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C6: Novel applications
We will discuss optoelectronic properties of nanoscale junctions between nanowires of thermoelectric materials and conducting thin films. In our experiments we employed devices composed of bismuth telluride nanowire arrays which are capped with a transparent indium tin oxide electrode. The incident surface features very low optical reflectivity and enhanced light trapping. The unique attributes of the thermoelectric arrays are the combination of strong temporal and optical wavelength dependences of the photocurrent. Under infrared illumination, the signal can be completely described by "quasi-equilibrium" thermoelectric effects considering cooling rates given by heat diffusion through the array. The thermal diffusivity is found to be less (by a factor of 3.5) than in the bulk, a result that we discuss in terms of phonon confinement effects. Surprisingly, in addition to the infrared thermoelectric response, under visible illumination we observe a photovoltaic response. We will also discuss our results in light of recent reports of hot carrier thermoelectric response in atom layer materials like graphene. Preliminary results were presented in T.E. Huber et al, Applied Physics Letters 103, 041114 (2013).
