Phase Separation in Ge-Rich GeSbTe at Different Length Scales: Melt-Quenched Bulk versus Annealed Thin Films
Integration of the prototypical GeSbTe (GST) ternary alloys, especially on the GeTe-Sb<sub>2</sub>Te<sub>3</sub> 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...
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MDPI AG
2022-05-01
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| author | Daniel Tadesse Yimam A. J. T. Van Der Ree Omar Abou El Kheir Jamo Momand Majid Ahmadi George Palasantzas Marco Bernasconi Bart J. Kooi |
| author_facet | Daniel Tadesse Yimam A. J. T. Van Der Ree Omar Abou El Kheir Jamo Momand Majid Ahmadi George Palasantzas Marco Bernasconi Bart J. Kooi |
| author_sort | Daniel Tadesse Yimam |
| collection | DOAJ |
| description | Integration of the prototypical GeSbTe (GST) ternary alloys, especially on the GeTe-Sb<sub>2</sub>Te<sub>3</sub> 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 Ge<sub>5</sub>Sb<sub>2</sub>Te<sub>3</sub> 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. |
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| issn | 2079-4991 |
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| last_indexed | 2024-03-10T03:16:19Z |
| publishDate | 2022-05-01 |
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| series | Nanomaterials |
| spelling | doaj.art-7ca3cfb644784727ab7b54c76679f89d2023-11-23T12:27:09ZengMDPI AGNanomaterials2079-49912022-05-011210171710.3390/nano12101717Phase Separation in Ge-Rich GeSbTe at Different Length Scales: Melt-Quenched Bulk versus Annealed Thin FilmsDaniel Tadesse Yimam0A. J. T. Van Der Ree1Omar Abou El Kheir2Jamo Momand3Majid Ahmadi4George Palasantzas5Marco Bernasconi6Bart J. Kooi7Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The NetherlandsZernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The NetherlandsDepartment of Materials Science, University of Milano-Bicocca, Via R. Cozzi 55, I-20125 Milano, ItalyZernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The NetherlandsZernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The NetherlandsZernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The NetherlandsDepartment of Materials Science, University of Milano-Bicocca, Via R. Cozzi 55, I-20125 Milano, ItalyZernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The NetherlandsIntegration of the prototypical GeSbTe (GST) ternary alloys, especially on the GeTe-Sb<sub>2</sub>Te<sub>3</sub> 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 Ge<sub>5</sub>Sb<sub>2</sub>Te<sub>3</sub> 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.https://www.mdpi.com/2079-4991/12/10/1717phase change materialsGe-rich GSTpulsed laser depositionphase separationGGSTEDX elemental chemical mapping |
| spellingShingle | Daniel Tadesse Yimam A. J. T. Van Der Ree Omar Abou El Kheir Jamo Momand Majid Ahmadi George Palasantzas Marco Bernasconi Bart J. Kooi Phase Separation in Ge-Rich GeSbTe at Different Length Scales: Melt-Quenched Bulk versus Annealed Thin Films Nanomaterials phase change materials Ge-rich GST pulsed laser deposition phase separation GGST EDX elemental chemical mapping |
| title | Phase Separation in Ge-Rich GeSbTe at Different Length Scales: Melt-Quenched Bulk versus Annealed Thin Films |
| title_full | Phase Separation in Ge-Rich GeSbTe at Different Length Scales: Melt-Quenched Bulk versus Annealed Thin Films |
| title_fullStr | Phase Separation in Ge-Rich GeSbTe at Different Length Scales: Melt-Quenched Bulk versus Annealed Thin Films |
| title_full_unstemmed | Phase Separation in Ge-Rich GeSbTe at Different Length Scales: Melt-Quenched Bulk versus Annealed Thin Films |
| title_short | Phase Separation in Ge-Rich GeSbTe at Different Length Scales: Melt-Quenched Bulk versus Annealed Thin Films |
| title_sort | phase separation in ge rich gesbte at different length scales melt quenched bulk versus annealed thin films |
| topic | phase change materials Ge-rich GST pulsed laser deposition phase separation GGST EDX elemental chemical mapping |
| url | https://www.mdpi.com/2079-4991/12/10/1717 |
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