Experimental and theoretical investigations of laser-induced crystallization and amorphization in phase-change optical recording media

We describe the numerical procedure for calculating three-dimensional profiles of temperature in a multilayer stack illuminated by a laser beam, and model the crystallization and amorphization kinetics for phase-change rewritable media. Experimental methods have been used to determine indirectly the probabilities of nucleation and growth for ${\mathrm{Ge}}_{\mathrm{2}}{\mathrm{Sb}}_{\mathrm{2}}{\mathrm{Te}}_{\mathrm{5}}$ alloy. Some of the fundamental behaviors of phase-change erasable media, such as the crystallization of as-deposited amorphous phase, amorphization of supercooled liquid, and recrystallization of quenched amorphous phase, have been illustrated based on our three-dimensional temperature calculations and the model kinetics. The calculated transient reflectance behavior of as-deposited ${\mathrm{Ge}}_{\mathrm{2}}{\mathrm{Sb}}_{\mathrm{2}}{\mathrm{Te}}_{\mathrm{5}}$ amorphous films in a single layer and in a quadrilayer stack, as well as the erasure behavior of ${\mathrm{Ge}}_{\mathrm{2}}{\mathrm{Sb}}_{\mathrm{2}}{\mathrm{Te}}_{\mathrm{5}}$ alloy in a quadrilayer disk are in good agreement with experimental observations.