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1、IntroductiontotheNanoworldScanningElectronMicroscope(SEM)1986PhysicsNobelPrizeErnstRuska(b.1906,d.1988)“Forhisfundamentalworkinelectronoptics,andforthedesignoffirstelectronmicroscope”1897年布勞恩設(shè)計(jì)并制成了最初的示波管1926年布什（H.Busch）發(fā)表了有關(guān)磁焦距的論文SeeingThroughLensesRefr
2、actionLightRay人眼分辨的最小距離0.2mmHowanOpticalMicroscopeworksHowanOpticalMicroscopeworksWhySEMwasdeveloped?LimitationsofOpticalMicroscope(1)Resolution:opticalmicroscopecan’tresolveobjectsmallerthanl/2(2)Depthoffield:opticalmicroscopehaspoordepthoffocus(view).
3、1870s,amannamedErnstAbbeResolvingPowerofSEMThelimitonwhatsizecanberesolvedissetbythewavelength.Thewavelengthofthevisiblelightusedinopticalmicroscopesisbetween400and700nanometers(nm).Theresolvingpowersofhigh-qualitylightmicroscopesarelimitedbythewaveleng
4、thofimaginglighttoabout200nanometers(0.2microns).Scanningelectronmicroscopyuseselectronswithenergiesofafewthousandelectronvolts(eV).ThedeBrogliewavelengthisgivenbyh/momentumwherehisPlanck'sconstant.For3600electron-voltelectrons,thewavelengthis0.02nanome
5、ters.Theresolvingpowersofordinaryelectronmicroscopesis1nanometer(abovethelimitbecauseconstructiondetailsdetermineresolvingpower),avaluewhichcanbepushedto0.1nanometer.DeBroglieWavelengthForelectronwith3600eV,whatisitsdeBrogliewavelength?Assumenon-relativ
6、istic,Energyofelectron=3600x1.6x10-19J=5.76x10–16JThisenergyisintheformofkineticenergyduetoitsmotion.Thisenergyisgivenbymv2/2wherem=massofelectron=9.1x10-31kg,v=velocityofelectron.Wehavemv2/2=5.76x10–16J,?v=3.55x107m/sMomentumofelectronp=mv=3.24x10–23kg
7、m/sHencedeBroglieWavelength=h/p=2x10-11m=0.02nmWhathappenwhenabeamofelectronshitasample?Incidente-BeamBackscatterede-Secondarye-CathodoluminescenceX-rayAugere-SampleElectronRangeThickSampleSecondaryElectrons(SE)IncidentElectronSecondaryElectron入射電子與樣品相互
8、作用后，使樣品原子較外層電子（價(jià)帶或?qū)щ娮樱╇婋x產(chǎn)生的電子，稱二次電子。二次電子能量比較低，習(xí)慣上把能量小于50eV電子統(tǒng)稱為二次電子。二次電子能量低，僅在樣品表面5nm－10nm的深度內(nèi)才能逸出表面，這是二次電子分辨率高的重要原因之一。SecondaryElectrons(SE)Yieldtopographicalinformation.ProductionofSEisverytopographyrelated.Duetotheirlowenergy
