F F F F F F F F F F F F F Ui

F F F F F F F F F F F Iiq

QFIFP emperture progrmmed growth on sr@QQPA F

during the writing timeD like ll those times you hd to ook t weird hoursD or

@ixminteurA qeorgi eh hysis wmeF Laurence Magaud hireteur de reherhe @ixmintrieA snstitut xéel wmeF Muriel Sicot ghrgé de reherhe @ixmintrieA niversité de vorrine wF Antonio Tejeda ghrgé de reherhe @hireteur de thèseA niversité risEud wmeF Amina Taleb-Ibrahimi hireteur de reherhe @goEdiretrie de thèseA ynhrotron oleil s would like to thnk (rst of ll the jury memers rF prnine ollD rF tenEwr hemlinD rF ydile tephnD vurene wgud nd rF idwrd gonrdD for their inE sightD fruitful disussionsD interest nd dvie in this workF es my thesis developed in three min sites @niversité ris udD ynhrotron oleil nd niversité de vorrineAD there re numerous people s would like to knowledge nd thnk for their ontriution to this thesis workF o my thesis diretorD entonio ejedD you were more thn s ould wish for in supervisorD s you were very involved in my workD whether it ws from the o0e next door or from ny ountry round the worldF por these pst three nd hlf yers s ppreited gretly the trust you put in meD from smll things s the (rst time s mounted smple @whih took few hoursA until the end where s ould perform experimentl mpigns on my ownF s ould lwys rely on you nd s feel very luky to hve hd suh supportive supervisorF ivery time s strted to dout myself you were lwys there to remind me the vlue of wht s ws doing @like our REpoint grphD whih is tully gret del of work 3AF s will lwys rememer the joy s felt when something went extly s we plnned nd how eger s ws to show you the resultsD s s knew you would e just s exited s meY you truly understnd the stisftion of siene wellEmdeF end never forget the time the seurity people onfused me with your kidD whih lwys rings smile to our fesF o my thesis oEdiretorD emin leEsrhimiD s wnt to thnk you euse you mde me feel like prt of your fmily y giving me dvie not only on the sienti( plne ut lso on the personl oneF s know you were working from the shdows nd lwys hd good word to sy out meF ou never hesitted to tell me the good nd the dD nd s ppreite your honestyF s m lso gld s ould shre with you experienes outside of the thesis frmeworkD s the mzing disovery of the est resturnt in frelon @tht s will keep on visitingAF hnk you for your trustD your supportD your dvies nd your kes 3 Q R o my thesis godmotherD elin ldD s wnt to thnk you for your disponiility nd enourgement wordsF ivery tlk we hve is lwys plesureF huring my sty t the niversité de vorrineD s met wonderful people tht helped me expnd my sienti( knowledgeF s would like to thnk the diretor of the urfes et petrosopies temD hniel wlterreD for your kind welome to the temD for your interest in my workD for the opportunity to experiene your gret tehing nd your hllenging questions tht lwys kept my hed spinningF his (rst yer wouldn9t hve een possile without the supervision of wuriel iotF e spent together numerous wG experimentl sessions on the iridium systemD in whih s tried to sor from you s muh s s ould @this led to numerous hiers full of tiny notes until the (nest detilAF s ppreite your sense of detil nd s ws espeilly gld tht you ould understnd my struggles with the size of the experimentl setupF hnk you for your ptieneD your experiene nd your supportF es prt of the urfes et petrosopies groupD s m grteful to vu woreuD for his neverEending help when my rms were too tiny to reh the helium entry of the mirosopeD when s needed help to trnsport the nitrogen tnk through the universityD s well s his thoughts on the importne of knowing wht is hppening inside the lk ox insted of just pushing uttonF s would lso like to thnk the rest of the urfe nd petrosopies temD fertrnd uierren nd nnik pgotEevurtD for their gret onverstion t lunh time or ny time we rossed eh other t onfereneF o tulien qrnetD you were gret o0e mte for the one yer s ws in xnyF hnk you for your help nd dvie with the mirosopeD s well s your humour nd kindnessF o quillume sseurD you mde me feel t home when s ws in xnyD you were so ptient with my very poor frenh when s rrived nd lwys hd time for eerD dinner or o'ee time nd little ht on how the experiments were doingF et the niversité de ris ud s hd the opportunity to perform high level experiE ments nd ollorte with experts on the iw (eldF s would like to thnk elexndre qloter nd elerto oelli from the wirosopie életronique groupD for their ontriE utions on the understnding of the grphene sidewll system from the experimentl @iwA nd theoretil @hpA point of viewF sn dditionD s would like to thnk iE oyn vi for her experieneEshring on the thinning proess tht s lter dpted to the sidewll smplesF s m grteful to omin fourrellier for the help on the very (rst trils we performed on grpheneF s lso would like to thnk the diretor of the vortoire de hysique des olides E ylvin vy nd the vumière ltrrèveD gohérene et Èletrons temD nmely S wrino wrsiD ivngelos plzrouD hvid ve follo9hD inent tquesD xiols woisnD grlo pezzni nd vu yrteg for their fruitful disussions nd interest in my workD s well s the sul dy to dy onverstions t lunh timeF o the dotorl nd postEdotorl ollegues of vrious temsD winEs veeD ssel qonzlezEllejoD xiloufr xilforoushnD vm uhlilD wro gputoD iwen felle nd enn rrnD s wnt to thnk you for ll the supportD the o'ee reks nd insightful onverstions tht most of the time hd nothing to do with sieneF roweverD when prolem me @espeilly with sgorD yesD you knowAD s9m gld we ould exhnge solutions nd lso think out sieneF ou mde my sty t v very plesing nd full of surprisesF huring these three yers of hhD s spent fir mount of time t the ynhrotron oleil in ssoition with the gssiopée emlineD where ll my ei experiments were performedF s would like to thnk the permnent st' of the emlineD prnçois fertrnD trik vefèvreD tulien ultD prnçoise heshmps nd hniel gonnet for their support on my experimentl mpignsD their trustD their kind words of enourE gement nd numerous onverstions out frenh ulture t lunh timeF s would like to knowledge the support of tefn uusky nd prnçois xiols during the w experimentl mpigns on the pltinum nd iridium system nd thnk them for their )exiility on my lortory requests nd on(dene in my hndling of the urfe vortory hmersF s would like to thnk postEdotorl ollegue srene lioD with whom s egn the study of the grphene sidewll systemF ou tught me to hve on(dene nd to (ght for wht is rightF s dmire still the energy you hve ll the timeF ou helped me to grow oth on the sienti( nd personl plneD nd it ws lwys fun to e round youF hnk you for your support nd high hopes for meD you seeD s mde itF o the postEdotorl ollegueD wy xrynnD we spent lot of time togetherD s long experimentl mpignsD summer shoolsD onferenes nd even trip to etlnt with our ollortorsF s wnt to thnk you for ll your support nd help through my hhF ou hve very positive wy of thinking nd mny stories to tellD espeilly when we hd long emtime hoursF s think we eme wellEoiled mhine y the end of my hh nd s m grteful for hving shred so mny di'erent experienes with you nd to hve lerned from youF s would lso like to thnk our ollortors from the qeorgi eh snstituteD lt de reerD glire fergerD idwrd gonrdD nd dotorl students weredith xeviusD peng ng nd tenEhilippe urmudD s they provided the grphene sidewll smples T tht were studied in this thesis workF s hd the fortune to shre numerous experimentl mpigns with themD whih deepened the qulity of this workF edditionllyD s spent two weeks in etlnt t the qeorgi eh snstituteD where s ould lern from their growth tehniques nd hve n enrihing sienti( exhngeF s wnt to thnk my friendsD for their support nd loveD lose or fr wyD s rry you round with meD to ilizD viyD oD endreD wrinD ermísD wriferD uirillD wriD wrioD uterinD irikD hilippD vurD gorinnD mr nd srvingF s lso wnt to thnk my fmily for their supportD espeilly to my prents irgini nd tun grlos nd to my rother velF st ws lwys di0ult to understnd wht it is tht s doD ut it ws thrill to shre this suess with you @nd thnks for the wexin food t the potAF o wrEentoineD my life prtner nd est friendD thnk you for your reD supportD ptiene nd understndingF s nnot egin to thnk you for the sri(es you mde Introduction 9

1 Fundamentals of graphene nanoribbons

IFI truture nd eletroni properties F F F F F F F F F F F F F F F F F F F F IQ IFP reprtion methods F F F F F F F F F F F F F F F F F F F F F F F F F F F F IU IFPFI opEdown pprohes F F F F F F F F F F F F F F F F F F F F F F F F IU IFPFP fottomEup pprohes F F F F F F F F F F F F F F F F F F F F F F F PP IFQ idge stility nd edge sttes F F F F F F F F F F F F F F F F F F F F F F F PR IFR rnsport gp F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F PT IFS hevies F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F PW 2 Experimental techniques
Introduction iletroni devies hve eome our everydy ompnionsF hey re everywhere in our lives sine minituriztion hs llowed extremely powerful devies to e portleF winituriztion itself ws mde possile thnks to the development of nnoeletronisF sn this seek for minituriztionD grphene hs een extensively studied euse of its mny ppeling propertiesD s its ility to dissipte hetD its high moilityD its high urrent rrying pilities or its llisti trnsportF roweverD in order for grphene to e used s trnsistor hnnel on eletronisD it must e possile to swith etween the onGo' sttes @IGH sttesA in n e0ient wy @(gF IAF he prolem is tht sine grphene hs zero nd gpD it is lwys ondutive his thesis is preisely dedited to the orreltion etween frition methods with the tomi struture nd eletroni propertiesF en introdution to the generl physis of nnorions nd the existing methods of synthesis is presented in hpter IF e hve foused on otining grphene nnorions y omining preEstrutured suE strtes nd n dequte growth methodF he gol is to understnd the wys of opening nd gps y nnostruturing in view of lter tiloring nd gp openingF e hve studied ll these systems y eiD w nd iwD whih re desried in hpter PF e hve used two pprohes to open nd gps in grpheneX the growth on viinl metlli sustrtes @known for the tlyti deoupling of ethylene to promote grphene growthA nd on nneled lithogrphi trenhes on igF he metlli sustrtes used for the (rst pproh re viinl sr nd urved multiviinl t exhiiting di'erent viinlitiesF foth on iridium nd pltinumD we were le to otin gpped eletroni struture due to periodi (nite potentil rrier on ontinuous grphene lyerF he omined results of the viinl sr nd multiviinl t llowed us to explore the ftors ontriuting to the nd gp opening experimentlly nd y modelingF e hve in prtiulr studied the potentil strength s funtion of the periodi nnostrutureD the viinlity type nd the stepEedge typeF hese results re desried in hpters Q nd RF yn our seond pprohD we studied grphene grown on nneled lithogrphed trenhes on ig @or sidewllsAF he growth ws performed y our ollortors in qeorgi ehF wotivted y the oservtion in ei of nd gp with unknown tomi originD we performed thorough struturl study to understnd the unexplored ronEron distne a ≈ 1.42 ÅF he hexgonl network hs motif of two toms per ell @eh tom orresponding to inequivlent sulttie e @yellowA or f @greenA in (gF IFIA nd lttie prmeter of PFRT ÅF he reiprol lttie is lso hexgonl rotted QH • with respet to the rel spe lttieF he lttie vetors nd the reiprolE lttie vetors re given yX

a = a 2 (3, √ 3) D b = a 2 (3, - √ 3) @IFIA a * = 2π 3a (1, √ 3) D b * = 2π 3a (1, - √ 3) @IFPA
he nd struture of grphene y tightEinding isX

E ± (k) = ±t 3 + f (k) -t f (k) @IFQA f (k) = 2 cos √ 3k y a + 4 cos √ 3 2 k y a cos √ 3 2 k x a @IFRA
where t is the hopping etween di'erent sultties @(rst neighoursA nd t is the hopping in the sme sulttie @seond neighoursAF he plus nd minus suindex orrespond to the π nd π * nds respetivelyF he dispersion reltion is shown in (gF IFP for hopping prmeters t = 2.7eV nd t = 0.2tF hue to its hrteristi IQ IR CHAPTER 1. FUNDAMENTALS OF GRAPHENE NANORIBBONS ).

tomi strutureD the π nd π * nds touh eh other t the K nd K points round the permi level @E f AD mking of grphene zero gp semiEmetlF sn the viinity of the K pointsD the dispersion reltion n e pproximted yX E ± (k) = ±hv f k @IFSA whih renders expliit the liner dispersion of grpheneD where v f 1 × 10 6 mGs is the permi veloityF hen one sptil dimension of grphene is redued to nnometri sizeD grphene nnorions re otinedF sdel rions with simple edge orienttion nd termintionD of extremely nrrow widthD nd isolted from ny sustrte in)uene hve een extenE sively seeked forF he edge termintion is de(ned y the orienttion of the rion with respet to the grphene lttieF hue to their high symmetryD the most studied grphene nnorions re those with zigzg nd rmhir edgesF igzg rions hve honeyE om network oriented in suh wy tht the edge is mde of the tringulr edges of the hexgons @(gF IFQEtop leftAF ermhir rions re oriented t QH • @or equivlently t WH • A from the zigzg orienttionF sn this seD the edge is mde of hexgonl sides @(gF IFQEtop rightAF ell other ordered orienttions re hirlF irly tightEinding lultions IPD IQ hve shown tht the nd struture of nrrow rions depends on their orienttionF pei(llyD in these lultionsD zigzg rions re lwys metlli @(gF IFQA nd rmhir rions present n lterntion of metlli nd gpped eletroni strutures depending on the widthF hen presentD the gp sles inversely with the rion9s widthF sn (gF IFQD the lulted nds re projeted either long the diretion de(ned y the lttie prmeter a @prllel to the rmhir diretionA or long z @prllel to the zigzg diretionA @(gF IFQEottomAF ith this onventionD π = k orresponds to the kEpoint where the frillouin zone edge is rehed long a * or z * reiprol vetorsD respetively IP @(gF IFQEottomAF he width is hrterized y x ron dimer linesD whih re di'erent for rmhir or zigzg rionsD s presented in (gF IFQEtopF he eletroni strutures for di'erent vlues of x re shown in (gF IFQF ixpliitlyD the rion is metlli for N = 3M -1D where M is n integerD nd presents gp otherwiseF wore reent initio lultions hve on(rmed the presene of signi(nt nd gp in ll I nm to ∼ R nm wide rmhir rionsD with gp vlue tht dereses with width nd osilltes with x ISD IU!PI @(gF IFQAF he sitution is qulittively di'erent for zigzg rionsD for whih tightEinding lultions (nd )t nd t zero energy @highlighted y the ox in (gF IFQA tht orresponds to sttes tht re loted t the edge of the rionsF hese edge sttes produe pek in the hy t the permi levelD enhning the temperture dependene of their prmgneti suseptiilityF sn the se of zigzg rionsD (rstEpriniple lE ultions hve shown tht the )t nd t zero energy found in simple tightEinding lultions is unstle reltive to spin splittingF wgneti ordering is predited on the edges of nrrow zigzg rionsD with longErnge ferromgneti polriztion long eh he reported moilities for this type of synthesis using timeEresolved rz speE trosopy for rions dispersed in the liquid phse re within the rnge 150-15000 cm 2 (V 1.4. TRANSPORT GAP PU spetrosopy @siAF hotoemission n determine the nd gp when the permi enE ergy is pled in the ondution ndF ytherwiseD when the permi level is somewhere within the nd gpD photoemission gives minimum vlue of the gpF hotoemission requires homogeneous res for suh determintionsF hs the dvntge of eing n tomi sle mesurementD ut does not proe the rion s whole s is done in trnsport mesurementsF rnsport mesurements in generl nnot distinguish eE tween vnishing ondutne due to true nd gp @iFeF no sttes villeA nd moility gp due to loliztion e'ets @iFeF presene of nonEonduting sttesAF ery detiled lowEtemperture trnsport dt nlysis is required for thtF sn oth sesD vnishing ondutne t lowEis voltge nd strong ondutne inrese with gte nd is voltges @iFeF lrge urrent onGo' rtiosA re expetedD nd these e'ets depend strongly on tempertureF sn most of the rionsD nd espeilly in lithogrphillyEptterned nnorionsD defets ssoited with edge roughness nd the inhomogeneous potentil reted y impurities rete series of interonneting quntum dots @(gF IFIPA UID UQ!USF he overll e'et of this potentil is the onset of trnsport gp9D due to loliztion e'ets nd goulom hrge lokingF his mens tht the ondutne drops to zero round the hrgeEneutrlity point even in the sene of true nd gpF pigF IFIP shows the ondutne s funtion of is for grphene nnorion exhiiting trnsport gp in the region of gte voltge ∆V g F hen the gpped region is nlyzed more refully @see the insetAD smll resonnt ondutne peks n e seenF his gp is often inversely proportionl to the width @(gF IFIPA QID UID UPD UTD whih mkes it more di0ult to unrvel from true nd gpF he most reent pulished gp vluesD onGo' rtiosD resistnes nd moilities for rions prepred with di'erent proesses re listed in les IFI nd IFPF he listed gps re trnsport gps @mostly t ryogeni tempertureAD unless otherwise spei(edF Notes: RT (LT, respectively) refers to room temperature (cryogenic, respectively) measurements. Epi refers to graphene grown on SiC sidewalls as it will be discussed in chapter 5. Chapter 2

Experimental techniques

he struturl nd eletroni nlysis on surfe siene in generl is etter performed y using set of omplementry tehniquesF sn our seD we hve studied the eletron properties of grphene nnorions y engleEesolved hotoemission petrosopy @eiAD nning unneling wirosopy nd petrosopy @wGAD nning rnsmission iletron wirosopy @iwA nd iletron inergy voss petrosopy @iivAF hese tehniques were performed t the niversité ris ud @vortoire de hysique des olidesAD t the niversité de vorrine @snstitut ten vmourA nd t the oleil ynhrotron @urfe vortory nd the gssiopée femlineAF sn the followingD s will desrie these tehniquesF 2.1 Scanning tunneling microscopy he nning unneling wirosope @wA is mirosope with the ility to resolve the tomi nd eletroni struture of onduting surfes with resolution of the order of the ÅF he w rehes suh resolution y snning shrp tip on top of the smple to e studiedF hen potentil is pplied etween the tip nd the surfeD eletrons n )ow etween them without ontt euse of the quntum tunnel e'etD whih is the sis of the operting priniple in wF he min element in n w is the tip @typilly or tEsrA tthed to three xis piezodrive @xD y nd z piezoeletri trnsduersAF es the tip is positioned lose to the smpleD typilly few he energy digrm of the system is onstituted y the smple nd the tip with the vuum in etween is shown in (gF PFIF he vuum is potentil rrier @U (z) = φA tht eletrons lssilly nnot penetrte if their energy is lower thn the potentil rrier @E < U (z)AF roweverD in quntum systemD the wvefuntion ψ(z) stis(es the hrödinger equtionX

- h2 2m
d 2 dz 2 ψ(z) + U (z)ψ(z) = Eψ(z) @PFIA
nd hs solution in the lssilly foridden region of the form ψ(z) = ψ(0)e -κz where κ = 2m(U -E)/h is the wve vetor tht desries the deying ehvior s eletrons penetrte through the rrierF he totl tunneling urrent through the rrier depends on ll the sttes etween the permi level of the smple nd the is

pplied @E F nd E F -eV A sX 2.1. SCANNING TUNNELING MICROSCOPY QQ I ∝ E F En=E F -eV |ψ n (0)| 2 e -2κz
@PFPA sf eV is smll enough so tht the density of sttes does not vry signi(ntly with itD the urrent I n e rewritten s funtion of the lol density of sttes s followingX

