1
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Zhang H, Li M, Mi SB, Cheng SD, Lu L, Chen ZG. Electron beam lithography of GeTe through polymorphic phase transformation. NANOSCALE HORIZONS 2024; 9:1574-1581. [PMID: 39034818 DOI: 10.1039/d4nh00035h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/23/2024]
Abstract
We report two previously undiscovered phases of GeTe including the sphalerite (c-) phase and the hexagonal (h-) phase with interlayer van der Waals gaps. A polymorphic phase transformation from rhombohedral α-GeTe to c- and h-GeTe at near room temperature is first realized via electron beam irradiation. Their underlying thermodynamics and kinetics are illustrated using the in situ heating experiments and molecular dynamics simulations. Density-functional theory calculations indicate that c-GeTe exhibits typical metallic behavior and h-GeTe is a narrow-gap semiconductor with a strong spin-orbital coupling effect. Our findings shed light on a strategy for designing GeTe-based quantum devices compromising nanopillars and heterostructures via an atomic-scale electron beam lithography technique.
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Affiliation(s)
- Hu Zhang
- Ji Hua Laboratory, Foshan 528200, China.
- School of Physics and Information Technology, Shaanxi Normal University, Xi'an 710119, China
- State Key Laboratory for Mechanical Behavior of Materials & School of Microelectronics, Xi'an Jiaotong University, Xi'an 710049, China
| | - Meng Li
- School of Chemistry & Physics, Faculty of Science, Queensland University of Technology, Queensland 4000, Australia.
| | - Shao-Bo Mi
- Ji Hua Laboratory, Foshan 528200, China.
| | - Shao-Dong Cheng
- State Key Laboratory for Mechanical Behavior of Materials & School of Microelectronics, Xi'an Jiaotong University, Xi'an 710049, China
| | - Lu Lu
- Ji Hua Laboratory, Foshan 528200, China.
| | - Zhi-Gang Chen
- School of Chemistry & Physics, Faculty of Science, Queensland University of Technology, Queensland 4000, Australia.
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2
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Qu J, Cheng H, Lan H, Zheng B, Luo Z, Yang X, Yi X, Wu G, Chen S, Pan A. Space-Confined Growth of Ultrathin P-Type GeTe Nanosheets for Broadband Photodetectors. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2309391. [PMID: 38456381 DOI: 10.1002/smll.202309391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Revised: 02/18/2024] [Indexed: 03/09/2024]
Abstract
As p-type phase-change degenerate semiconductors, crystalline and amorphous germanium telluride (GeTe) exhibit metallic and semiconducting properties, respectively. However, the massive structural defects and strong interface scattering in amorphous GeTe films significantly reduce their performance. In this work, two-dimensional (2D) p-type GeTe nanosheets are synthesized via a specially designed space-confined chemical vapor deposition (CVD) method, with the thickness of the GeTe nanosheets reduced to 1.9 nm. The space-confined CVD method improves the crystallinity of ultrathin GeTe by lowering the partial pressure of the reactant gas, resulting in GeTe nanosheets with excellent p-type semiconductor properties, such as a satisfactory on/off ratio of 105. Temperature-dependent electrical measurements demonstrate that variable-range hopping and optical-phonon-assisted hopping mechanisms dominate transport behavior at low and high temperatures, respectively. GeTe devices exhibit significantly high responsivity (6589 and 2.2 A W-1 at 633 and 980 nm, respectively) and detectivity (1.67 × 1011 and 1.3 × 108 Jones at 633 and 980 nm, respectively), making them feasible for broadband photodetectors in the visible to near-infrared range. Furthermore, the fabricated GeTe/WS2 diode exhibits a rectification ratio of 103 at zero gate voltage. These satisfactory p-type semiconductor properties demonstrate that ultrathin GeTe exhibits enormous potential for applications in optoelectronic interconnection circuits.
