DejectandD炉 ∫̀io77For7JmVols./60-16](1998)pp_57164㊨J998SciLecPubZicaLions,SwiIzer/077d

PhaseDefectsonSi(100)Surface,StudiedbyScannlngTunne=ngMicroscopy

H.Shigekawa,K.Miyake.M.lshida,S.OzawaandK.Hata

lnstituteofMaterialsScience,CenterforTsukubaAdvancedResearchATliance(TARA).UniversrtyofTsukuba,Tsukuba305,Japan

CREST,JapanScienceandTechnologyCorporation(JST)

Keywords:Phasons.phasetransition.surfacedefects,lsingmodel.dimerinteraction

Abstract:DynamicsofanewmovabletypePphasedefect,thatis,phasonsformedonSi(1(刀)dimer

rows,andrelatedstructuralchilngeSWereStudiedfromroomtemperatureto6Konanatomicscale,in

relationtotheinteractJOnbetweenSi(100)surfacediners.At～200K,dinernip-flopmotionbegan

tofreezefromthedefectsondinerrows,andtheantiferomagneticcorrelationappearedalongdjmer

rowsfirsLWithfurtherdecl'eaSeintemperature,C(4x2)Structurebegantocoverthesurface･While

typePdefectsnligratedonthesurface,thec(4x2)arTangementperSistedasthetemperaturedecreased

to30K･TheobservedchangewasconsistentwiththeordeトdlSOrderphasetransitionwhichhasbeen

observedontheSi(100)surface･At6K,incontrast,themigratlOnOfthephasonsresultedinanapparent

phasetransitionbetweenc(4x2)andp(2x2)amngementS,Whichindicatesthattheinteractionbetween

dimerTOWSissignificantlyweilkeratthistemperature,andsuggestssomecharacteristlCChangebetween

ト 30Kand6K.Long,angeinteractionwasfoundtoplayanimportant,oleonSi(100)surface.

Withtheprogressofthenanoscalescienceandtechnology,atomicdefectsinmaterlalsurfaces/

Interfacesbegintoplayanincl▲eaSinglyimportantrole,andthereforeitisnecessarytocharacterizethe

structureofthedefectsatanatomicscale･FortheSi(100)surface,itisweLlestablishedthatpairsof

top-layeratomsformdimeJ.ゝ･AsIdentifiedbyHamersetal･,therearethreetypicaltypesofdefects-

typeAcorrespondingtoasing一edimervacancy;typeBtoadoubledimervacancy;andtypeCtotwo

half-dimersresultingfromtwoadjacentSivacanciesalongthe<110>directionll〕.Recently,anew

type ofmovabledefectknownastypepdefect,wasfoundtoexistontheSi(loo)surface,andthe

dynamicsOfthephasedefectthephason,wasdirectlyobservedbyscanningtunneLingmicroscopy

(STM)at80Kand6K[2-5],ThetypePdefecthasastructuresimilartothetypeCdefectwhichacts

toinduceaphaseshift:atypePdefectconsistsoftwoadjacentdimerswhicharebuckledwiththe

sameorientation･However,incontrasttothetype Cdefect,type Pdefectcanmlgratealongdiner

rowsduetodin ernip-mopmotionatthephaseboundaries.Inthispaper,therecentSTMstudieson

thesedefectswillbesummarized,andthecharacteristicsofthetypePdefect.inrelationoftheinteraction

betweenSi(100)surfacedjnlerSWilldiscussed.

