CdS thin-film electrodeposition from a phosphonium ionic liquid

Thin, adherent films of CdS were electrodeposited on FTO coated glass by reduction of a thiosulfate precursor in the presence of Cd(II) ions in methyltributylphosphonium (P-1,P-4,P-4,P-4) tosylate ionic liquid at 130-150 degrees C. The structural properties of the deposits have been characterized by profilometry, scanning electron microscopy (SEM) and optical microscopy. Energy dispersive X-ray spectroscopy (EDX) was used to evaluate the chemical composition, which was found to be close to stoichiometric. Semiconductor properties including the band gap and. at band potential were calculated from UV-Vis and impedance spectroscopy measurements. The crystal structure was analyzed by X-ray diffraction (XRD). The data obtained from XRD and band gap measurements suggest the presence of hexagonal CdS crystals. The possible growth mechanism of the films is also addressed.