ρ s (z, E) ≡ 1 E En=E- |ψ n (z)| 2 @PFQA I ∝ eV ρ s e -2κz
@PFRA prom this equtionD the exponentil sensitivity of the tunneling urrent with respet to the tipEsurfe distne is highlightedD whih gives the resolution to this mirosopeF here re two types of snning mode for n wD s shown on (gF PFPX IA gonstnt height E the tip is kept t onstnt height setpoint vlue while the surfe is snned nd the hnges in tunneling the urrent re reordedF PA gonstnt urrent E the urrent etween the tip nd the surfe is kept onstnt while the hnge in the height is reordedF e feedk look keeps the tunneling urrent onstnt s it moves over the surfeF his is the most ommon modeF o further quire informtion on the lol density of sttes of the smpleD it is possile to perform snning tunneling spetrosopyF es the eletrons )ow etween the QR CHAPTER 2. EXPERIMENTAL TECHNIQUES tip nd the surfeD there is onvolution of the lol density of sttes of the tip nd the smpleF sf the tip hs onstnt density of sttesD the urrent )ow gives informtion out the density of the sttes of the smple @iqF QFRAF o do thisD feedk of the onstnt urrent mode is interrupted t given sptil lotionD so the tipEsmple distne z is kept onstntF hen the tunneling urrent is snned s funtion of the pplied is @dsGdAD whih is proportionl to the smple lol density of sttes @from iqF QFRD dI/dV ∝ ρ s AF he typil urves for metlli nd semionduting mteril re shown on (gF PFQF w n e performed in vriety of environments nd working temperturesF he experiments done t the snstitut ten vmour were under vuumD t D liquidEN 2 nd He temperturesD llowing lso to perform mesurements t ryogeni temE perturesF ixperiments t the urfe vortory in oleil ynhrotron were performed under vuum t F 2.2 Scanning transmission electron microscopy sn nning rnsmission iletron wirosopy @iwAD nrrow foused em of eletrons @∼ I E IH ÅA is snned through di'erent positions of thin smple @∼ few hundred nm thikAF e detetor t the lower prt of the mirosope olumn detets the trnsmitted eletrons @(gF PFRAF en dvntge of iw over iw is tht the imge is formed without imging lensesD therefore the resolution is only limited y the eletron em sizeD llowing the study of the tomi order of the eletron density of the smple IHTF hi'erent trnsmitted eletrons n e olleted ording to the need of the studyY we will minly disuss three di'erent modesD the rightE(eld @fpA modeD nd two nnulr drk (eld @ehpA modes @high ngulr nnulr drk (eldEreehp nd low ngulr nnulr drk (eldEveehpAF fp imges re otined y positioning detetor tht interepts the diret trnsmitted emD while the veehp nd reehp re otined y using nnulr detetors tht surround the fp detetor @(gF PFRAF he veehp mode llows to otin imges with high ontrsted intensity suited for light elementsF yn the other hndD the reehp mode is sensitive to the tomi numer of hevy elements @E ontrstA IHTD IHV!IIHF ine the ehp detets sttered eletrons nd the fp mode detets the diretEem eletronsD they re omplementry modesF pigF PFR shows shemti for the three modes @pnel A nd n exmple of mesuring the sme ojet with the three di'erent modes @pnels EdAF iw llows lso to perform eletron energyEloss spetrosopyD whih gives inforE mtion out the hemistry nd eletroni struture of the smple y olleting nd QT CHAPTER 2. EXPERIMENTAL TECHNIQUES nlyzing their energy distriutionF sn this wy it is possile to otin informtion out the ondingGvlene stteD nerestEneighor tomi strutureD dieletri responseD freeEeletron densityD ndgp nd even the thikness IHTF he sptil resolution nd sensiility of iiv is of the order of single tomF en iiv spetr for (tive mteril is presented in (gF PFSD showing the most ommon feturesF he most intense feture is the zeroEloss pekF lsmon fetures pper ner to it nd then the ioniztion edges of di'erent hemil elements re oE servedF he spetr is divided into low nd high energy loss regionsF he low energy loss region provides informtion on the wekly ounded ondution nd vlene eletronsD while the highEloss region is relted to the tightly ounded or oreEshell eletrons IHTF ine this work fouses on the nlysis of grpheneD the iiv spetr here will fous on the ron vEedgeF por this thesisD mesurements were rried out t the vortoire de hysique des olides in ollortion with elexndre qloterF he iw mesurements @fpD ehp nd iivA were performed on iw xsyx PHHD where the spheril errtions of the ojetive lens re orreted up to 5 th order nd the nyon type gpiq ws used with n eletron em energy of TH ke with sptil resolution of ∼ I ÅF 2.3. ANGLE RESOLVED PHOTOEMISSION SPECTROSCOPY QU 2.3 Angle resolved photoemission spectroscopy engle esolved hotoemission petrosopy @eiA is tehnique tht llows oE tining informtion out the eletroni sttes of mterilD whih re fundmentl to understnd their propertiesF he spei(ity of this tehnique is to llow the onstruE tion of n energy versus momentum mp @i@kAA y nlyzing the eletrons oming from smpleF he working priniple to ejet eletrons from the smple is the photoeletri e'etD tht desries the energy trnsfer from photon to n eletron of mterilF hen the photon energy @hνA llows the eletron to overome the energy rrier to espe the mteril @workfuntion ΦA nd its own inding energy to the system @E b AD y the priniple of energy onservtionD the kineti energy of the outgoing eletron is desried yX

E kin = hν -Φ -E b @PFSA
his mens tht y mesuring the kineti energy of the outgoing eletronD it is possile to retrieve the inding energy @E b A of the eletron inside the mterilF sn order to onstrut the i@kA mpD it is neessry to determine the momentum of the eletronsF he eletrons re ejeted t ertin θ ngle @(gF PFTAF he mesurement of the emission ngle θ nd the reltionship etween kineti energy nd momentum llows to retrieve the omponent of the momentum prllel to the surfeF ine the ejeted eletrons pss through potentil rrier s they exit the surfeD the perpendiulr omponent of the momentum is not onservedF roweverD the prllel momentum is onserved nd is de(ned yX

p || = hk || = p sin θ = √ 2mE kin • sin θ @PFTA
where m is the mss of the eletron IIID IIQF es the prllel momentum is onserved when the eletron exits the solidD y mesuring it in the vuum is possile to otin the momentum in the initil stteF hereforeD y mesuring oth the energy nd the emission ngleD it is possile to reover the i@kA dispersionF pigF PFT shows semiE spheril nlyzer olleting the outgoing eletrons tht re (ltered y their kineti energy nd emission ngle nd re lter olleted on ggh merF he i@kA for eu@IIIA surfe mesured in this wy is shown on (gF PFTF e useful wy to represent the i@kA nd dispersion is vi the inergy histriution gurves @ihgAD where the olorEode is repled y the numeril intensity @(gF PFTAF e wide rnge of emission ngles n e explored y hnging the ngulr position of the smple with respet to the semiEspheril nlyzerF st is therefore possile to explore lrge regions of the kEspe @the k x nd k y prllel omponentsA vsF inding energy @(gF PFUAF his type of onstrution llows to visulize nd follow the nd struture long di'erent rystllogrphi orienttionsF gonstnt energy uts of the

)
his hpter is dedited to the modi(tion of the eletroni properties of grphene y nnostruturing of the sustrteF e will indue the struturtion in grphene y using viinl surfe tht n promote grphene growthF sr@QQPA is stle viinl surfe with smll terres of IFPS nmF he growth study on sr@QQPA ws plnned eE fore the (rst pulition on the topi ppered IIRF he work done y rut et lF ws then pulished t the time where our experimentl work egnD therefore we used these reported results on sr@QQPAD long with the wellEknown growth of grphene on sr@IIIAD s sis nd omprison point for the lter growth on sr@QQPA in our hmerF s hve pplied two di'erent growth methodsD nmely temperture progrmmed growth nd hemil vpor depositionF qrowth y those tehniques on sr@QQPA indues periodi potentil on grpheneD s seen y the presene of gps in the nd struture proed y eiF efter pplying the hirEhmiltonin modelD we determined tht surfe potentil is indued in grphene y the nnostruturingF e (nlly modi(ed the periE odi potentil y gu interltionD otining n rry of nE nd pEdoped nnorions on ontinuous lyerF 3.1 Growth and structure of Gr on Ir(332) everl nole metls hve een used s sustrtes for grphene growth due to their tE lyti propertiesD whih ontriute to the deomposition of hydroronsF sn prtiulrD grphene growth n e hieved on sr@IIIAF rereD grphene grows deoupled from the RI sustrte @qrEsr distne is QFREQFV ÅD whih is lrger thn the interlyer distne in grphiteAF sn this wyD there is low intertion etween grphene nd srD llowing study of grphene9s eletroni properties in qusiEfree stnding regime IISD IITF pigF QFIE shows viih pttern of grphene on sr@IIIAF here is domin ligned with the sustrte @ zero rottionD tht we will nme HAD dditionllyD other domins pper where grphene hs twisted ngle with respet to iridiumF foth the quntity nd qulity of the grphene depends on the prtiulr growth nd onditionsD nd sevE erl grphene rottionl domins with respet to the sustrte n oexist IIU!IPIF he w imges on (gF QFIEd show three di'erent oexisting domins tht extend even through step edgesF homins re seprted y defetive oundries where ron toms form heptgons nd pentgons or wrinklesF potentil rrier on oth edges ting s potentil well for eletrons in grphene @(g QFPAF he e'ets of suh potentil should hve diret impt on the eletroni nd struture of grpheneF e hve used viinl surfe s templte for grphene growth with two di'erent methodsX emperture rogrmmed qrowth @qA nd ghemil por heposition @ghAD whih n form single domins on metlli surfes IIT!IIWD IPI!IQHF hese growth results were otined t the snstitut ten vmour in xnyD in ollortion with wF iot nd hF wlterreF sn the following s detil the growth studies to deterE mine the optiml preprtion tht ws then extensively studied y ei t oleil ynhrotronF 3.1.1 Ir (332) substrate preparation he pristine sr@QQPA surfe onsists of sr@IIIA terres of IFPS nm tht extend long the 101 diretion nd re periodi in the 121 diretion @(gF QFQAF o len the sr@QQPA rystlD yles of sputtering followed y nneling hve een performedF en intermeE dite nneling under oxygen tmosphere n e performed to eliminte the ron impurities tht di'use to the surfe s produt of the nneling IIVDIPQF e found howeverD tht high qulity surfe ould e hieved without this intermedite stepF he sputtering ws performed t with 1ke Ar + )ux t 2 × 10 -6 mr pressureF he sputtering time ws IH min t three di'erent positions @enter nd edges of the smpleAF e susequent nneling y eletron omrdment ws performed t TSH • g for IS min nd then slowly ooled down for QS min to t rte of PH ±1 • gGminF efter repeted yles of sputteringGnnelingD viih ptterns were heked until otining len surfeD s shown on (gF QFQF he len surfe is hrterized y lmost no kground intensity nd de(ned sr spotsF he surfe is omposed of two types of sr spotsX the @1x1A spots of sr due to the hexgonl iridium periodiity @mrked in redAD nd splitting of these spots due to the periodi nture of the viinl surfe long the 121 periodi diretion @G per mrked in lueAF king the distne etween the sr @1x1A spots s refereneD the terre size lulted y viih is L = 2π/G per = 1.8 ±0.2 nmF es seond qulity hekD the surfe ws lter studied y w @(gF QFQAF et (rst glneD we oserve tht the terres hve n homogeneous distriution nd stright edgesF yn the other hndD some present prtiles pper due to impuritiesD s the imge ws tken t IQIF o otin the terre size from the w imgesD two methods were employedX the pst pourier rnsform @ppA of w imges nd diret nlysis of the erre idth histriution @hAF efter the pp ws otinedD pro(le ws tred through the entrl spot nd the two seondry mximF he terre size ws otined y trnsforming the q distne in the reiprol spe into its orresponding distne in the rel spe @L = 2π/GAF ith this methodD the reovered periodiity is

L = 1.2 ±0.
2 nmF por the h methodD the w imge ws nlyzed pixelEyEpixel emperture rogrmmed qrowth @qAon sr@IIIA hs lredy lowed the growth of seprte grphene )kesD eing thus promising for our gol IIWDIPSDIPWDIQPF he q tehnique onsists of depositing hydroron onto the tlyst surfe t F yne the deposition is hievedD the surfe is heted ove THH • g to promote the deomE position of the hydroronF he hydrogen is evuted through the r pumping systemD while the remining ron is moile t the surfe of the metlF he energy provided y the temperture is used to nuleteD grow ndGor merge islnds of grpheneF ine the ron di'usion towrds the sr ulk is insigni(nt IQQD y nneling to the systemD only grphene formtion is promotedF es grphene forms lyer on top of the metlD the surfe of the metl is overed when the (rst monolyer is ompleteD preventing ny further tlyti intertion etween the hydroron nd the metlli sustrteF he formtion of grphene is thus selfE limiting proess to single lyerF sf the sustrte is ooled fterwrdsD monoEdomin islnd is fvored in grpheneF sn prinipleD severl q yles re neessry to reh the full overge of the surfe IQPD lthough omplete monolyer is not neessry for nnorion rry growthF sn our experimentD the preferred hydroron for q is ethylene @C 2 H 4 AD s it is the simplestD most ommon gsD nd our ollortors t the snstitut ten vmour in xny hve the expertise of growing grphene with itF sts deposition is hieved with lek vlveF foth the prtil pressure @P C 2 H 4 A nd the exposure time @t exp A re key prmetersF he dosge is mesured in vngmuir vD orresponding to the equivE lent exposure of 10 -6 torr for one seondF he sr@QQPA surfe ws lter nneled to di'erent T tpg tempertures to stimulte the ronEhydrogen ond reking nd the grphene formtionF pinllyD the surfe is ooled down to t ontrolled rte of PP ±1 • gGminF he prmeters for P C 2 H 4 nd t exp vry from 1 × 10 -8 to 2.5 × 10 -6 mr nd from I to TH minutes respetivelyF he detils of ll the preprtions re presented in le eFI on the eppendixF ith the ojetive of growing individul nnorions on the terres of sr@QQPAD we strted with n exposure ten times lower thn the optiml for fully overing sr@IIIAF 3.1. GROWTH AND STRUCTURE OF GR ON IR(332)

RU he systemti study of grphene formtion y q s funtion of the nneling temperture T tpg nd the exposure is presented in (gF QFRF he initil optimiztion of the growth onsisted of performing one q yle t vrious exposures nd tempertures until grphene signl ppered in viih @red squreAF he pperne of grphene llowed to (x the q temperture t ∼ VHH • gD whih flls in the rnge for the growth on sr@IIIAF yne the growth temperture ws setD series of q yles were performed without smple lening to inrese the overge of the surfe y umultion until rehing the optiml preprtion @green strAF sn (gF QFRD the irleD tringle nd str represent three di'erent smples grown y severl onseutive q yles fter the lowest exposure onesF ivery pperne of the sme symol indites n umulted q yle on the sme smpleF viih ws performed on every smpleD so we n identify the growth onditions leding to grphene formtion @ornge dotted lineAF

[1 V, 1.1 nA],[1 V, 0.5 nA], [1 V, 0.6 nA], [1 V, 0.6 nA], [1 V, 0.5 nA]).
viih ws performed fter q yles to roughly hrterize the smple qulityF pigF QFS orresponds to the initil stges of grphene growth @red squre in (gF QFRA t 6.75 v nd VIP • gF he viih shows tht the surfe hs een modi(ed with respet to the len sr@QQPA surfeF he splitting of the @1x1A spots hrteristi of the len sr@QQPA sufe dissperD inditing tht the regulr periodiity of the steps hs een lostF elsoD new spots pper ssoited to grphene whih is ligned with respet to the iridium sustrte @H rottionAF ix dditionl fetures pper round the grphene spot @insetA resulting from the moiré pttern due to the di'erent lttie prmeters of grphene nd iridiumD even if they hve the sme rystllogrphi orienttionF elthough mny fetures of the surfe were understood thnks to viihD it does not provide informtion out the preise morphology of the surfeF rene we performed w to investigte the initil stges of grphene growth @(gF QFSAF st n e oserved tht stepEunhing proess tkes pleF he pristine @IIIA steps olese nd form step unhing in vrious degrees of ompletion @prtil or fullAD shown y the rrows on (gF QFSF yne wider terres re formed due to the full step unhingD the (rst pthes of grphene pper on the @IIIA stepsF he step unhing suppresses the initil periodiity of the sr@QQPA surfeD explining the loss of the splitting on the viih spots when grphene is grownF edditionllyD the roundElike islnds re most likely ridesD whih hve een oserved efore y rut et lF IIRF hen inresing the e'etive dosgeD the surfe is progressively overedD s shown in (gF QFTD whih orresponds minly to the vertil points in (gF QFRF sn (gF QFTD the red tringles orrespond to one q yleD while the lue irles orrespond to two or more ylesF qrphene is (rst seen t dosges round U vD s shown y the ornge lineF righer grphene overge is otined on severl q ylesF he viih intensity does not hnge s the overge is inresedD so the qunti(tion of the overge is sed 3.1. GROWTH AND STRUCTURE OF GR ON IR(332) RW on w imges t lrge sleF fesides showing the inrese of grpheneD w imges lso show the stiliztion of lrge terres @orngeA nd step unhing res @rownA in n ordered mnnerF he optiml preprtion is presented in (gF QFUF he treted w imge is shown in pnel @AF foth the terre nd the step unhing rrys re developedF he verge terre width is now 4.4 ±1.4 nm s lulted from the pp of the w imgesF qrphene res on the @IIIA steps re highlighted in greenD s

shown on (gF QFUF he inset shows the tomi resolution of the grphene networkD whih is rotted H • with respet to srF qrphene is identi(ed y D s shown in (gF QFVF he spetrum on (gF QFV performed on the @IIIA terre @green point in pnel @AAD is very similr to the one on qrGsr@IIIAF sn prtiulrD it revels three fetures spei( to the qrGsr@IIIA system IPUD IPVD IQRD s shown in pnel @A IQRF he (rst feture ssoited to the I surfe stte hs mxim etween -0.25 nd -0.5 @F 1 AF he seond feture is ssoited to unoupied sttes nd hs mxim round +0.6 @F 2 AF he third feture is the dir point @E Ir D A round +0.25 D omprle the +0.2 in pnel @AD inditing pEdoping on the eletroni struture of grphene on the terreF he doping is slightly di'erent to the one on qrGsr@IIIA @+0.2 eAD ut it is not surprisingD s experimentl nd theoretil reported vlues for the pEdoping vry from 0.1 to 0.34 IPPD IPTD IQHD IQPD IQSD IQTF es shown y (gF QFUD grphene does not oupy the full terre lengthD whih n only e hieved y pprohing full overgeD ut it is not suitle for disontinuous grphene nnorions growthF st seems di0ult to otin disontinuous grphene on the @IIIA terresD s w revels tht grphene extends from the stepEunhing to the terres in ontinuous wyF pigF QFV shows the ontinuity thnks to the tomi resolutionF yur interprettion is tht the oserved ontinuity is due to the growth mehnismD where the steps of the stepEunhing t s nuletion enters for grphene growth tht then extends towrds the @IIIA terresF pigF QFW shows n intermedite stge of grphene growth where the step unhing res @orngeA fully disply periodiity similr to the moiré of grpheneF et the sme timeD only frtion of the terres re overed y overgrown grphene @greenAD while the mjority of the @IIIA terres re re iridium @rownAF st seems then possile to otin disontinuous network of grphene nnorions loted t the step unhing regions in this stge of growthF pigF QFW shows our model for this intermedite stgeX qrphene is present on the step unhing re nd slightly overgrown on the terreD produing network of disontinuous grphene nnorionsF his sptil disontinuity ould e seen y grphene s n in(nite potentil rrier t oth sides of eh nnorionD whih is n interesting perspetive to e explored in the futureF he ghemil por heposition tehnique @ghA onsists of exposing hot tlyti surfe to hydroron speiesF gontrry to the q tehniqueD the dissoition of the moleule nd grphene formtion our in single stepF he therml energy promotes the nuletionD growth ndGor merging of islndsF hepending on the ooling dynmisD grphene n form monoE or multiE rottionl domins or even wrinkles IIU!IPID IPTF es qD gh is selfElimiting proessD so one grphene monolyer is formedD no tive sites re ville to promote further grphene growth IPWF por gh preprtion of grphene on sr@QQPAD we hose ethylene @C 2 H 4 AF he suE strte is nneled to given temperture @T cvd A nd gs prtil pressure of ethylene @P C 2 H 4 A is inserted through lek vlveF he surfe is kept hot for n tive time @t act AD then ooled down to room temperture t ontrolled rte of 60 ±1 • gGminF gontrry to qD viih eme tool to explore the evolution of the grphene strutureD sine the overge is inherently lrger y ghF his is the result of dissoition nd growth ourring ontinuously t the hot surfeF e thus optimized the preprtion y mxiE mizing the intensity nd shrpness of the grphene viih spots y vrying the dosge nd the tempertureF e then performed w on the optiml preprtionF hereforeD the qulity of the smple n e (rst ssessed y viih nd then nlyzed y w one the optiml viih pttern hs een rehedF pigF QFIH shows the viihs of the di'erent preprtions s funtion of the dosge nd the nneling tempertureF he detils of ll the preprtions re presented in le eFP on the eppendixF yur (rst preprtion ws hosen to e out hlf of the dosge for gh on sr@IIIA nd 150 • g elow the typil temperture IQIF his is indited y the lue squre on (gF QFIH nd orresponds to T cvd = 659 • g nd dosge of 22.5 ± 0.1 vF nel @A shows viih with n inoming eletron em of 232 e with hrteristi sr @1x1A spots nd di'use kgroundD ut no tres of grpheneF husD we hnged the tempertureD s it is the key prmeter to indue the moleulr dissoition nd hene the grphene formtionF he seond preprtion ws performed t slightly higher temperture of T cvd = 713 • g nd dosge of 34±2 v @(gF QFIHAF en emerging struture is ppreited round the sr@IIIA spots due to grphene t 66 eF 3.1. GROWTH AND STRUCTURE OF GR ON IR(332) SQ qrphene spots re visile now ligned with the sr@IIIA spots @H rottionAF e di'use r is lso visileD due to multiEdomin grpheneF pon inresing the temperture to 800 • g while keeping the dosge t 34 ± 2 v @(gF QFIHAD the viih fetures eome shrperD nd we distinguish the H spotD plus two domins round PS • nd QS • @further lled PS nd QSAF he fint intensity from the multiEdomin grphene r is still presentF pinllyD the temperture ws set to 800 • gD while inresing the dosge to the optimum vlue of 67.5 ± 0.1 vD in greement with tht for sr@IIIA @(gF QFIHdAF he detils of the viih in @dA re given in (gF QFIIF he viih of the optiml preprtion is shown in (gF QFIIF here re four di'erent kinds of grphene viih spots ssoited to di'erent rottionl dominsF he (rst kind of spots hve the sme orienttion thn sr@IIIA spots @0 • rottion etween the lyers or HA shown y the white rrow on viih lso reports on the struturl periodiity of the sustrteF he sr spot is splittedD s indited y the red rrows in (gF QFII due to superperiodiity on the sustrte L = 7.1 ±1.5 nmF es seen in (gF QFIPD the surfe is omposed of terres nd step unhing res @mrked y the legends nd fA giving rise to the superpeE riodiity otined y viihF he size of the superperiodiity lulted y pp of this w imge is L = 6.8 ± 0.6 nmD s shown y (gF QFIPF he terre width distriution method performs pixelEyEpixel nlysis perpendiulrly to the steps on the w imgesD in order to detet the step edges nd determine the terre sizeF he otined terre size is T = 3.5 ± 0.5 nm @(gF QFIPAD roughly hlf of tht otined y viih nd ppF ine the superperiodiity is omprised of the terre C stepEunhing nd the lulted terre size is hlf of the superperiodiity sizeD this would result in the step unhing size eing roughly equl to the step unhing sizeF w lso shows tht grphene ompletely overs the sr@QQPAD s oserved y the ontinuous moiré pttern on (gF QFIPF hespite this ontinuityD the niely periodi sustrte @with muh higher qulity thn tht otined y qAD indues periodi potentil tht my hve n impt on the eletroni properties of grphene nd open nd gpsD s is the se for other nnostrutured systems IIPD IQU!IQWF he modi(E tion of the properties depends on the potentil strength t the step edgesF he e'et n hnge from totl on(nement in disontinuous grphene nnoriE ons due to in(nite potentil rriers @(gFQFIQAD or to minigp opening in the se of ontinuous grphene feeling periodi struture with (nite potentil rriers t the oundries etween terres nd step unhing regions @(gFQFIQAF ei llows to 3.1. GROWTH AND STRUCTURE OF GR ON IR(332) SS quntify the potentil strength nd its e'ets on the eletroni nd strutureD s we will see in the next setionF 3.1.4 Cu intercalation on Gr/Ir(332) e wy to further ontrol the potentil rrier t the step edges is y deorting the steps of the sustrte with dtomsF st is neessry to interlte toms elow the grphene lyerF snterltion of metls on grphene hs een suessful wy of investigting the metlEgrphene reltionship nd the hnges in ommensurility IQTDIRHDIRID hrge trnsfer IQHD IQTD IRPD IRQD eletroni nd struture IQHD IQTD IRHD IRRD IRSD phonon modes IRSD IRTD spinEpolrized e'ets IRID mong othersF sn the frmework of the modi(tion of the surfe potentil to otin higher on(nementD we onsider the interltion of gu on qrGsr@QQPA y following the proedure developed for qrGsr@IIIA IQIF Intercalation method gopper dtoms n e interlted on grphene on sr@IIIA IQIF pigF QFIR shows the interltion s funtion of the gu overgeF he initil qrGsr@IIIA surfe is represented in stge 0 @(gF QFIRAF et stge 1D gu interltes in preferentil sites suh s the step edges nd osionlly in the terresF purther interltion @stge 2A results in the growth of the lredy interlted sitesF hen pprohing omplete gu monolyer elow the grpheneD gu ontinues to e interlted homogeneously elow the grphene nd lso strts to form islnds on top of grpheneD s presented in stge 3F nels @A@A nd @dA show the w imges of stges 1D 2 nd 3 respetivelyD where the insets highlight in yellow the res where the moiré struture indites tht gu hs een interltedF fy tking into ount this mehnismD we expet tht gu deortes esily the step edges of viinl surfeD possily inresing the potentil felt y grphene thereF e hve performed two di'erent interltions of 0.45 wv nd 0.9 wv of gu on the optiml qrGsr@QQPA otined y gh @(gF QFIPAF he interltion is hieved y gu evportion from unudsen ell t VSH • g for RS minF @in the se of 0.45 wv overgeAF followed y n nneling t SHH • g for RS min t se pressure ∼ 1 -2 × 10 -9 mr t rte of HFI ÅGminF hese prmeters re the usul ones for qrGsr@IIIA on the sme preprtion hmer IQIF he overge of 0.9 wv of gu is rehed y dding 0.45 wv of gu on the previously interlted smpleF efter eh interltionD the smple ST CHAPTER 3. ELECTRONIC STRUCTURE TAILORING ON IR(332) is ooled down to nd wG is performed to oserve the hnges in the tomi nd eletroni struture of the surfeF Near monolayer intercalation on Gr/Ir(332) he interltion of 0.9 wv is presented in (gF QFISF he surfe efore interltion is shown on pnel @A s refereneD while the interlted surfe is shown on pnel @AF he tomilly resolved w imge shows the H rottion of grphene with respet to iridium @inset in (gF QFISAF he interltion of gu is visile through the enhnement of the moiré on the terresD s shown y the lue rhomus unit ellF he moiré is not visile on the step unhingD proly euse it nnot e developed ompletely s the width of the step unhing is slightly elow the size of the unit ell @2.52 nmAF roweverD even if the enhned moiré is not developed on the step unhingD gu is lso interlted thereD s indited y snning tunneling spetrosopy @(gF QFISAF foth spetr on the terres nd on the step unhing re very similrD with the dir point @E Cu D A t ∼ -0.6 D hrteristi of nEdoping nd of gu interltion nd very di'erent from the nonEinterlted spetrF his on(rms tht we hve fully interlted the gu under the grphene lyerD nd eletroni properties re therefore homogeneousF vower overge interltion my give rise to di'erent ehvior in terres nd step unhingD s we will see in the followingF Submonolayer intercalation on Gr/Ir(332) he interltion of 0.45 wv gu on qrGsr@QQPA is shown on (gF QFITF pigF QFIT shows the terreGstepEunhing strutureD lso present in the initil qrGsr@QQPA surE fe @(gF QFIPAF he regions where gu is interlted ould e usully identi(ed y the enhnement of the moiré IQI when the moiré is reltively lrge @ few nmAF roweverD due to the rottion of QH • etween grphene nd iridium @inset (gF QFITAD the (2x2) Gr unit ell of the moiré @0.492 nmA is not visile on the terres or on the step unhingF e performed snning tunneling spetrosopy on oth regions @(gF QFITA to identify where gu is interltedF he urve on the terre @(gF QFITA shows the hrteristi ehvior of qrGsr@QPPAD with stte t ∼ -0.25 D mrked with the lue rrow nd new dir point @E Ir D A t ∼ +0.1 D inditing slight pEdopingF yn the other hndD the urve on the stepEunhing @orngeA shows shift of the dir point @E Cu D A to ∼ -0.6 D showing hnge from pE to nEdopingD typil of qrGguGsr surfe due to hnge in the work funtion of the surfe IQHD IRUD IRVF o proe suh ehvior in lrge sleD we performed ondutne mp t -0.6 D shown in (gF QFITF he right zones orrespond to the terres with high intensityD while the drk res orrespond , typical of the p-doping of Gr/Ir(332). On the step-bunching, the dirac point is shifted to ∼ -0.6 V (E Cu D ), typical of the n-doping of Gr/Cu/Ir(332). (c) Conductance map (dI/dV) performed at -0.6 V (10 nm x 10 nm), showing the distinct behavior of the terraces and the step bunching areas resulting in an array of n-and p-doped nanoribbons.

