Interface formation and growth of a thin film of ZnPcCl8/Ag(111) studied by photoelectron spectroscopy

We have investigated the electronic properties of a thin film of ZnPcCl8 molecules deposited on Ag(1 1 1) using ultra-violet photoelectron spectroscopy. Close to one monolayer the electronic structure differs sensibly from that of the thick film. The appearance of a density of states close to the Fermi level is interpreted as the sign of the molecule-substrate interaction via a charge transfer mechanism. An increase of the work function at the early stages of adsorption confirms that electrons are transferred from the metal to the molecular orbitals creating an interface dipole. As the coverage is increased the weak interaction between molecules of successive layers causes the electronic properties to evolve gradually towards those of the thick film. Finally, the impact of the interface electronic properties on the intermolecular interaction is discussed. (C) 2007 Elsevier B.V. All rights reserved.