Microstructural Properties of Chemically Synthesized Cubic ZnS Nanocrystals

Abstract

In this paper we present microstructural properties of chemically synthesized cubic zinc sulfide (ZnS) nanocrystals, investigated by X-ray diffraction (XRD) line profile analysis applying classical Williamson-Hall (WH) and modified Williamson-Hall (MWH) methods, and transmission electron microscopy (TEM) observations. ZnS nanocrystals are synthesized using 1:1 M ratio of Zn and S precursors with 25, 50, and 75 mM, 2-mercaptoethanol as capping agent. WH analyses show that the average crystallite sizes (lattice strain) are 3.98 nm (2.22 × 10−2), 2.69 nm (1.99 × 10−2), and 2.58 nm (2.65 × 10−2). Dislocation contrast factors of ZnS crystals required for the MWH method are calculated from their elastic stiffness constants for various proportions of screw and edge dislocations. The best fit to MWH equation is found to be for dislocation contrast factors corresponding to 100 % edge dislocations and thereby suggesting edge dislocations are main contributors to strain. MWH analyses show dislocation density of 3.65, 2.69, and 2.47 nm crystallites are 3.19 × 1018 m−2, 2.58 × 1018 m−2, and 4.62 × 1018 m−2 , respectively. The crystallite sizes as estimated from the WH, MWH, and TEM studies are found to be intercorrelated. Presence of edge dislocations, as suggested by the MWH analysis, is confirmed by high resolution TEM (HRTEM) studies.