to the stepEunhing terres where the gu hs een interltedF his imge proves tht nE nd pE doped regions re lternted on qrGguGsr@QQPA orresponding to the step unhing nd terres respetivelyF he next step would thus onsist on studying the eletroni properties y ei in order to determine the indued potentil of the surfeF 3.2 Superperiodic potential and band gap on Gr/Ir(332) diities re ssoited to period L in the rel spe tht introdues new G vetor in the eletroni struture @2π/LAF pigFQFIU shows the i@kA sheme for the se of Ih superperiodiity modifying n idel proli ndF sn lk we hve the initil proli nd nd in lue the mklpp replis ssoited to the G vetor @2π/LAF he new periodiity indues new frillouin zone with edges t ±G/2 @π/LAD where the nds ross nd therefore nd gp opening oursD s shown on pigFQFIUF he mplitude of the nd gp @E g A depends on the strength of the potentil ISP nd n modify signi(ntly the dispersionD s shown y the )ttening of the nds t points e nd f @pigFQFIUAF he di'erent senrios for vrious potentil strengths re shown on (gF QFIVF pinite potentils n led to prtil on(nement @pigF QFIVAD while for in(nite potentilsD totl eletroni on(nement ppersD leding to disrete energy levelsF he simplest model to desrie the nd struture of eletrons in Ih periodi poE tentil is the uronigEenney modelF his model onsists of pproximting the periodi potentil to squreEwell periodi potentil with n nlytil solution for nerly free eletrons ISPDISQF fy dpting this model to periodi potentil indued y stepped surfeD the squre potentil is repled y hir rrier U 0 bδ (x) IQUD ISID ISRF por the nd struture of grpheneD the uronigEenney model hs een dpted y using n e'etive twoEdimensionl hir hmiltonin ISS!ISU tht tkes into ount the pseudoEspin nture of the eletrons of grpheneF he periodi potentil indued in this hir hmiltonin is skethed on (gF QFIWD where two stripes of grphene with di'erent gps @∆ a nd ∆ b A nd di'erent fermi veloities @v f a nd v f b A re repeted periodilly t the surfe with period l = a+b long the x xisF he hir hmiltonin is derived from perturtive k•p pproh tht is vlid round the K point of grpheneF he orresponding e'etive rmiltonin for mssless prtiles with veloity v f isX

H = v f σ • p @QFIA
where σ re the uli mtries relted to the two grphene sultties nd p is the momentum opertorF e onsider (rst the diretion where the potentil is vryingD iFeF

H = v f σ x h i d dx @QFPA sf v f depends on the x oordinte @v f = v f (x)AD the prolem eomes nonEhermitinF
st is thus neessry to (nd hermitin opertor for the hmiltonin tht redues to eqF QFP on the se tht v f (x) = v f F his opertor isX

H = v f (x)σ x h i d dx v f (x) @QFQA
sf we now inlude the possiility of motion long the yEdiretion nd we inlude the periodi potentil long x with its respetive vrying gpsD the two dimensionl hmilE tonin isX

H = -ih v f (x)σ x ∂ x v f (x) + v f (x) σ y ∂ y + ∆ (x) σ z @QFRA
he seond term is the one dimensionl opertor long the yEdiretion s in eqF QFPF ∆(x) is nd gp term introdued s digonl term in the hmiltonin through the σ z uli mtrixF ith this hmiltonin opertorD the hir eqution is thenX

Hψ (x, y) = Eψ (x, y) @QFSA
where ψ (x, y) is twoEomponent spinor tht represents the two grphene sulttiesF fy mking the vrile hnge v f (x)ψ (x, y) = φ (x, y)D the hir eqution eomesX

-ihv f (x) σ x ∂ x φ (x) + [∆ (x) σ z -hk y σ y ] φ (x) = Eφ (x) @QFTA whih n e rewritten sX i dφ (x) dx = M (x) φ (x) with M (x) =     ik y -E -∆ (x) hv f (x) -E + ∆ (x) hv f (x) -ik y     @QFUA
he solution of iqF @QFUA is given yX

φ (x) = Pexp   -i x 0 x dx M (x )   φ (x 0 ) @QFVA
where P is the pth ordering opertorD nd n e simpli(ed sX

φ (x) = Λ (x -x 0 ) φ (x 0 ) @QFWA where Λ (x -x 0 ) = exp [-i (x -x 0 ) M (x)]F
fy expnding we otin the reltionX

det [Λ (a + b) -exp [ik x • (a + b)]] = 0 @QFIHA whih yields the reltion 2cosk x • (a + b) = T r [Λ (a + b)] nd llows to determine the dispersion reltionX cos (k x l) = cos (k a a) cos (k b b) + k 2 y h2 v f a v f b -E 2 + ∆ a ∆ b h2 v f a v f b k a k b sin (k a a) sin (k b b) @QFIIA
with the following reltionsX

k a = E 2 -∆ a 2 h2 v f a 2 -k 2 y 1/2 @QFIPA k b = E 2 -∆ b 2 h2 v f b 2 -k 2 y 1/2
@QFIQA pon omprison of this theoretil dispersion with the experimentl one it should e possile to otin ∆ a D ∆ b tht will llow us to understnd the strength of the surfe potentilF 3.2.2 Periodic potential from ARPES measurements e hve seen in the previous setion tht the nd struture ontins the informtion out the superperiodi potentilF es ei is the idel tehnique to determine the experimentl i@kA reltionD it therefore llows to study the potentil strengthF e hve thus studied the nd struture of qrGsr@QQPA y gh y eiF he smple ws (rst grown on the gssiopée preprtion hmer nd immeditely mesured fterwrdsF pigF QFPH shows the experimentl geometryD with terres @greenA nd step unhing @orngeA on the surfeF he nds of the terre @∆θ T err in orngeA nd stepEunhing res @∆θ SB in greenA pper t di'erent ngulr regionsF ih one of these nds should e 'eted y the overll periodi potentilF pigF QFPH shows the permi surfe otined t hν = 150 e tht llows to explore lrge region of reiprol spe to identify the re of interestF he i@kA dispersion long the dotted lines on pnel @A is shown in pnels @A nd @dAF whih is lose to the IH • of the pristine sr@QQPA surfeF he di'erene on the optil tilt ngle etween the sr@QQPA nd the qrGsr@QQPA surfes is due to the reonstrution of the steps into stepEunhing tht resulted in eqully lrge terre nd step unhing resF yne ll the fetures t the permi surfe re understoodD we onentrte on the one of the H rottionD eing the most intense oneF he H dispersion of the terre is explored in more detil y using lower exittion energy @hν = 32 eA tht llows to proe roughly hlf of the reiprol spe mesured in (gF QFPH @in (gF QFPH we were le to proe QÅ -1 D while on (gF QFPI we proe ∼ IFSÅ -1 AF he lk line shows the liner dispersion of the π nd of the H dominF e doping of QQH me is ppreited on the experimentl nd struture in greement with previous results IPPDIPSDIPTDIQRDIQTDISVF he lue lines orrespond to the less intense QSGPS nd QH dominsF he green lines re identi(ed s sr sttes S1D S2 nd I @shown on the line pro(le done t HFT Å

-1 AF S1 is loser to the permi levelD nd its intensity depends on the exittion energy IPTY in our se it overlps with the grphene nd t the permi levelF he sr nd t -1 e is the S2 stte ISWF pinlly the stte t ∼ 1.6 e is the I ndD whose spetrl weight is lso exittion energyEdependent ISWF es we nlyze the grphene ndD we notie tht grphene hs liner dispersion with the fermi veloity of idel grphene @mesured etween the permi level nd -1.5

eAF elong the grphene liner nd there re some ples on whih the spetrl weight deresesF o etter oserve this ehviorD we performed the derivtive of @A @(gF QFPIAF st eomes now ler tht three lotions long the π nd hve n intensity dereseF o etter ppreite this e'etD we plot the inergy histriution gurves @ihgA in (gF QFPI every HFSV • long the K -M diretionF fy following the mxim of the ndD it is ppreited the hrteristi ehvior of nd gp openingD tht is orrelted to the intensity derese previously oservedD indited y lk rrowsF hese three fetures re hrterized y E g = 390 ± 20 meD di'erene etween the nd gps of 0.60 ± 0.06 e nd G/2 vetor of 0.09 ± 0.02 Å -1 D orresponding to L of 3.5 ± 0.9 nm @G = 2π/LAD whih is preisely the hrteristi width of the terres nd step unhingF his nlysis llows us to onlude tht there is n e'et of the nnostruturtion on the eletroni properties of grpheneF e will now pply the model previously presented in etion RFPFIF to the experimentl nd strutureF he superperiodiity is given y l = a + bD where a is the terreGstep unhing width nd b is the limit etween these regionsD usully few ngstromsF foth regions present the sme idel fermi veloityD s proed y eiD simplifying to

v f 1 = v f 2 = v f F sn this modelD the doping of grphene is modeled y V a nd V b F es mesured y eiD the doping of grphene is V a = V b = 330meV F edditionllyD sizle
gp opening mimis the potentil rrier present on region b for the qrGsr@QQPA se @∆ b = ∆AF hereforeD iqnsF @QFIIAD @QFIPA nd @QFIQA re orreted for our se s followingX

cos (k x l) = cos (k 1 a) cos (k 2 b) + k 2 y h2 v 2 f + E • (E -V ) h2 v 2 f k 1 k 2 @QFIRA
with the following reltionsX 3.2. SUPERPERIODIC POTENTIAL AND BAND GAP ON GR/IR(332)

TU nole metlli stepped surfes ISIAD whih gives rise to eletroni prtil on(nementF es the on(nement my depend on the terre widthD we will in the following study grphene on urved t rystl @ghpter RA in order to explore di'erent viinl surfes t the sme time round the nominl t@IIIA surfeF

k 1 = [V -E] 2 h2 v 2 f -k 2 y 1/2 @QFISA k 2 = E 2 -∆ 2 h2 v 2 f -k 2 y 1/2 @QFITA

Conclusions and perspectives

sn this hpter we explored the modi(tion of the eletroni properties of grphene y nnostruturtion of the sustrteF e (rst studied the growth nd morphology of grphene on the sr@QQPA y two di'erent methodsX temperture progrmmed growth nd hemil vpor depositionF e lso interlted guD where periodi struture with modultion of the eletroni properties ws oserved y F ei mesurements oserved nd gp openings due to the superperiodi potentil tht re explined with hirEhmiltoninF wore preisely we hve understoodX

• he growth nd struture of grphene on sr@QQPA vi gh nd q qrphene growth vi oth q nd gh modi(es the originl steps of the sr@QQPA sustrte nd trnsforms the underlying surfe in n rry of terres nd step unhE ing res where grphene lter growsF he q tehnique produes grphene domins ligned with the underlying sustrte tht fully overs the step unhing resF gh llows to otin ontinuous grphene on top of the whole sr@QQPA surfe with vrious oexisting rottionl dominsF ell the grphene res hve the sme spetrosopi sigE nl thn qrGsr@IIIA with slight pEdopingF yn the other hndD in the suEmonolyer overge of interlted guD gu preferentilly interltes on the step unhing reD resulting in n rry of nE nd pE doped nnorions on single ontinuous lyerF elthough the growth within the )t pltinum surfe is very similr to tht on sr@IIIAD reent studies hve shown tht disontinuous grphene n e otined for ertin rystllogrphi orienttionsD s on t@QIIA @(gF RFIEfAF he surfe onsists of two sets of fets mrked y the lue nd green retngles @(gF RFIAF nel @dA shows the zoom of the lue reD where the periodi struture is ttriuted to grpheneF yn the other hndD t the djent fetD no distinguishle fetures of grphene re found @pnel @eAAD onsistently with re t@IIIA @pnel @fAAF sn order to proe wide rnge of viinl surfes of t@IIIAD some of whih might produe disontinuous grphene nnorionsD we hve ought urved t rystl to 4.1. GROWTH AND STRUCTURE OF GRAPHENE ON PT UQ fihur grystl @n estinD pinAD whose mrosopi orienttion is tilted up to IT • towrds the 112 nd the 112 diretions @(gF RFPEAF he 9 mm×9 mm urved t rystl onsists of terres of di'erent widthsD depending on the mrosopi viinl ngleD tht run prllel to the 110 diretionF he mjor dvntge of urved rystl is tht single grphene growth proess llows to proe severl viinl surfes t the timeF fy studying di'erent sites ross the red line @(gF RFPAD eh of them orreE sponding to vrious terre sizesD we will otin the eletroni struture ssoited to eh terre nd orrelte it to the tomi strutureF 4.1.1 Preparation of multivicinal Pt(111) substrate he lening of the t@IIIA multiviinl sustrte onsists of (rst sputtering yle t with 1ke Ar + em t 8 × 10 -6 mr pressure t three di'erent smple lotionsF he sputtering is performed long the 110 diretion @prllel to the stepsAD to preserve the viinlity of the surfeF he sputtering is followed y n eletron omrdment nneling t UHH • g for IH min lter ooled down to t ontrolled rte of 60 ± 10 • gGminF e seond yle of sputtering is followed y n nneling under oxygen tmosphere @1 × 10 -7 mrA for IH minF he smple is then ooled down to t ontrolled rte of 60 ± 10 • gGmin nd (nl )sh is performed t WSH • gF o urtely red the temperture long the rystlD we hve mesured the temperture with pyrometer @ = 0.1A t the enter of the smpleF efter repeted yles of sputteringGnnelingD viih nd w were performed on severl positions on the smpleD I mm prtF he negtive nd positive positions re ssoited to the eEsteps nd fEsteps respetively tht re found on either side of the rystl @(gF RFPAF yn the eEstep terminted edgesD the lst tomi row of the upper terre re ligned with the (rst tomi row of the lower terreF yn the other hndD on the fEstep terminted edgesD the lst tomi row of the upper terre is shifted y hlf lttie prmeter prllel to the step with respet to the (rst tomi row of the lower terreF even di'erent points were proed y w nd viihX -3mmD -2mmD -1mmD 0mmD +1mmD +2mmD +3mmF hese positions present mrosopi viinl ngle with respet to the (111) surfe of -14.5

• D -11 • D -7 • D -3.5 • D 0 • D +3.5 • D +7 • D +11 • nd +14.5
• respetivelyF sn the followingD we will refer to this viinl ngle to present our resultsF epresenttive regions re shown on (gF RFPF sn the region orresponding to the t@IIIA surfe @pnel hAD the terres re lrge nd without preferentil orienttionD s seen in the w imge @pnel jAF es we move wy from the enter towrds the eEsteps regionD the viih shows shrp splitting of the t@IIIA spots long the 112 diretion @pnels f nd dAF fy mesuring the splitE STM also shows higher quality of terraces in the A-step side.

