How important is the {103} plane of stable Ge2Sb2Te5 for phase‐change memory?

Zhang, W.; Zheng, Weitao; Kim, J.-G.; Cui, Xiaoqiang; Li, L.; Qi, Jingang; Kim, Y.-J.; Song, Sukhyun

doi:10.1111/jmi.12242

Cited by 6 publications

(3 citation statements)

References 36 publications

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“…In view of the similar configuration and minor energy discrepancy between the 100% VOC- and h-GST lattices, a non-diffusion controlled slide of the building blocks was proposed to understand the f-to-h transformation 18 . Analogous research achievement stated that a shearing martensitic transformation from {200} planes of f-GST to {} planes of h-GST should be energetically favorable during f-to-h transition 19, 20 . In addition, the discovery of twin crystals consisted by one f- and one h-grain led to an “epitaxial growth model” to interpret the structure evolution manner as f-GST approaching the h-phase 21, 22 .…”

Section: Introductionmentioning

confidence: 99%

Surface Energy Driven Cubic-to-Hexagonal Grain Growth of Ge2Sb2Te5 Thin Film

Zheng

Cheng

et al. 2017

Sci Rep

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Phase change memory (PCM) is a promising nonvolatile memory to reform current commercial computing system. Inhibiting face-centered cubic (f-) to hexagonal (h-) phase transition of Ge2Sb2Te5 (GST) thin film is essential for realizing high-density, high-speed, and low-power PCM. Although the atomic configurations of f- and h-lattices of GST alloy and the transition mechanisms have been extensively studied, the real transition process should be more complex than previous explanations, e.g. vacancy-ordering model for f-to-h transition. In this study, dynamic crystallization procedure of GST thin film was directly characterized by in situ heating transmission electron microscopy. We reveal that the equilibrium to h-phase is more like an abnormal grain growth process driven by surface energy anisotropy. More specifically, [0001]-oriented h-grains with the lowest surface energy grow much faster by consuming surrounding small grains, no matter what the crystallographic reconfigurations would be on the frontier grain-growth boundaries. We argue the widely accepted vacancy-ordering mechanism may not be indispensable for the large-scale f-to-h grain growth procedure. The real-time observations in this work contribute to a more comprehensive understanding of the crystallization behavior of GST thin film and can be essential for guiding its optimization to achieve high-performance PCM applications.

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Section: Introductionmentioning

confidence: 99%

Surface Energy Driven Cubic-to-Hexagonal Grain Growth of Ge2Sb2Te5 Thin Film

Zheng

Cheng

et al. 2017

Sci Rep

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“…Considering the plausible similar atomic sequence in f-and hlattice, researchers tend to believe a diffusionless controlled mechanism should happen during the whole crystal transition process 22,37 . For example, the shearing martensitic mechanism with a twisting atomic movement 38,39 , the epitaxial growth mechanism through a continuous accumulation 40,41 , and recently, a vacancy ordering mechanism which emphasizes the critical role of the vacancy aggregation behavior 24,25,42,43 . Though above-mentioned mechanisms seem to be very intriguing, puzzles in the atomic arrangement of different structures, especially the intermediate (i-) state, obstruct the clarification of the exact transition mechanism.…”

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confidence: 99%

Direct atomic identification of cation migration induced gradual cubic-to-hexagonal phase transition in Ge2Sb2Te5

et al. 2019

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GeTe-Sb 2 Te 3 pseudobinary system, especially Ge 2 Sb 2 Te 5 alloy, is the most desirable material to be commercialized in phase change random access memory. Directly resolving the local atomic arrangement of Ge 2 Sb 2 Te 5 during intermediate steps is an effective method to understand its transition mechanism from face-centered-cubic to hexagonal phases. In this study, we provide insights into the atomic arrangement variation during face-centered-cubic to hexagonal transition process in Ge 2 Sb 2 Te 5 alloy by using advanced atomic resolution energy dispersive X-ray spectroscopy. Induced by thermal annealing, randomly distributed germanium and antimony atoms would migrate to the specific (111) layer in different behaviors, and antimony atoms migrate earlier than germanium atoms during the phase transition process, gradually forming intermediate structures similar to hexagonal lattice. With the migration completed, the obtained stable hexagonal structure has a partially ordered stacking sequence described as below:-Te-Sb x /Ge y-Te-Ge x /Sb y-Te-Ge x /Sb y-Te-Sb x /Ge y-Te-(x > y), which is directly related to the migration process. The current visual fragments suggest a gradual transition mechanism, and guide the performance optimization of Ge 2 Sb 2 Te 5 alloy.

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“…However, ordering of Ge cations in GST326 in the middle of building block was assumed. Although different GST compounds (stable and metastable) are very close in terms of structure174548495051, it is not clear why the cation layers in the GST124 structure should not possess intermixing. As an explanation, it was proposed that the Te, Sb and Ge atoms in the (0001) plane have to satisfy the 3Ge-Te-3Sb rule, in which Te atoms are surrounded by three Ge and three Sb atoms located in opposite corners of the octahedron structures45.…”

Section: Resultsmentioning

confidence: 99%

Local atomic arrangements and lattice distortions in layered Ge-Sb-Te crystal structures

Lotnyk

Roß

Bernütz

et al. 2016

Sci Rep

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Insights into the local atomic arrangements of layered Ge-Sb-Te compounds are of particular importance from a fundamental point of view and for data storage applications. In this view, a detailed knowledge of the atomic structure in such alloys is central to understanding the functional properties both in the more commonly utilized amorphous–crystalline transition and in recently proposed interfacial phase change memory based on the transition between two crystalline structures. Aberration-corrected scanning transmission electron microscopy allows direct imaging of local arrangement in the crystalline lattice with atomic resolution. However, due to the non-trivial influence of thermal diffuse scattering on the high-angle scattering signal, a detailed examination of the image contrast requires comparison with theoretical image simulations. This work reveals the local atomic structure of trigonal Ge-Sb-Te thin films by using a combination of direct imaging of the atomic columns and theoretical image simulation approaches. The results show that the thin films are prone to the formation of stacking disorder with individual building blocks of the Ge2Sb2Te5, Ge1Sb2Te4 and Ge3Sb2Te6 crystal structures intercalated within randomly oriented grains. The comparison with image simulations based on various theoretical models reveals intermixed cation layers with pronounced local lattice distortions, exceeding those reported in literature.

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How important is the {103} plane of stable Ge₂Sb₂Te₅ for phase‐change memory?

Cited by 6 publications

References 36 publications

Surface Energy Driven Cubic-to-Hexagonal Grain Growth of Ge2Sb2Te5 Thin Film

Surface Energy Driven Cubic-to-Hexagonal Grain Growth of Ge2Sb2Te5 Thin Film

Direct atomic identification of cation migration induced gradual cubic-to-hexagonal phase transition in Ge2Sb2Te5

Local atomic arrangements and lattice distortions in layered Ge-Sb-Te crystal structures

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