Superior Thermoelectric Performance of SiGe Nanowires Epitaxially Integrated into Thermal Micro-Harvesters |
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Authors: | Jose Manuel Sojo-Gordillo Carolina Duque Sierra Gerard Gadea Diez Jaime Segura-Ruiz Valentina Bonino Marc Nuñez Eroles Juan Carlos Gonzalez-Rosillo Denise Estrada-Wiese Marc Salleras Luis Fonseca Alex Morata Albert Tarancón |
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Affiliation: | 1. Department of Advanced Materials, Catalonia Institute for Energy Research (IREC), Jardins de Les Dones de Negre 1, Sant Adrià de Besòs, Barcelona, 08930 Spain;2. Beamline ID-16B, ESRF: The European Synchrotron, 71, Avenue des Martyr, Grenoble, 38043 France;3. Institute of Microelectronics of Barcelona, IMB-CNM (CSIC), C/Til⋅lers s/n (Campus UAB), Bellaterra, Barcelona, 08193 Spain |
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Abstract: | Semiconductor nanowires have demonstrated fascinating properties with applications in a wide range of fields, including energy and information technologies. Particularly, increasing attention has focused on SiGe nanowires for applications in a thermoelectric generation. In this work, a bottom-up vapour-liquid-solid chemical vapour Deposition methodology is employed to integrate heavily boron-doped SiGe nanowires on thermoelectric generators. Thermoelectrical properties –, i.e., electrical and thermal conductivities and Seebeck coefficient – of grown nanowires are fully characterized at temperatures ranging from 300 to 600 K, allowing the complete determination of the Figure-of-merit, zT, with obtained values of 0.4 at 600 K for optimally doped nanowires. A correlation between doping level, thermoelectric performance, and elemental distribution is established employing advanced elemental mapping (synchrotron-based nano-X-ray fluorescence). Moreover, the operation of p-doped SiGe NWs integrated into silicon micromachined thermoelectrical generators is shown over standalone and series- and parallel-connected arrays. Maximum open circuit voltage of 13.8 mV and power output as high as 15.6 µW cm−2 are reached in series and parallel configurations, respectively, operating upon thermal gradients generated with hot sources at 200 °C and air flows of 1.5 m s−1. These results pave the way for direct application of SiGe nanowire-based micro-thermoelectric generators in the field of the Internet of Things. |
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Keywords: | integration micro/nano-generators nanowires silicon-germanium thermoelectric tip-enhanced Raman spectroscopy X-ray fluorescence |
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