Electrical Characterization of Single Molecules via Mechanically Controllable Break Junctions

Molecular electronics has been a field of big interest for the last years. Using the technique of mechanically controllable break junctions we characterize different organic molecules, e.g. 1,4-Diethoxy-2,5-bis(4-sulfanyl-phenylethynyl)-benzene (PEEB) and switchable molecular wires, dissolved in an organic non-polar solvent. IV-curves taken from the molecules connected to single gold atom contacts show the expected tunneling behavior described by the single-level model: weak coupling of the molecules to the gold atoms implies an off-resonant tunneling process and a transport through a single channel. Varying the end-groups of the molecules leads to a different transport behavior. Figure 1 shows a 2D histogram of IV-curves of PEEB with amino end-groups. Based on the single-level transport model the analysis of the current-voltage characteristics delivers the energy of the molecular level and the coupling between electrode and molecule. It also indicates a reliable contact of the molecules to the gold atoms. A further goal is the investigation of an electric gate effect on the transport behavior through the molecules.