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Bertelli M, Sfuncia G, De Simone S, Diaz Fattorini A, Calvi S, Mussi V, Arciprete F, Mio AM, Calarco R, Longo M. Stable chalcogenide Ge-Sb-Te heterostructures with minimal Ge segregation. Sci Rep 2024; 14:15713. [PMID: 38977811 PMCID: PMC11231325 DOI: 10.1038/s41598-024-66441-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Accepted: 07/01/2024] [Indexed: 07/10/2024] Open
Abstract
Matching of various chalcogenide films shows the advantage of delivering multilayer heterostructures whose physical properties can be tuned with respect to the ones of the constituent single films. In this work, (Ge-Sb-Te)-based heterostructures were deposited by radio frequency sputtering on Si(100) substrates and annealed up to 400 °C. The as-deposited and annealed samples were studied by means of X-ray fluorescence, X-ray diffraction, scanning transmission electron microscopy, electron energy loss spectroscopy and Raman spectroscopy. The heterostructures, combining thermally stable thin layers (i. e. Ge-rich Ge5.5Sb2Te5, Ge) and films exhibiting fast switching dynamics (i. e. Sb2Te3), show, on the one side, higher crystallization-onset temperatures than the standard Ge2Sb2Te5 alloy and, on the other side, none to minimal Ge-segregation.
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Affiliation(s)
- Marco Bertelli
- Institute for Microelectronics and Microsystems (IMM), Consiglio Nazionale delle Ricerche (CNR), Via del Fosso del Cavaliere 100, 00133, Rome, Italy
- Institute for Microelectronics and Microsystems (IMM), Consiglio Nazionale delle Ricerche (CNR), Strada VIII N. 5, 95121, Catania, Italy
| | - Gianfranco Sfuncia
- Institute for Microelectronics and Microsystems (IMM), Consiglio Nazionale delle Ricerche (CNR), Strada VIII N. 5, 95121, Catania, Italy
| | - Sara De Simone
- Institute for Microelectronics and Microsystems (IMM), Consiglio Nazionale delle Ricerche (CNR), Via del Fosso del Cavaliere 100, 00133, Rome, Italy.
| | - Adriano Diaz Fattorini
- Department of Physics, University of "Tor Vergata", Via della Ricerca Scientifica 1, 00133, Rome, Italy
| | - Sabrina Calvi
- Department of Physics, University of "Tor Vergata", Via della Ricerca Scientifica 1, 00133, Rome, Italy
| | - Valentina Mussi
- Institute for Microelectronics and Microsystems (IMM), Consiglio Nazionale delle Ricerche (CNR), Via del Fosso del Cavaliere 100, 00133, Rome, Italy
| | - Fabrizio Arciprete
- Institute for Microelectronics and Microsystems (IMM), Consiglio Nazionale delle Ricerche (CNR), Via del Fosso del Cavaliere 100, 00133, Rome, Italy
- Department of Physics, University of "Tor Vergata", Via della Ricerca Scientifica 1, 00133, Rome, Italy
| | - Antonio M Mio
- Institute for Microelectronics and Microsystems (IMM), Consiglio Nazionale delle Ricerche (CNR), Strada VIII N. 5, 95121, Catania, Italy
| | - Raffaella Calarco
- Institute for Microelectronics and Microsystems (IMM), Consiglio Nazionale delle Ricerche (CNR), Via del Fosso del Cavaliere 100, 00133, Rome, Italy
| | - Massimo Longo
- Institute for Microelectronics and Microsystems (IMM), Consiglio Nazionale delle Ricerche (CNR), Via del Fosso del Cavaliere 100, 00133, Rome, Italy
- Department of Chemical Science and Technologies, University of "Tor Vergata", Via della Ricerca Scientifica 1, 00133, Rome, Italy
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2
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Privitera SMS. Synthesis, Properties and Applications of Germanium Chalcogenides. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:2925. [PMID: 36079963 PMCID: PMC9457559 DOI: 10.3390/nano12172925] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Accepted: 08/23/2022] [Indexed: 06/15/2023]
Abstract
Germanium (Ge) chalcogenides are characterized by unique properties which make these materials interesting for a very wide range of applications, from phase change memories to ovonic threshold switches, from photonics to thermoelectric and photovoltaic devices [...].