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Affiliation(s)
- Junyu Qu
- Hunan Institute of Optoelectronic Integration, Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha, Hunan, 410082, P. R. China
| | - Haodong Cheng
- Hunan Institute of Optoelectronic Integration, Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha, Hunan, 410082, P. R. China
| | - Huiping Lan
- Hunan Institute of Optoelectronic Integration, Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha, Hunan, 410082, P. R. China
| | - Biyuan Zheng
- Hunan Institute of Optoelectronic Integration, Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha, Hunan, 410082, P. R. China
| | - Ziyu Luo
- Hunan Institute of Optoelectronic Integration, Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha, Hunan, 410082, P. R. China
| | - Xin Yang
- Hunan Institute of Optoelectronic Integration, Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha, Hunan, 410082, P. R. China
| | - Xiao Yi
- Hunan Institute of Optoelectronic Integration, Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha, Hunan, 410082, P. R. China
| | - Guangcheng Wu
- Hunan Institute of Optoelectronic Integration, Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha, Hunan, 410082, P. R. China
| | - Shula Chen
- Hunan Institute of Optoelectronic Integration, Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha, Hunan, 410082, P. R. China
| | - Anlian Pan
- Hunan Institute of Optoelectronic Integration, Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha, Hunan, 410082, P. R. China
- School of Physics and Electronics, Hunan Normal University, Changsha, Hunan, 410081, P. R. China
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3
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Furci M, Marini G, Calandra M. First-Order Rhombohedral-to-Cubic Phase Transition in Photoexcited GeTe. PHYSICAL REVIEW LETTERS 2024; 132:236101. [PMID: 38905679 DOI: 10.1103/physrevlett.132.236101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Accepted: 04/23/2024] [Indexed: 06/23/2024]
Abstract
Photoexcited GeTe undergoes a nonthermal phase transition from a rhombohedral to a rocksalt crystalline phase. The microscopic mechanism and the nature of the transition are unclear. By using constrained density functional perturbation theory and by accounting for quantum anharmonicity within the stochastic self-consistent harmonic approximation, we show that the nonthermal phase transition is strongly first order and does not involve phonon softening, at odds with the thermal one. The transition is driven by the closure of the single particle gap in the photoexcited rhombohedral phase. Finally, we show that ultrafast x-ray diffraction data are consistent with a coexistence of the two phases, as expected in a first order transition. Our results are relevant for the understanding of phase transitions and bonding in phase change materials.
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Affiliation(s)
- Matteo Furci
- Department of Physics, University of Trento, Via Sommarive 14, 38123 Povo, Italy
| | - Giovanni Marini
- Graphene Labs, Fondazione Istituto Italiano di Tecnologia, Via Morego, I-16163 Genova, Italy
| | - Matteo Calandra
- Department of Physics, University of Trento, Via Sommarive 14, 38123 Povo, Italy
- Graphene Labs, Fondazione Istituto Italiano di Tecnologia, Via Morego, I-16163 Genova, Italy
- Sorbonne Université, CNRS, Institut des Nanosciences de Paris, UMR7588, F-75252 Paris, France
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4
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Krizman G, Zakusylo T, Sajeev L, Hajlaoui M, Takashiro T, Rosmus M, Olszowska N, Kołodziej JJ, Bauer G, Caha O, Springholz G. A Novel Ferroelectric Rashba Semiconductor. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023:e2310278. [PMID: 38100676 DOI: 10.1002/adma.202310278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Revised: 12/08/2023] [Indexed: 12/17/2023]
Abstract
Fast, reversible, and low-power manipulation of the spin texture is crucial for next generation spintronic devices like non-volatile bipolar memories, switchable spin current injectors or spin field effect transistors. Ferroelectric Rashba semiconductors (FERSC) are the ideal class of materials for the realization of such devices. Their ferroelectric character enables an electronic control of the Rashba-type spin texture by means of the reversible and switchable polarization. Yet, only very few materials are established to belong to this class of multifunctional materials. Here, Pb1- x Gex Te is unraveled as a novel FERSC system down to nanoscale. The ferroelectric phase transition and concomitant lattice distortion are demonstrated by temperature dependent X-ray diffraction, and their effect on electronic properties are measured by angle-resolved photoemission spectroscopy. In few nanometer-thick epitaxial heterostructures, a large Rashba spin-splitting is exhibiting a wide tuning range as a function of temperature and Ge content. This work defines Pb1- x Gex Te as a high-potential FERSC system for spintronic applications.
