Mechanism of electron conduction in self-assembled alkanethiol monolayer devices

Abstract

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 \ensuremath{\beta}. From the bias dependence of \ensuremath{\beta}, a barrier height ${\ensuremath{\Phi}}_{B}$ of $1.39\ifmmode\pm\else\textpm\fi{}0.01\mathrm{eV}$ and a zero-field decay coefficient ${\ensuremath{\beta}}_{0}$ of $0.79\ifmmode\pm\else\textpm\fi{}0.01{\AA{}}^{\ensuremath{-}1}$ are determined for alkanethiols.