ting nd ompring it with the distne etween the t@IIIA spotsD the terre size is L = 2.1 ±0.1 nm nd L = 1.2 ±0.1 nm for the -7 • nd -11 • viinl ngles respetivelyD in greement with the expeted viinl surfeF he splitting spots re shrpD inditing the high qulity ordering of the terresD s seen y the wellEde(ned periodiity oserved y w on pnels g nd eF hen moving from the enter towrds the fEsteps sideD the viih shows lurred splitting of the t@IIIA spots @pnels k nd nAF he lurred splitting indites wider he ghemil por heposition @ghA tehnique ws hosen sine the rystl is lrge @W mm×WmmAD nd it is desirle to grow grphene nnorions on the whole surfe t one @in qD the growth is done in severl stgesAF es we expet to hve disontinuous grphene t step edges t ertin viinlitiesD gh is the idel ndidte for suh growthF e hose gin ethylene @C 2 H 4 A nd similr prmeters to those used for qrGsr@QQPAF he sustrte is nneled to VHH • g for IH minF while exposed to n ethylene prtil pressure of 3×10 -7 mrF he smple is then ooled down to t ontrolled rte of 60±1 • gGminF he surfe is hrterized y viih @eletron inoming em t 82.3 e to oserve the @IxIA spots of t nd the detils round themA nd nlyzed y snning tunneling mirosopy t the urfe vortory in the oleil ynhrotronF pigF RFQ shows the viih ptterns nd the w imges of di'erent viinlities otined s funtion of the viinl ngleF he growth t the position orresponding to t@IIIA is s expetedF he viih @pnel dA shows di'erent fetures of grphene on tX shrp QH domin nd n r round itF he inset shows the @IxIA spot of pltinum nd two grphene rottions t ±S • @SD S9AF he intensity of these grphene orienttions dereses wy from the @IIIA surfeF he w imges on viinl ngle 0 • @pnel dA show nonEordered lrge terresF qrphene presents severl rottions s demonstrted y the two di'erent moiré strutures on tomi resolved imges @the moiré unit ell is indited y the white rhomus on pnel dAF qrphene grows over the step edgesD s demonstrted y the ontinuity of the honeyom network @white hexgonsA on oth sides of the stepsD in greement with previous work ITP!ITRD ITU @see lso zooms in the eppendix eFQAF hen exploring the eEsteps sideD the step rry is homogeneous for the smll viinl ngle -3.5 • @pnel AF e ler splitting of the @1x1A t spots is oserved on the viih insetD whih orresponds to periodiity of L = 5.8 ± 0.8 nmF he Qh w imge shows homogeneous periodi struture omposed of @IIIA terres nd step unhing UU resF e pixelEyEpixel nlysis of the w imge perpendiulr to the steps llows to detet the step edges nd to lulte the surfe periodiity v @from the terre nd the step unhingAF he inset shows the shrp eriodi idth histriution @hA histogrm inditing periodiity of L = 6.8 ± 1.8 nmF qrphene is ontinuous ross the terres @lue in the right pnelA nd step unhing @orngeAD s shown y the honeyom struture on oth sides of the step unhingD inditing the sene of disontinuous grphene rionsF por viinl ngle of -7 • D we (nd the est ordered surfes @pnel AF por the (rst timeD we oserve replis of the grphene rsD resulting from the high ordered periodi strutureF he periodiity here is smllerD L = 5.8 ± 1.5 nm s lulted from the viih spots nd oserved in w imgesD showing nrrower terres s the result of wider step unhingF he inset shows the h histogrms with periodiity of L = 5.8 ± 0.5 nmF rereD grphene is lso ontinuousD s suggested y the honeyom on the lue terres t oth sides of the ornge step unhing resF pinllyD the highest viinl ngle tht we studied is -11 • F t spot splitting in viih is similr to tht oserved for θ = -7 • D orresponding to L = 4.8±1.5 nmF he Qh w imge shows strightEedged terresD while the h histogrm indites periodiity of L = 5.7 ± 1.8 nmF he lrge error r is in greement with the rod t splitting spot in viihD re)eting less homogeneous surfeF yn the ontrryD s we move towrds the fEsteps sideD the viih of the viinl ngle +3.5 • is initilly very similr to tht of the )t surfeF w imges show the pprition of preferentil orienttion for steps nd the development of step unhing res @pnel eX gry res on the Qh imge nd ornge on the tomi resolution imgeAD leding to smller terresF he inset shows the h histogrm tht gives L = 6.6 ± 2.7 nmF he tomilly resolved w imges show tht the terres re only prtilly homogeneousD s their edges wiggleD giving rise to widths etween 4.6 nd 6.6 nmF uh n oservtion explins why the spot splitting is oserved on the viihF hespite the inhomogeneous terre widthD grphene rottionl domins @S nd IRA re ontinuous ross the stepsD s highlighted y the ontinuity of the moiré unit ell on oth domins @white rhomus on pnel eA in the w imgeF hen moving even further wy long the fEsteps side to the viinl ngles +7 • nd +11 • @pnels f nd gAD the pltinum spots lose intensity in the viih ptternD nd the splitting is less de(nedD inditing the wekening of the ordering of the step rryF qrphene is still oserved in tomilly resolved imgesD ut w imges show the disorder of the step rryF he h histogrms show the inhomogeneity in rod histogrm of widthsD rnging from P to IS nm for θ = +7 • nd from 2.5 nm to 13 nm for θ = +11 • F hese res will e disrded from the eletroni struture nlysis due to the struturl inhomogeneityF sn onlusionD we oserve tht grphene grows more ordered in viinl surfes on the eEsteps sideD s seen y the splitting of the t spotF he qulity of the step periodiity dereses t the edges of the smpleD nmely for viinl ngles +11 • nd -11 • with respet to intermedite sitesF qrphene grows ontinuously ross the smple etween the terres nd step unhing resF ith the otined ontinuous grpheneD we expet modi(tion of the eletroni properties similrly to qrGsr@QQPA vi the nnostruturtion nd the pperne of superperiodi potentilF 4.2 Band gap tailoring on graphene on multivicinal Pt(111) es indited in hpter QD informtion out superperiodi potentils is ontined in the nd strutureF e will thus use ei to determine the experimentl i@kA reltion nd mesure the potentil strength indued in grphene y the periodi nnostruE turtionF e will ompre the e'et of nnostruturing on di'erent viinl surfesF pigF RFRE shows the i@kA mps otined t the u point of grphene long diE retion perpendiulr to the steps s funtion of the viinl ngleF he (rst striking feture is tht the liner dispersion of grphene is disontinuousD s the intensity deE reses t ertin energies nd its i@kA lotion depends on the viinl surfeD s we will seeF nels dEf hve superimposed lines to etter understnd the eletroni strutureF wo di'erent hir ones re oservedD orresponding to S nd S9 roE ttionl domins @green linesAF hepending on the viinlity or mye on the surfe qulityD the doping of grphene vries from 320 me to 250 meD whih lso hppens for t@IIIA ITQF sn ddition to the grphene ones of S nd S9 dominsD yn nd is ppreited round PFS eF his nd orresponds to the sddle point of the π nd of the QH rottionl domin tht is superimposed with the S nd S9 grphene ndsF glose to the fermi level there is t@IIIA ulk nd indited y lk lineD tht lso superimposes with the grphene ndsF sf we now fous on the disontinuities of the grphene nd struture t the loE tions with no interferene with other spetrl feturesD we must onentrte on the disontinuity leled Pnd gp on (gF RFRdEfF his region is shown in the inergy hisE hnges with the viinlityF sf we tre line through the nd gp energyD there is shift from one surfe to the otherF here is lso shift in the k position where the nd gp ppersD mening tht the G vetor depends on the viinl ngleF sndeedD the periodiities ssoited to the G vetor oserved in ei re 3.8 ± 0.9 nm @-5.5 • AD 3.9 ± 0.9 nm @-2 • A nd 4.5 ± 0.9 nm @+2 • AF hese vlues orrespond roughly to hlf of the periodiity found y viih nd wD s lso oserved for qrGsr@QQPA nd in the mgneti properties of feted systems ITWF 4.3 Dirac-hamiltonian model on Gr/multivicinal Pt(111)

he hirErmiltonin model n e pplied to grphene on urved t s for qrGsr@QQPAD llowing to reprodue the experimentl ei nds nd to lulte the potentil rrier strength t the di'erent viinl rrysF pigF RFS shows the min prmeters used in the hirEhmiltonin model for ontinuous grphene under periodi potenE tilF he periodiity is given y l = a + bD where a is the width of the min fets t the surfeD either the @IIIA terres or the stepEunhed fets nd b is the limit etween these two regions @of usully few ngstroms wideA nd is where the potentil rrier is foundF he fermi veloity in ll the viinlities should orrespond to the theoretil where the gp is reprodued with 3.2 nm nd 3.2 e Å for -5.5 • @pnel AD 3.5 nm nd 2.8 e Å for -2 • @pnel AD nd 3.5 nm nd 1.8 e Å for +2 • @pnel dAF pigF RFT summrizes the resultsF he experimentl periodiity s funtion of the viinlity re shownD oth those otined experimentlly @lkD lueD greenA nd vi the hirEhmiltonin model @redAF he verge fet width dereses when inresing the viinl ngle s we move wy from the t@IIIA surfeD s represented y the green enveloping linesF he potentil strength s funtion of the verge terre width for pltinum is plotted on (gF RFT @lue dimondsAF he results of sr@QQPA re lso inluded @fEstepsD viinl ngle of +11 • D represented y the red irleAF fy ompring two di'erent terre widths on pltinum with the sme step termintion @lue enlosing on (gF RFTAD it n e ppreited tht the potentil strength inreses for smller terre widthsD suggesting the possiility of rehing totl on(nement for smller terresD s oserved in viinl surfes of eu ISIF sf we now ompre to the potentil indued for the sme terre width ut di'erent step type @pink enlosing on (gF RFTAD we notie lmost douling of the potentil strength for e stepsD proly fvoring higher oupling etween the grphene nd the sustrteF pinllyD if we ompre the potentil s funtion of the sustrte with sme verge terre width nd fEstep edge @green enlosing on (gF RFTAD we see tht the potentil strength gretly inreses on iridiumD proly due to the smller grpheneEsustrte distneF Gap opening on graphene nanoribbons on SiC e hve previously onsidered the tiloring of the eletroni properties of grphene on nole metl surfe vi the nnostrutured sustrte onsisting of regulr step rryF sn this hpterD we will fous on the engineering of the eletroni properties of grphene on ig on n rti(illy indued nnostrutureF erti(il grphene nnorions proE dued from proedure omining lithogrphy nd nnelingEindued growth will e studiedF hile the lithogrphi proedure llows to lote the nnostruture t willD the susequent nnelings llow to grow grphene t the seleted lotions with edges in their minimum energy on(gurtion IUHF he so formed grphene nnorions sysE tem hve een demonstrted to exhiit metlEsemiondutingEmetl juntions VWD nd lthough it ws stted tht the origin of the wide semionduting ehvior ws urved grpheneD this remins to e lri(edF ith this golD we omined nning unneling wirosopy @wA with highEresolution nning rnsmission iletron wirosopy @iwA in di'erent modes @frightEpield @fpAD vowE nd righEengle ennulr hrkE pield @veehpD reehpAA s well s lol iletron inergy voss petrosopy @iivAF he iw nlysis required the development of thinning method for the delite smple with nnorion rryD where the min informtion is loted in the few lst he group of lt de reer @qeorgi ehA hs developed n originl pproh to grow rions tht should present smooth edgesF he proedure is skethed in (gF SFIF vithogrphy (rst retes trenhes tht re the seeds for nnorion formtionF sn our se we need rion rry to esily mesure in photoemission @to verge over lrge numer of nnorionsA or to esily lote the regions of interest on the mirosopiesF nel @A shows the lithogrphed rry of trenhes ethed in RrEig @HHHIA prllel to the diretion 1120 of ig for rmhir nnorions @or the perpendiulr 1100 ig diretion for zigzg nnorionsAF he ptterned sustrte is nneled t IIHH • g for 5.1. GRAPHENE SIDEWALL NANORIBBONS AND BAND GAP VW QH minD followed y seond nneling t ISPS • g for few minutes in on(nement ontrolled sulimtion furne VWD IUHD IURF he (rst nneling step rerystllizes the vertil (1100) nd (1100) wlls into the stle (110n) nd (110n) fetsD respetivelyF he (nl highEtemperture growth step produes grpheneD s the grphene growth rte is slower on the ig@HHHIA fet thn on the (110n) nd (110n) fetsF qrphene ppers in these sidewll fets nd therefore rions grown here re lled sidewll nnorionsF he resulting smple onsists of n rry of feted mes shpesD s shown in pnel @AF foth the @HHHIA plteus nd trenh ottom widths n e vried independently nd the height di'erene etween plteus nd trenhes n e lso tilored t willF he height di'erene depends on the initil lithogrphi proess nd ontrols the width of the grphene nnorion tht lies on the sidewll etween the plteu nd the trenhF feuse of the orienttionl epitxy of grphene grown on ig@HHHIAD the edge of the rions n e tunedF his ility to tilor the width nd edge of the rions opens up the possiility of tuning their eletroni properties in wy tht is omptile with mss produtionF sn this studyD we minly fous on grphene nnorions with trenh wlls ethed prllel to the (1100) orienttionD tht isD rmhir edge grphene rionsF sn our seD the trenhes re QH to QS nm deep nd produe RH nm wide nnorions tht exhiit exeptionl llisti trnsport up to ISµm t room temperture nd lso present wide ndgp t lotion to e disussed VTD VWF ithin the frmework of the ollortion with idwrd gonrd t qeorgi eh nd the gssiopée emline t oleil ynhrotronD the rrys of sidewll nnorions hve een studied y ei to identify the lotion nd nd struture of these ojetsF he ngulr resolution of this tehnique llows to di'erentite regions with di'erent surfe normlF pigF SFP shows three di'erent regionsD their respetive surE fe norml nd nd struture VWF he norml of the )t ig(0001) is tken s the referene norml @0 • AF hue to the geometry of the system nd preliminry epw studies performed efore the ei mesurementsD it ws estimted tht the sidewll nnorions re found with norml t ∼ 30 • F fetween these two regionsD there is trnsition region with normls etween 10 • E25 • D whose origin ws proposed to e t the highlighted yellow res oth ove or elow the sidewll nnorion VWF he nd struture t every region n e proed t the grphene uEpoint ssoited to every surfe normlF sn order to proe orretly the ngulr rnge for every fetureD the sidewll nnorion rry ws slightly overgrownD so tht grphene would grow on ig(0001) to serve s the referene for the mesurementsF nel @A shows the metlli nEdoped grphene ndD typil of grphene lyer on ig@HHHIA IUSF hen moving ∼ 30 • from the refereneD neutrl hrged metlli grphene nd is otined @pnel AF his neutrlity suggests deoupling etween the sidewll nnorion nd the sustrteD ontrrily to the nEdoped grphene on ig@HHHIAD nd my e due to the pperne of multilyersF yn the other hndD when looking t the eletroni struture of the trnsition regionD gpped nd of t lest 500 me is otined perpendiulr to the trenhes @pnel AD whose origin ws suggested to e loted t the urved region @pigF eFR on the eppendix shows ut prllel to the trenhesAF sn order to understnd why nd where this lrge ndgp omes fromD we need detiled understnding of the nnorion strutureF e hve thus explored the tomi struture of epitxil grphene sidewll nnorions (rstly y wF purther detiled snning tunneling mirosopy nd spetrosopy performed on higher qulity zigzg sidewll nnorions llow to ompre nd distinguish their eleE troni struture versus the nds otined in ei for rmhir sidewll nnoriE onsF he w dt were quired in ollortion with wuriel iot nd hniel wlterre t the snstitut ten vmourD nd nlyzed with former postEdo srene lE io t oleil ynhrotronF pirstD we identify nd lel ll the interest resD nmely the ig@HHHIA plteu @yellowA nd trenh @lueAD the sidewll nnorion @greenA nd the upper @redA nd lower @purpleA trnsition res @(gF SFRAF he tomilly resolved imE ges show perfet grphene lttie on the sidewll region @pnel dAD whose orienttion is zigzgD s shown y the superposed grphene lttie in pnels @A nd @AF e hve lso studied in detil rmhir sidewll nnorionsF vrge sle topoE grphi imges show the oherene of the rry omposed of plteusD fets nd trenhes @(gF SFSAD where the edges re smooth nd strightF es we zoom on the (110n) sidewll nd in order to oserve simultneously the honeyom orrugtion nd the strong topogrphi vritionsD we use onstnt urrent imging @(gF SFSAF he (rst region @IA orresponds to the trenh ottom where the grphene honeyom is not well resolved ut the moiré periodiity is tht of u'er lyerF he seond region @PA is grphene growing long the fet up to the plteu nd onsists of multiple urves prllel to the fetF sn region @QAD due to the spei( nneling temperture used in this smpleD grphene overgrows the fet onto the ig@HHHIA plteuF he overgrown grphene extends to oundry with the fourth regionD where the u'er lyer is oserved gin @RAF he tomi resolution w imge on the trnsition region etween the fet nd the plteu @lue retngleA on(rms unmiguously the orienE ttion of the edgeF es shown y the superimposed honeyom lttie on pnel @AD it Mechanical polishing st is neessry to polish the two surfes of I mm y Q mm until rehing few hundreds of nm thiknessF pigF SFV shows sheme of the initil sl nd identi(es the two fes to polish @e nd fAF he polishing is divided in two stepsX @IA polishing nd smoothing of fe f to ensure tht this fe will remin glued to the support nd @PAD polishing fe e until rehing few hundreds of nm thiknessF yn the (rst stepD fe e will e glued to the polishing support with rystl silionF pe f will e polished with deresing dimond grinding ppers @ISD TD nd Q µmA t deresing speeds from QH to PH rpm to void rking of the surfeF he polishing ends when the surfe is visily smooth t n optil mirosopeF he sl is then unglued sidewll fetF nel @A shows n tomilly resolved iwEfp imge with lrge (eld of view of the sidewll where two min fmilies of fets re oservedF he entrl prt of the sidewll @tens of nnometers wideA hs norml rotted F QH • with respet to the ig @HHHIA plne @orresponding to @1107A surfeAF he top nd the ottom prt of the sidewll re omposed of fets tilted ∼PH • from the @HHHIA plneD iFeF to the (110n) n=9,10 fetD onsistent with the rippleElike struture oserved y wF e lose up on the ripples of the (110n) n=9,10 fet is shown in pnels EdF he detil shows tht the sustrte presents smll ig@HHHIA miniterres nd minifets due to the stiliztion of the initil ig fet during grphene growth IUVF he minifets typilly hve @1105A orienttion extending over R ig ilyers long the HHHI diE retionD tht isD the unit ell of the RrEig polytypeF qrphene grows ontinuously over the miniterres nd minifetsD ut the distne to the sustrte hngesF he distne of the grphene lyer to the miniterres is PFQ ÅD distne similr to the tightly ound u'er lyer on the i @HHHIA fe @referred s oupled grphene in lue on pnels @A nd @dAAF yn the other hndD urved )oting grphene lyer is found on the minifets @referred s deoupled minirion in green on pnels @A nd @dAAF sts distne to the sustrte is extremely high @RFH ÅAD whih ould use n eletroni deE oupling from the igD nd forms nrrow rmhirEedge minirion running prllel to the ig step edgeF hile nlyzing the entire (110n) n=9,10 fet @pnel @eAAD we n see tht grphene in green runs ontinuously from the sidewll to the rippleElike struture until rriving to the ig@HHHIAF et the @1107A sidewll we (nd lrge rmhir nnorion lrger thn PH nm with n verge distne to the sustrte of F QFS ÅD whih is muh lrger thn the PFQ Å distne for the tightly onded u'er lyer IUW!IVIF his lerly indites tht the sidewll nnorion is essentilly deoupled from the sustrte @or delminted IVPAD prt from sprse more or less regulrly sped nhored pointsF xote tht the @1107A nd @1107A surfes re nonpolr IVQD whih my explin why the nnorions re hrge neutrl on ei VTD VWF yn the other hndD t the (110n) n=9,10 fet the deoupled minirions hve normls tht vry from ∼ IP to PS • D orresponding to the normls oserved in eiF heir width is etween IEP nmF hese struturl studies on(rm the orienttion of the sidewll fets tht ws determined y ngleEresolved photoemissionD s well s the presene of suEstruture on the trnsition regionsF engleEresolved photoemission hs oserved liner dispersion t the @1107A extended fetF his is onsistent with the iw oservtion for the lrge entrl rion eletronilly deoupled from the sustrte nd whose width will not produe n oservle gpF e lso know tht the trnsition regions with norml etween HHHI nd 1107 exhiit nd gp of t lest SHH meD orresponding to the normls of the deoupled minirionsF here re severl possiilities for nd gp opening in these minirionsF nixil strin n open gp in rmhir rions when the strin is perpendiulr to the edge IDP ut in order to explin the experimentl gpD onds should e strined y n unphysil lrge vlue of more thn PH7F xeverthelessD iw imges show tht grphene in the minirions )ots on the minifetsD tht isD the grphene lyer is le to relx ny residul strinD whih rules out strinEindued gpF e more relisti possiility is quntum on(nementD where the nrrow IEP nm minirions ould produe nd gps of HFS to I e ISF sn order to on(rm tht the nd gp oserved y ei is e'etively sptilly loE ted in the urved grphene minirionsD we performed iwEiiv mesurementsF e fous on the ron uEedge orresponding to trnsitions etween the gEIs ore eletron to the unoupied sttes just ove the permi level @(gF SFIPAF he oundry etween the plteu nd the sidewll overed y single ontinuous grphene lyer is shown in pnel @AF he u'er lyer t the ig top surfe nd three minirions re oservedF nel @A is zoomed imge of the re oxed in pnel @A where spetroE mirosopy mesurements were performedF iiv spetr were olleted with sptil step of HFHR nm nd n quisition time of severl milliseondsF petr integrted in the oxes of pnel @A re hrteristi of di'erent regions @pnel @AAX the u'er lyer @IAD the (rst minirion @PAD grphene on the miniterre @QA nd ulk ig @RAF he spetrum from the minirion shows the π * nd σ * peks hrteristi of grphene or grphiteElike mterils IVPF e similrity is oserved on the spetr from the u'er lyer nd the grphene on the miniterreD s these two regions hve notiele ddiE tionl spetrl intensity in etween the π * nd σ * peks loted F IFQ e higher in energy thn the π * @indited y n rrow in spetrum I in pnel @AAF o isolte the dditionl fetures in the u'er nd grphene on miniterreD we hve nlyzed the min spetrl omponents in the iiv spetr y using spetrl unmixing sed on ertex omponent nlysis IVRD resulting in two spetrl omponents e nd fD shown in pnel @AF nel @dAD@eA show the sptil distriution of omponents e nd f respetivelyF gomponent e is oserved ll long the ron tomi lyerD nd it is thus ssoited with grpheneGgrphiteF yn the other hndD the dditionl omponent f is only present when the ron lyer is strongly ounded to the ig surfe @iFeFD either t the u'er lyer or t the grphene on the miniterresAF ei mesurements hve indited tht the u'er lyer hs smll nd gp with the presene of dditionl sptilly lolized inEgp sttes ssoited with the omplex hyridiztion etween the u'er lyer nd the ig surfe IVSF hese peulir eletroni strutures might e the origin of the dditionl spetrl omponent f found in the u'er lyer nd IHR CHAPTER 5. GAP OPENING ON GRAPHENE NANORIBBONS ON SIC lso on grphene t the miniterresF htever the ext origin of this iiv spetrl omponent fD it on(rms tht the eletroni struture t oth sides of minirions is di'erent from tht of pure grpheneGgrphiteF o etter visulize the di'erene in eletroni strutureD pnel @fA shows pseudoolor imge where gry enhnes the igD yn highlights the deoupled minirions nd white shows the u'er lyer nd grphene on the miniterresF 5.4 Atomic origin of the band gap sn order to further explore the eletroni struture of the minirionsD we hve investiE gted iiv spetr t higher resolutionF pigF SFIQ shows n iw imge on ilyer grphene smpleF egion S orresponds to the seond lyer on ig@HHHIAD lerly distinE guished ove the u'er lyer nd known to e metlli IVHF egion T orresponds to the minirions on ilyerF he omprtive iiv spetrum t oth positions shows di'erent shpe of the π * nd exhiits n energy shift of round HFPS e @pigF SFIQAF on(rmed y the initio lultions performed y elerto oelli t the vortoire de hysique des olidesF he surfe orresponding to 1, 1, 0, 10 t the top nd ottom region of the sidewll hve een modeled y IFU nm thik ig sl where the lower surfe hs een sturted y hydrogen tomsF he superell periodiity hs een hosen long the 1, 1, 0, 10 step edge diretion in order to minimize the strin on the grphene rionsF hree rmhir grphene periods re ommodted over four ig step periods leding to grphene ompression s low s QFT7F his ompression relxes through slight outEofEplne rippling of the minirionsF e PFW nm wide grphene sheet is onsidered for the modelD where IFI nm is loted on top of the ig miniterres @u'er lyerA nd IFV nm is freestnding @minirionsAF he fully relxed VHT toms model is displyed in (gF SFIRF he projeted density of sttes of the system is presented in (gF SFIRF he u'er lyer t the miniterres hs projeted density of sttes shifted with respet to the freeEstnding rionsD whih is in greement with previous results on extended u'er lyers IVUDIVVF he freeEstnding grphene region presents lol density pproximE tion of the eletroni gp of out I e @pnel @AAF his energy gp is of the order of mgnitude of the expeted gp for freeEstnding rmhir rions with similr widthsF he eletroni ehvior of the omplex igGgrphene heterostruture n e linked to

