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A5: Nanoscale and low dimensional effects
Conversion of relatively low temperature heat into electricity using devices with no moving parts has mostly focused onto thermoelectric generators. Although impressive results achieved over the last decade have brought to major efficiency improvements, still heat conversion is limited by the material non-zero thermal conductivity. Thermotunneling generators (TTGs) promise instead a much larger conversion rate because of the very high thermal resistance of the vacuum nano-gap between the electrodes1−3. Two major issues have limited the development of TTGs, namely the technological hurdle of reliably fabricating nanogaps; and the need for materials with very low work functions (≤ 1 eV). As progress in nanotechnology is making the former obstacle vanish, an alternate device design might loosen the latter constraint. In this study we show how the implementation of two different materials for the anode and the cathode can be used to enhance the tunneling current occurring in the device. We show that with a proper choice of the two electrode materials a smoothing of the tunneling barrier associated with a non-symmetric electric potential may be obtained within the nanogap. This effect may be implemented to obtain high-current TTGs using materials with work functions exceeding 1 eV, still with feasible nanogaps larger than 2 nm – opening opportunities for the actual nanofabrication of thermotunneling generators.
References
(1) Despesse, G., Jager, T., J. Appl. Phys., 96, 5026-5031 (2004)
(2) Tavkhelidze, A. N., J. Appl. Phys., 108, 044313 (2010)
(3) Arik, M., Bray, J., Weaver, S., Proc. SPIE 7679, 76791F (2010)