FordefectsoftypesAandB,structuralmodelswhichhaverebondedconfigurationsinthe

secondlayerwereproposedoriginallyl6]･TheelectronicstructureofthetypeAdefectandthecross

sectionofthetypeBdefectdeterminedbySTM atroomtemperaturewereconsideredtoprovidethe

58 SurfaceDWus10nandSurfaceStructure

evidencefortheapplicabilJt7e."ftherebondedmodell7,8]･However,recently,theeffectsofthese

defectsonthebucklingofadjacentdinerswerestudiedbySTM at80K,whichraisedquestions

relatedtothestructuresofthesedefectsl9].FromtheSTMobservationsofSi(loo)surfacesatroom

temperature,typeAandtypeBdefectsdidnotcausedetectablestaticbuck]ingora叫acentdimers･At

80K,ouトof-phasebucklingofadjacentdimerswasobservedinthecaseofthedoublevacancydefect

(typeB)･However,thesinglevacancydefect(typeA)wasfoundtobefurthersubdividedintothree

types,Al,A2,andA3:AIsuppressesbucklingofadjacentdinersevenatlowtemperatures,A2

inducesin-phasebuckling,andA3inducesout-of-phasebuckling･lfthesethreeeffectsaredueto

differencesinthestructuresofthetypeAdefects,theremustbethreedifferentinternals(rtlCtureSfor

thetypeAdefect･Detailswerestudiedbyobservlngthebias-dependentSTMImages,andtypeAand

typeBdefectswerefoundtohaveacharacteristicrelationshipbetweenthelrelectronicstructuresand

theireffectsonbucklingofadjacentdlmerSinducedat80K.Therelationshipbetweenthephaseof

dinerbucklingandtheeleclronicstructureofthedefectcou一dbecomprehensivelyexplainedinterms

ofthedinerstructureofthedefectl10].

RegardingthetypeCdefect,sincefromtheresultsofthespectroscoplCStudyonlythisdefect

showedastrongmetalliccharacteritisconslderedtoformasurfacestatewhichcausesFermilevel

pinningl11･AstructuralmodelwithdimerfomlationinthesecondlayerwasproposedbyUdaetaL

l11】,Sincethecalculatedelectronicstructureofthetype Cdefectwasingoodagreementwiththe

STMresults,thestructureofthetype Cdefectwasconsideredtohavebeencompletelydetermined･

However,recently,Semiconductivepropertywasobservedtobeinducedat80K〔12]･Inaddition,

slngletype CdefectwasfoundtoInducealongrangeinteractiononthesurface;whenthetypeC

defectwasremovedbytheatomicmanlPUlationtechnique,thestmctureofthelargeareasurrounding

thedefectwasobservedtobestronglyaffected[13].Theseresultsarerelatedtothefactthattype C

defectinducesaphaseshlfLandstrongInteractionbetweenthetypeCdefectandthesurrounding

buckJeddinerswasobserveddirectlyl13].

Fromtheexperimentalresultsdescribedabove,defectsoftypesA,BandCmustplayamuch

moreimportantroleinthemnOSCaletechnologythanexpected.Therefore,moredetailedanalysisis

requiredtoclarifytheircharacterlStlCS.Inanycase,itisclearthatphaseshiftinducedinthebuckled

dinerarrangementbythedefectsisquiteimportantonthesurface･Ontheotherhand,asdescribed

above,typePdefectisamovablephasedefect,andmigrationofthedefectsisstronglyrelatedtothe

characteristicsoftheSi(100)surfacestructure.However,littleisknownaboutthetypePdefect.h

thispaper,wepresen(OurrecentresultsontheSTM observationofthedynamicsoftheSi(100)

surfacecausedbythetype Pdefectfromroomtemperatureto6K,byfocusLngOntheinteraction

betweendinersonthesurface.

As iswellknown,thedetailsofthedimerarrangementhavebeencontroversialduringthelast

twodecades･Namely,dimer.<giveriselo(hesymmetric(2xl)structure;however,the(2xl)phaseis

nottheSi(100)groundstate,anddlfferentreconskuctionswithinsimilardinerstructureswereproposed

l14]･Anenergeticallyfavoredalternationofdimerbucklingalongthedinerrowsleads【othec(4x2)

reconstruction,inwhichaltema【lngbucklingaELglesarealsopresentbetweentwoneighboringdiners