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Affiliation(s)
- Stefania M S Privitera
- Institute for Microelectronic and Microsystems (IMM), National Research Council (CNR), Zona Industriale Ottava Strada 5, 95121 Catania, Italy
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3
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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:nano12101717. [PMID: 35630939 PMCID: PMC9143932 DOI: 10.3390/nano12101717] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Revised: 05/04/2022] [Accepted: 05/16/2022] [Indexed: 11/16/2022]
Abstract
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.
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Affiliation(s)
- Daniel Tadesse Yimam
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands; (D.T.Y.); (A.J.T.V.D.R.); (J.M.); (M.A.); (G.P.)
| | - A. J. T. Van Der Ree
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands; (D.T.Y.); (A.J.T.V.D.R.); (J.M.); (M.A.); (G.P.)
| | - Omar Abou El Kheir
- Department of Materials Science, University of Milano-Bicocca, Via R. Cozzi 55, I-20125 Milano, Italy; (O.A.E.K.); (M.B.)
| | - Jamo Momand
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands; (D.T.Y.); (A.J.T.V.D.R.); (J.M.); (M.A.); (G.P.)
| | - Majid Ahmadi
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands; (D.T.Y.); (A.J.T.V.D.R.); (J.M.); (M.A.); (G.P.)
| | - George Palasantzas
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands; (D.T.Y.); (A.J.T.V.D.R.); (J.M.); (M.A.); (G.P.)
| | - Marco Bernasconi
- Department of Materials Science, University of Milano-Bicocca, Via R. Cozzi 55, I-20125 Milano, Italy; (O.A.E.K.); (M.B.)
| | - Bart J. Kooi
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands; (D.T.Y.); (A.J.T.V.D.R.); (J.M.); (M.A.); (G.P.)
- Correspondence:
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4
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Portavoce A, Roland G, Remondina J, Descoins M, Bertoglio M, Amalraj M, Eyméoud P, Dutartre D, Lorut F, Putero M. Kinetic Monte Carlo simulations of Ge-Sb-Te thin film crystallization. NANOTECHNOLOGY 2022; 33:295601. [PMID: 35439738 DOI: 10.1088/1361-6528/ac6813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Accepted: 04/19/2022] [Indexed: 06/14/2023]
Abstract
Simulation of atomic redistribution in Ge-Sb-Te (GST)-based memory cells during SET/RESET cycling is needed in order to understand GST memory cell failure and to design improved non-volatile memories. However, this type of atomic scale simulations is extremely challenging. In this work, we propose to use a simplified GST system in order to catch the basics of atomic redistribution in Ge-rich GST (GrGST) films using atomistic kinetic Monte Carlo simulations. Comparison between experiments and simulations shows good agreements regarding the influence of Ge excess on GrGST crystallization, as well as concerning the GST growth kinetic in GrGST films, suggesting the crystallized GST ternary compound to be off-stoichiometric. According to the simulation of atomic redistribution in GrGST films during SET/RESET cycling, the film microstructure stabilized during cycling is significantly dependent of the GST ternary phase stoichiometry. The use of amorphous layers exhibiting the GST ternary phase stoichiometry placed at the bottom or at the top of the GrGST layer is shown to be a way of controlling the microstructure evolution of the film during cycling. The significant evolution of the local composition in the amorphous solution during cycling suggests a non-negligible variation of the crystallization temperature with operation time.
