Accuracy and precision of thickness determination from position-averaged convergent beam electron diffraction...

Area of Science:

• Materials Science
• Electron Microscopy
• Crystallography

Background:

• Convergent beam electron diffraction (CBED) patterns are crucial for materials analysis.
• Visual comparison of experimental and simulated CBED patterns is a common method for determining sample thickness.
• This method is effective but can be subjective and time-consuming.

Purpose of the Study:

• To develop and evaluate an automated method for sample thickness determination using CBED.
• To assess the accuracy and precision of the automated method.
• To investigate factors influencing the precision of thickness determination.

Main Methods:

• Position-averaged convergent beam electron diffraction patterns were generated by scanning an electron probe across a sample.
• A sum of square differences metric was employed to automate the comparison between experimental and simulated patterns.
• The accuracy and precision of the automated thickness determination were analyzed.

Main Results:

• The automated method demonstrated accurate sample thickness determination, with deduced thicknesses generally agreeing with true values.
• Factors such as experimental noise, sample mistilt, and inelastic scattering were found to reduce the precision of the measurements.
• Higher precision in thickness determination was observed with smaller probe-forming aperture angles.

Conclusions:

• Automated analysis of CBED patterns using a sum of square differences metric offers an accurate approach to sample thickness determination.
• While accurate, the precision is influenced by experimental conditions and sample characteristics.
• Optimizing aperture angles can lead to more precise thickness measurements in electron microscopy.