Effect of tri-sodium citrate concentration on structural, optical and electrical properties of chemically deposited tin sulfide films

Graphical abstract: - Highlights: • SnS thin films grown by CBD in different concentration of tri-sodium citrate. • Grain size increases, while surface roughness decreases, with concentration. • Optical band gap decreases from 1.40 eV to 1.17 eV with increasing concentration. • Electrical conductivity improves with increasing concentration. - Abstract: Tin sulfide thin films were deposited onto glass substrates by chemical bath deposition. The effects of molar concentration of the complexing agent, tri-sodium citrate, on the structural, morphological, optical and electrical properties of the films were investigated. The films are characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy, optical absorption spectroscopy and Hall effect measurements. Polycrystalline film structure in orthorhombic phase was determined. Flower-like spherical grains are observed on the surface. While their average size increased from 345 nm to 750 nm when the tri-sodium citrate concentration was increased from 6.4 × 10⁻³ M to 8.0 × 10⁻³ M, the surface roughness varied in an opposite manner from approximately 120.18 nm to 29.36 nm. For these concentrations, optical band gap of the films decreased from 1.40 eV to 1.17 eV, whereas the Hall conductivity, mobility and carrier concentration of the films increased slightly from 5.91 × 10⁻⁵ to 8.78 × 10⁻⁵ (Ω cm)⁻¹, from 148 to 228 cm² V⁻¹ s⁻¹ and from 1.73 × 10¹² to 3.59 × 10¹² cm⁻¹, respectively