oneD so v a = v b = v f F he doping V a nd V b for

Conclusions

e indued superperiodi potentil on grphene y growing it in two di'erent suE strtesD viinl sr@QQPA surfe nd multiviinl t@IIIA surfeF hose two suE strtes re tlysts nd llow to grow grphene y the deomposition of ethyleneF yn sr@QQPA we found tht grphene modi(es the originl steps of the sr@QQPA suE strte nd trnsforms the underlying surfe in n rry of terres nd step unhE ing resF e hve used two di'erent proedures to grow grpheneF he temperture progrmmed growth tehnique produes grphene domins ligned with the underlyE ing sustrte tht fully over the step unhing resF his is promising route for grphene nnorions growthD nd the method should e revisited with lower dosgesD whih is n interesting perspetive of this reserhD ut not omplished due to limited timeF yn the other hndD hemil vpor deposition llows to otin slightly pEdoped grphene overing the whole sr@QQPA surfe with vrious oexisting rottionl dominsF his ontinuous grphene lyer feels the periodi nnostruturtion of the underlyE ing sustrteD s we hve oserved y ngleEresolved photoemission spetrosopyF he grphene π nd presents severl minigps due to the superperiodi potentilF hese IHW minigps re onsistent with the struturl periodiity proed y viih nd wD nd n e stisftorily explined y hirEhmiltonin modelF he modeliztion of the photoemission results hs llowed us to retrieve the potentil strength t the juntions etween the terres nd step unhingF e hve lso tried to inrese the surfe potentil y interlting guD whih is known to e dsored t the step edgesF gu preferentilly interltes on the step unhing reD produing there nEdoped rionsD while the nonEinterlted res remin pEdopedF his results in n rry of nE nd pE doped nnorions on single ontinuous lyerD n rry to e explored in the futureF e hve lso tilored the surfe potentil y hnging the nnostruturtion of the surfeF por thisD we hve hosen urved multiviinl t@IIIA sustrteF he growth of grphene gin modi(es the sustrteD with the trnsformtion of the surfe into @IIIA terres nd step unhing regionsF ith our growth onditionsD the eEsteps promote more homogeneous terre rrys nd step unhing resD while fEtype steps present wiggly edges nd nonEhomogeneous step rrysF he homogeneous step rrys llowed us to tilor di'erent minigps s funtion of the viinlityF es in the se of sr@QQPAD the omined study of eiD viihD w nd modeliztion llowed us to retrieve the potentil strength t the juntions etween terres nd step unhingF yur study shows tht it is possile to ontrol the surfe potentil nd therefore the indued minigps in di'erent wysF he potentil strength inreses s funtion of the viinl ngleD s funtion of the step type @e or fAD nd s funtion of the sustrteF he seond wy to ontrol the gp tht s hve studied is the eletroni on(neE ment in grphene nnorions grown on igF hese rions re grown on n rry of rti(illy lithogrphed trenhes stilized into sidewlls y further nneling on the ig@HHHIA fetF rereD nd gp opening with unler tomi origin hd een oserved y eiF e hve performed the (rst tomilly resolved study in these nnostruturesD demonstrting y w the smoothness nd hirlity of the edgesD nd preisely loting the grphene on the fetsF e hve lso disovered some unexpeted nnorions of I E P nm wideF o nlyze the role of these strutures on the nd gp openingD we hve studied them y rossEsetionl iw studyD so we dpted stnE drd thinning proess to sidewll nnorion smplesF e oserved tht the miniriE ons oserved y w order the extended (110n) nd (110n) fets of the sidewll rionsD where photoemission nd indite the presene of metlli grpheneF iw hs llowed to oserve the oupling of these minirions to the sustrteF rereD grphene extends ontinuously on the suEfeted ig sustrte oth on the @1105A minifets nd @0001A miniterresF qrphene on top of the @0001A miniterres is ouE III pled to the sustrte nd is semiondutingD on(rmed y lol iiv mesurementsF yn the other hndD grphene on top of the @1105A minifets is deoupled from the sustrteF hespite thisD iiv shows gp on these deoupled minirions of I E P nm width tht hve n orienttion omptile with the gp oserved in photoemissionF ell these results together hve llowed us to onlude tht the nd gp is due to eletroni on(nementF Perspectives his hh work hs opened mny interesting perspetivesF e hve foused on the role of superperiodi potentils on ontinuous grphene lyersD nd the nturl evolution of this work is to develop disontinuous grphene rions to promote totl on(nementD s in the se of rions on igF yn the se of grphene on sr@QQPAD we hve shown tht the growth strts on the step unhing resD so disontinuous nnorions n e proly otined y performing only prtil overge of the surfeF yn the se of grphene on viinl t@IIIAD n interesting perspetive is to exploit the higher surfe potentil of fEtype stepsF roweverD these step rrys were more irregulr with the explored onditions thn the ones with eEtypeD suggesting the need of detiled ves sustrts viinux de métux noles utilisés ont été l9sr@QQPA et un ristl ouré multiviinl de t@IIIAF v surfe prfite d9sr@QQPA est omposée de mrhes d9sr@IIIA de IFPS nmF ges mrhes s9étendent le long de l diretion 101 et introduisent une périodiité dns l diretion 121 @(gF fFQAF ve ristl multiviinl de t@IIIA perE met d9étudier une lrge gmme des surfes viinles de t@IIIAD ertines pouvnt priori produire des nnoruns de grphène disontinusF v9orienttion mrosopique du ristl multiviinl v de H • pour l normle @IIIA jusqu9à IT • dns les diretions 112 et 112 @(gF fFQAF ves vleurs positives et négtives sont ssoiés ux ords de mrhe du type e et f de hque ôté du ristl @(gF fFQAF ur es sustrtsD nous vons utilisé deux di'érentes méthodes de roissne du grphèneD notmment l roissne progrmmée en tempérture @temperture proE grmmed growth E q en nglisA et le dépôt himique en phse vpeur @hemiE l vpor deposition E gh en nglisAF v méthode q onsiste à fire un dépôt ve résultt de l roissne de grphène sur sr@QQPA pr gh est une ouhe onE tinue de grphène sur des zones du sustrt ve de terrsses @IIIA et des régions d9umultion de mrhes @indiqués pr et f sur l (gF fFRAF ur l surfe mulE tiviinle de t @IIIAD le grphène produit une struture similire des deux ôtés du ristlF v (gF fFR montre une imge w représenttive de l surfeF ne fois que le grphène repose sur une surfe ve une superpériodiité ien dé(nieD l struture életronique été étudiée pr photoémission résolue en ngle @eiAF ur les deux systèmes étudiés nous retrouvons l dispersion linéire du grphène ve des ndes interdites ux endroits de l9espe réiproque orrespondnt u ord de zone de l superpériodiitéD dont l période été préllement mesurée pr wF v (gF fFS montre l struture de ndes et l9emplement des ndes interdites pour le système qrGsr@QQPA @pnneu A et pour trois endroits di'érents pour le système qrGmultiviinl t@IIIAF our modéliser l struture de ndesD nous vons utilisé un hmiltonien de hir à deux dimensionsF eve et hmiltonien on peut dérire les dispersions et déE duire le potentiel responsle de l superpériodiité à prtir de l résolution numérique IPI des équtions suivntesX hns le dre de notre ollortion ve qeorgi ehD l9ssemlée de nnoruns de grphène été étudiée pr eiF v (gF fFV montre le iln de es étudesD où trois régions életroniquement di'érentes sont présentes sur es runs VWF ve grphène dont l normle à l surfe est @HHHIA est métllique et dopé nD omme ttendu IUSF r ontreD le grphène qui roît sur le sidewll @ve une normle de ∼ 30 • A est métllique et neutre @pnneu AD e qui indique qu9il est déouplé du sustrtF in revnheD le grphène qui des normles intermédiires une nde interdite d9u moins SHH me @pnneu AF v9origine de e gp été suggérée d9être dns le grphène qui roit sur l région ouré @en juneAF e(n de omprendre l9origine struturle de ette nde interdite ussi lrgeD nous vons ontrsté des études spetrosopiques à des études struturlesF xous vons d9ord étudié l struture du système pr wF ves imges à lrge éhelle montrent l9ssemlée omposée de plteuxD fettes et trnhées @(gF fFWA Y les runs se lolisent priniplement sur les fettes et ont des ords lisses et droitsF vorsqu9on fit un zoom sur l fette (110n)D on oserve l struture de nid d9eille du grphène et des vritions topogrphiques forts @(gF fFWAF v région @IA orrespond à l prtie sse de l trnhéeD où on oserve l présene d9un préurseur de grphène @u'er lyerAF v région @PA montre du grphène qui s9étend de l fette jusqu9u plteuF v région @QA montre du grphène qui s9étle sur le plteu @HHHIAF v oupe trnsversle pr iw d9un ensemle de nnoruns de grphène est montrée à l (gF fFIIF v9grndissement sur l fette (110n) @pnneu A permet Mots-clés : grphèneD nnostrutureD nde interditeD wD eiD iw Résumé : v9életronique sé sur le grphène fit fe à un verrou tehnologiqueD qui est l9sene d9une nde interdite @gpA permettnt une ommuttion entre les étts logiques llumé et éteintF ves nnoEruns de grphène rendent possile l9otention de e gp mis il est di0ile de produire de tels runs ve une lrgeur préise à l9éhelle tomique et des ords ien ordonnésF ve on(nement életronique est une fçon élégnte d9ouvrir un gp et peut en prinipe être réglé en justnt l lrgeur des nnoErunsF gette thèse est onsrée à l ompréhension de l9ouverture du gp pr nnoEstruturtionF xous vons suivis deux pprohes X l9introdution d9un potentiel superEpériodique sur le grphène pr des sustrts viinux de métux noles et le on(nement életronique dns des nnoEruns sur des fettes rti(ielles du igF hes potentiels superEpériodiques ont été introduits ve deux sustrts nnoEstruturésX l9sr@QQPA et un ristl ouré de t@IIIA multiEviinleF ve grphène modi(e les mrhes initiles des sustrts et les trnsforme en une suession de terrsses @IIIA et de régions d9umultion de mrhesD oservés pr wF v nnoEstruturtion du sustrt induit lors un potentiel superEpériodique dns le grphène entrînnt l9ouverture de gps sur l nde π du grphène oservée pr eiD e qui est ohérent ve l périodiité struturle oservé pr w et viihF ves gps peuvent être onvenlement expliqués pr un modèle de type hmiltonien de hirY e dernier nous permet de retrouver l fore du potentiel à l jontion entre les terrsses @IIIA et l région d9umultion des mrhesF v fore du potentiel dépends du sustrtD de l périodiité ssoiée à l surfe et du type de ord des mrhes @soit type e ou fAF xous vons ussi hngé le potentiel de surfe en interlnt du gu sur l9sr@QQPAD qui reste préférentiellement u niveu de l9umultion des mrhesF v surfe présente des régions dopées n lors que les régions nonEinterlées restent dopées pD onduisnt à une suession de runs dopés n et p pour une même ouhe de grphène ontinueF v seonde pprohe pour ontrôler le gp est pr on(nement életronique dns des nnoE runs de grphène synthétisés sur du igF ges runs sont otenus sur des fettes du ig ordonE nées périodiquementF gomme l9ouverture d9un gp d9origine inonnue vit été oservé pr eiD nous vons rélisé les premières études tomiquement résolues pr wF xous démontrons l réguE lrité et l hirlité des ordsD nous lolisons préisément les nnoruns de grphène sur les fettes et nous identi(ons des miniEfettes sur du igF e(n de omprendre le ouplge entre le grphène et le sustrtD nous vons étudié une oupe trnsversle pr iwGiivD en ompleE ment des études pr ei et wGF xous oservons que l fette @1107A où le grphène se trouve présente un suEfettge sur les extrémités hute et seF ve suEfettge omprend des miniEterres @HHHIA et des miniEfettes @1105AF ve grphène s9étend tout u long du l région suEfettéeD et est ouplé u sustrt dns les miniEterres @HHHIAD e qui le rend semiEonduteurF in revnheD le grphène uEdessus des miniEfettes @1105A est déouplé du sustrt mis présente un gp oservé pr iivD et omptile ve les oservtions fites pr eiF v9origine du gp est expliqué pr le on(nement életronique sur des nnoEruns de grphène de I E P nm de lrgeur lolisés sur es miniEfettes @1105AF Université Paris-Saclay Espace Technologique / Immeuble Discovery

cos (k x l) = cos (k 1 a) cos (k 2 b) + k 2 y h2 v 2 f + E • (E -V ) h2 v 2 f k 1 k 2 @IA ve les reltionsX k 1 = [V -E] 2 h2 v 2 f -k 2 y 1/2 @PA k 2 = E 2 -∆ 2 h2 v 2 f -k 2 y 1/2 @QA

  sur des surfaces nanostructurées de SiC et desdes surfaces vicinales de métaux nobles. hèse présentée et soutenue à intEeuinD le IH novemre PHITF gomposition

  Figure 1: (a) Scheme of a transistor with graphene as its main conduction channel ideally producing both on/o states, represented by 1-0. (b) Electronic band diagram from ideal and semiconducting graphene. On ideal graphene, the on state is always present, as electrons can move freely from the valence to the conduction band. On semiconducting graphene, by opening a band gap we can obtain both the on (conductive) and o (non-conductive) states.

  struture nd the origin of the nd gpF fy performing vriE ous mirosopi nd spetrosopi mesurementsD we onlude tht the system onsists of ontinuous grphene lyer sudivided in lrge metlli nnorion on sidewll ig fet ordered y semionduting minirionsF hese IEP nm wide semiondutE ing nnorions re responsile for the nd gp opening vi eletroni on(nementF hese results re presented in hpter SF he mnusript ends with the onlusionsD where we present summry of the wys of opening nd gps on grpheneD s well s the perspetives of my workF and electronic properties qrphene onsists of single lyer of ron toms in honeyom rrngement with

Figure 1

 1 Figure 1.1: (a) Real lattice of graphene with hexagonal symmetry and two atoms per unit cell, (b) Four Brillouin zones showing the main high symmetry directions of reciprocal space (Γ M = 1.475 Å -1 and

  Figure 1.2: Electronic band structure of graphene around E f in the tight-binding approximation with hopping parameters t = 2.7eV and t = 0.2t [14].

Figure 1 . 3 :

 13 Figure 1.3: Theoretical properties of graphene nanoribbons. (a) Top: representation of a zigzag (left) and armchair nanoribbon (right). The arrows indicate the long direction of the ribbons. Bottom: scheme indicating the direction where the electronic structure in (b) was calculated. The left panel is the real space representing graphene and the right panel is its reciprocal space. The rectangular unit cell for calculations is dened by a and z. (b) Electronic band structure calculated by tight-binding for various graphene nanoribbon widths (N = 4, 5, 6, as dened in (a)). Top row: zigzag nanoribbons have a metallic state at E = 0. Bottom row: armchair nanoribbons exhibit either metallic or semiconducting behaviors, depending on the presence of an edge state at E f (metallic states in the red box). The band gap is width-dependent [12]. (c) Density functional theory (DFT) calculations showing an oscillation of the band gap as a function of the ribbon width in functionalized armchair nanoribbons [15]. (d) ab initio calculation of the spin-resolved density of states (DOS) (top) and local DOS (bottom) of zigzag nanoribbons in the absence of an electric eld (left). In the presence of a transverse electric eld (right), the band at E f is spin-polarized [16].

Figure 1 . 4 :

 14 Figure 1.4: Lithographic ribbons. (a) Oxygen-plasma-patterned graphene nanoribbons with a nanowire protecting mask. Top panel: graphene is deposited on a substrate and nanowires are placed on top. An oxygen plasma etches away the unprotected graphene. The wires are removed and the nanoribbons are revealed on the substrate. Bottom panel: scanning tunneling microscope (STM) images of these nanoribbons [26]. (b) Microscopy images of lithographically-patterned graphene ribbons. Top panel: scanning electron microscopy (SEM) image showing the nanoribbon covered with the polystyrene etching mask resist. Bottom panel: cross-sectional transmission electron microscopy (TEM) image showing the ribbons with the polystyrene (PS) resist mask on top and a protecting platinum layer [27]. (c) E-beam lithographically-patterned graphene nanoribbons on SiC. Overall topography of the ribbon as seen by a STM (left) and zoom on the edge (rectangle) with atomic resolution (right) [-1.6 V, 0.1 nA].

  Figure 1.7: Graphene nanoribbon obtained by cutting with catalytic particles. Left: Model of paths made by metallic particles when cutting graphene by a catalytic reaction. Nanoribbons can be as narrow as 10 nm and display preferential zigzag edges. Right: AFM phase contrast image, showing the resulting patterns that include ribbons, triangles and rhombus [58].

  Figure 1.13: All graphene pn junctions. (a) Schematics of a graphene theoretical heterojunction, where the left part is p-doped and the right part is n-doped. Below the LDOS along the ribbon axis, as calculated by DFT, allows to visualize the pn junction [84]. (b) Color-coded SEM image of the n-(blue) and p-(green) doped areas obtained by the intercalation of one (two, respectively) layer of Ge at the interface between SiC and epitaxial graphene, as sketched in the bottom panel [91].

  Figure 1.14: Devices. (a) A chip with multiple electrodes connected to a suspended graphene nanoribbon obtained by TEM lithography [41]. (b) FET device obtained by e-beam lithography patterning. The graphene nanoribbons are contacted by Pd electrodes [29]. (c) A 50 graphene nanoribbons FET array developed from CVD graphene on a catalyst template. The inset shows the four-electrode contact conguration [66].

  Figure 2.1: (a) Main elements of a Scanning Tunneling Microscope. The three piezo scanner is controlled by the applied bias to scan over the sample. By detecting the tunneling current between the tip and the sample, an STM image is generated [103, 104]. (b) Electron quantum tunneling eect principle applied for STM measurements. The bias eV is applied to the sample so that electrons can tunnel through the barrier given by the workfunction φ in vacuum and towards the tip [103]. The wavefunction can tunnel through the barrier even if its energy it's lower than the barrier height.

Figure 2

 2 Figure 2.2: (a) Constant height mode, where the changes in tunneling current are measured along the surface while the height is kept constant. (b) Constant current mode, where the tunneling current is kept constant and the changes in height are recorded.

Figure 2 . 3 :

 23 Figure 2.3: Band diagram, I-V and dI/dV typical STS curves for a metal and a semiconductor [105].

  Figure 2.4: (a) Scheme showing the angular range to obtain the BF, LAADF and HAADF imaging modes of STEM [106]. (b) STEM image of a planar V O 2 thin lm probed by the dierent modes [107].

Figure 2

 2 Figure 2.5: Typical EELS spectra for a ctional material showing the low and high energy loss regimes, where weakly and tightly bounded electron interactions can be found [106].

Figure 2

 2 Figure 2.6: (a) Scheme of the ARPES conguration [111]. (b) E(k) map for a Au(111) surface [112]. (c) Energy Distribution Curves for the band dispersion on (b). Each line corresponds to an individual spectrum at a dierent emission angle.

