Chemical Bath Deposition and characterization of CdS – PbS thin films.

CdS–PbS thin films have been deposited on glass substrates by the chemical bath deposition technique. Cadmium sulphide thin layer was first deposited on glass substrate from a solution of cadmium chloride (CdCl2) and thiourea (NH2CSNH2) with triethanolamine (TEA) as complexing agent. CdS – PbS films were obtained by depositing lead sulphide (PbS) films on the CdS – coated glass substrates from a solution of lead nitrate [Pb(NO3)2] and thioacetamide NH3CSNH2. Complexing agent again was TEA while in both cases aqueous ammonia (NH3) created the necessary alkaline medium for the reaction to take place. The energy dispersive X – ray fluorescence (EDXRF) analysis confirmed the composition of the CdS and PbS thin films. Optical measurements were performed with a single-beam UNICAM Heλ 105 Spectrophotometer in the wavelength range of 195nm – 1000nm. The optical transmittance of CdS-PbS films is extremely low, in most cases zero within the UV and first half of the visible region but peaked at 49.4% (at λ = 994nm) for the 150oC air-annealed samples and at 44.7% (at λ = 994nm) for the as grown samples in the near infra-red region. The absorbance is infinitely large in the UV and first half of the visible regions for both as-deposited films and annealed films, respectively but falls exponentially between the second half of the visible and near infra-red regions. The films have peak reflectance within the visible region. The films showed good characteristics for deployment not only as UV filters but also in solar control coating applications.Keywords: Chemical bath, CdS, PbS, Thin Films, transmittance

Chemical bath deposition and characterization of PbS – Cu

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