Mechanism of electron conduction in self-assembled alkanethiol monolayer devices

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 beta. From the bias dependence of beta, a barrier height Phi(B) of 1.39 +/- 0.01 eV and a zero-field decay coefficient beta(0) of 0.79 +/- 0.01 Angstrom(-1) are determined for alkanethiols.