Nanoscale Ordering at the Liquid-Solid Interface using Self-Assembly Principles
The focus of this work is on the investigation and the understanding of molecular adsorption at the liquid-solid interface. Unlike ultra high vacuum conditions, this highly dynamic environment gives room for multiple ways controlling the structure formation, through adapting external parameters. In order to achieve self-assembled networks with a high degree of flexibility it was important to choose systems with weak to moderately strong binding behavior, both between molecule and substrate, and amongst the molecules. All selected molecules have mere van der Waals interaction with the substrate in common. In order to promote specific molecule-molecule interaction they are equipped with the ability to form hydrogen bonds. These bonds ideally meet the requirements for well ordered two-dimensional monolayers: On one hand, they are rendering a reorganization of networks possible due to easy connecting and disconnecting, i.e. a comparability between binding energy and thermal energy. On the other hand, they provide sufficient stability within the monolayer, and lead to a well defined geometry between neighboring molecules due to their high directionality. Scanning Tunneling Microscopy (STM) has been proven as a very appropriate tool to investigate these self-assembled structures at the liquid-solid interface. STM provides real space images of the molecular networks with near atomic resolution.