DFT-based study of electron transport through ferrocene compounds with different anchor groups in different adsorption configurations of an STM setup

摘要

In our theoretical study in which we combine a nonequilibrium Green's function approach with density functional theory (DFT) we investigate compounds containing a ferrocene moiety which is connected to (i) thiol anchor groups on both sides in a para-connection and (ii) a pyridyl anchor group on one side in a meta-connection and a thiol group on the other side in a para-connection, in both cases with acetylenic spacers in between the ferrocene and the anchors. We predict possible single-molecule junction geometries within a scanning tunneling microscopy (STM) setup, where we find that the conductance trend for the set of conformations is intriguing in the sense that the conductance does not decrease while the junction length increases, which we analyze and explain in terms of the Fermi level alignment. We also find a pattern for the current-voltage (I -V) curves within the linear-response regime for both molecules we study, where the conductance variation with the molecular configurations is surprisingly small.