Co distribution through n-type pyrite thin films

Formation of n-type pyrite thin films has been obtained by direct sulphuration from metallic Fe–Co bilayers of atomic ratio Fe/Co ∼ 2.5, at temperatures between 250 °C and 500 °C. Pyrite structure is observed by X-ray diffraction measurements (XRD). Composition depth profile has been studied by Rutherford Backscattering Spectroscopy (RBS). Three different zones can be observed: a non-diffused Co layer near the substrate, a FeS2 layer with homogeneous diffusion of Co, and a Co-rich FeS2 layer on the surface. Co content seems not to be dependent on the sulphuration temperature. Electrical characterization gives values from − 17.4 ± 0.9 μV/K to − 67 ± 4 μV/K for the Seebeck coefficient and from (3.7 ± 0.2)·10− 3 to (2.1 ± 0.1)·10− 2 Ω cm for the resistivity, as sulphuration temperature is increased. Transport properties are compared with those of non-doped films and the Co distribution through the films will be analysed.