Hierarchical structure and phase transition of (GeTe)n(Sb 2Te3)m used for phase-change memory

Jino Im, Jae Hyeon Eom, Changwon Park, Kimin Park, Dong Seok Suh, Kijoon Kim, Youn Seon Kang, Cheolkyu Kim, Tae Yon Lee, Yoonho Khang, Young Gui Yoon, Jisoon Ihm

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6 Scopus citations


(GeTe)n(Sb2 Te3)m is the material which has been extensively studied for phase-change memory applications. However, the local structure and the phase-transition mechanism of this material are not precisely known yet. We propose here, based on the recent extended x-ray absorption fine structure spectroscopy, stibnite-like Sb2 Te3 units and chainlike GeTe units as primary building blocks of the material. Then we further propose a three-dimensional model of secondary building blocks composed of a small number of primary building blocks. The phase change between the crystalline and the amorphous structure is shown to occur via reorientations of the secondary building blocks, establishing a simple reversible transformation process that can explain the high endurance and the fast switching time of the material. In the amorphous phase, the relaxed structure obtained from the ab initio total-energy minimization calculations satisfies the experimentally observed 8-N rule for the atomic coordination number.

Original languageEnglish
Article number205205
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number20
StatePublished - 21 Nov 2008


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