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KR: Fachgruppe Kristallographie

KR 3: Symposium Crystallography in Materials Science

KR 3.2: Hauptvortrag

Montag, 31. März 2014, 15:30–16:00, HSZ 02

X-Ray Microscopy with Coherent Radiation: Beyond the Spatial Resolution of Conventional X-Ray Microscopy — •Christian G. Schroer — Institut für Strukturphysik, Technische Universität Dresden, 01062 Dresden, Germany

Hard x-ray microscopy has greatly benefited from the high brilliance of modern synchrotron radiation sources and x-ray free-electron lasers (XFELs). Today, the spatial resolution of conventional x-ray microscopes is limited by the x-ray optics to a few tens of nanometers. Scanning coherent diffraction microscopy, also known as ptychography, can overcome this limitation. In ptychography, the sample is scanned through a confined coherent beam, recording at each location of the scan a far-field diffraction pattern. From these data, the complex transmission function (projected complex refractive index) of the sample and the illuminating complex wave field can be reconstructed with a spatial resolution that clearly exceeds the lateral size of the illuminating beam. The spatial resolution in a ptychogram is shown to depend on the shape (structure factor) of a feature and can vary for different features in the object. In addition, the resolution and contrast depend on the coherent fluence on the sample. For an optimal ptychographic x-ray microscope, this implies a source with highest possible brilliance and an x-ray optic with a large numerical aperture to generate the optimal probe beam. Ptychography closes the gap between real space imaging and reciprocal space structure determination and merges these two fields.

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