快速热处理化学气相沉积法制...理的轻质柔性石墨烯（英文）_Satendra Kumar.pdf

Cite this:NewCarbonMaterials,2023,38(3):534-542DOI:10.1016/S1872-5805(23)60737-1Flexible and lightweight graphene grown by rapid thermal processingchemical vapor deposition for thermal management inconsumer electronicsSatendraKumar1,2,ManojGoswami1,2,NetrapalSingh1,2,UdayDeshpande3,SurenderKumar1,2,*,N.Sathish1,2,*（1.Academy of Scientific and Innovative Research(AcSIR),Ghaziabad 201002,India;2.CSIR-Advanced Materials and Processes Research Institute(AMPRI),Bhopal 462026,India;3.UGC-DAE Consortium for Scientific Research,University Campus,Indore 452001,India）Abstract：Next-generationconsumerelectronicsrequireexcellentthermalmanagement.Grapheneisagoodchoicebecauseitsthermalconductivityis13timesthatofcopper.Single-,bi-andfew-layergraphene(SLG,BLG,FLG)withlargesp2domainsweregrownbyrapidthermalprocessingchemicalvapordeposition(RTP-CVD)fromCH4andH2usingArasthedilutinggas.ThequalityofgraphenewasinvestigatedbyRamanspectroscopyandTEM.TodemonstratetheheatdissipationcapabilityofRTP-CVD-growngraphene,a2TBsolidstatedrivewasusedandthetemperaturewasmeasuredbyaFLIRthermalcamera.ResultsindicatethathighthermalconductivitygraphenewaspreparedbydilutingtheprecursorgaswithAr.SLGwaspreparedatagrowthtemperatureof1000Candatimeof25min.AtransitionfromFLGtohigh-qualityBLGwasobservedatlowH2concentrations.UsingSLG,therewasa5Clowertemperaturerisethanusingacommercialcopperheatdissipator.TheheatdissipationabilityofSLGwasapproxim-ately200timesthatofcommercialcopperheatdissipators.Key words:Graphene；Thermalmanagement；Consumerelectronics；Chemicalvapourdeposition1IntroductionInnovationinthermalmanagementtechnologiesis driven by the continual downsizing and risingpowerdensityofelectronicdevices.Duetotheirheftymass,suchasmetalheatsinks,conventionalheatre-movalsolutions,cannotsatisfytheneedsofportableelectronicdevices13.Intherealmofelectronicpack-aging,composites of a metal matrix with excellentthermal conductivity and adjustable coefficients ofthermal expansion have attracted particular interest.Due to its excellent thermal conductivity,copper iswidelyusedtospreadheatinelectronicdevices4.Be-causeofitsexceptionalthermalconductivity(5300W/mK),high flexibility,and lightweight,graphenehasbeenregardedasasuperiorthermalinterfacema-terial57.Rapidphonongroupvelocity(23.6m/sforLA branch)and a lengthy phonon mean free path(240nm)combinetogivegrapheneitsextremelyhighthermal conductivity8.The thermal conductivity ofgrapheneisdecreasedbydefectsincludingvacancies,isotopicdoping,andchemicalfunctionalgroups.Sev-eralwaysofgraphenesynthesismethodshavebeenreportedsuchaschemicalandelectrochemicalexfoli-ation9,epitaxial growth on the SiC crystal10,andgrowth through CVD11.Chemically synthesizedgrapheneoxide(GO)hasbeenusedtopreparemetalcompositeforheatdissipation.Itenhancesthethermalconductivity(260W/mKor15%)ofAluminumbutnot up to the mark12.Because chemically