Crystallization behavior in Se90Te10 and Se80Te20 thin films

Abstract

Isothermal crystal growth kinetics in Se90Te10 and Se80Te20 thin films was studied by microscopy and in situ X-ray diffraction (XRD) measurements. The spherulite-like crystals grew linearly with time. In a narrow temperature range of between 65 and 85 °C, crystal growth rates exhibit simple exponential behavior with activation energies EG = 193 ± 4 kJ mol−1 for Se90Te10 and EG = 195 ± 4 kJ mol−1 for Se80Te20. The crystal growth in both compositions is controlled by liquid-crystal interface kinetics and can be described by a screw dislocation growth model. From the XRD data, the crystallization fraction was estimated. The crystallization data were described by Johnson-Mehl-Avrami (JMA) model with Avrami exponents m = 1.4 ± 0.3 for Se90Te10 and m = 1.6 ± 0.4 for Se80Te20. Activation energies were estimated from the temperature dependence of rate constant evaluated from the JMA model. The activation energies of nucleation-growth process were found to be Ec = 184 ± 21 kJ mol−1 for Se90Te10 and Ec = 179 ± 7 kJ mol−1 for Se80Te20, and are comparable with activation energies of crystal growth.