1
|
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.
Collapse
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.)
| |
Collapse
|
2
|
Structural transformation and phase change properties of Se substituted GeTe. Sci Rep 2021; 11:7604. [PMID: 33828186 PMCID: PMC8027648 DOI: 10.1038/s41598-021-87206-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2020] [Accepted: 03/11/2021] [Indexed: 12/02/2022] Open
Abstract
GeTe1−xSex (0 ≤ x ≤ 1.0) alloys have been prepared both in bulk and thin film forms to study the effect of selenium (Se) substitution for tellurium (Te) on the phase change properties. It is observed that with increasing Se substitution in GeTe, the structure transforms from rhombohdral structure to orthorhombic structure. Rietveld Refinement analysis support the phase transformation and show that the short and long bond lengths in crystalline GeTe decrease with increasing Se substitution but the rate of reduction of shorter bond length is more than the longer bond length. The GeTe1−xSex thin films undergo amorphous to crystalline phase change when annealed at high temperatures. The transition temperature shows an increasing trend with the Se substitution. The contrast in electrical resistivity between the amorphous and crystalline states is 104 for GeTe, and with the Se substitution, the contrast increases considerably to 106 for GeTe0.5Se0.5. Devices fabricated with thin films show that the threshold current decreases with the Se substitution indicating a reduction in the power required for WRITE operation. The present study shows that the crystalline structure, resistance, bandgap, transition temperature and threshold voltage of GeTe can be effectively controlled and tuned by the substitution of Te by Se, which is conducive for phase change memory applications.
Collapse
|
3
|
Lotnyk A, Behrens M, Rauschenbach B. Phase change thin films for non-volatile memory applications. NANOSCALE ADVANCES 2019; 1:3836-3857. [PMID: 36132100 PMCID: PMC9419560 DOI: 10.1039/c9na00366e] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Accepted: 09/17/2019] [Indexed: 06/10/2023]
Abstract
The rapid development of Internet of Things devices requires real time processing of a huge amount of digital data, creating a new demand for computing technology. Phase change memory technology based on chalcogenide phase change materials meets many requirements of the emerging memory applications since it is fast, scalable and non-volatile. In addition, phase change memory offers multilevel data storage and can be applied both in neuro-inspired and all-photonic in-memory computing. Furthermore, phase change alloys represent an outstanding class of functional materials having a tremendous variety of industrially relevant characteristics and exceptional material properties. Many efforts have been devoted to understanding these properties with the particular aim to design universal memory. This paper reviews materials science aspects of chalcogenide-based phase change thin films relevant for non-volatile memory applications. Particular emphasis is put on local structure, control of disorder and its impact on material properties, order-disorder transitions and interfacial transformations.
Collapse
Affiliation(s)
- A Lotnyk
- Leibniz Institute of Surface Engineering (IOM) Permoserstr. 15 04318 Leipzig Germany
| | - M Behrens
- Leibniz Institute of Surface Engineering (IOM) Permoserstr. 15 04318 Leipzig Germany
| | - B Rauschenbach
- Leibniz Institute of Surface Engineering (IOM) Permoserstr. 15 04318 Leipzig Germany
| |
Collapse
|
4
|
Zhang Y, Chou JB, Li J, Li H, Du Q, Yadav A, Zhou S, Shalaginov MY, Fang Z, Zhong H, Roberts C, Robinson P, Bohlin B, Ríos C, Lin H, Kang M, Gu T, Warner J, Liberman V, Richardson K, Hu J. Broadband transparent optical phase change materials for high-performance nonvolatile photonics. Nat Commun 2019; 10:4279. [PMID: 31570710 PMCID: PMC6768866 DOI: 10.1038/s41467-019-12196-4] [Citation(s) in RCA: 122] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Accepted: 08/20/2019] [Indexed: 11/23/2022] Open
Abstract
Optical phase change materials (O-PCMs), a unique group of materials featuring exceptional optical property contrast upon a solid-state phase transition, have found widespread adoption in photonic applications such as switches, routers and reconfigurable meta-optics. Current O-PCMs, such as Ge–Sb–Te (GST), exhibit large contrast of both refractive index (Δn) and optical loss (Δk), simultaneously. The coupling of both optical properties fundamentally limits the performance of many applications. Here we introduce a new class of O-PCMs based on Ge–Sb–Se–Te (GSST) which breaks this traditional coupling. The optimized alloy, Ge2Sb2Se4Te1, combines broadband transparency (1–18.5 μm), large optical contrast (Δn = 2.0), and significantly improved glass forming ability, enabling an entirely new range of infrared and thermal photonic devices. We further demonstrate nonvolatile integrated optical switches with record low loss and large contrast ratio and an electrically-addressed spatial light modulator pixel, thereby validating its promise as a material for scalable nonvolatile photonics. Here, the authors introduce optical phase change materials based on Ge-Sb-Se-Te which breaks the coupling between refractive index and optical loss allowing low-loss performance benefits. They demonstrate low losses in nonvolatile photonic circuits and electrical pixelated switching have been demonstrated.
Collapse
Affiliation(s)
- Yifei Zhang
- Department of Materials Science & Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Jeffrey B Chou
- Lincoln Laboratory, Massachusetts Institute of Technology, Lexington, MA, USA.
| | - Junying Li
- Shanghai Key Laboratory of Modern Optical Systems, College of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai, China
| | - Huashan Li
- School of Physics, Sun Yat-sen University, Guangzhou, China
| | - Qingyang Du
- Department of Materials Science & Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Anupama Yadav
- The College of Optics & Photonics, Department of Materials Science and Engineering, University of Central Florida, Orlando, FL, USA
| | - Si Zhou
- Department of Materials, University of Oxford, Oxford, UK
| | - Mikhail Y Shalaginov
- Department of Materials Science & Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Zhuoran Fang
- Department of Materials Science & Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Huikai Zhong
- Department of Materials Science & Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Christopher Roberts
- Lincoln Laboratory, Massachusetts Institute of Technology, Lexington, MA, USA
| | - Paul Robinson
- Lincoln Laboratory, Massachusetts Institute of Technology, Lexington, MA, USA
| | - Bridget Bohlin
- Lincoln Laboratory, Massachusetts Institute of Technology, Lexington, MA, USA
| | - Carlos Ríos
- Department of Materials Science & Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Hongtao Lin
- College of Information Science & Electronic Engineering, Zhejiang University, Hangzhou, China
| | - Myungkoo Kang
- The College of Optics & Photonics, Department of Materials Science and Engineering, University of Central Florida, Orlando, FL, USA
| | - Tian Gu
- Department of Materials Science & Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Jamie Warner
- Department of Materials, University of Oxford, Oxford, UK
| | - Vladimir Liberman
- Lincoln Laboratory, Massachusetts Institute of Technology, Lexington, MA, USA
| | - Kathleen Richardson
- The College of Optics & Photonics, Department of Materials Science and Engineering, University of Central Florida, Orlando, FL, USA
| | - Juejun Hu
- Department of Materials Science & Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
| |
Collapse
|