Thickness Map

You can relatively easily produce a relative thickness map using the EFTEM technique by acquiring an unfiltered and zero-loss image from the same region under identical conditions. Once acquired, you can compute the relative thickness map when you utilize the Poisson statistics of inelastic scattering:

$$t/\lambda = -ln (\frac{I_{o}}{I_{t}})$$

where

• $I_{t}$ = Total intensity (unfiltered)

• $I_o$  = Zero-loss intensity (elastic or ZLP filtered)

   

1. To acquire a thickness map, specify the slit width for the zero-loss acquisition and the camera parameters to be used.
   1. The same camera parameters will be applied for both the zero-loss and unfiltered image acquisition.

2. Access the Configure Thickness Map dialog will vary based on the mode you choose.
   1. SingleMap – Press the Select Thickness Map button
   2. MultiMap – Specify via the MultiMap Configuration dialog
      1. Window Settings – Set the energy loss (0 eV) and slit width for the filter
      2. Detector – Specify the detector settings you want to use
3. Click Capture.

The routine will

• Acquire an unfiltered image followed by a zero-loss (elastic) image
• Correct any spatial drift between the images
• Compute and display the thickness map

References

Malis, T.; Cheng, S. C.; Egerton, R. F. EELS log ratio technique for specimen-thickness measurement in the TEM. J. Electron Microscope Technique. 8:193; 1988.

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3. Click Capture.