Dynamic theory of crystallization in Ge_2Sb_23Te_5 phase-change optical recording media

We develop a theory of the crystallization dynamics of Ge(2)Sb(2.3)Te(5) thin films that shows good qualitative agreement with experimental reflectivity results from a two-laser static tester. The theory is adapted from the nucleation theory of liquid droplets from supersaturated vapor and elucidates the physics underlying the amorphous-to-crystalline phase transformation under short-pulse excitation. In particular, the theory provides a physical picture in which crystalline islands, or basic embryos, are thermally activated in the amorphous material and subsequently grow as stable nuclei are formed.