Substantial local variation of Seebeck coefficient in gold nanowires

TL;DR

This study reveals significant local variation in the Seebeck coefficient within gold nanowires, influenced by structural defects and surface passivation, impacting thermoelectric behavior at the nanoscale.

Contribution

It demonstrates the spatial dependence of thermoelectric voltage in gold nanowires and highlights the influence of nanoscale structural features on thermoelectric properties.

Findings

Seebeck coefficient varies locally within nanowires

Thermoelectric voltage is sensitive to defects and surface passivation

Longer nanowires show extreme variability in thermoelectric response

Abstract

Nanoscale structuring holds promise to improve thermoelectric properties of materials for energy conversion and photodetection. We report a study of the spatial distribution of the photothermoelectric voltage in thin-film nanowire devices fabricated from single metal. A focused laser beam is used to locally heat the metal nanostructure via a combination of direct absorption and excitation of a plasmon resonance in Au devices. As seen previously, in nanowires shorter than the spot size of the laser, we observe a thermoelectric voltage distribution that is consistent with the local Seebeck coefficient being spatially dependent on the width of the nanostructure. In longer structures, we observe extreme variability of the net thermoelectric voltage as the laser spot is scanned along the length of the nanowire. The sign and magnitude of the thermoelectric voltage is sensitive to the structural defects, metal grain structure, and surface passivation of the nanowire. This finding opens the possibility of improved local control of the thermoelectric properties at the nanoscale.