3D Bragg x-ray ptychography: a new microscopy for strain imaging
Speaker: Virginie Chamard (Institut Fresnel, CNRS, Aix-Marseille University, FST Saint Jérôme, Marseille, France)
Date: 22 March 2012, 11:00
Location: AER19, 4.14
Hard X-ray lens-less microscopy holds the promise of a resolution power meeting the need of nanoscience, owing to the possibility of circumventing the limits of state-of-the-art X-ray lenses. Beyond the resolution issue, the complex-valued wavefield is imaged, ensuring truly quantitative information on the sample scattering contrast. Furthermore, combining this approach to the Bragg geometry allows providing nano-resolved images of defects and strains in crystals, in a non-destructive manner.
This X-ray microscopy concept makes use of far-field coherent intensity patterns produced by third generation synchrotron sources. Instead of lenses, numerical tools are employed to retrieve the exit-field at the sample position. As an introduction, we will describe the capabilities and actual limits achieved in the differently proposed lens-less microscopy techniques dedicated to crystal imaging. The new perspectives offered by the ptychography method will be further detailed. It allows the retrieval of the 3D sample scattering contrast with a nanoscale resolution and over a -possibly- infinite field of view. Our recent successful developments of X-ray Bragg ptychography will be illustrated by numerical and experimental results.
The accurate and detailed knowledge of the crystalline structures at the nanoscale is highly desirable for its potential to bring new insights and understandings in a large variety of nanoscience material problems: this challenge is expected to be met by X-ray Bragg ptychography.
This work is funded by the French ANR (ANR-08-JCJC-0095-01).
Keywords: nano-crystals, lens-less microscopy, coherent X-ray diffraction