Optical, structural and morphological study of CdS nanoparticles: role of sulfur source

Cadmium sulfide (CdS) nanoparticles were synthesized by using a simple and low-cost home-made hot-injection method at a low process temperature using different sulfur (S) sources. The effects of sulfur concentration on the structural, morphological and optoelectronic properties of the synthesized cadmium sulfide films were studied using a range of characterization techniques: X-ray diffraction (XRD), Raman spectroscopy, field-emission scanning electron microscopy (FESEM) and ultraviolet–visible spectroscopy. The XRD studies revealed the formation of hexagonal-type cadmium sulfide nanoparticles. The varying morphology dependence on the sulfur source was ascertained from FESEM analysis. The longitudinal optical phonon vibrational modes of cadmium sulfide were assigned in Raman spectra at 300 and 600 cm⁻¹. The bandgap of the cadmium sulfide particles was estimated to be 2·30 eV from Tauc’s plots. Consistent with the experimental results, this study’s first-principles density functional theory calculations predict the bandgap of cadmium sulfide nanoparticles to increase with decreasing sulfur concentration – Cd₅₂S₅₂ (2·38 eV), Cd₅₂S₅₁ (2·52 eV) and Cd₅₂S₅₀ (2·65 eV) – with both the valence and conduction band edges demonstrated to be dominated by sulfur p states.