Hi, I have an oxide layer formed on carbon steel at room temperature. When I performed SEM on a cross-section moulded sample, I've started noticing some black areas (in red rectangular) within the oxide film.
Please note that the sample is moulded first, then is sectioned.
What could be these black areas? Resin?
Thank you
It definitely looks like some organic contamination. Was cooling liquid applied when sectioning? Was specimen polished after sectioning?
EDIT: is it a resin that looks white (huge charging?) Was conductive coating applied?
Thanks, Vladimir Dusevich
No, there was no cooling (it was a small sample). Should I apply cooling liquid?
Yes, it was automatically ground up to 1200, and then it was automatically polished.
I've applied a carbon coating.
look like voids that tend to form in some phase separation region (from the graph they seems to be aligned in rows nearly parallel to the surface)
Mahmoud Saeed , thanks for clarification. Now I see my mistake (about charging); left side is steel, not resin. I prefer cutting with as little damage as possible, so cooling a specimen is not a bad idea. It looks like there is a big crack separating metal and oxide, and the leftmost red rectangular lies in it. To identify what other dark places are I would recommend to take two pictures from the same place - not just in backscattered electrons (as you have), but in secondary electrons as well, for a better observation of topography.
I also think it can be related to organic contamination, however, if you have the possibility, maybe you can try EDS to verify it. Most of the modern SEMs have the EDS spectrometer and at lease qualitatively you can find what the black area is. Best regards.
It seems there is some contamination on your grid. How did you prepare your sample?
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