薄膜制備與表面分析

ThinFilmSynthesisandSurfaceAnalysisQing-YuZhangStateKeyLaboratoryforMaterialsModificationbyLaser,IonandElectronBeams概論表面及表面科學(xué)

固體的表面、或者說界面，在人們的社會(huì)實(shí)踐中起著極為重要的作用。表面科學(xué)的研究，對(duì)整個(gè)科學(xué)技術(shù)的發(fā)展具有重要的意義。表面科學(xué)包括表面物理、表面化學(xué)、表面電子學(xué)、表面生物學(xué)等。

概論表面及表面科學(xué)固體表面：物體與真空或氣體的界面。固體表面可以指從單一的第一個(gè)原子層到幾個(gè)原子層厚度的表面層，甚至深達(dá)幾個(gè)微米的表面層。在熱力學(xué)平衡的條件下，固體表面的化學(xué)組成、微觀結(jié)構(gòu)、原子振動(dòng)狀態(tài)等均會(huì)與固體內(nèi)部產(chǎn)生一定的差異。概論表面分析技術(shù)表面分析技術(shù)是人們?yōu)榱双@取表面的物理、化學(xué)等方面的信息而采用的一些實(shí)驗(yàn)方法和手段。SampleExcitationsourceEnergySelectorSignalDetectorEvent概論表面分析技術(shù)一般地說，它是利用一種探測束——如電子束、離子束、光子束、中性粒子束等，有時(shí)還加上電場、磁場、熱等的作用，來探測材料的形貌、化學(xué)組成、原子結(jié)構(gòu)、原子狀態(tài)、電子狀態(tài)等方面的信息。

概論表面分析技術(shù)探測粒子發(fā)射粒子分析方法名稱簡稱主要用途ee低能電子衍射LEED結(jié)構(gòu)ee反射式高能電子衍射RHEED結(jié)構(gòu)ee俄歇電子能譜AES成分ee掃描俄歇探針SAM微區(qū)成分ee電離損失譜ILS成分e能量彌散x射線譜EDXS成分ee俄歇電子出現(xiàn)電勢譜AEAPS成分e軟x射線出現(xiàn)電勢譜SXAPS成分ee消隱電勢譜DAPS成分ee電子能量損失譜EELS原子及電子態(tài)eI電子誘導(dǎo)脫附ESD吸附原子態(tài)及成分ee透射電子顯微鏡TEM形貌ee掃描電子顯微鏡SEM形貌ee掃描透射電子顯微鏡STEM形貌概論表面分析技術(shù)探測粒子發(fā)射粒子分析方法名稱簡稱主要用途

ex射線光電子譜XPS成分、化合態(tài)

e紫外線光電子譜UPS分子及固體電子態(tài)

e同步輻射光電子譜SRPES成分、原子及電子態(tài)紅外吸收譜IR原子態(tài)拉曼散射譜RAMAN原子態(tài)

擴(kuò)展x射線吸收譜精細(xì)結(jié)構(gòu)SEXAFS結(jié)構(gòu)

角分辨光電子譜ARPES原子及電子態(tài)結(jié)構(gòu)

I光子誘導(dǎo)脫附譜PSD原子態(tài)概論表面分析技術(shù)探測粒子發(fā)射粒子分析方法名稱簡稱主要用途Ee場電子顯微鏡FEM結(jié)構(gòu)EI場離子顯微鏡FIM結(jié)構(gòu)EI場離子顯微鏡-原子探針AP-FIM結(jié)構(gòu)及成分Ee場電子發(fā)射能量分布FEED電子態(tài)Ee掃描隧道顯微鏡STM形貌Tn熱脫附譜TDS原子態(tài)n中性粒子碰撞誘導(dǎo)輻射SCANIIR成分n

n分子束散射MBS結(jié)構(gòu)、原子態(tài)AWAW聲顯微鏡AM形貌概論表面分析技術(shù)部分表面分析設(shè)備的分析范圍

概論真空技術(shù)原理為了使被研究的樣品不被周圍氣氛所污染，獲取“原子清潔”的表面，表面分析過程往往是在真空或超高真空中進(jìn)行的。目前，人們所廣泛使用的很多表面分析設(shè)備都具有真空系統(tǒng)。薄膜制備設(shè)備往往涉及真空系統(tǒng)。概論真空技術(shù)原理真空單位Atmospheres(atm):

Scalerelativetoouratmosphericpressureas1atmPascal(Pa):SIunitequaltoN/m2mBar:Equalto1x10-8Pa.

TorrormmHg:Mostcommonlyusedpressureunit,basedonmercuryvacuumgauges.概論真空技術(shù)原理真空的劃分Atmospheric:760TorrLowVacuum:1to1x10-3

TorrMediumVacuum:1x10-3to1x10-5

TorrHighVacuum(HV):1x10-6to1x10-8

TorrUltra-HighVacuum(UHV):<1x10-9

Torr概論真空技術(shù)原理真空的意義ImpingementRate(Flux)Foranidealgas,theimpingementrateisgivenby: ZA=ρv/4where,ρ-thenumberdensityofgasmoleculesv-themeanvelocity概論真空技術(shù)原理DegreeofVacuumPressure

