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Article

Phase Separation in Ge-Rich GeSbTe at Different Length Scales: Melt-Quenched Bulk versus Annealed Thin Films

1
Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
2
Department of Materials Science, University of Milano-Bicocca, Via R. Cozzi 55, I-20125 Milano, Italy
*
Author to whom correspondence should be addressed.
Academic Editors: Gregory M. Odegard and Jordi Sort
Nanomaterials 2022, 12(10), 1717; https://doi.org/10.3390/nano12101717
Received: 19 April 2022 / Revised: 4 May 2022 / Accepted: 16 May 2022 / Published: 18 May 2022
(This article belongs to the Special Issue Synthesis, Properties and Applications of Germanium Chalcogenides)
Integration of the prototypical GeSbTe (GST) ternary alloys, especially on the GeTe-Sb2Te3 tie-line, into non-volatile memory and nanophotonic devices is a relatively mature field of study. Nevertheless, the search for the next best active material with outstanding properties is still ongoing. This search is relatively crucial for embedded memory applications where the crystallization temperature of the active material has to be higher to surpass the soldering threshold. Increasing the Ge content in the GST alloys seems promising due to the associated higher crystallization temperatures. However, homogeneous Ge-rich GST in the as-deposited condition is thermodynamically unstable, and phase separation upon annealing is unavoidable. This phase separation reduces endurance and is detrimental in fully integrating the alloys into active memory devices. This work investigated the phase separation of Ge-rich GST alloys, specifically Ge5Sb2Te3 or GST523, into multiple (meta)stable phases at different length scales in melt-quenched bulk and annealed thin film. Electron microscopy-based techniques were used in our work for chemical mapping and elemental composition analysis to show the formation of multiple phases. Our results show the formation of alloys such as GST213 and GST324 in all length scales. Furthermore, the alloy compositions and the observed phase separation pathways agree to a large extent with theoretical results from density functional theory calculations. View Full-Text
Keywords: phase change materials; Ge-rich GST; pulsed laser deposition; phase separation; GGST; EDX elemental chemical mapping; embedded memory; density functional theory phase change materials; Ge-rich GST; pulsed laser deposition; phase separation; GGST; EDX elemental chemical mapping; embedded memory; density functional theory
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MDPI and ACS Style

Yimam, D.T.; Van Der Ree, A.J.T.; Abou El Kheir, O.; Momand, J.; Ahmadi, M.; Palasantzas, G.; Bernasconi, M.; Kooi, B.J. Phase Separation in Ge-Rich GeSbTe at Different Length Scales: Melt-Quenched Bulk versus Annealed Thin Films. Nanomaterials 2022, 12, 1717. https://doi.org/10.3390/nano12101717

AMA Style

Yimam DT, Van Der Ree AJT, Abou El Kheir O, Momand J, Ahmadi M, Palasantzas G, Bernasconi M, Kooi BJ. Phase Separation in Ge-Rich GeSbTe at Different Length Scales: Melt-Quenched Bulk versus Annealed Thin Films. Nanomaterials. 2022; 12(10):1717. https://doi.org/10.3390/nano12101717

Chicago/Turabian Style

Yimam, Daniel Tadesse, A. J. T. Van Der Ree, Omar Abou El Kheir, Jamo Momand, Majid Ahmadi, George Palasantzas, Marco Bernasconi, and Bart J. Kooi. 2022. "Phase Separation in Ge-Rich GeSbTe at Different Length Scales: Melt-Quenched Bulk versus Annealed Thin Films" Nanomaterials 12, no. 10: 1717. https://doi.org/10.3390/nano12101717

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