High-Resolution and In-Solution Hard X-ray Ptychography at the Ptychographic Nano-Analytical Microscope PtyNAMi

Dissertation, University of Hamburg, 2021; Hamburg : Staats- und Universit��tsbibliothek Hamburg 168 pp. (2021). = Dissertation, University of Hamburg, 2021
X-ray microscopy is characterized by its high spatial resolution, exceeding that ofvisible light microscopy, while also being able to penetrate thick samples and sample enclosures that are inaccessible to electron microscopy. With these characteristics, x-ray microscopy excels in in-situ imaging of nanoscopic sample systems that are highly relevant in fields such as chemistry and life sciences.Ptychography is a lensless, computational microscopy technique in which the objective lens of the microscope is replaced with an algorithm to retrieve the phases of the coherent wave field. With this approach, the spatial resolution achieved in a ptychographic microscope can widely exceed that of the used x-ray focusing optics.One of the limiting factors of current ptychographic microscopes are nanopositioning errors and vibrations. Using laser-interferometry, these factors are studied in this thesis at the Ptychographic Nano-Analytical Microscope (PtyNAMi, P06, PETRA III) with particular attention to the occurring measurement uncertainties. In addition, an ultra-stable setup for two-dimensional measurements, that exhibits isotropic vibrations in the order of 1nm rms, is presented.Further improvement of the instrumentation is achieved by placing the area detector into a windowless and evacuated detector device, thereby suppressing the incoherent scattering background. With both of these instrumentational optimizations, ptychographic imaging with 10nm resolution is demonstrated.A distinct advantage of ptychography is the high degree of overdetermination in the data set that permits extensions of the ptychographic model to describe experimental imperfections. For samples that extent along the optical axis beyond the depth-offield of the microscope, several independent virtual object planes can be modeled, reconstructing all of them from a single measurement.This multi-slice ptychography is required when imaging the synthesis of nanoparticles in solution in cases in which the forming particles adhere to both windows of the in situ cell. Such an in situ cell, that is designed to be compatible with hard x-ray ptychographic imaging, is designed and commissioned.In a first demonstration, the nucleation and growth of copper and copper oxidenanoparticles in heated benzyl alcohol is imaged. For a period of 20 h, the growth of individual nanoparticles was imaged with a spatial resolution of 70nm and a temporal resolution of 22 minutes in two image planes. The observed imaging artifacts are part of an overarching discussion about the disadvantages of multi-slice ptychography.
Published by Staats- und Universit��tsbibliothek Hamburg, Hamburg