Influence of steps on the tilting and adsorption dynamics of ordered Pn films on vicinal Ag(111) surfaces

Here we present a structural study of pentacene (Pn) thin films on vicinal Ag(111) surfaces by He atom diffraction measurements and density functional theory (DFT) calculations supplemented with van der Waals (vdW) interactions. Our He atom diffraction results suggest initial adsorption at the step edges evidenced by initial slow specular reflection intensity decay rate as a function of Pn deposition time. In parallel with the experimental findings, our DFT+vdW calculations predict the step edges as the most stable adsorption site on the surface. An isolated molecule adsorbs as tilted on the step edge with a binding energy of 1.4 eV. In addition, a complete monolayer (ML) with pentacenes flat on the terraces and tilted only at the step edges is found to be more stable than one with all lying flat or tilted molecules, which in turn influences multilayers. Hence our results suggest that step edges can trap Pn molecules and act as nucleation sites for the growth of ordered thin films with a crystal structure similar to that of bulk Pn.Comment: 4 pages, 4 figures, 1 tabl

Self-assembly of Organic Molecules at Metal Surfaces

Adsorption and self-assembly of organic molecules at surfaces is a key issue in nanoscience and nanotechnology for the many possible uses of hybrid organic\u2013inorganic interfaces. Depending on the nature of the molecules, applications are foreseen in the fields of molecular electronics, sensoristics, pharmacology, biocompatibility, hygiene and biofouling. As a consequence, there has been a large effort in the last few years to determine the structure of the layers and to unravel the mechanisms at the basis of the self-assembly process