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DS: Fachverband Dünne Schichten

DS 30: Thin film characterization: structure analysis and composition (TEM, LEED, PAS)

DS 30.3: Vortrag

Donnerstag, 29. März 2012, 10:00–10:15, H 0111

Quantification of LEED measurements. I. Systematic Errors — •Falko Sojka, Matthias Meissner, Marco Gruenewald, Roman Forker, and Torsten Fritz — University of Jena, Institute of Solid State Physics, Max-Wien-Platz 1, 07743 Jena, Germany

Low energy electron diffraction (LEED) on epitaxial layers is a powerful tool to examine long-range ordering at the interface. However, due to limitations like distortion of the LEED images, often additional efforts have to be made in order to derive precise epitaxial relations.

We developed and implemented an algorithm to determine and correct systematic distortions in LEED-images. The procedure is independent of the design of the device (MCP-LEED vs. conventional LEED). Therefore, only a calibration sample with a well-known structure and a suitably high number of diffraction spots, i.e. Si(111)-7x7, is required. The algorithm provides a correction matrix which can be used to rectify all further measurements generated with the same device. In detail, we distinguish between a radial and an asymmetric distortion. Additionally, we found an axial distortion which occurs due to a tilted sample surface during the measurement. We will show that this axial distortion can be described theoretically with the Ewald Construction, and that it is thus possible to correct those measurements, too. After all, a relative accuracy of the lattice parameter determination better than 1 % can be achieved.