Tunneling Currents through a Single Molecule Isolated in a New Matrix

Abstract

The electrical properties of single phenylene oligomers were studied in terms of the dependence of the tunneling current on the length of the oligomers using self‐assembling techniques and scanning tunneling microscopy (STM). It is important to isolate single molecules in an insulating matrix for the measurement of the conductivity of the single molecule. We show a novel self‐assembled monolayer (SAM) matrix appropriate for the isolation of the single molecules. Bicyclo[2.2.2]octane derivative was used for a SAM matrix, in which the single molecules were inserted at molecular lattice defects. The isolated single molecules of phenylene oligomers inserted in the SAM matrix were observed as protrusions in STM topography using a constant current mode. We observed two types of the motion of the single molecules inserted in the SAM matrix. First, the single molecules showed stochastic switching. Second, the single molecules moved laterally. These phenomena occurred spontaneously at room temperature. We measured the heights of the molecular protrusions using STM and estimated the decay constant, β, of the tunneling current through the single phenylene oligomers using a bilayer tunnel junction model.