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

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.