Influence of [S2O3]/[Sm] on Sm2S3 thin films deposited by liquid phase deposition method on self-assembled monolayers

Sm₂S₃ thin films were prepared on Si (1 0 0) substrates using SmCl₃ and Na₂S₂O₃ as precursors by liquid phase deposition method on self-assembled monolayers. The influence of the molar concentration ratio of S₂O₃²⁻]/Sm³⁺] on the phase compositions, surface morphologies and optical properties of the as-deposited films were investigated. The as-deposited Sm₂S₃ thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), ultraviolet-visible (UV-vis) and photoluminescence spectrum (PL). Results show that it is important to control the S₂O₃²⁻]/Sm³⁺] during the deposition process and monophase Sm₂S₃ thin films with orientation growth along (0 1 1) direction can be achieved when S₂O₃²⁻]/Sm³⁺] = 2.0, pH 3.0, with citric acid as a template agent. The as-deposited thin films exhibit a dense and crystalline surface morphology. Good transmittance in the visible spectrum and excellent absorbency of ultraviolet light of the thin films are observed, and the band gap of the thin films first decrease and then increase with the increase of the S₂O₃²⁻]/Sm³⁺]. The as-deposited thin films also exhibit red photoluminescence properties under visible light excitation. With the increase of the S₂O₃²⁻]/Sm³⁺] in the deposition solution, the PL properties of Sm₂S₃ thin films are obviously improved.