SEM原理及应用课件.ppt

《SEM原理及应用课件.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、IntroductiontotheNanoworldScanningElectronMicroscope(SEM)1986PhysicsNobelPrizeErnstRuska(b.1906,d.1988)“Forhisfundamentalworkinelectronoptics,andforthedesignoffirstelectronmicroscope”1897年布劳恩设计并制成了最初的示波管1926年布什（H.Busch）发表了有关磁焦距的论文SeeingThroughLensesRefr

2、actionLightRay人眼分辨的最小距离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入射电子与样品相互

8、作用后，使样品原子较外层电子（价带或导带电子）电离产生的电子，称二次电子。二次电子能量比较低，习惯上把能量小于50eV电子统称为二次电子。二次电子能量低，仅在样品表面5nm－10nm的深度内才能逸出表面，这是二次电子分辨率高的重要原因之一。SecondaryElectrons(SE)Yieldtopographicalinformation.ProductionofSEisverytopographyrelated.Duetotheirlowenergy