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O: Fachverband Oberflächenphysik

O 44: Metal substrates: Adsorption of organic / bio molecules VI

O 44.4: Vortrag

Donnerstag, 26. März 2009, 11:15–11:30, SCH A118

Nature of Free-Electron-Like States in PTCDA molecules Adsorbed on an Ag(111) Surface — •Mats Persson and Matthew Dyer — Surface Science Research Centre, University of Liverpool, L69 3BX Liverpool, UK

Advances in molecular assembly experiments on metal surfaces and potential applications arising from them call for a better understanding of the electronic structure at the interface of metals and organic systems. There is a high interest in delocalized electronic states, because of their potential use in molecular and opto-electronics applications. Recently, unoccupied, free-electron-like states arising in mono layers of 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) molecules adsorbed on an Ag(111) surface at energies close to the Fermi energy have been observed by scanning tunneling and photoemission spectroscopies [1,2]. So as to reveal the nature of these delocalized states we have carried out a density functional study of the electronic structure and local density of states of these systems. We show that the observed free-electron state originates from a Shockley surface state (SS) at the zone centre of the bare surface. The SS is shifted up by the interaction with the organic overlayer. [1] R. Temirov et al., Nature 444, 350 (2006). [2] C. H. Schwalb et al., Phys. Rev. Lett. 101, 146801 (2008).