Berlin 2012 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

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

DS 30.4: Vortrag

Donnerstag, 29. März 2012, 10:15–10:30, H 0111

Quantification of LEED measurements. II. Application to epitaxial organic films — •Matthias Meissner, Falko Sojka, 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.

Based on LEED images corrected for their distortion and calibrated by means of a Si(111)-7x7 diffraction pattern (cf. talk by Falko Sojka), a home-made algorithm finds the LEED spots belonging to a certain structure and fits a lattice to all those spots simultaneously. This provides us with absolute lattice parameters within a small error margin. Additionally, in the case of organic-inorganic epitaxy, measurements at higher energies can be used to relate the adsorbate lattice to the substrate lattice and derive the epitaxy matrix. The precision of this procedure will be evaluated on the basis of two systems: (a) 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) on epitaxial graphene, featuring two different PTCDA phases, one known, the other not; (b) Tin-phthalocyanine (SnPc) on Au(111), not being described in literature yet.