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O: Fachverband Oberflächenphysik
O 29: Nanostructures at surfaces: preparation
O 29.1: Vortrag
Mittwoch, 25. März 2009, 10:30–10:45, SCH A01
Formation of Nanostructures by Bimodal Growth of a Low Symmetry Magnetic Molecule on a Weakly Interacting Substrate — Sweetlana Fremy1, •Alexander Schwarz1, Knud Lämmle1, Roland Wiesendanger1, and Marc Prosenc2 — 1Universität Hamburg, Department Physik, IAP, Jungiusstr. 11, 20355 Hamburg — 2Universität Hamburg, Department Chemie, IAAC, Martin-Luther-King Platz 6, 20146 Hamburg
We are interested in the properties of nanostructures formed by magnetic molecules. In this non-contact atomic force microscopy (NC-AFM) investigation we study the growth of Co-Salen, a planar Schiff-Base complex with Co as magnetic center, on NaCl(001). On this large band gap insulator we expect a rather weak coupling between molecule and surface. Apart from step decoration, we find nanowires, which form networks at higher coverages, and compact nanocrystallites. Molecular resolution on nanowires and nanocrystallites indicate that in both cases the molecules are arranged in the monoclinic bulk unit cell, which consists of 8 Co-Salen dimers. For the nanowires (nanocrystallites) the c-axis is oriented parallel (perpendicular) to the surface normal. From NC-AFM images recorded at 8 K after evaporating small quantities of molecules onto a cold substrate (T < 30 K), we know that the molecules initially adsorb as monomers. Hence, a transition from monomers to dimers must take place before the nanowires and nanocrystallites start to grow. In this presentation, the origin of the bimodal growth, the stability of nanowires and nanocrystallites as well as a model how and where the monomer-to-dimer transition takes place will be discussed.