Enhancing the thermoelectric properties of Ca3Co4O9 thin films by Nb ion injection

•High quality Ca3Co4O9 thin films have been epitaxially grown on single crystal Al2O3 substrate.•Nb element was implanted into Ca3Co4O9 thin film by ion beam injection technique.•The effect of Nb doping was verified by resistivity measurement at room temperature.•Resistivity and Seebeck coefficient were measured in the temperature range 150–380 K.•The power factors of Ca3Co4O9 thin films increase when Nb doped.

High quality Ca3Co4O9 thin films have been grown epitaxially on single crystal Al2O3 substrates with pulsed laser deposition. Nb was implanted into the Ca3Co4O9 films using an ion beam injection technique. The microstructure of the thin films has been investigated by XRD, SEM and AFM. The epitaxial thin films were grown with the c-axis perpendicular to the substrate surface. The effect of Nb doping by ion beam injection was verified using resistivity measurements at room temperature. Resistivity and the Seebeck coefficient were also measured in the temperature range 150–380 K. The results indicate that the power factors of Ca3Co4O9 thin films increase when doped with Nb. When the concentration of doped Nb was 3.65 × 1019 atoms/cm3, the power factor of the thin films reached 0.10 mW/m K2 at room temperature, and it approached a maximum of 0.17 mW/m K2 at 380 K.