Temperature-dependent properties of electrochemically grown CdS thin films from acetate precursor

Abstract

Cadmium sulphide (CdS) thin films have been successfully deposited on glass/fluorine-doped tin oxide (glass/FTO) from an aqueous electrolyte solution containing cadmium acetate Cd(CH3COO)2 and sodium thiosulphate (Na2S2O3) using electrodeposition technique. The deposition electrolytic bath temperature was varied at 45, 65 and 85 °C. Two electrode system was applied and the corresponding structural, optical, morphological and compositional properties of these thin films have been characterized using X-ray diffraction, UV–Vis spectrophotometry, scanning electron spectroscopy, scanning probe microscopy and energy dispersive X-ray spectroscopy, respectively. The effect of post growth annealing on the structural, optical and morphological quality of the thin films is also reported. The results show that, growth temperature has significant influence on structural and optical properties of the film properties. Increasing the electrolytic solution temperature resulted in slight improvement in crystallinity of CdS thin films in both as deposited and annealed conditions. Due to increase in bath temperature from 45 to 85 °C the energy band gap narrows down from 2.45 to 2.38 eV for as deposited films and 2.42–2.22 eV for annealed films. The increase in deposition temperature improves the atomic ratio of Cd to S. Similarly, the grain sizes of the films increase with increase in growth temperature.