Thioether-Linked Single-Molecule Junctions with Coinage Metal Contacts.

The influence of changing electrode material on the electrical and mechanical properties of metal-molecule-metal junctions is relatively poorly understood, yet an improved understanding of these interfaces remains critical to the implementation of such systems as active elements in real-world circuits. Accordingly, here we study single-molecule junctions comprising thioether-linked alkane and oligophenyl wires formed under an inert atmosphere using gold, silver, and copper electrodes. Break junction experiments and computational simulations reveal that the conductance of junctions with different contacts typically decreases in the order gold > silver ≥ copper. Such trends cannot be explained solely from the differences in work function for these metals, which are modulated in junctions by the interface dipole. Transport calculations also expose the influence of electronic coupling to the electrodes, which is strongest for gold. Together, this study charts a coherent path toward a more complete understanding of the role of the electrode in single-molecule devices.