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COSMO corrector (STEM)

COSMO corrector (STEM)

Jan 23, 2018

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.

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

Ensure super fine control of the objective lens (super fine defocus) is not selected.

  1. Ensure at zero defocus and set sample height to infinite magnification on thin amorphous material.

  2. Set camera length to 40cm and centre the ronchigram on the OneView camera with the PL deflectors.

  3. Stop the OneView camera.

  4. Ensure Cosmo software is in STEM mode and select 250nm defocus.

  5. Press single on the Cosmo software and correct for P3, A2 and O2.

  6. Repeat step 5 until P3<300nm, A2<50nm and O2< 10nm.

  7. Press single then press run to correct for higher order aberrations.

  8. Iterate steps 5 to 7.

  9. Once aberrations converge reduce the defocus to 150 nm and repeat steps 5 to 8.

  10. Further reduce the defocus stepwise to 25nm iterating steps 5 to 8 until required aberration values are reached.

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

 

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