Temperature-dependent I–V characteristics for the nanocomposite semiconducting films composed of a thiol end-capped dinuclear macrocyclic complex and Au-NPs bridging 1 μm gap gold electrodes

Abstract

A rigid trans pyridine-4-thiol coordinated dinuclear zinc(II) macrocyclic complex trans-[Zn₂L(py-4-SH)₂](ClO₄)₂ (1) is introduced for the first time to fabricate self-assembled nanocomposite films with gold nanoparticles (Au-NPs) covering 1 μm gap gold electrodes. Utilizing the same self-assembled fabrication technique but different concentrations of dithiol 1 and Au-NPs in chloroform, a series of molecular-scale electronic devices 2–5 have been obtained exhibiting typical temperature-dependent (8–300 K) semiconducting I–V characteristics on the order of μA, nA and pA in the temperature range of 8–300 K. The transformation from an insulating dinuclear zinc(II) macrocyclic complex to a semiconducting nanocomposite thin film is thereby achieved by means of the Au–S bonded contacts between dithiol end-capped molecules and Au-NPs as well as the unique charge separation and electron transportation abilities of Au-NPs. From the classical Arrhenius plots, it is concluded that the temperature-independent tunneling current between Au-NPs in the 1 × 1 μm² region dominates the conductance below 100 K. However, the tunneling current is overwhelmed by the temperature-dependent thermal excitation current with the increase of temperature and the hopping conductance finally governs the electron transportation among the molecules.