Regensburg 2010 – scientific programme

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O: Fachverband Oberflächenphysik

O 37: Metal substrates: Adsorption of organic / bio molecules IV

O 37.4: Talk

Tuesday, March 23, 2010, 15:45–16:00, H36

Island decay studies of PTCDA on Ag(100) — •Julian Ikonomov, Christoph H. Schmitz, and Moritz Sokolowski — Institut für Physikalische und Theoretische Chemie, Universität Bonn, Germany

We have studied two-dimensional islands of perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA) deposited on the Ag(100) surface. For submonolayers, the attractive interactions between the molecules lead to two-dimensional islands with a quadratic equilibrium shape. The ordered PTCDA islands are surrounded by a disordered two-dimensional gas-like phase, consisting of highly mobile molecules [1]. The island ripening and decay were investigated with scanning tunneling microscopy (STM) at room temperature. The decay curves follow the classical continuum model for time evolution of clusters (Ostwald theory). The island area changes with a power low t^α with an exponent α of about 2/3 which clearly reveals that the decay of the PTCDA islands is diffusion limited. For an ensemble of more closely to each other located PTCDA islands, a mass transport from the smaller to the larger islands has been observed. We have performed numerical simulations of the decay curves of the islands in this ensemble and obtained values for relevant parameters, e.g., the step line tension of the PTCDA islands, the attachment-detachment rate, and the equilibrium density of the two-dimensional gas-phase.

Funded by DFG through SFB 624

[1] J. Ikonomov, O. Bauer, and M. Sokolowski, Surface Science 602, 2061 (2008).