Effect of deposition potential and bath temperature on the electrodeposition of SnS film

SnS films were cathodically electrodeposited on ITO glass substrates from aqueous solution containing 5 mmol/L SnSO4 and 25 mmol/L Na2S2O3 with pH 2–3 under different deposition potential (E) and bath temperature. The deposited films were characterized with X-ray diffractograms, microstructure, composition analysis and optical measurement. When the bath temperature was kept at room temperature (30 °C) and E was varied from −0.60 to −1.1 V (vs SCE), it was found that, the composition ratio Sn/S of the films varied with E, the ratio Sn/S significantly increased and exceeded 1 at the potential more negative than −0.80 V (vs SCE), and the ratio Sn/S significantly decreased and was less than 1 at the potential more positive than −0.70 V (vs SCE). The nearly stoichiometric SnS films with the composition of Sn0.99S1.01 ∼ Sn1.01S0.99 were synthesized at −0.72 to −0.75 V (vs SCE), and they were polycrystalline with orthorhombic structure and had good uniformity and good adhesion to the substrate. When E was kept at −0.72 to −0.75 V (vs SCE) and the bath temperature varied from 30 to 50 °C, it was found that the atomic ratio Sn/S of the film still approached to its ideal ratio 1/1 and it was seldom influenced by the bath temperature, but the increase of the temperature improved the crystallinity of the deposit and made the direct energy gap Eg become smaller (from 1.48 to 1.24 eV).