School of Physics Condensed Matter Series: Dr. Quirin Stöckl, Swiss Federal Laboratories for Materials Science and Technology (EMPA)

Fivefold symmetry is incompatible with the translational order in all 17 plane groups and is therefore of fundamental interest for two dimensional crystallization processes. A model study on single crystal surfaces, e.g. Cu(111), has been carried out to better understand the fundamental principles of intermolecular interactions between fivefold symmetric corannulene and its derivatives in two-dimensional clusters and lattices, including those consisting of fivefold bowl-shaped (buckybowl) molecules. Rational molecular design and state of the art surface science methods, e.g. Scanning Tunneling Microscopy, Low Energy Electron Diffraction, X-Ray Photoelectron Spectroscopy, Ultraviolet Photoelectron Spectroscopy, Temperature Programmed Desorption, and Reflection Adsorption Infrared Spectroscopy were applied. Several reversible surface phases were identified, including stripes, zig-zag, rosette and rotator phases. The packings of fivefold symmetric molecules was found to exhibit the same patterns upon adsorption as identified in the closest packings of hard pentagons and five-pointed stars.