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Affiliation(s)
- Gauthier Krizman
- Institut für Halbleiter und Festkörperphysik, Johannes Kepler Universität, Altenberger Strasse 69, Linz, 4040, Austria
| | - Tetiana Zakusylo
- Institut für Halbleiter und Festkörperphysik, Johannes Kepler Universität, Altenberger Strasse 69, Linz, 4040, Austria
| | - Lakshmi Sajeev
- Department of Condensed Matter Physics, Masaryk University, Kotlárská 2, Brno, 61137, Czech Republic
| | - Mahdi Hajlaoui
- Institut für Halbleiter und Festkörperphysik, Johannes Kepler Universität, Altenberger Strasse 69, Linz, 4040, Austria
| | - Takuya Takashiro
- Institut für Halbleiter und Festkörperphysik, Johannes Kepler Universität, Altenberger Strasse 69, Linz, 4040, Austria
| | - Marcin Rosmus
- National Synchrotron Radiation Centre SOLARIS, Jagiellonian University, Czerwone Maki 98, Krakow, 30-392, Poland
| | - Natalia Olszowska
- National Synchrotron Radiation Centre SOLARIS, Jagiellonian University, Czerwone Maki 98, Krakow, 30-392, Poland
| | - Jacek J Kołodziej
- National Synchrotron Radiation Centre SOLARIS, Jagiellonian University, Czerwone Maki 98, Krakow, 30-392, Poland
- Faculty of Physics, Astronomy and Applied Computer Science, Jagiellonian University, Ul. Prof. Stanislawa Lojasiewizca 11, Krakow, 30-348, Poland
| | - Günther Bauer
- Institut für Halbleiter und Festkörperphysik, Johannes Kepler Universität, Altenberger Strasse 69, Linz, 4040, Austria
| | - Ondrej Caha
- Department of Condensed Matter Physics, Masaryk University, Kotlárská 2, Brno, 61137, Czech Republic
| | - Gunther Springholz
- Institut für Halbleiter und Festkörperphysik, Johannes Kepler Universität, Altenberger Strasse 69, Linz, 4040, Austria
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5
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Tiwari RP. Enhanced shift current bulk photovoltaic effect in ferroelectric Rashba semiconductor α-GeTe: ab initiostudy from three- to two-dimensional van der Waals layered structures. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:435404. [PMID: 35985305 DOI: 10.1088/1361-648x/ac8b50] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Accepted: 08/19/2022] [Indexed: 06/15/2023]
Abstract
The ferroelectric Rashba semiconductors (FERSCs) are endowed with a unique combination of ferroelectricity and the spin degree of freedom, resulting in a long carrier lifetime and impressive bulk photovoltaic (BPV) efficiency that reached 25% in organometal halide perovskites. The BPV efficiency can be further improved by using low-dimensional ferroelectrics however, it is inhibited by the ferroelectric instability in low-dimensional perovskites and toxicity along with phase instability of the lead-halide perovskites. To address these challenges, theα-GeTe could be of great importance which is the simplest known lead-free FERSC with an intrinsic layered structure. Therefore, in this work, we investigate the BPV properties of three- to two-dimensional van der Waals structures ofα-GeTe by calculating the shift current (SHC). We predict that the mono (1.56 Å) and bi-layers (5.44-6.14 Å)α-GeTe with the buckled honeycomb structure are dynamically stable and possess the characteristic features of the bulk up to the nanoscale limit. The SHC of ∼70μA V-2is calculated in bulk α-GeTe which is 20 times larger than that obtained in organometal halides in the visible light. The SHC increases with decreasing the number of layers, reaching a maximum amplitude of ∼300μA V-2at 2.67 eV in the monolayer which is more than double that obtained in monolayer GeS. We find that the SHC in monolayer α-GeTe can be further enhanced and redshifted by applying a compressive strain; which is correlated with the strong absorption of thexx-polarized light, stimulated by the more delocalized px/yorbital character of the density of states. Furthermore, in the bilayer structures, the magnitude of the SHC is sensitive to the layers' stacking arrangement and a maximum SHC (∼250μA V-2) can be achieved with an AB-type stacking arrangement. Combining these results with the benefits of being environmental-friendly material makesα-GeTe a good candidate for next-generation solar cells application.
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6
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Stereochemical expression of ns2 electron pairs in metal halide perovskites. Nat Rev Chem 2021; 5:838-852. [PMID: 37117392 DOI: 10.1038/s41570-021-00335-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/07/2021] [Indexed: 12/20/2022]
Abstract
Metal halide perovskites (MHPs) are characterized as strongly anharmonic and dynamic lattices. While there is a consensus on the solvation-like polarization effect in these materials, whether static polarization, that is, ferroelectricity, exists or not in 3D MHPs remains controversial. In this Review, we resolve this controversy by analysing the stereochemical expression (SE) of the ns2 electron pair (NSEP) on group IV metal cations. The SE-NSEP is key to lattice instability, which governs the breaking of inversion symmetry and induces ferroelectricity. The SE-NSEP is diminishingly small in commonly studied 3D lead iodide or bromide perovskites, indicating an absence of ferroelectricity. In contrast, 2D MHPs promote the SE-NSEP and produce unambiguous ferroelectricity or antiferroelectricity. Irrespective of ferroelectricity, the dynamic manifestation of the SE-NSEP provides the missing link to understanding polar fluctuations and efficient dielectric screening in MHPs, thus, contributing to the long carrier lifetimes and diffusion lengths.
