Identify edge features in spectrum

Once you acquire the spectra, it is time to identify your edge of interest. 

Edge identification for EELS quantification

Common indicators you may use to identify your edge include:

  • Edge threshold energy (e.g., point of steepest rise)

  • Edge shape (e.g., hydrogenic, delayed, white lines)

  • Accompanying edges (e.g., Si L-edge at 99 eV, Si K-edge at 1839 eV)

Edge identification can be done three different ways in Gatan Microscopy Suite® (GMS) 3 software.

  1. Use the AutoID function in the Elemental Analysis window of the technique.

AutoIDWhen you select the AutoID button it will show candidate edges on the spectrum. You will need to verify these edges using the common identifiers defined above. To aid in this task the Mark Edges button can be used to show edge families. Once verified, you can then add them to the quantification list by pressing the → button to the left of the list.

  1. Your second option is manual identificationManual Edge ID.

By right clicking on the spectrum itself, you will see the Edge ID menu where candidate edges are shown. The most probable edge will be in bold. You can add that edge to the quantification by using Add to Quant menu choice.

  1. The third option for identification is through the period table interface.

Open Periodic TableTo reach this option, click the Open Periodic Table icon on the Elemental Analysis window. This will in turn open a periodic table where you can directly select known elements to automatically add them to the quantification.

Complex edge identification

Delayed edge features, plural scattering and overlapped edges can sometimes make edge identification difficult. Compare the acquired spectra to reference data (e.g., from the EELS Atlas) if you suspect overlapped edges or see unusual edge shapes. If the element has multiple edges available, confirm the existence of these features in you experimental data for unambiguous identification.

Complex edge identification
Here the B K-edge overlaps strongly with the P L­-edge. Comparisons with a P standard would show the B feature is not present. Small concentrations of B may be hard to extract in this case.

References

Ahn, C. C.; Krivanek, O. L.; Disko. M. M. EELS atlas: a reference collection of electron energy loss spectra covering all stable elements. HREM Facility, Center for Solid State Science, Arizona State University; 1983.