sem microscope by: doug, holly & oleg. scanning electron microscope vs. optical microscope...

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)