Dependence of thermoelectric effects in molecular junctions on the topography of the bottom electrodes

This study addresses the influences of the topography of the bottom electrodes on the properties of the thermoelectric effects across molecular wires made from self-assembled monolayers (SAMs) of oligophenylenethiolates or alkanethiolates. We showed that the flatter the surface of the electrode, the better would be the packing of molecules, resulting in the larger values of the Seebeck coefficient. Surprisingly, the analysis of the power factor (PF) for both the SAMs of oligophenylenethiolates and alkanethiolates suggested that an optimal roughness of bottom electrodes as well as molecular length could be found for the highest values of PF rather than the flattest surfaces. Our results indicated that the topography of the bottom electrodes plays a crucial role in SAM-based molecular thermoelectric effects. The values of the Seebeck coefficient and power factor of a molecular junction can be regulated by the topography of the electrode.