Chemisorbed single molecules as electronic switches

The aim of this project is the direct investigation of the electrical conduction properties of single molecules with extended electronic π-systems, which are chemically bound to metallic contacts. We want to investigate the structure and the adsorption geometry at the atomic scale and finally want to functionalize these molecules and induce switchability by electric fields via the substrate or by additional electrodes. As a starting point we are planning to use silver electrodes and coordination compounds, such as functionalized ferrocene and phenyl substituted molecules (the latter as reference systems). For this purpose laterally open contact structures will be used, which allow direct access to the contact together with the adsorbed molecules. By use of the combination of a 4-probe STM with an SEM all steps like generation and characterization of contacts and molecules at the atomic scale can be carried out in situ, as well as electrical transport measurements. We further plan to vary chemical end groups and temperature in order to study the influence of coupling of the molecule to its environment on transport properties.