Question 1

How often should I correct for the spatial drift during a STEM spectrum imaging acquisition?

Accepted Answer

This depends on the amount of drift. The more severe the drift, the more frequent the correction needs to be set up.

Note: The drift correction procedure increases the total exposure time for the entire dataset.

Question 2

Why is the intensity of the EFTEM spectrum imaging negative at high energy losses?

Accepted Answer

This is typically caused by afterglow of the phosphor. To minimize this effect:

Acquire the data in reverse direction using the “Acquire high to low” option in the spectrum imaging software
Avoid exposing the camera to the unfiltered or elastic (ZLP filtered) image prior to acquiring a core-loss EFTEM spectrum imaging
Do not use the option “Align ZLP before acquire” option in the spectrum imaging software

Question 3

Why does a strange shadow exist in the images and maps?

Accepted Answer

This is caused by tuning of the Filter or an incorrectly centered zero-loss peak (ZLP). It is good practice to tune the filter (using the Tune for spectrum focus option in AutoFilter) at the magnification you will be using to acquire your maps. Do this at the early stage of the setup to avoid scintillator afterglow.

Question 4

Why does a semicircular shadow appear in a corner of my EFTEM spectrum imaging (the shadow may shrink into a circle or drift across the image field of view)?

Accepted Answer

This is typically caused by a poorly calibrated Condenser Adjustment. As the HT is changed to acquire the EFTEM spectrum imaging, an automated adjustment must be made to the condenser focus and deflectors. To run this calibration, make sure the system is in Power User mode and run the menu item “EFTEM | Calibrate | Calibrate Condenser Adjustment …”. This is best done with a sample in the TEM and moderately thick area in the field of view (1 – 2 mean free paths). Simply follow the online prompts.

Question 5

Strange shadows exist in the acquired images or maps.

Accepted Answer

At the start of an energy-filtered transmission electron microscope (EFTEM) mapping session, or if strange shadows exist in acquired images or maps during a session, perform Tune GIF in the AutoFilter^® palette and repeat. For more details refer to the tuning document.

eaSI Spectrum Imaging FAQs

How often should I correct for the spatial drift during a STEM spectrum imaging acquisition?

Why is the intensity of the EFTEM spectrum imaging negative at high energy losses?

Why does a strange shadow exist in the images and maps?

Why does a semicircular shadow appear in a corner of my EFTEM spectrum imaging (the shadow may shrink into a circle or drift across the image field of view)?

Strange shadows exist in the acquired images or maps.