Dresden 2011 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 59: Thermoelectric Materials, Thin Films, and Nanostructures I (Focused Session -- Organisers: Nielsch, Rastelli, Balke)

DS 59.1: Topical Talk

Freitag, 18. März 2011, 11:00–11:30, GER 37

Nanocrystalline silicon for thermoelectricity — •Gabi Schierning — Center for NanoIntegration Duisburg-Essen (CeNIDE), University of Duisburg-Essen, 47057 Duisburg, Germany

A main focus in thermoelectricity is on the development and utilization of materials with high availability and sustainability. From this point of view, nanocrystalline silicon is a potential candidate for thermoelectric application, motivating the effort of optimizing its thermoelectric properties. In the first part of the talk, an overview over silicon-based thermoelectrics will be given.

In the second part of the talk, own work will be presented. Our bottom up approach starts with tailored silicon nanoparticles from a gas phase process. Compaction of the nanopowder is done by a dc-current sintering. In a combined experimental and theoretical work it is shown how the developing microstructure during sintering correlates to the percolation paths of the current through the powder. Observed density fluctuations on the micrometer scale are attributed to the specific heat profile of the simulated powder networks.

It is technologically highly demanding to exclude any contamination of the nanopowder with oxygen and moisture. As a result, a Si/SiO₂ core/shell structure is always observed for nanocrystalline silicon powders having been in contact with air. In the sintered body, the initial core shell structure is dissolved. Instead, oxidic precipitates have formed during sintering. The role of these oxidic precipitates with respect to the sintering mechanism and the thermoelectric transport properties will be discussed.