SnS absorber thin films by co-evaporation: Optimization of the growth rate and influence of the annealing

Abstract Tin sulfide thin films were prepared by co-evaporation on soda-lime glass substrates, for use as absorber layers. The synthesis was carried out at 350 °C substrate temperature and varying the growth rate in the 2–6 A/s range, adjusting the deposition time in order to obtain thicknesses in the 700–1500 nm range. After evaporation, the samples were heated at 400 °C and 500 °C under various atmospheres. The evolution of the morphological, structural and optical properties has been analyzed as a function of the thickness and deposition rate, before and after annealing. For the samples grown at the lowest rate, SnS and Sn 2 S 3 phase mixing has been observed by X-ray diffraction. Samples with reduced thickness preferably crystallize in the SnS phase, whereas thicker layers become richer in the Sn 2 S 3 phase. The sulfur treatment of samples prepared at the lowest rate results in the formation of SnS 2 phase. Otherwise, the samples obtained at the highest rates show single-phase SnS after heating at 400 °C in sulfur atmosphere, with gap energy values around 1.24 eV.