Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 14: Poster session I (Adsorption, Epitaxy and growth, Phase transitions, Surface reactions, Organic films, Electronic structure, Methods) (sponsored by Omicron Nanotechnology GmbH)

O 14.49: Poster

Monday, March 27, 2006, 18:00–21:00, P2

Observation of Distinct Topographic/Electronic Features in Cobalt Porphyrin Layers on Silver (111) — •K. Comanici, H. Marbach, F. Maier, F. Buchner, K. Flechtner, T. Lukasczyk, J. M Gottfried, and H.-P. Steinrück — Lehrstuhl für Pysikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstraße 3, D-91058 Erlangen

Metalloporphyrins are of special interest due to their functionality in technological processes and biological molecules like chlorophyll and hemoglobin. The properties of metalloporphyrins can be modified e.g. by changing a central metal atom and different ligands. Keeping or reversibly changing the oxidation state of the involved central metal atom is crucial for the functionality of the porphyrin in natural and technological processes. The approach of this work is to prepare and investigate monolayers of different porphyrins under ultra clean conditions in an ultra high vacuum (UHV) environment. We studied different metalloporphyrins on a silver (111) surface by means of scanning tunneling microscopy (STM) and ultraviolet photoelectron spectroscopy (UPS). Ordered porphyrin layers imaged with sub-molecular resolution were found. A particular interesting feature was observed for two different cobalt porphyrins. A fraction of these Co porphyrins appear as No-dqpitsNo-dq in the STM image. These pits tend to vanish at lower bias voltages. One possible explanation for these features is to interpret them as different oxidation states of the central cobalt atoms.