This thesis is focused on the links between charge transfer (CT) at metalorganic (MO) interfaces, creation of surface dipoles and two-dimensional supra- molecular assembly. Although several examples can be found in the literature where molecular self-assembly on surfaces was in uenced by the formation of interfacial dipoles, only in a few cases were the results fully rationalised and only a posteriori. The MO interface resulting from the deposition of the molecules used for these studies (chosen for their relevance as building blocks for applications in organic opto-electronic, photovoltaic, or proposed organic spintronics devices) is usually very complex. This is mainly due to the chemical structure of these molecules and to their strong interaction with the substrate. A clear identification of the different fundamental processes (such as CT and formation of interfacial dipoles) is thus highly difficult. The approach followed in this thesis is markedly different: specific molecules were rationally designed and subsequently synthesised in order to obtain model systems where the different parameters could be clearly isolated and identified. The presented work is the result of a close collaboration with other two research groups: the organic synthetic chemistry group of Prof. D. Bonifazi and the theoretical group of Prof. A. De Vita. The study was addressed through a complementary multi-disciplinary theoretical and experimental investigation, including the synthesis of new molecules, the analysis of their self-assembly by scanning tunnelling microscopy and spectroscopy and the use of density functional theory calculations and Monte Carlo simulations for the theoretical modelling of the systems. A balance between omnipresent short-range van der Waals attractive forces and long-range repulsive interactions generated by CT at MO interfaces was found to be responsible for the spontaneous formation of novel classes of supramolecular structures. By selecting different metal substrates and by carefully modifying the molecular species through chemical synthesis, the CT was selectively inhibited or enabled. This strategy represents a new paradigm for predicting and controlling the molecular self-assembly at surfaces. Conversely, the appearance of specific molecular linkage patterns is used to reveal the occurrence of CT and provides a novel means for obtaining crucial information on the electronic properties and the energy level alignment of MO interfaces.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:606189 |
| Date | January 2014 |
| Creators | Della Pia, Ada |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/60286/ |
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