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7
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Singh K, Kumari S, Singh H, Bala N, Singh P, Kumar A, Thakur A. A review on GeTe thin film-based phase-change materials. APPLIED NANOSCIENCE 2021. [DOI: 10.1007/s13204-021-01911-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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8
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Micro-Structure Changes Caused by Thermal Evolution in Chalcogenide Ge xAs ySe 1-x-y Thin Films by In Situ Measurements. MATERIALS 2021; 14:ma14102572. [PMID: 34063433 PMCID: PMC8156157 DOI: 10.3390/ma14102572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 05/10/2021] [Accepted: 05/11/2021] [Indexed: 11/25/2022]
Abstract
To understand the effects of thermal annealing on the structure of GexAsySe1−x−y thin films, the thermal evolution of these films was measured by the in situ X-ray diffraction (XRD) at different temperature (773 K or 1073 K) in a vacuum (10−1 Pa) environment. The entire process of crystallization can be observed by using in situ XRD, which is from the appearance of a crystal structure to melting liquid-state and ultimately to the disappearance of the amorphous structure. In the crystallized process, the corresponding state-transition temperatures Tx (the onset crystallization temperature), Tl (the transition temperature from glassy-state to liquid-state), Tp (peak crystallization temperature) are linear with MCN (Mean Coordination Number). In order to obtain information about changes in the amorphous structural origin of the anneal-induced material, the samples were analyzed by in situ Raman spectroscopy. Analysis of the results through decomposing the Raman spectra into different structural units showed that the Ge−Ge, As−As, or Se−Se homopolar bonds as the nonequilibrium minority carriers could be found in films. It suggests that the formation of these bonds cannot be completely suppressed in any case, as one falls and another rises.
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9
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Bergeron H, Lebedev D, Hersam MC. Polymorphism in Post-Dichalcogenide Two-Dimensional Materials. Chem Rev 2021; 121:2713-2775. [PMID: 33555868 DOI: 10.1021/acs.chemrev.0c00933] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Two-dimensional (2D) materials exhibit a wide range of atomic structures, compositions, and associated versatility of properties. Furthermore, for a given composition, a variety of different crystal structures (i.e., polymorphs) can be observed. Polymorphism in 2D materials presents a fertile landscape for designing novel architectures and imparting new functionalities. The objective of this Review is to identify the polymorphs of emerging 2D materials, describe their polymorph-dependent properties, and outline methods used for polymorph control. Since traditional 2D materials (e.g., graphene, hexagonal boron nitride, and transition metal dichalcogenides) have already been studied extensively, the focus here is on polymorphism in post-dichalcogenide 2D materials including group III, IV, and V elemental 2D materials, layered group III, IV, and V metal chalcogenides, and 2D transition metal halides. In addition to providing a comprehensive survey of recent experimental and theoretical literature, this Review identifies the most promising opportunities for future research including how 2D polymorph engineering can provide a pathway to materials by design.
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Affiliation(s)
- Hadallia Bergeron
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Dmitry Lebedev
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Mark C Hersam
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States.,Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States.,Department of Electrical and Computer Engineering, Northwestern University, Evanston, Illinois 60208, United States
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10
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Flux periodic oscillations and phase-coherent transport in GeTe nanowire-based devices. Nat Commun 2021; 12:754. [PMID: 33531502 PMCID: PMC7854721 DOI: 10.1038/s41467-021-21042-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Accepted: 01/05/2021] [Indexed: 11/09/2022] Open
Abstract
Despite the fact that GeTe is known to be a very interesting material for applications in thermoelectrics and for phase-change memories, the knowledge on its low-temperature transport properties is only limited. We report on phase-coherent phenomena in the magnetotransport of GeTe nanowires. From universal conductance fluctuations measured on GeTe nanowires with Au contacts, a phase-coherence length of about 280 nm at 0.5 K is determined. The distinct phase-coherence is confirmed by the observation of Aharonov-Bohm type oscillations for parallel magnetic fields. We interpret the occurrence of these magnetic flux-periodic oscillations by the formation of a tubular hole accumulation layer. For Nb/GeTe-nanowire/Nb Josephson junctions we obtained a critical current of 0.2 μA at 0.4 K. By applying a perpendicular magnetic field the critical current decreases monotonously with increasing field, whereas in a parallel field the critical current oscillates with a period of the magnetic flux quantum confirming the presence of a tubular hole channel.
