STUDIES OF STRUCTURAL AND OPTICAL PROPERTIES OF LEAD SULFIDE THIN FILM AT DIFFERENT DEPOSITION TIME PREPARED BY CBD TECHINIQUE

Abstract

In this study, PbS thin films were deposited on glass substrates using the chemical bath deposition (CBD) technique. Lead acetate, thiourea, and sodium hydroxide were used as precursors for the Pb²⁺, S²⁻ source, and complexing agent, respectively. The deposition was carried out at a bath temperature of 80°C for varying durations of 20, 25, 30, 35, and 40 minutes. Following deposition, the films were annealed at 200°C for 90 minutes. The structural and optical properties of the films were characterized using X-ray diffraction (XRD) and UV-Visible spectroscopy. XRD analysis revealed that the as-deposited PbS films exhibited a nanocrystalline cubic (galena) structure with a face-centered cubic lattice, showing diffraction peaks corresponding to the (111), (200), (220), (222), (311), (400), (420), (331), and (422) planes, with a preferred orientation along the (200) plane. The crystallite size was estimated to increase from 33.27 nm to 37.50 nm as the deposition time increased. Additionally, both dislocation density and lattice strain decreased with increasing deposition time. Optical absorption measurements revealed strong absorption in the wavelength range of 500 nm to 750 nm. The optical band gap was reduced from 1.62 eV to 1.51 eV as the deposition time increased from 20 to 40 minutes in 5-minute intervals