Bond-selective excitation and following displacement of Ge atoms in GeTe/Sb2Te3 superlattice

Abstract

Phase change random access memory devices made from chalcogenides compounds, such as Ge2Sb2Te5, have attracted much attention because of their high-speed read-write and low power consumption capabilities. The phase change in Ge2Sb2Te5 is thought to be characterized by the displacement of Ge atoms, accompanying relaxation of surrounding Sb and Te atoms. Here we examine a new approach, that is the manipulation of Ge-Te bonds using linearly-polarized femtosecond near-infrared optical pulses. As a result, p-polarized pump pulses are found to be more effective in inducing the precursor of phase change, probably due to the atomic arrangements along the unique axis of the superlattice structure.