Influence of Chemical Bath Deposition Temperatures on Cadmium Sulphide Thin Film and Photosensor Application
Abstract
Cadmium sulphide (CdS) thin films were deposited on commercial glass substrates by the chemical bath deposition (CBD) method using cadmium chloride (CdCl2.H2O), thiourea (SC(NH2)2), ammonium chloride (NH4Cl), ammonium hydroxide(NH4OH), and deionised water. The sulphur to cadmium molar ratio (S/Cd) was 2.89, and deposition time (50 minutes) was fixed during the depositions. The optical, structural, morphological, and photoelectric properties of these prepared CdS thin films were studied at different deposition temperatures, which varied between 50 to 80℃. Optical spectra showed the transmittance, up to 70 to 85%, and a band-gap of 2.83 to 2.4 eV within the temperature range used in the present studies. X-ray diffraction patterns revealed the hexagonal phase of all synthesised CdS thin films with a (002) orientation and temperature-dependent intensity variation. The measured crystallite size ranged from 42 to 63nm. The distribution of spherical grains throughout the substrate was seen in Field Emission Scanning Electron Microscopy (FESEM) micrographs. As the deposition temperature increased from 60 to 80°C, the photoelectric resistance of the CdS film under light illumination significantly decreased from 108 to 107Ω. With rise and decay time constants, the CdS film deposition at 80°C demonstrated a considerable photoresponse, making it appropriate for photosensor applications.
