Vogel spiral-based tilt-scan averaging approach for robust and efficient diffraction contrast suppression in DPC...

Area of Science:

• Materials Science
• Physics
• Electron Microscopy

Background:

• Differential Phase Contrast (DPC) Scanning Transmission Electron Microscopy (STEM) is a powerful technique for materials characterization.
• Suppression of diffraction contrast is crucial for accurate phase retrieval in DPC STEM.
• The arrangement of tilt points significantly influences the effectiveness of contrast suppression.

Purpose of the Study:

• To theoretically investigate the impact of tilt point arrangements on diffraction contrast suppression in DPC STEM.
• To compare the effectiveness of different sampling patterns, including concentric and Vogel spiral patterns.
• To identify optimal tilt sampling strategies for robust DPC STEM imaging.

Main Methods:

• Theoretical investigation using multislice simulations.
• Comparison of three tilt point sampling patterns: 4-fold, 6-fold symmetric concentric, and Vogel spiral.
• Simulations performed on GaN, GaAs, Si, and SrTiO3 crystals.

Main Results:

• All patterns converged to similar values with high tilt numbers, but convergence behaviors differed.
• Concentric patterns showed non-monotonic decay and discrete fluctuations in residual diffraction contrast.
• The Vogel spiral pattern demonstrated smoother, monotonic decay across various tilt numbers and crystal symmetries.

Conclusions:

• Rotationally asymmetric and uniformly distributed tilt sampling is advantageous for diffraction contrast suppression in DPC STEM.
• The Vogel spiral pattern is identified as an effective strategy for robust contrast suppression.
• This finding aids in optimizing DPC STEM acquisition for improved phase imaging.