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Affiliation(s)
- A Portavoce
- Aix-Marseille University/CNRS, IM2NP, Faculté des Sciences de Saint-Jérôme case 142, F-13397 Marseille, France
| | - G Roland
- Aix-Marseille University/CNRS, IM2NP, Faculté des Sciences de Saint-Jérôme case 142, F-13397 Marseille, France
- STMicroelectronics, 850 Rue Jean Monnet, F-38920 Crolles, France
| | - J Remondina
- Aix-Marseille University/CNRS, IM2NP, Faculté des Sciences de Saint-Jérôme case 142, F-13397 Marseille, France
| | - M Descoins
- Aix-Marseille University/CNRS, IM2NP, Faculté des Sciences de Saint-Jérôme case 142, F-13397 Marseille, France
| | - M Bertoglio
- Aix-Marseille University/CNRS, IM2NP, Faculté des Sciences de Saint-Jérôme case 142, F-13397 Marseille, France
| | - M Amalraj
- Aix-Marseille University/CNRS, IM2NP, Faculté des Sciences de Saint-Jérôme case 142, F-13397 Marseille, France
| | - P Eyméoud
- Aix-Marseille University/CNRS, IM2NP, Faculté des Sciences de Saint-Jérôme case 142, F-13397 Marseille, France
| | - D Dutartre
- STMicroelectronics, 850 Rue Jean Monnet, F-38920 Crolles, France
| | - F Lorut
- STMicroelectronics, 850 Rue Jean Monnet, F-38920 Crolles, France
| | - M Putero
- Aix-Marseille University/CNRS, IM2NP, Faculté des Sciences de Saint-Jérôme case 142, F-13397 Marseille, France
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5
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Díaz Fattorini A, Chèze C, López García I, Petrucci C, Bertelli M, Righi Riva F, Prili S, Privitera SMS, Buscema M, Sciuto A, Di Franco S, D’Arrigo G, Longo M, De Simone S, Mussi V, Placidi E, Cyrille MC, Tran NP, Calarco R, Arciprete F. Growth, Electronic and Electrical Characterization of Ge-Rich Ge–Sb–Te Alloy. NANOMATERIALS 2022; 12:nano12081340. [PMID: 35458046 PMCID: PMC9031044 DOI: 10.3390/nano12081340] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 04/07/2022] [Accepted: 04/11/2022] [Indexed: 02/01/2023]
Abstract
In this study, we deposit a Ge-rich Ge–Sb–Te alloy by physical vapor deposition (PVD) in the amorphous phase on silicon substrates. We study in-situ, by X-ray and ultraviolet photoemission spectroscopies (XPS and UPS), the electronic properties and carefully ascertain the alloy composition to be GST 29 20 28. Subsequently, Raman spectroscopy is employed to corroborate the results from the photoemission study. X-ray diffraction is used upon annealing to study the crystallization of such an alloy and identify the effects of phase separation and segregation of crystalline Ge with the formation of grains along the [111] direction, as expected for such Ge-rich Ge–Sb–Te alloys. In addition, we report on the electrical characterization of single memory cells containing the Ge-rich Ge–Sb–Te alloy, including I-V characteristic curves, programming curves, and SET and RESET operation performance, as well as upon annealing temperature. A fair alignment of the electrical parameters with the current state-of-the-art of conventional (GeTe)n-(Sb2Te3)m alloys, deposited by PVD, is found, but with enhanced thermal stability, which allows for data retention up to 230 °C.
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Affiliation(s)
- Adriano Díaz Fattorini
- Istituto per la Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche (CNR), Via del Fosso del Cavaliere 100, 00133 Rome, Italy; (A.D.F.); (C.P.); (M.B.); (M.L.); (S.D.S.); (V.M.)
