Burdet, NGG; (2017) X-ray Bragg Projection Ptychography for nano-materials. Doctoral thesis , UCL (University College London).

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Abstract

Progress in nanotechnology critically relies on high resolution probing tools, and X-ray coherent diffraction imaging (CDI) is certainly an attractive method for exploring science at such small scales. Thus, the aim of this PhD is to study structural properties of nano-materials using X-ray CDI, with a special motivation to combine Bragg CDI with ptychography. The former has ability to retrieve the complex density and strain maps of nano-meso crystalline objects, and the latter uses translational diversity to produce quantitative maps of the complex transmission function of non-crystalline objects. As both techniques promote highly sensitive phase-contrast properties, the thesis exploits their agreement to reveal the morphology of domain structures in metallic thin films. Additionally, it is demonstrated that Bragg-ptychography is an evolutionary improvement to probe the structure of ’highly’ strained crystals, with respect to its Bragg-CDI counterpart. However, the adaptation of ptychography to the Bragg geometry is not without difficulties and comes with more experimental cost. Therefore, the effects of experimental uncertainties, e.g., scan positions undetermination, partial coherence, and time-varying probes are assessed throughout the thesis and corrected for by implementation of suitable refinement methods. Furthermore, it is shown how the set-up at beamline 34-ID-C at the Advanced Photon Source, used for the experimental measurements can be optimized for better ptychographical reconstructions.

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