M. Kockert^a, R. Mitdank^a, H. Moon^b, J. Kim^c, A. Mogilatenko^d, S.H. Moosavi^e, M. Kroener^e, P. Woias^e, W. Lee^b and S.F. Fischer^a

Published in:

Nanoscale Adv., vol. 3, no. 1, pp. 263-271, doi:10.1039/D0NA00658K (2021).

Abstract:

We demonstrate the full thermoelectric and structural characterization of individual bismuth-based (Bi-based) core/shell nanowires. The influence of strain on the temperature dependence of the electrical conductivity, the absolute Seebeck coefficient and the thermal conductivity of bismuth/titanium dioxide (Bi/TiO₂) nanowires with different diameters is investigated and compared to bismuth (Bi) and bismuth/tellurium (Bi/Te) nanowires and bismuth bulk. Scattering at surfaces, crystal defects and interfaces between the core and the shell reduces the electrical conductivity to less than 5% and the thermal conductivity to less than 25% to 50% of the bulk value at room temperature. On behalf of a compressive strain, Bi/TiO₂ core/shell nanowires show a decreasing electrical conductivity with decreasing temperature opposed to that of Bi and Bi/Te nanowires. Wefind that the compressive strain induced by the TiO₂ shell can lead to a band opening of bismuth increasing the absolute Seebeck coefficient by 10% to 30% compared to bulk at room temperature. In the semiconducting state, the activation energy is determined to ❘41.3±0.2❘ meV. We show that if the strain exceeds the elastic limit the semimetallic state is recovered due to the lattice relaxation.

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