Evaluation of the Electronic Structure of Single-Molecule Junctions Based on Current-Voltage and Thermopower Measurements: Application to C₆₀ Single-Molecule Junction

The electronic structure of molecular junctions has a significant impact on their transport properties. Despite the decisive role of the electronic structure, a complete characterization of the electronic structure remains a challenge. This is because there is no straightforward way of measuring electron spectroscopy for an individual molecule trapped in a nanoscale gap between two metal electrodes. Herein, a comprehensive approach to obtain a detailed description of the electronic structure in single-molecule junctions based on the analysis of current-voltage (I-V) and thermoelectric characteristics is described. It is shown that the electronic structure of the prototypical C₆₀ single-molecule junction can be resolved by analyzing complementary results of the I-V and thermoelectric measurement. This combined approach confirmed that the C₆₀ single-molecule junction was highly conductive with molecular electronic conductances of 0.033 and 0.003 G₀ and a molecular Seebeck coefficient of -12 μV K^-1 . In addition, we revealed that charge transport was mediated by a LUMO whose energy level was located 0.5≈0.6 eV above the Fermi level of the Au electrode.