Gap-Free Information Transfer in 4D-STEM via Fusion of Complementary Scattering Channels

Area of Science:

• Materials Science
• Electron Microscopy
• Imaging Techniques

Background:

• Linear phase-contrast scanning transmission electron microscopy (STEM) techniques are crucial for imaging beam-sensitive materials but suffer from low-frequency contrast gaps.
• Existing methods to address these gaps often increase experimental complexity, limiting their routine application.
• Dark-field STEM captures missing low-frequency information but is dose-inefficient due to signal loss.

Purpose of the Study:

• Introduce Fused Full-field STEM (FF-STEM), a new 4D-STEM modality.
• Overcome limitations of existing phase-contrast STEM techniques, specifically the contrast gap.
• Achieve high-contrast, dose-efficient imaging of weakly scattering and beam-sensitive materials.

Main Methods:

• FF-STEM combines ptychographic phase reconstruction with tilt-corrected dark-field imaging in a single acquisition.
• Bright-field data are used for probe aberration estimation and phase image reconstruction.
• Dark-field data provide complementary low-frequency contrast, fused with bright-field data in Fourier space using Wiener-band weighting.

Main Results:

• FF-STEM yields transfer-gap-free images with high contrast.
• The modality preserves ptychography's upsampling and depth-sectioning capabilities.
• Achieves robust low-frequency contrast and dose-efficient, near-real-time reconstruction.

Conclusions:

• FF-STEM effectively overcomes the contrast gap in phase-contrast STEM imaging.
• This technique offers a dose-efficient and practical solution for imaging sensitive materials.
• FF-STEM represents a significant advancement in 4D-STEM imaging capabilities.