Isoconversional kinetic analysis of the crystallization phases of amorphous selenium thin films

The crystallization kinetics of Se thin films were determined under nonisothermal conditions using a differential scanning calorimetry (DSC) technique. The development of crystal phases by thermal treatment of the film at various temperatures was analyzed by X-ray diffraction. Microstructures were identified by studying the morphology of the films using scanning electron microscopy and atomic force microscopy. This study reveals the simultaneous presence of distinct hexagonal and monoclinic phases; the DSC crystallization curve is formed by overlapping the exothermic crystallization curves of both phases. Two isoconversional methods, the Kissinger–Akahira–Sunose and Vyazovkin methods, were used to determine the variation of the activation energy for crystallization with temperature. The results show that the crystallization activation energy decreases with the extent of crystallization or temperature, which suggests that the examined phases follow multi-step kinetics.