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11
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Park H, Watanabe T, Yoda I, Shohmitsu Y, Kawasaki S, Nakaoka T. Reversible and irreversible resistance changes for gamma-ray irradiation in silver-diffused germanium telluride. SN APPLIED SCIENCES 2020. [DOI: 10.1007/s42452-020-03927-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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12
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Kriener M, Sakano M, Kamitani M, Bahramy MS, Yukawa R, Horiba K, Kumigashira H, Ishizaka K, Tokura Y, Taguchi Y. Evolution of Electronic States and Emergence of Superconductivity in the Polar Semiconductor GeTe by Doping Valence-Skipping Indium. PHYSICAL REVIEW LETTERS 2020; 124:047002. [PMID: 32058775 DOI: 10.1103/physrevlett.124.047002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Indexed: 06/10/2023]
Abstract
GeTe is a chemically simple IV-VI semiconductor which bears a rich plethora of different physical properties induced by doping and external stimuli. Here, we report a superconductor-semiconductor-superconductor transition controlled by finely-tuned In doping. Our results reveal the existence of a critical doping concentration x_{c}=0.12 in Ge_{1-x}In_{x}Te, where various properties, including structure, resistivity, charge carrier type, and the density of states, take either an extremum or change their character. At the same time, we find indications of a change in the In-valence state from In^{3+} to In^{1+} with increasing x by core-level photoemission spectroscopy, suggesting that this system is a new promising playground to probe valence fluctuations and their possible impact on structural, electronic, and thermodynamic properties of their host.
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Affiliation(s)
- M Kriener
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - M Sakano
- Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656, Japan
| | - M Kamitani
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - M S Bahramy
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
- Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656, Japan
| | - R Yukawa
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - K Horiba
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
| | - H Kumigashira
- Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai 980-8577, Japan
| | - K Ishizaka
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
- Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656, Japan
| | - Y Tokura
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
- Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656, Japan
- Tokyo College, University of Tokyo, Tokyo 113-8656, Japan
| | - Y Taguchi
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
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13
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Features of the High-Temperature Structural Evolution of GeTe Thermoelectric Probed by Neutron and Synchrotron Powder Diffraction. METALS 2019. [DOI: 10.3390/met10010048] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Among other chalcogenide thermoelectric materials, GeTe and derivative alloys are good candidates for intermediate temperature applications, as a replacement for toxic PbTe. We have prepared pure polycrystalline GeTe by using arc-melting, and investigated its structural evolution by using neutron powder diffraction (NPD) and synchrotron X-ray diffraction (SXRD), as well as its correlation with the thermal variation of the Seebeck coefficient. Besides a significant Ge deficiency (~7% Ge vacancies), the thermal evolution of the unit-cell volume and Ge-Te bond lengths in the rhombohedral phase (space group R3m), below 700 K, show unexpected anomalies involving the abrupt Ge-Te bond lengthening accompanied by increased Te thermal displacements. Above 700 K, the sample is cubic (space group Fm-3m) and shows considerably larger displacement parameters for Ge than for Te, as a consequence of the random distribution of the lone pair lobes of Ge2+. The Seebeck coefficient, reaching 120 μV K−1 at 775 K, shows a shoulder in the 500–570 K region that can be correlated to the structural anomaly, modifying the electron-phonon scattering in this temperature range.
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14
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Nam J, Lee H, Lee M, Lee JH. Nonvolatile Balanced Ternary Memory Based on The Multiferroelectric Material GeSnTe 2. J Phys Chem Lett 2019; 10:7470-7474. [PMID: 31735031 DOI: 10.1021/acs.jpclett.9b02956] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Modern computer technology is based on the binary logic system. However, the slowdown of its development calls for transition to multivalued logic (MVL) systems. MVL can yield a denser logic implementation on the same chip area at low cost. More information can be transmitted with the same digits over fewer interconnections, thereby reducing power dissipation. Here, we suggest a novel nonvolatile balanced ternary memory based on the multiferroelectric material GeSnTe2. Two different directions and quantities of electric polarization are found to be stable in atomic-thick two-dimensional structures. The balanced ternary data set of {-1, 0, +1} can be implemented in the two-dimensional material on the nanometer scale. One-shot read/write processes are suggested.
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Affiliation(s)
- Jisoo Nam
- School of Energy and Chemical Engineering , Ulsan National Institute of Science and Technology (UNIST) , Ulsan 44919 , Korea
| | - Hosik Lee
- School of Energy and Chemical Engineering , Ulsan National Institute of Science and Technology (UNIST) , Ulsan 44919 , Korea
| | - Minseong Lee
- School of Energy and Chemical Engineering , Ulsan National Institute of Science and Technology (UNIST) , Ulsan 44919 , Korea
| | - Jun Hee Lee
- School of Energy and Chemical Engineering , Ulsan National Institute of Science and Technology (UNIST) , Ulsan 44919 , Korea
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15
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Hawken SL, Huang R, de Groot CH(K, Hector AL, Jura M, Levason W, Reid G, Stenning GBG. [Ge(Te nBu) 4] – a single source precursor for the chemical vapour deposition of germanium telluride thin films. Dalton Trans 2019; 48:117-124. [DOI: 10.1039/c8dt03263g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Reaction of activated germanium with nBu2Te2 in THF solution was shown to be more effective for the preparation of the germanium(iv) tellurolate compound, [Ge(TenBu)4], than reaction of GeCl4 with LiTenBu in THF.
