Room temperature stable single molecule rectifiers with graphite electrodes

In this combined theoretical and experimental study we present new molecular electronics device characteristics of unprecedented stability at room temperature by using electrodes based on highly oriented pyrolytic graphite with covalently attached molecules. To this aim, we explore the effect of the anchoring group chemistry on the charge transport properties of graphite/molecule contacts by means of the scanning tunneling microscopy break-junction technique and ab initio simulations. The theoretical approach to evaluate the conductance is based on density functional theory calculations combined with the non-equilibrium Green’s function technique, as implemented in the Smeagol electron transport code \footnote{A. Rocha et al., Nature Mater. {\bf 4}, 335 (2005); A. Rocha et al., Phys. Rev. B {\bf 73}, 085414 (2006); I. Rungger et al., Phys. Rev. B {\bf 78}, 035407 (2008)}. We also demonstrate a strong bias dependence and rectification of the single molecule conductance induced by the anchoring chemistry in combination with the very low density of states of graphite around the Fermi energy. We show that the direction of tunneling current rectification can be tuned by anchoring group chemistry.