Thermopower characterization of InSb nanowires using thermoreflectance

Increasing energy demand and depleting fossil fuels make it imperative to shift to more efficient energy sources. Thermoelectric materials can convert waste heat into electrical energy by means of the Thermopower or Seebeck effect. Nanowires are promising candidates to increase the efficiency of thermo-electric conversion because their low dimensionality is predicted to increase the Seebeck effect due to confinement of charge carriers and decrease thermal conductivity due to boundary scattering of phonons. The Seebeck effect is characterized by the Seebeck coefficient which describes the output voltage per degree Kelvin in a thermoelectric material. Hence, in order to obtain the Seebeck coefficient, it is crucial to accurately measure the temperature difference along the axial direction of the nanowire which has a length of a few micrometers, at the locations where voltage measurements are performed under a temperature gradient. Here we demonstrate an application of thermoreflectance to measure the temperature difference along the nanowire allowing bi-directional measurements of Seebeck coefficient.