表面重構(gòu)課-薛其坤課件

表面重構(gòu)OutlineBriefintroductionBondingatasurface2.PrincipleofSurfaceReconstruction

3.ReconstructionElements3.1Chains3.2Dimers(trimers)3.3Adatoms4.Typicalreconstructionsurfaces

4.1MetalSurface4.2InsulatorSurface4.3SemiconductorSurface5.Summary1.BriefintroductionTwotypesofatomicrearrangements

RelaxationReconstruction

Wood：A(hkl)-nm--BBondingatasurfaceWhy原子間的鍵合（1）Surface:heterogeneousatmicroscopicscale（2）Surfaceprocesses:adsorption/desorption,diffusion,reaction……

外來原子與表面原子的相互作用/鍵合金屬鍵共價鍵（Si，Ge，GaAs/InAs/AlAs,GaN,ZnO…）離子鍵（MgO,Al2O3,NaCl…)孤立分子中原子間的成鍵固體中原子間的成鍵psahb化學(xué)鍵局域化學(xué)鍵的角度去理解晶體中原子的鍵合OrbitalsandBondingOne-ElectronPicture1023-bodyproblem兩個軌道間的成鍵雙原子分子（H2或者LiH）H11–

H12–

S12H*11–S*12

H22–()()12=0a,i

(x)=

aia(x–Ri)LiHs(H)s(Li)AtomicOrbitalsandTheirInteractionANB8-N三個假定：（1）s,Px,Py

and

Pz（2）Sab(Ri–Rj)=abij

（3）最近鄰和次近鄰相互作用

，

且Hab(Ri,Rj)=Hab(Ri–Rj)d=Ri–RjpdnnnL?wdinTheorem：Sab(Ri–Rj)=abij

BondingHybridsElectronsarelocalizedbetweenatomsalongthebondingdirection

Atomicorbitalsalongthebondingdirectionsp3雜化sp2雜化sp雜化AB(1)同原子內(nèi)軌道相互作用1A(1B)2A(2B)(2)原子之間軌道相互作用34465^ahbsp3Hirabayashi,J.Phys.Soc.Jpn.27.1475(1969)KJ2DwavevectorJ’對電子態(tài)的影響對電子態(tài)的影響br=sp3–

2DB=sp3+

2(110)KJ2DwavevectorJ’2.PrincipleofReconstructionThesurfacestructureobservedwillbethelowestfree-energystructurekineticallyaccessibleunderthepreparationconditions.

Si(111)-2x1→7x7byannealing

Ge(111)-2x1→c(2x8)byannealingBothoftheabovearestableuponsubsequentcoolingindicatethatthefirst2x1structureobtainedbylow-temperaturecleavageisonlyalocalstablestructure,butnotthelowestfree-energystructurewhichisobtainedforbothsurfacesbyannealingandsubsequentcooling.Inthetwoprocesses,hightemperatureisnecessarytoovercometheenergybarrierbetweendifferentstructureandtogeneratetheadatomsinthelowestfree-energystructure.BasicPrinciple：費米能級以下的表面態(tài)必須全部占據(jù)Bondingandnon-bondingsurfacestates費米能級以上的表面態(tài)必須全部空著non-bondingandantibondingstatesElectronCountingModel3.ReconstructionElements3.1Chains3.2Dimers(trimers)3.3Adatoms2.1ChainsZig-zagchainsBinaryIV-IV(SiC),III-VandII-VIcompoundsemiconductorshaveplanarzig-zagchainsofalternatingcationsandanionsalonga<-110>directionintheir{110}surfaces(111)-2x1UsingNNapproximationofTBA,consideringtheDBinteractionBandstructureof

-bondedchainmodel

twosurfacebandsV=H12(d1)+H12(d2)S(k)=ieikdi~Trimer2.3Adatomsoftenon(111)surfaces[110][112][111][112]4.Typicalreconstructionsurfaces4.1MetalSurfaces4.2InsulatorSurfaces4.3SemiconductorSurfaces

