x-射线光电子能谱.ppt

《x-射线光电子能谱.ppt》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、NanoscopicCharacterizationMethods:X-rayPhotoelectronSpectroscopyXPS:SystemCharacteristicsIntroductionBackgroundTheoryInstrumentationSystemPerformanceSensitivityResolutionLimitationsCurrentApplicationsFutureImprovementsXPS:IntroductionCharacterizationofsurfacecomposition/molecularfunctionality

2、X-radiationofsurfacesejectsphotoelectronsElectronsanalyzedbydetector,energydeterminedOrbitalspossesscharacteristiceVassignments;correlatedtodetermineelementalcomposition???XPS:TheoryBasedonEinstein’sRelationship:E=photonenergy,h=Plancksconstant(6.62x10-34Js),c=speedoflight,andv=frequency(Hz)of

3、theradiation.XPS:TheoryInitialConditionsA+hv=A++e-ConservationofEnergyE(A)+hv=E(A+)+E(e-)RearrangeEq.,obtainKEKE=hv-E(A+)+E(A)FinalEquationKE=hv–BE,*WhereBE=energydifferencebetweenionizedandgroundstateKE=hv–BE-Φ,whenworkfunctionincludedXPS:TheoryOtherConditionstoConsider:DoubletStatesSecondary

4、ReactionsDoubletStates(1s)2(2s)2(2p)6(3s)2(3p)6(3d)10....InstrumentalComponentsX-RaySource:TwinAnodeMg/AlSourceMonochromaticSourceAnalyzer:ConcentricHemisphericalAnalyzer(CHA)Detector:ChanneltronElectronMultiplierVacuumSystemInstrumentalComponentsX-RaySource:TwinAnodeMg/AlSourceUseselectricfil

5、amenttoproduceelectronsAcceleratetowardsanodeandgeneratex-raysSwitchbetweenanodestochoosephotonenergySimple,inexpensiveHighfluxofx-rayphotonsPoorresolutionMonochromaticSourceUsesdiffractionthroughquartzcrystaltoselectx-rayphotonsofcertainwavelengthsImprovesresolutionInstrumentalComponentsAnaly

6、zer:ConcentricHemisphericalAnalyzer(CHA):2concentrichemispheresofdifferentradiiVoltagebiasapplied–varytoscanenergyspectrumFilterelectronsbyselectingelectronsofcertainkineticenergyInstrumentalComponentsDetector:ChanneltronelectronmultiplierMeasuresnumberofelectronsofspecificbindingenergiesLeads

7、ilicateglassConductiveandproducessecondaryelectronemissionOutputplacedathighVaccelerateelectronsSensitivityPhotoelectronInelasticMeanFreePath(IMFP)X-rayradiationse-e-X-raypenetrationdepthIMFPX-rayPenetrationDepthProbabilityofEscapingPh