Phase change in Ge_(2)Sb_(2)Te_(5) films investigated by coherent phonon spectroscopy

摘要

Amorphous and crystalline phases of Ge_(2)Sb_(2)Te_(5) films are investigated by coherent phonon spectroscopy. By heating amorphous films above specific temperatures, the coherent phonon signatures exhibit pronounced changes due to the crystallization of the amorphous phase into a cubic lattice and the transition from the cubic to a hexagonal crystal structure. The phonon modes observed are identified by comparison with coherent phonon spectra of the binary Sb_(2)Te_(3) and GeTe constituents.