in-situ SEM-observation

CC cc37 at
Fri Mar 18 13:10:47 EST 1994

In article <2mcdpu$1j4 at>, "Stefan Vetter" 
<Stefan.Vetter 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.
                                                -- CC

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