Electron tunneling through self-assembled monolayers (SAM’s) of alkanethiols is investigated using nanometer-scale devices. Temperature-dependent current-voltage measurements are performed on alkanethiol SAM’s to distinguish between different conduction mechanisms. Temperature-independent electron transport is observed, proving that tunneling is the dominant conduction mechanism of alkanethiols, as well as exhibiting an exponential dependence of tunneling current on the molecule length with a decay coefficient β. From the bias dependence of β, a barrier height ${\Phi }_B$ of $1.39\pm 0.01\mathrm{eV}$ and a zero-field decay coefficient ${\beta }_0$ of $0.79\pm 0.01{\AA }^{-1}$ are determined for alkanethiols.

• Received 3 September 2002

DOI:https://doi.org/10.1103/PhysRevB.68.035416