Scanning/Transmission Electron Microscopy: Today's Essential Techniques 

Thank you; I actually had several other slides about HR-TEM that i wanted to include (with a bit more technical nitty gritty stuff), but I ended up cutting to keep the total time more reasonable (though now in hindsight, I suppose I could've put them in for this version of the webinar).

You're welcome; I'm glad to see people are seeing the rerecorded version. About your OA question, yes, you will always get a better HR-TEM image with an aperture than without an aperture, because this limits the effect of spherical aberration, increases mass-thickness contrast, improves depth of field, and decreases image delocalization.

@@NicholasRudawski I had some thoughts about it, but now you've really opened my eyes! I always was made HRTEM images without an OA. And only recently I began to think about why I should use multiple n-reflexes that are not responsible for any details in the image. And then I filtered HRTEM by FFT to make it better ))) Thank you for highlighting this basic aspects, which helped me identify a gap in my knowledge.

@@adrianzavodov6745 @NicholasRudawski I can add to this question for the case of an image-corrected Titan with the default OA set: I was wondering the same ("To use OA or not to use OA?") on an image-corrected system. The default OA set "only" goes up to a 100 µm size and I measured once that this corresponds to a radius of around 9.5-10 nm-1 (i.e., around 100 pm resolution). An image-corrected Titan is typically specified with an HRTEM resolution of 80 pm (under ideal conditions and a nice sample). So in this case of an image-corrected TEM, I was imaging HRTEM without an objective aperture. However, I probably would have used a potentially large OA that cut of at 80 pm (= 12.5 nm-1) if it was available due to the reasons Nicholas mentioned. For uncorrected systems, I try to use the closest OA given by Nicholas' formula in the video (typically around 40 µm for 200 keV TEMs).

​@@electronmicroscopist1986 Yea, this works great! I've tried it today with 40 mkm OA and without it. The main improvement - reduction of ghost images (delocalization) and as a sequence more uniform focus over entire field of view. Live and learn!

Hi Crystal; glad you like my webinar. 4D-STEM has certainly been requested by quite a few people up to this point. It would need to be a 2-part series: one part discussing the collection of the data and the second part discussing the actual analysis of the data. I definitely hope to get around to this sooner rather than later (particularly the part about data collection, because I feel this is really quite lacking based on what is available here on YT). That being said, there are already some very good YT videos talking about the applications of 4D-STEM; this one from Gatan is probably my personal favorite: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE--KpxeNDoB5I.html

How to find kikuchi pattern (TEM and STEM mode) in thin sample for good zone axis alignment ? Please help Sir.

​@@arupghoshal5814 Kikuchi diffraction will decrease as the sample becomes thinner; at some point, you may not observe any Kikuchi diffraction at all, so this definitely can make it more challenging to obtain accurate zone axis alignment in a very thin sample. It is actually easier to check the alignment in STEM mode, since CBED patterns are more sensitive to crystal tilts. After you align in STEM mode, you could then go back and perform TEM imaging on the same location. Otherwise, if you only use TEM mode, you need to evaluate the symmetry of the intensity of the spots in the diffraction pattern. Please check out this video on zone axis alignment when performing S/TEM (apologies if you already did): ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-0VfJLJP6tP4.html