synthes-izedgraphenehasseveraldefectsandremainingfunc-tionalgroupswhichreducethethermalconductivity.Chaeetal.reportedenhancedheatdissipationbyheal-ingthedefectsinreduced-GO13.IncomparisontothethermalconductivityofGO(1.92W/mK),thethermalconductivity of reduced-GO was increased to9.90W/mK.Additionally,thedefect-healedreduced-Received date：2022-12-17；Revised date：2023-01-30Corresponding author：N.Sathish.E-mail:;SurenderKumar.E-mail:surenderampri.res.inAuthor introduction：SatendraKumar.E-mail:Supplementarydataassociatedwiththisarticlecanbefoundintheonlineversion.第38卷第3期新型炭材料（中英文）Vol.38No.32023年6月NEWCARBONMATERIALSJun.2023GOwassuccessfullyusedasaheat-dissipatingmater-ial,causingittocooldownswiftlyby36C.Rhoetal.demonstrated porous copper/SLG/reduced-GOcompositeforafanlessheatdissipator14.Witha9Clower peak temperature,the porous copper/SLG/re-duced-GO composite dissipated heat more quicklythancopper.However,CVD-grown graphene with a largearea,defects-free,andself-limitingtoasingleorfewlayers,isverysuitableformassproductionwitheas-ilytransferrable15.RTP-CVDisdifferentfromcon-ventional CVD due to rapid thermal ramping andcooling.Theconventional CVD setups require hightemperaturestogroweithersemiconductoror2Dma-terials such as graphene.On the other hand,RTP-CVD requires comparatively low temperatures withfastrampingandcoolingupto15C/s.Toobtainde-fects-free and high-quality graphene through RTP-CVD,stillthereisarequirementtooptimizevariousparameterslikegrowthtemperature,time,chamberat-mosphere,precursor gases and substrates16.Ramanspectroscopyisapromisingtechniquefortheinvest-igationofgraphenequality1718.Ramanspectroscopyalongwithhigh-resolutionTEMcandistinguishthenumber of layers,defect,and doping level ingraphene1920.Herein,we have reported the effect of growthparameters in RTP-CVD to engineer the defects ingraphene.With a one-step growth parameter,graphenesheetswereinvestigatedbyRamanspectro-scopy and high-resolution TEM.The high-qualitygrapheneis demonstrated as a flexible and light-weightheatdissipatorforconsumerelectronics.2Experimentalsection 2.1 Growth of grapheneAn RTP-CVD(APT-TF200)based bottom-upapproachisusedtogrowgraphenerecipesona25mthickcopper foil.Initially,the copper foil was an-nealedunderH2at100standardcubiccentimetersperminute(mL/min)for30min.Duringthegrowthof10 min,the precursor(CH4 and H2)ratio of 124mL/minwasmaintained,withchamberpressureintherangeof2.5-4.0Mbar.Thesubstratetemperaturewasmaintainedat1000Cthroughouttheannealingandgrowthprocesses.ArconcentrationwasvariedforH2dilution.The sample designation for 70,80 and100mL/minofArconcentrationisAr-70,Ar-80andAr-100,respectively.Pristine SLG is prepared atgrowthtemperatureandtimeof1000Cand25min,respectively.GraphenetransferonthecoppergridfortheTEMstudywasdonewithawetchemicalmethodasshownschematicallyinFig.1andisexplainedinthesupplementaryinformation(SI)section.2.2 Growth mechanism of grapheneFor the removal of the native oxide layer