CdS thin films deposition by AACVD: effect of precursor type, decomposition temperature and solvent

Abstract

Hexagonal cadmium sulfide (CdS) thin films were deposited on glass substrates by aerosol assisted chemical vapour deposition (AACVD) using cadmium(II) dithiocarbamate and xanthate complexes in tetrahydrofuran (THF) and mixed solvents (THF + chloroform) at 400 and 450 °C. The surface morphology and size of the CdS films determined using scanning electron microscopy, showed the formation of films of various morphologies depending on the precursor, the deposition temperature and solvent used. An increase in temperature resulted in an increase in particle size and a change in morphology with the formation of CdS films with distorted structures. The CdS films showed an overall blue shift in their absorption band edge (2.35–2.49 eV) compared to bulk CdS. In dithiocarbamates, a slight blue shift was observed with a shift to higher wavelengths with the reduction of the carbon chain of the dithiocarbamate and an increase in temperature. Films from xanthate complexes showed a strong blue shift at both deposition temperatures. The use of mixed THF + chloroform solvent at 450 °C showed the formation of films with irregular structures compared to those deposited using THF solvent alone, indicating the role of the solvent in shape direction of the films formation. The elemental composition determined by energy dispersive X-ray spectroscopy measurements revealed a 1:1 (Cd:S) ratio in all the samples confirming the stoichiometry of the CdS films.