Effect of the Sn dopant on the crystallization of amorphous Ge₂Sb₂Te₅ films induced by an excimer laser

In this paper, the influence of Sn doping (0%, 8%, and 14%) on the crystallization of Ge₂Sb₂Te₅ (GST) was studied with the aid of an ultraviolet laser. It was found that the addition of Sn element not only expanded the lattice parameter but also decreased the crystallization temperature and activation energy as compared to the GST. As compared to the Ge₂Sb₂Te₅, a more complete crystallization of the Sn doping Ge₂Sb₂Te₅ is mainly due to the lower binding energy of Sn-Te (359.8 kJ/mol), which could be more easily taken part in the bond breakage and formation than Ge-Te (456 kJ/mol) in such a short time as 30 ns. The equiaxial grains were obtained for the Sn₈Ge₁₅Sb₂₃Te₅₄ films when crystallization was induced by the laser fluence of 20 mJ/cm² but the grains elongated when the laser fluence was increased to 60 mJ/cm². The reason may be the incorporation of Sn elements changed the crystal nucleation mode.