Thema der Dissertation:
Functionalisation of 2D-Semiconductors with Organic Molecules
Functionalisation of 2D-Semiconductors with Organic Molecules
Abstract: Combining organic molecules with inorganic substrates, especially two-dimensional materials such as transition-metal dichalcogenides (TMDCs), is a wide field with much interest and many possibilities. Finding the right combination to achieve a purposeful union with desired properties requires a detailed examination of the fundamental processes that occur in these hybrid systems. Scanning tunnelling microscopy (STM) and spectroscopy (STS) are ideal tools for investigating these hybrid systems, as they allow us to employ their powerful capabilities of local spatial resolution on the atomic scale,resulting in direct access to the local electronic structure. The locality of electronic effects is a crucial piece of information in reaching a full understanding of the various mechanisms at play.
Here, we utilise STM and STS to investigate different hybrid systems under different aspects: First, we explore the capabilities of MoS2 as a decoupling layer that enhances the lifetime of molecular states inside its bandgap. Using the model system of single vanadyl-naphthalo-cyanine (VONc) molecules adsorbed on MoS2/Au(111), we study the electronic states of this molecule in detail. We identify the observable in-gap states and analyse the local variations in the electronic structure which are determined to be caused by the tip-perturbation potential as well as vibration-induced effects such as vibrationassisted tunnelling.
Secondly, we create and explore the system of trifluoromethyl-terphenyl-thiol (CF3-3PSH) molecules on MoS2/Au(111). We investigate the chemisorption process of anchoring CF3-3P-S(H) molecules to purposefully created S-vacancies in the MoS2 monolayer. The anchoring molecules are identified by their rotation around one of their terminations. We observe two different species of anchored molecules that differ only in their electronic structure: the majority shows nothing around the Fermi energy, whereas a small percentage exhibits a peak at zero bias which we assign to a Kondo resonance. This chemisorption process is untangled at the atomic level by combining experiment and theory in collaboration. Detailed theoretical analysis confirms that two different molecular species are involved: intact CF3-3P-SH and dehydrogenated CF3-3P-S. Both show electronic states inside the bandgap of MoS2 which crucially differ in their occupation.
Here, we utilise STM and STS to investigate different hybrid systems under different aspects: First, we explore the capabilities of MoS2 as a decoupling layer that enhances the lifetime of molecular states inside its bandgap. Using the model system of single vanadyl-naphthalo-cyanine (VONc) molecules adsorbed on MoS2/Au(111), we study the electronic states of this molecule in detail. We identify the observable in-gap states and analyse the local variations in the electronic structure which are determined to be caused by the tip-perturbation potential as well as vibration-induced effects such as vibrationassisted tunnelling.
Secondly, we create and explore the system of trifluoromethyl-terphenyl-thiol (CF3-3PSH) molecules on MoS2/Au(111). We investigate the chemisorption process of anchoring CF3-3P-S(H) molecules to purposefully created S-vacancies in the MoS2 monolayer. The anchoring molecules are identified by their rotation around one of their terminations. We observe two different species of anchored molecules that differ only in their electronic structure: the majority shows nothing around the Fermi energy, whereas a small percentage exhibits a peak at zero bias which we assign to a Kondo resonance. This chemisorption process is untangled at the atomic level by combining experiment and theory in collaboration. Detailed theoretical analysis confirms that two different molecular species are involved: intact CF3-3P-SH and dehydrogenated CF3-3P-S. Both show electronic states inside the bandgap of MoS2 which crucially differ in their occupation.
Zeit & Ort
10.07.2024 | 10:00
Hörsaal B (0.1.01)
(Fachbereich Physik, Arnimallee 14, 14195 Berlin)