TRANSFORMATION FROM THE AMORPHOUS TO THE NANOCRYSTALLINE STATE IN PURE SELENIUM

A bulk nanocrystalline selenium (nc-Se) was formed by completely crystallizing a melt-quenched amorphous selenium (a-Se). The transformation process of the a-Se to the nc-Se and its microstructure were characterized by means of differential scanning calorimetry (DSC), x-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Structural analyses indicated that the nanocrystalline selenium samples with average gl ain sizes ranging from 6 to 45 nm were of the trigonal structure, and the morphology of nc-Se was in the form of lamellae, which are made up of fine fibers. A crystallization mechanism of chain folding is suggested to interpret the structural features of the nc-Se and the transformation process from amorphous to nanocrystalline trigonal selenium.