(Torr)GasDensity,ρ

(moleculesm-3)MeanFreePath

(m)Time/ML,tML

(s)Atmospheric7602x10257x10-810-9Low13x10225x10-510-6Medium10-33x10195x10-210-3High10-63x1016501UltraHigh10-103x10125x105104CollisionFreeConditions:P~10-6TorrMaintainaCleanSurface:P~10-10Torr概論真空技術(shù)原理真空的獲得UltimatePressureLowVacuum(Rough)PumpsRotaryVanePumpsSorptionPumpsHighVacuumPumpsDiffusionPumpsTurboMolecularPumpsUltra-HighVacuumTurboMolecularPumpsIonPumpsTitaniumSublimationPumpsOil/Oil-FreeOilRotaryVanePumpsDiffusionPumpsTurboMolecularPumpsOil-FreeTurboMolecularPumpsIonPumpsTitaniumSublimationPumps概論真空技術(shù)原理真空的獲得LN2cooledmolecularsievewithlargesurfaceareaAtmto10-3

Torr(twounitsworkingalternately)QuicklybecomessaturatedMustbebakedat>200°CtoremoveadsorbedgasesSimple,inexpensive,oil-free概論真空技術(shù)原理真空的獲得MomentumtransfertogasmoleculesthroughcollisionwithdirectedjetofoilmoleculesRequirecoolingwater,backingpump10-3to10-7

Torr(to10-9

TorrwithLN2cooling)AdvantagesRobustHighpumpingspeedforrelativelylowcost.Novibrationornoise.DisadvantagesOilasapumpingmedium,highriskofback-streamingoil,coldtrapsrequiredPotentialforseriousvacuumproblems

概論真空技術(shù)原理真空的獲得Moleculesmechanicallypumpedbycollisionwithangledhighspeedturbineblades(rotor).Severalrotorarrangedinaseriesspinningat30,000-60,000rpm.Rotortangentialvelocityisontheorderoftheaveragethermalvelocityofmolecules.Atmosphereto10-10

TorrOil/grease/electromagneticbearingsMostcommonHV/UHVpump.概論真空技術(shù)原理真空的獲得Highvoltagebetweenanodeandcathode(~5kV)Electronsarecapturedinanodeandspiralduethetomagneticfield(longerpath-length).Gasmoleculesareionizedbycollisionswithelectronsandareacceleratedtocathode.Ionsembeddedincathodematerial(titanium)andsputtertitaniumatomsfromsurface.SputteredTiatomsactas"getter"forreactivegases.10-4

Torrto10-11

Torr概論真空技術(shù)原理真空的獲得AdvantagesClean,oil-free.Nomovingparts,novibrations,quiet.LowpowerconsumptionandrelativelylongoperatinglivesDisadvantage

Donotpumpnoblegaseswell.Requires“regeneration”ofTievery4-6years.概論真空技術(shù)原理真空的獲得HeatedTifilamentevaporatesTifilmontocooledsurface.Tigettersreactivegasesbyreaction.Operateat10-8-10-11

TorrInexpensive,reliablePeriodicoperation-notprimarypumpingmechanism概論真空技術(shù)原理真空的獲得Oxygenfreehigh-puritycopper(OFHC)Be-CualloyTantalum,Molybdenum,TungstenTeflon(gassy)MACOR(machinableglasscomposite)

Alumina

Quartz,pyrex(gassy)"mu-metal"magneticshielding(Co,Ni,Fe)Molybdenumdisulfide(lubricant)CompatibleMaterials

概論真空技術(shù)原理MaterialstobeAvoided

(highvaporpressures)

Zn,Cd:especiallybecarefuloffasteners,boltsBrassCertainsoldersAnytypeofgreaseoroils真空的獲得CommonVacuumProblemsImpropercleaningorhandlingtechniquesUsingincompatiblematerialsLeaksVirtualleaks概論真空技術(shù)原理真空的獲得概論真空技術(shù)原理真空的獲得概論真空技術(shù)原理真空的獲得PumpDownTypicallyfollowsawell-definedsequenceaccordingtothetypesofpumpsonthevacuumsystemForUHVsystems,typicallyrequiresafewhourstoreachamediumvacuumafteraventtoairBakeOutHeatthechambertotemperaturesbetween100oCand200oCfor1-2days.Rapidlyremoveadsorbedgasesfromthechamberwallsathightemperaturesinordertolowertheoutgassingratesatroomtemperature.Generallyittakesanotherdaytocoolandrecoverbasepressure.概論真空技術(shù)原理真空的測量Heatfilamentwithaconstantcurrent.Measurefilamenttemperaturewiththermocouple.Gasmoleculescollidewithandcoolthefilament.Voltageincreasestokeepfilamentatconstantcurrent.Atmto10-4

TorrFast,simple,inexpensive.ThermocoupleGauge概論真空技術(shù)原理真空的測量Twoidenticalheatedfilaments;onesealedatHV,oneexposedtosystem.CurrentflowsthroughWheatstonebridgecircuit.Pressuredifferenceindicatedbymeter(non-linear).Atmto10-4

torr.Simple,reliable,inexpensive.PiraniGauge概論真空技術(shù)原理真空的測量Heatedfilamentproduceselectronsviathermionicemission.Electronsareacceleratedtowardsanodegrid.Manyelectronspassthroughthegridandcreatepositiveionsfromcollisionswithgasmolecules.Ionsareacceleratedtocollec