Structural properties of thermoelectric skutterudite [formula omitted] gradient films fabricated by modulated elemental reactant method

Abstract

The interest in using energy sources more efficiently has boosted the research activities in the field of thermoelectricity. Lowering the thermal conductivity of existing thermoelectric materials as the skutterudite CoSb3, is one way to improve their thermoelectric properties. Especially for gradient films a strong decrease of the phononic thermal conductivity is expected. In this work, the feasibility of this approach was investigated for FexCo1-xSb3 skutterudite thin films, which were prepared at room temperature on a Si(100) substrate using the modulated elemental reactant method (MERM) followed by post-annealing. First a homogenous single phase skutterudite film with constant Fe content x was deposited, for which the successful incorporation of Fe on the Co sites could be demonstrated. In a second step a cross-plane gradient film with varying x from 0 (bottom interface) to 0.5 (surface) was prepared and it was confirmed by Rutherford backscattering spectrometry and by secondary neutral mass spectrometry that the gradient can be maintained up to an annealing temperature of 400°C. This is a necessary condition for designing novel thermoelectric gradient films or multilayer structures based on skutterudites, which might provide a reduced thermal conductivity and thus an enhanced thermoelectric efficiency.