Au(1 1 0) 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 π-delocalized orbitals (copper-phthalocyanine and pentacene) deposited on the Au(1 1 0)-(1 × 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 [0 0 1] direction and a ×5 (×6) symmetry in the [1 1̄ 0] 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 π molecular orbitals (even for the phthalocyanine). Comparing the electronic spectral density excited by different photon energies we single out the different contribution of π and d symmetry to interface states.