Structural and optical investigations on CdS thin films grown by chemical bath technique

Cadmium sulphide (CdS) thin films have been prepared by using a chemical ba th deposition (CBD) method. Structural analysis (XRD and TEM) revealed that the films showed hexagonal structure with lattice constants a=0.4015 nm an d c=0.6545 nm. On annealing, the films exhibited secondary phase of beta -C dS (cubic) along with hexagonal phase, but density of dislocations decrease d. The stacking faults have been observed in the crystalline arrangement by high resolution transmission electron microscopy (HRTEM). The direct band gaps of as-grown and annealed films were found to be 2.42 and 2.62 eV with sub band gap of 2.35 eV, respectively, which were confirmed by optical anal ysis. On annealing, the resistivity of the films decreased from 3 x 10(6) t o 1 x 10(3) Omega cm. Multiple Cd and S defects were observed by employing photoluminescence (PL) method. The intensities of emission peaks for anneal ed films differed with that of as-grown films. As was discussed with giving reasons. (C) 2001 Elsevier Science B.V. All rights reserved.