DefectandDI'uusionForum Vo/S.160-161 59

belonglngtOdifferentrowsAnotherpossible

phaseisthep(2x2)phase,inwhichthebuckling

angleisthesamebetweenlWOneighboring

dinersbelonglngtOdifferentrows.Figurel

showsaschematicof(a)symmetric2xl,(b)

C(4x2),(C)p(2x2),and(d)coexistingc(4x2)and

p(2x2)strt)cturesw∫thasingletypePdefect･

Here,onlytheupperSlatomsOfthebuckJed

dinersareillustratedusingcircles･Lines

betweenthecirclesaredrawninordertocompare

thephaseshift.InFig.I,theantiferomagnetic

arrangementsofthebuckleddimers,whichforms

azigzagStnlCturealongthedlmerrows,Shows

theout-of-phase(Fig11(b))andln-Phase(Fig･

1(C))re一ationshipsbetweendimeHowsfor

c(4x2)andp(2x2)StfuClureS.reSpeCtively-

Whatmakestheill-gumentmore

complicatedisthatthedifferencebetweenthe

(a)く=∋く≡)

冒く∋(=)∈∋く∋

(C)

′…

ヽ

主

犯川騨

馴

mn

,DOO○○①①00

◎◎⑳⑬⑳e@◎

Fig.ISchematicof(a)symmetric2xJ,(b)C(4x2),

(C)p(2x2),and(d)coexTStingc(4x2)aTldp(2x2)

S帆CtureSWithasLngletypePdefecL

energiesofthep(2x2)andc(4x2)reconstructionsobtainedbytheoreticalcalculaLionsisonlyonthe

orderofImeVperdlmerH4].FromLEEDmeasurements,areversiblephasetransitionoccursbetween

theorderedc(4x2)anddisorderedphasesat-2CM)K【15]andthemoststablephasewasconcludedlo

bec(4x2)･Basedtotherecentlow-temperatureSTM studiesaL- 100Konthesurface,thec(4x2)

structurewasalsoconf)rmedtobethemoststablearrangementofthebuckleddinersl16-18].These

resultswerethoughttohavel̀eSu】tedthecontroversy,however,morerecently,l九ep(2x2)Structure

wasfoundtoreemergeatalowertemperatureof-6K,andfluctuationsbetweenthec(4x2)and

p(2x2)structureswasdlreCl】yobservedbySTM [2].

Theobservedphenomenonat-6Kisunderstoodtobecausedbythedynamicsofthemovab一e

phasedefectsformedonthedinerrows,thatis,type Pdefects･SincetypePdefectscauseaphase

shift,whenatype-Pdefectchangesitsposition,apparentphasetransitionbetweenthec(4x2)and

p(2x2)structuresoccurs(Fig･1(d)).Existenceofasimilardefectwasconfirmedevenatroom

temperature,andthestabilityofthec(4x2)structureandtheoriglnOfthesymmetricdinerswere

comprehensivelyexplainedbythedynamicsofthephasedefectl5]･Ontheotherhand,typePdefects

tendtoformpairsat80KsoilStOreducetheareaofthep(2x2)arrangementl31,whichdiffersfromthe

characteristicpropertyofthetypePdefectat6K;ぬosemovemoreindependentlyofeachotherat6K

l2]･Therefore.inordertounderstandtheobservedchangeontheSi(leo)surface;(1)>150K:disorder

(C(4x2)+p(2x2))→ (b)～ 150K:C(4x2)- (C)～ 6K:C(4x2)+p(2x2).itisnecessarytostudythe

temperature-dependenceofthesurfacedynamicsinmoredetail.

Experimentswereperrormeduslngalow-temperatureSTM,whichallowsobservationwith

atomicresolutionat-6Klnultrahighvacuum(5xlOl9pa).Aphosphorus-doped(0.010cm)Si(100)

SurfaceDiffusionandSurfaceStructure

samplesurfacewasheatedupt0-1200℃ afterprebakingforoneday,andcooledveryslowlyto

reducethedensityofthesurfacedefects･Basepressurewas～110xl0-8pa,andpressureduringtheheat

treatmentwaskeptbelow-5xl0-8pa.

