Regensburg 2007 – scientific programme

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O: Fachverband Oberflächenphysik

O 52: Methods: Atomic and Electronic Structure II

O 52.6: Talk

Thursday, March 29, 2007, 12:30–12:45, H42

Verification of Phase Retrieval Parameters by coherent Measurement itself — •T. Panzner¹, T. Sant¹, G. Gleber¹, I. Vartanyants², and U. Pietsch¹ — ¹Festkörperphysik, Institut für Physik, Universität Siegen, Germany — ²Hasylab-DESY , Hamburg

Monochromatic scattering experiments using a coherent x-ray beam have shown the great potential to get access to atomic resolved results without special preparation of the sample. The big disadvantage of all scattering experiments is the loss of phase information of the scattered signal. Therefore, so called ``phase retrieval'' procedures are needed to restore the wanted information from the measured intensities. The quality of these procedures strongly depends on additional information about the illuminated area. This information can be given by the size of the illuminated area (``over sampling'' [1]) or the illumination function itself (i.e. approximation by Fermi-integrals [2]). In our case (energy-dispersive set-up) we have shown, that the illumination function is well determined by the aperture (pinhole) being equipped in front of the sample. A simple FFT of a measured intensity map is sufficient to reproduce the calculated intensity distribution. The deviation of the reconstructed illumination function from the calculated one, represents the influence of the specimen to the scattering intensity. In case of a reflectivity experiment this information concerns the roughness of surface. Our future work is concentrated on these variations to improve the quality of the phase retrial procedure. [1] J. Miao et al, Phys. Rev. B 67, 174104 [2] I.A. Vartanyants et al, Phys. Rev. B 55, 13193