Modifications in SnS thin films by plasma treatments

The present study shows the modifications of structural, optical and electrical characteristics that occur in tin sulfide (SnS) thin films treated in air and in nitrogen plasma at different pressure conditions. The films were obtained by the chemical bath deposition method, which results in SnS thin films with an orthorhombic crystalline structure, band gap (Eg) of 1.1–1.2 eV, and electrical conductivities (σ) in the order of 10−6 Ω−1cm−1. The films treated with air plasma at pressures between 1 and 4 Torr, showed the presence of SnS2, Sn2S3, and SnO2 phases, within the band gap values ranging from 0.9 to 1.5 eV. On the other hand, the films treated with nitrogen plasma presented the same phases, but showed a significant modification in the electrical conductivity, increasing from 10−6 Ω−1cm−1 (as-deposited) up to 10−2–10−3 Ω−1cm−1 (plasma treated). This result is a suitable range of conductivity for the improvement of the solar cells with SnS as an absorber material. Also, emission spectroscopy measurements were carried out in both air and nitrogen plasma treatments.