4.1MetalSurfaceAlthoughmostmetalsurfacesarerelaxedinsteadofrecosntruction,somenobleandnear-noblefccmetals,Au,Ir,Ptandbcctransitionmetals,WandMo,displayrecosntructions.W?lletal.Phys.Rev.B39,7988-7991(1989)1x2missing-rowreducesthesurfaceenergy.Pt(110),Au(110)T.R.Linderoth,S.Horch,E.L?gsgaard,I.Stensgaard,andF.Besenbacher,PRL,78,49784.2InsulatorSurfacesNaCl(111)-1x1Hebenstreitetal.,Phys.Rev.Lett.85,5376(2000)(a)50nmx50nm,21.2V,0.06nA.(b)NaCl(111)islandwithatomicresolution(7nmx7nm,21.2V,0.3nA).(c)StructuremodelofanNaCl(111)island.C(100)-2x1Bobrovetal.,Natrue413,616(2001)4.3SemiconductorSurfacesChem.Rev.96,1237-1259(1996)CharlesB.DukeSTMonIII-V(100)SurfaceReconstructionsXueetal.,ProgressinSurfaceScience56,p001-p131(1997)ElementsemiconductorsurfaceSi(100)industrySi(111)cleavedGe(111)Ge(100)

K.Oura,V.G.Lifshitsetal.<SurfaceScience-AnIntroduction>Si(001)surface(001)Dimerization:reducedanglingbonds(110)Si(100)-2x1Trompetal.,PRL1985Si(100)-2x1→c(4x2)filledstates(-1.0V)emptystates(1.0V)at63K.UnitcellTakashiYokoyama*etal.PRB,61,8Si(111)Si(111)-2x1

7x7

disorder”1x1”(metastable)

Heatingtoabout400Heatingtoabout850irreversiblyreversiblySi(111)-2x1K.C.Pandey,PRL,47,26The

-bondedchainmodelbyPandeyforthecleavedSi(111)-2x1structure.CompoundsemiconductorsurfaceGaAs(110)GaAs(100)GaAs(111)Verycomplicated!GaAs(110)TheGaAs(110)isthecleavagesurface,thereconstructedsurfacestillpreservesanideal1x1periodicity.SuchareconstructionistypicalforzincblendestructureIII-VsemiconductorswithbucklingangleGaAs(110)R.M.Feenstraetal.,PRL1987110AsGaemptyfilledGaAs(110)R.M.Feenstraetal.,PRL1987110TheGaAs(110)isthecleavagesurface,thereconstructedsurfacestillpreservesanideal1x1periodicity.SuchareconstructionistypicalforzincblendestructureIII-VsemiconductorswithbucklingangleAsGaGaAsc(4x4),2x4/c(2x8),2x6,3x1,1x3,4x2/c(8x2),4x6……As-richGa-richGa覆蓋度增加方向GaAs(001)：oneofthemostimportantsurfaces[001][110][110]GaAs(001)-1x1surface(001)Dimerization:reducedanglingbonds(110)AsGa(110)(110)Top-view費米能級以下的表面態(tài)必須全部占據(jù)Bondingandnon-bondingsurfacestates費米能級以上的表面態(tài)必須全部空著non-bondingandantibondingstatesElectronCountingModelXueetal.,ProgressinSurfaceScience,56,(1997)p1-p131s(110)(110)Top-viewSide-viewModelsof2x4SurfaceGaAs(001)As-rich2x4As-Rich2x4HashizumeandXueetal.,PRL73,2208（1994）[110][110][110][110]GaAs(001)-2x4surface(110)(110)Bilayertwo-As-dimermodelThree-As-dimermodelHashizumeandXueetal.,PRL73,2208（1994）AnothertwomodelsTwo-As-dimermodelwithsecondlayerGadimerizedExtra-As-dimermodel(110)(110)GaAs(001)Ga-rich4x2surfaceThree-Ga-dimermodelGa-bilayermodelAsmodel(110)(110)GaAsSTMimageofGa-rich4x6structureXueetal.Phys.Rev.Lett.74,3177(1995)MirrorsymmetryofAs-rich2x4andGa-rich4x2As-rich2x4Ga-rich4x2MonolayerofGaadsorptiononAs-richsurfaceresultsinGa-rich4x2phase,MonolayerofAsadsorptiononGa-richsurfaceresultsinAs-rich2x4phase.PhaseevolutiondiagramQ.K.Xue,T.Hashizume,andT.Sakurai,"ScanningTunnelingMicroscopyofIII-VCompoundSemiconductor(001)Surface",ProgressinSurfaceScience56,P1-P132(1997)Si(111)-7x7reconstructionSchlierandFarnsworth,J.Chem.Phys30,917(1959)TheoreticmodelofSi(111)-7x7Adatoms(add-atoms)intheoutermostlayerwasproposedbyHarrison.Whiletheenergytoformavacancyonasilicon(111)surfaceisverylarge,siliconatomsoutsidethenominalsurfaceshouldbequitestable.Thissuggeststhatthe7×7reconstructionisapatternofadd-atomsratherthanapatternofvacancies.Harrison,Surf.Sci.55,1

