透射电子显微镜TEM

透射电子显微镜TransmissionElectronMicroscopy当代分析措施与技术目录Contents透射电子显微镜21历史History2原理Background3构造Components4制备Preparation5应用Application历史History最初研究Initialdevelopment透射电子显微镜3ErnstAbbe(*23.Januar1840;†14.Januar1905),deutscherAstronom对物体细节的分辨率受到用于成像的光波波长的限制Theabilitytoresolvedetailinanobjectwaslimitedapproximatelybythewavelengthofthelightusedinimaging光学显微镜分辨率仅在微米级limitstheresolutionofanopticalmicroscopetoafewhundrednanometersAugustKöhler(March4,1866–March12,1948),GermanyPhysicistMoritzvonRohr(4April1868–20June1940),GermanyPhysicistJuliusPlücker(16July1801–22May1868)GermanmathematicianandphysicistFerdinandBraun(4April1868–20June1940),GermanyPhysicist185818971891192619281931JuliusPlücker磁场可使阴极射线弯曲Thedeflectionof"cathoderays"(electrons)waspossiblebytheuseofmagneticfieldsRiecke使用磁场能够使阴极射线聚焦Thecathoderayscouldbefocusedbymagneticfields,allowingforsimplelensdesignsAugustKöhlerandMoritzRohr研制出能够将极限辨别率提升约一倍的紫外光显微镜Developmentsintoultraviolet(UV)microscopesallowedforanincreaseinresolvingpowerofaboutafactoroftwoFerdinandBraun阴极射线示波器Built

primitivecathoderayoscilloscopes(CROs)intendedasameasurementdeviceAdolfMatthias&MaxKnoll考虑了透镜设计和示波器的列排列，研制能够用于产生低放大倍数（接近1:1）的电子光学原件AttemptedtoobtaintheparametersthatcouldbeoptimizedtoallowforconstructionofbetterCROs,aswellasthedevelopmentofelectronopticalcomponentswhichcouldbeusedtogeneratelowmagnification(nearly1:1)imagesHansBusch制镜者方程在合适的条件下能够用于电子射线Thelensmaker'sequationcouldbeapplicabletoelectronsunderappropriateassumptionsMaxKnollGroup成功的产生了在阳极光圈上放置的网格的电子放大图像——第一台电子显微镜SuccessfullygeneratedmagnifiedimagesofmeshgridsplacedovertheanodeapertureArguablythefirstelectronmicroscope1LouisdeBroglie

(15

August1892–19

March1987),FranchPhysicistAwardedNobelPrizeinPhysics(1929)LouisdeBroglie,1927电子作为物质粒子的波动特征Thewavenatureofelectronshadnotbeenfullyrealizeduntilthepublicationofthe

DeBrogliehypothesis

in1927电子波的波长比光波波长小了若干数量级，理论上允许人们观察原子尺度的物质TheDeBrogliewavelengthofelectronswasmanyordersofmagnitudesmallerthanthatforlight,theoreticallyallowingforimagingatatomicscales历史History辨别率的提升ImprovingResolution透射电子显微镜4MaxKnoll&ErnstRuska1932建造一种新的电子显微镜以直接观察插入显微镜的样品Constructedanewelectronmicroscopefordirectimagingofspecimens

insertedintothemicroscope1933通过对棉纤维成像正式地证明了TEM的高分辨率ByusingimagesofcottonfibersdemonstratedthehighresolutionofTEM第一台商用TEMThefirstcommercialelectronmicroscope

wasinstalledinthePhysicsdepartmentofIGFarben-Werke1936改进TEM的成像效果，尤其是对生物样品的成像TheimprovementofTEMimagingproperties,particularlywithregardtobiologicalspecimensThefirstpracticalTEM,originallyinstalledatIGFarben-WerkeandnowondisplayattheDeutschesMuseuminMunich,Germany1历史History进一步研究FurtherResearch透射电子显微镜51AfterWorldWarⅡErnstRuskaatSIMENS生产了第一台能够放大十万倍的显微镜Producedthefirstmicroscopewith100kmagnification1942第一届电子显微镜国际会议(Delft)Thefirstinternationalconferenceinelectronmicroscopy1950InParis1954

InLondon1970AlbertCrewe(ChicagoUniversity,USA)发明了场发射枪，添加了高质量的物镜，发明了现代的扫描透射电子显微镜Developedthefieldemissiongun

andaddedahighqualityobjectivelenstocreatethemodernSTEM(ScanningTransmissionElectronMicroscopy)ASTEMequippedwitha3rd-ordersphericalaberrationcorrector目录Contents透射电子显微镜61历史History2原理Background3构造Components4制备Preparation5应用Application原理Background电子Electron透射电子显微镜72

光学显微镜所能达成的最大辨别率受到如下条件的限制Themaximumresolutionthatonecanobtainwithalightmicroscopehasbeenlimitedby照射在样品上的光子波长λthewavelengthofthephotonsthatarebeingusedtoprobethesampleλ光学系统的数值孔径，NAthenumericalapertureofthesystemNA相对论修正Anadditionalcorrectiontoaccountforrelativisticeffects透射出的电子束包具有电子强度、相位、以及周期性的信息，这些信息将被用于成像Thetransmittedbeamcontainsinformationaboutelectrondensity,phaseandperiodicity.Thisbeamisusedtoformanimage原理Background电子源SourceFormation透射电子显微镜82

