Formation of solid solutions via solid-state lead diffusion in chemically deposited CdS films

Highlights: • The formation of Cd_xPb₁ – _xS due to the exchange process is thermodynamically possible. • Thin-film solid solutions of CdS-PbS with variable composition were obtained. • Time and temperature of the exchange process affect the lead content of the films. • The effective coefficient of lead diffusion in a CdS film was calculated. - Abstract: Substitutional solid solutions in the CdS–PbS system were obtained by aging of chemically deposited cadmium sulfide thin film in an aqueous solution of lead acetate Pb(C₂H₃O₂)₂. By using the thermodynamic calculations a possibility of proceeding of a heterogeneous ion-exchange reaction at the interface "chemically deposited CdS film/lead salt aqueous solution" was estimated. The effect of solid-state diffusion on the morphology, composition, and optical properties of the CdS films was investigated. By means of X-ray photoelectron spectroscopy with layer-by-layer sputtering, the chemical composition across the obtained films thickness was analyzed, and concentration depth profiles of the elements were plotted. The coefficient of the lead diffusion into the cadmium sulfide film during its ion-exchange transformation was calculated.