材料科学中电子显微镜的各种技术介绍

PartIIIAnalyticalElectronMicroscopyinMaterialsScience1.Introduction2.ImagemodeinAEM3.MicroanalysisinAEM3.1X-rayEnergyDispersiveSpectroscopy(EDS)3.2ElectronEnergyLossSpectroscopy(EELS)3.3Microdiffraction3.4Convergentbeamdiffraction

1、Introduction1.Signalsgeneratedintheinteractionbetweentheincidenthighenergyelectronbeamandthethincrystallinespecimen2.Howtoformaprobe3.RelationshipbetweenTEM,SEMandAEM3.1TEMImagemodeDiffractionmode3.2SEMImagemode:SE,BSE,X-RayMappingMicroanalysis:WDS,EDS3.3AEMImagingmode:TEM,STEM,SEM,Mapping(X-Ray+EELS)Diffractionmode:ScanningprobeStationarydiffractionpatternMicroanalysis:EDS,EELS,micro-diffraction,convergentbeamdiffraction

Howtoformaprobe?DetectorsneededforanAEM3.RelationshipbetweenTEM,SEMandAEM3.1TEMImagemodeDiffractionmode3.2SEMImagemode:SE,BSE,X-RayMappingMicroanalysis:WDS,EDS3.3AEMImagingmode:TEM,STEM,SEM,Mapping(X-Ray+EELS)Diffractionmode:ScanningprobeStationarydiffractionpatternMicroanalysis:EDS,EELS,micro-diffraction,convergentbeamdiffraction3.2SEMImagemode:SE,BSE,X-RayMappingMicroanalysis:WDS,EDS3.3AEMImagingmode:TEM,STEM,SEM,Mapping(X-Ray+EELS)Diffractionmode:ScanningprobeStationarydiffractionpatternMicroanalysis:EDS,EELS,Micro-diffraction,Convergentbeamdiffraction2、ImaginginAEM2.1.TEM2.2.STEM-Scanningtransmissionelectronmicroscopy2.3.STEM/SEMimaging2.4.Signalmixing-Hybridimaging2.5.X-RayandEELSmapping3、MicroanalysisinAEM3.1X-Rayquantitativemicroanalysis3.1.1X-RaysignalgenerationinTEMthinfoilspecimens3.2.2Identificationandeliminationofspurioussignals3.2.3OptimizationoftheAEMformicroanalysis3.2.4X-Raymicroanalysis3.2.5Microanalysislimit3.2EELS-ElectronEnergyLossSpectroscopy3.2.1energylossprocessinthinfoilTEMspecimens3.2.2Wheretofindtheenergylosselectrons?3.2.3Electronenergylossspectrometer3.2.4ComparisonofthesignalgeneratingprocessforEDSandEELS3.2.5Theenergylossspectrum3.2.6EELSMicroanalysisandthelimitofanalysis3.2.7Conclusionremarks3.3ComparisonbetweenEDSandEELSX-RaysignalgenerationinTEMthinfoilspecimensFluorescenceyield(w):w=0forZ～5(Boronkshellionization)Z～27(CobaltLshell)Z～57(lathanlumMshell)3.2.3OptimizationoftheAEMformicroanalysis3.2.4X-RaymicroanalysisCliffandLorimer:CA+CB=100%LimitformicroanalysisbyEDS1.Absoluteaccuracy2Minimumdetectablemass:MDM10-20g3Minimummassfraction:MMF0.1wt%4Spatialresolution:10～～20nm5LowZlimit6Practicallimitations:(1)contamination(2)Embeddedparticales3.2EELS-ElectronEnergyLossSpectroscopy3.2.1energylossprocessinthinfoilTEMspecimens3.2.2Wheretofindtheenergylosselectrons?3.2.3Electronenergylossspectrometer3.2.4ComparisonofthesignalgeneratingprocessforEDSandEELS3.2.5Theenergylossspectrum3.2.6EELSMicroanalysisandthelimitofanalysis3.2.7Conclusionremarks3.2.2Wheretofindtheenergylosselectrons?3.3.3EELSSpectrometer3.2.4ComparisonofthesignalgeneratingandcollectionprocessforEDSandEELS1.SignalgenerationEDS-secondaryeventHighenergyincidentelectronsexcitationofatomscharacteristicX-raysorAugerelectronsEELS-primaryevent2.CollectionefficiencyEDS-verylow!!X-Raygeneration:forcarbon:1inevery400k-shellionizationforNa,1in40Collectionefficiency:WDS:10-3-10-4EDS:～～10-2Goldlayer(20nm):onlyallow67%betransmitted!TheDeadlayerbelowthegoldlayer:37%ofthe67%betransmitted!EELS:veryhigh!!75%oftheenergylosselectronswithacollectionangleof10mrad100%whencollectionangleis30mrad3.2.5Theenergylossspectrum(1)Thezerolosspeak(2)ThelowlossregionofthespectrumDE<50eVplasmonpeaks(3)HighenergyregionofthespectrumDE>=50eVenergylosspeak-ionizationedgespre-edgeandpost-edgestructureMicroanalysisusingionizationpeaks(edges)3.2.5ThelimitationsinEELSanalysis1.DetectionlimitsMDM:In500ÅFefoil,103atomsforLiandAl3x104atomsforO(k-edge)MDF:Cin300Åsteel:3at%(100atoms)Oin600ÅÅsteel:6at%2.Specimenthickness3.SpatialresolutionPhaseidentification4、MicroDiffraction4.1LimitoftheSelectedareaelectrondiffraction(SAD)4.2Microdiffraction4.2.1theRickemethod4.2.2convergentbeammicrodiffraction4.1LimitoftheSelectedareaelectrondiffraction(SAD)5、Convergentbeamdiffraction5.1Terminology5.2HowtogetaCBDP5.3ZOLZ-theZeroOrderLaueZone5.4ThicknessMeasurementbyCBDP5.5HOLZ-HigherOrderLaueZone5.6HOLZLines-HigherOrderLaueZoneLines5.7ZAPS-thezoneAxisPatters5.8Acquiring3-Dsymmetryinformation5.9Phaseidentification5.10summary5.1TerminologyZOLZ-ZeroOrderLaueZoneHOLZ-HigherOrderLaueZoneFOLZ-FirstOrderLaueZoneSOLZ-SecondOrderLaueZoneKikuchiLinesHOLZLinesDynamicalEffectK-MPatternKosselPattern5.2HowtogetaCBDP5.3ZOLZ-theZeroOrderLaueZone5.4ThicknessMeasurementbyCBDP5.5HOLZ-HigherOrderLaueZone5.5.1HigherorderLauezone5.5.2Determinationofinterplanarspacingsparalleltotheelectronbeamdirection5.5.3IndexingoftheHOLZmaximahu+kv+lw=1forFOLZmaximahu+kv+lw=2forSOLZmaximaForfcc:WhenU+V+WoddWhenU+V+WevenForbcc:WhenUVWalloddWhenUVWallevenForHexcrystal:5.6HOLZLines-HigherOrderLaueZoneLines5.6.1HOLZlines5.6.2IndexingofHOLZlines5.6.3ApplicationofHOLZlinesUnitcelldimensionCrystalsymmetryCrystaldefect5.7ZAPS-thezoneAxisPatters5.8Acquiring3-DsymmetryinformationFromKosselpatternFromK-