Au(110) induced reconstruction by π conjugated molecules adsorption investigated by photoemission spectroscopy and low energy electron diffraction

We present a comparative investigation of the adsorption mechanism of two organic molecules characterized by pi-delocalized orbitals (copper-phthalocyanine and pentacene) deposited on the Au(110)-(1 x 2) surface, studied by means of low energy electron diffraction (LEED) and high energy-resolution ultraviolet photoemission spectroscopy (HR-UPS). The molecular adsorption induces a threefold periodicity in the [001] direction and a x5 (x6) symmetry in the [1 (1) over bar0] direction for the phthalocyanine (pentacene), as deduced by the LEED patterns. High energy-resolution photoemission spectra show similar hybrid interface states for both systems, indicating that the molecular interaction with the metal substrate is driven mainly by pi molecular orbitals (even for the phthalocyanine). Comparing the electronic spectral density excited by different photon energies we single out the different contribution of pi and d symmetry to interface states. (C) 2004 Elsevier B.V. All rights reserved.