材料MaterialsTungstenorLaB6形制ShapesHairpin-stylefilamentSmallspike-shapedfilament

HairpinstyletungstenfilamentSinglecrystalLaB6filament高压电源highvoltagesource(typically~100–300kV)热电子发射

或场电子发射thermionicorfieldelectronemission两种物理现象TwoPhysicalEffects运动的电子在磁场中将会根据右手定则受到洛伦兹力的作用Theinteractionofelectronswithamagneticfieldwillcauseelectronstomoveaccordingtothelefthandrule使用磁场能够形成不同聚焦能力的磁透镜Theuseofmagneticfieldsallowsfortheformationofamagneticlensofvariablefocusingpower原理Background电子光学设备与成像设备Optical&Display透射电子显微镜92

透镜Lens

电子束聚焦Beamconvergence三级透镜Threestagesoflensing

聚焦透镜Thecondenserlenses

物镜Theobjectivelenses

投影透镜Theprojectorlenses荧光屏FluorescentScreenZnS(10–100

μm)FilmsCCDLayoutofopticalcomponentsinabasicTEM目录Contents透射电子显微镜101历史History2原理Background3构造Components4制备Preparation5应用Application构造Components真空系统VacuumSystem(No.11)透射电子显微镜113

作用Effects在阴极和地之间加以很高的电压，而不击穿空气产生电弧Theallowanceforthevoltagedifferencebetweenthecathodeandthegroundwithoutgeneratinganarc将电子和空气原子的撞击频率减小到能够忽视的量级Toreducethecollisionfrequencyofelectronswithgasatomstonegligiblelevels构成Components旋片泵或隔膜泵RotaryVanePumporDiaphragmPumps低真空Settingasufficientlylowpressure涡轮分子泵或扩散泵Turbo-molecularorDiffusionpump高真空Establishinghighvacuumlevel门阀或差动泵GatevalvesorDifferentialpumpingaperture隔离电子枪与主腔室Isolatedthegunfromthemainchamber离子泵或吸气材料IonpumporGettermaterialTheelectronsourceoftheTEMisatthetop,wherethelensingsystem(4,7and8)focusesthebeamonthespecimenandthenprojectsitontotheviewingscreen(10).Thebeamcontrolisontheright(13and14)构造Components样品台SpecimenStage(No.6)透射电子显微镜123

尺寸Size直径3.05mm的环形，其厚度和网格大小不不小于100微米StandardTEMgridsizesarea3.05mmdiameterring,withathicknessandmeshsizerangingfromafewto100μm内部的网格区域直径约2.5mmThesampleisplacedontotheinnermeshedareahavingdiameterofapproximately2.5mm材料Materials:Cu,Mo,Au,Pt设计Design侧入式theSide-entryversion顶入式theTopentryversionTheelectronsourceoftheTEMisatthetop,wherethelensingsystem(4,7and8)focusesthebeamonthespecimenandthenprojectsitontotheviewingscreen(10).Thebeamcontrolisontheright(13and14)构造Components电子枪ElectronGun(No.2)透射电子显微镜133

构成Consistance灯丝、偏置电路、韦乃特阴极、阳极theFilament,aBiasingcircuit,aWehneltcap,andanExtractionanode材料Materials:Cu,Mo,Au,Pt设计Design侧入式theSide-entryversion顶入式theTopentryversionTheelectronsourceoftheTEMisatthetop,wherethelensingsystem(4,7and8)focusesthebeamonthespecimenandthenprojectsitontotheviewingscreen(10).Thebeamcontrolisontheright(13and14)构造Components电子透镜ElectronLens(No.4)透射电子显微镜143

构成Consistance外壳、磁线圈、磁极、极靴、外部控制电路theyoke,themagneticcoil,thepoles,thepolepiece,andtheexternalcontrolcircuitryTheelectronsourceoftheTEMisatthetop,wherethelensingsystem(4,7and8)focusesthebeamonthespecimenandthenprojectsitontotheviewingscreen(10).Thebeamcontrolisontheright(13and14)目录Contents透射电子显微镜151历史History2原理Background3构造Components4制备Preparation5应用Application制备Preparation透射电子显微镜164

要求Requirement薄片在纳米尺度TEMspecimensarerequiredtobeatmosthundredsofnanometersthick措施Methods切片加工法TissueSectioning染色加工法SampleStaining机械加工法MechanicalMilling化学腐蚀法ChemicalEtching离子刻蚀法IonEtching复制法ReplicationChemicalEtchingReplicationIonEtchingMechanicalMillingSampleStaningTissueSectioning工具Tools玻璃或金刚石GlassorDiamonds优势Advantage取得薄而最低程度变形的样本toobtainthin,minimallydeformedsamples局限Limitation对软样品伤害极大theheavydamageinducedinthelesssoftsamplesAdiamondknifebladeusedforcuttingultrathinsections(typically70to350nm)fortransmissionelectronmicroscopy工具Tools重金属HeavyMental(Os,Pb,Au,U)优势Advantage经过着色提升吸收光线来增强观察细节Enhancethedetailsinlightmicroscopesamplesstains