FEI Tecnai F20 S/TEM: STEM mode operation
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- Опубликовано: 25 авг 2024
- Dr. Nicholas Rudawski of the University of Florida demonstrates operation of the FEI Tecnai F20 S/TEM in scanning (STEM) mode including:
1. Specimen adjustments before entering STEM mode
2. Choosing an appropriate numerical value of spot size
3. Alignment of the instrument in STEM mode
4. Camera length selection for HAADF-STEM imaging
5. Acquiring and adjusting STEM images using TIA
6. Considerations for atomic-resolution STEM imaging
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Ha ha, thanks, glad you liked the video!
As usual very great..
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Thank you!
I,m very surprised to find this useful video in RUclips! Thank you for this tutorial especially for rounchegrams allighments and and Scope adjustment. Next HRSTEM I will do with this video playing parallel )) P.s. You are lucky, because of absence AC magnetic field. But even those, the 1024 image will be better if you use dwell time 15,31 mks (not 32!). Thank you!
Glad you find the video helpful; I think the room passed in terms of magnetic fields, but I'm not sure; the Tecnai doesn't produce STEM images as nice as our Talos, but STEM performance wasn't really the main priority at the time the Tecnai was in production; there is way more emphasis on STEM performance today, both in terms of the microscope and the room as well.
Thank you for the videos! Great stuff!
What size c2 aperture are you using for stem? Using the same scope you are, all apertures are 100 though for brightfield imaging. Need to order some for stem
Thank you
Thank you for your support. So, funny thing about the C2 aperture I am using here: it was actually one of the original C2 apertures, but it was originally too small. So, I used the dual FIB/SEM in the next room and I opened it up a little bit (I think the final diameter was 30 or 50 um; I'm not entirely sure as this was 7 years ago when I did this). With the 2 condenser S/TEMs, you don't have the ability to set the convergence angle as desired, so alpha is effectively fixed by the C2 aperture size. 100 um is definitely going to be too large for performing any kind of HR-STEM, but if you measure alpha using a 100 um C2 aperture, you can then extrapolate to the necessary C2 diameter to give an appropriate value of alpha (at 200 kV with Cs = 1.2 mm, this should be ~10.0 +/- 0.5 mrad). I also have an application note from FEI about measuring alpha; if you want it, please email me and I will send it to you. Tuning your optimal value of alpha for HR-STEM would also be a good future video topic.
Dr. Rudawski, thank you very much for the nice video!
This may be a silly question. When you mentioned "well-aligned" at 28:17, do you mean the zone axis? And how can one tell if it's well aligned based on the CBED pattern? Will the process of adjusting this zone axis based on CBED pattern be the same process as closing the Laue circle in convention mode, but with the binoculars? Thanks!!!
Great tutorials.. I will be happy if you could do more videos on ronchigram. This video has ronchigram concepts. However, the ronchigram shown is not clear. Also can you show us how to get the sample to the zone axis in STEM mode using ronchigram.
Also, bright field and dark field imaging in STEM mode
Please see this video about using the Ronchigram for alignment; I may try to upload again at some point as RUclips appears to have compressed this somewhat and reduced its initial resolution (but at least this is better than what you can see in the original STEM video):
ruclips.net/video/LGfZlWeKLhk/видео.html
The Ronchigram is just the direct or 000 disk of the CBED pattern; you can't use this alone to align to the zone axis, you have to look at the whole CBED pattern. I can probably make a separate short video covering how to do this and another short video covering the differences in STEM modes as this video only covers HAADF-STEM mode; thank you for giving me new video ideas!
Nice 👍
Thanks for your video，it's realy helpful! I just want to be sure that, given the right alignment we can get a atomic level high-res STEM-HAADF even on a conventional TEM without Cs correctors?
You're welcome! Yes, you can get atomic-resolution STEM with a non-corrected instrument as long as it is a FEG instrument.
@@NicholasRudawskiI followed your tutorial and tried on an FEI TALOS F200X TEM, unfortunately, the C2 aperture is too small (150μm) to see a Ronchigram (or I did it wrong). what's the diameter of the C2 aperture on the tem you were operating? I also watched your ronchigram video, to be honest, it's quite different from that in this video. it would be really helpful if you could elaborate on the Rochigram alignment on this machine. thank you very much!
@@shanjiang_HIT We just received a Talos here so I can do a STEM alignment for that instrument once it comes up; I did post an additional video going over the STEM alignment in better detail with better images so please see if you can find that. In that video, I actually wasn't using the Tecnai, I was using a JEOL 2010F. The nice thing with JEOL TEMs is that the C2 aperture can be completely removed, but you can't do this on the FEI instruments, you can only go to the biggest one, and then you have to manually center it on the Ronchigram. If you can see an image of the specimen in the direct disk but not a Ronchigram, then this usually means you need to adjust the C2 lens; otherwise, it could be that the C2 aperture is misaligned, but then you still may need to adjust the C2 lens.
Hi, Dr. Nicholas. Thank you so much for your video, I learned a lot! When I use the STEM in F20, I can find a couple of profiles that have been prepared for the STEM mode in the gun column. However, these STEM profiles have different parameters, such as probe size, current... I would like to know which setting should be the best for the image performance, and how I create the STEM profile for myself? If you have time, could you make a video for that? Looking forward to your reply.
Hi Li: in principle, getting best STEM resolution comes down to only three things: using the optimal semi-angle of convergence of the probe, using a high numerical value of probe size, and proper alignment. It would be a good idea for a video topic to delve into this a little deeper though, so thanks for the suggestion!
@@NicholasRudawski Hi Dr. Nicholas thank you for your reply. Recently I am trying to catch an atomic resolution STEM-EDS mapping, however, I got severe beam damage... so I am wondering whether should I use a higher spot size number such as 8 with a low current ~100pA? If you have time, could you please give me some suggestions?
Hi Nicolas, thanks for this video. One question for me is, when switching from convention TEM to STEM, the eucentric height is no longer conserved. In my case, >100 um is needed to adjust Z to see the same region/particle I saw in TEM mode. However, long-distance Z adjustment will shift the zone-axis we've done. What should I do in that situation? Or, the STEM eucentric height is just a different height and we just use the method you showed in this video to get to the right height?
btw, I have one specimen prepared by FIB, but not cleaned by Gentle Mill or Plasma Clean. Is that possible I can still achieve atomic-level HR STEM imaging?
@@yuan_tu Yes, you can get atom-resolution STEM without any post-FIB processing if your final FIB milling steps are done at low kV (5 kV or less). If you can't plasma clean the sample, then be sure to image it as soon as you can after you are done with the FIB as that is when it will be the cleanest.
Eucentric height doesn't depend on the operating mode of the microscope; it is a mechanical consideration that really only depends on the stage of TEM and not any of the lenses. An in-depth discussion of eucentric height is actually a great topic for a video (thanks for the inspiration!) so please be on the lookout for it.
@@NicholasRudawski looking forward to seeing it!
Hi, Nicholas. Did you use FIB or Ion milling for sample preparation?
Thanks for your question. The specimens used in the video and thumbnail image were both prepared prepared via Ga+ FIB.
@@NicholasRudawski Great thanks for your answer. Is it possible to do HAADF STEM with sample only prepared by Ion milling ? I am gonna do some TEM in somwhere which has same model you are using.
@@rayshen9739 sure, a sample prepared via ion milling will also work; FIB or ion milling can both be effective as long as the sample is thin enough and the damage layer is minimal; with a Si sample, it is possible to make