Structural and optical properties of CdS thin film obtained by chemical bath deposition and effect of annealing

Abstract

Cadmium sulphide (CdS) thin film was deposited on glass substrate by chemical bath deposition (CBD) by single dip method. The bath-temperature was at 80°C and pH at 11. The film was annealed in air at 300°C for one hour. The as-deposited and annealed films were characterized by XRD, UV-visible spectrophotometer, EDAX and photoluminescence study. The film-thickness of 391.1 nm was revealed by Ellipsometry. Coexistence of hexagonal and cubic structure of the as-deposited film was confirmed by XRD. On annealing, the film was confirmed to be purely hexagonal. The band gaps of 2.35 eV of the as-deposited film and 2.29 eV of the annealed film were derived from the optical transmittance data of UV-VIS spectrum. Photoluminescence (PL) spectrum of the CdS thin film exhibits green and red emission peaks with different intensity on annealing. EDAX spectrum confirms the transformation of CdS thin film from off-stoichiometric to near stoichiometric state on annealing.