Role of cation diffusion in the formation mechanism and properties of cobalt-doped n-type pyrite thin films

Binary and ternary chalcogenides are relevant compounds for photovoltaic and thermoelectric energy conversion processes. The prototype material in this wide family is FeS2 (pyrite). In this work, we have investigated the simultaneous formation and doping (n-type) of FeS2 thin films. Sulphuration of Fe over Co metallic bilayers at constant pressure and temperature has allowed to get the necessary experimental information. Through the analysis of the chemical composition (Rutherford backscattering/elastic recoil detection analysis, energy dispersive X-ray) and structural (XRD) experimental data we have been able to propose a detailed mechanism to explain the formation of pyrite doped with Co thin films. In this mechanism the most relevant role is played by the diffusion of cationic (Fe and Co) species. Measured transport properties of the films reflect the different steps of the formation and doping processes.