sem microscope by: doug, holly & oleg. scanning electron microscope vs. optical microscope...
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SEM SEM microscopemicroscope
By:By:
Doug, Holly & OlegDoug, Holly & Oleg
Scanning Electron MicroscopeScanning Electron Microscopevs.vs.
Optical MicroscopeOptical Microscope AdvantagesAdvantages
Continuously variable Continuously variable magnificationmagnification
High resolutionHigh resolution
Depth of focusDepth of focus
Elemental analysis Elemental analysis attachmentsattachments
DisadvantagesDisadvantages
CostCost
More knobsMore knobs
VacuumVacuum
Sample limitationsSample limitations
Scanning Electron MicroscopeScanning Electron Microscope(simplified drawing)(simplified drawing)
sample
tungsten filament (electron source)
electrostatic lens (F = qE)
accelerating voltage anode
electromagnetic lenses (F = q v x B)(condenser lenses)
electromagnetic lens (objective lens)& deflector coils (raster scan)
e-
detector (scintillator & PMT)SE
Signal GenerationSignal Generation
In (Probe)In (Probe)
Focused mono-energetic electron beamFocused mono-energetic electron beam
Out (Signal)Out (Signal)
ImagingImaging• Backscattered electronsBackscattered electrons• Secondary electronsSecondary electrons
AnalysisAnalysis• X-raysX-rays
Characteristic x-raysCharacteristic x-rays
Bremsstrahlung x-rays (background “noise”)Bremsstrahlung x-rays (background “noise”)• Auger electronsAuger electrons
Topographic contrastTopographic contrast
surface
same penetration depth
shorter exit distance,higher signal
longer exit distance,lower signal
SEM general infoSEM general info
SEM General infoSEM General info•Mount the sample on the holder•“Paint” the conductive path
SEM General infoSEM General infoLoad the sample into the SEMLoad the sample into the SEM
SEM general infoSEM general info
•Vacuum pump 4 minutes
•Turn on filament current & accelerating voltage
•Fiddle with the knobs
Sample PrepSample PrepQuenched from 1700 Quenched from 1700 degFdegF
Anneal to 900 degFAnneal to 900 degF
Furnace cooled from Furnace cooled from 1700 degF1700 degF
Low C steelLow C steel
High C steelHigh C steel
Unknown C steelUnknown C steel
High C (optical 600x)High C (optical 600x)
High C (SEM 400x)High C (SEM 400x)
High C (SEM 3000x)High C (SEM 3000x)
Low C (600x optical)Low C (600x optical)
Low C (SEM 400x)Low C (SEM 400x)
Low C (SEM 3000x)Low C (SEM 3000x)
Unknown C (SEM 400x)Unknown C (SEM 400x)
Unknown (optical 600x)Unknown (optical 600x)
Unknown (SEM 3000x)Unknown (SEM 3000x)
Low C vs High C (SEM 200x)Low C vs High C (SEM 200x)
Low Carbon
Plastic
High Carbon
Low CLow C(3000x vs 10000x)(3000x vs 10000x)