Automatic and Quantitative Measurement of Spectrometer Aberrations.

Area of Science:

• Electron Microscopy
• Spectroscopy
• Materials Science

Background:

• Electron optical aberrations limit the performance of electron energy loss spectrometers.
• Recent advancements in high-resolution and momentum-resolved EELS necessitate spectrometer optimization.
• Automated alignment is needed for complex EELS techniques, such as the 'ω - q' mode.

Purpose of the Study:

• To develop and demonstrate a method for automatic and quantitative measurement of spectrometer aberrations and distortions.
• To validate the measurement technique through wave mechanical simulations.
• To guide future developments in aberration measurement and correction for EELS spectrometers.

Main Methods:

• Demonstrated measurement of geometric aberrations and distortions in EELS within a monochromated scanning transmission electron microscope (STEM).
• Developed wave mechanical simulations incorporating measured aberration and distortion coefficients.
• Compared simulation results with experimental data to verify formulae and assess measurement accuracy.

Main Results:

• Successfully measured geometric aberrations and distortions in the EELS spectrometer.
• Achieved good agreement between experimental results and wave mechanical simulations when using measured aberration coefficients.
• Verified the accuracy of the simulation formulae and established a basis for assessing measurement precision.

Conclusions:

• The developed method provides a quantitative approach to measuring EELS spectrometer aberrations.
• Verified simulations enhance the understanding and accuracy assessment of aberration measurements.
• This work paves the way for automated alignment and improved performance of advanced EELS techniques.