Regensburg 2010 – scientific programme
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DS: Fachverband Dünne Schichten
DS 4: Organic Electronics and Photovoltaics II (Joint Session DS/CPP/HL/O)
DS 4.3: Talk
Monday, March 22, 2010, 14:30–14:45, H8
Morphology and electronic properties of an electron acceptor adsorbed on organic insulator pre-covered metal surfaces — •P. Amsalem1, J. Frisch1, A. Wilke1, A. Vollmer2, R. Rieger3, K. Müllen3, J.-P. Rabe1, and N. Koch1 — 1Humboldt-Universität zu Berlin, Institut für Physik, Brook-Taylor-Str. 6, 12489 Berlin, Germany — 2HZB-BESSY II, Albert-Einstein-Str. 15, 12489 Berlin, Germany — 3Max Planck Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany
In this work, we explore the possibility of tuning the interface energetics at a pi-conjugated (electron acceptor) molecule-metal interface by modifying the adsorbate-substrate distance through pre-adsorption of insulating organic monolayers. We report a photoemission study of the growth of hexaazatriphenylene-hexacarbonitrale (HATCN) deposited on N,N-bis-(1-naphthyl)-N,N-diphenyl1-1,1-biphenyl1-4,4-diamine(α-NPD) or tris(8-hydroxyquinoline)aluminum (Alq3) pre-covered Ag(111) surfaces. α-NPD and Alq3 are known to be weakly adsorbed on Ag(111) and have both been used as thin organic spacer. The choice of HATCN has been motivated by its high electronic affinity (∼3.5 eV). HATCN molecules deposited on α-NPD/Ag(111) are found to diffuse below the α-NPD molecules pre-adsorbed on Ag(111). In the case of HATCN on Alq3/Ag(111), an interface state close to the Fermi-level is observed. This interface state differs markedly from the one measured for HATCN in direct contact with Ag(111). The results are discussed in terms of the formation of polaronic states and charge transfer across insulating layers.