Hi everyone; there are a couple important corrections here that I want to point out regarding setting the C3 lens to focus the probe that I discuss at 18:00. Point 1: the proper appearance of the probe (in vacuum) is a sharp caustic spot surrounded by a diffuse halo; this is different from what I show in the video. Point 2: if your alignment file is properly set up, there should be no need to adjust the C3 or objective lenses from the "eucentric focus" setting to obtain the proper probe appearance. Point 3: the caustic spot should still remain stationary when the beam it tilted (just like how I show here, but with the probe appearance being different) if the C3 and objective lenses are properly set. In a subsequent video I did on S/TEM alignment and imaging, I do show the proper probe appearance and also state that adjusting C3 and the objective lenses from "eucentric focus" shouldn't be necessary: kzread.info/dash/bejne/doytuJKqhpe-p9I.html Sorry for any confusion; I always want to make sure people have the most accurate information possible.

Timestamps: 1:30 discussing appropriate samples for corrector tuning 2:50 gun settings and alignment 5:45 C2 aperture selection and centering 7:30 entering STEM mode and setting convergence semi-angle 8:45 spot size selection 11:00 resetting objective lens, stigmators, beam shift, and beam tilt in the UI 16:30 manually correcting beam shift and tilt with S-CORR (1st time) 18:30 setting C3 lens (Intensity List FOCUS) 20:00 manually correcting coarse A1 and B2 with S-CORR (1st time) 33:00 measuring convergence semi-angle 36:45 setting camera length, magnification, and detector contrast/brightness 40:00 C1A1 measurement in S-CORR (1st time) 44:00 tableau measurement and auto correction in S-CORR (1st time) 50:00 manually correcting beam shift and tilt, coarse A1, and coarse B2 in S-CORR (2nd time) 54:00 C1A1 measurement in S-CORR (2nd time) 56:30 tableau measurement and auto correction in S-CORR (2nd time) 1:01:00 C1A1 measurement in S-CORR (3rd time) 1:05:45 tableau measurement and auto correction in S-CORR (3rd time) 1:08:00 manually correcting coarse A1 and coarse B2 in S-CORR (3nd time) 1:10:00 C1A1 measurement in S-CORR (4th time) 1:12:40 tableau measurement and auto correction in S-CORR (4th time) 1:15:20 saving updated alignment file

A small correction at 8:47 when discussing spot size (number) selection: DECREASING the spot size by one increment increases the probe current by approximately a factor of 2. I actually did this in the video (changing spot size from 9 to 5) to obtain an appropriate probe current, but verbally, I incorrectly stated this as INCREASING the spot size to increase the probe current (sorry!).

Hello Nicholas. Your videos are very good, I'm always learning new things, as well as tips and tricks about TEM. I would like to know if I can use the same strategy of making some manual adjustments using the Cs correction software for image mode (TEM mode)? Another question is: How often should I adjust the Cs corrector? Is weekly acceptable, considering that I work in an open facility research center? Thank you very much and see you next time.

@NicholasRudawski

2 ай бұрын

Hey, sorry for the late response. Great to hear from you and it's always great to hear that my videos are helping people learn new things and get better at operating their instruments. Regarding your questions about doing this for an image corrector, I'm afraid I will have to somewhat plead ignorance here as I do not have any experience using or tuning one (sorry). That being said, my understanding is that the process is very similar in that the beam is tilted to a high angle and then azimuthally rotated and then a sequence of images collected; the difference is that for an image corrector I believe you are imaging amorphous material rather than AuPd particles like with the probe corrector. The question about frequency of tuning is a good one, too. Generally, the higher order aberrations are more stable with time than the lower order ones and those (higher order) are the ones the corrector is primarily designed to correct. I usually tune my probe corrector about once a month and this works well. Doing this every week is probably a bit overkill, but certainly won't hurt anything (though it will take up more of your time). Of course, if there is a voltage change or some other big change to the system, I will also perform tuning immediately afterwards. Is there someone in your facility in charge of the system or are you having to do this yourself? If someone is in charge, I would ask him/her about how frequently this is being done. He/she should be keeping track of the tuning results (at least, this is what I personally do) and updating the alignment file accordingly.

Great video! The caluclated phase plate seems to be an essential tool for aberration determination. Could you elaborate on that, maybe in another video? Thanks!

@NicholasRudawski

Жыл бұрын

Hi Shan: glad you like the video. If I under it correctly (and full disclosure, I may not) the phase plate itself does not determine the aberrations, but rather tells you what your Ronchigram will look like with the measured aberrations from the tableau. If you look at it the phase plate, you can see it's basically a simulated Ronchigram. What actually is used to determine the aberrations are the probe shapes at under and over focus when the probe is tilted to high angles (30 - 40 mrad) and azimuthally rotated. Then the computer basically takes it from there and solves a bunch of equations to determine the aberration coefficients. There are some good papers out there that go over the mathematical details of this; if you email me, I can point you to some.

I like your video. I've learned lots of thing from your video. Could you upload a video about EELS operation, such as tuning the stigmator, alignment, acquire spectra with mono and so on? Thank you for your share.

@NicholasRudawski

Жыл бұрын

Thank you. Yes, I do eventually plan on doing an EELS video; doing EELS is rather involved so I want to make sure I have a good grasp of it first. But yes, there will eventually be an EELS video.

Nice video, a very important detail when during corrector, the beam shift and beam tilt neutral. While I am not clear whether this process works when tuning image corrector, specially for negative Cs HRTEM?

