A multivariate approach to single-molecule thermopower and electric conductance measurements

TL;DR

This paper introduces a simplified method using a scanning tunnelling microscope to measure and correlate single-molecule thermopower and conductance without custom electronics, enabling detailed analysis of molecular junctions.

Contribution

It presents a novel, trace-by-trace calibration technique for thermoelectric measurements at the single-molecule level, improving accuracy and ease of use.

Findings

Measured Seebeck coefficients for three molecules: 12, 5, and -5 microV/K.

Established correlation between thermopower, conductance, and displacement.

Method enables direct comparison with current-distance spectroscopy results.

Abstract

We report a method using scanning tunnelling 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) microV 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.