andsmootheningofthecoppersurface,a30minanneal-ingwasdoneinthepresenceofmolecularH2(100mLmin1).Duetoannealing,someH2isdiffusedin-sidethecopperfoil.ThisatomicH2,impurityoxides,defects,andgrainboundariesover/insidethecopperfoilarethebasicbuildingblocksforgraphenenucle-ationonCu(111)21.Duetothecatalyticdecomposi-tionofCH4overthesurfaceofthecopperpossibledi-mers,trimers,andadatomsaregeneratedasequations(1)&(2)andschematicallyshowninFig.2(a):CH4(g)CH4(s)(1)CHx(s)+(s)CHx1(s)+H(s)(2)Theequation(2)continuesuntilthewholeCHxisconvertedintoC(s)andH(s)2223.Alargeconcentra-tionofH2blocksthegraphenenucleationsitesoncop-perfoil.Becauseofthat,atalowerargonamount(Ar-70),alargenumberofpoint-defectedgraphenesheetswere grown.The increment of argon concentration(dilution of H2)is responsible for the activation oflargecatalyticsite(s)oncoppertogrowhigh-qualityanddefects-freeBLGandSLG.ForAr-100,graphenegrowthcontinuestoformlargefour-armeddendriticstructuresandtriestocoveralargeportionofthecop-perfoil.AsthechamberismoredilutedwithH2gas,theprecursorisalsogettingdilutedwhichleadstotheterminationofgraphenegrowth.Thegeneralequation(3)ofgraphenegrowthcanbewrittenas:Graphene+CxHy(s)(GrapheneCx)+yH(s)(3)第3期SatendraKumaretal:Flexibleandlightweightgraphenegrownbyrapidthermalprocessingchemical535ItmeanspristineSLGrequiremoregrowthtimetocoverthewholesubstrate.Inspiredbytheabovediscussions,SLG is also grown only by increasinggrowthtimeto25min(discussedlater).3ResultsanddiscussionField-emission scanning electron microscopy(FE-SEM)imagesinFig.2(b-d)showacloserela-tionshipbetweenthenumberofnucleiperunitareaandthepercentageareacoveredwithH2dilution(in-creasingArconcentration).Randomlyshapedgrapheneflakestofour-armedlargedendriticflakesaregrownbyH2dilution.ThecoppersurfaceisetchedproperlyuponH2dilutionwhichresultsinlargecrys-tallite and defects-free BLG.For Ar-100,dendriticflakesareveryorganizedandgrowninamatrixfash-ion.Fig.S1showsthatthenumberofnucleiperunitareafallsdrasticallyfrom3200(Ar-70)to2000(Ar-100)inaconcave-downfashion.AtlowArflow,thecoppersurfacewasnotetchedandsmoothedproperlydue to which more nucleation sites were garneredwhichresultsindefectiveFLG(Ar-70andAr-80).Raman spectroscopy is used to confirm thegraphene growth,quality,and etching of the nativeoxidelayer.Afull-rangeRamanspectrumofAr-100sampleintherangeof1100-3000cm1isprovidedinFig.S2.Here,itisveryclearthatthereisnosuchD-peakobservedthatcorrespondstostructuraldefectsinRTP-CVDgraphenesheets.Ontheotherhand,aweakNative Cu foilGraphene/Cu foilSpin-coating80 oC1 hPMMA/Graphene/Cu foil2000 r/min60 sGraphene onTEM gridCleaning of PMMAGraphene fishingwith TEM gridPMMA/Graphene/TEM gridEtching of Cu foilFig.1SchematicrepresentationofgraphenetransferonTEMCugridCH4(a)(b)(c)(d)CH4Radicals20 m20 m20 mCH2-CH2Stage-IStage-IIStage-IIIStage-IVStage-VDimerTrimerH2H2ArFig.2(a)Theschematicrepresentationofchemisorption/depositionofgrapheneoncopperfoil.Stage-I:dissociativedehydrogenationofCH4,Stage-II:dimer-ization,Stage-III&Stage-IV:trimerizationandmigration,andStage-V:growthofgraphene.FE-SEMimagesof(b)Ar-70,(c)Ar-80and(d)Ar-100samples536新型炭材料（中英文）第38卷peakat2450cm1isattributedtobothaDphononand acoustic longitudinal