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Title: Evolution of short- and medium-range order in the melt-quenching amorphization of Ge2Sb2Te5

Journal Article · · Journal of Materials Chemistry C
DOI: https://doi.org/10.1039/C8TC00549D · OSTI ID:1529369

Phase-change memory takes advantage of the fast phase transition between amorphous and crystalline phases of phase-change materials (e.g.,Ge2Sb2Te5 or GST). To date, while the “SET” process (crystallization of GST glass) has been intensively studied, studies on the “RESET” process (melt-quenching amorphization of GST) are still limited. Here, we explore the structural changes of GST upon rapid cooling by ab initio molecular dynamics simulations and atomistic cluster alignment (ACA) analysis. Different from other methods which only focus on the nearest bonding atoms, the ACA method can study both the short- and medium-range order clusters containing atoms beyond the first-neighboring shell and enables us to explore the changes of cluster structures in a larger scale. The results reveal that low-coordinated octahedral clusters tend to become high-coordinated ones, and Ge-centered octahedral structures change to tetrahedrons whereas Sb-centered tetrahedrons transform to octahedral structures during the amorphization process. Interestingly, tetrahedrons show aggregation in liquid and supercooled liquid in contrast to 6-fold octahedrons which present notable aggregation in amorphous GST. Furthermore, our study showed that wrong bonds (Ge–Ge, Sb–Sb, Ge–Sb and Te–Te bonds) can promote the formation of large rings, and irreducible rings tend to separate into smaller and larger rings as the temperature is decreased. Our conclusions provide useful insights into the formation process and the structure of amorphous GST, which is valuable for facilitating the application of phase change materials.

Research Organization:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Organization:
National Natural Science Foundation of China (NSFC); National Key R&D Plan of China; USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division; National Energy Research Scientific Computing Centre (NERSC)
Grant/Contract Number:
AC02-07CH11358
OSTI ID:
1529369
Report Number(s):
IS-J--9688
Journal Information:
Journal of Materials Chemistry C, Journal Name: Journal of Materials Chemistry C Journal Issue: 18 Vol. 6; ISSN JMCCCX; ISSN 2050-7526
Publisher:
Royal Society of ChemistryCopyright Statement
Country of Publication:
United States
Language:
English

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The Structure of Phase‐Change Chalcogenides and Their High‐Pressure Behavior journal December 2018
Aging in Phase Change Materials: Getting Insight from Simulation journal January 2019
Ovonic Threshold Switching in Se‐Rich Ge x Se 1− x Glasses from an Atomistic Point of View: The Crucial Role of the Metavalent Bonding Mechanism journal January 2020
Optical Properties and Local Structure Evolution during Crystallization of Ga16Sb84 Alloy journal June 2018
Mass spectrometric investigation of amorphous Ga-Sb-Se thin films journal July 2019
Observation of van der Waals reconfiguration in superlattice phase change materials journal January 2019
Understanding CrGeTe 3 : an abnormal phase change material with inverse resistance and density contrast journal January 2019
Local structure origin of ultrafast crystallization driven by high-fidelity octahedral clusters in amorphous Sc 0.2 Sb 2 Te 3 journal February 2019
Temperature dependence of structural, dynamical, and electronic properties of amorphous Bi 2 Te 3 : an ab initio study journal September 2019

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