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SEM microscope. By: Doug, Holly & Oleg. Advantages Continuously variable magnification High resolution Depth of focus Elemental analysis attachments. Disadvantages Cost More knobs Vacuum Sample limitations. Scanning Electron Microscope vs. Optical Microscope.

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sem microscope

SEM microscope

By:

Doug, Holly & Oleg

scanning electron microscope vs optical microscope
Advantages

Continuously variable magnification

High resolution

Depth of focus

Elemental analysis attachments

Disadvantages

Cost

More knobs

Vacuum

Sample limitations

Scanning Electron Microscopevs.Optical Microscope
scanning electron microscope simplified drawing

tungsten filament (electron source)

electrostatic lens (F = qE)

e-

accelerating voltage anode

electromagnetic lenses (F = q v x B)

(condenser lenses)

electromagnetic lens (objective lens)

& deflector coils (raster scan)

detector (scintillator & PMT)

SE

sample

Scanning Electron Microscope(simplified drawing)
signal generation
Signal Generation

In (Probe)

  • Focused mono-energetic electron beam

Out (Signal)

  • Imaging
    • Backscattered electrons
    • Secondary electrons
  • Analysis
    • X-rays

Characteristic x-rays

Bremsstrahlung x-rays (background “noise”)

    • Auger electrons
topographic contrast
Topographic contrast

surface

same penetration depth

shorter exit distance,

higher signal

longer exit distance,

lower signal

sem general info1
SEM General info
  • Mount the sample on the holder
  • “Paint” the conductive path
sem general info2
SEM General info
  • Load the sample into the SEM
sem general info3
SEM general info
  • Vacuum pump 4 minutes
  • Turn on filament current & accelerating voltage
  • Fiddle with the knobs
sample prep
Quenched from 1700 degF

Anneal to 900 degF

Furnace cooled from 1700 degF

Low C steel

High C steel

Unknown C steel

Sample Prep
high c optical 600x
High C (optical 600x)

High C (SEM 400x)

High C (SEM 3000x)

low c 600x optical
Low C (600x optical)

Low C (SEM 400x)

Low C (SEM 3000x)

slide13

Unknown (optical 600x)

Unknown C (SEM 400x)

Unknown (SEM 3000x)

low c vs high c sem 200x
Low C vs High C (SEM 200x)

Low Carbon

Plastic

High Carbon