Bragg Diffraction Imaging : Overcoming Angular Uncertainty

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.