Secondary Electron Detectors

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1、SecondaryElectronDetectorAnaZehtabiOskuieIntroductionSecondaryelectronsecondaryelectrondetectorTheelectronbeaminteractionwithnearsurfacespecimenatomswillmakeasignalwhichresultsintheSEMimage.SEMbasics:IntroductionSecondaryelectronsecondaryelectrondetectorIntroductionSecondaryelectronsecond

2、aryelectrondetectorSecondaryelectrons:SecondaryelectronsaregeneratedfromthecollisionbetweentheincomingelectronsandthelooselybondedouterelectronsThescatteredsecondaryelectronsarecategorizedintothreedifferenttypes.IntroductionSecondaryelectronsecondaryelectrondetectorElectronswithenergiesE<

3、50eV:Secondaryelectrons(SE);(2)Electronswithenergies50eV

4、ashighresolutionwhichisonlylimitedbytheelectronbeamdiameter.AsSE1isgeneratedbynearsurfaceatomssothiskindofsecondaryelectronisindependentofV.accIntroductionSecondaryelectronsecondaryelectrondetectorSE2:Thesecondaryelectronsthataregeneratedbythebackscatteredelectronshavereturnedtothesurface

5、afterseveralinelasticscatteringeventsSE2comefromasurfaceareawhichisbiggerthanthespotoftheincomingelectrons,alsobiggerthansurfaceareaofSE1.ThereforeresolutionislessthanresolutionofSE1exclusively.IntroductionSecondaryelectronsecondaryelectrondetectorSE3:ThegeneratorofthiskindistheSE2thatent

6、ersthelenssurfaceandgetscattered.Thus,itwillresultinadecreaseofresolution.IntroductionSecondaryelectronsecondaryelectrondetectorFactorsthataffectSecondaryElectronemission:1-Atomicnumber(Z)MoreSE2arecreatedwithincreasingZIntroductionSecondaryelectronsecondaryelectrondetector2-Beamenergyand

7、beamcurrentElectronyieldgoesthroughamaximumatlowacc.voltage,thendecreaseswithincreasingacc.voltageIntroductionSecondaryelectronsecondaryelectrondetector3-Themostimportantfactoristhelocalcurvatureofthesurface.Ifwehaveaedgemoresecondaryelectroncanbeemittedfromspecific