Unconventional co-existence of plasmon and thermoelectric activity in In:ZnO nanowires

Metal-doped ZnO nanowires exhibit the unique property of being simultaneously thermoelectric transparent conductors and low-loss plasmonic materials in the near-IR and visible range. Using calculations from first principles, we identify the mechanisms that regulate this behavior at the nanoscale and we describe how nanostructuring affects the optoelectronic, vibrational and transport properties of In: ZnO nanowires. Our results reveal that In doping imparts a good electrical conductivity and provides an injected free charge sufficient to sustain a surface-plasmon-polariton excitation. At the same time, surface scattering effects efficiently quench the thermal conductivity along the wire, improving the thermoelectric figure of merit of the system with respect to the bulk material. The coexistence of plasmonic and thermoelectric characteristics fosters the design of a novel class of coupled nanostructured devices for photothermal-electrical energy conversion.