Видео

You're welcome; unfortunately, Velox does not offer an option to generate "corrected" maps, only "intensity" (no background subtraction, no peak de-convolution), net, at%, and wt% (which is derived from at%). Since Velox is generating at% maps, it must have tabulated and/or calculated parameters necessary to calculate the associated correction factors for each X-ray peak. Sadly, there is no way to see these correction factors, so the results Velox is producing are somewhat "black box" in nature. If you want to calculate the correction factors yourself, please check out the description of this video I did a while back on quantitative S/TEM-EDS (keeping in mind that the detector efficiency data is unique for every EDS detector): ruclips.net/video/H5HA9K3eRlo/видео.html

You're welcome.

Yes, good for some non-hr imaging. STEM-BF dislocation image of some material could be way better than TEM-BF ones.

Of course it can! BF microprobe - the best thing for all metals, because of good diffraction contrast. Even relatively good high-res STEM in nanoProbe mode could be realized without probe corrector. Just make main alignment: condenser aperture, condenser astigmatism and comma (by seeing ronchigramm) - and you will be pleasantly surprised!

Thank you!

You are absolutely correct; the Talos vacuum system is much simpler than this one!

Thank you!

You're welcome; thank you so much for your support.

What good timing! What system were you working on and what sample were you looking at?

You're welcome; thank you for your support of my channel!

Thank you!

Hi Alexander: thank you so much for the well wishes and for your support of my channel.

Hi Nataraj: thank you so much for the well wishes and your support of my channel.

Hi Stuart: thank you for your support. I've actually tweaked quite a few things with my lamella prep compared to what I did when I made this video. I don't tend to go quite as crazy with the E-beam Pt and I use a much lower current density when depositing I-beam Pt. I also no longer PFIB final thin below 8 kV, because I find that the curtaining at 5 kV (or less) is simply too severe (in spite of the supposedly thinner damage layer). A long time ago, I did use the rectangle pattern more when doing final thinning, but I now basically only use the cleaning cross-section. I find I simply have far more control of the thinning process and I end up with cleaner sidewalls using the CCS (which I imagine is how "cleaning" got in the name). If I want to be more aggressive with the thinning process, I still stick with the CCS, but I just increase the beam current. I have indeed heard good things about W as a protective cap, but have not had the chance to test this out yet. I'm curious as to what (if any) morphological differences exist between W and Pt deposited via both E-beam and I-beam.

Indexing a polycrystalline DP is actually much easier compared to a single crystal DP because there is no zone axis to consider. That being said, the process is very similar with measuring ring diameters and calculating ratios. Indexing polycrystalline DPs would definitely be a good addition to the channel and I hope to do this at some point soon.

@@NicholasRudawski thankyou

You're welcome.

Hi Ajay: there could be a lot of reasons why the Omniprobe is responding how you are describing, but the most obvious one is that the frame of reference is set incorrectly. You want this set on "Stage" instead of "Port". There could be other reasons, too, but it's a bit too lengthy to cover in a YT response. The jitters are most likely due to some kind of mechanical coupling/transfer. Again, a bit hard to cover in a YT response, but I would check your Omniprobe cabling to make sure it is properly isolated because that is the most obvious way to get vibration transfer.

Thank you for your support; I hope you found the video useful.

You're welcome

Thanks, Stan. About your question, I do not believe manual control of the energy range for a given element is possible with Velox; you are stuck with whatever "window" the software assigns. However, if you collect the map with TIA, I believe that you can do this. That being said, while TIA can give you more functionality in this regard, it is very limited in terms of collecting the actual EDS data because it only allows for "single pass" analysis whereas Velox allows for as many passes as you wish.

Sure thing; I hope you found it helpful.

You're welcome; thanks for your support.

You're welcome.

Both de-ionization and distillation are processes to remove dissolved solids, so either will be a much better option compared to normal tap water. As far as one being "purer" than the other, I'm not entirely sure on that. I've never encountered a problem using our in house DI-water for sample prep, so there really isn't any reason for me to try distilled instead. That being said, it would be an interesting experiment to simply put a drop of DI (or distilled, or tap) water (no particles) on a grid, let it dry, and then image the grid to see what (if anything) still remains. Regarding the tweezers, these are actually correctly described as "self-closing" tweezers (rather than "self-locking"). Here is a link from Ted Pella: www.tedpella.com/twzr-sc_html/twzr-sc.aspx

Thank you, glad to hear you found my video helpful; do let me know how your samples turn out for you.

Thank you for the information about the pipettes, this was certainly something I was obviously not paying a lot of attention to compared to everything else. Also, I tend to avoid support films with formvar; I've had too many issues with instability under the electron beam (though the manufacturers claim over and over that formvar is fine and stable) and plus having to dip grids in chloroform to dissolve the formvar (if needed) can introduce a source of hydrocarbon contamination (though some plasma cleaning may sufficiently address this). Did you ever have hydrocarbon contamination issues when using chloroform to prep grids?

