Influence of Sn dopant on the crystallization of amorphous Ge2Sb2Te5 by a picosecond pulsed laser irradiation

Phase-change materials were highly promising for next-generation nonvolatile data storage technology and their properties were usually improved by doping. In this paper, the pronounced effects of Sn doping (0%, 10%, 30%) on crystallization behaviors of Ge2Sb2Te5 (GST) film induced by a picosecond pulsed laser were investigated in detail. The TEM observations presented the crystallization threshold, melting threshold and ablation threshold all decreased with the increasing of Sn doping while the crystal structure and crystallization behavior has not been changed. After single pulse Gaussian laser irradiation, the morphology of crystallized films for GST and Sn-doped GST all presented an ingot-like microstructure at higher laser fluence and equiaxed crystal microstructure at lower laser fluence, which was mainly caused by the temperature gradient. The local grain refinement was found in GSTSn30% films because weaker Sn-Te bond (359.8 kJ/mol) replaced the stronger Ge-Te bond (456 kJ/mol), which was also proved by X-ray photoelectron spectroscopy (XPS). This eventually led to a decline in nucleation energy barrier and increased nucleation rate.