Berlin 2005 – scientific programme

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O: Oberflächenphysik

O 54: Adsorption an Oberfl
ächen VI

O 54.5: Talk

Wednesday, March 9, 2005, 11:45–12:00, TU EB202

Influence of the alkyl-chain length on the electronic structure and interface properties of 1,4-octasubstituted Zinc Phthalocyanine thin films on gold — •Indro Biswas¹, Heiko Peisert¹, Sonja Dick¹, Danilo Dini², Michael Hanack², and Thomas Chassé¹ — ¹Institut für Physikalische und Theoretische Chemie, Universität Tübingen, Auf der Morgenstelle 8, 72076 Tübingen — ²Institut für Organische Chemie, Universität Tübingen, Auf der Morgenstelle 18, 72076 Tübingen

We compare the interface properties of various 1,4,8,11,15,18,22,25-octa-alkyl-substituted zinc phthalocyanines [(But)₈PcZn, (Hep)₈PcZn, (Dec)₈PcZn] with those of unsubstituted zinc phthalocyanine (PcZn) on gold using X-ray photoemission spectroscopy (XPS) and valence band ultraviolet photoemission spectroscopy (UPS). Although the separation between the aromatic cores in the evaporated thin films clearly depends on the alkyl chain length, it is found that the nature of the substituents causes only minor changes of electronic properties, such as optical gap and ionization potential. It is shown that the observed small energetic shifts for film thicknesses larger than the molecule size cannot be understood in terms of a band bending-like mechanism. Influences of a different orientation of the molecules at the interface and in thin films are discussed. We are grateful for helpful discussions and the synthesis of organic materials to M. Cook and I. Chambrier.