Crystallization Mechanism and Course of the Ge_2Sb_2Te_5 Thin Films under Focused Pulse Laser

The relationship between the reflectivity of the Ge2Sb2Te5 thin films, which are as-deposited and melt-quenched states separately, and the pulsed laser time was investigated by the focused pulse laser, and it was found that the reflectivity changes for the two kinds of samples are different. On the basis of the principle of the droplet formation in the gas-liquid system and the basic ideas of the statistical physics, the crystallization mechanism and course of the Ge2Sb2Te5 thin films, which are in as-deposited and melt-quenched states separately, were analyzed and studied in detail. The crystalline nucleus can't form if Ge2Sb2Te5 is in below-saturation or saturation state, different size crystalline nucleus can form if it is in super-saturation. While only the crystalline nucleus which are more than the critical size can grow into crystalline. In addition, the stress, decreasing the crystallization energy barrier and increasing the super-saturation degree of the amorphous Ge2Sb2Te5, is the leading factor causing the different relationships of reflectivity change with pulsed laser width between the as-deposited and melt-quenched Ge2Sb2Te5 thin films. At the same time, on the basis of the analytical results, the reflectivity change characters and laws of the two kinds of the samples under the focused pulse laser were explained in detail.