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TEM Calibration Pattern

  1. Dec 4, 2014 #1
    Ok, so we were doing TEM and at the end we were looking at calibration patterns and I'm preparing the presentation and I am writing the intro but I realised I'm not sure why the calibration pattern looks like concentric circles.

    I believe it is because we are scanning the beam across the sample at different angles and this is causing the concentric ring pattern.

    This is NiOX Cal1.png .

    In this second one I'm not quite sure why we don't get concentric rings but just spots. I know that those spots are the locations of the molecules in our crystalline matrix, but I don't get why it's circles in the first and dots in the second. The manual that we used is rather unhelpful in explaining why. In a lot of cases the manual walked us through the steps but didn't really explain why we were doing what we were doing.

    Please help!!

    This is SiGe Cal2.png .

    The presentation is mostly done but I'm just tweaking and want to get the intro for this section done and I'm short on time. Thanks! :)
  2. jcsd
  3. Dec 4, 2014 #2


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    "If the material is microcrystalline (or polycrystalline with different crystal orientations) or amorphous the diffraction pattern consists of a series of concentric rings rather than spots/discs." I believe the spot pattern comes from a single crystal orientation.

    Here is a reasonable discussion - http://www.ammrf.org.au/myscope/tem/background/concepts/imagegeneration/diffractionimages.php

    And - http://faraday.physics.utoronto.ca/IYearLab/elecdiff.pdf
  4. Dec 4, 2014 #3
    Ah! Thank you! I spent about 45 minutes searching and was getting no where.
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