ICT2014 Abstracts

The ongoing miniaturization of thermoelectric modules requires scaling down to thin films of TE materials with high efficiency. In search for such materials, thin films of Mg₂(Si,Sn) solid solutions have been deposited on SiO₂/Si, glass and Ni substrates by microwave plasma-assisted co-sputtering method with a fine control over their stoichiometry. The types of substrates were chosen based on the particularities of a thermoelectric module which comprises both electrodes and insulators. The thermo-mechanical properties and thermal stability of the thin films have been investigated after intermediate temperature thermal treatments. It is shown that the deposition process, as well as the substrates on which the films are grown, determine the subsequent adherence of the films. Also, the metastability of the chosen solid solution leads to a separation into 2 phases at intermediate temperatures that stabilize after the first annealing treatment (623 K). The impact of this phase separation has been ascertained by characterizing the thermoelectric properties (electrical conductivity, Seebeck coefficient) of the films both for as-deposited single-phase and post-annealing 2-phase thin films. Furthermore, by increasing the temperature of the thermal treatment (773 K), the decomposition of the material is observed, thus establishing the functional temperature range for these solid solutions as thin films.