Jump-ratio map

Two techniques are commonly used in EFTEM to map elemental distribution: 2-window ratio mapping and 3-window elemental mapping. The jump-ratio approach requires two energy-filtered images, one you position just before the ionization edge (pre-edge) and one you position just after the edge (post-edge). In the jump-ratio approach the post-edge image is divided by the corresponding pre-edge image to produce a map that is indicative of the distribution of the element you select.

  1. To acquire a jump-ratio map, specify

    1. Element of interest

    2. Camera parameters

    3. Slit width and filter energies to be used for the pre- and post-edge acquisitions

  2. Access the Configure Jump Ratio dialog will vary based on the mode you chooseConfigure Jump Ratio

    1. SingleMap mode – Press the Select Jump-Ratio Map button

    2. MultiMap mode – Specify via the MultiMap Configuration dialog

    3. Indicate parameters within the Configure Jump Ratio dialog

      1. Window settings (eV)

        1. Setup – Allows you to recall pre-saved or default settings for a particular element

        2. Slit width – Specify the energy-selecting slit width you want to use for both the pre- and post-edge acquisitions

        3. Post-edge – Designate the energy loss setting that the filter will use to acquire the post-edge image

        4. Pre-edge – Indicate the energy loss setting that the filter will use to acquire the pre-edge image

        5. Edge – Specify the edge you want to use for ratio mapping

      2. Detector – Specify the detector settings you want to use

      3. Spectrum display – Generates and displays a simulated spectrum at the top of the dialog to give you visual feedback regarding the feature shape and the selected acquisition window positions

    4. Click Capture

      Jump-ratio map data

The routine will

  • Acquire the post-edge image followed by the post-edge image

  • Correct for any spatial drift between the images

  • Compute and display the ratio map

Jump ratio image
When you create a jump-ratio map, first insert the slit and focus the image at an energy loss (typically 400 eV and 50 eV slit) before acquiring a pre-edge image. Acquire the pre-edge image, and then shift the energy to after the edge to acquire the post-edge image. To calculate the ratio, divide the post- by the pre-edge image value.