Adsorbate–substrate bonding and the growth of naphthalene thin films on Ag(1 1 1)

Abstract

The adsorption kinetics, energetics and growth of naphthalene thin films, from submonolayer to about 10 layers, on a Ag(1 1 1) surface at low temperature in a ultrahigh vacuum chamber are examined by using temperature programmed desorption spectroscopy. The first layer adsorption occurs with a desorption energy of 85 ± 5 kJ/mole and results in an interface dipole of 5 ± 1 D, from charge transfer of approximately 0.2 e from naphthalene to Ag. The surface dipole induced inter-adsorbate repulsion causes the lowering of the adsorption energy within the first layer near the saturation coverage so that the second layer deposition begins before the completion of the first layer. The second layer is a metastable phase with desorption energy, 74 ± 3 kJ/mole, smaller than the multilayer desorption energy of 79 ± 5 kJ/mole. Fractional order desorption kinetics were found for both the metastable and the multilayer phases, suggesting desorption from 2-D islanding and 3-D islanding, respectively.