@@NicholasRudawski Hi..it would be great if you introduce us about great variety of TEM grids and their specific applications(I mean when to choose which grid).

@@NicholasRudawski That question brings back a lot of painful memories! Actually, we don’t do that anymore. A chloroform wash can be helpful, but it can also end in a mess. Let me explain the story a bit more. Patterned grids (like quantifoils) are made using a technique called soft lithography. It’s like creating a pattern on a wafer, then making a negative pattern using a soft silicone resin (e.g., Sylgard). This pattern is then used to stamp a polymer solution (like formvar) dissolved in a solvent (probably chloroform) onto a substrate like glass. Afterward, they cover the patterned film with another layer of carbon film on top to make it conductive and stable. For random holey carbon grids, the method is slightly different, but the idea is the same: first, make a patterned formvar film, and then deposit the carbon. However, I’m not sure how lacey grids are made, but I speculate that they’re produced in a similar way. It would be best to consult older EM books. Anyway, the carbon grids are supposed to be pre-washed and free of formvar or polymer backing film from the supplier. But in the past, we often received grids with formvar contamination. In some cases, a chloroform wash wasn’t enough or even made the situation worse. It was like trying to clean a huge mess with a wipe. Also, chloroform sometimes introduced its own contamination, which was really problematic. The contamination could come from mishandled tools or consumables, and in most cases, the source wasn’t clear. It could be from filter papers, mishandled parafilm, tweezers, pipettes, or even contamination in the chloroform bottle. So yes, I did experience contamination after using a chloroform wash. But nowadays, I see far fewer of these issues. Grids are usually clean from the supplier. In case I receive contaminated grids, I pass them on to other EM groups with less strict cleanliness standards. 😂 Finally, back to the original topic: heating the grids helps stabilize many of these microscopic contaminants. However, overdoing it may also make the carbon film fragile. It's also worth mentioning that in cryo-EM, we glow discharge all the grids, which effectively removes loose hydrocarbons. Although in glowdischaging cleanliness is not intended; It’s done to make the grids hydrophilic.

Thank you for your support and glad to hear you found the video helpful. I've been meaning to set up an open access Dropbox folder for all of the presentations I post on YT, but have not gotten around to doing this yet. In the interim, I will gladly send you the presentation via email, so please send me an email requesting the presentation and I will take care of this.

Yes indeed, doing the gun alignment (even with the monochromator) isn't too difficult (and the provided instructions are very good, too). As far as time to stabilize the mono after excitation, leaving it overnight is indeed probably overkill (though not a bad idea if you have the time to allow it); I think the apps person from ThermoFisher said that a couple hours was sufficient for this.

Yes, you are correct about the discs not overlapping (or at least overlapping less) in uP-STEM versus nP-STEM. I actually discussed this in a video about CBED I did several years ago using our Tecnai. You are also correct that true BF-STEM is not really possible in nP because of the discs overlapping, so uP also has an advantage here, too. It would be interesting to do an image comparison of BF-STEM in nP versus uP using a material with lots of dislocations. This would definitely be another good video to do at some point.

You're welcome; yes uP-STEM is definitely advantageous when you are trying to avoid disc overlaps in the DPs and form true BF or DF STEM images to improve contrast. I am planning to do another MSA webinar in mid November specifically about STEM imaging so that would be a great opportunity to discuss this (as well as the comparison with nP-STEM mode I did here).

You're welcome, glad to hear you found my video helpful. Your question is a very interesting one indeed. Should there be any difference between nP and uP if the convergence semi-angle and probe currents are the same in both cases? Well, in principle, there should be no difference because angles are angles and current is current, right? With the Themis being a 3 condenser lens system, it has the capability to arbitrarily set the value of alpha in either mode, but I don't know if nP has the range to obtain alpha < 3 mrad. It actually may be easier to make alpha larger in uP mode to be comparable to alpha in nP mode. Even with alpha being the same, I believe there would be a discrepancy with the currents in a 3 condenser system because of the "zoom" between C2 and C3 which causes the current to decrease as alpha is decreased.

Great question! While the OL effectively acts like two lenses, these cannot be controlled independently, so you are changing the strength (focal length) of both at the same time. This is why the MC coil is present in the upper pole piece, to reduce the effect of the OL pre-field when it (the MC) is (optically) on, which corresponds to microprobe mode. Otherwise, the system would only have nanoprobe mode.

You're welcome, and thanks so much for your well wishes. We were actually quite lucky and spared anything remotely close to serious and we never lost power. The good news of the university being closed was that it gave me an opportunity to record and upload this video!

Hello! This could be a beam shift issue or a column-to-column alignment issue. Start by zeroing the beam shifts for both the SEM and FIB. Then, set eucentric height using the SEM image as you would normally. You should then be able to use the FIB beam shift to make the FIB image coincident with the SEM image for any stage tilt between 0 and 52 degrees (the amount of FIB beam shift necessary will vary somewhat with stage tilt). If you are running out of FIB beam shift, this indicates the default FIB beam shift needs to be adjusted at the supervisor level or there may be a column-to-column misalignment. The former issue is something the instrument owner should be able to adjust, but the latter issue most definitely requires a service visit from a service technician. I hope this helps.