Figure2showsSTMimagestakenat(a)roomtemperature,(b)-200K,(C)～80K,(d)30K,

and(e)～6K･AsisshowninFig･2(a),dinersappearsymmetricatroomtemperatureasiswell

knownJtiswidelyacceptedthatdinersarebuckledevenatroomtemperature,andswitchbackand

forthbetweenthetwopossibleorientationsinatimemuchshorterthanthelimescaleoftheSTM

measurement,whichresultsintheobservedsymm etricconfigurationintheSTMimagesIHowever,

whenthedinersnip-nopwlthoutcorrelation,thef一ip-mopmotionimplleSaCOmpletelydisordered

surface･Ontheotherhand,whenthephasedefectsmigraterapidlycomparedtothetimescaleofSTM

measurement,symmetricdimerscanbefb-edwithoutcompletelydestroylngthe2xanticorrelation

arrangement,whichagreeswellwiththefactthattheelectronicstructureobtainedbyphotoemission

spectroscopyatroomtempemtureisconsistentwiththetheoreticalresultcalculatedundertheassumpt10n

oforderedasymmetrlCdlmerSl19]Consideringtheseresults,thesymmetricdinerslntheSi(100)

SurfaceareconsideredtobecausedbythecharacteristicpropertiesofthetypePphasedefectofthe

dimerrowsl5】.Somedimersneardefectsa一ebuckled,whichisunderstoodtobecausedbytheeffect

ofthedefects;bucklingphaseisfixedbythedefects.

At､200K,asshowninFig.2(b),buckleddlmerSfrozennearthedefectsarelongercompared

tothosefrozenatroomtemperature.Evenat～200K,buckleddimersal.eJocaJizednearthedefects

onthedinerrows.TnFig.2(b),symmetricdinerregionsarecausedbythemlgratlOnOrthetype P

defectsasdescribedabove.Fromtheresultsat200Kanda【roomtemperature,interactionbetween

dimersisconcludedtobestrongeralongthedinerrowscomparedtothatbetweendユmerrowsatthis

temperaturerange･

Fig.2STMImagesOrS】()00)川rfacetakenal(a)rooTTltemperature,(b)200K,(C)80K,(d)30Kand(e)6K

DefectandDjffus/'onForumVo/S.160-161 61

AccordingtothepreviousSTM measurementat144K〔16】,anorderedc(4x2)structurewas

observedtocoverthesurface･【nthiscase,sym etricdinerdoma山swereobservedononesideofthe

typeCdefects･SinceatypeCdefectproducesaphaseshift,andintroducesaLnantiphasedomainon

oneofitssides,theobservedresultindicatesthatadomainwiththecompletep(2x2)aLTTangementWith

thetwoadjacentdinerrowsisveryunstableat144KJntheSTMimageobtainedat120K,thep(2x2)

arrangementwasobservedntdomalnboundaries[17】,whichindicatesthatthep(2x2)arrangement

whichexistsattheboundariesisstableinthistemperaturerange･

At～ 80K,asshownlnFig.2(C),thec(4x2)structurecoversthesurface･Thestructureofthe

completep(2x2)arrangementisunstableatthistemperature.AsimilarCharacteristicpropertytOthat

obtainedat80Kwasobservedonthesurfaceat30K.Thestructureofthec(4x2)Observedat30Kis

showninFig,2(d).ThlSindicatesthatthec(4x2)structureisthemoststableevenat30K･ASWas

previouslyshown,type Pdefectsexistonthesurface,andwhenthesurfaceisperturbed,rnLgrationof

thetypePdefectsisinitiatedcausingareductionintheareaofthep(2x2)arrangement〔4]･

A【6K,domalnSWiththecompletep(2x2)stn1Cturereemergedonthesu血ce･Figure2(e)Shows

anexampleoftheSTMimageobtainedat～6K,inwhichc(4x2)andp(2x2)structurescoexisHogether,

andf)uctuationbetweenthetwostructureswasobserved.Thephasetransitionbetweenc(4x2)and

p(2x2)structuresisexplainedbythecharacteristicprope托yofthetypePdefectwhichisformedon

dinerrows.NameJy,typePdefecthasastructwesimilartothatofthetypeCdefect,thatis,ilconsists

