Understanding TEM Calibration Patterns: NiOX vs SiGe Explained

[Rapier]

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 realized 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

.

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

.

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! :)

 

[Astronuc]

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 realized 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 View attachment 76194.

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 View attachment 76195.

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! :)

"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

 

[Rapier]

Ah! Thank you! I spent about 45 minutes searching and was getting no where.