Ethylenediamine-Mediated Wurtzite Phase Formation in ZnS

Abstract

The usual high temperature wurtzite phase of ZnS was successfully obtained at low temperature (170 °C) in the presence of ethylenediamine (EN) as the soft template. X-ray diffraction and Raman spectroscopy analysis confirmed the EN-mediated phase transformation (zinc blende to wurtzite) of ZnS. X-ray photoelectron spectroscopy (XPS) showed that all the samples were sulfur deficient. A high temperature X-ray diffraction (XRD) study showed that ZnS samples, both EN-mediated and without EN, retained their phases except small changes in the unit cell dimension. Besides the EN-mediated phase transition, morphology transformations from nearly spherical shape to nanorods are also observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The coupling between EN molecules with ZnS is confirmed by Fourier transform infrared spectroscopy. A significant reduction in the phase transition temperature of ZnS has been achieved as compared to the bulk transition temperature (1020 °C). Mechanisms of phase transformation have been discussed. The density functional theory (DFT) supports the rod formation and wurtzite structure in the presence of nitrogen-terminated ZnS surface.