Regensburg 2010 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 27: CE: Poster Session
TT 27.31: Poster
Mittwoch, 24. März 2010, 14:00–18:00, Poster D1
Doping dependent behaviour of potassium intercalated pentacene films: watching out for correlation effects — •Andreas Ruff1, Joep Loos1, Michael Sing1, Jens Pflaum2, and Ralph Claessen1 — 1Experimentelle Physik 4, Universität Würzburg — 2Experimentelle Physik 6, Universität Würzburg
Recently, evidence for a band-filling controlled Mott metal-insulator transition (MIT) was reported for strongly potassium (K) doped pentacene (PEN) films on silicon substrates by conductivity measurements [1]. We have investigated the system KxPEN on silicon with different orientations by means of photoelectron spectroscopy to follow the evolution of the spectral function with doping. The high quality of our PEN films is demonstrated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED) measurements. In the ultraviolet photoemission spectra (UPS) one can observe the gradual filling of the former lowest unoccupied molecular orbital (LUMO) with K evaporation time. Additionally, conductivity measurements have been carried out to observe the MIT. To clarify the growth mode of the films images of the surface were taken with an atomic force microscope (AFM). Despite the drastic change in conductivity, no spectroscopical evidence neither for the metallic regime nor for the Mott transition has been observed as yet.
[1] M.F. Craciun et al, PRB 79, 125116 (2009)