Effect of Electrode Orientations on Charge Transport in Alkanedithiol Single-Molecule Junctions

Using first-principles calculations based on the density functional theory and the nonequilibrium Green's functions approach, we study the charge transport in Au-alkanedithiol-Au single-molecule junctions with different electrode orientations and molecular lengths. We attribute the recently measured high-/low-conductance in these heterostructures to two distinct electrode orientations, [100] and [111], which can control the electrode-molecule coupling as well as the tunneling strength by way of diverse band structures. Our detailed analysis on the transmission spectra suggests that even a single alkanedithiol junction can serve as a double quantum-dot system to yield tunable quantum interference.