This would be a nearly pointless exercise: with LaB6 filament you can make a small beam but it will have not enough current in it (~pA) to do X-ray mapping. A FEG will give you a sub-nm probe with three orders of magnitude higher current (~1nA) so you can do reasonably fast mapping within some minutes and get maps with good SNR within a few 10 minutes or so, while the same would take you 16 hours on a LaB6 instrument, during which drift will kill the experiment.

I routinely collect decent quality EDS maps on a JEOL 2100 S/TEM with a LaB6 crystal. We have a 60mm^2 SDD for our EDS detector, so we get good counts even running a map for just 10 mins. The point here is that I want to visually illustrate the benefits of a Cs-corrected STEM for EDS mapping as compared to our current instrumentation at VA Tech, which is a non-Cs-corrected S/TEM with a LaB6 source. This is to show the non-microscopists that make funding decisions why a Cs-corrected scope would be a boon for us to have.

Hi Sheri, sure, but what is your resolution? With a FEG I routinely get 1-2nm; everything smaller depends on sample thickness and drift rates. With a LaB6 filament I bet you will not get that kind of resolution in EDX maps., even with a large SDD.

Oh definitely. The LaB6 crystal does not give me very good resolution in STEM or for EDS maps. That's actually why I'm trying to find good comparative images—to show the people who make the funding decisions at my university why we sorely need a FEG TEM!

Dear Dr. Singerling,

I have seen some good comparative images to show the effects of Cs correction on the spatial resolution of TEM images and EDS maps in the book "Transmission Electron Microscopy: A Textbook for Materials Science (2nd Edition)" by David B. Williams and C. Barry Carter. In chapters 1 and 36 you can find the images and detailed analytical comparisons with illustrations.

I hope this may help you.

Kind regards,

Amir Sabet Ghorabaei