Understanding the adsorption of non-planar Subphthalocyanine molecule on the Cu(111) surface
Shashank S. Harivyasi
Institute of Solid State Physics, NAWI Graz, Graz University of Technology
15:00 - 15:40 Friday 17 November 2017 Hörsaal Ventrex (NT03034)

We know that the structure of an organic molecule plays a determining role in its adsorption on metal surface and on the subsequent interaction between them. However, the case can be quite complex for non-planar molecules which show a varying tendency in planarization upon adsorption. Here, we try to understand these phenomena in a system that shows extreme behavior: adsorption of shuttle-cock shaped three-fold symmetric Chloroboron subphthalocyanine molecule on Cu (111) surface results in an almost complete planarization and considerable hybridization of molecular orbitals with metal electronic states, making this interface an interesting test-case for understanding the link between the two phenomena. Moreover, at sub-monolayer coverage, the adsorbed molecules aggregate into two separate phases that show different growth behavior.

In this talk, I combine results from density-functional theory and from ultraviolet photospectroscopy & low-temperature STM to analyze the adsorption process as well as the interfacial geometry and electronic structure of the molecule on Cu(111). Using DFT, we study the adsorption process and follow the evolution of the molecule’s electronic and geometrical structure. We identify that the bonding of the molecule is a gradual process involving Fermi-level pinning followed by a rehybridization of the molecule’s frontier orbitals. Especially the observed evolution of charge rearrangements aids us in explaining why we see an almost complete planarization. Further, by investigating different possible conformations and their energy costs, and by comparing simulations and experiments, we deduce that the molecule on Cu(111) is susceptible to dechlorination. Since a majority but not all molecules undergo dechlorination, the overall result is a formation of two different species that, in turn, lead to the formation of the two phases. The results thus highlight the need to carefully consider all surface-mediated physical and chemical processes that might happen.