Regensburg 2016 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 85: Organic-Inorganic Systems IV: Electronic Structure
O 85.7: Vortrag
Donnerstag, 10. März 2016, 16:45–17:00, S051
Excitation dynamics at the PTCDA/TiOPc heterointerface on Ag(111) — •Alexander Lerch1, Frederik Schiller1,2, and Ulrich Höfer1 — 1Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, D-35032 Marburg — 2Centro de Física de Materiales, San Sebastian, Spain
The charge carrier transport across metal/organic and organic heterointerfaces was investigated by means of time-resolved two-photon photoemission (2PPE). We deposited well defined layers of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) on top of titanylphthalocyanine (TiOPc) on an Ag(111) substrate as model system. An optical parametric oscillator (OPO) provided tuneable pump pulses with photon energies ranging from 1.6 to 2.5 eV. Excitons in PTCDA and TiOPc were excited selectively and the subsequent charge transfer to the metal was monitored by photoemission with 4.3 eV probe pulses. An unoccupied interface state lying 0.3 eV above the Fermi energy arises at the TiOPc/Ag(111) interface. Although a second TiOPc layer is used to form the organic heterostructure and separate the PTCDA from the silver, we observe a resonant enhancement of the interface state for 2.3 eV pump photons, which corresponds to the excitonic HOMO-LUMO transition in PTCDA. We find a time delayed transfer of electrons from PTCDA across the TiOPc layers into the interface state on the time scale of approximately 200 fs. Our results indicate the importance of the interface state for charge carrier dynamics at heterostructures close to the Ag(111) surface.