Effect of thermal annealing and cooling rate on CBD grown CdS thin films

CdS films were deposited by CBD on a glass substrate by using CdI₂ as a Cd⁺ source, thiourea as an S⁻ source and NH₄OH as the complexing agent. The effect of slow and rapid cooling on the films after thermal annealing was investigated in the present study. X-ray diffraction and Raman spectra of the films suggest that thermal annealing followed by slow cooling gives CdS with enhanced crystallinity and reduced strain and dislocation density as compared to the films where they were cooled rapidly after thermal annealing. The results were supported by scanning electron microscopy and UV–Vis absorption spectroscopy. Hall Effect measurement shows the lowest resistivity and highest mobility obtained in the case of a slowly cooled sample as compared to the rapidly cooled sample. Carrier concentration in the range of about 10¹¹ (cm⁻³) was found, and all the samples of CdS were of n-type conductivity.