phonon(D”),hence thecombination is denoted by the notation G*-band.Stacked Raman spectra of as-grown graphene areshowninFig.3(a).Withtheabsenceofdefectband(D),graphitic(G)anddoubleresonancesignature(2D)areobtainedineachcase.ThegraphenequalityismonitoredwithI2D/IGratio,andFLGtoBLGqual-ityisimprovedupontheH2dilution.Thelargefullwidth at half maxima(FWHM)is found for thesampleAr-70(23and61cm1forGand2D)duetoimproperetchinganddefects(Fig.3(b,c).TheG-and 2D-peaks are deconvoluted with one(at1607 cm1)and two(2659 and 2720 cm1)sub-peaks,respectively.Theimproperetchingandnativecopperoxides are also monitored in different loca-tionsofAr-70(Fig.3(d).FourdifferentnativeoxidepeaksofCuO(at215and632cm1)andCu2O(at148and412cm1)arefoundwhichresultedinadefectiveand small domain FLG24.As the H2 concentrationwasdilutedmore(Ar-80andAr-100),G-peakisblue-shiftedwithnarrowFWHMwhile2D-peakshiftedtothepristineBLGsposition,showninFig.3(e-h).The2D-peakofAr-100isfurtherdeconvolutedwithfourLorentzianpeaks(2673,2685,2693and2714cm1)whichisthestrongsignatureofBLG.ThegraphenequalitiesmentionedabovearealsoconfirmedwithRamanmappingwhichgivesaclearpicture.A20.50m20.50mareawasselectedforthemappingofeachsample.Fig.4(a,d,g)representstheGmappingofAr-70,Ar-80andAr-100,respect-ively.The G of Ar-70(1590 cm1)and Ar-80(1590cm1)issomewhatred-shifted(greenregion:lowwavenumber)fromthenanocrystallinegrapheneposition1600cm1.Thered-shiftingofGinAr-70andAr-80isduetotensionthatcanbeseenintheFWHMmappinginFig.S3(a,e).SinceG-peakisun-dertensionduetothedistortedhoneycombstructure,whichleadstothewideningofRamanspectraofthe2DbandinFig.S3(b,f).TheCuOisalsomappedaround632cm1inFig.S3(c).Fig.S3(d)showsclearpictureofCuOintensityvariation.The2DmappingofAr-70,Ar-80andAr-100canbeseeninFig.4(b,e,h).However,inthemappingof2D,mostofthere-gionisred-shiftedinAr-70.ThefurtherdilutionofH2leadstotheblue-shiftingofthe2D-bandinthecaseofAr-80andAr-100.AlmosteverydendriteofgrapheneiscoveredwithnanocrystallineBLGinAr-100andnarrowFWHMfrom40-80cm1inFig.S3(h).TheabovebehaviourmoreclearlycanbeseeninFig.S4(a,b,d,e,g,h),zoomedarea(redcircles)ofparticu-larinterestinFig.4.Fig.4(c,f,i)representsthequal-G:1575FWHM:23G:1582FWHM:18G:1584FWHM:152D:2689FWHM:612D:2701FWHM:662D:2689FWHM:28D:1607FWHM:1.2Intensity/(a.u.)Intensity/(a.u.)Intensity/(a.u.)Intensity/(a.u.)Intensity/(a.u.)Intensity/(a.u.)Intensity/(a.u.)Intensity/(a.u.)1400 1600 2400 2600 2800Ranan shift/cm11470154016101680Ranan shift/cm12500260027002800Ranan shift/cm1150300450600Ranan shift/cm11470154016101680Ranan shift/cm12500260027002800Ranan shift/cm11470154016101680Ranan shift/cm12500260027002800Ranan shift/cm1Ar-100(a)(b)(c)(d)(e)(f)(g)(h)I2D/IG=1.41I2D/IG=0.36I2D/IG=0.18Ar-80Ar-7012320 m4512345Fig.3(a)StackedRamanspectraofAr-70,Ar-80andAr-100withtheI2D/IGratio.(b,c,d)G-band(G),2D-band(2D),andnativeoxideRamanspectraforAr-70.