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Affiliation(s)
| | - Ruomeng Huang
- School of Electronics and Computer Science
- University of Southampton
- Southampton SO17 1BJ
- UK
| | - C. H. (Kees) de Groot
- School of Electronics and Computer Science
- University of Southampton
- Southampton SO17 1BJ
- UK
| | - Andrew L. Hector
- School of Chemistry
- University of Southampton
- Southampton SO17 1BJ
- UK
| | - Marek Jura
- ISIS Neutron and Muon Source
- Rutherford Appleton Laboratory
- Harwell Science and Innovation Campus
- Didcot
- UK
| | - William Levason
- School of Chemistry
- University of Southampton
- Southampton SO17 1BJ
- UK
| | - Gillian Reid
- School of Chemistry
- University of Southampton
- Southampton SO17 1BJ
- UK
| | - Gavin B. G. Stenning
- ISIS Neutron and Muon Source
- Rutherford Appleton Laboratory
- Harwell Science and Innovation Campus
- Didcot
- UK
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16
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In situ monitoring of stress change in GeTe thin films during thermal annealing and crystallization. MICRO AND NANO ENGINEERING 2018. [DOI: 10.1016/j.mne.2018.10.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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17
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Yarema O, Perevedentsev A, Ovuka V, Baade P, Volk S, Wood V, Yarema M. Colloidal Phase-Change Materials: Synthesis of Monodisperse GeTe Nanoparticles and Quantification of Their Size-Dependent Crystallization. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2018; 30:6134-6143. [PMID: 30270986 DOI: 10.1021/acs.chemmater.7b04710] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 08/19/2018] [Indexed: 05/28/2023]
Abstract
Phase-change memory materials refer to a class of materials that can exist in amorphous and crystalline phases with distinctly different electrical or optical properties, as well as exhibit outstanding crystallization kinetics and optimal phase transition temperatures. This paper focuses on the potential of colloids as phase-change memory materials. We report a novel synthesis for amorphous GeTe nanoparticles based on an amide-promoted approach that enables accurate size control of GeTe nanoparticles between 4 and 9 nm, narrow size distributions down to 9-10%, and synthesis upscaling to reach multigram chemical yields per batch. We then quantify the crystallization phase transition for GeTe nanoparticles, employing high-temperature X-ray diffraction, differential scanning calorimetry, and transmission electron microscopy. We show that GeTe nanoparticles crystallize at higher temperatures than the bulk GeTe material and that crystallization temperature increases with decreasing size. We can explain this size-dependence using the entropy of crystallization model and classical nucleation theory. The size-dependences quantified here highlight possible benefits of nanoparticles for phase-change memory applications.
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Affiliation(s)
- Olesya Yarema
- Materials and Device Engineering Group, Department of Information Technology and Electrical Engineering, ETH Zurich, Gloriastrasse 35, CH-8092 Zurich, Switzerland
| | - Aleksandr Perevedentsev
- Polymer Technology, Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 5, CH-8093 Zurich, Switzerland
| | - Vladimir Ovuka
- Materials and Device Engineering Group, Department of Information Technology and Electrical Engineering, ETH Zurich, Gloriastrasse 35, CH-8092 Zurich, Switzerland
| | - Paul Baade
- Materials and Device Engineering Group, Department of Information Technology and Electrical Engineering, ETH Zurich, Gloriastrasse 35, CH-8092 Zurich, Switzerland
| | - Sebastian Volk
- Materials and Device Engineering Group, Department of Information Technology and Electrical Engineering, ETH Zurich, Gloriastrasse 35, CH-8092 Zurich, Switzerland
| | - Vanessa Wood
- Materials and Device Engineering Group, Department of Information Technology and Electrical Engineering, ETH Zurich, Gloriastrasse 35, CH-8092 Zurich, Switzerland
| | - Maksym Yarema
- Materials and Device Engineering Group, Department of Information Technology and Electrical Engineering, ETH Zurich, Gloriastrasse 35, CH-8092 Zurich, Switzerland
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18
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Yarema O, Perevedentsev A, Ovuka V, Baade P, Volk S, Wood V, Yarema M. Colloidal Phase-Change Materials: Synthesis of Monodisperse GeTe Nanoparticles and Quantification of Their Size-Dependent Crystallization. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2018; 30:6134-6143. [PMID: 30270986 PMCID: PMC6156088 DOI: 10.1021/acs.chemmater.8b02702] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 08/19/2018] [Indexed: 05/31/2023]
Abstract
Phase-change memory materials refer to a class of materials that can exist in amorphous and crystalline phases with distinctly different electrical or optical properties, as well as exhibit outstanding crystallization kinetics and optimal phase transition temperatures. This paper focuses on the potential of colloids as phase-change memory materials. We report a novel synthesis for amorphous GeTe nanoparticles based on an amide-promoted approach that enables accurate size control of GeTe nanoparticles between 4 and 9 nm, narrow size distributions down to 9-10%, and synthesis upscaling to reach multigram chemical yields per batch. We then quantify the crystallization phase transition for GeTe nanoparticles, employing high-temperature X-ray diffraction, differential scanning calorimetry, and transmission electron microscopy. We show that GeTe nanoparticles crystallize at higher temperatures than the bulk GeTe material and that crystallization temperature increases with decreasing size. We can explain this size-dependence using the entropy of crystallization model and classical nucleation theory. The size-dependences quantified here highlight possible benefits of nanoparticles for phase-change memory applications.
