cc37 at cornell.edu
Fri Mar 18 13:10:47 EST 1994
In article <2mcdpu$1j4 at mserv1.dl.ac.uk>, "Stefan Vetter"
<Stefan.Vetter at vu-wien.ac.at> wrote:
> Germany). As is generally know, observing organic matter in the SEM requires
> coating the objekt with a conductive film, mostly gold. Breaking such material,
> however, automatically exposes uncoated surfaces to the electron beam and leads to
> strong electric charging even at a low acceleration voltage (1-3 KV) making
> observation and documentation impossible.
> Has anybody got an idea how we could solve this problem? We would be very grateful
> for every tip we get!
> Michael Schlag
What you need to do is somehow make all of your material conductive,
not just the surface features. I can think of two options for this:
1) View the material in a frozen hydrated state, so that the water
will conduct as you are breaking the material. A problem I can see with
this is that frozen material may not behave the same as unfrozen material.
2) Treat your material in some way to make it conductive. A few
possibilities are a short fixation followed by postfixation treatment with
osmium tetroxide and thiocarbohydrazide (OTO technique) and/or uranyl
acetate. You may need to critical point dry or freeze-dry the specimens
afterwards. We have succesfully viewed uncoated Tetrahymena (lots of
cilia) treated this way at 2.5 kV at upwards of 50kX in our Hitachi 4500.
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