Thickness map

You can produce a relative thickness map relatively easily in the EFTEM technique by acquiring an unfiltered and a 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. Thickness mapTo 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 mode – Press the Select Thickness Map button

    2. MultiMap mode – 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

Thickness map data

The routine will

  • Acquire an unfiltered image followed by a zero-loss (elastic) image

  • Correct for 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.