Thermoelectric properties of cobalt–antimonide thin films prepared by radio frequency co-sputtering

• Polycrystalline Co–Sb thin films were obtained by present deposition strategy.
• CoSb2 and CoSb3 have semimetal and semiconductor characteristics respectively.
• The Seebeck coefficient depends heavily on defect concentration and impurity phases.
• Film properties in the second heating cycle were different from the first.
• CoSb2 is found to possess significant n-type thermopower.

Co–Sb thin films with an Sb content in the range 65–76 at.%, were deposited on a thermally oxidized Si (100) substrate preheated at 200 °C using radio-frequency co-sputtering. Evaluation using scanning electron microscopy images and X-ray diffraction reveals that the films were polycrystalline, with a grain size in the range 100–250 nm. Energy-dispersive spectroscopy analysis indicates single-phase CoSb2 and CoSb3 films, as well as multiphase thin films with either CoSb2 or CoSb3 as the dominant phase. The electrical and thermoelectric properties were measured and found to be strongly dependent on the observed phases and the defect concentrations. The CoSb2 thin films were found to exhibit a significant n-type thermoelectric effect, which, coupled with the very low electrical resistivity, resulted in a larger power factor than that of the CoSb3 thin films. We find power factors of 0.73 mWm− 1 K− 2 and 0.67 mWm− 1 K− 2 for the CoSb2 and CoSb3 thin films, respectively.