First-principles study of charge transport across alkene thiolate self-assembled monolayers

Carrying out first-principles density-functional and matrix-Green´s function calculations, we study the electron tunneling through self-assembled monolayers (SAMs) of conjugated n-alkene chains (n = 8, 12, 16, and 30) bridged to Au(lll) electrodes via monothiolate and dithiolate contacts. In contrast to the semiconducting behavior of bulk polyacetylenes, we do not find any current decay up to 30-alkene chain length. Comparing tiholate and dithiolate cases, we observe only a small difference in their resistance (ratio of 2.8), or minor dependence of charge transport characteristics on the contacts. We thus predict that ideal nanoscale alkene chains can be a good wire component for molecular electronics.