Dependence of pH on phase stability, optical and photoelectrical properties of SnS thin films

Abstract

This study reports the effect of pH value of the reaction solution (5, 5.8 and 6.5) on growth rate of SnS films deposited by chemical bath deposition and their characteristics such as X-ray diffraction (XRD), surface morphology, phase stability, optical and photoelectrical. XRD analysis reveals that the films exhibit an orthorhombic structure with polycrystalline nature, in addition to the presence of the secondary phase Sn2S3 at pH 6.5. Field emission scanning electron microscopy observations show the formation of nanoflowers. Raman spectra manifest the presence of Sn2S3 phase, where its peak intensity gradually reduces until disappearance with decreasing pH value from 6.5 to 5. Furthermore, the enhancement in the dark current (conductivity) value of the thin films occurs with decreasing pH value, as well as increasing in the value of photocurrent under illumination of near-infrared 750 nm. Conversely, the sensitivity value decreased with decreasing pH. Moreover, the energy gap value ranges from 1.34 to 1.51 eV with increasing pH. The as-obtained results demonstrate the key role of pH in controlling SnS films characteristics to achieve high quality films for the applications of photodetectors and solar cells.