Microstructure and photoluminescence properties of ternary Cd_0.2Zn_0.8S quantum dots synthesized by mechanical alloying

Abstract

Ternary Cd_0.2Zn_0.8S quantum dots with a mixture of both cubic (zinc blende) and hexagonal (Wurtzite) phases have been prepared 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 the X-ray diffraction patterns gives an insight of the relative phase abundances of both cubic and hexagonal phases present in sample. Microstructure parameters like change in lattice parameters, the variation of lattice strain, particle size, stacking faults of different kinds are quantitatively determined. High resolution transmission electron microscopy (HRTEM) image analysis corroborates well with the results obtained from the Rietveld analysis. A core–shell structure has been found in HRTEM images where major cubic phase remains at the core and minor hexagonal phase constitutes the shell. Optical band gap measurement using UV–Vis spectroscopy confirms the quantum confinement effects. Steady-state and time-resolved photoluminescence study have also been carried out for better understanding the optical property of this material. Atomic structure modelling helps to reveal the structural changes happening during different milling times.