Dresden 2011 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 64: Organic Thin Films III
DS 64.1: Vortrag
Freitag, 18. März 2011, 14:00–14:15, GER 38
Alkali metal-intercalated Picene thin films: Examination of the electronic structure by photoemission spectroscopy — •Andreas Ruff1, Andreas Müller1, Nis Hauke Hansen2, Jens Pflaum2, Michael Sing1, and Ralph Claessen1 — 1Lehrstuhl für Experimentelle Physik 4, Physikalisches Institut, Universität Würzburg — 2Lehrstuhl für Experimentelle Physik 6, Physikalisches Institut, Universität Würzburg
Recently, superconductivity was reported for potassium-doped picene single crystals (K3Pic) from magnetization measurements [1]. We have investigated AxPic thin films (A=K, Cs) on silicon oxide substrates by means of photoemission spectroscopy (PES) to follow the evolution of the spectral function with doping. The high quality of our Pic films is demonstrated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). To clarify the growth mode of the films, surface images were taken with an atomic force microscope (AFM). In the PES spectra one can observe the gradual filling of the former lowest unoccupied molecular orbital (LUMO) with alkali metal evaporation time. As opposed to previous experiments on K-doped pentacene films, a two-peak structure, instead of one, appears in the former gap of the organic semiconductor. The origin of these features has not been unraveled as yet. We discuss these findings as well as the absence of a clear metallic Fermi cut-off against the background of experimental and theoretical work so far.
[1] R. Mitsuhashi et al., Nature 464, 76 (2010)