Crystallization behaviors of laser induced Ge₂ Sb₂ Te₅ in different amorphous states

We examined the crystallization behavior of Ge₂ Sb₂ Te₅ in different amorphous states in the context of the kinetic approach using a laser heating method. We measured the changes in reflectance values after varying the applied laser pulse power and duration time and estimated the fraction of the crystalline phase of Ge₂ Sb₂ Te₅ with a nanosecond time scale. The modification of the laser pulse sequence allowed a comparison between the crystallization behaviors of the as-deposited and melt-quenched amorphous states. We determined crystallization kinetics, such as nucleation and growth mechanisms, by combining the results from reflectance measurements and transmission electron microscopy. We observed the different crystallization behaviors between the as-deposited and melt-quenched Ge₂ Sb₂ Te₅ films. The melt-quenched Ge₂ Sb₂ Te₅ demonstrated fast crystallization with a short incubation time compared to the as-deposited sample. The melt-quenched Ge₂ Sb₂ Te₅ also crystallized with a number of fine grains in contrast with the few larger grains seen in the as-deposited Ge₂ Sb₂ Te₅.