Formation of Cu_2SnS_3 thin film by the heat treatment of electrodeposited SnS-Cu layers

摘要

Thin films of copper tin sulfide (Cu_2SnS_3) were obtained by sulfurizing a stack of thin layers of Cu and SnS in nitrogen atmosphere. The film stack was obtained by the sequential electrodeposition of SnS and Cu. The Cu_2SnS_3 film was characterized for structural, morphological, composition, optical, spectroscopic, and electrical properties. The optimum condition for the formation of Cu_2SnS_3 was developed after testing different sulfurization temperatures. The films were polycrystalline with monoclinic structure which was confirmed by Raman and transmission electron microscopy analysis. The interplanar spacings estimated from the high resolution transmission electron microscopy images are 2.74, 2.19, and 2.06 A. The average crystallite size is 13 nm, and the band gap of the film is in the range of 1 eV. The surface chemical composition determined by X-ray photoelectron spectroscopy showed the Cu:Sn:S ratio as 1.9:1:2.85 which is close to the stoi-chiometric Cu_2SnS_3. The films are p-type, photosensitive, and the conductivity measured in dark was in the range of 4 × 10~(-3) Ω~(-1) cm~(-1). The comprehensive characterization presented in this paper will update the knowledge on this material.