- Dipartimento di Fisica, Università di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Rome, Italy; (C.C.); (F.R.R.); (S.P.); (E.P.); (F.A.)
| | - Caroline Chèze
- Dipartimento di Fisica, Università di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Rome, Italy; (C.C.); (F.R.R.); (S.P.); (E.P.); (F.A.)
| | - Iñaki López García
- Istituto per la Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche (CNR), Zona Industriale Ottava Strada 5, 95121 Catania, Italy; (I.L.G.); (S.M.S.P.); (M.B.); (A.S.); (S.D.F.); (G.D.)
| | - Christian Petrucci
- Istituto per la Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche (CNR), Via del Fosso del Cavaliere 100, 00133 Rome, Italy; (A.D.F.); (C.P.); (M.B.); (M.L.); (S.D.S.); (V.M.)
| | - Marco Bertelli
- Istituto per la Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche (CNR), Via del Fosso del Cavaliere 100, 00133 Rome, Italy; (A.D.F.); (C.P.); (M.B.); (M.L.); (S.D.S.); (V.M.)
| | - Flavia Righi Riva
- Dipartimento di Fisica, Università di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Rome, Italy; (C.C.); (F.R.R.); (S.P.); (E.P.); (F.A.)
| | - Simone Prili
- Dipartimento di Fisica, Università di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Rome, Italy; (C.C.); (F.R.R.); (S.P.); (E.P.); (F.A.)
| | - Stefania M. S. Privitera
- Istituto per la Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche (CNR), Zona Industriale Ottava Strada 5, 95121 Catania, Italy; (I.L.G.); (S.M.S.P.); (M.B.); (A.S.); (S.D.F.); (G.D.)
| | - Marzia Buscema
- Istituto per la Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche (CNR), Zona Industriale Ottava Strada 5, 95121 Catania, Italy; (I.L.G.); (S.M.S.P.); (M.B.); (A.S.); (S.D.F.); (G.D.)
| | - Antonella Sciuto
- Istituto per la Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche (CNR), Zona Industriale Ottava Strada 5, 95121 Catania, Italy; (I.L.G.); (S.M.S.P.); (M.B.); (A.S.); (S.D.F.); (G.D.)
| | - Salvatore Di Franco
- Istituto per la Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche (CNR), Zona Industriale Ottava Strada 5, 95121 Catania, Italy; (I.L.G.); (S.M.S.P.); (M.B.); (A.S.); (S.D.F.); (G.D.)
| | - Giuseppe D’Arrigo
- Istituto per la Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche (CNR), Zona Industriale Ottava Strada 5, 95121 Catania, Italy; (I.L.G.); (S.M.S.P.); (M.B.); (A.S.); (S.D.F.); (G.D.)
| | - Massimo Longo
- Istituto per la Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche (CNR), Via del Fosso del Cavaliere 100, 00133 Rome, Italy; (A.D.F.); (C.P.); (M.B.); (M.L.); (S.D.S.); (V.M.)
| | - Sara De Simone
- Istituto per la Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche (CNR), Via del Fosso del Cavaliere 100, 00133 Rome, Italy; (A.D.F.); (C.P.); (M.B.); (M.L.); (S.D.S.); (V.M.)
| | - Valentina Mussi
- Istituto per la Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche (CNR), Via del Fosso del Cavaliere 100, 00133 Rome, Italy; (A.D.F.); (C.P.); (M.B.); (M.L.); (S.D.S.); (V.M.)
| | - Ernesto Placidi
- Dipartimento di Fisica, Università di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Rome, Italy; (C.C.); (F.R.R.); (S.P.); (E.P.); (F.A.)
- Department of Physics, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy
| | - Marie-Claire Cyrille
- Leti, CEA, University Grenoble Alpes, 38000 Grenoble, France; (M.-C.C.); (N.-P.T.)
| | - Nguyet-Phuong Tran
- Leti, CEA, University Grenoble Alpes, 38000 Grenoble, France; (M.-C.C.); (N.-P.T.)
| | - Raffaella Calarco
- Istituto per la Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche (CNR), Via del Fosso del Cavaliere 100, 00133 Rome, Italy; (A.D.F.); (C.P.); (M.B.); (M.L.); (S.D.S.); (V.M.)
- Correspondence:
| | - Fabrizio Arciprete
- Dipartimento di Fisica, Università di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Rome, Italy; (C.C.); (F.R.R.); (S.P.); (E.P.); (F.A.)
