Precise measurement of third-order spherical aberration using low-order zone-axis Ronchigrams

Area of Science:

• Materials Science
• Electron Microscopy
• Crystallography

Background:

• Accurate measurement of electron-optical aberrations is crucial for high-resolution electron microscopy.
• Third-order spherical aberration (C(s)) significantly impacts image quality and resolution.
• Existing methods for measuring C(s) often lack sufficient precision.

Purpose of the Study:

• To propose a novel, high-precision method for measuring third-order spherical aberration coefficients (C(s)).
• To validate the proposed method using both simulated and experimental data.
• To present a complementary technique for defocus estimation.

Main Methods:

• Utilizing low-order zone-axis Ronchigrams of crystalline materials.
• Acquiring Ronchigrams with diverse probe-forming lens configurations.
• Comparing results with the established power spectrum-analysis method.

Main Results:

• The proposed method successfully measures C(s) with significantly enhanced precision.
• Validation confirmed the method's accuracy across various experimental conditions.
• Defocus values can also be estimated with reasonable accuracy.

Conclusions:

• The new Ronchigram-based method provides a more precise determination of C(s) in electron microscopy.
• This advancement has the potential to improve the performance of electron optical systems.
• The technique offers a practical alternative for aberration coefficient measurement.