EELS

Caution

VERY ROUGH DRAFT - @bobleesj and Guoliang Hu took notes and pictures during training. This document will be updated with more detailed steps and images.

TODO:

• Add image for “EELS Scan” button (Step 2, Part 3)
• Better photo for STEM SI button
• Show what auto gain looks like
• Clarify zero loss extraction steps
• Add comparison images for beam not centered

This guide covers Electron Energy Loss Spectroscopy (EELS) on the Spectra 300. The process has two parts: calibration in TEM mode and STEM EELS spectrum imaging.

Prerequisite: Complete the STEM alignment procedure before starting.

Acronyms:

• GIF - Gatan Imaging Filter
• EFTEM - Energy Filtered Transmission Electron Microscopy
• ZLP - Zero Loss Peak
• SI - Spectrum Imaging
• mulXY - Multifunction X/Y knobs on hand panel

Part 1: Calibration

Use a vacuum or thin amorphous carbon area for calibration.

1. Find a calibration area

   • Locate a vacuum region or thin amorphous carbon area on the standard sample

2. Open DigitalMicrograph

   • Open DigitalMicrograph on the left monitor

   • If you see any dialog box, click OK to dismiss

     

   • Click EFTEM (Energy Filtered Transmission Electron Microscopy)

3. Open FilterControl

   • Go to Help → User Mode → Power User

   • Go to Window → Floating Window → Filter Control

     

   • Notice the green circle in TEMUI showing EELS detector is active

     

4. Set beam intensity

   • Converge the beam by adjusting the intensity knob

     

   • Lift the fluorescent screen by pressing R1

   • Click View in DigitalMicrograph

   • Go to Filter Control → Aperture → Mask to verify beam position

     Correct intensity:

     

     Too high intensity (oversaturated):

     

5. Center and tune the GIF

   • Click Center ZLP in Filter Control

   • Click Tune GIF. Notice the message appears:

     

   • Click OK to confirm

Part 2: TEM EELS acquisition

1. View the sample

   • Set magnification to ~17,000x

   • Click View in DigitalMicrograph

   • Select EF-CCD Camera → View to see image real-time

     

2. Acquire zero loss image

   • Go to SingleMap → click Zero Loss Image

     

3. Switch to EELS mode

   • Click EELS button to switch modes

     

     FIXME: use image where EELS is clicked

   • Notice the 2D EELS spectrum. Observe the plasma peak near the zero loss peak.

     

   FIXME: what’s plasma peak?

4. Align the zero loss peak

   • Set exposure to 2e-4 in View mode

   • Click Align ZLP

     

     FIXME: where is ZLP click?

Part 3: STEM EELS spectrum imaging

1. Set camera length

   • In Velox, change camera length to 29 mm or 37 mm

   • Notice the beam size decreases

     

2. Enable EELS scanning

   • Press EELS Scan in the software

   FIXME: attach image

3. Find a vacuum area

   • Navigate to a vacuum region for initial alignment

4. Center the beam

   • In EFTEM mode, use mulXY knobs to center the beam

     Before centering:

     

     After centering:

     

5. Switch to STEM SI mode

   • Click STEM SI to switch to Spectrum Imaging mode

     

6. Find sample area

   • Navigate to an area of interest on your sample

7. Start scanning

   • Click Scan → View to see the image

     

8. Adjust gain

   • Right-click on ADF image → click Auto Gain

   FIXME: add image showing auto gain result

9. Stop viewing

   • Click View again to stop live scanning

10. Capture line scan (1D EELS)

    • Click Capture and draw a line across the region of interest

      

    • Go to EELS → User Mode

      

    • Go to EELS → Zero Loss → Extract Zero Loss

      

      FIXME: clarify what “extract zero loss” does and expected result

11. Capture area scan (2D EELS)

    • Click Capture and select a rectangular area for 2D spectrum imaging

      

      FIXME: add steps for analyzing 2D EELS data, expected output

Part 4: End session

Follow the steps in End session.

Changelog

• Dec 18, 2024 - initial rough draft by Guoliang Hu and @bobleesj