Non-covalent Molecular Wires of Double Thiahelicene on Cu(111): A nc-AFM Study at Room Temperature

The fine control of molecules or atoms in self-assemblies on surfaces is a great challenge for future nanodevices, specially for unidimensional structure formations. In this context, our study explores the adsorption behavior of a benzo-fused double [7]thiahelicene (DT7H) on Cu(111). Using non-contact atomic force microscopy (nc-AFM) at room temperature, we prove their capability in the construction of linear-like shape adlayers. After a gentle annealing of the DT7H-copper interface, the molecules are prone to form non-covalent molecular wires which orientations are influenced by the surface symmetry. Analysis of the coverage-dependence reveals a preference for double wires at lower and intermediate densities. However, this coupling is not strong enough to prevent structural changes caused by surface mobility. Wire enlargements were induced by a further increase in surface coverage, reaching the assembly of 17 parallel molecular wires near full monolayer conditions. Finally, the electronic properties of the interface were characterized by means of Kelvin probe force microscopy (KPFM). The surface potential variations indicate a reduction of the surface work function on the regions covered by molecules, showing the functionality of this interface for optoelectronic applications.