A study on the crystallization behavior of Sn-doped amorphous Ge₂Sb₂Te₅ by ultraviolet laser radiation

Highlights: • The Raman peaks of Sn doped GST moved towards lower wavenumbers compared to GST. • The crystallization fluence for Sn doped GST was smaller than that for pure GST. • The optical contrast increased from 15% to 40% with the addition of Sn. • Optical contrast changed little with the variation of laser fluence. - Abstract: In this paper, the influence of Sn doping (0%, 8% and 14%) on the crystallization of Ge₂Sb₂Te₅ was studied with the aid of an ultraviolet laser. The XRD analyses revealed that the addition of Sn maintained the NaCl-type structure of Ge₂Sb₂Te₅ after crystallization but expanded the lattice parameter due to the smaller atomic radii of Ge replaced by Sn. Raman peaks (123, 150 and 110 cm⁻¹) moved towards lower wavenumbers (118, 137 and 104 cm⁻¹), which can be explained by the remarkable decrease of the binding energy from Ge–Te to Sn–Te. A remarkable increase in optical contrast from 15% to 40% was observed in the Sn-doped Ge₂Sb₂Te₅ film after crystallization with both the isothermal annealing and laser radiance. While the optical contrast changed little for a fixed volume fraction of Sn-doped sample with the variation of laser fluence which is attributed to the crystallization mechanism induced by laser under different fluences is the same