Molecule-Substrate Hybridization Revealed by Angle-Resolved Photoemission Spectroscopy

Full text: Within the past few years a close relation between the angle-resolved photoemission (ARPES) intensity of oriented molecular films and the spatial distribution of the respective molecular orbital has been demonstrated. So far, experimental ARPES data has been accounted for by neglecting the interaction of molecule with the underlying metal substrates. The remaining, small differences have been tentatively attributed to modifications of the molecular states due to molecule-substrate hybridization. Here, we calculate ARPES intensity maps of the prototypical monolayers PTCDA/Ag(110) and pentacene/Cu(110) by explicitly taking into account molecule substrate interactions within ab-initio density functional calculations. By comparing simulated ARPES maps with experiment, we shed light on the possibility to extract information about molecule-metal hybridization from ARPES experiments and reveal limitations of the plane-wave final state approximation for such molecular films. (author)