Ultrahigh-vacuum third-order spherical aberration (Cs) corrector for a scanning transmission electron microscope

Area of Science:

• Materials Science
• Electron Microscopy
• Physics

Background:

• Spherical aberration (Cs) limits resolution in electron microscopy.
• Developing aberration correctors is crucial for advancing nanoscale imaging.
• Ultrahigh-vacuum (UHV) environments are essential for high-resolution microscopy.

Purpose of the Study:

• To present initial results from a UHV third-order spherical aberration (Cs) corrector.
• To evaluate the performance of a dual hexapole Cs corrector in a dedicated scanning transmission electron microscope (STEM).
• To assess the achieved resolution and explore direct measurement of higher-order aberrations.

Main Methods:

• Installation of a UHV-compatible dual hexapole Cs corrector on a UHV STEM column.
• Acquisition and analysis of Ronchigrams to assess aberration correction.
• Analysis of image power spectra to determine resolution.
• Attempted direct measurement of fifth-order spherical aberration (C5) using Ronchigram fringe analysis.

Main Results:

• Successful correction of third-order spherical aberration (Cs) was indicated by an extended Ronchigram sweet spot.
• A resolution of 0.1 nm was achieved, as demonstrated by the image power spectrum.
• A preliminary direct measurement of fifth-order spherical aberration (C5) was successfully attempted.

Conclusions:

• The UHV Cs corrector effectively corrects third-order spherical aberration, enhancing STEM performance.
• The achieved 0.1 nm resolution represents a significant improvement for nanoscale imaging.
• The study demonstrates the feasibility of directly measuring higher-order spherical aberrations.