Investigation of the structural order in amorphous GeTe-based alloys

The crystallization kinetics of as-deposited (sputtered), laser quenched and ion implanted amorphous Ge2Sb2Te5 (GST) and GeTe thin films have been measured by time resolved reflectivity. An enhancement of the crystallization process occurred in the ion and laser irradiated samples. Raman scattering analysis and transmission electron microscopy measurements were used to correlate the stability of the amorphous phase to its structure. Ion implantation tends to modify the atomic arrangement of the amorphous phase and facilitate the transition to the octahedral crystalline state. The local rearrangement of the amorphous network is suggested to be related to thermal spikes effects rather than to the defects produced by the ions in the collision cascade.