ESR01: Employing ab-initio methods to study distinct scenarios of adsorption of organic molecules on inorganic surfaces / Thesis

Technical University of Graz (TUG), Austria
Shashank Shekhar Harivyasi
PhD Thesis download /

Abstract: In this work, we study two distinct scenarios of adsorption of organic molecules on metal surfaces—non-planar Chloro boron-subphthalocyanine(ClB-SubPc) molecules on a Cu(111) surface as well as a perfluoroanthracenylaminoalkane thiolate selfassembled monolayer (SAM) that forms on Au(111) — using different methodologies albeit with similar motivation: simulating experimentally relevant systems. Incaseof ClB-SubPc onCu(111), ourgoalwastodevelopanunderstandingofthe registry between adsorbate and the substrate, to develop on results from scanning tunneling microscopy (STM) experiments as well as to explore the interfacial electronic structure. We found that the registry is governed by interaction between the molecule’s nitrogen atom atoms and the six-fold symmetry of the underlying substrate. By comparing simulated STM results with those experiments, we found that adsorption on Cu(111) leads to dechlorination of the ClB-SubPc molecule, resulting in formation of two chemically different moieties on the surface. To explore the evolution of interfacial electronic structure in relation to the molecule’s peculiar geometry, we introduced a novel methodology and found the adsorption of this moleculeisanunusualcaseofvanderWaals-interactionactivatedstrongelectronic interaction. For the perfluoroanthracenylaminoalkane thiolate SAM, our main goal was to be able to simulate its near edge X-ray absorption fine structure spectra in order to experimental understanding of the system. This work was a partial success because of the limitations of the presently available methodology. However, we were able identify the source of the problem and future improvements to the methodology might resolve the issue.

Recent publication.