This project being embedded in the funCOS research unit aims at the atomic-scale investigation of the binding of larger organic molecules to oxide surfaces. The molecule-oxide bond will be established by specific anchoring groups, which will be tested in view of their effectiveness and resulting configuration of the bound molecule.To this end, two scanning probe microscopy methods, Scanning Tunneling Microscopy (STM) and Atomic Force Microscopy (AFM) will be employed at liquid helium temperature (4.2 K) and in ultra-high vacuum. Within the project benzene and tetra-phenylporphyrine molecules substituted with -COOH, -OH, -NH2, and -CN groups will be deposited from the gas phase on magnesium oxide and cobalt oxide surfaces. By systematically varying linker units and oxide surface properties, the role of the anchoring group and the influence of surface termination and defects on the particular adsorption site and adsorption geometry will be analysed. By varying the temperature at which the molecules are imaged, diffusion processes will be studied and their energy barrier determined. Quantifying these processes is an important ingredient for understanding and steering self-assembly processes which is one of the overall aims of the funCOS research unit. The local probes employed in this project will help to assess the quality and homogeneity of self-assembled molecular layers on a mesoscopic scale.Further, spectroscopic methods of STM and AFM will be used to investigate the electronic structure and charge distribution of molecules adsorbed on oxide surfaces providing important data for comparison with theoretical modelling of the detailed binding of a molecule to oxides.
