Berlin 2012 – scientific programme

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DS: Fachverband Dünne Schichten

DS 43: Thermoelectric materials V: Bulk materials (Focused session – Organizers: Meyer, Heiliger)

DS 43.2: Talk

Friday, March 30, 2012, 14:00–14:15, H 2032

Annealed CoSb₃ thin films on various substrates — Martin Friedemann, •Marcus Daniel, Gunter Beddies, and Manfred Albrecht — Institute of Physics, Chemnitz University of Technology, 09107 Chemnitz, Germany

Looking for new energy sources, thermoelectric becomes more and more important and especially CoSb₃ is a promising alloy for thermoelectric applications. Besides a high figure of merit, the thermal stability of the material has to be assured. Thermal treatment can yield to strain, cracks and formation of different crystal phases. During the annealing process of CoSb₃ thin films deposited on thermally oxidized Si substrates, cracks occur at the surface of the films. The reason for the cracks could be the difference of the thermal expansion coefficient of Si and CoSb₃. In this study, 40nm thick CoSb_x films have been deposited via MBE at room temperature onto substrates with different expansion coefficient in the range of 0,5 - 12 · 10⁻⁶ K⁻¹. The samples were post-annealed in ultra-high vacuum for one hour at 500^∘C. The composition of the films were checked by RBS before and after annealing. The samples show small differences in composition and the Sb content of the annealed samples is slightly lower than that of the initial ones. The phase formation was analysed by XRD, where CoSb₃ could be found as major phase. The surface morphology and the roughness of the films was investigated by AFM. For a substrate thermal expansion coefficient between 9 and 11 · 10⁻⁶ K⁻¹ crack formation could be prevented and a minima in roughness was found, resulting also in a minima of electric conductivity.