薄膜制备与分析课件

薄膜制备与表面分析

ThinFilmSynthesisandSurfaceAnalysisQing-YuZhangStateKeyLaboratoryforMaterialsModificationbyLaser,IonandElectronBeams概论表面及表面科学

固体的表面、或者说界面，在人们的社会实践中起着极为重要的作用。表面科学的研究，对整个科学技术的发展具有重要的意义。表面科学包括表面物理、表面化学、表面电子学、表面生物学等。

概论表面及表面科学固体表面：物体与真空或气体的界面。固体表面可以指从单一的第一个原子层到几个原子层厚度的表面层，甚至深达几个微米的表面层。在热力学平衡的条件下，固体表面的化学组成、微观结构、原子振动状态等均会与固体内部产生一定的差异。概论表面分析技术表面分析技术是人们为了获取表面的物理、化学等方面的信息而采用的一些实验方法和手段。SampleExcitationsourceEnergySelectorSignalDetectorEvent概论表面分析技术一般地说，它是利用一种探测束——如电子束、离子束、光子束、中性粒子束等，有时还加上电场、磁场、热等的作用，来探测材料的形貌、化学组成、原子结构、原子状态、电子状态等方面的信息。

概论表面分析技术探测粒子发射粒子分析方法名称简称主要用途ee低能电子衍射LEED结构ee反射式高能电子衍射RHEED结构ee俄歇电子能谱AES成分ee扫描俄歇探针SAM微区成分ee电离损失谱ILS成分e能量弥散x射线谱EDXS成分ee俄歇电子出现电势谱AEAPS成分e软x射线出现电势谱SXAPS成分ee消隐电势谱DAPS成分ee电子能量损失谱EELS原子及电子态eI电子诱导脱附ESD吸附原子态及成分ee透射电子显微镜TEM形貌ee扫描电子显微镜SEM形貌ee扫描透射电子显微镜STEM形貌概论表面分析技术探测粒子发射粒子分析方法名称简称主要用途

ex射线光电子谱XPS成分、化合态

e紫外线光电子谱UPS分子及固体电子态

e同步辐射光电子谱SRPES成分、原子及电子态红外吸收谱IR原子态拉曼散射谱RAMAN原子态

扩展x射线吸收谱精细结构SEXAFS结构

角分辨光电子谱ARPES原子及电子态结构

I光子诱导脱附谱PSD原子态概论表面分析技术探测粒子发射粒子分析方法名称简称主要用途Ee场电子显微镜FEM结构EI场离子显微镜FIM结构EI场离子显微镜-原子探针AP-FIM结构及成分Ee场电子发射能量分布FEED电子态Ee扫描隧道显微镜STM形貌Tn热脱附谱TDS原子态n中性粒子碰撞诱导辐射SCANIIR成分n

n分子束散射MBS结构、原子态AWAW声显微镜AM形貌概论表面分析技术部分表面分析设备的分析范围

概论真空技术原理为了使被研究的样品不被周围气氛所污染，获取“原子清洁”的表面，表面分析过程往往是在真空或超高真空中进行的。目前，人们所广泛使用的很多表面分析设备都具有真空系统。薄膜制备设备往往涉及真空系统。概论真空技术原理真空单位Atmospheres(atm):

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

TorrormmHg:Mostcommonlyusedpressureunit,basedonmercuryvacuumgauges.概论真空技术原理真空的划分Atmospheric:760TorrLowVacuum:1to1x10-3

TorrMediumVacuum:1x10-3to1x10-5

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

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

Torr概论真空技术原理真空的意义ImpingementRate(Flux)Foranidealgas,theimpingementrateisgivenby: ZA=ρv/4where,ρ-thenumberdensityofgasmoleculesv-themeanvelocity概论真空技术原理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概论真空技术原理真空的获得UltimatePressureLowVacuum(Rough)PumpsRotaryVanePumpsSorptionPumpsHighVacuumPumpsDiffusionPumpsTurboMolecularPumpsUltra-HighVacuumTurboMolecularPumpsIonPumpsTitaniumSublimationPumpsOil/Oil-FreeOilRotaryVanePumpsDiffusionPumpsTurboMolecularPumpsOil-FreeTurboMolecularPumpsIonPumpsTitaniumSublimationPumps概论真空技术原理真空的获得LN2cooledmolecularsievewithlargesurfaceareaAtmto10-3