Thank you very much for your advice!

@@quyenhiennguyentruong4854 You're welcome; I hope your are able to get you system working properly soon.

You're welcome; yes, I I do want to make a 4D-STEM video covering EMPAD use at some point. In the interim, there are quite a few good videos already on YT about 4D-STEM (not really about how to perform it and collect the data, but about the applications and analysis of the data). There is a really good one on the Gatan YT channel that should show up in a basic search.

@@NicholasRudawski Sir，Thank you again for these useful information!

@@zhedd5954 You're welcome

sorry, too much fundamental questions! though I use TEM for many years, but never get chance to understand the mechanism behind it and why we do it. your video is great resource for me to backfill these knowledge! appreciated

@@jq58 thanks for watching my video. Yes, I apologize for not addressing the equivalent situation for two condenser systems, so I will do so here. In a two condenser system, you will no longer have the ability to maintain parallelism over a range of beam diameters; instead, there will be a single diameter corresponding to a parallel beam (when the spots are focused in the DP). The process as you describe it in your first post is otherwise correct (including the part about using "diffraction focus" to focus on the objective aperture). If the instrument is properly aligned and configured, the default "eucentric focus" value in diffraction mode shouldn't need tweaking, but it never hurts to check by imaging the OA. On my system, it is a little more complicated because I find that the DP spots become quite astigmatic when I have a perfectly focused, stigmated image of the OA, so when I stigmate the spots, the OA image loses sharpness. Not sure why this happens, but it likely has something to do with the presence of the Cs probe corrector.

@@NicholasRudawski Hi Nic, thanks for clarification. In the diffraction mode, I can rotate intensity knob clockwise to make diffraction spot a small spot, but if I keep clockwise rotating intensity, the diffraction spot is still a small spot but weaker in brightness, it seems that the beam is parallel if the intensity below certain value. but as you mentioned "there will be a single diameter corresponding to a parallel beam". it confuses me that how can I determine beam intensity to find the parallel condition since the diffraction spot keep constant small if intensity below certain value by clockwise rotation?

@@jq58 was your SA aperture inserted when you were trying to focus the spots in the DP? You need to make sure to do this without the SA aperture inserted. If the SA aperture is inserted, then you will not see the proper response from the spots as you change the intensity knob. You always want to focus the spots without the SA aperture inserted, then do not adjust the intensity knob as the beam is now parallel, then insert the SA aperture.

I have a question with the illumination area. our Themis has been 6 years old. One day I found if I focus beam into a spot, the illumination area is not zero. but if it show zero, the beam is a small disk. where can I reset this zero point?

@@jq58 Thanks again for watching my videos. And yes, I've seen this issue before, too; the beam diameter is non-zero but the UI says it's zero! If you perform the full "Condenser" alignment, this should address this, but In my experience, the actual diameter never perfectly matches the expected diameter due to hysteresis and other factors. This discrepancy tends to be more pronounced in the vicinity of the crossover point (diameter = zero) and less so as the beam is spread out within the "parallel" regime.

@@NicholasRudawski thanks you so much for the useful information. The full condenser alignment works, the correlation of beam spot with zero illumination area is much better now on our machine

You're welcome; glad to hear my video helped you out.

Hey, sorry for the late reply. Thank you for the feedback and glad my videos are providing useful information for you.

Hey, sorry for late response. Your question about seeing detail beyond the limits of the OA is a great one and really deserves an entire video to properly answer it. That being said, the short answer for why detail beyond the OA limit is observed is due to non-linear effects, which is another way of saying interference between different Bragg beams rather than interference between Bragg beams and only the direct beam. If only interference between the Bragg beams included in the OA and the direct beam was transferred to the image, then we would not see any detail beyond the OA limit, but this is never the case because interference between Bragg beams does indeed happen. This is one of the advantages of HAADF-STEM over HR-TEM: the information limit in HAADF-STEM never exceeds the probe size due to the incoherent nature of the imaging, which does not rely on any contributions from Bragg scattering. Again, this question really deserves a dedicated video, and I hope to do this eventually.

@@NicholasRudawski Hey Nicholas, no worries about the late reply. Thanks for taking the time! I agree with you and now understood this effect. Indeed, we also perform mostly HAADF-STEM nowadays, so these "phase-contrast problems" never show up there in this extend. :-) I can imagine that interference between the Bragg reflections can indeed cause the higher-order reflections, e.g., +g/-g -> 2g or something along that line - even if the 2g spatial frequency would be outside of the OA radius. That's all probably also related to using very thin samples (i.e., within weak phase object approx.) for quantitative HRTEM/comparison with image simulations. I will have another look into textbooks. Nowadays, "simple" lattice fringe imaging is often good enough for my cases.