This thesis describes the investigation of fundamental properties of molecules in the tunnelling junction using combined scanning tunneling (STM) and atomic force microscopy (AFM).
In this work, five different experimental topics are addressed.
A reduction of the single-particle level spacing of two frontier orbitals enables the manifestation of strong electron-correlation effects in single molecules. In this regime conduction exhibits a spatial signature fundamentally different from what a single particle picture would predict.
Individual molecules at the edges of self-assembled islands temporarily change their charge state due to the presence of the electric field from a scanning-probe tip. Close to the threshold voltage for a charge state transition, periodic switching of the charge is directly driven by the cantilever motion in frequency-modulated AFM.
A novel concept for the realization of molecular quantum cellular automata is demonstrated. The solution lies in the combination of the creation of perfectly aligned inactive cells by self-assembly as a first and their selective and controlled activation as a second step.
A real space investigation of a singly charged molecules adsorbed on an ultrathin insulating film reveals a two-level system that can reversibly change between configurations, resembling the motion of a rocker switch.
Selective intermolecular aryl-aryl coupling via dehydrogenative C-H activation occurs on the surface upon thermal annealing. A full atomistic description of the different reaction products based on an unambiguous discrimination between pyrazine and pyridine moieties is presented.