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Synthesis and characterization of low work function alkali oxide thin films for unconventional thermionic energy converters

Valentina Giorgis 1 François Morini 2 Tianqi Zhu 1 J.F. Robillard 3 X. Wallart 4 Jean-Louis Codron 5 Emmanuel Dubois 3 
3 MICROELEC SI - IEMN - Microélectronique Silicium - IEMN
IEMN - Institut d’Électronique, de Microélectronique et de Nanotechnologie - UMR 8520
4 EPIPHY - IEMN - EPItaxie et PHYsique des hétérostructures - IEMN
IEMN - Institut d’Électronique, de Microélectronique et de Nanotechnologie - UMR 8520
5 CMNF - IEMN - Centrale de Micro Nano Fabrication - IEMN
IEMN - Institut d’Électronique, de Microélectronique et de Nanotechnologie - UMR 8520
Abstract : In this work, we present the synthesis and the characterization of low work function thin films for Micro Thermionic Converters (MTC). The objective is producing a device operating at relatively low temperature (< 1000 K). We aim at improving the MTC efficiency by reducing the work function of the electrodes and increasing the emitted current density by alkali metal oxides electrodes coating. In particular, in this work, we analyse and compare the performances of two alkali metal oxides: potassium and caesium oxides. Our choice to exploit those materials relies on their low work function and their abundance. For both materials, we present the results on the synthesis of the oxides under high vacuum and controlled temperature. The oxide thin films were characterized by X-ray photoelectron spectroscopy, photoemission, and thermionic emission measurements. By exploiting the latter technique, a quantitative evaluation of the current density, emitted by the heated oxides, is obtained as a function of temperature. Our results demonstrate that it is possible to decrease the silicon work function by almost 3 eV, enabling significant thermionic currents despite relatively low temperatures (below 850 K). Published by AIP Publishing.
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Submitted on : Wednesday, August 17, 2022 - 5:54:26 PM
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Valentina Giorgis, François Morini, Tianqi Zhu, J.F. Robillard, X. Wallart, et al.. Synthesis and characterization of low work function alkali oxide thin films for unconventional thermionic energy converters. Journal of Applied Physics, American Institute of Physics, 2016, 120 (20), pp.205108. ⟨10.1063/1.4968532⟩. ⟨hal-03276235⟩

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