionalcolumnofGalliuminCNTGreatestliquidrange(30–2,403°C)HeightofliquidgalliumvarieslinearlyandreversiblywithtemperatureExpansioncoefficientsameasmacroscopicgalliumGalliummeniscusperpendiculartoinnersurfaceofCNTEasytoreadGaoandBando,Nature(2002)Fluorescentlabelingcarbonnanotubes

Moleculesfillingofcarbonnanotube

Chemicalmodificationandfunctionalizationofcarbonnanotubes

NanotubeBiosensorNanowireBiosensorPrinciplesimilartochemicalsensorFunctionalizeSinanowirewithbiotinStudybindingofbiotin-streptavidinResults:Conductanceincreasesonadditionof250nMstreptavidinsolution(dueto–vechargeofstreptavidin)DetectconcentrationsdowntopMPossibletoconstructmicro-arraysofnanowiresTime(s)Ligand-receptorillustration250nMstreptavidinsolutionBiotinsitesblockedWithd-biotinCuietal.,Science(2001)

AHydrogenFilterfromNanotubesSuckinguptritium.Computersimulationssuggestthatcarbonnanotubes(blue)canpreferentiallyadsorbtritium(red)overhydrogen,evenifthetritiumisextremelydiluteinthegas.QuantumSievinginCarbonNanotubesandZeolites

QinyuWang,SivakumarR.Challa,DavidS.Sholl,andJ.KarlJohnson

Phys.Rev.Lett.82,956

(issueof1February1999)

CarbonNanotubeAnodesforLithiumIonBatteriesCarbonNanotubesasElectrochemicalsupercapacitorsArtificialMusclesMadeFromNanotubesLikenaturalmuscles,providinganelectricalchargecausestheindividualfiberstoexpandandthewholestructuretomove.However,anyapplicationofthisworkinreplacingbiologicalmusclesis"nearerthedreamfactorythanreality".Therealbenefitofthebreakthroughmaycomeingeneratingenergyfromoceanwaves.Nanotube'Peapods'ExhibitSurprisingElectronicPropertiesInyetanothersmallsteptowardbuildingnanoscaledevices,scientistshavedeterminedthatnanotubepeapods—minutestrawsofcarbonfilledwithsphericalcarbonmoleculesknownasbuckyballs—havetunableelectronicproperties.PublishedonlinebythejournalScience(2002),thefindingssuggestthatstuffingthestrawsprovidesgreatercontrolovertheelectronicstatesofsingle-walledcarbonnanotubes(SWNT).

CameraFlashPromptsCarbonNanotubeCombustionItsoundslikeaphotographer'sworstnightmare:thelightoftheflashbulbcausesthesubjectofthephototoburstintoflames.Butthat'sexactlywhathappenedrecentlywhenresearcherssnappedapictureofsomesingle-walledcarbonnanotubes,tinycylindersofpurecarbon.Thefindings,describedinareportpublishedinScience(2002),suggesttheminutestrawscouldbeusedastriggeringdevicesorforremotelight-inducedignition.CarbonNanotubeGears

ARMCHAIRWIREPROJECTCarbonNanotubesCouldServeasUltrafastOscillatorsTheminusculesizeofcarbonnanotubes-hollowcylindersmeasuringafewbillionthsofameterwide-canbogglethemind.NowpicturethestrawsnestledinsideoneanotherlikeMatryoshkadolls,withtheinnersetoftubesslidinginandoutabilliontimesasecond.Infact,accordingtoareportpublishedintheJanuary28th,2002editionofPhysicalReviewLetters,scientistscouldconceivablyfashionjustsuchagigahertzoscillator-onethatcouldaidinthecreationofnanomechanicaldevices.ConclusionsGrapheneMaterialsOutlinesIntroductiontotheGrapheneThenovelpropertiesofGrapheneGraphenenanoribbonsPartIIntroductiontotheGrapheneGraphene:easytomake,hardtofind.5mmGraphene(viaadhesivetape)Novoselovetal,Science306,666(2004)1μm0?9?13?SiO2SiAucontactsGRAPHENE1

m4mgraphenefilmsdowntotwomonolayersthickhangingoveragapinSiwaferopticalimageSEM(1kV)micrographWhatmakesgraphenestable?Theinteractionwiththesubstrate.Corrugationsinthethirddimensioninfreestates.Nature466,60(2007)Grapheneisoneatomthickandhencesoft!CrumplingGraphenehasatendencytoberoughandhavelocallyafinitecurvature:ripplingJ.C.Meyeretal.,Nature446,60(07)300nmTEMImageofagraphenesheetE.Stolyarovaetal.,cond-mat/0705.0833ScanningTunnelingMicroscopeFabricationofGrapheneMechanicalexfoliation

Science306,666(2004);PNAS102,10451(2005),etc.Epitaxialgrowth

Science312,1191(2006),etc.Processableaqueousdispersions

NatureNanotechnology3,101(2007).ChemicalsynthesisJACS130,4216(2008),etc.J.S.Bunchetal.,Science315,490(07)PartIIThenovelpropertiesofGraphenet~2.7eVSomeelectronicpropertiesofgrapheneBt’~0.1eVAAUnitcellNearestneighborsNextNearestneighborsCrystalstructureofgrapheneLatticevectors:Reciprocallatticevectors:Specialpoints:Tight-bindingapproachWheremeanscreates(annihilates)anelectron,

tisthenearestneighborhoppingenergy,t’isthenextnearestneighborhoppingenergy.EnergybandsKorK’InmomentumspaceDiracConeSemi-Metal“Ultrarelativistic”SolidStateatlowspeedoflightMathematicallyChirality(helicity)KK’G++--+=righthanded;-=lefthandedMinimumconductivityNature438,197(2005)VgmeansexternalgatevoltageHowtoopenanenergygap?NatureMater.6,

770(2007).NatureMater.6,

720(2007).Angle-resolvedphotoemissionspectroscopy(ARPES)datatakenonsingle-layergrapheneonSiCsubstrate.TheeffectoftheSiCsubstratePRL99,126805(2007)PRL99,076802(2007)AnomalousquantumHalleffect(QHE)Nature438,197(2005)Undermagneticfield,for2-Dfreeelectrongas:,isthecyclotronfrequency.

Undermagneticfield,forgraphene:,VFisthecyclotronfrequency.

2-DelectrongasGrapheneFutureadvancesor“wishlist”Magneticgraphene?ModifygraphenestructurallyorchemicallyandtailoritspropertiesattheatomiclevelFormationoflocalmomentsandincreaseinthenumberofcarriersSuperconductinggraphene?Electrondopingandenhancementoftheelectron-phononor/andelectron-plasmoncouplingB.Uchoa,AHCNPRL98,146801(2007)Freenon-relativisticelectronsinaboxPaulDrudeArnoldSommerfeld=Ignoranceisdumpedhere!NOLATTICEFelixBlochNOINTERACTIONSLevLandauFreerelativisiticelectronsinaboxPaulDiracIgnoranceisdumpedhere!DISORDERINTERACTIONSPartIIIGraphenenanoribbonsWhatareGraphenenanoribbons(GNRs)?UnlimitedLimitedZigzagGNRsUnlimitedLimitedArmchairGNRsWidthofGNRsJourn