Berlin 2005 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 30: POSTER: Chemical physics
CPP 30.14: Poster
Dienstag, 8. März 2005, 16:30–18:30, Poster TU D
Theoretical investigation of the reactivity of Mg deposited on PTCDA films — •L. Mancera, R. Scholz, A. Abbasi, M. Schreiber, B.A. Paez, G. Gavrila, G. Salvan, and D.R.T. Zahn — Institut für Physik, Technische Universität Chemnitz, Chemnitz, Germany
In this work, the spectroscopic changes observed upon deposition of Mg on PTCDA films of 15 nm thickness are investigated with different microscopic models for Mg-PTCDA compounds. The Raman spectra obtained on these films reveal pronounced changes of the vibrational fingerprint, indicating the reactive nature of the PTCDA/Mg interface. Some of the new modes observed after Mg deposition can be assigned to modified molecules with magnesium atoms attached to the oxygen atoms in the carboxylic and anhydride groups. In a geometry resembling crystalline PTCDA, the energetically most favourable position for a single Mg atom was found in a bridge position between the oxygen end groups of two adjacent PTCDA molecules. The shift of the 2p core levels of the Mg atoms observed in photoemission spectroscopy results from a significant positive net charge on the Mg atoms, in keeping with the Mulliken charge and core level shift found in the calculation. Due to the delocalized nature of the lowest unoccupied states of neutral PTCDA, the additional negative charge is distributed over the entire molecular area, resulting in relatively small shifts of the O1s and C1s core levels.