TheLEED:stackingfaultinthesurfacelayer

Bennettetal,PRB1983STM:Binnigetal.PRL50,120Basedontheaboveobservations,Himpsel(leftbelow)andMcRae(rightbelow)predictedthattheboundarybetweenthefaultedandunfaultedtriangularsubunitsincorporatesanarrayofdimersanddeepholes.

PRB.27,12PRB.28,4TEDbyTakayanagietal.

Modelwithdimers,adatomsandstackingfaults,whichknownasDASmodel.Takayanagi,Surf.Sci.164,36710?FaultedHalfUnfaultedHalfAdatomRestatomCornerhole112110ElectronicstructureofDASmodel+2v+1.45v-1.45v-0.35v-0.8v-1.7v小結(jié):半導(dǎo)體表面(100)-like表面：2DBs/atom。dimer形成其主導(dǎo)作用。對化合物,dimer-missing

再構(gòu)：偶數(shù)x偶數(shù)

1D特點:Buckling/tilting/distortion(111)-like表面：1DBs/atom。adatom形成其主導(dǎo)作用。再構(gòu)：奇數(shù)x奇數(shù)（有理數(shù)x有理數(shù)）3.Stronginteractiondirection:strongdispersion2inchSiwafer100nmx100nm27nmx27nmSi(111)-7x7上的Al納米團簇的有序陣列Lietal.,Phys.Rev.Lett.

88,066101(2002)Jiaetal.,Phys.Rev.B66,165408(2002)Jiaetal.,Appl.Phys.Lett.80,3186(2002)Summary

Surfaceisbeautiful

SmallisbeautifulThankyou!HowECRworksinpracticeForGaAs,Vn=5,Vp=3,thus:M.D.Pashley,Phys.Rev.B40,10481(1990)Satisfytheprinciplesofsemiconductorsurfacereconstrucion

Principle1.Reconstructiontendeithertosaturatesurface“dangling”bongdviarehybridizationortoconvertthemintononbondingelectronicstates.Principle2.Surfacecanlowertheirenergiesbyatomicrelaxationsleadingtosemiconducting(asopposedtometallic)surfacestateeigenvaluespectra.Principle3.Thesurfacestructureobservedwillbethelowestfree-energystructurekineticallyaccessibleunderthepreparationconditions.Principles1-3areonlyforspace-chargefreeelementalsemiconductors,butforcompoundsemiconductorsprinciples1-2willbereplacedbyotherprinciples.C.B.DukeChem.Rev,96,1237Xueetal.,ProgressinSurfaceScience,56,(1997)pp.1-131sBandstructureofGaAs(001)

whichissp3hybridizedinthebulkGaAs(001)As-rich2x4RHEED[110]595oC550oC505oC2.ReconstructionElements

2.1ReconstructionandBondingsp3雜化sp2雜化sp雜化s-likedanglinghybridPz-likedanglinghybrid(111)(100)關(guān)于GaAs(001)和GaN(0001)表面重構(gòu)的文章

GaAs(111)isapolarsurfacewhichcontainstwoterminatedsurfaces.＊Ga-terminated(111)surface,alsocalledGaAs(111)orGaAs(111)Asurface.＊As-terminated(111)surface,alsocalledGaAs(-1-1-1)orGaAs(111)BsurfaceBothofthemexhibit2x2reconstructions,butthesereconstructionsareessentiallydifferent.GaAs(111)GaAs(111)Asurface.K.W.Heberern,M.D.Pashley,PRB,41,5Inthisrecosntruction,oneoutofeveryfourGa