I'm looking for some provision to directly visualize the imaging probe of a normal SEM.
It is impossible. The best CCD camera has a pixel size not less than 1 micrometer. The electron probe's diameter is not more than 100 nm (typically, < 10 nm). You will just destroy a pixel without any results.
The direct measuring of the probe diameter is an interesting physical problem. There are some methods for solving it. For example, see this article and references:
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2818.1987.tb02840.x/abstract
Good luck!
No. Even if you could put TEM camera into SEM, you'll burn pixels under the focused beam.
It is impossible. The best CCD camera has a pixel size not less than 1 micrometer. The electron probe's diameter is not more than 100 nm (typically, < 10 nm). You will just destroy a pixel without any results.
The direct measuring of the probe diameter is an interesting physical problem. There are some methods for solving it. For example, see this article and references:
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2818.1987.tb02840.x/abstract
Good luck!
You can also check this
http://people.umass.edu/jig0/files/176.pdf
In the dedicated STEM I have CCD, but also projection lens. Then on the CCD I can see Ronchigram, but not the beam diamater :(
If You will find easy way to measure beam diameter please let me know.
Thank you all. I agree with all your observations, especially that of Vladimir. A focused electron beam might actually damage the camera. Probably with an underfocused probe, I'd be able to obtain a magnified image of the probe cross-section at the image plane. Ofcourse with the assumption that beyond the image plane, the beam travels in a field free region...
Denis, my institution doesn't seem to have access to Wiley's journal :| So, if you'd be kind to send in the pdf copy of the paper please.
Tomasz, don't know if it is possible but, if you turn off the projector lens supply, then I guess you should be able to get an image of the beam diameter. What say ?
I am totally at one with all the above lively discussions on the question asked :-)
The CCD camera plane is far away from the focusing plane, so because the beam is convergent then You will see disk on the CCD, of course when I switch off the projection lens, then the disk will be ......... hmmmm I am not sure I have to check :) , but as it was mentioned above, the beam diameter is smaller than pixel size on the CCD.
Off course it is possible to burn the CCD (not the CCD itslef, but just fluorescent screen), It happens at least once in our lab. But only with very strong current and long exposure time in the STEM mode at 120kV. Typically the proper CCD should survive electron beam. They can survive diffraction in the TEM at 300keV.
If You want to play with CCD in SEM at loe kV like 30 then You can ask someone who have new Oxford EBSD, where they placed fluorescent screen under the beam.
Why You need beam diameter? I think in the SEM is more important, what is the interaction volume :)
It is true that a defocused ring will be visible on the CC camera. The beam might get collimated to an extent considering the distance between focal plane and the CCD. But then if the projector is operated at a selective low excitation level, probably a true image can be formed on the CCD - not really sure of that though, coz for magnification one needs the ratios of image distance to object distance to be greater that unity atleast. I'd like to know how it turns out to be.
Coming back to the reason why I wanted the information was, if not the probe diameter atleast if aberration in the probe could actually be visualized, it would help me in qualification of some condenser lens pole-pieces that I have. We are in the process of making our own focusing column, so this was supposed to be a direct QC. Purely experimental :)
Do You know what is this Ronchigram?
We are using Ronchigram in our STEM for every day alignment of astigmatism and come, I think it is very nice feature to quick observations of the basic beam aberrations.
To see higher level aberrations You should use techniques, which are implemented in the Cs corrector software.
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