Cubic, orthorhombic and amorphous SnS thin films on flexible plastic substrates by CBD

Abstract

Tin sulfide (SnS) thin films were successfully deposited on acetate plastics substrates by chemical bath deposition at 70 °C by 2 h varying the pH value. SnS films exhibited good adherence, compact and uniform. X-ray diffraction (XRD) results showed that it is possible to obtain cubic, amorphous, and orthorhombic crystalline structures for SnS films depending on the pH value in a range from 8.24 to 10.93. Scanning electron microscopy (SEM) analysis revealed a morphological transformation of SnS films from spherical shape to flakes shape for cubic and orthorhombic structures, respectively. The pH variation influences on SnS films stoichiometry, for low pH the S/Sn ratio is 0.15 while for pH around of 10.45 the S/Sn ratio is 0.90 which is near-stoichiometric. Raman studies confirm SnS vibrational modes associated with cubic and orthorhombic structure. Optical properties also were modified varying the pH and the absorption coefficients are larger than 104 cm−1 for all SnS films deposited on acetate plastic substrates. The band gap values were obtained from 1.08 to 1.72 eV and associated with cubic, amorphous, and orthorhombic SnS. The results suggest that it is possible to modify the crystalline structure, band gap, and S/Sn ratio varying the pH value, and this work promotes the application of SnS in flexible devices.