Imaging extended single crystal lattice distortion fields with multi-peak Bragg ptychography

Area of Science:

• Materials Science
• Crystallography
• X-ray Imaging

Background:

• Phase-retrieval X-ray imaging can reconstruct 3D distortion fields in nanocrystals using Bragg reflections.
• Existing methods struggle with phase wrapping in crystals with high defect densities.
• Current techniques are limited to isolated crystals smaller than the X-ray beam.

Purpose of the Study:

• To develop an advanced X-ray imaging method capable of reconstructing lattice distortions and defects in extended crystals.
• To overcome limitations of phase wrapping and sample size in current phase-retrieval techniques.

Main Methods:

• Introduced multi-peak Bragg ptychography, an optimization framework combining stochastic gradient descent and phase unwrapping.
• Utilized modern automatic differentiation toolsets for method extensibility and high-performance computing implementation.
• Applied to extended crystals, addressing challenges of phase wrapping and larger sample sizes.

Main Results:

• Successfully reconstructed 3D lattice distortions and defects in extended crystals.
• Demonstrated robustness in image reconstruction despite significant defect content and phase wrapping.
• The method is adaptable for various settings and compatible with high-performance computing.

Conclusions:

• Multi-peak Bragg ptychography overcomes key limitations of previous X-ray imaging methods for lattice distortion analysis.
• This technique enables detailed defect imaging in extended crystalline materials.
• The advancement is timely for leveraging fourth-generation synchrotron sources for materials research.