Redshift in Absorption Edge of Cd $_{bm{{1-x}}}$ Co $_{bm{{x}}}$ S Nanofilms

Cd_1-xCo_xS nanofilms (0 ≤ x ≤ 0.08) deposited by chemical bath deposition have been studied using energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and ultraviolet-visible-near-infrared spectroscopy. A redshift in Cd-S stretch with Co doping has been observed. The incorporation of Co²⁺ ions in CdS lattice deteriorates the large crystallites with an increase in grain boundaries. A redshift in absorption edge has also been observed with Co concentration. This shift may be explained on the basis of band tailing due to creation of defect states. The optical behavior of Cd_1-xCo_xS nanofilms has been analyzed in term of Tauc model, Urbach-Martienssen model, and Vegard´s law.