Electron microscopy

[P3D Paul S. Boyer <boyer@xxxxxxxxxxxxx>]

Jim Crowell asks:
"Paul,

Could you elaborate on this (the difference between transmission &
scanning
microscopes, I mean).

-Jim C."

Ah, umm .. I think that a few writers have posted messages which
indicate that they know more about TEM than I do.  The TEM which I
have watched being made have been done with acetate peels, and have
about as much relief as a fingerprint.  I suppose that you could get
depth out of that, and apparently other techniques make this
possible.
Still, SEM is what can give you pictures with great depth of field
not possible in light photography.  When I first got to use and SEM,
it immediately struck me that this would make stereo feasible.
Stereo is poor at high magnifications on regular light microscopes
because you have insufficient depth of field.  I have always been
frustrated with regular high-power microscopes because you see only
one plane at a time.
So we made SEMicrographs in stereo back in 1975, and even published a
few in a paper in Micropaleontology.
I also was not aware that it is possible now to make SEMicrographs
without coating the specimens.  I was working with acid-resistant
microfossils, and would coat them with Al.  Then afterwards I would
immerse the specimens in dilute HCl to remove the Al.  Obviously, one
cannot remove Au coatings without destroying everything else!
The SEMicroscopist who worked with me in 1975 is Dee Breger of
Lamont-Doherty Geological Observatory of Columbia University.  She
recently published a book of stereo SEMs which was reviewed in Stereo
World.  I have not yet seen the book.  May someone else could comment
on it!
--Paul S. Boyer  <boyer@xxxxxxxxxxxxx>


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