Time resolved charge transport properties of single-molecule junctions

Charge transport properties through molecules have been studies on the single molecule scale using the break junction (BJ) technique. Here, we investigate time resolved single-molecule transport properties, which has been masked by time averaged electric measurement. Target molecules are benzene-type molecules with different anchor group of thiol, amine, and isocyanide. Single-molecule junctions of each target molecule sandwiched by Au electrodes are created by the BJ technique. We developed current vs bias voltage (I−V) measurement technique to obtain time resolved change in the metal-molecule electronic interactions (Γ) and the molecular energy level relative to the Fermi level of the electrodes (ε). Time resolved I−V curves were measured during the self-breaking process of the single-molecule junctions at room temperature. We found both ε and Γ decreased for all molecules in a 1 ms time window just before the self-breaking event. The decay factor t_A (Here, A(t) = A₀ exp(−t/t_A) and A = ε or Γ) were t_ε > t_Γ for thiol, t_ε = t_Γ for amine, and t_ε < t_Γ for isocyanide. This study provides insight into time resolved change in the transport properties and the electronic structure (i.e., e and G) on the single-molecule scale.