Single Molecule Conductance of Ferrocene at Cryogenic and Room Temperature

Ferrocene and other metallocenes are organometallic species with a metal atom sandwiched between two aromatic rings whose overall spin, spectrum and other properties can be tuned synthetically by choice of metal atom. There is interest in these molecules as candidates for applications in single molecule electronics and spintronics. However, few electron transport measurements of single metallocene molecules on metal have been performed to date. Previous conductance measurements of ferrocene using single molecule break junctions employed anchoring groups to attach the ferrocene to the electrodes, thereby changing the molecular orbitals energy levels and attenuating electron transport. Here, we use Scanning Tunneling Microscope-based break junction technique to measure conductance of ferrocene on gold at room temperature and at 4 K in UHV. We are able to effectively trap the molecule between the tip and substrate while pushing the junction together and find that the molecule binds to gold directly through carbon atoms in the cyclopentadiene organic ligands sandwiching the iron, and has an average conductance of 0.012 G₀. Using this technique, we investigate the effect of the metal atom on transport properties by measuring conductance through other metallocene molecules.