A cross sectional study on the crystallization of amorphous Ge2Sb2Te5 films induced by a single-pulse ultraviolet laser

Abstract

In this paper, the crystallization along the film thickness of amorphous Ge2Sb2Te5 (a-GST) films induced by a single-pulse ultraviolet laser was investigated by using transmission electron microscopy (TEM) integrated with SAED. TEM observations showed that the crystalline GST (c-GST) was composed of columnar grains at the top surface and equaixed grains inside the film. Moreover, the columnar grains became larger with the increase of laser fluence. A three-dimensional finite element method simulation was further used to elucidate the temperature field by a nanosecond excimer laser in the cross section of the a-GST film. A big temperature gradient obtained at the top surface in the cooling process caused the formation of columnar grains, while columnar grains were gradually substituted by small equaixed grains with the decrease of temperature gradient downwards the film interior.