Microstructure and optical band-gap of mechano-synthesized CdxZn1-xS quantum dots

CdxZn1-xS (x = 0.0 to 1.0, at 0.1 interval) quantum dots (QDs) were synthesized by mechanical alloying of the stoichiometric mixture of elemental Cd, Zn and S powders at room temperature under Ar in record minimum time. The Cd0.5Zn0.5S QDs were formed after 25 min and the Cd0.1Zn0.9S QDs after 160 min of milling. The x-ray and high resolution transmission electron microscope characterizations reveal the presence of both major and minor zinc-blende and wurtzite phases and stacking faults in these QDs. Lattice parameters of both these phases decrease and the optical band-gaps increase continuously with increasing Zn concentrations. A very distinct change in colour of these QDs from blue to red is noticed with increasing Cd concentration from 0 to 1, indicating that optical band-gap varies with varying composition.