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.