Acene adsorption on a Fibonacci-modulated Cu film

Abstract

The adsorption of pentacene (Pn) on the fivefold surface of an i-Al-Pd-Mn quasicrystal and on a one-dimensionally aperiodic Cu multilayer formed thereon is observed with scanning tunneling microscopy. The molecule has a strong interaction with the clean quasicrystal surface, leading to the formation of a disordered layer. On the Cu film, a molecular layer assembles, with the Cu rows acting as a template. At lower coverages, there is a repulsive interaction between the molecules, leading to a dispersed homogeneous arrangement. At higher coverages, the steric interaction of the Pn molecules counterbalances the aperiodic template, which results in a short-range periodic " checkerboard" arrangement of molecules. Density functional theory calculations using lower order acenes are used to probe the details of the interactions with the aperiodic Cu surface and it is found that adsorption with molecules parallel to Cu rows is preferred, in agreement with experimental results.