Tuning spin and charge at a metal-organic hybrid interface

Abstract

Metal-organic interfaces are key constituents of the various functional building blocks that can be found in molecular electronics and spintronics. Long electron and spin relaxation times of organic molecules make them superior to inorganic materials for many technological devices. When put into contact with a metal electrode, the hybridization of molecular orbitals and metallic states can lead to several intriguing effects, which strongly affect the electronic and magnetic properties of the system. In this regard, the interface obtained by depositing nickel tetraphenyl porphyrin onto the copper (100) surface (NiTPP/Cu(100)) can be seen as an interesting model system. Previous experiments reported an unexpected high charge transfer leading to a partial filling of the molecular orbitals up to the LUMO+3 and a reduction of the central nickel atom. Considering this observation as the point of departure, this thesis aims to develop different approaches to alter the hybridization at this interface. The results of this thesis can be divided into three main topics. First, it is shown that a pre-oxidation of the copper substrate leads to a substantial quenching of the charge transfer from the metal to the molecule and, thereby, weakens the interaction. In a second step, the spin configuration of the chelated nickel ion is changed by an on-top adsorbed NO2 molecule. The third part addresses the temperature-induced changes at the NiTPP/Cu(100) interface upon annealing. Up to the limit of thermal decomposition, the NiTPP molecules do not undergo chemical changes but only conformational modifications.