Torr(twounitsworkingalternately)QuicklybecomessaturatedMustbebakedat>200°CtoremoveadsorbedgasesSimple,inexpensive,oil-free概论真空技术原理真空的获得MomentumtransfertogasmoleculesthroughcollisionwithdirectedjetofoilmoleculesRequirecoolingwater,backingpump10-3to10-7

Torr(to10-9

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

概论真空技术原理真空的获得Moleculesmechanicallypumpedbycollisionwithangledhighspeedturbineblades(rotor).Severalrotorarrangedinaseriesspinningat30,000-60,000rpm.Rotortangentialvelocityisontheorderoftheaveragethermalvelocityofmolecules.Atmosphereto10-10

TorrOil/grease/electromagneticbearingsMostcommonHV/UHVpump.概论真空技术原理真空的获得Highvoltagebetweenanodeandcathode(~5kV)Electronsarecapturedinanodeandspiralduethetomagneticfield(longerpath-length).Gasmoleculesareionizedbycollisionswithelectronsandareacceleratedtocathode.Ionsembeddedincathodematerial(titanium)andsputtertitaniumatomsfromsurface.SputteredTiatomsactas"getter"forreactivegases.10-4

Torrto10-11

Torr概论真空技术原理真空的获得AdvantagesClean,oil-free.Nomovingparts,novibrations,quiet.LowpowerconsumptionandrelativelylongoperatinglivesDisadvantage

Donotpumpnoblegaseswell.Requires“regeneration”ofTievery4-6years.概论真空技术原理真空的获得HeatedTifilamentevaporatesTifilmontocooledsurface.Tigettersreactivegasesbyreaction.Operateat10-8-10-11

TorrInexpensive,reliablePeriodicoperation-notprimarypumpingmechanism概论真空技术原理真空的获得Oxygenfreehigh-puritycopper(OFHC)Be-CualloyTantalum,Molybdenum,TungstenTeflon(gassy)MACOR(machinableglasscomposite)

Alumina

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

概论真空技术原理MaterialstobeAvoided

(highvaporpressures)

Zn,Cd:especiallybecarefuloffasteners,boltsBrassCertainsoldersAnytypeofgreaseoroils真空的获得CommonVacuumProblemsImpropercleaningorhandlingtechniquesUsingincompatiblematerialsLeaksVirtualleaks概论真空技术原理真空的获得概论真空技术原理真空的获得概论真空技术原理真空的获得PumpDownTypicallyfollowsawell-definedsequenceaccordingtothetypesofpumpsonthevacuumsystemForUHVsystems,typicallyrequiresafewhourstoreachamediumvacuumafteraventtoairBakeOutHeatthechambertotemperaturesbetween100oCand200oCfor1-2days.Rapidlyremoveadsorbedgasesfromthechamberwallsathightemperaturesinordertolowertheoutgassingratesatroomtemperature.Generallyittakesanotherdaytocoolandrecoverbasepressure.概论真空技术原理真空的测量Heatfilamentwithaconstantcurrent.Measurefilamenttemperaturewiththermocouple.Gasmoleculescollidewithandcoolthefilament.Voltageincreasestokeepfilamentatconstantcurrent.Atmto10-4

TorrFast,simple,inexpensive.ThermocoupleGauge概论真空技术原理真空的测量Twoidenticalheatedfilaments;onesealedatHV,oneexposedtosystem.CurrentflowsthroughWheatstonebridgecircuit.Pressuredifferenceindicatedbymeter(non-linear).Atmto10-4

torr.Simple,reliable,inexpensive.PiraniGauge概论真空技术原理真空的测量Heatedfilamentproduceselectronsviathermionicemission.Electronsareacceleratedtowardsanodegrid.Manyelectronspassthroughthegridandcreatepositiveionsfromcollisionswithgasmolecules.Ionsareacceleratedtocollec