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DS: Fachverband Dünne Schichten

DS 14: Thermoelectric Thin Films and Nanostructures II

DS 14.1: Topical Talk

Dienstag, 23. März 2010, 14:00–14:30, H8

Thermal Conductivity of Thermoelectric Materials Embedded with Nanoparticles — •Yee Kan Koh and David Cahill — Dept. of Materials Sc. and Eng., University of Illinois, Urbana, USA

Over the past decade, nanostructures are prevalently explored to reduce the thermal conductivity of existing thermoelectric materials and hence enhance the thermoelectric efficiency. In this regard, nanoparticles or nanodots embedded in a matrix could be effective in scattering phonons and thus reducing the thermal conductivity. We report here our thermal conductivity measurements of two important classes of thermoelectric materials, i.e., InAlGaAs embedded with ErAs nanoparticles and PbTe/PbSe nanodot superlattices (NDSLs). The samples are grown by our collaborators at UC Santa Barbara and MIT Lincoln Laboratory. We measured the thermal conductivity by time-domain thermoreflectance. From our measurements, we found that reduction of the thermal conductivity by ErAs nanoparticles is less significant in InAlGaAs than in InGaAs. By measuring TDTR in frequency domain, we showed that 3% of ErAs nanoparticles is sufficient to scatter phonons with mean-free-paths of 300-1000 nm. In contrast to InAlGaAs, we found that PbSe nanodots do not reduce the thermal conductivity of NDSLs below the alloy limits. All of our measurements approach the thermal conductivity of bulk homogenous alloys with the same average composition. We attribute this observation to short mean-free-paths of phonons in PbTe and small acoustic impedance mismatch between PbTe/PbSe. Our work provides guidelines for future work on thermoelectric materials embedded with nanoparticles.