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6
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Chèze C, Righi Riva F, Di Bella G, Placidi E, Prili S, Bertelli M, Diaz Fattorini A, Longo M, Calarco R, Bernasconi M, Abou El Kheir O, Arciprete F. Interface Formation during the Growth of Phase Change Material Heterostructures Based on Ge-Rich Ge-Sb-Te Alloys. NANOMATERIALS 2022; 12:nano12061007. [PMID: 35335820 PMCID: PMC8949867 DOI: 10.3390/nano12061007] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 03/10/2022] [Accepted: 03/15/2022] [Indexed: 02/01/2023]
Abstract
In this study, we present a full characterization of the electronic properties of phase change material (PCM) double-layered heterostructures deposited on silicon substrates. Thin films of amorphous Ge-rich Ge-Sb-Te (GGST) alloys were grown by physical vapor deposition on Sb2Te3 and on Ge2Sb2Te5 layers. The two heterostructures were characterized in situ by X-ray and ultraviolet photoemission spectroscopies (XPS and UPS) during the formation of the interface between the first and the second layer (top GGST film). The evolution of the composition across the heterostructure interface and information on interdiffusion were obtained. We found that, for both cases, the final composition of the GGST layer was close to Ge2SbTe2 (GST212), which is a thermodynamically favorable off-stoichiometry GeSbTe alloy in the Sb-GeTe pseudobinary of the ternary phase diagram. Density functional theory calculations allowed us to calculate the density of states for the valence band of the amorphous phase of GST212, which was in good agreement with the experimental valence bands measured in situ by UPS. The same heterostructures were characterized by X-ray diffraction as a function of the annealing temperature. Differences in the crystallization process are discussed on the basis of the photoemission results.
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Affiliation(s)
- Caroline Chèze
- Dipartimento di Fisica, Università di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Rome, Italy; (C.C.); (G.D.B.); (S.P.); (F.A.)
| | - Flavia Righi Riva
- Dipartimento di Fisica, Università di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Rome, Italy; (C.C.); (G.D.B.); (S.P.); (F.A.)
- Correspondence:
| | - Giulia Di Bella
- Dipartimento di Fisica, Università di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Rome, Italy; (C.C.); (G.D.B.); (S.P.); (F.A.)
- Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy;
| | - Ernesto Placidi
- Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy;
| | - Simone Prili
- Dipartimento di Fisica, Università di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Rome, Italy; (C.C.); (G.D.B.); (S.P.); (F.A.)
| | - Marco Bertelli
- Istituto per la Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche (CNR), Via del Fosso del Cavaliere 100, 00133 Rome, Italy; (M.B.); (A.D.F.); (M.L.); (R.C.)
| | - Adriano Diaz Fattorini
- Istituto per la Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche (CNR), Via del Fosso del Cavaliere 100, 00133 Rome, Italy; (M.B.); (A.D.F.); (M.L.); (R.C.)
| | - Massimo Longo
- Istituto per la Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche (CNR), Via del Fosso del Cavaliere 100, 00133 Rome, Italy; (M.B.); (A.D.F.); (M.L.); (R.C.)
| | - Raffaella Calarco
- Istituto per la Microelettronica e Microsistemi (IMM), Consiglio Nazionale delle Ricerche (CNR), Via del Fosso del Cavaliere 100, 00133 Rome, Italy; (M.B.); (A.D.F.); (M.L.); (R.C.)
| | - Marco Bernasconi
- Department of Materials Science, University of Milano-Bicocca, Via R. Cozzi 55, 20125 Milan, Italy; (M.B.); (O.A.E.K.)
| | - Omar Abou El Kheir
- Department of Materials Science, University of Milano-Bicocca, Via R. Cozzi 55, 20125 Milan, Italy; (M.B.); (O.A.E.K.)
| | - Fabrizio Arciprete
- Dipartimento di Fisica, Università di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Rome, Italy; (C.C.); (G.D.B.); (S.P.); (F.A.)
