Rocksalt-structured GeSbTe phase-change materials contained significant amounts of intrinsic vacancies at one sub-lattice. On the basis of ab initio total energy calculations, it was shown that the so-called intrinsic vacancies resulted from geometrical voids that originated from packing spaces for lone pairs of electrons tightly bound to specific Te layers where a weak bonding exists. The existence of such geometrical voids was concomitant with a narrow band gap. The present results also shed new light on the intrinsic vacancies in rocksalt-structured GeSbTe.

Vacancy or Not: an Insight on the Intrinsic Vacancies in Rocksalt-Structured GeSbTe Alloys from ab initio Calculations. J.Zhou, Z.Sun, Y.Pan, Z.Song, R.Ahuja: EPL, 2011, 95[2], 27002