Structural properties of thermoelectric CoSb3 skutterudite thin films prepared by molecular beam deposition

The research field of thermoelectricity was renewed by the progress made in nanostructuring approaches and by the investigation of new material groups as skutterudites, whose most promising representative is CoSb3. In this work Co-Sb thin films with a thickness of 30 nm were deposited by molecular beam deposition at different substrate temperatures as well as on non-heated substrates followed by a post-annealing step. An extended investigation of the phase formation in dependence of deposition method and parameters, film composition, and post-treatment is given. The presented results provide different routes to achieve high quality single phase films. It was also demonstrated that the grain size of the CoSb3 thin films is very sensitive to the used deposition method and especially on the substrate temperature during deposition. A controllable grain size by changing the deposition parameters could be a key feature for the optimization of the thermoelectric properties, since especially the thermal conductivity should strongly depend on the grain size due to enhanced grain boundary scattering of phonons.