Felisa Berenguer, du synchrotron SOLEIL, donnera le 2 février à 11h00 dans la salle 101 barre 32-42 – 1er étage, un séminaire intitulé :
3D Imaging of materials in the nanometer scale using Coherent X-ray Diffraction
Résumé
Imaging objects of several tens of microns in thickness with high resolution (nanometers scale) in three dimensions is a challenging task. The penetration depth of x-rays in matter makes this radiation the perfect candidate for imaging such objects. The development of X-ray microscopy in synchrotrons during the last years has been very promising ; however, the resolution remains limited by the x-ray lenses used during the data acquisition. An alternative (and somehow complementary) approach is Coherent x-ray Diffraction Imaging, a lensless method for imaging materials on the nanometer length scale by exploiting the high coherence flux of synchrotron sources. When using this approach, a finite coherent illumination is used to record diffraction patterns in the far field from the sample, and iterative phase retrieval algorithms are used to retrieve the 3D complex wave field past the specimen. The retrieved wave field carries quantitative information about the density and structure of the object, and 3D images can be obtained with a resolution of a few tens of nanometers and higher sensitivity to the material density than conventional x-ray microscopy. Additionally, in the case of ordered materials, the reconstructed images are also sensitive to the presence of strain, lattice defects and domains structures. In this talk, I will present these methods, together with some applications (particularly in material science) and their latest developments.
