Huaiyu Chen
Profile area member
Bragg Diffraction Imaging : Overcoming Angular Uncertainty
Author
Summary, in English
Probing the internal structure of crystalline materials is vital for understanding and optimizing their functional properties, especially in semiconductors and multiferroics, where nanoscale distortions such as strain and lattice tilt can dramatically affect performance. Among various characterization tools, X-ray diffraction imaging offers a unique combination of deep penetration, nondestructive measurement, and high strain sensitivity.
This thesis focuses on Bragg Cohereht Diffraction Imaging (BCDI), a powerful technique that reconstructs three-dimensional internal displacement fields in crystals from coherent X-ray diffraction patterns. While BCDI offers high-resolution structural information, its practical implementation faces a critical challenge: angular instability during data acquisition, which can lead to severe distortions and artifacts in the reconstruction. Addressing this limitation forms the central theme of this work.
A robust angular correction algorithm is developed to mitigate for such distortions, and its effectiveness is demonstrated in experimental studies, including BCDI measurements on heterostructured nanowires. To further relax the stringent sampling requirements of BCDI, a deep learning–based strategy is introduced that enables diffraction volume reconstruction from completely unordered and angularly distorted datasets. Together, these methods aim to enhace the robustness of BCDI and make it more adaptable to complex, dynamic, or extreme experimental conditions.
In addition, scanning X-ray diffraction (nano-XRD) is employed to map local strain and lattice tilt in extended crystalline materials, such as ferroelectric thin films and nanowires. Nano-XRD serves as a practical probe of the internal structure of the extended sample.
Overall, this thesis demonstrates the potential of synchrotron-based X-ray diffraction imgaging tehnique for revealing internal crystalline structures, offering valuable tools for both fundamental research and advanced technological development.
This thesis focuses on Bragg Cohereht Diffraction Imaging (BCDI), a powerful technique that reconstructs three-dimensional internal displacement fields in crystals from coherent X-ray diffraction patterns. While BCDI offers high-resolution structural information, its practical implementation faces a critical challenge: angular instability during data acquisition, which can lead to severe distortions and artifacts in the reconstruction. Addressing this limitation forms the central theme of this work.
A robust angular correction algorithm is developed to mitigate for such distortions, and its effectiveness is demonstrated in experimental studies, including BCDI measurements on heterostructured nanowires. To further relax the stringent sampling requirements of BCDI, a deep learning–based strategy is introduced that enables diffraction volume reconstruction from completely unordered and angularly distorted datasets. Together, these methods aim to enhace the robustness of BCDI and make it more adaptable to complex, dynamic, or extreme experimental conditions.
In addition, scanning X-ray diffraction (nano-XRD) is employed to map local strain and lattice tilt in extended crystalline materials, such as ferroelectric thin films and nanowires. Nano-XRD serves as a practical probe of the internal structure of the extended sample.
Overall, this thesis demonstrates the potential of synchrotron-based X-ray diffraction imgaging tehnique for revealing internal crystalline structures, offering valuable tools for both fundamental research and advanced technological development.
Department/s
- Synchrotron Radiation Research
- NanoLund: Centre for Nanoscience
- eSSENCE: The e-Science Collaboration
- LTH Profile Area: Nanoscience and Semiconductor Technology
- LU Profile Area: Light and Materials
Publishing year
2025
Language
English
Full text
- Available as PDF - 10 MB
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Document type
Dissertation
Publisher
Lund University
Topic
- Condensed Matter Physics (including Material Physics, Nano Physics)
- Atom and Molecular Physics and Optics
Keywords
- Coherent Diffraction Imaging
- X-ray Diffraction
- Nanowires
- Strain Mapping
- MAX IV
Status
Published
Project
- eSSENCE@LU 8:2 - Coherent 3D X-ray imaging of nanoparticles with unknown orientation
Supervisor
- Jesper Wallentin
- Pablo Villanueva Perez
- Megan Landberg
ISBN/ISSN/Other
- ISBN: ISBN 978-91-8104-620-5
- ISBN: ISSN 978-91-8104-621-2
Defence date
19 September 2025
Defence time
09:15
Defence place
Rydbergsalen
Opponent
- Tobias Schülli (Dr.)