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2Grapheneonmetalsurfaces

3J.Wintterlina,*,M.-L.Bocquetb

4aLudwig-Maximilians-UniversitätMünchen,Dept.ChemieundBiochemieandCenterforNanoscienceCeNS,Butenandtstr.5-13,81377Munich,Germany5bUniversitédeLyon,LaboratoiredeChimie,EcoleNormaleSupérieuredeLyon,CNRS,F69007Lyon,France

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8articleinfo

9Articlehistory:10Availableonlinexxxx

11Keywords:12Review13Graphene14Metalsurfaces15Nickel16Ruthenium17Platinum18Iridium1920abstract

21Thearticlereviewsworkongraphenemonolayersadsorbedonmetalsurfaces.Graphenelayersonmetals22havebeenpreparedbysurfacesegregationofcarbonandbydecompositionofhydrocarbons.Thefilms23areoftennotrotationallyalignedtothemetalsurface.However,foranumberofhexagonallyclose-24packedsurfacesperfectlyorderedepitaxialoverlayerscanbeobtained,withdomainslargerthantheter-25racesofthemetalsubstrate.Inmostcasesthewell-orderedoverlayersdisplaymoiréstructureswith26largeperiodicities,resultingfromthelatticemismatchbetweengrapheneandtheunderlyingmetal.27Thesestructuresareconnectedwithabucklingofthegraphenelayerindicatinglocalvariationsofthe28bindingtothemetal.Forthemetal–graphenespacingsvaluesbetweenapproximately2.1and3.8Åwere29found,dependingonthemetal.Reasonsforthesestrongvariationsarenotyetclear,butthereareindi-30cationsthatthesystemsfallintotwoclassesthatdifferqualitativelywithrespecttothemetal/graphene31interaction.Thesevariationsarealsoreflectedbytheelectronicstructure.Therearemetal–graphenesys-32temsinwhichthepbandissignificantlydownshiftedinenergycomparedtothefree-standinggraphene,33andabandgapofordereVhasopenedatthe󰀂KpointoftheBrillouinzone.Inothersystems,theelectronic34structureoffree-standinggrapheneisalmostintact.Theperfectnessoftheepitaxialmoiréphasesoffers35promisingapplications,e.g.,astemplatesfornanostructures.36Ó2009PublishedbyElsevierB.V.

37

38391.Introduction

40Thepublicationin2004ofamethodtopreparefree-standing

41graphene,single2Dcarbonsheetswiththesamestructureasthe

42individuallayersingraphite,hasinitiatedenormousscientific

43activities[1–4].Grapheneisauniquematerial.Itisstrictly2D

44(apartfromasmall,long-rangebuckling[5]),ithasahighcrystal-

45lographicquality,anditisstableunderambientconditions.Ithasa

46veryspecialelectronicstructure,thepandp*bandstouchinasin-

47glepointattheFermienergy(EF)atthecorneroftheBrillouin

48zone,andclosetothisso-calledDiracpointthebandsdisplayalin-

49eardispersion.Thistopologyofthebandsgivesrisetoexoticelec-

50tronictransportproperties–thechargecarriersbehavelike

51relativisticparticles–whichmanifestthemselvesinunusualphe-

52nomenasuchasananomalousquantumHalleffect[6,7].Thebal-

53listicchargecarriertransportat300Kandathighchargecarrier

54concentrationsmakesgraphenealsointerestingforapplications

55inelectronicdevices[4].

56Intheadsorbedformonmetalsurfacesgraphenehasbeen

57knownforatleast40years.Theformationofgraphenewasfirst

58observedduringpreparationofPtandRusinglecrystalsurfaces

59[8–12].Whenduringtheusualpreparationthesampleswere

60annealedtohightemperatures,carbonimpuritiessegregatedfrom61thebulktothesurface.Itwassoonrealizedthatoneformofthis

62surfacecarbonisgraphene[11].Grapheneonmetalsurfacesisalso

63knownfromindustrialheterogeneouscatalysis,where,forreac-

64tionsinvolvinghydrocarbons,thedepositionofgraphiticcarbon

65onthecatalystsurfaceisamajorreasonfordeactivation[13,14].

66Recentinvestigationshaveshownthatthesegraphiticlayerscan

67consistofafewgraphenelayersonly,orevenofmonolayers

68[15].Notsurprisingly,thecurrentboominresearchonfree-stand-

69inggraphenehasledtorenewedinterestingrapheneadsorbedon

70metalsurfaces.Explorationofthesesystemshasmeanwhilebe-

71comeathirdmainfieldofgrapheneresearch,inadditiontoinves-

72tigationsoffree-standinggrapheneandofepitaxialgrapheneon

73SiC.(ThedecompositionofSiCisthesecondmajormethodfor

74graphenepreparation[16–18],apartfromthemechanicalexfolia-

75tionfromgraphite.)

76Inthiscontribution,wegiveanoverviewofresultsformetal–

77graphenesystems.Theavailablepublishedmaterialongraphene

78onmetalshasstronglygrownsincetwopreviousreviewsfrom

791997[19,20],andcurrentlythefieldisdevelopingsorapidlythat

80wecannothopetoprovidemuchmorethanasnapshot.Animpor-

81tantissueinmanyoftheinvestigationshasbeenthequestionof

82howthegraphenelayerinteractswiththemetal,which,ofcourse,

83isthediscriminatingfactorfromisolatedandSiC-supportedgraph-

84ene:Isthegraphenelayerphysisorbed–asonemayexpectfrom

85theveryweakinteractionbetweenthelayersinbulkgraphite–

86orisitboundmorestrongly?Andhowistheelectronicstructure

0039-6028/$-

seefrontmatterÓ2009PublishedbyElsevierB.V.doi:10.1016/j.susc.2008.08.037*Correspondingauthor.Tel.:+4908921807606;

fax:

+49089218079994.E-mailaddress:

wintterlin@cup.uni-muenchen.de

(J.Wintterlin).SurfaceSciencexxx(2009)xxx–xxx

ContentslistsavailableatScienceDirect

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Pleasecitethisarticleinpressas:J.Wintterlin,M.-L.Bocquet,Surf.Sci.(2009),doi:10.1016/j.susc.2008.08.037