@NicholasRudawski

Жыл бұрын

Hi Zhipeng: thank you. Regarding image corrector tuning, I think the process is rather similar to probe corrector tuning, but relies on FFTs of high-res images of amorphous films rather than HAADF-STEM images of high contrast particles (though the same sample would work for tuning either probe or image corrector).

Hi Nicholas, thanks for your brilliant video and I have a shallow question. I am wondering how to judge that A1 and B2 are optimally adjusted in Ronchigram? Do you have any vivid description😂? Thanks

@NicholasRudawski

5 ай бұрын

Thank you, Blake; sorry for the late reply. For B2, you wobble the objective lens and you check that the expansion/contraction of the Ronchigram is concentric; this is usually very obvious, particularly when B2 is very large. For A1, this can be a little tougher to see, particularly is the area is not completely amorphous. What you are looking for here is two-fold symmetry in the Ronchigram. If you can see this clearly in the Ronchigram, then A1 is not corrected. What you should be seeing is a 6-fold symmetry in the Ronchigram if A1 is corrected. Seeing A1 is actually much more obvious in the actual STEM image, since you can see "streaking" in the image that reorients by 90 degrees when going from over- to under-focus. Thank you for your support and I hope this helps.

@BlakeCao-fc4qh

5 ай бұрын

Oh! I am sorry for the too late reply.🥲 Thanks for your patient answer, your reply is very useful. Give you a big hug🥰@@NicholasRudawski

Hi Nicholas, Thanks for uploading this helpful and educational video. My problem is slightly irrelevant to Cs corrector but relevant to C3 lens. I'm trying to do thickness measurement by CBED technique under STEM mode in which I can preciously hit my desired position. I have to make the convergence angle(alpha) small so that my CBED disks would not overlap. To do so, I loaded the uP STEM mode with 50 um C2 aperture. Unfortunately, my CBED disks still overlapped with others. I'm guessing to manipulate the C3 lens in uP STEM mode and to reduce the convergence angle further. I'm not sure how to do that. Do you have any suggestions? Thanks in advance and happy new year.

@NicholasRudawski

Жыл бұрын

Hi Yao: good to hear from you. So if I understand you correctly, you are in uP mode with the smallest C2 aperture but your discs are still overlapping? Just like in nP mode, you should have the ability to modify the semi-angle of convergence of the beam in uP mode. I think you can do this in the "beam settings" control panel. I know on our system, when using the smallest C2 aperture, we can obtain alpha ~ 0.5 mrad as the smallest value. If the discs still overlap, it may simply be related to the structure of the material (maybe it has a very large lattice constant?).

@yaoli7081

Жыл бұрын

@@NicholasRudawski Hi Nicholas: yes, your understanding is 100% correct. Thanks for your explanation and help!

Thanks for the fantastic job! We don't have STEM autotuning feature and I see no other button to change B2 manually. Do you know how I can zero the B2 value in TIA since I see some numbers exported to S-CORR?

@NicholasRudawski

Жыл бұрын

Hi Andrey: you're welcome. Regarding your question, please first tell me what model of FEI microscope are you working on and whether or not the system has Cs probe correction, thanks.

@andrey1690

Жыл бұрын

@@NicholasRudawski a double-corrected Themis

@NicholasRudawski

Жыл бұрын

@@andrey1690 Hi Andrey: this is a little too involved to discuss via YT comments. Please email me directly so we can discuss this further; I put my email in the video description.

It is a really nice video for student, will you upload a video about Lorentz mode imaging? Actually, our TEM has the Lorentz lens, but no one knows how to use it.

@NicholasRudawski

Жыл бұрын

Thank you; our system also has a Lorentz lens, so eventually I can do a video covering how to use it. It's actually quite easy. What is a little more involved is Lorentz STEM, which is a type of differential phase contrast imaging and gives a lot more information than Lorentz TEM. What kind of TEM do you have?

@yihongji1962

11 ай бұрын

@@NicholasRudawski Hi Nicholas, great video as always! I've learned a lot from you. In terms of the Lorentz, I was wondering if you could upload a video about DPC measurement? That would be fantastic! Thank you very much again!

@NicholasRudawski

11 ай бұрын

Thank you; Lorentz TEM mode is actually not very useful in a lot of ways; it can be used to highlight and separate the magnetic domains, but it does a poor job of actually giving you information about the orientation of the domains. To do that, it would be better to do "Lorentz STEM", which is just 4D-STEM done in LM mode with the objective lens (nearly) off; if you search "Lorentz STEM" on KZread, there are a couple very good presentations covering this.

@NicholasRudawski

11 ай бұрын

@@yihongji1962 Thank you; DPC-STEM can be covered as a part of 4D STEM using an EMPAD. This is actually a more effective way to do DPC imaging as opposed to using segmented STEM detectors. Thanks for the suggestion.

hello,I have a question.when I use ascore corrector to get high resolution,ronchigram is unstable,only can keeping 2min then image slowly worse ,why😂??

@NicholasRudawski

Жыл бұрын

Hi qinblenden445: are you saying your alignments only stay good for 2 min after tuning? In general, the lower the order of aberration, the less stable it is with time. Things like 2-fold astigmatism (a first order aberration) need to be corrected every few minutes (particularly when atomic-resolution imaging). Second order aberrations (3-fold astigmatism (A2), axial coma (B2), etc.) tend to remain stable over the course of a typical operating session (hours) after correction. Are you also sure that sample contamination is not a factor in your images? Sometimes when someone describes the "image getting worse with time" this is due to carbonaceous contamination build-up, which is completely independent of your corrector tuning, but would obviously affect your image (particularly atomic-resolution images).