What is SEM (Scanning Electron Microscopy)?

slide 1

First the scientist has to pick a sample to look at under the SEM. Samples must be small enough to fit into the specimen chamber and need to be dry. If moist biological samples are used, they need to be chemically fixed to preserve their struct

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Samples are mounted on a metal holder, called a “specimen stub.” This stub holds the specimen up for imaging and stabilizes the specimen.

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The specimen is usually attached using double sided carbon tape. This tape sticks the specimen to the stub while not affecting the electron imaging of the specimen.

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The sample is then attached to the stub with carbon tape. Many times this is done in the field and then the mounted specimen is transported back to the SEM lab.

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This is a specimen of moonmilk from a lava tube, already attached to the stub.

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Carbon cement is then attached to the specimen and stub in the lab. This cement is thicker and stronger than super glue and electronically grounds the specimen so that an electrostatic charge does not accumulate on the surface.

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The specimen, on the stub, is then put into a sputter coater. This coats the specimen with gold/palladium, which helps with the imaging. To create an image, the specimen needs to bounce electrons out after being hit by the stream of electrons t

Slide 8

Mike Spilde, our SEM expert, powers up the sputter coater to coat our specimen.

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The gold/palladium is coated onto the sample using plasma streaming. A highly energetic plasma is generated in the argon gas in the chamber. The plasma ions collide with the gold and palladium in the target (the very bright thing in the middle t