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VisualizationonthenanoscaleScanningelectronmicroscopy-SEMAtomicforcemicroscopy-AFM
MicroscopyHumaneyeLightmicroscopeScanningelectronmicroscopeTransmissionelectronmicroscopeScanningprobemicroscopeorganismbacteriavirusOrg.moleculeatomsmacromoleculeEukaryote
Wavelengthofvisiblelight(photons):400nm-800nmResolutionlimit:ca200nmMagnification:upto1500xDepthoffield:0.5μmat1000xdeBroglie:ElectronswithwavelengthinverselyproportionaltovoltageElectronmicroscopyvs.opticalmicroscopyWavelength4-5ordersofmagnitudesmallerthanvisiblelight(0,039nm...0,007nm)
AbilityofSEM
HistoryTransmissionelectronmicroscope(TEM)1932firstprototypebyKnollandRuska1936firstcommercialdeviseScanningelectronmicroscope(SEM)1942firstprototype1965firstcommercialdeviseElectronmicroscopy
Electronmicroscopy:SEMvs.TEM
TransmissionElectronMicroscope–TEM(1932)TheTransmissionElectronMicroscope(TEM)
Therayofelectronsisproducedbyapin-shapedcathodeheatedupbycurrentTheaccelerationvoltageis50-50kVThelenssystemsconsistofelectroniccoilsgeneratinganelectromagneticfieldTheraypassesthroughtheobject(100nm),whereitispartiallydeflected.ThedegreeofdeflectiondependsontheelectrondensityoftheobjectThescatteredelectronsformablack-and-whiteimagethatisenlargedbyalens-system(projective).ThedegreeofdarknesscorrespondstotheelectrondensityTransmissionelectronmicroscopyResolution:upto0,3nmMagnification:upto300.000
ScanningElectronMicroscope–SEM(1942)ScanningelectronmicroscopyResolution:upto0,5nmMagnification:50...106-foldLargedepthoffieldThepathoftheelectronbeamdiffersfromTEMConductivespecimens(oftengoldcoating)ThesurfaceoftheobjectisscannedwiththeelectronbeampointbypointwherebysecondaryelectronsaresetfreeTheintensityofsecondaryradiationisdependentontheangleofinclinationoftheobjectssurfaceThese
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