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A5: Nanoscale and low dimensional effects
Among the different strategies employed nowadays to improve the thermoelectric properties of materials and the efficiency of the direct conversion of thermal to electric energy and vice-versa, one of the most encouraging is the use of nanostructure engineering. For instance, it has been shown by Mingo et al [1] that for a SiGe matrix, the inclusion of metallic silicides nanodots (like TiSi2 and MoSi2) causes an up to four-fold reduction of the material’s thermal conductivity without further changes on its electrical conductivity and Seebeck coefficient. On this work we studied the growth of QDSLs (Quantum Dots Super Lattices) made of TiSix and MoSix nano inclusions (20-40nm) on a doped SiGe matrix. These materials were produced using an industrial CVD tool adapted for the use of liquid and solid precursors. The size and the fraction of the nanoparticles inside the matrix were chosen according to the studies of Mingo et al. To our knowledge it is the first time that these materials were produced. The role of deposition parameters such as time, temperatures and precursor gas flows on the nanodots size and density was thoroughly studied both for the Ti and Mo based nanodots. Different characterization techniques were employed to analyze the structure of the QDSLs produced such as SEM, TEM and XRD, and to measure the thermoelectric properties (electrical conductivity, Seebeck coefficient and thermal conductivity. These results were interpreted and a discussion linking the physical properties and the corresponding thermoelectric characteristic of these materials was performed
[1] N. Mingo, D. Hauser, N. P. Kobayashi, M. Plissonnier, et A. Shakouri, « “Nanoparticle-in-Alloy” Approach to Efficient Thermoelectrics: Silicides in SiGe », Nano Lett., vol. 9, no. 2, p. 711-715, 2009