The experimental electron mean-free-path in Si under typical (S)TEM conditions

Area of Science:

• Materials Science
• Solid State Physics
• Electron Microscopy

Background:

• Accurate determination of electron mean-free-path (EMFP) is crucial for quantitative analysis in electron microscopy.
• Existing models for EMFP in silicon (Si) may lead to inaccuracies in sample thickness measurements.

Purpose of the Study:

• To accurately measure the electron mean-free-path in silicon using EELS.
• To compare experimental results with theoretical models and assess their predictive capabilities.
• To evaluate the impact of EMFP accuracy on TEM sample thickness determination.

Main Methods:

• Electron Energy Loss Spectroscopy (EELS) was employed to measure EMFP in Si.
• A certified test structure with known dimensions served as a calibration standard.
• Measurements were performed for primary electron energies of 200 keV and 300 keV at large collection angles.

Main Results:

• The measured EMFP in Si was 150 nm for 200 keV and 179 nm for 300 keV electrons.
• Experimental values closely matched predictions from the Iakoubovskii et al. model.
• The Malis et al. model, commonly used in microscopy software, underestimated EMFP by at least 15%.

Conclusions:

• The study provides accurate EMFP values for silicon, essential for quantitative EELS.
• The Iakoubovskii et al. model demonstrates superior accuracy compared to the Malis et al. model.
• Previous TEM studies on Si-based materials may have underestimated sample thicknesses due to inaccurate EMFP values.