Removal of carbon coating

[Probeman]

This was posted to the microscopy list server recently.  I thought it worth reposting here:

Carbon coating is fairly easy to remove with Oxygen or Oxigen/Helium plasma. Dedicated plasma cleaner would work the best, but you can even try Evactron or IBSS in-situ cleaners. Plasma cleaner is preferred over plasma etcher, as it typically works with much lower RF power and therefore provides "gentler" cleaning.

For completely chemical removal of carbon coating get a UV cleaner (or find a lab which has it) - the removal would be terribly slow (hours or even couple of days for 50nm  C removal), but absolutely no physical damage to the surface.

Easily-removable coating for preventing FIB charging would be to spray-on of one of conductive polymer, either with regular atomizer or better yet with ultrasonic nozzle. Plenty of formulations, I've worked with aquaSAVE (removable by water) and E-Shield (removable by alcohol) with great success (although never tried them on the rock samples).

Valery Ray

[crystalgrower]

I would like to observe that the  phrase "would be" occurs  with every suggestion.

In my experience, including grossly overloaded mounts that were returned to Astimex Scientific for repolishing, there were two safe and effective procedures.  If there was an error on the mount's surface, then the preference was to use sticky tape followed by a quick retouch with 0.2u Al2O3 by hand.  We used the common translucent variety of office tape.  The tape was applied with firm finger pressure and then immediately peeled off. 

If the mount had been grossly overloaded with C, then it was repolished mechanically with 0.2u Al2O3.  Reworking a mount also went back to mechanical polishing.  Any lab that prepares their own mounts has all the equipment and procedures required for removing C.  Although I am guessing, removing Au would similarly have to be done by repeating the final polishing step with 0.2u Al2O3. 

On many occasions a vendor of the plasma systems tried to sell the idea of removing C coatings.  Our gut response was to ask what would happen to the epoxy. No answer and so the experiment was never done.  This vendor did make one trial of providing a 1-nm Os coating.  That coating was not durable in shipping.  It was also visible as a higher-Z background in the SEM, although it could not be detected by XRF.  The SEM is also how I would judge the removal of Au.