Characterization of Amorphous Phases of Ge2Sb2Te5 Phase-Change Optical Recording Material on Their Crystallization Behavior

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Abstract
The difference in crystallization behavior between the as-deposited amorphous state and the melt-quenched amorphous state of Ge2Sb2Te5 alloy has been studied using a dynamic tester. The melt-quenched amorphous alloy showed much shorter crystallization time than did the as-deposited one. We laser-annealed the as-deposited amorphous alloy under a certain condition so as to make it exhibit the same crystallization property as that of the melt-quenched one. The crystallization kinetics of this laser-annealed amorphous alloy and the as-deposited amorphous alloy has been explained by applying transmission electron microscopy (TEM) and continuously heating the specimens in a differential scanning calorimeter (DSC). From the TEM results, it has been shown that preexisting atomic clusters accelerate the crystallization speed of the amorphous alloy. The two states have been found to have different crystallization temperatures and activation energies.