Coexistence of cubic and hexagonal phases of Cd doped ZnS at different annealing temperatures

Abstract

Simultaneous formation of biphasic ternary chalcogenide from Cd:ZnS with binary crystal structures was synthesized at different temperatures; 200, 300, 400, and 500 °C. The effect of the annealing tempeartures on the structural and optical properties was investigated for the ternary solid solution of Zn0.75Cd0.25S chalcogenide system. XRD pattern hand by hand with Rietveld profile method confirms the coexistence of wurtzite and zinc blend structures of Zn0.75Cd0.25S. FTIR spectra sign the characteristic bands of Zn0.75Cd0.25S at 549, 591, 790 and 984 cm-1 slightly shifted with temperature and their intensity is temperature dependent. Photoluminescence spectra reveal a marginal shift in the blue-green emission band with annealing temperature. Also the emission band arises from the surface states relating to high concentration of surface defect states. The nanosized particles were also confirmed by the UV-vis absorption edge at the UV region (340 nm). UV-vis analysis shows that the energy gap of Zn0.75Cd0.25S is located between those of CdS and ZnS. EDX analysis identified only on Cd, Zn and S without any other impurities within the sample and with nominal composition of Zn0.75Cd0.25S solid solution. The annealing temperature at 200 °C is the optimum at which the nucleated Zn0.75Cd0.25S system emits maximum fluorescence.