  Understanding how the mechanism of charge transport through molecular tunnel
junctions depends on temperature is crucial to control electronic function in
molecular electronic devices. With just a few systems investigated as a
function of bias and temperature so far, thermal effects in molecular tunnel
junctions remain poorly understood. Here we report a detailed charge transport
study of an individual redox-active ferrocene-based molecule over a wide range
of temperatures and applied potentials. The results show the temperature
dependence of the current to vary strongly as a function of the gate voltage.
Specifically, the current across the molecule exponentially increases in the
Coulomb blockade regime and decreases at the charge degeneracy points, while
remaining temperature-independent at resonance. Our observations can be well
accounted for by a formal single-level tunneling model where the temperature
dependence relies on the thermal broadening of the Fermi distributions of the
electrons in the leads.