0ftwoadjacentdimerswhichLLrebuckledwiththesameorientation.lnaddition,sincetheyproducea

phaseshift.migrationofthetypePdefectcausedbythedinerf)ip-flopmotionaHhephaseboundaries

ondinerrowsinducestheapparentphasetransitionbetweenthec(4x2)andp(2x2)arrangements

肝ig･2(d)).WhenthephasedefectaHheboundarymigratesrapidlycomparedtothetimescaleofthe

STMmeasurement,itresultsinthesymmetricimagingofdimersintheSTMmeasurementst5]･

Nextletusconsiderthecharacteristicpropertyofthe

typePdefectusingthekingmodel.Figure3Shows

schematicdiagramsofthearrangementofasymmetric

dimersrepresentedbylsjngsplnS.Ingeneral,thetiltangle

ofthebuckleddinersISassumedtolakeonlytwovalues,♂oand-♂o･Therefore,thermalmotionofthediners

inducesf)ip-flopmotionbetweenthetwoangles.The

absolutevaluesofthecouplingconslantsdeterminedby

lnoueetal.areV=5I.9meV.H=6.6meV,andD=3.6meV

-+ 一一1-■- →

G… H: + I-I--･･:

vr-,-一一p≡_ 二=■ I=

Fig.3SchematicofthelsingSplnmodel

andcouplingconstantsdefinedinterms

ofV,G,H,andD.

[201.Whenatype Pdefectexists,astructurewithparallelspinisintroduced.Inthiscasethecoupling

constantVismodlfiedandbecomesequaltoG,ofabout40meVl21].Herethedefinitionandvalue

ofeachinteractionistakenfromTnoueetaI.

InteractionbetweendlmerSObtainedbylnoueeta】.ishighlyanisotropic･StrongCOrrelalion

alongdimerrowsevenatroomtemperatureWasactuallyconfinedbytheLE仁DmeasuremenlS【151.

Thecharacteristicpropertycol･reSPOndstoourSTMobservationat200K.Asimilarcharacteristicwas

alsoobservedat-6K;C(4x2)Structuraldomainsareformedasone-dimensionalratherthantwo-

62 SurfaceDiqusionandSurfaceStructure

dimensionalstructures･Theseresultsindicatethat (a)一博

interactionbetweendinersisstrongeralongdiner

rowstharHhatbetweenadjacentdinerrows.

Figure4(a)showsascL●iesofSTM Images

takenat200K(Vs=-2･OV.lt=1.OnA),wherea

symmetricdinerreglOnexistsonadinerrow

sandwichedbetweentwobuckleddinerreglOnS.By

companng山ephaseofthebuckユeddinersonei山er

sideofthesymmetricdineral'ea,WeSeethatthere

isonetypePdefectinthesymmetricdinerreglOn,

ThesymmetricdinerregionChangesitsposition

accordingtothemigrationofthetypePdefect,but

isl∝atedonlyaroundtheside.iOfthedinerdomain,

andneverappearsinthecentralpan.Theobserved

resultssuggestthepotentiaJshdpeShowninFig･4(b)

蔚 逐 建碑 J;,i.二二:≡..一一■jp

至萄 -. ' 亮 一-I_一 正

歴 空 軍軍 慧

一丁 . .__･▼

憲 塁-'IleIごO'二oIa'-vOr■ 一竃L_l■■■-

(b) ＼､ーノ //′{ ＼ J

forthetype Pdefect,asafunctionofitsposition

alongthedinerrow.Foranalysispurposes,the (C)

schematicsoranlsingsplnmodelfbr山etwocases

inwhichatype Pdefectexin aroundthesideand (d)centralareaOfthedomainaL.eShowninFigs.4(C)

and4(d),respectively･0111ywhenthenearest-

neighborinteractionalongthedinerrow is

considered,doestheInteractionenergyofthe10

asymmetricdinersinthedomainshowninFigs.