Figure 2

 2 Figure 2.7: (a) Band dispersion along k x and k y for a parabolic band. (b) Constant energy cut of a parabollic band. Band dispersion as a function of (c) k x and (d) k y .

Figure 3

 3 Figure 3.1: (a)-(b) LEED patterns of graphene growth on Ir(111) at dierent growth temperatures. (a) shows a wide variety of rotational domains with respect to iridium, named after their angle of rotation, while (b) presents only two rotational domains, namely R0 and R30 [118]. (c) STM image of a Gr/Ir(111) surface where three rotational domains coexist in a continuous graphene layer (108 nm × 108 nm). (d) Sketch where the three rotational domains are identied. The white borders represent the boundary of each domain, that extends across the terrace edges (yellow lines) [121].

Figure 3 . 3 :

 33 Figure 3.3: Clean Ir(332) structure. (a) Sketch of the pristine Ir(332) surface, with 1.25 nm terraces along the 101 and periodic along the 121 direction [114]. (b) LEED pattern of Ir(332) at 148 eV showing the splitting of the Ir (1x1) spots due to the periodicity of the terraces. The dierence between the red and blue spots gives a terrace size L = 1.8 ±0.2 nm along the 121 direction. (c) STM image on the clean Ir(332) vicinal surface [1 V, 0.5 nA]. Insets shows two methods to obtain the terrace width: A general estimate through a Fast Fourier Transform of the STM image (L = 1.2 ±0.2 nm) and the terrace width distribution of the STM image (L = 1.2 ±0.3 nm).

3. 1 .

 1 GROWTH AND STRUCTURE OF GR ON IR(332) RS perpendiulrly to the steps in order to detet step edges nd determine the terre size with the histogrm of the terre widthsF his method gives distriution where L = 1.2 ±0.3 nmF he pp imge nd the histogrm otined y h re presented on the inset in (gF QFQF he di'erene etween the vlues otined y viih nd w n e explined y the lol nture of wD where imges re typilly of surfes ∼ 3000 nm 2 D while viih verges over ∼ I mm 2 with oherene of ∼ IHH nm 2 F 3.1.2 Temperature programmed growth onIr(332)

Figure 3 . 4 :

 34 Figure 3.4: Dosage vs. substrate annealing temperature for dierent TPG preparations. The orange line indicates the dosages and temperatures where graphene appears. The cross and square symbols represent samples obtained in a single TPG cycle. The triangle, diamond and circle represent series of consecutive TPG cycles. The red square marks the rst appearance of graphene, while the green diamond marks the optimal preparation.

Figure 3 . 5 :

 35 Figure 3.5: Characterization of the initial graphene growth obtained after one TPG cycle at an eective dosage of 6.75 ±0.14 L. (a) LEED with an incoming electron beam of 34 eV showing the (1x1) spots of Ir and R0 graphene spots. Inset shows the moiré spots around the R0 spot of graphene. (b) STM image showing the rst stages of graphene growth on Ir(332) [1 V, 1.1 nA]. The pristine Ir(111) steps begin to coalesce and form step bunching in various degrees of completion (partial or full), shown by the arrows. Graphene appears on the wider terraces associated to full step bunching.

Figure 3 . 6 :

 36 Figure 3.6: Coverage vs. eective dosage for dierent TPG preparations. The orange line shows the boundary of graphene formation. Red triangles represent samples obtained with one TPG cycle while blue circles were obtained after two or more cycles. Insets show STM images of the surface as the coverage increases (left to right:[1 V, 1.1 nA],[1 V, 0.5 nA], [1 V, 0.6 nA], [1 V, 0.6 nA], [1 V, 0.5 nA]).

Figure 3 . 7 :

 37 Figure 3.7: Characterization of the optimal preparation. (a) STM image showing the Gr/Ir(332) sample obtained after three TPG cycles with an eective dosage of 1014 ±1 L [1 V, 0.6 nA]. (b) Green areas represent the graphene areas in (a). These areas do not extend across the whole length of the terrace. Inset shows atomic resolution of the graphene R0 domain on a terrace.

Figure 3 . 8 :

 38 Figure 3.8: Continuity of graphene between step bunching and terraces. (a) 3D STM image [10 mV, 36 nA] of a boundary between a at terrace and two step bunching areas. The continuity of the graphene network is indicated by arrows. The green point shows where the spectroscopy data in (b) was taken, while (c) is extracted from a previous experiment on Gr/Ir(111) performed in the same preparation chamber [134]. (b) STS shows three features: F 1 between -0.25 V and -0.5 V (associated to surface state S1), F 2 around +0.6 V (unoccupied states) and the dirac point (E Ir D ) around +0.25 V, indicating p-doping. (c) STS on Gr/Ir(111) [134] showing the same F1, F2 and E Ir D features than Gr/Ir(332).

Figure 3

 3 Figure 3.9: (a) STM image of an intermediate stage of graphene growth after three TPG cycles with an eective dosage of 1455 ±15 L [1 V, 0.6 nA]. Step bunching areas (orange) fully display a periodicity similar to the moiré of graphene. Overgrown graphene (green), occupies a fraction of the (111) terraces, while the majority of the terraces are bare iridium (brown). (b) Model for the intermediate stage: Graphene is present on the step bunching area and slightly overgrown on the (111) terrace, producing a network of discontinuous graphene nanoribbons. The spatial discontinuity is seen by graphene as an innite potential barrier at both sides of each nanoribbon.

  3.1. GROWTH AND STRUCTURE OF GR ON IR(332) SI 3.1.3 Chemical vapor deposition forIr(332)

Figure 3 .

 3 Figure 3.10: Dosage vs. temperature for dierent CVD preparations. Blue symbols show the evolution of the preparations, while the red rhombus shows the optimal preparation. (a)-(d) LEED of the blue square (232 eV beam energy), triangle (66 eV beam energy), star (66 eV beam energy) and red rhombus (66 eV beam energy) respectively. (a) Ir (1x1) spots and a diuse background are present, but there is no graphene signal. (b) R0 graphene spots are visible along with a diuse arc representative of multi-domain graphene. (c) R0, R25 and R35 graphene spot are visible, in addition to a graphene arc.(d) LEED of the optimal preparation, further analyzed in g. 3.11.

Figure 3 .

 3 Figure 3.11: Characterization of the optimal CVD sample (810 • C and 67.5 ±0.1 L). (a) LEED image at an incoming electron beam of 63 eV. Blue/pink/red arrows represent graphene, moiré and Ir spots respectively. Inset shows the Ir splitting (due to a superperiodic structure) and the moiré. (b) STM images of the graphene domains in (a). Upper and middle panel show the R0 and R30 domains [1 V, 2 nA]. The pink rhombus indicate the unit cells of the graphene moiré aligned with the 101 direction. The bottom panel is composed image for the R25/R35 domain. Center: STM image where both the graphene network and the moiré pattern are present [5 mV, 29 nA]. Left: Filtered image with moiré unit cell in pink. Right: Filtered image with graphene unit cell in green.

  Figure 3.12: (a) STM image of the optimal CVD sample [0.9 V, 0.5 nA]. Terrace (T) and Step bunching (SB) areas indicated on the surface. (b) FFT of (a) resulting in a superperiodicity of 6.8 ± 0.6 nm. (c) Terrace width distribution histogram of the surface resulting in a terrace size of 3.5 ± 0.5 nm.

Figure 3 .

 3 Figure 3.13: (a) Model for the innite potential barrier between discontinuous graphene nanoribbons on the Ir(332) surface. (b) Model for the nite potential barrier created by the step bunching on a continuous carpet of graphene.

Figure 3 .

 3 Figure 3.14: (a) Mechanism of Cu intercalation between the Gr and Ir(111) surface. Step 0 -Initial Gr/Ir(111) surface. Step 1 -Intercalation of Cu begins at step edges and terraces. Step 2 -Cu clusters grow on nucleated sites. Step 3 -Growth continues until monolayer coverage. Then, Cu in excess forms nanoislands on the Gr surface. (b)(c)(d) STM images corresponding to step 1 (0.12 ML), 2 (0.31 ML) and 3 (0.86 ML) respectively. Insets show the same STM image where it is indicated in yellow the regions where the moiré demonstrates that Cu has been intercalated [131].

  Figure 3.15: STM image of the terraces and the step-bunching areas (a) before [0.9 V, 0.5 nA] and (b) after intercalation of 0.9 ML of Cu [50 mV, 0.9 nA]. The inset shows the R0 rotation of graphene in the terrace. The blue rhombus shows the moiré unit cell of this domain. (c) STS curves performed on the areas indicated in (a) with a blue (terrace) and a green (step-bunching) circle, both indicating an n-doping of ∼ -0.6 V.

Figure 3 .

 3 Figure 3.16: (a) 10 nm x 10 nm STM image showing the at terraces and the step-bunching areas after intercalation of 0.45 ML of Cu [0.1 V, 2 nA]. Inset shows that graphene has a R30 orientation with respect to iridium, therefore the (2x2) Gr moiré unit cell of 0.492 nm is not visible neither on the terraces (T) nor on the step bunching (SB) due to its small size. The orange and blue circles indicate where spectra in (b) were acquired. (b) On the terrace we can see the F1 state at ∼ -0.25 V and the dirac point is at ∼ +0.1 V (E Ir D ), typical of the p-doping of Gr/Ir(332). On the step-bunching, the

  Figure 3.17: (a) E(k) scheme for a parabolic band and the Umklapp replicas due to the periodic nature of the system given by the G vector (2π/L). (b) E(k) scheme showing the E g band gap opening at the new Brillouin zone edges G/2 = ±π/L (crossing between the initial band and Umklapps).

Figure 3 .

 3 Figure 3.18: E(k) scheme showing the electronic connement on a parabolic band (red dotted line) on a superperiodic system associated to a G vector (2π/L). (a) Partial connement induced by a nite periodic potential resulting in the black sinusoidal dispersing bands. (b) Total electronic connement induced by an innite periodic potential resulting in black at bands.

Figure 3 .

 3 Figure 3.19: Model of a two-dimensional Dirac hamiltonian applied to graphene stripes with a periodicity l = a + b. The dierent regions are characterized by dierent fermi velocities (v a and v b ) and gaps ∆ a and ∆ b .

  Figure 3.20: (a) Sketch of the superperiodic surface, showing the angular range of detected intensity for the terraces (∆θ T err ) and step-bunching (∆θ SB ) areas. (b) k x vs. k y map at the Fermi Level showing the traces of the dierent rotational domains of graphene (R30, R25/R35) as well as R0, coming from the terrace and step bunching areas. Some bands of the substrate are also visible (hν = 150 eV). (c)(d) E vs. k x cut along the dotted lines in (b), where the cones of the R30 and R25/R35 domain are highlighted by dotted black lines. The reciprocal space is represented in terms of angles.

.

  Figure 3.21: (a) E(k) map of Gr/Ir(332) at the K point of the R0 rotation coming from the terraces (hν = 36 eV of excitation photon energy). The green bands are the S1, S2 and I iridium surface states, also shown on the line prole at 0.6 Å -1 . The blue bands are graphene bands (R25, R35 and R30). The black line is the R0 graphene band, that allows to appreciate a doping of 330 meV in agreement with previous results [122, 125, 126, 134, 136, 158]. (b) First derivative of (a). Three band gaps are marked by the pink arrows. (c) Energy distribution curves of (a) every 0.58 • along the K -M direction, where the maxima of the bands are followed with vertical lines. The black arrows show the location of the band gaps with E g = 390 ± 20 meV and a separation in energy between the gaps of 0.60 ± 0.06 eV and in reciprocal space by a G/2 vector of 0.09 ± 0.02 Å -1.

Figure 3 .

 3 Figure 3.23: Model of the Gr/Ir(332) band structure (red dotted line) tted with a two dimensional Dirac hamiltonian on a superlattice with parameters: a = 3.3 nm, b = 0.2 nm and V = 0.33 eV. The recovered strength of the potential is 4.4 eV Å, which recreates the band gap opening of 390 meV (green arrows).

•

  Figure 4.1: (a) LEED pattern of Gr/Pt(111) where some well dened domains (R0, R30) are present. The pattern also exhibits some arcs corresponding to rotational domains very close in angle. (b) STM image showing the continuity of graphene between two Pt(111) terraces. The moiré preserves the same orientation on both sides of the step edge. On the lower terrace, two rotational domains coexist. The prole along the red line shows the dierent corrugations of the two moiré (C orr 1 and Corr 2 ) [167]. (c) STM image showing the discontinuity of graphene grown on Pt(311). The blue and green rectangles correspond to the dierent facets of the surface. (d) Zoom on the blue area on panel (c), where the yellow dots highlight a periodic pattern, attributed to graphene. (e) Zoom on the green area, where no periodic features are observed, similar to bare Pt(111) on panel (f ) [1 V, 0.8 nA] [168].

Figure 4

 4 Figure 4.2: (a) Scheme of the curved Pt crystal. The Pt(111) orientation is found at the center (vicinal angle = 0 • , x = 0 mm), and as we move further away from the center up to a tilt of 16 • towards the 112 or 112 directions, the vicinal surfaces present A or B step edges respectively. The steps of the vicinal surfaces run along the 110 direction. (b) Image of the curved Pt crystal, where the center of the sample is referred as vicinal angle 0 • , while the side with A-steps or B-steps are referred with negative or positive values respectively, measured in vicinal angle with respect to the [111] direction. (c) Schematic of the Pt(111) surface and the geometry of A-step and B-steps. LEED images at incoming electron beam of 128 eV as for vicinal angles (d) -11 • , (f ) -7 • , (h) 0 • , (k) +7 • and (n) +11 • . The terrace size decreases away from the center. The LEED splitting associated to the vicinality is sharp on the A-steps side and blurred on the B-steps side. STM images corresponding to vicinal angles (e) -11 • , (g) -7 • , (j) 0 • , (m) +7 • and (p) +11 • [1 V, 0.8 nA]. At vicinal angle 0 • , the Pt(111) large terraces are recovered, while at both sides of the sample, the terrace size decreases.

4. 1 .

 1 GROWTH AND STRUCTURE OF GRAPHENE ON PT US distriution of terres nd lower ordering of the surfeF he qulity derese is lso oserved on the w imges in pnels m nd pF hespite this disorder oserved in wD the terre size n e lulted y viih rehing L = 1.7 ±0.3 nm nd L = 1.2 ±0.2 nm for the +7 • nd +11 • viinl ngles respetivelyD in greement with the expeted viinl surfeF 4.1.2 Graphene growth on curved Pt by chemical vapor deposition

Figure 4

 4 Figure 4.3: LEED (left), 3D STM (center) and details of the STM images (right) for vicinal angles (a) -11 • [1.14 V, 0.7 nA], (b) -7 • [100 mV, 2.8 nA], (c) -3.5 • [70 mV, 2.6 nA], (d) 0 • [360 mV, 2.6 nA], (e) +3.5 • [1 V, 0.8 nA], (f ) +7 • [1 V, 0.5 nA] and (g) +11 • [1 V, 0.8 nA]. Three main graphene features appear: R30, equivalent R5/R5' rotations and multidomain arcs. The A-steps side(a-c) presents a gradual splitting on the Pt spot, indicating the formation of a well ordered periodic system, whose period L (terraces + step bunching) varies from 6.8 to 5.7 ± 1.4 nm obtained by PWD histograms. The B-steps side (e-g) does not show the Pt spot splitting in LEED, although STM images and PWD histograms conrm that there is a certain degree of order. Atomic resolution images suggest the continuity of graphene, as the graphene honeycomb on the blue terraces is oriented in the same way at both sides of the orange step bunching area. The white rhombus highlights the unit cells of moirés. Appendix A.3 shows the zoom of panels a-c.

Figure 4

 4 Figure 4.4: E(k) maps of graphene for the vicinal angles (a) -5.5 • , (b) -2 • and (c) +2 • . The same data with indications of the dierent spectral features are shown for vicinal angles (d) -5.5 • , (e) -2 • and (f ) +2 • . The green bands show the R5/R5' rotational domains with a dierent p-doping at every vicinal angle. The cyan band at 2.5 eV is the saddle point of the π band from the R30 domain. The black band is a Pt(111) bulk band. The pink features mark the three gaps due to the crossing between the main band and the Umklapps. (g)-(i) EDC curves showing the gap opening of the second band gap. (k) Scheme of Umklapps bands due to the superperiodicity induced by the step arrays.

  regions a nd b hnges with the viinl ngle @320 meD 290 me nd 250 me for -5.5 • D -2 • nd +2 • respetivelyAF e sizle gp opening in the oundry etween the terres nd the step unhing @bA mimis the potentil rrierD therefore ∆ b = ∆D while everywhere else ∆ a = 0F e gin (nd the numeril solution of eqnsF QFIRD QFIS nd QFIT in the region of interest round the

Figure 4

 4 Figure 4.5: (a) Physical representation of the parameters on the two-dimensional Dirac-hamiltonian model for graphene under a periodicity l = a + b, where a is the average width of the (111) terrace or the step bunching facet and b is the junction of a few Å wide. The fermi velocity is preserved on both regions (v a = v b = v f ). The doping on regions a and b is 320 meV, 290 meV and 250 meV for vicinal angles -5.5 • , -2 • and +2 • respectively. A gap in region b mimics the potential barrier at the limit between terraces and step bunching (∆ b = ∆), while no gap is present in region a (∆ a = 0). Superimposed yellow bands obtained from the Dirac-hamiltonian model on top of the ARPES map for vicinal angles (b) -5.5 • , (c) -2 • and (d) +2 • . The calculated bands correspond to the parameters: (b) a = 3.0 nm, b = 0.2 nm and a potential of 3.35 eV Å; (c) a = 3.3 nm, b = 0.2 nm and a potential of 2.8 eV Å; (d) a = 3.3 nm, b = 0.2 nm and a potential of 1.8 eV Å, that reproduce the gap openings of 360 meV, 290 meV and 200 meV respectively.

Figure 4

 4 Figure 4.6: (a) Periodicity vs. vicinal angle (see the inset for the angle reference) as calculated by various techniques (LEED, TWD in STM, ARPES) and the Dirac-hamiltonian model. The trend is highlighted by the two enveloping green curves. The periodicity at the Pt(111) surface is not shown due to the absence of preferential orientation. (b) Calculated potential strength (U 0 b) vs. vicinal angle for the three angles on the multivicinal platinum crystal and on Ir(332). The pink enclosing correspondsto periodicities of 3.5 nm on A-and B-step side (-2 • and +2 • respectively). The green enclosing corresponds to periodicities of 3.5 nm on B-steps side on platinum (+2 • ) and iridium (+11 • ). The blue enclosing corresponds to periodicities 3.5 nm and 3.2 nm (-5.5 • and -2 • respectively) on the A-steps side.

4. 4

 4 Conclusions and perspectives e hve modi(ed the eletroni properties of grphene y growing it on nnostruE tured viinl sustrteF e hve explored the e'et of oth eEsteps nd fEsteps t viinl ngles etween +16 • to -16 • with respet to the III surfe normlF e hve performed study of the in)uene of the viinlity on the potentil rrier strength oth experimentlly nd y modeliztionF sn detilD with this study we hve underE stoodX • he growth nd the struture of grphene vi gh on urved t rystlX sn our growth onditionsD for overges lose to the monolyerD we hve grown ontinE uous lyer of grpheneF here re four min grphene rottionl dominsD nmely QHD S nd S9 s well s other domins orresponding to rottions etween 15 • nd 45 • D s indited y rs in viihF st hs een oserved tht the qulity of the step rry dereses fr wy from the [111] diretionF woreoverD the side with eEsteps results in more homogeneous step rrysD while most of the side with fEsteps presents wiggly edgesD giving rise to nonEhomogeneous struturesF• he e'ets of the strutured sustrte on the grphene eletroni nd strutureX e studied the eletroni properties of grphene in di'erent viinl surfes y eiF e oserved there nd gps di'ering in their mplitude nd their @iDkA positionF fy omining w nd ei results s n input for hirEhmiltonin modelD we explin the oserved nd gpsF he origin of the gps omes from the superperiodiE ity indued y the step rryF he modeling llows to retrieve the potentil strength t the juntions etween the @IIIA terres nd step unhing tht leds to prtil on(nement on grphene nd nd gp openingF he study of the on(nement s funtion of the viinl ngle llows to relte the struture to the on(ning potentilF 4.4. CONCLUSIONS AND PERSPECTIVES VS he potentil strength inreses roughly s funtion of the viinl ngleF woreoverD we oserve di'erent ehvior depending on the step edgeD s there is di'erene in the potentil etween eE nd fEstepsF edditionllyD the potentil strength gretly hnges in iridium or pltinumD inditing n importnt ontriution from the interE tion etween grphene nd the sustrteF pinllyD we oserve how it is possile to ontrol the potentil y hnging the periodiity of the nnostruturtionF ixiting perspetives pper from our studyF hisontinuous grphene nnorions ould proly e hieved with lower ethylene dosgesF elsoD the stility of fEsteps ould e improved y hnging the growth prmeters leding to higher on(ning poE tentilsF pinllyD other surfes with di'erent viinl ngles nd orienttions deserve to e exploredD suh s the (311) @viinl ngle of IVFRQ • towrds the 110 diretion with respet to the [111] diretionAD where disontinuous growth of grphene is expeted to hppenF Chapter 5

  Figure 5.1: (a) 4H-SiC(0001) wafer after lithography of deep trenches parallel to the 1120 direction of SiC to produce armchair nanoribbons. The perpendicular 1100 direction of SiC that produces zigzag nanoribbons is also shown. (b) Array of graphene nanoribbons through the stabilization of the vertical (1100) and (1100) walls into the stable (110n) and (110n) sidewalls after a rst annealing. A second annealing promotes the nanoribbon growth on the sidewalls.

