Contrast transfer and resolution limits for sub-angstrom high-resolution transmission electron microscopy

Area of Science:

• Microscopy and Imaging Science
• Materials Science
• Physics

Background:

• Sub-angstrom imaging necessitates meticulous control of high-resolution instrument aberrations.
• Lens aberrations, particularly up to the fifth order, significantly impact imaging fidelity.

Purpose of the Study:

• To determine optimal aberration coefficients for achieving strong phase contrast up to the information limit.
• To investigate the influence of object thickness on defocus aberration correction for improved image simulation.
• To establish the achievable structure resolution limits for sub-angstrom instruments.

Main Methods:

• Least-squares optimization applied to defocus aberration (C1), third-order spherical aberration (C3), and fifth-order spherical aberration (C5).
• Development of two sets of aberration coefficients for variable C1/C3 (fixed C5) and variable C1/C3/C5.
• Simulation study using a double-column model to evaluate structure resolution.

Main Results:

• Two sets of optimal aberration coefficients were identified for strong phase contrast.
• An object-thickness-dependent defocus correction was proposed for enhanced image simulation.
• Simulations predicted structure resolutions between 0.070 nm and 0.059 nm for a 300-kV instrument with a 0.050 nm information limit.

Conclusions:

• Precise adjustment of lens aberrations up to fifth order is critical for sub-angstrom imaging.
• The proposed defocus correction improves contrast prediction for thin objects.
• Ultimate structure resolution is influenced by both instrumental and object properties, with potential for sub-0.06 nm resolution.