Comparison of different imaging models handling partial coherence for aberration-corrected HRTEM at 40-80 kV

Area of Science:

• Materials Science
• Physics
• Electron Microscopy

Background:

• Accurate simulation of high-resolution transmission electron microscopy (HRTEM) images requires accounting for partial coherence of electron waves.
• Existing simulation methods include incoherent summation, transmission cross-coefficient (TCC) model, and quasi-coherent model.

Purpose of the Study:

• To compare the accuracy and computational efficiency of three HRTEM image simulation models.
• To evaluate the suitability of these models for simulating images of high-Z materials, especially with corrected aberrations.

Main Methods:

• Simulated HRTEM images using incoherent summation, TCC model, and quasi-coherent model.
• Compared simulated images with experimental images for Cs-corrected and Cc/Cs-corrected microscopes at 80 kV.
• Assessed model performance for weak phase objects and high-Z materials.

Main Results:

• The quasi-coherent model is computationally efficient and sufficient for weak phase objects.
• For Cs- and Cc/Cs-corrected microscopes, the quasi-coherent model provides sufficient approximation for high-Z materials if chromatic aberration is corrected and samples are thin.
• For Cs-corrected only, incoherent summation or TCC models are necessary for high-Z samples, despite higher computational cost.

Conclusions:

• The quasi-coherent model offers a computationally efficient and sufficiently accurate approach for HRTEM image simulation in advanced, corrected microscopes.
• Model selection depends on the microscope's correction status and the sample's material properties and thickness.