  Figure 5.2: Array of slightly overgrown graphene armchair nanoribbons probed by ARPES. Three regions with dierent surface normal are shown: SiC(0001) (0 • ), sidewalls nanoribbons (∼ 30 • ) and a transition region (10 • -25 • ) whose orientation is compatible with curved areas at the top or bottom of the sidewall nanoribbons (highlighted in yellow). (a) Metallic n-doped overgrown graphene on SiC(0001). (b) Transition region exhibiting a band gap of at least 500 meV. (c) Neutral metallic graphene indicative of decoupled graphene at the sidewalls [89].

5. 2 .

 2 Figure 5.3: 3D STM images for (a) armchair [1.1 V, 0.7 nA] and (b) zigzag [-1.5 V, 0.25 nA] sidewall nanoribbons at large scale. The edge of the armchair sidewall nanoribbons is straight, while the zigzag refacets into more stable armchair directions. (c) Cylindrical SiC pillars of dierent sizes after an annealing that refacets the edges of the pillars. For the smaller pillar, armchair edges are preferred. For larger pillars, zigzag edges can be obtained mixed with armchair edges [174].

Figure 5

 5 Figure 5.4: STM and STS performed on zigzag sidewall nanoribbons. Atomic resolution on the (a) upper [-1.5 V, 0.25 nA] and (b) lower [-1.5 V, 0.25 nA] edges. Moiré structures corresponding to a buer layer on SiC(0001) on the (c) plateau [1 V, 0.25 nA] and (e) trench [-1.5 V, 0.25 nA]. The spectroscopic signal for the (f ) plateau and (h) trench show the typical semiconducting behavior of the buer layer. (d) Atomic resolved image on the zigzag sidewall nanoribbon [-1.5 V, 0.25 nA], whose orientation is preserved from edge to edge. (g) STS showing the characteristic spectrum of undoped graphene [86].

  Figure 5.6: Ideal slab of some hundreds of nm thick obtained by the standard thinning procedure for a LaAlO 3 /SrT iO 3 interface. The electrons pass through the sample and a projected image of atomic resolution is recovered on the CCD camera [177].

  Figure 5.8: (a) Single slab where faces A and B are identied in order to perform further mechanical polishing. (b) Slab after thinning by dierent diamond grinding papers, where a 1 • angle allows to obtain a wedge shape. The thicker end of the wedge is 1 mm thick, while the thin end of the wedge is ∼ 300 nm in width. (c) Optical microscope image of the obtained wedge sample, where a portion of the sandwich has been taken away by the mechanical polishing, however we can appreciate the ∼ 300 nm thick end of the wedge by the appearance of optical fringes (inset). (d) Thinned wedge nanoribbons sample glued to the Cu STEM grid. The thick part is glued to the edge of the grid, while the thin part will be suspended in the middle of the grid.

Figure 5 . 9 :

 59 Figure 5.9: Graphene nanoribbons sample (3 mm × 1mm × ∼ 100 nm) is further thinned by ion bombardment, as shown by the further appearance of optical fringes monitored with a pink lter. The ion bombardment process is stopped when interference fringes appear on the nanoribbon area.

5. 3 .

 3 Figure 5.11: (a) Cross sectional TEM image of the array of ribbons with a distance between plateaus of 300 nm. (b) Zoom on the (110n) facet, showing two families of facets. The rst is the extended (1107) surface where the armchair sidewall nanoribbon is grown at a normal rotated ∼ 30 • from the SiC normal, and the second is a ripple-like structure in the upper and lower part of the extended facet at normals rotated ∼ 12-25 • from the SiC normal. (c)(d) A zoom on one of the ripple structures shows afaceting of the SiC substrate into miniterraces and minifacets. The distance of coupled graphene to the miniterrace is 0.23 nm, similar to the buer layer on SiC(0001). The distance between the decoupled miniribbon and the minifacet is 0.40 nm, larger than on graphite, so a decoupling from the substrate is expected. (e) A zoom on the green square on panel (b) shows a colorized image where graphene is in green and SiC in red. A large armchair nanoribbon larger than 20 nm extends over the sidewall facet, continues upwards following the supplementary faceting of SiC (minifacets and miniterraces) until arriving to the (0001) SiC surface. The given angles and distances were calculated for the decoupled miniribbons. In average their normals vary from ∼ 12 to 25 • and their width is between 1-2 nm.

  Figure 5.12: (a) STEM image of the region studied by EELS at the carbon K-edge. The region exhibits a graphene monolayer at the boundary between the plateau and sidewall. (b) Zoom of the red rectangle in (a) indicating the four regions chosen for STEM-EELS spectromicroscopy measurements in (c). (c) Raw spectra extracted from (1) the buer layer, (2) the rst miniribbon, (3) graphene on the miniterrace and (4) bulk SiC. Component A and B spectra represent the main spectral components related to the carbon layer at the surface of SiC. Spectra 1-3 show the features of component A (graphite-like), while only spectrum 1 and 3 show an additional feature marked by the blue arrow corresponding to component B (highly coupled graphene). (d) Spatial location of component A present on the single carbon layer. (e) Spatial location of component B, present on the semiconducting buer layer and coupled graphene on the miniterraces. (f ) Pseudocolor image where gray enhances the SiC and cyan highlights the decoupled miniribbons.

Figure 5 .

 5 Figure 5.13: (a) STEM image use in EELS analysis at the carbon K-edge for bilayer graphene at the boundary between the plateau and sidewall. Boxes 5-6 indicate the regions where spectra have been extracted, namely the rst metallic graphene layer on SiC and the decoupled miniribbons, respectively. (b) EELS spectra showing an energy shift to higher energy of ca. 250 meV of the π * excitation for the decoupled miniribbon with respect to the metallic graphene.

  Figure 5.14: Modelization of the atomic structure and density of states. (a) Schematics of the model proposed for the general structure of armchair graphene ribbons grown on SiC(0001). The sidewall nanoribbon is found on the (1107) extended facet at 30 • o normal with respect to the SiC (0001) plane. Above and below the sidewall, a series of regions composed of minifacets and miniterraces exhibiting normals tilted ∼ 20 • from the (0001) plane are found. In the graphene on the minifacets, graphene is bonded to the substrate, while graphene on the miniterraces is oating without any strain and exhibits a band gap. The band gap is due to the quantum connement in the miniribbon. (b) Relaxed atomic positions of single-layer graphene miniribbons at SiC facet with [0001] and [1105] normals. (c) Density of states at the positions indicated in (b). Top panel: gapped and doped buer layer with some interface states in the gap. Bottom panel: oating graphene in the electronically decoupled miniribbon.

  Figure B.2: (a) Schéma montrant la dispersion E(k) parabolique d'électrons libres (en noir) ainsi que des Umklapp (en bleu) dus à une superpériodicité L correspondant au vecteur de l'espace réciproque G =(2π/L). (b) Schéma montrant la dispersion E(k) près du nouveau bord de zone à G/2 = ±(π/L) (au croisement entre la bande parabolique initiale et les Umklapps).

Figure

  Figure B.3: : (a) Schéma de la surface idéale d'Ir(332) avec des marches de 1.25 nm qui s'étendent le long de la direction 101 et qui introduisent une périodicité dans la direction 121 [114]. (b) Schéma du cristal multivicinal Pt(111). On trouve l'orientation (111) au centre du cristal (angle vicinal = 0 • ). Lorsqu'on s'éloigne du centre vers les directions 112 ou 112 , la surface présente des bords de marche de type A ou B. Les marches s'étendent le long de la direction 110 . (c) Schéma de la surface de Pt(111) et de la géométrie des bords de marches de type A et B.

  Figure B.4: (a) Image de microscopie à eet tunnel de graphène sur Ir(332) produit par CVD [0.9 V, 0.5 nA]. La surface est reconstruite avec des zones de marches (111) (T -terrasses) et des accumulations de marches (SB Step Bunching), indiqués sur l'image. (b) Image STM 3D du cristal multivicinal de Pt(111) pour un angle vicinal ∼ -7 • . La surface présente aussi une reconstruction périodique avec des zones de terrasses (111) et des accumulations de marches.

Figure B. 5 :

 5 Figure B.5: (a) Structure électronique étudiée par ARPES pour le système Gr/Ir(332). La courbe obtenue par l' hamiltonien de Dirac (ligne pointillé rouge) est superposée. Le potentiel associé à la superpériodicité correspondante est 4.4 eV Å. La structure électronique étudiée par ARPES pour graphène sur Pt(111) multivicinal est montrée pour trois angles d'orientations diérentes par rapport à la direction (111) : (b) -5.5 • , (c) -2 • et (d) +2 • . Les courbes obtenues avec l'hamiltonien de Dirac sont superposées (lignes pointillées jaunes) et correspondent à des barrières de potentiel de (b) 3.35 eV Å, (c) 2.8 eV Å et (d) 1.8 eV Å.

Figure B. 8 :

 8 Figure B.8: Nanorubans de graphène de type armchair étudiés par ARPES. Trois régions avec des propriétés diérentes du graphène sont observées : le graphène sur le SiC(0001) (normal à 0 • ), graphène sur les sidewalls (normal à ∼ 30 • ) et une région de transition (avec normal entre 10 • -25 • ). (a) Dispersion du graphène mesurée dans la région de normale 0 • . Le graphène ici est métallique, dopé n. (b) Dispersion du graphène mesurée dans la région de transition. Le graphène ici a une bande interdite d'au moins 500 meV. (c) Dispersion du graphène mesurée sur les sidewalls. Le graphène ici est métallique et neutre, ce qui indique un découplage du substrat [89].

Figure B. 10 :

 10 Figure B.10: Schéma de la mesure par microscopie électronique à transmission. Un faisceau d'électrons (èches oranges) traverse les nanorubans de graphène sur SiC après avoir été amincis et collés en sandwich. Finalement la projection latérale des atomes est récupérée sur une camera CCD.

  photoemissionF Physical Review BD VRXHUSRPUD PHIIF

Table 1 .

 1 1: Band gap and structural properties.

		Fabrication
		methods	Orientation	Width(nm)			Gap(meV)
	Top-down	Conventional	Not specied 4 -500	[26, 27, 29, 77], [3136], 4 -500	[26, 29, 31], [34, 74]
		lithography				[28, 65, 7174, 78]
		Local Probe	Not specied 0.7 -12	[41, 42]		100 -500	[40, 42]
		lithography
			AC		2.5	[40]
		Chemical	Not specied 3 -300	[46, 48, 79]		10 -400	[46]
		Unzipping	Not specied 10 -300	[51, 5355, 80, 81]	10 -50	[49, 51]
		CNTs
			Chiral		80 -200	[49]
		Particle cutting Not specied >10	[59, 60]		120 -1600	[82]
			ZZ		>1.1	[58, 82]
	Bottom-up Molecular	AC		0.7 -13	[6163, 72, 83]	1300 -3100	[44, 50, 62]
		precursor-based
			ZZ		1	[50]		[63, 7276, 84]
		CVD	Not specied 20 -3000	[64, 66, 67]		50 -58.5	[64, 66]
		Epitaxial	Not specied 900	[85]		-
		graphene
	Epi	Epitaxial	ZZ		40	[86, 87]		-
		sidewall
			AC		2 -40	[8890]		>500	[88]
	Notes: Listed gap values are either transport gaps or band gaps. True band gaps are listed for local probe lithography
	(STS measurements [40, 42]) and molecular precursor (PES-IPES [44, 62], optical absorption [50], STS [32, 84]) and un-
	zipping CNTs (STS [49]) and epitaxial graphene (ARPES [88]). All others are transport measurements. Epi refers to
	graphene grown on SiC sidewalls as it will be discussed in chapter 5.
	Table 1.2: Reported on/o ratio and transport properties for ribbons prepared with various processes.
		Fabrication methods	On/O ratio		Resistance (KΩ)	Mobility (cm 2 (V•s) -1 )
	Top-down	Conventional lithography	5 -1000 RT	[26, 35] 30 -670	[29]	0.21 -6000	[29, 71]
						[34, 65]		[35, 65]
		Local probe lithography	-		[41]	100	[41]	-	[41]
		Chemical		10 7 RT	[46]	-	[46]	100 -200	[46]
		Unzipping CNTs		10 -100 RT	[54]	2	[51]	0.1 -1500	[51, 54]
								[81]
	Bottom-up Molecular precursor-based -			-	150 -150,000	[50]
		CVD		2 -15,000 RT, LT	[64, 66] 100	[67]	40 -1000	[64, 66]
						[67]		[67]
		Epitaxial graphene	5 • 10 6 RT	[38, 85] 10	[85]	10 -1000	[38, 85]
	Epi	Epitaxial sidewall		-			7 -26	[87, 90] 2700	[90]
								[86]	Ballistic	[86]

  IPU d9identi(er une orrugtion similire à elle oservée préédemment en w dns les prties hute et sse de l fette dite sidewllF ve détil de ette zone ondulée se montre dns les pnneux EdX il y des miniEterrsses d9orienttion @HHHIA et des miniEfettesF ve grphène s9étend de mnière ontinue entre es deux régions mis l distne entre le grphène et le sustrt hngeF v distne entre le grphène et le sustrt dns les miniEterrsses est de PFQ ÅD e qui suggère un fort ouplge ve le sustrtF in revnheD l distne entre le grphène et le sustrt dns les miniE fettes est de RFH ÅD e qui résulte en un déouplge du grphène ii et devrit don être métlliqueF gependnt l normle de es régions vrie entre ∼ 12 • et 25 • D e qui orrespond ux normles ou l nde interdite est oservée pr eiF gomme es miniEruns ont une lrgeur de IEP nm permettnt d9ouvrir une nde interdite dns le grphène et qu9une nde interdite été oservée mlgré le déouplge du sustrtD nous onluons que l rison de l9ouverture de l nde interdite est le on(nement életronique dns es nnorunsF hes mesures d9iiv ve résolution tomique et de vF hngD wF uF frinkleyD qF finD F willerD nd FEgF ghingF hononE indued gps in grphene nd grphite oserved y ngleEresolved photoemissionF Physical Review LettersD IHSXIQTVHRD PHIHF IHH F viuD fF vF tksonD tF huD gFEF wioD gFErF ghungD FEtF rkD uF unD tF ooD nd FErF ieF vrge sle pttern grphene eletrode for high perforE mne in trnsprent orgni single rystl (eldEe'et trnsistorsF ACS NanoD RXQWPUD PHIHF IHI F yzhiiD wF yzhiiD eF touD nd F ytsujiF gurrentEvoltge hrteristis of grpheneEnnorion (eldEe'et trnsistorF AIP Journal of Applied PhysicsD IHQXHWRSIHD PHHVF IHP rF wohmdpour nd eF esgriF qrphene nnorion tunneling (eld e'et trnsistorsF Physica E: Low-dimensional systems and nanostructuresD RTXPUHD PHIPF IHQ tF ghenF Introduction to Scanning Tunneling MicroscopyF yxford niversity ressD IWWQF IHR wF hmidF he snning tunneling mirosopeF http://www.iap.tuwien.ac. at/www/surface/stm_gallery/stm_schematicF IHS shington niversityF nning tunneling mirosopyF https://depts. washington.edu/nanolab/NUE_UNIQUE/Lab_Units/5_Lab_Unit_STM.pdfF IHT hF fF illims nd gF fF grterF Transmission Electron Microscopy: A textbook for Materials ScienceF pringer ieneD PHHWF IHU F viD eF qloterD rF quD F goD F tinD nd gF golliexF ole of epitxil mirosE trutureD stress nd twin oundries in the metlEinsultor trnsition mehnism in yPGelPyQ heterostruturesF Acta MaterialiaD TIXTRRQD PHIQF IHV fF pultz nd tF wF roweF Transmission Electron Microscopy and Diractometry of MaterialsF pringerD PHHVF IHW teolF qlossry of iw termsF http://www.jeol.co.jp/en/words/emterms/ search_result.html?keyword=LAADF-STEMF IIH gF golliexF La microscopie électroniqueF ufD IWWVF III F hngF Photoemission Spectroscopy on High Temperature Superconductor: A study of Bi2Sr2CaCu2O8 by Laser-Based Angle-Resolved PhotoemissionF

