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چکیده
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CdS is a direct band gap semiconductor and has relatively high absorption coefficient and high optoelectronic conversion efficiency and has been studied extensively in the deposition (CBD), laser ablation, sputtering, and vacuum evaporation [2].Among them, chemical bath deposition (CBD) is a simple and inexpensive method for a deposition of thin films of various semiconductors at low temperature on different types of substrates [3]. Nanocrystalline cadmium sulfide CdS thin films with relevance for optical applications were synthesized from aqueous solutions by chemical bath deposition. This work deals with the preparation of cadmium sulfide (CdS) thin films by chemical bath deposition. The energy band gap (Eg) was calculated from absorption coefficients obtained from the optical transmittance. CdS thin films have been deposited on the glass substrates using CBD method. Stock solutions of 10ml cadmium acetate dehydrate (0.5M), 20ml ethylenediamine (0.5M) such as complexing agent was added to control the release of the cadmium ions.The temperature of the chemical bath was 50°C and the pH was adjusted to 7. The morphology of the thin films were studied by a Cam Scan MV 2300 scanning electron microscope (SEM) and transmission spectra were measured using UV/ VIS Cary (Varian) spectrophotometer. The nanocrystalline thin films of CdS were successfully deposited by chemical bath deposition method. The transmittance spectral shifts are explained based on grain size effects. The obtained films werehomogeneous, strongly adherent and uniform surface with very low pinholes well covered to the substrate.The transmittance spectral shifts are explained based on grain size effects. The films with shorter deposition time have a higher transmittance at shorter wavelength.The band gap measuredwas found to be in the range of 2.7 - 3.2 eVwhich leads this semiconductor to act as an optical window in photovoltaic cells.
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