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Affiliation(s)
- Olesya Yarema
- Materials
and Device Engineering Group, Department of Information Technology
and Electrical Engineering, ETH Zurich, Gloriastrasse 35, CH-8092 Zurich, Switzerland
| | - Aleksandr Perevedentsev
- Polymer
Technology, Department of Materials, ETH
Zurich, Vladimir-Prelog-Weg 5, CH-8093 Zurich, Switzerland
| | - Vladimir Ovuka
- Materials
and Device Engineering Group, Department of Information Technology
and Electrical Engineering, ETH Zurich, Gloriastrasse 35, CH-8092 Zurich, Switzerland
| | - Paul Baade
- Materials
and Device Engineering Group, Department of Information Technology
and Electrical Engineering, ETH Zurich, Gloriastrasse 35, CH-8092 Zurich, Switzerland
| | - Sebastian Volk
- Materials
and Device Engineering Group, Department of Information Technology
and Electrical Engineering, ETH Zurich, Gloriastrasse 35, CH-8092 Zurich, Switzerland
| | - Vanessa Wood
- Materials
and Device Engineering Group, Department of Information Technology
and Electrical Engineering, ETH Zurich, Gloriastrasse 35, CH-8092 Zurich, Switzerland
| | - Maksym Yarema
- Materials
and Device Engineering Group, Department of Information Technology
and Electrical Engineering, ETH Zurich, Gloriastrasse 35, CH-8092 Zurich, Switzerland
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19
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Sosso GC, Deringer VL, Elliott SR, Csányi G. Understanding the thermal properties of amorphous solids using machine-learning-based interatomic potentials. MOLECULAR SIMULATION 2018. [DOI: 10.1080/08927022.2018.1447107] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Gabriele C. Sosso
- Department of Chemistry and Centre for Scientific Computing, University of Warwick , Coventry, UK
| | - Volker L. Deringer
- Department of Engineering, University of Cambridge , Cambridge, UK
- Department of Chemistry, University of Cambridge , Cambridge, UK
| | | | - Gábor Csányi
- Department of Engineering, University of Cambridge , Cambridge, UK
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20
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Momand J, Boschker JE, Wang R, Calarco R, Kooi BJ. Tailoring the epitaxy of Sb2Te3 and GeTe thin films using surface passivation. CrystEngComm 2018. [DOI: 10.1039/c7ce01825h] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Depending on the substrate surface termination the epitaxy of chalcogenide thin films can be drastically altered. While GeTe grows with many randomly oriented domains on H-terminated Si(111), the in-plane alignment is significantly improved on Sb-terminated Si(111).
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Affiliation(s)
- Jamo Momand
- Zernike Institute for Advanced Materials
- University of Groningen
- Groningen
- The Netherlands
| | - Jos E. Boschker
- Paul-Drude-Institut für Festkörperelektronik
- 10117 Berlin
- Germany
| | - Ruining Wang
- Paul-Drude-Institut für Festkörperelektronik
- 10117 Berlin
- Germany
| | | | - Bart J. Kooi
- Zernike Institute for Advanced Materials
- University of Groningen
- Groningen
- The Netherlands
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21
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Huang Z, Miller SA, Ge B, Yan M, Anand S, Wu T, Nan P, Zhu Y, Zhuang W, Snyder GJ, Jiang P, Bao X. High Thermoelectric Performance of New Rhombohedral Phase of GeSe stabilized through Alloying with AgSbSe 2. Angew Chem Int Ed Engl 2017; 56:14113-14118. [PMID: 28929555 DOI: 10.1002/anie.201708134] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Revised: 09/15/2017] [Indexed: 11/05/2022]
Abstract
GeSe is a IV-VI semiconductor, like the excellent thermoelectric materials PbTe and SnSe. Orthorhombic GeSe has been predicted theoretically to have good thermoelectric performance but is difficult to dope experimentally. Like PbTe, rhombohedral GeTe has a multivalley band structure, which is ideal for thermoelectrics and also promotes the formation of Ge vacancies to provide enough carriers for electrical transport. Herein, we investigate the thermoelectric properties of GeSe alloyed with AgSbSe2 , which stabilizes a new rhombohedral structure with higher symmetry that leads to a multivalley Fermi surface and a dramatic increase in carrier concentration. The zT of GeAg0.2 Sb0.2 Se1.4 reaches 0.86 at 710 K, which is 18 times higher than that of pristine GeSe and over four times higher than doped orthorhombic GeSe. Our results open a new avenue towards developing novel thermoelectric materials through crystal phase engineering using a strategy of entropy stabilization of high-symmetry alloys.