4(C)and4(d)becomethesome:(C)H.o=-10Vand

(d)2H～=-10V･Here,VjstheattractlVeinteraction

er)ergybetweentwodiners.andH meansthesum

▲-

▲T

Hu

11Hu

▲T

▲T

l

･⊥▼

【V〓>&

Fig･4(a)STM imagesofSi(100)surface

continuous一yobtainedat200K,(b)Apotentia一

modelforthetypePdefec【in(a).Schematicsof

theIsingsplnmodelfortwocasesinwhichatype

Pdefec(existsaround(C)theside,and(d)central

areaorthedomain.

oftheintemctionenergiesofnasymmetricdimers･However,theobservedphenomenon(H .o<2H,)is

differentfromthecalculatedresult,andsuggeststheexistenceofalongerrangeinteraction,which

mayalsoagreewiththetendencyofthe2xorderingofthedimerarrangement,

From144Kl16]to30K.acompletec(4x2)structurewasobservedonthesurface,indicatingthe

stronginteractionbetweendimerrows.Infact,whenthesurfaceisperturbed,thec(4x2)structure

recoversbythedynamicsofthetypePdefectsltypePdefectsreamngetheirlocationstoincreasethe

areaofthec(4x2)structure.Figure5Showsanexampleofthestructuralchangeinducedbythe

destructionofatypeCdefectat80K(Vs=一0.6V,It=1.OnA).SlnCetypeCdefectpr∝luceaphaseshift,

ap(2x2)arrangementexistsontheleftofthetypeCdefectindicatedbyanaJTOWinFig･5(a).Inorder

tostudytheinteractionbetweendlmerrows,thetype CdefectwasremovedbyapplylngaVOJtage

usingtheSTM tip.As issh()wncLearly,thep(2x2)domaininFig.5(a)changedintothec(4x2)

arrangementjnFigl5(b).Theobservedchangeisexplainedbythecreationaridmovementofthetype

DefectandDJ'ffusI'onFonJm Vo/S.160-161 63

逮

Fig-5STMimagestakenn【80K(a)beforeand(b)a鮎rdestructionofthe(ypeCdeFectjndicatedby

ana汀OWin(a).

Pdefec【onthedinerrowbythedestructionofthetypeCdefect･Theobservedresultsdirectlyindicate

thestronginteractionbetweendinerrowsandstabilityofthec(4x2)arrangementcomparedtothatof

thep(2x2)arrangementutthlHemperature.

Downto30J(,thep(2x2)domainformedononesideofthe【ype Cdefectwasunstablebutit

stabilizedwhenthetempel-aturewasdecreasedto6K.Letusdiscusstheobservedstructuralchange

from30Kto6K･ThestructL=eOfthep(2x2)arrangementreemergesat6K.Apossibleexp一anationis

torelatetheobservedslfuCrurulchangetothecoherentlengthofthecorrelationofdinerarrangement

alongdinerrows.Whenthecorrelationbecomesstrongeratlowertemperatures,coITeliltionbetween

dinerrowsmaybecomeweaker.However,asiswellknown,theorder-disordertransitiontemperature

isaround200K･Anotherexr)1ilnationistoconsiderthechangeintheinteractionbetweendimers･

SinceintefaCtlOnenergiesoradimerinc(4x2)andp(2x2)arrangementsare-2V十2H-4Dand-2V-

2H+4D,respectively,ChangeintheWDratiomaycausetheobservedsurfacestructuralchange･

Inconclusion,phaseorthebuckleddinerswasfoundtobestrateglCallyrelatedtotheatomic

defectsontheSi(loo)surface.Sincebuckleddinersarefrozenatlowtemperatures,thephaseeffect

becomesmoredomjnarItat一owtemperatures,Fromtheanalysisofthetemperaturedependentdynamics

ofthetypePdefect,interactionbetweendinerswasshowndirectly.