	IQQ IQS IQU IQW
	et qui présentent une nde interditeD à use du on(nement életroniqueF W eF gstellnosEqomezD wF ojtszekD errmelD xF omrosD nd fFtF vn eesF IW F froneD yF rodD nd qFiF useriF iletroni struture nd stility of QH tF ngEghulF prition of grphene nnorion with eletron em lithogE RH vF psztóD qF horikD F vminD nd vF F firóF iloring the tomi struture RW gF oD vF tioD yF F zyevD FEgF ghenD tF pengD F hngD F fF gpzD tF wF SV vF gF gmposD F F wnfrintoD tF hF nhezEmgishiD tF uongD nd TV F uoyshiD uF uuskeD uF pukuiD nd F inokiF wG oservtion of VH hF F uosynkinD F vuD eF initskiiD qF erD F unD nd tF wF ourF righly iF rF gonrdF e wideEndgp metlEsemiondutorEmetel nnostruture mde WW F viuD
	eversile hydrogention nd ndgp opening of grphene nd grphite surfes semionduting grphene nnorionsF Nano LettersD TXPURVD PHHTF rphy using EISRIGwwe liftEo' proessF Transactions on Electrical and of grphene nnorions y snning tunnelling mirosope lithogrphyF Nature ourD eF ettlD nd F qF vouieF ptilly resolving edge sttes of hirl grphene F trilloErerreroF enisotropi ething nd nnorion formtion in singleElyer peulir eletroni sttes t grphite edgesF Physica E: Low-dimensional Systems ondutive grphene nnorions y londigutinl splitting of ron nnotues entirely from grpheneF Nature PhysicsD WXRWD PHIPF
	proed y snning tunneling spetrosopyF SmallD VXITHUD PHIPF PH FEF onD wFvF gohenD nd FqF vouieF inergy gps in grphene nnorionsF Electronic MaterialsD IIXIWH!IWQD PHIHF NanotechnologyD QXQWUD PHHVF nnorionsF Nature PhysicsD UXTITD PHIIF grpheneF Nano LettersD WXPTHHD PHHWF and NanostructuresD QRXTUVD PHHTF using potssium vporF ACS NanoD SXWTVD PHIIF WH wF prinkleD tF riksD eF ejedD eF leEsrhimiD F ve pèvreD pF fertrnD
	luls Einitio soutiennent ussi ette interpréttionF Conclusions ge trvil été dédié à l9étude de ndes interdites dns l struture életronique du grphène pr nnostruturtionF xous vons suivis deux pprohes X l9introdution d9un potentiel superpériodique sur le grphène pr des sustrts viinux de métux noles et le on(nement életronique dns des nnoruns sur des fettes rti(ielles du igF hns les sustrts viinuxD nous vons induit un potentiel périodique dns le grphène sur deux sustrts di'érentsD sur sr@QQPA et sur une surfe multiviinl de t@IIIAF eve une roissne de type gh nous vons produit du grphène ontinu sur l surfe nnostruturéeD e qui induit une modi(tion de l struture de ndes du grphène que nous vons oservé pr eiF v nde π du grphène présente plusieurs minigps ssoiés u potentiel périodique dû à l nnostruturtionF ges minigps peuvent être expliqués ve un hmiltonien de hirD e qui nous permis de déterminer l rrière de potentiel induite pr l superpériodiitéD qui dépend de l périodiitéD du type de ord de mrhe et du type de sustrtF hns les nnoruns de grphène sidewll nous vons rélisé l première étude de w ve résolution tomiqueF xous vons identi(é des orrugtions nnométriques IH F vuoD tF hngD F vimD hF viD F iongD F henD tF vinD nd F uF wodultE Physical Review LettersD WUXPITVHQD PHHTF QI wF F rnD fF yzylmzD F hngD nd F uimF inergy ndEgp engineering of RI F tF iD tF eF odríguezEwnzoD eF F fotelloEwéndezD F tF rongD iF eF thD SH eF xritD F pengD F rernndezD F eF tenseD wF fonnD rF ngD sF eF erzhE TW wF sjäsD wF irvstiD eF ppstuD F viljerothD tF vn der vitD sF wrtD nd eF rrjuF VI F hu nd tF wF ourF qrphene nnorion thin (lms using lyerEyElyer rF inkeyD wF gF glrkD F oukissinD hF wrtinottiD tF rssD nd iF rF gonrdF SW vF giD F uD vF ngD F qoD pF hingD uF pF uellyD fF sF kosonD nd F wF Bibliography I tFErF ongD fFEF uD nd wFEpF vinF trin e'et on the eletroni properties of single lyer nd ilyer grpheneF The Journal of Physical Chemistry CD IITXVPUID PHIPF P F ereirD eF gstro xetoD nd xF eresF e tightEinding pproh to unixil strin in grpheneF Physical Review BD VHXHRSRHID PHHWF Q xF vevyD F eF furkeD uF vF wekerD wF nlsiguiD eF ettlD pF quineD eF rF gF ing the eletroni strutures of grphene y ontrollle hydrogentionF Applied Physics LettersD WUXPQQIIID PHIHF II eF vF ilísD F F xirD F wF qF wohiuddinD F F worozovD F flkeD wF F rlsllD eF gF perrriD hF F foukhvlovD wF sF utsnelsonD eF uF qeimD nd uF F xovoselovF gontrol of grphene9s properties y reversile hydrogentionX ividene for grpheneF ScienceD QPQXTIHD PHHWF IP uF xkdD wF pujitD qF hresselhusD nd wF F hresselhusF idge stte in grphene rionsX xnometer size e'et nd edge shpe dependeneF Physical Review BD SRXID IWWTF PI vF ngD gFErF rkD FEF onD wF gohenD nd F vouieF usiprtile energies nd nd gps in grphene nnorionsF Physical Review LettersD WWXIVTVHID PHHUF PP vF isniD tF ghnD fF wontnriD nd xF rrrisonF iletroni struture nd mgneti properties of grphiti rionsF Physical Review BD USXHTRRIVD PHHUF PQ yFF zyevF imergene of mgnetism in grphene mterils nd nnostruturesF Reports on Progress in PhysicsD UQXHSTSHID PHIHF PR uF kyshi nd wF igrist F kneF erfetly onduting hnnel nd uniE grphene nnorionsF Physical Review LettersD WVXPHTVHSD PHHUF QP FEhF ghenD FEfF viuD FEF tingD FEF nD pF ingD F ngD F ghenD nd tFEqF inF he seletive trnsfer of ptterned grpheneF Scientic ReportsD QXQPITD PHIQF QQ tF eF qrdener nd tF eF qolovhenkoF seEssisted eletron em lithogrphy of grpheneF NanotechnologyD PQXIVSQHPD PHIPF QR F ng nd rF hiF ithing nd nrrowing of grphene from the edgesF Nature ChemistryD PXTTID PHIHF F F rkD tFEgF ghrlierD wF hrndi¢D nd eF F gF tohnsonF gorrelting tomi struture nd trnsport in suspended grphene nnorionsF Nano Let-tersD IRXRPQVD PHIRF itskiyD gF gsirghiD wF yn rnsenD eF rF F uohD qF pytsD yF svsenkoD fF viD uF F wliD F flndinD F wheshD F he peyterD nd uF wüllenF yntheE sis of struturl wellEde(ned nd liquidEphseEproessle grphene nnorionsF Nature ChemistryD TXIPTD PHIQF iletroni sttes in (nite grphene nnorionsX i'et of hrging nd defetsF ssemlyF Nano LettersD IHXRQSTD PHIHF wultilyer epitxil grphene grown on the ig@HHHEIA surfeY struture nd ejynF gontrolled nnoutting of grpheneF Nano ResearchD IXIITD PHHVF Physical Review BD VVXHUSRPWD PHIQF eletroni propertiesF Journal of Physics D: Applied PhysicsD RQXQURHHTD PHIHF VP F F viD wF F ghenD wF einertD nd vF viF hiret experimentl determinE TH F F httD hF F trhnD F wF uhmisD nd eF F gF tohnsonF grystlloE UH F viuD eF horinskyD nd fF kosonF qrphene edge from rmhir to zigzgX tion of onset of eletronEeletron intertions in gp opening of zigzg grphene WI tF fringhusD eF törD F portiD F eF ursnikovD eF eF khrovD F trkeD grphi ething of fewElyer grpheneF Nano LettersD VXIWIPD PHHVF he origins of nnotue hirlityc Physical Review LettersD IHSXPQSSHPD PHIHF nnorionsF Nature CommunicationsD SXRQIID PHIRF nd gF egenkmpF fipolr gting of epitxil grphene y interltion of qeF RP qF F wgdD F tinD sF rgymásiD F nsóD F ysváthD F xemesEsnzeD gF rwngD vF F firóD nd vF psztóF oomEtemperture mgneti order on zigzg edges of nrrow grphene nnorionsF NatureD SIRXTHVD PHISF SI tF tioD F ngD qF hinkovD rF ngD nd rF hiF pile synthesis of highE qulity grphene nnorionsF Nature NanotechnologyD SXQPID PHIHF SP hF F uosynkinD eF vF rigginothmD eF initskiiD tF F vomedD eF himievD TI tF giD F u0euxD F tfrD wF fieriD F frunD F flnkenurgD wF wuothD eF F eitsonenD w FlehD F pengD uF wüllenD nd F pselF etomilly preise UI F qllgherD uF oddD nd hF qoldherEqordonF hisorderEindued gp ehvior Applied Physics LettersD IHRXPTITHPD PHIRF VQ F flkenurgD tF giD F u0euxD F tfrD hF sseroneD F pengD uF wüllenD in grphene nnorionsF Physical Review BD VIXIISRHWD PHIHF F pselD nd gF eF ignedoliF sntrrion heterojuntion formtion of ultrnrE WP F rertelD hF ldmnnD tF tostD eF elertD wF elrehtD F eshnovD ottomEup frition of grphene nnorionsF NatureD RTTXRUHD PHIHF UP wF F rnD tF gF frntD nd F uimF iletron trnsport in disordered grphene row grphene nnorionsF ACS NanoD TXPHPHD PHIPF eF honerD wF uriegerD nd rFfF eerF iloring the grpheneGsilion rE RQ F F eiD hF fF ngD F uimD F F uimD F uF ruD wF uF kesD eF F vruenteD F F hiD F F wrderD gF fergerD F F uingD F eF de reerD F iF heehnD nd iF iedoF xnosle tunle redution of grphene oxide for fF uF rieD nd tF wF ourF vongitudinl unzipping of ron nnotues to form grphene nnorionsF NatureD RSVXVUPD PHHWF TP F vindenD hF hongD eF immerD xF eghdssiD tF rF prnkeD rF hngD F pengD uF wüllenD rF puhsD vF ghiD nd rF hrisF iletroni struture of sptilly nnorionsF Physical Review LettersD IHRXHSTVHID PHIHF UQ pF olsD pF quineD nd eF rF gstro xetoF goulom lokde in grphene ide interfe for monolithi wferEsle eletronisF Nature CommunicationsD VR tF giD gF eF ignedoliD vF lirzD F u0euxD rF ödeD vF vingD F weunierD QXWSUD PHIPF F fergerD F viD nd F pengF qrphene nnorion heterojuntionsF Nature xetoD nd wF pF grommieF trinEindued pseudoEmgneti (elds greter thn QHH esl in grphene nnoulesF ScienceD QPWXSRRD PHIHF R F flogD fF torgensenD vF xilssonD wF endersenD iF ienksD wF finhiD wF pnettiD F vegsgrdD eF frldiD F vizzitD F ljivnninD pF fesenherD fF rmmerD FqF edersenD F rofmnnD nd vF rornekerF fndgp opening in grphene indued y ptterned hydrogen dsorptionF Nature MaterialsD WXQISD PHIHF S fF F wtisD tF F furgessD pF eF fultD eF vF priedmnD fF rF roustonD nd tF F fldwinF urfe doping nd nd gp tunility in hydrogented grpheneF ACS NanoD TXIUD PHIPF T F eF henisF fnd gp opening of monolyer nd ilyer grphene doped with luminiumD silionD phosphorusD nd sulfurF Chemical Physics LettersD RWPXPSID PHIHF U F eF henisF ghemil retivity of ndEgp opening of grphene doped with glliumD germniumD rseniD nd selenium tomsF ChemPhysChemD ISXQWWRD PHIRF IQ uF kyshiD wF pujitD rF ejikiD nd wF igritF iletroni nd mgneti properties of nnogrphite rionsF Physical Review BD SWXVPUID IWWWF IR eF rF gstro xetoD xF wF F eresD uF F xovoselovD nd eF uF qeimF he eletroni properties of grpheneF Reviews of Modern PhysicsD VIXIHWD PHHWF IS F gnerD gF F iwelsD tFEtF edjizin ndvF wgudD F ohetD F oheD eF vopezEfeznillD F F svnovskyD eF yD wF ysonD F friddonD nd fF rumertF fnd gp engineering vi edgeEfuntionliztion of grphene nnorionsF The Journal of Physucal Chemistry CD IIUXPTUWHD PHIQF IT F F onD wF vF gohenD nd F qF vouieF rlfEmetlli grphene nnorionsF NatureD RRRXQRUD PHHTF IU pF wD F quoD uF uD nd F uF ghuF pirstEpriniple study of energy nd struE ture of rmhir grphene nnorionsF Solid State CommunicationsD ISPXIHVWD PHIPF IV pF tF wrtínEwrtínezD F pisD qF n vierD pF he roftD nd F qeerlingsF verslity rossover in disordered grphene nnorionsF Physical Review LettersD WWXHQTTHID PHHUF PS gF fergerD F ongD F viD F viD eF F ygzghiD F pengD F hiD F qrenetD QS eF initskii nd tF wF ourF tterning grphene nnorions using opper oxide nnowiresF Applied Physics LettersD IHHXIHQIHTD PHIPF grphene eletronisF ScienceD QPVXIQUQD PHIHF RR F rF oD wF hekhirevD hF eF uunkelD wF hF wortonD iF ferglundD uF uongD F wF ligned grphene nnorions on eu@UVVAF Physical Review LettersD IHVXPITVHID nnorionsF Physical Review LettersD WWXITTVHQD PHHUF NanotechnologyD WXVWTD PHIRF WQ tF tohnsonD eF fehnmD F ertonD nd eF rlF rydrogen sensing using dE SQ hF fF hindeD wF wjumderD nd F uF illiF gounterEion dependentD longiE tudinl unzipping of multiEwlled ron nnotues to highly ondutive nd trnsprent grphene nnorionsF Scientic ReportsD RXRQTQD PHIRF PHIPF TQ FEgF ghenD hF qF de yteyzD F edrmrziD gF ghenD pF F pisherD nd wF pF UR gF tmpfefD tF qüttingerD F rellmüllerD pF wolitorD uF insslinD nd F shnF inE ergy gps in ethed grphene nnorionsF Physical Review LettersD IHPXHSTRHQD funtionlized multiElyer grphene nnorion networksF Advances MaterialsD VS tF uunD F ruD tF lmerD F quoD tF rnkinsonD F rG qmlD gF fergerD nd PPXRVUUD PHIHF F eF de reerF lnr edge hottky rrierEtunneling trnsistors using epitxil ilsonD F eF howenD eF indersD nd eF initskiiF vrgeEsle solution synthesis eF xF wrhenkovD iFrF gonrdD FxF pirstD nd F eF de reerF ltrthin epitxil grphiteX Ph eletron gs properties nd route towrds grpheneE sed nnoeletronisF The Journal of Physical Chemistry BD IHVXIWWIPD PHHRF PT tF fiD F hunD nd F rungF tionl frition of grphene nnorions using nnowire eth mskF Nano LettersD WXPHVQD PHHWF PU qF viuD F uD FEwF vinD hF fF prmerD tF eF yttD tF fruleyD eF qrillD F evourisD hF fei'erD eF eF flndinD nd gF himitrkopoulosF ipitxil grphene nnoriE on rry frition using fgEssisted nnolithogrphyF ACS NanoD TXTUVTD PHIPF PV F eF de reerD gF fergerD F uD F xF pirstD iF rF gonrdD F viD F viD wF prinkleD tF rssD wF vF dowskiD wF otemskiD nd qF wrtinezF ipitxil grpheneF Solid State CommunicationsD IRQXWPD PHHUF QT qF uD tF fiD gF wF orresD iF fF ongD tF ngD F houD F hunD F hngD of nrrow grphene nnorionsF Nature CommunicationsD SXQIVWD PHIRF grommieF uning the nd gp of grphene nnorions synthesized from moleE PHHWF grpheneGig juntionsF Nano LettersD IRXSIUHD PHIRF WR pF rversiD gF illonD F wF fenmeurD uF viuD F uhlyovD wF osunD hF ursE SR vF tioD vF hngD F ngD qF hinkovD nd rF hiF xrrow grphene nnoriE nd uF vF ngF vowEnoise sumiron hnnel grphene nnorionsF Applied Physics LettersD WUXHUQIHUD PHIHF QU F iF fryn nd F wurli F ngF gondutne of epitxil grphene nnoriE onsX sn)uene of size e'ets nd sustrte morphologyF The Journal of Physical Chemistry CD IISXIHPQHD PHIIF QV F F rwngD F hoD uF hyD vF yF xykitiD F hF heelerD F vF wyersE rdD gF F iddy trFD hF uF qskillD tF eF oinsonD F renshD rF @qreA ingD eF eughD nd hF tenF qrphene nnorion (eldEe'et trnsistors RS F tiD wF rofmnnD F weunierD fF qF umpterD tF gmposEhelgdoD tF wF omoErerrerD rF onD F F rsiehD eF einD tF uongD wF erronesD nd wF F hresselhusF gontrolled formtion of shrp zigzg nd rmhir edges in grphiti nnorionsF ScienceD QPQXIUHID PHHWF RT F viD F ngD vF hngD F veeD nd rF hiF ghemilly derivedD ultrsmooth grphene nnorion semiondutorsF ScienceD QIWXIPPWD PHHVF RU gF llésD gF hrummondD rF douiD gF eF purtdoD wF reD yF oueuD vF yrE ons from ron nnotuesF NatureD RSVXVUUD PHHWF SS eF vF ilísD eF F fotelloEwéndezD hF wenesesEodríguezD F tehová qonzálezD hF mírezEqonzálezD vF giD iF wuñozEndovlD F wF ejynD rF erronesD nd ulr preursorsF ACS NanoD UXTIPQD PHIQF US tF fF yostingD fF épéD wF pF griunD nd eF pF worpurgoF wgnetotrnsport through grphene nnorionsF Physical Review BD VIXIWQRHVD PHIHF nozhonD eF uisD nd eF denoviF heteting the trnslotion of hxe through VT tF fringhusD wF unD pF idlerD eF ejedD wF iotD eF leEsrhimiD eFF nnopore using grphene nnorionsF Nature NanotechnologyD VXWQWD PHIQF viD F tingD iFrF gonrdD gF fergerD gF egenkmpD nd FeF de reerF ixE TR F uto nd F rtkeymF iteEnd lignmentEontrolled growth of grpheneE nnorions from nikel nnorsF Nature NanotechnologyD UXTSID PHIPF eptionl llisti trnsport in epitxil grphene nnorionsF NatureD SHTXQWRD WS wF preitgD F vowD F huD rF nD pF iD nd F evourisF hotourrent UT hF qunlyke nd gF F hiteF ling of the loliztion length in rmhirEedge grphene nnorionsF Physical Review BD VIXHUSRQRD PHIHF PHIRF in grphene hrnessed y tunle intrinsi plsmonsF Nature CommunicationsD wF erronesF vongitudinl utting of pure nd doped ron nnotues to form grphiti nnorions using metl lusters s nnoslpelsF Nano LettersD IHXQTTD PHIHF ST hF eiD vF ieD uF uF veeD F ruD F nD F ghenD rF owD uF ghenD F viuD nd eF F F eeF gontrollle unzipping for intrmoleulr juntions of grpE TS eF xF okolovD pF vF pD xF viuD uF uimD uF giD yF fF tohnsonD rF ngD UU gF fergerD F ongD F viD F uD xF frownD gF xudD hF wyouD F viD tF rssD RXIWSID PHIQF VU tF fringhusD pF idlerD nd gF egenkmpF idgeEsttes in grphene nnoriE wF osguerithinD eF vF uohD tF ghenD tF rkD nd F foF hiret growth of eF xF wrhenkovD iF rF gonrdD nd F xF pirstF iletroni on(nement nd onsX e omined spetrosopy nd trnsport studyF Journal of Physics: Con-WT FEpF hiD F uD hF gF lphD nd F vF wiuenF lsmon resonne in individul ligned grphiti nnorionsfrom hxe templte y hemil vpour deposiE oherene in ptterned epitxil grpheneF ScienceD QIPXIIWID PHHTF densed MatterD PSXQWPHHID PHIQF nnogp eletrodes studied using grphene nnoonstritions s photodetetorsF tionF Nature CommunicationsD RXPRHPD PHIQF NanolettersD IIXIVIRD PHIIF VV sF lioD eF gelisD wF xF xirD eF qloterD eF oelliD wF iotD hF wlterreD UV qF uD gF wF orresD tF fiD tF ngD nd F uF vinewidth roughness in nnowireE on wferEsle epitxil grphene on ig sustrtesF APL MaterialsD QXHIIIHID PHISF QW F ieiroD tFEwF oumirolD eF grestiD F iso0erD wF qoirnD tFEwF frotoD tolniD wF wonthiouxD nd eF éniudF olutions of negtively hrged grphene sheets nd rionsF Journal of the American Chemical SocietyD IQHXISVHPD PHHVF RV F F uD F eD vF qoD fF viuD tF hoD nd rF wF ghengF i0ient synthesis of hene nnorions nd singleEwlled ron nnotuesF Nature CommunicationsD RXIQURD PHIQF SU F qongD wF vongD qF viuD F qoD gF huD F eiD F qengD wF unD gF ngD TT sF wrtinEpernndezD hF ngD nd F hngF hiret growth of grphene nnoriE wF F xeviusD F eF de reerD gF fergerD iF rF gonrdD eF leEsrhimiD nd WU F yzhiiD wF yzhiiD wF F hurD F witinD eF touD nd F ytsujiF esonnt mskEsed grphene nnorionsF Applied Physics LettersD WVXPRQIIVD PHIIF ons for lrgeEsle devie fritionF Nano LettersD IPXTIUSD PHIPF TU hF ngD rF inD F ngD hF ieD FEvF enD nd F hngF lle nd diret eF ejedF etomi struture of epitxil grphene sidewll nnorionsX plt plsmoni terhertz detetion in grphene splitEgte (eldEe'et trnsistors with UW tF gmposEhelgdoD tF wF omoErerrerD F tiD hF eF gullenD rF wurmtsuD F eF uimD F ryshiD F enD hF tF mithD F ykunoD F yhD rF unohD grpheneD minirionsD nd the on(nement gpF NanolettersD ISXIVPD PHISF lterl pEn juntionsF Journal of Physics D: Applied PhysicsD RWXQISIHQD PHIPF
	que nous vons retrouvés ussi dns les études pr iwF ges orrugtions tomiques V F vv nd wF erronesF owrds new grphene mterilsX hoped grphene sheets iletroni struture nd romtiity of grphene nnorionsF Chemistry -A PW F ghenD FEwF vinD wF tF ooksD nd F evourisF qrphene nnoErion eleE F oheD nd fF quetF nveiling the mgneti struture of grphene nnoriE grphene nnorions sonohemilly ut from grphene sheetsF Nano ResearchD vF vuD nd vF viuF iletroni trnsport properties of grphene nnorion rrys growth of grphene miro rions on dieletri sustrtesF Scientic ReportsD wF F hresselhusD nd wF erronesF fulk prodution of new form of sp 2 VW tF riksD eF ejedD eF leEsrhimiD wF F xeviusD pF ngD uF hepperdD WV pF hwierzF qrphene trnsistorsX ttusD prospetsD nd prolemsF Proceedings
	sont à l9origine de runs de grphène d9une tille nnométrique déouplés du sustrt nd nnorionsF Materials LettersD UVXPHWD PHIPF European JournalD IVXTIVQD PHIPF tronisF Physica E: Low-dimensional Systems and NanostructuresD RHXPPVD PHHUF onsF Physical Review LettersD IHUXHVTTHID PHIIF QXITD PHIHF frited y unzipping ligned nnotuesF Physical Review BD VUXITSRHRD PHIQF QXIQRVD PHIQF ronX grystlline grphene nnorionsF Nano LettersD VXPUUQD PHHVF tF lmerD pF fertrnD F ve pèvreD tF uunD F eF de reerD gF fergerD nd of the IEEED IHIXISTUD PHIQF
	IPW

Acknowledgments

Appendix A

Supplementary material

A.1 Temperature programmed growth on Gr/Ir(332) Keywords : grpheneD nnostrutureD nd gpD wD eiD iw Abstract : he mjor hllenge for grpheneEsed eletroni pplitions is the sene of the ndEgp neessry to swith etween on nd o' logi sttesF qrphene nnorions provide route to open ndEgpD though it is hllenging to produe tomilly preise nnorion widths nd wellEordered edgesF e prtiulrly elegnt method to open ndEgp is y eletroni on(nementD whih n in priniple e tuned y djusting the nnorion widthF his thesis is dedited to understnding the wys of opening ndEgps y nnostruturtionF e hve used two pprohesX the introdution of superperiodi potentil in grphene on viinl nole metl sustrtes nd the eletroni on(nement in rti(illy ptterned nnorions on igF uperperiodi potentils on grphene hve een introdued y two nnostrutured sustrtesD sr@QQPA nd multiviinl urved t@IIIA sustrteF he growth of grphene modi(es the originl steps of the pristine sustrtes nd trnsforms them into n rry of @IIIA terres nd step unhing resD s oserved y wF his nnostruturtion of the underlying sustrte indues the superperiodi potentil on grphene tht opens miniEgps on the π nd s oserved y ei nd onsistent with the struturl periodiity oserved in w nd viihF he miniEgps re stisftorily explined y hirEhmiltonin modelD tht llows to retrieve the potentil strength t the juntions etween the @IIIA terres nd the step unhingF he potentil strength depends on the sustrteD the surfe periodiity nd the type of stepEedge @e or f typeAF he surfe potentil hs lso een modi(ed y interlting gu on sr@QQPAD tht remins preferentilly on the step unhing resD produing there nEdoped rionsD while the nonEinterlted res remin pEdopedD giving rise to n rry of nE nd pE doped nnorions on single ontinuous lyerF sn the seond pproh to ontrol the gpD we hve studied the gp opening y eletroni onE (nement in grphene nnorions grown on igF hese rions re grown on n rry of stilized sidewlls on igF es ndEgp opening with unler tomi origin hd een oserved y eiD we rriedEout orrelted study of the tomi nd eletroni struture to identify the nd gp originF e performed the (rst tomilly resolved study y wD demonstrting the smoothness nd hirlity of the edgesD (nding the preise lotion of the metlli grphene nnorion on the sidewlls nd identifying n unexpeted miniEfeting on the sustrteF o understnd the oupling of grphene to the sustrteD we performed rossEsetionl study y iwGiivD omplementry of our ei nd wG studiesF e oserve tht the @1107A ig sidewll fet is suEfeted oth t its top nd ottom edgesF he sufetting onsists of series of @HHHIA miniterres nd @1105A minifetsF qrphene is ontinuous on the whole sufetting regionD ut it is oupled to the sustrte on top of the @HHHIA miniterresD rendering it there semiondutingF yn the ontrryD grphene is deoupled on top of the @1105A minifets ut exhiits ndgpD oserved y iiv nd omptile with ei oservtionsF uh ndgp is originted y eletroni on(nement in the I E P nm width grphene nnorions tht re formed over the @1105A minifetsF Université Paris-Saclay Espace Technologique / Immeuble Discovery