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O: Oberflächenphysik

O 32: Nanostrukturen III

O 32.8: Vortrag

Montag, 7. März 2005, 12:30–12:45, TU EB202

Copper-phthalocyanine/Cu(001) as template for cobalt- nanodots — •C.X. Liu, H. L. Meyerheim, J Barthel, and Jürgen Kirschner — Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle

Preparation of metallic nanostructures require a special template for preferential adsorption. While for this purpose vicinal surfaces or dislocation networks are used quite frequently, large organic molecules deposited on flat substrate surface have only recently attracted interest[1]. Here we show that copper-phthalocyanine (CuPc) molecules deposited on Cu(001) at room temperature can be used to prepare a suitable template for preparing a metallic nanostructure. Depending on the CuPc-coverage we find different CuPc-superstructures. A "relaxed" one at a coverage of one monolayer (i.e. a complete layer of molecules), which we assign to a quadratic (5 3 -3 5) unit-cell in matrix notation, and a "compact" one corresponding to a coverage of about 1.5 monolayers. For the latter, STM indicates the formation of a stripe structure, where the stripes are formed by molecules aligned in columns parallel to the <110> substrate directions. The stripes are up to 100 nm long, their lateral separation (1.3 and 2.6 nm) gives rise to a (10x1) LEED-diffraction pattern. Subsequently deposited Co (≈ 0.3-0.5 ML; 1ML =1.53×10¹⁵atoms/cm²)is found to adsorb in monolayer thick islands (diameter ≈ 5nm) aligned parallel to the stripes keeping the short range ordering intact. Magnetic hysteresis loops are observed in longitudinal geometry above about 0.5 ML at 50K.

[1] X. Ma, et al., Appl. Phys. Lett. 84 (2004) 4038