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Notre Dame extended Research Community

Scanning Electron Microscope

Michael CrockerValerie GossRebecca Quardokus

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Scale

SEM Feature Sizes Down to 1 nm for best scopes Maximum around 500,000x magnification

Viewing Nanomagnets Feature Size: 5-10nm

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Looking Smaller

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Basic SEM Idea

e-e-

e-

e-

e-

e-

e-

e-

e-

e-e-

Some are absorbed

Some are “reflected”

Some is absorbed

Some light is “reflected”

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The Electron Beam Column

http://bioweb.usu.edu/emlab/TEM-SEM%20Teaching/How%20SEM%20works.html

Beam created from heated filament

Beam travels through a vacuum

Electro-magnetic fields act as lenses

Scattered and “secondary” electrons are detected

Electron beam hits the sample in a precise

location

Beam scans back and forth

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The “Splash”

http://www4.nau.edu/microanalysis/Microprobe-SEM/Signals.html

Primary electrons come from the beam

Some electrons scatter back (BSE), and they

move very fast

Other secondary electrons (SE) are

dislodged and move more slowly

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Water Hose and Splash

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Splash Analog

How it helps E-Beam and Water Stream Scattering and Splash The beam moves back and forth (scan)

How it doesn’t help Electron beam is created by magnetic field The beam gets wider and thinner The electrons penetrate the surface Electrons can be selectively detected

Be clear when using analogs!

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Other Analogs

Solar System Mobile Sun and Planets on a Football Field Onion as the shells of a Star Solar System as an Atom Etc.