On-surface radical addition of triply iodinated monomers on Au(111)—the influence of monomer size and thermal post-processing

In the present study on-surface polymerisation of aromatic iodinated precursor molecules through radical addition is studied by scanning tunneling microscopy (STM) on Au(111) under ultra-high vacuum (UHV) conditions. Comparison of the two analogous monomers s-triiodobenzene and s-triiodophenylbenzene with similar symmetry and functionalization but differently sized organic backbones aimed to study the influence of monomer size on the morphology of resulting covalent networks. In contrast to previous studies on brominated monomers, here the reaction by-product, i.e., the split-off iodine atoms, was found to adsorb stably on Au(111) in ordered structures. The influence of post-processing by thermal annealing on both the covalent networks and the iodine structures was studied for different temperatures. DFT calculations were applied to evaluate formation energies of commonly observed topological defects and related to their experimental probability of occurrence.