《薄膜制备与分析》PPT课件

薄膜制备与表面分析ThinFilmSynthesisandSurfaceAnalysis,Qing-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。,概论表面及表面科学,Sinceitrequiresenergytoterminatethebonding,thesurfaceisenergeticallylessstablethanthebulk.,Thisenergyisknownasthesurfacefreeenergy.Inthecaseofliquidinterfaces,thisenergyiscalledsurfacetension.,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。,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,概论表面分析技术,概论表面分析技术,概论表面分析技术,概论表面分析技术,部分表面分析设备的分析范围,概论表面分析技术,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:1to1x10-3TorrMediumVacuum:1x10-3to1x10-5TorrHighVacuum(HV):1x10-6to1x10-8TorrUltra-HighVacuum(UHV):200CtoremoveadsorbedgasesSimple,inexpensive,oil-free,概论真空技术原理,真空的获得,MomentumtransfertogasmoleculesthroughcollisionwithdirectedjetofoilmoleculesRequirecoolingwater,backingpump10-3to10-7Torr(to10-9TorrwithLN2cooling),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.Atmosphereto10-10TorrOil/grease/electromagneticbearingsMostcommonHV/UHVpump.,概论真空技术原理,真空的获得,AdvantagesCorrectlyoperatedtheydonotback-streamoilintothevacuumsystematanytime.Theycanbestartedandstoppedinafewminutestime.DisadvantageTurbopumpcanbenoisyandtheyinducevibration.Turbopumpsareexpensive.,概论真空技术原理,真空的获得,Highvoltagebetweenanodeandcathode(5kV)Electronsarecapturedinanodeandspiralduethetomagneticfield(longerpath-length).Gasmoleculesareionizedbycollisionswithelectronsandareacceleratedtocathode.Ionsembeddedincathodematerial(titanium)andsputtertitaniumatomsfromsurface.SputteredTiatomsactasgetterforreactivegases.10-4Torrto10-11Torr,概论真空技术原理,真空的获得,AdvantagesClean,oil-free.Nomovingparts,novibrations,quiet.LowpowerconsumptionandrelativelylongoperatinglivesDisadvantageDonotpumpnoblegaseswell.Requires“regeneration”ofTievery4-6years.,概论真空技术原理,真空的获得,HeatedTifilamentevaporatesTifilmontocooledsurface.Tigettersreactivegasesbyreaction.Operateat10-8-10-11TorrInexpensive,reliablePeriodicoperation-notprimarypumpingmechanism,概论真空技术原理,真空的获得,MaterialsConsiderations,OutgassingratesProducing“virtual”leaksMechanicalstabilityTemperaturestability,ConductivityChemicalinertnessWeldability,概论真空技术原理,真空的获得,Oxygenfreehigh-puritycopper(OFHC)Be-CualloyTantalum,Molybdenum,TungstenTeflon(gassy)MACOR(machinableglasscomposite)AluminaQuartz,pyrex(gassy)mu-metalmagneticshielding(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,typicallyrequiresafewhourstoreachamediumvacuumafteraventtoair,BakeOutHeatthechambertotemperaturesbetween100oCand200oCfor1-2days.Rapidlyremoveadsorbedgasesfromthechamberwallsathightemperaturesinordertolowertheoutgassingratesatroomtemperature.Generallyittakesanotherdaytocoolandrecoverbasepressure.,概论真空技术原理,真空的测量,Heatfilamentwithaconstantcurrent.Measurefilamenttemperaturewiththermocouple.Gasmoleculescollidewithandcoolthefilament.Voltageincreasestokeepfilamentatconstantcurrent.Atmto10-4TorrFast,simple,inexpensive.,ThermocoupleGauge,概论真空技术原理,真空的测量,Twoidenticalheatedfilaments;onesealedatHV,oneexposedtosystem.CurrentflowsthroughWheatstonebridgecircuit.Pressuredifferenceindicatedbymeter(non-linear).Atmto10-4torr.Simple,reliable,inexpensive.,PiraniGauge,概论真空技术原理,真空的测量,Heatedfilamentproduceselectronsviathermionicemission.Electronsareacceleratedtowardsanodegrid.Manyelectronspassthroughthegridandcreatepositiveionsfromcollisionswithgasmolecules.Ionsareacceleratedtocollectorwire.Measurethecurrentbetweenanodeandcollector.Operateat10-4to10-11TorrSensitive,highaccuracy,widelyused.,IonGauge(Bayard-Alpert),概论真空技术原理,真空的测量,Quadrupolemassspectrometer-RGA(residualgasanalyzer)10-4to10-14torrTotalpressuremodeintegratesallionintensitiesPartialpressuremodeindicatesresidualvacuumcompositionHighlyaccurate,preciseComplex,expensive.,MassSpectr