ThisworkwassuppolledbytheShigekawaProjectofTjN ,UniversltyOfTsukuba･Thesupport

ofaGrant-in-AidforScientLrLCResearchfromtheMinistryofEducation,Science,SportsandCulture

ofJapanisalsoacknowledged.

SurfaceDMusionandSurfaceStructu/守

Refbrences

ll]R.J.HamersandU.K.Kohler,J.Vac.Scl.Technol.A7(1989)2854.

[2]H･Shigekawa,K･Miyake.M,Ishida,K.Hata,H.Oigawa,YINaLnnichi,A･Kawazu,

R.Yoshizakj,T.Abe,T.Ozawa,andT.Nagamura,Jpn.J.Appl.Phys135(1996)LIO81･

〔3】H･Shigekawa,K･Miyake.MJshda,K･Hata,Jpn･J･Appl･Phys･36(1997)L294･

[4】llShigekawa,K.Miyake.MJshida,K.Hata,Sci.Rep.RITUA44(1997)67･

〔5】H･Shigekawa,K･Hata,K･Miyake,M.Ishida,S･Ozawa,Phys･Rev･B55(1997)15448･

[6]JIWang,T･A･Arias,andJ･0･Joannopoulos,Phys･Rev･B47(1993)10497

[7]J.H.G.Owen,D R.Bow一er,C.M.Goringe,K.Miki,andG.A.D.Briggs,Surf.Sci.,341,

(1995)LIO42.

[8]F･KIMen,A.R.Smith,K.J.Chao.Z.Y.Zhang,andC.K Shih,Phys.Rev.B52(1995)R8650.

【9】M Uchikawa,M.Ishida,K.Miyake,R.Yoshzaki,K.Hata,andH.Shigekawa,SU工f･S°i.,

357/358(1996)468.

[10]H･Shigekawa,K･Mlyake.M･Ishida,KIHa【a,T･SatoandM･Iwatsuki,tobepublished･

Bias-dependentSTMmeLISurementisapplicablefortheanalysisofthedefectsonSi(111)surface,

K･Miyake,H･ShigekawaandR.YoshiZaki,Appl.Phys･Lett･66(1995)3468･

lll]T.UdaandK.Terakum.Phys.Rev.B53(1996)6999.

tl2]K･Hata,S,Ozawa,K.Miyake,H.Shigekawa,tobepublished.

[13]K･Hata,K･Miyake,M･lshida.H･Shigekawa,Appl,Phys.Lett.,inpress.

[14]A･Ramstad,G.Blocks,andP.J.Kelly,Phys.Rev.B51(1995)j4504.

日5】T.Tabata,T.ArugaandYMurata,Surf.S°i.179(1987)L63.

[16]H･Tochihara,T･Amaku叫 andM.Iwatsuki,PhysRev,B50(1994)12262.

【17】R.A.Wolkow,Phys.Rev.Left.,68(1992)2636.

[18]A.R.Smith,F.K.Men.KJ,Chao,andC.Shih,J.Vac.Sci.TechnoJ.B14(L996)914.

[19]J.E.Norlhrup,Phys.Rev.B,47(1993)10032.

[20]K･Inoue,Y･Morikawa･K,TerakuraandM.Nakayama,Phys.Rev.B49(J994)14774.

[21]Y･Nakamura,H KawaiaridM Nakayama,Phys.Rev.B52(1995)8231.

Forcorrespondence,

Electronicmai一:hidemi@mal.ims.tsukuba.acJP

http:〟www.ims･tsukuba.ac.jp/lab/shgekawa

Fax:十8ト298-55-7440