Multivariate Approach to Single-Molecule Thermopower and Electrical Conductance Measurements

We report a method using scanning tunneling microscope single molecular break junction to simultaneously measure and correlate the single-molecule thermopower and electrical conductance. In contrast to previously reported approaches, it does not require custom-built electronics and takes advantage of a trace-by-trace calibration of the thermal offset at the Au/Au contact, thus greatly facilitating thermoelectric measurements at the single-molecule level. We report measurements of three molecules, 1,4-di(4-(ethynyl(phenylthioacetate))) benzene, 1,8-octanedithiol, and 4,4'-bipyridine, and determine single-molecule Seebeck coefficients of 12(3), 5(2), and -5(2) mu V K-1, respectively. Furthermore, the method statistically correlates the Seebeck voltage offset, electrical conductance, and stretching displacement of the single-molecule junction and allows for direct comparison with current-distance spectroscopy results obtained at constant bias.