Formation of composite C60-perylene layers on a silver substrate

Molecules provide versatile building blocks capable of generating remarkably diverse macromolecular systems. Such bottom-up nanofabrication approaches are currently often used to create a range of molecular architectures at surfaces via molecular self-assembly. In this perspective, we present an STM study of the formation of composite layers of organic molecules designed by depositing C60 fullerene on a previously formed multilayer of perylene on an Ag(110) substrate. We underline the interest in studying mixed layers of these two molecules forming a weakly interacting system. The room temperature STM study at the molecular scale, complemented with modeling of the intermolecular interactions, revealed that adsorption of C60 does occur on top of the outer perylene compact rows along the [1-10] substrate axis. The fullerenes tend to aggregate within alignments along the axis of the compact rows of the perylene structure; the higher the coverage, the longer the alignments. In the most compact ones, the C60s are periodically positioned at a 2b1 distance, b1 being the inter-perylene distance within the [1-10] compact rows. Furthermore, the C60s adsorb preferably on "Short bridge" sites, meaning above and between the underlying upper perylenes. Modeling of the intermolecular interactions in this system confirms the STM measurements and points to the ability of the underlying perylene multi-layer to drive the fullerene assembly.