Temperature dependence of three-terminal molecular junctions with sulfur end-functionalized tercyclohexylidenes

We have studied the gate and temperature dependence of molecular junctions containing sulfur end-functionallzed tercyclohexylidenes. At low temperatures we find temperature-independent transport; at temperatures above 150 K the current increases exponentially with increasing temperature. Over the entire temperature range (10-300 K), and for different gate voltages, a simple toy model of transport through a single level describes the experimental results. In the model, the temperature dependence arises from the Fermi distribution in the leads and in a three-parameter fit we extract the level position and the tunnel rates at the left and right contact. We find that these parameters increase as the bias voltage increases.