Chemisorption of Pentacene on Pt(111) with a Little Molecular Distortion

We investigated the adsorption of pentacene on the (111) surface of platinum, which is an archetypal system for a junction with a low charge-injection barrier. We probed the structural and electronic configurations of pentacene by scanning tunnelling mi- croscopy (STM), X-ray photoemission spectroscopy (XPS) and near-edge X-ray absorp- tion fine structure (NEXAFS) spectroscopy measurements. We simulated the interface by means of ab initio methods based on the density functional theory (DFT) frame- work, while including the dispersion forces. We found that the molecules adsorb at the bridge site of the close-compact atom rows with the long axis parallel to the substrate’s directions, in a slightly distorted geometry, driven by the good match between the position of carbon atoms of the molecule and the underlying lattice of the surface. Most importantly, a chemical bond is formed at the interface which we attribute to the high chemical reactivity of the Pt substrate