Dresden 2011 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 49: Metal substrates: Adsorption of organic / bio molecules VI
O 49.2: Vortrag
Mittwoch, 16. März 2011, 15:15–15:30, PHY C213
Charge transfer from a metal to a strong electron acceptor molecule through an organic spacer-layer — •Patrick Amsalem1, Jens Niederhausen1, Johanes Frisch1, Andreas Wilke1, Benjamin Bröker1, Antje Vollmer2, Ralph Rieger3, Klaus Müllen3, Jürgen P Rabe1, and Norbert 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
We investigate the possibility for electrons to tunnel from a metal surface to a strong electron acceptor molecule through an inert organic layer used as spacer. We report photoemission measurements performed on one monolayer (ML) hexaaza-triphenylene-hexacarbonitrile (HATCN) deposited under ultrahigh vacuum conditions on Ag(111) precovered with 1ML tris(8-hydroxyquinoline)aluminium (Alq3). The valence spectra reveal a density of states (DOS) in the vicinity of the Fermi-level which is attributed to the filling of the HATCN lowest unoccupied molecular orbital derived state, resulting from a charge transfer from the Ag(111). Indications that this DOS is located at the very surface are given by the intensity variations of the molecular level valence features as a function of the emission angle. These variations match well with the expected signal attenuation in photoemission, allowing to conclude that the low-energy DOS arises from HATCN molecules located at the very surface. Work function changes are set in relation to the observed charge transfer.