|
The self organization of pentacene can be driven by the large structural anisotropy of suitable metal substrates. We investigated the pentacene film morphology and electronic properties on the Cu(119) surface, where pentacene forms long-range ordered hybrid interfaces [1], characterized by peculiar interface electronic states [2,3]. We performed scanning tunnelling microscopy/spectroscopy (STM/S), core level photoemission (XPS), low energy electron diffraction (LEED) and angle resolved photoemission (ARPES) with polarized synchrotron radiation on in situ deposited pentacene films with thickness ranging from sub-monolayer (< 0.3 nm) to 2 ML. The pentacene molecules are adsorbed in a flat-lying configuration, with the molecular axis parallel to the step edges of Cu(119), as shown by STM images for all thicknesses. We could resolve the internal molecular structure by STM by adjusting the bias voltage. We identify the character of the HOMO or LUMO states for each coverage, by comparing the measured distribution by STM and ARPES with the intrinsic electronic structure of free pentacene molecules [4]. The perturbations of the HOMO/LUMO electronic state due to the substrate/neighbouring molecules are discussed.
[1]L.Gavioli et al, Phys. Rev. B 72, 035458 (2005)
[2]C. Baldacchini et al, Jour. Chem. Phys. 124, 1(2006)
[3]C. Baldacchini et al, Surf. Science 566-568, 613(2004)
[4]J. Repp et al, Phys. Rev. Let. 94, 26803 (2005)
|