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7
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Cecchi S, Lopez Garcia I, Mio AM, Zallo E, Abou El Kheir O, Calarco R, Bernasconi M, Nicotra G, Privitera SMS. Crystallization and Electrical Properties of Ge-Rich GeSbTe Alloys. NANOMATERIALS 2022; 12:nano12040631. [PMID: 35214960 PMCID: PMC8876497 DOI: 10.3390/nano12040631] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 01/31/2022] [Accepted: 02/08/2022] [Indexed: 01/27/2023]
Abstract
Enrichment of GeSbTe alloys with germanium has been proposed as a valid approach to increase the crystallization temperature and therefore to address high-temperature applications of non-volatile phase change memories, such as embedded or automotive applications. However, the tendency of Ge-rich GeSbTe alloys to decompose with the segregation of pure Ge still calls for investigations on the basic mechanisms leading to element diffusion and compositional variations. With the purpose of identifying some possible routes to limit the Ge segregation, in this study, we investigate Ge-rich Sb2Te3 and Ge-rich Ge2Sb2Te5 with low (<40 at %) or high (>40 at %) amounts of Ge. The formation of the crystalline phases has been followed as a function of annealing temperature by X-ray diffraction. The temperature dependence of electrical properties has been evaluated by in situ resistance measurements upon annealing up to 300 °C. The segregation and decomposition processes have been studied by scanning transmission electron microscopy (STEM) and discussed on the basis of density functional theory calculations. Among the studied compositions, Ge-rich Ge2Sb2Te5 is found to be less prone to decompose with Ge segregation.
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Affiliation(s)
- Stefano Cecchi
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V., Hausvogteiplatz 5–7, 10117 Berlin, Germany; (E.Z.); (R.C.)
- Department of Materials Science, University of Milano-Bicocca, via R. Cozzi 55, 20125 Milano, Italy; (O.A.E.K.); (M.B.)
- Correspondence:
| | - Iñaki Lopez Garcia
- Institute for Microelectronic and Microsystems (IMM), National Research Council (CNR), Zona Industriale Ottava Strada 5, 95121 Catania, Italy; (I.L.G.); (A.M.M.); (G.N.); (S.M.S.P.)
| | - Antonio M. Mio
- Institute for Microelectronic and Microsystems (IMM), National Research Council (CNR), Zona Industriale Ottava Strada 5, 95121 Catania, Italy; (I.L.G.); (A.M.M.); (G.N.); (S.M.S.P.)
| | - Eugenio Zallo
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V., Hausvogteiplatz 5–7, 10117 Berlin, Germany; (E.Z.); (R.C.)
- Walter Schottky Institut, Physik Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
| | - Omar Abou El Kheir
- Department of Materials Science, University of Milano-Bicocca, via R. Cozzi 55, 20125 Milano, Italy; (O.A.E.K.); (M.B.)
| | - Raffaella Calarco
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V., Hausvogteiplatz 5–7, 10117 Berlin, Germany; (E.Z.); (R.C.)
- Institute for Microelectronic and Microsystems (IMM), National Research Council (CNR), Via del Fosso del Cavaliere 100, 00133 Roma, Italy
| | - Marco Bernasconi
- Department of Materials Science, University of Milano-Bicocca, via R. Cozzi 55, 20125 Milano, Italy; (O.A.E.K.); (M.B.)
| | - Giuseppe Nicotra
- Institute for Microelectronic and Microsystems (IMM), National Research Council (CNR), Zona Industriale Ottava Strada 5, 95121 Catania, Italy; (I.L.G.); (A.M.M.); (G.N.); (S.M.S.P.)
| | - Stefania M. S. Privitera
- Institute for Microelectronic and Microsystems (IMM), National Research Council (CNR), Zona Industriale Ottava Strada 5, 95121 Catania, Italy; (I.L.G.); (A.M.M.); (G.N.); (S.M.S.P.)
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