1
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Shukla P, Nath Acharyya J, Mahawar P, Kumar H, Chandra Joshi P, Kumar Singh V, Vijaya Prakash G, Nagendran S. Germylenes Exhibiting Solid-State Emissions that Extend to NIR. Chemistry 2023; 29:e202301486. [PMID: 37485580 DOI: 10.1002/chem.202301486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Revised: 07/03/2023] [Accepted: 07/20/2023] [Indexed: 07/25/2023]
Abstract
Low-valent main group compounds that fluoresce in the solid-state were previously unknown. To address this, we investigated room-temperature photoluminescence from a series of crystals of germylenes 3-8 in this article; they exhibited emissions nearly reaching the NIR. Germylene carboxylates (3-8) were synthesized by reacting dipyrromethene stabilized germylene pyrrolide (2) with carboxylic acids such as acetic acid, trifluoroacetic acid, benzoic acid, p-cyanobenzoic acid, p-nitrobenzoic acid, and acetylsalicylic acid.
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Affiliation(s)
- Pratima Shukla
- Department of Chemistry, Indian Institute of Technology Delhi (IIT Delhi), Hauz Khas, New Delhi, 110016, India
| | - Jitendra Nath Acharyya
- Nanophotonics Labs, Department of Physics, Indian Institute of Technology Delhi (IIT Delhi), Hauz Khas, New Delhi, 110016, India
| | - Pritam Mahawar
- Department of Chemistry, Indian Institute of Technology Delhi (IIT Delhi), Hauz Khas, New Delhi, 110016, India
| | - Hemant Kumar
- Department of Chemistry, Indian Institute of Technology Delhi (IIT Delhi), Hauz Khas, New Delhi, 110016, India
| | - Prakash Chandra Joshi
- Department of Chemistry, Indian Institute of Technology Delhi (IIT Delhi), Hauz Khas, New Delhi, 110016, India
| | - Vivek Kumar Singh
- Department of Chemistry, Indian Institute of Technology Delhi (IIT Delhi), Hauz Khas, New Delhi, 110016, India
| | - G Vijaya Prakash
- Nanophotonics Labs, Department of Physics, Indian Institute of Technology Delhi (IIT Delhi), Hauz Khas, New Delhi, 110016, India
| | - Selvarajan Nagendran
- Department of Chemistry, Indian Institute of Technology Delhi (IIT Delhi), Hauz Khas, New Delhi, 110016, India
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2
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Yang S, Sui F, Liu Y, Qi R, Feng X, Dong S, Yang P, Yue F. Anisotropy and thermal properties in GeTe semiconductor by Raman analysis. NANOSCALE 2023; 15:13297-13303. [PMID: 37539838 DOI: 10.1039/d3nr02678g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/05/2023]
Abstract
Low-symmetric GeTe semiconductors have attracted wide-ranging attention due to their excellent optical and thermal properties, but only a few research studies are available on their in-plane optical anisotropic nature that is crucial for their applications in optoelectronic and thermoelectric devices. Here, we investigate the optical interactions of anisotropy in GeTe using polarization-resolved Raman spectroscopy and first-principles calculations. After determining both armchair and zigzag directions in GeTe crystals by transmission electron microscopy, we found that the Raman intensity of the two main vibrational modes had a strong in-plane anisotropic nature; the one at ∼88.1 cm-1 can be used to determine the crystal orientation, and the other at ∼124.6 cm-1 can reveal a series of temperature-dependent phase transitions. These results provide a general approach for the investigation of the anisotropy of light-matter interactions in low-symmetric layered materials, benefiting the design and application of optoelectronic, anisotropic thermoelectric, and phase-transition memory devices based on bulk GeTe.
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Affiliation(s)
- Shuai Yang
- Key Laboratory of Polar Materials and Devices (MOE), Department of Electronics, East China Normal University, Shanghai 200241, China.
| | - Fengrui Sui
- Key Laboratory of Polar Materials and Devices (MOE), Department of Electronics, East China Normal University, Shanghai 200241, China.
| | - Yucheng Liu
- Key Laboratory of Polar Materials and Devices (MOE), Department of Electronics, East China Normal University, Shanghai 200241, China.
| | - Ruijuan Qi
- Key Laboratory of Polar Materials and Devices (MOE), Department of Electronics, East China Normal University, Shanghai 200241, China.
| | - Xiaoyu Feng
- Key Laboratory of Polar Materials and Devices (MOE), Department of Electronics, East China Normal University, Shanghai 200241, China.
| | - Shangwei Dong
- Key Laboratory of Polar Materials and Devices (MOE), Department of Electronics, East China Normal University, Shanghai 200241, China.
| | - Pingxiong Yang
- Key Laboratory of Polar Materials and Devices (MOE), Department of Electronics, East China Normal University, Shanghai 200241, China.
| | - Fangyu Yue
- Key Laboratory of Polar Materials and Devices (MOE), Department of Electronics, East China Normal University, Shanghai 200241, China.