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Affiliation(s)
- Zhiwei Huang
- State Key Laboratory of Catalysis, CAS Center for Excellence in Nanoscience, Institution Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Samuel A Miller
- Materials Science and Engineering Department, Northwestern University, Evanston, Illinois, 60208, USA
| | - Binghui Ge
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Mingtao Yan
- State Key Laboratory of Catalysis, CAS Center for Excellence in Nanoscience, Institution Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Shashwat Anand
- Materials Science and Engineering Department, Northwestern University, Evanston, Illinois, 60208, USA
| | - Tianmin Wu
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, China
| | - Pengfei Nan
- School of Physics, Beijing Institute of Technology, Beijing, 100081, China
| | - Yuanhu Zhu
- State Key Laboratory of Catalysis, CAS Center for Excellence in Nanoscience, Institution Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China
| | - Wei Zhuang
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, China
| | - G Jeffrey Snyder
- Materials Science and Engineering Department, Northwestern University, Evanston, Illinois, 60208, USA
| | - Peng Jiang
- State Key Laboratory of Catalysis, CAS Center for Excellence in Nanoscience, Institution Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China
| | - Xinhe Bao
- State Key Laboratory of Catalysis, CAS Center for Excellence in Nanoscience, Institution Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China
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22
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Huang Z, Miller SA, Ge B, Yan M, Anand S, Wu T, Nan P, Zhu Y, Zhuang W, Snyder GJ, Jiang P, Bao X. High Thermoelectric Performance of New Rhombohedral Phase of GeSe stabilized through Alloying with AgSbSe2. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201708134] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Zhiwei Huang
- State Key Laboratory of Catalysis; CAS Center for Excellence in Nanoscience; Institution Dalian Institute of Chemical Physics; Chinese Academy of Sciences; Dalian Liaoning 116023 China
- University of Chinese Academy of Sciences; Beijing 100049 China
| | - Samuel A. Miller
- Materials Science and Engineering Department; Northwestern University; Evanston Illinois 60208 USA
| | - Binghui Ge
- Beijing National Laboratory for Condensed Matter Physics; Institute of Physics; Chinese Academy of Sciences; Beijing 100190 China
| | - Mingtao Yan
- State Key Laboratory of Catalysis; CAS Center for Excellence in Nanoscience; Institution Dalian Institute of Chemical Physics; Chinese Academy of Sciences; Dalian Liaoning 116023 China
- University of Chinese Academy of Sciences; Beijing 100049 China
| | - Shashwat Anand
- Materials Science and Engineering Department; Northwestern University; Evanston Illinois 60208 USA
| | - Tianmin Wu
- State Key Laboratory of Structural Chemistry; Fujian Institute of Research on the Structure of Matter; Chinese Academy of Sciences; Fuzhou Fujian 350002 China
| | - Pengfei Nan
- School of Physics; Beijing Institute of Technology; Beijing 100081 China
| | - Yuanhu Zhu
- State Key Laboratory of Catalysis; CAS Center for Excellence in Nanoscience; Institution Dalian Institute of Chemical Physics; Chinese Academy of Sciences; Dalian Liaoning 116023 China
| | - Wei Zhuang
- State Key Laboratory of Structural Chemistry; Fujian Institute of Research on the Structure of Matter; Chinese Academy of Sciences; Fuzhou Fujian 350002 China
| | - G. Jeffrey Snyder
- Materials Science and Engineering Department; Northwestern University; Evanston Illinois 60208 USA
| | - Peng Jiang
- State Key Laboratory of Catalysis; CAS Center for Excellence in Nanoscience; Institution Dalian Institute of Chemical Physics; Chinese Academy of Sciences; Dalian Liaoning 116023 China
| | - Xinhe Bao
- State Key Laboratory of Catalysis; CAS Center for Excellence in Nanoscience; Institution Dalian Institute of Chemical Physics; Chinese Academy of Sciences; Dalian Liaoning 116023 China
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