Thermal stability of thermoelectric CoSb3 skutterudite thin films

•Films with slight excess Sb are thermally more stable than stoichiometric CoSb3 films.•Sb outgassing during annealing is increased for stoichiometric films.•The decomposition temperature varies with composition.•The electric properties of films with excess Sb saturate for longer annealing times.•Films with excess Sb show no changes of electric property during thermal cycling.

The skutterudite CoSb3 exhibits promising properties for future thermoelectric applications and its efficiency can be even enhanced by using thin film technology. However, the thermal stability of these films has to be guaranteed up to the working temperature. In this study, the structural and electrical properties were investigated in dependence of annealing temperature and annealing time for room temperature deposited 30 thick Co–Sb films with two different initial compositions (75 at.% Sb and 77 at.% Sb). It was shown that an excess of Sb stabilizes the CoSb3 skutterudite phase. Furthermore, resistivity measurements during thermal cyclings were performed and no changes in resistivity were obtained as long as the temperature was kept below the initial annealing temperature.