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3
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Kumaar D, Can M, Portner K, Weigand H, Yarema O, Wintersteller S, Schenk F, Boskovic D, Pharizat N, Meinert R, Gilshtein E, Romanyuk Y, Karvounis A, Grange R, Emboras A, Wood V, Yarema M. Colloidal Ternary Telluride Quantum Dots for Tunable Phase Change Optics in the Visible and Near-Infrared. ACS NANO 2023; 17:6985-6997. [PMID: 36971128 PMCID: PMC10100560 DOI: 10.1021/acsnano.3c01187] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 03/23/2023] [Indexed: 06/18/2023]
Abstract
A structural change between amorphous and crystalline phase provides a basis for reliable and modular photonic and electronic devices, such as nonvolatile memory, beam steerers, solid-state reflective displays, or mid-IR antennas. In this paper, we leverage the benefits of liquid-based synthesis to access phase-change memory tellurides in the form of colloidally stable quantum dots. We report a library of ternary MxGe1-xTe colloids (where M is Sn, Bi, Pb, In, Co, Ag) and then showcase the phase, composition, and size tunability for Sn-Ge-Te quantum dots. Full chemical control of Sn-Ge-Te quantum dots permits a systematic study of structural and optical properties of this phase-change nanomaterial. Specifically, we report composition-dependent crystallization temperature for Sn-Ge-Te quantum dots, which is notably higher compared to bulk thin films. This gives the synergistic benefit of tailoring dopant and material dimension to combine the superior aging properties and ultrafast crystallization kinetics of bulk Sn-Ge-Te, while improving memory data retention due to nanoscale size effects. Furthermore, we discover a large reflectivity contrast between amorphous and crystalline Sn-Ge-Te thin films, exceeding 0.7 in the near-IR spectrum region. We utilize these excellent phase-change optical properties of Sn-Ge-Te quantum dots along with liquid-based processability for nonvolatile multicolor images and electro-optical phase-change devices. Our colloidal approach for phase-change applications offers higher customizability of materials, simpler fabrication, and further miniaturization to the sub-10 nm phase-change devices.
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Affiliation(s)
- Dhananjeya Kumaar
- Chemistry
and Materials Design, Institute for Electronics, Department of Information
Technology and Electrical Engineering, ETH
Zürich, 8092 Zürich, Switzerland
| | - Matthias Can
- Chemistry
and Materials Design, Institute for Electronics, Department of Information
Technology and Electrical Engineering, ETH
Zürich, 8092 Zürich, Switzerland
| | - Kevin Portner
- Integrated
Systems Laboratory, Department of Information Technology and Electrical
Engineering, ETH Zürich, 8092 Zürich, Switzerland
| | - Helena Weigand
- Optical
Nanomaterial Group, Institute for Quantum Electronics, Department
of Physics, ETH Zürich, 8093 Zürich, Switzerland
| | - Olesya Yarema
- Materials
and Device Engineering, Institute for Electronics, Department of Information
Technology and Electrical Engineering, ETH
Zürich, 8092 Zürich, Switzerland
| | - Simon Wintersteller
- Chemistry
and Materials Design, Institute for Electronics, Department of Information
Technology and Electrical Engineering, ETH
Zürich, 8092 Zürich, Switzerland
| | - Florian Schenk
- Chemistry
and Materials Design, Institute for Electronics, Department of Information
Technology and Electrical Engineering, ETH
Zürich, 8092 Zürich, Switzerland
| | - Darijan Boskovic
- Chemistry
and Materials Design, Institute for Electronics, Department of Information
Technology and Electrical Engineering, ETH
Zürich, 8092 Zürich, Switzerland
| | - Nathan Pharizat
- Chemistry
and Materials Design, Institute for Electronics, Department of Information
Technology and Electrical Engineering, ETH
Zürich, 8092 Zürich, Switzerland
| | - Robin Meinert
- Integrated
Systems Laboratory, Department of Information Technology and Electrical
Engineering, ETH Zürich, 8092 Zürich, Switzerland
| | - Evgeniia Gilshtein
- Laboratory
for Thin Films and Photovoltaics, Empa −
Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
| | - Yaroslav Romanyuk
- Laboratory
for Thin Films and Photovoltaics, Empa −
Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
| | - Artemios Karvounis
- Optical
Nanomaterial Group, Institute for Quantum Electronics, Department
of Physics, ETH Zürich, 8093 Zürich, Switzerland
| | - Rachel Grange
- Optical
Nanomaterial Group, Institute for Quantum Electronics, Department
of Physics, ETH Zürich, 8093 Zürich, Switzerland
| | - Alexandros Emboras
- Integrated
Systems Laboratory, Department of Information Technology and Electrical
Engineering, ETH Zürich, 8092 Zürich, Switzerland
| | - Vanessa Wood
- Materials
and Device Engineering, Institute for Electronics, Department of Information
Technology and Electrical Engineering, ETH
Zürich, 8092 Zürich, Switzerland
| | - Maksym Yarema
- Chemistry
and Materials Design, Institute for Electronics, Department of Information
Technology and Electrical Engineering, ETH
