HETERO-INTERFACES: FUNCTIONAL MOLECULAR FILMS AND LOW DIMENSIONAL MATERIALS

The aim of this PhD work is to study the formation and the electronic and morphologic properties of complex organo-metallic and hetero-organic architectures, grown on metal surfaces via a bottom-up approach. Different systems have been investigated, in order to monitor distinct situations occurring on a surface. The largest part of this work has been focused on the boroxine-based systems. This covalently-bonded films have been explored with a multi-technique approach that allowed a deeper insight in their nature. We have prepared a novel 2D material based on the boroxine unit and consisting in boron and oxygen atoms only. Moreover, we have found interesting electronic properties, such as a channel for ultra-fast charge delocalization toward the golden substrate in all the boronic systems and a dispersion in the valence band for this 2D material. These results allow to gain a new perspective in the boroxine based systems. From material mostly known for their morphological properties, we have highlighted the presence of interesting electronic properties. In addition to the covalently bonded boroxine systems, we have focused also on the possibility of building more complex architectures upon metallic substrates via weak interactions. In particular, we have taken advantage of one of the already investigated boroxine systems to study the interplay between the boron molecule, acting as a Lewis acid, and an amine acting as a Lewis base. We have evidenced a very interesting morphological change confirming that the interaction has taken place. Similarly, we have built another complex architecture relaying on weak interactions. We have taken advantage of a H-bonding to anchor a crown ether derivative on a substrate. Then we used the interaction between sodium and crown ethers to trap an alkali metal on the surface. In this experiment, we have used the crown ether for the first time on a substrate in UHV, and we have found that the affinity toward the metal is preserved. The last investigated system is also characterized by the presence of weak interactions between the molecules deposited on the surface. Despite of this similarity with the previous scientific case, the application target was completely different. We were not interested in building structures on a substrate, but we decided to take advantage offered by the UHV to study the behavior of molecules important in catalysis. In this case, we have studied the melamine and melem molecules, precursors of the 2D carbon nitride, an interesting photocatalyst for the water splitting reaction. This approach has been successful, and we gained a deeper insight in the H-bonding properties of the monitored molecules.