A series of CoSb3 thin films with Sb contents in the range 70-79 at.% were deposited at room temperature via RF co-sputtering. The thin films were amorphous in the as-deposited state and annealed at 300 degrees C for 3 h to obtain crystalline samples. The annealed thin films were characterized using scanning electron microscopy and X-ray diffraction (XRD), and these data indicate that the films exhibited good crystallinity. The XRD patterns indicate single-phase CoSb3 thin films in the Sb-rich samples. For the Sb-deficient samples, however, mixed-phase thin films consisting of CoSb2 and CoSb3 components were obtained. The electrical and thermoelectric properties were measured at temperatures up to 760K and found to be highly sensitive to the phases that were present. We observed a change in the thermoelectric properties of the films from p-type at low temperatures to n-type at high temperatures, which indicates potential applications as n-type thermoelectric thin films. A large Seebeck coefficient and power factor was obtained for the single-phase CoSb3 thin films. The CoSb2 phase thin films were also found to possess a significant Seebeck coefficient, which coupled with the much smaller electrical resistivity, provided a larger power factor than the single-phase CoSb3 thin films. We report maximum power factor of 7.92 mW/m K-2 for the CoSb2-containing mixed phase thin film and 1.26 mW/m K-2 for the stoichiometric CoSb3 thin film. (C) 2017 Elsevier B.V. All rights reserved.