Influence of growth conditions on the electrochemical synthesis of SnS thin films and their optical properties

Tin sulfide(SnS) thin films were prepared by electrodeposition onto fluorine-doped tin oxide(FTO) glass substrates using an aqueous solution containing SnC l2and Na2S2O3at various deposition potentials(E) and bath concentrations. The pH value and temperature of the solution were kept constant. The deposited films were characterized using X-ray diffraction(XRD), field-emission scanning electron microscopy(FESEM), photoluminescence(PL), and ultraviolet–visible(UV–Vis) spectroscopy. The FESEM images demonstrated that changes in the deposition potential(E) and solution concentration led to marked changes in the morphology of the deposited SnS films. Energy-dispersive X-ray analysis(EDXA) results showed that the Sn/S atomic ratio strongly depended on both the solution concentration and the deposition potential. To obtain an Sn/S atomic ratio approximately equal to 1, the optimal Sn<sub>2+/S2O2-3molar ratio and E parameter were 1/8 and-1.0 V, respectively. The XRD patterns showed that the synthesized SnS was obviously polycrystalline, with an orthorhombic structure. The effects of the variations of bath concentration and deposition potential on the band-gap energy(Eg) were studied using PL and UV–Vis experiments. The PL spectra of all the SnS films contained two peaks in the visible region and one peak in the infrared(IR) region. The UV–Vis spectra showed that the optical band-gap energy varies from 1.21 to 1.44 eV.