(e,g)and(f,h)istheG-and2D-bandspectraforAr-80andAr-100,respectively.TheG-bandposition,2D-bandposition,andFWHM(FWHM)areincm1第3期SatendraKumaretal:Flexibleandlightweightgraphenegrownbyrapidthermalprocessingchemical537itydistribution(I2D/IGratio)ofas-growngrapheneforAr-70,Ar-80andAr-100,respectively.Thisdiscus-sionisclearerinFig.S4(c,f,i)forAr-70,Ar-80andAr-100,respectively.The central region of two-di-mensionalimagesismostlycoveredwithrespectivegraphenelayersbuttheedgeshaveI2D/IGratiogreaterthan 4 which may lead to the turbostraticity whichwillbediscussedlater.Vacancydefects,edges,linearchains,bondrota-tions,andlayernumbersareinvestigatedbyhigh-res-olution TEM for a better understanding of as-pre-paredgraphene.High-resolutionTEMimagesoftheAr-70sampleareshowninFig.5(a,b)andarangeofpointdefectsarepresent.Themono-andmulti-vacan-ciesaredirectlyobservableincludinganextendedzig-zagmonovacancieschain(bluehighlight).Aschemat-icrepresentationofpointdefectsisshowninFig.5(c).Fig.S5(a-c)showsdifferenttypesofdefectssuchaspoint,lineandvacancydefectsinAr-70.FLGedgesareshowninFig.S5(d,e)betweenthedashedyel-lowlines.ThesextetoftheSAEDpatternhasadiffer-entbrightnessandshowsanon-AB-stackedgraphenelayer having a range of twist angles,shown inFig.5(d).As H2 is diluted(Ar-80),the etching ofcopper foil was enhanced which leads to the AB-stacked(Bernal Stacking)FLG with layer numbersandfewerdefects,showninFig.5(e-g).TheSAEDpatterninFig.5(h)showsanAB-stackedFLGwithrotationalanglesbetween2and40.Thelayernum-bersarereducedfrom10(Ar-70)to6(Ar-80)duetotheproperetching.FurtherdilutionofH2(Ar-100)producesBLGwithlesserdefects,showninFig.5(i,158015901600161010(a)(b)(c)(d)(e)(f)(g)(h)(i)505101050510Y/mX/m26802690270027101050510X/m12341050510X/m158015901600161010505101050510Y/mX/m26802690270027101050510X/m12341050510X/m158016001620164010505101050510Y/m1050510Y/m1050510Y/m1050510Y/m1050510Y/m1050510Y/m1050510Y/mX/m26602680270027201050510X/m12341050510X/mFig.4Two-dimensionalplotsofRamanmappingof(a,d,g)G-band,(b,e,h)2D-band,and(c,f,i)I2D/IGratioforAr-70,Ar-80andAr-100,respectively538新型炭材料（中英文）第38卷j).The inset of Fig.5(k)shows the high-resolutionTEM image of 2 atomic-carbon layers.The SAEDpatterninFig.5(l)showsthenon-BernalstackedortwistedBLGwithatwistangleof21.5.TheAr-100samplealsoshowssometracesofSLGthatconfirmthe proper etching of copper foil with H2 dilution,showninFig.S5(f).AsthedefectsarehealingwithH2 dilution,turbostratic factor(F)is approachingpristine SLG(1).Turbostraticity is calculated withthehelpoftheSAEDpattern(Fig.S6)fromequationS1,andtheresultsaresummarizedinTableS1.TheabovediscussionsarealsoconfirmedbyX-rayphotoelectronspectroscopy(XPS).TheC1sresultof Ar-100 is found to be similar to those for thepristine BLG(Fig.6(a).The sp2 carbon peak(284.84 eV)is symmetrical with fewer functionalgroups.Additionalspectralpeakswereassignedtoal-cohol(COH)andester(OCO)at285-286and288eV.TheO1sspectruminFig.6(b)isdeconvo-lutedinto4majorpeaksat529.95,530.68,531.62and532.87eVlabelledasmetaloxides(Me-Ox),OC,OCandH2O,respectively.Anadditionalimpurity(SiO2)appearedduetotheoxideformationinsidethequartzchamberorfromenvironmentalexposure.XPSresultsinFig.6(c)areinterestingands