Why you should align/focus via C2 (not OBJ) when performing uncorrected STEM (Talos, Tecnai)

Описание: Hey EM aficionados! As promised, here is the video (as always, recorded raw, unedited, unfiltered, uncensored, and uncut) about focusing in STEM mode on an S/TEM without Cs probe-correction (uncorrected). This is the "companion" video to the one I uploaded a few days ago discussing focusing in STEM mode on an S/TEM with Cs probe correction, which you can see here, in case you missed it:

   • FEI Themis Z S/TEM (Cs probe corrected): p...  

Once again, I cover the different focusing options for STEM mode, which can be found by navigating to the "STEM Imaging (Expert)" control panel, selecting the "flap-out" arrow in the upper right corner, and then the "Focus" tab. Here is a summary of the four different focusing options:

Intensity: "Intensity" knob = inactive, "Focus" knob = C2
Objective: "Intensity" knob = inactive, "Focus" knob = OBJ
Step Size Dependent: "Intensity" knob = inactive, "Focus" knob = OBJ (focus step = 1) or C2 (focus step = 2 or higher)
Intensity and Objective: "Intensity" knob = C2, "Focus" knob = OBJ

Most importantly, I discuss (and hopefully clearly demonstrate) why you should perform all your alignments/focusing via the C2 lens (not the OBJ) when performing STEM imaging on a system without Cs probe correction.

Thank you for your support, my fellow EM aficionados, as we have now surpassed 5,000 subscribers! Please like, subscribe, and share and leave any questions or comments you may have and I will do my best to reply as soon as possible. Video topic requests are always welcome and appreciated; I enjoy making these videos and wish I could make them more frequently, but the demands of my job make it tough to do so; I’m in charge of three S/TEMs, three dual FIB/SEM systems (a new one recently signed off on), and half of an SEM and this keeps me very busy!

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