We had just bought a FEI F20 TEM with a EDS detector of EDAX company, but we met a thorny problems. EDS detector detected a Si peak, sometimes it's strong and sometimes it's disappeared. The EDAX company didn't give the reasonable solution. We just want to know whether someone met the same situation before? If the TEM column is contaminated, the Si peak should be there with the same intensity, but is sometimes disappeared, so I think that column shouldn't be contaminated.
The internal components of your EDS system contain some silicon. One of the most common artifacts is a signal being detected from X-rays striking the detector. Maybe a sample occasionally diffracts a large amount of X-rays towards the detector, resulting n a large artifact. If you have a sample that is giving this signal try and generate an elemental map. If the Si is everywhere, then perhaps it is a detector artifact. If the Si signal is localized to a specific area, is the area oriented towards the detect? An alternative may be that the sample is contaminated. Silicon is everywhere, it can be very difficult to get rid of silicon. It might be in whatever you're using to mount a sample to the holder. It might be in the preparation of an analyte, as in someone accidentally got silicon grease on a tube holding the sample.
Dear prof. Robert. Thank you very much. The Si is everywhere when we use the same sample,even when we use the pure carbon grids. As your analysis, we believe that the most likely is the problem from the dector. Thank you again.
Best regards
It is a well known EDS artifact. Look here
http://www.web.pdx.edu/~jiaoj/phy451/Lect6.pdf
and make search for " Internal fluorescence Peak of Silicon".
I agreed with Prof Robert comments but i have one question during acquisition did you used the Stray aperture to avoid the unwanted peaks (artifact). If this is not the case, then might be your detector have some problem.
In many cases Silicon is found due to contamination of the TEM-Grid during preparation. Solvents are contaminated by silicon grease, nanoparticles synthesized by hydrothermal synthesis in glassware often contains silicic acid, sometimes the carbonfoil on the TEM-Grids itself was contaminated due to preparation in the factory!
Another source for silicon is vakuum grease which is often applied on the O-Ring of the TEM Holder. If there is too much grease on the O-Ring, the loadlock gets contaminated and the Tip of the TEM Holder itself can get a good amount of grease. That's bad, because the cleaning is laborious and tedious. Try cleaning your holder with pure(!) solvents like hexane and check with a dummy specimen like an electrolytical thinned metal foil for silicon. If it's still there, then it is a detector artifact. If it is gone, then you have to investigate further.
Good luck!
Grease on the O-ring of the sample holder?! I've never encountered it and in fact was EXPLICITLY told never to touch anything except for the handle during training. If we made a mistake and touched anything else, the sample holder went immediately to the plasma cleaner. I would not recommend using any kind of grease on your TEM.
That's why i said "often" and not "always" ;) Sometimes the only way to fix a leak at the O-Ring is a thin layer of grease. I know, it is just a quick and dirty fix and in the long run your microscope will get dirtier and result in contamination of specimen or detectors.
I second that touching the holder with your bare hands is definitly a No-No. But the area between O-Ring and the Handle is not critical as it will never enter the microscope vacuum.
I am very sorry for the late reply. Please understand that all of us are in holiday. Thank you for everyone. Considering the complexity of this problem, we decided to change the detector. Thank you again.
Best regards.
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