Measuring the absolute position of EELS ionisation edges in a TEM

Area of Science:

• Materials Science
• Analytical Chemistry
• Physics

Background:

• Electron energy loss spectroscopy (EELS) in transmission electron microscopy (TEM) is crucial for materials analysis.
• Primary electron energy instabilities in TEM cause significant errors in core-loss edge position measurements.
• Accurate measurement of chemical shifts, reflecting changes in valency or chemical environment, is often desired.

Purpose of the Study:

• To develop a method to overcome primary electron energy instabilities in TEM EELS.
• To enable precise measurements of absolute positions of EELS core-loss edges.
• To facilitate accurate determination of chemical shifts in materials.

Main Methods:

• Acquiring a series of short low-loss spectra immediately followed by core-loss spectra.
• Implementing computer-controlled operations to minimize time lapse between acquisitions.
• Accumulating and summing spectra, corrected for energy drift, to cancel instabilities.
• Presenting a practical algorithm and necessary calibrations for the procedure.

Main Results:

• The developed method effectively cancels energy instabilities in TEM EELS.
• Accurate measurement of core-loss EELS spectra on an absolute energy scale is achieved.
• Demonstrated successful measurement of chemical shifts in several metal oxides using the new technique.

Conclusions:

• The presented computer-controlled EELS acquisition strategy significantly improves measurement accuracy.
• This method provides a reliable approach for studying chemical shifts in materials.
• The technique is applicable to various materials, including metal oxides, for detailed chemical state analysis.