Pressure-induced crystallization of amorphous Ge₂ Sb₂ Te₅

Using in situ x-ray diffraction, we demonstrate a pressure-induced crystallization of as-deposited amorphous Ge₂ Sb₂ Te ₅ (a-GST) into a body-centered-cubic (bcc) solid solution at 28 GPa, and the back transformation from the bcc-GST to a-GST. A large hysteresis loop was observed, as the bcc-GST was retained until 15 GPa. Comparisons have been made, employing the x-ray data and the structural information obtained from ab initio molecular dynamics simulations, between the as-deposited a-GST and the a-GST obtained from the pressure-induced collapse of the rocksalt GST, both at a high hydrostatic pressure (20 GPa) prior to their crystallization to bcc. The results suggest that both routes have resulted in the same high-pressure amorphous state, which explains their crystallization into bcc-GST at similar pressures.