Mg-Ag-Sb thin films produced by solid-state reactive diffusion

Abstract

α -MgAgSb is a tellurium-free thermoelectric material that exhibits good thermoelectric properties near room temperature. Being made of relatively abundant elements compatible with the complementary metal oxide semiconductor (CMOS) technology, it is considered as a possible solution for the development of high-efficiency thermoelectric devices for heat waste harvesting in microelectronic setups. This study presents a first attempt to investigate the structural properties of MgAgSb thin films prepared by solid-state reactive diffusion. X-ray diffraction (XRD) was used to follow phase formation in thin films, first, in the case of the binary Ag 3 Sb and Mg 3 Sb 2 compounds, and then, in the case of the ternary system Mg-Ag-Sb. For the later, in situ XRD was used to follow real-time phase formations during the reaction of the bilayerAg 3 Sb/Mg 3 Sb 2 . The results show that the phase α -MgAgSb can be produced by reactive diffusion at the interface of the bilayer. Furthermore, the three phases α , β , and γ are shown to coexist at 360 °C, which can be the result of the thin film geometry (surface and interface effects) or due to a different stoichiometry between these three phases contrasting with usual belief. At temperatures higher than 450 °C, γ -MgAgSb is the only phase stabilized in the film. This study serves as a benchmark for the production of pure α -MgAgSb thermoelectric thin films by reactive diffusion.