Mechanochemical solid state synthesis of (Cd0.8Zn0.2)S quantum dots: Microstructure and optical characterizations

(Cd_0.8Zn_0.2)S quantum dots with a mixture of both cubic (Zinc-blende) and hexagonal (Wurtzite) phases have been prepared within 75 min by mechanical alloying the stoichiometric mixture of Cd, Zn and S powders at room temperature in a planetary ball mill under Ar. The Rietveld analysis of X-ray powder diffraction data reveals relative phase abundances of both cubic and hexagonal phases and several microstructure parameters like lattice parameters, particle sizes, lattice strains, concentrations of different kinds of stacking faults, etc. in both the phases. At the time of formation, hexagonal phase dominates over the cubic phase (molar ratio ∼0.6:0.4), but in course of milling up to 15 h, the hexagonal phase partially transforms to cubic phase and the molar ratio becomes ∼0.4:0.6. Particle sizes of hexagonal and cubic phases reduce to ∼4.5 nm and 12.5 nm, respectively, after 15 h of milling. The hexagonal phase contains a significant amount of lattice strain in comparison to cubic phase. The presence of different kinds of stacking faults is revealed clearly from the high resolution transmission electron microscope (HRTEM) images.