THE DEPOSITION OF LAYERS OF SULFIDES OF CADMIUM AND LEAD FROM THIOSULFATE-TIOUREA COMPLEXES AND THEIR PROPERTIES

Abstract

Objective. The results of studies of cadmium and lead sulfi de fi lms deposited from aqueous solutions of thiourea-thiosulfate complexes by aerosol pyrolysis at a temperature of 400 °C are presented. The study of thiourea-thiosulfate coordination compounds (TTСС) by infrared spectroscopy was carried out. Results. It was found that in aqueous solutions containing cadmium nitrate, sodium thiosulfate and thiourea with different molar ratios of components the coordination compounds [Cd(SCN2H4)2(bi-S2O3)] are formed. It was revealed that [Pb(SCN2H4)(bi-S2O3)(H2O)] complexes are formed in the Pb(NO3)2 – Na2S2O3 – SCN2H4 – H2O system. It has been established that at the formation of mixed TTСС of lead, as well as cadmium, monodentate coordination of thiourea to the metal cation through the sulfur atom carried out, and the thiosulfate ion is coordinated bidentately through sulfur and oxygen. The crystal structure and phase composition of sulfi des were studied by X-Ray phase analysis. Conclusion. It is established that independently of the molar ratio of components in the initial solution the cadmium sulfi de fi lms crystallize in the structure of wurtzite, and lead sulfi de fi lms – in cubic modifi cation. The transmission spectra of synthesized CdS and PbS fi lms in the region of the fundamental absorption edge were investigated by optical spectrometry. It was revealed that the optical band gap of the cadmium sulfi de fi lms is 2.4 ± 0.01 eV. The fi lms of lead sulfi de are characterized by a slight decrease of the band gap with an increase of the sodium thiosulfate content in the initial solution from 0.56 to 0.50 eV.

Keywords

• thiourea coordination compounds
• thiourea-thiosulfate complexes
• aerosol pyrolysis
• cadmium sulfi de
• lead sulfi de
• fi lms.