Chemical bath deposition and characterization of PbS – Cu<subx</sub>S thin films

Abstract

PbS and PbS - CuxS thin films have been deposited on glass substrates using the chemical bath deposition (CBD) technique. The PbS was  deposited from alkaline solution of lead nitrate, thioacetamide, ammonia and triethanolamine that was used as the complexing agent. The as-grown PbS was used as substrate to deposit CuxS thin films from alkaline solution of copper nitrate, thiourea, ammonia and triethanolamine that served also as the complexing agent. The energy dispersive X-ray  fluorescence (EDXRF) analysis confirmed the presence of Pb and S in the PbS thin films and Cu and S in the CuxS thin films. The absorbance of the annealed PbS films was about 70% in middle of the visible (vis) region. The PbS films also show transmittance as high as 54.5% and as low as 15% at 1000nm in the NIR. The peak reflectance in the vis region was 20%. The PbS – CuxS thin films showed minimum absorbance within the vis region (40% at 560nm and 45% at 720nm for the as-grown and annealed respectively) and a peak absorbance of 90% in the NIR  (1000nm). The effects of annealing on the optical constants of the films are discussed. Optical transitions are interpreted in terms of the direct band-to-band transitions.

Key words: PbS, CuxS, thin film, optical properties and chemical bath deposition.