Preparation and thermoelectric properties of CoSb3 thin films on GaAs(100) substrate

The thin film growth of CoSb₃ on a semi-insulating GaAs(100) substrate was made by using magnetron rf-sputtering, and the electrical and thermoelectric properties of the films were studied with relation to annealing temperature and film thickness. Polycrystalline films with the skutterudite structure were successfully grown on the GaAs(100) substrate. The obtained films were found to be p-type, and their hole mobility, electrical conductivity, and Seebeck coefficient significantly changed depending on the annealing temperature and the thickness. A huge Seebeck coefficient of 600 μV/K, which is about three times as large as the value of a p-type single crystal, was obtained for a thin film annealed at 750°C with thickness of 71 nm, and the power factor reached the value of 2×10^-4 W/cm K ². The variation in the thermoelectric properties with the annealing temperature and the thickness can be explained well in terms of a model which takes into account a carrier energy filtering effect by potential barriers at grain boundaries. According to the model, the Seebeck coefficient increases with increasing potential barrier height and also decreases with increasing carrier concentration