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COSMO corrector (TEM)

COSMO corrector (TEM)

Nov 29, 2017

Do not attempt to do anything you have not been trained to do by ePSIC staff.

In order to run the COSMO corrector the sample must have areas of thin amorphous material. Any lattice in the image may interfere with the aberration calculation.

If sample contaminates significantly the aberration correction may fail. If possible beam shower the sample.

  1. Ensure that the objective lens is set to standard defocus and microscope at x800k or greater.

  2. Increase the height of the sample so that the image is under focus (rings get smaller as you move sample -z) and numerous thon rings can be observed.

  3. Stop the view on Digital Micrograph and press monitor on the COSMO TEM auto-adjust software.

  4. Using COSMO software correct 2 fold astigmatism (A2) to ≤5nm.

  5. Using the z-piezo drive set defocus to about -200nm.

  6. Set the tableaux angle to the required level (recommended to start at ~20 mrad) and run a tableaux.

  7. Correct for higher order aberrations.

  8. Iterate 4-7 as required.

 Aberration

JEOL notation

'Good' value

 Aberration

JEOL notation

'Good' value

 Defocus

O2

n/a

 2-fold stig

A2

<5nm

 Coma

P3

<50nm

 3-fold stig

 A3

 <50nm

 Spherical

 O4

 <2um

 Star

 Q4

 <2um

 4-fold stig

 A4

 <2um