Charge transport of alkanedithiol self-assembled monolayers studied by using conducting atomic force microscopy

We use conducting atomic force microscopy with a variety of measurement techniques to study charge transport in alkanedithiol self-assembled monolayers (SAMs) formed in metal-molecule-metal junctions. The temperature-independent current-voltage behavior and the correct exponential decay of the conductance with respect to the molecular length show that the dominant charge transport mechanism for alkanedithiol SAMs is tunneling. In addition, length-variable transition-voltage measurements indicate that the energy barrier height for charge transport in alkanedithiol SAMs is independent of the molecular length.