Berlin 2015 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 96: Ultrafast Electron Dynamics at Surfaces and Interfaces
O 96.6: Vortrag
Freitag, 20. März 2015, 12:00–12:15, MA 004
Ultrafast charge transfer across the 5P-pyridine/ZnO(1010) interface — •Jan-Christoph Deinert1, Clemens Richter1, Lea Bogner1, Yves Garmshausen2, Stefan Hecht2, Martin Wolf1, and Julia Stähler1 — 1Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin — 2Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489 Berlin
The functionality of hybrid inorganic organic systems (HIOS) is governed by the interfacial electronic coupling and the resulting charge transfer (CT) dynamics. To gain direct insight into these dynamics we use femtosecond time-resolved two-photon photoemission (2PPE) to investigate the hybrid system 5P-pyridine on ZnO(1010). The molecules form an ordered layer on the mixed-terminated ZnO surface, accompanied by a strong reduction of the work function by up to 1.8 eV. We optically excite electrons from just below the Fermi level EF at the ZnO surface with 2.5 eV photons, leading to transient formation of a CT state by population of the molecular LUMO (1.7 eV above EF). This CT state is used to observe the pure interfacial electron transfer from the LUMO to the ZnO conduction band, which occurs on an ultrafast timescale of 90 fs. This is in contrast to previous results on interfacial CT processes on ps timescales at ZnO interfaces where photoexcitation is used to create excitons in the organic film. [1] Our results show that the purely electronic coupling at the interface is significantly stronger in the absence of the photohole.
[1] K. R. Siefermann et al., J. Phys. Chem. Lett. 5, 2753–2759 (2014)