Influence of [S2O32−]/[Sm3+] on Sm2S3 thin films deposited by liquid phase deposition method on self-assembled monolayers

Abstract

Sm2S3 thin films were prepared on Si (100) 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 (011) 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.