Zürich, 8092 Zürich, Switzerland
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4
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Parajuli P, Bhattacharya S, Rao R, Rao AM. Phonon anharmonicity in binary chalcogenides for efficient energy harvesting. MATERIALS HORIZONS 2022; 9:1602-1622. [PMID: 35467689 DOI: 10.1039/d1mh01601f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Thermoelectric (TE) materials have received much attention due to their ability to harvest waste heat energy. TE materials must exhibit a low thermal conductivity (κ) and a high power factor (PF) for efficient conversion. Both factors define the figure of merit (ZT) of the TE material, which can be increased by suppressing κ without degrading the PF. Recently, binary chalcogenides such as SnSe, GeTe, and PbTe have emerged as attractive candidates for thermoelectric energy generation at moderately high temperatures. These materials possess simple crystal structures with low κ in their pristine forms, which can be further lowered through doping and other approaches. Here, we review the recent advances in the temperature-dependent behavior of phonons and their influence on the thermal transport properties of chalcogenide-based TE materials. Because phonon anharmonicity is one of the fundamental contributing factors for low thermal conductivity in SnSe, Sb-doped GeTe, and related chalcogenides, we discuss complementary experimental approaches such as temperature-dependent Raman spectroscopy, inelastic neutron scattering, and calorimetry to measure anharmonicity. We further show how data gathered using multiple techniques helps us understand and engineer better TE materials. Finally, we discuss the rise of machine learning-aided efforts to discover, design, and synthesize TE materials of the future.
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Affiliation(s)
- P Parajuli
- Clemson Nanomaterials Institute, and Department of Physics and Astronomy, Clemson University, Clemson, SC 29634, USA.
| | - S Bhattacharya
- Clemson Nanomaterials Institute, and Department of Physics and Astronomy, Clemson University, Clemson, SC 29634, USA.
| | - R Rao
- Air Force Research Laboratory, WPAFB, Ohio 45433, USA
| | - A M Rao
- Clemson Nanomaterials Institute, and Department of Physics and Astronomy, Clemson University, Clemson, SC 29634, USA.
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5
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Kerres P, Zhou Y, Vaishnav H, Raghuwanshi M, Wang J, Häser M, Pohlmann M, Cheng Y, Schön CF, Jansen T, Bellin C, Bürgler DE, Jalil AR, Ringkamp C, Kowalczyk H, Schneider CM, Shukla A, Wuttig M. Scaling and Confinement in Ultrathin Chalcogenide Films as Exemplified by GeTe. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2201753. [PMID: 35491494 DOI: 10.1002/smll.202201753] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2022] [Indexed: 06/14/2023]
Abstract
Chalcogenides such as GeTe, PbTe, Sb2 Te3 , and Bi2 Se3 are characterized by an unconventional combination of properties enabling a plethora of applications ranging from thermo-electrics to phase change materials, topological insulators, and photonic switches. Chalcogenides possess pronounced optical absorption, relatively low effective masses, reasonably high electron mobilities, soft bonds, large bond polarizabilities, and low thermal conductivities. These remarkable characteristics are linked to an unconventional bonding mechanism characterized by a competition between electron delocalization and electron localization. Confinement, that is, the reduction of the sample dimension as realized in thin films should alter this competition and modify chemical bonds and the resulting properties. Here, pronounced changes of optical and vibrational properties are demonstrated for crystalline films of GeTe, while amorphous films of GeTe show no similar thickness dependence. For crystalline films, this thickness dependence persists up to remarkably large thicknesses above 15 nm. X-ray diffraction and accompanying simulations employing density functional theory relate these changes to thickness dependent structural (Peierls) distortions, due to an increased electron localization between adjacent atoms upon reducing the film thickness. A thickness dependence and hence potential to modify film properties for all chalcogenide films with a similar bonding mechanism is expected.
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Affiliation(s)
- Peter Kerres
- I. Institute of Physics (IA), RWTH Aachen University, 52056, Aachen, Germany
| | - Yiming Zhou
- I. Institute of Physics (IA), RWTH Aachen University, 52056, Aachen, Germany
| | - Hetal Vaishnav
- I. Institute of Physics (IA), RWTH Aachen University, 52056, Aachen, Germany
- Peter Grünberg Institute-JARA-Institute Energy-Efficient Information Technology (PGI-10), Forschungszentrum Jülich GmbH, 52428, Jülich, Germany
| | - Mohit Raghuwanshi
- I. Institute of Physics (IA), RWTH Aachen University, 52056, Aachen, Germany
- Peter Grünberg Institute-JARA-Institute Energy-Efficient Information Technology (PGI-10), Forschungszentrum Jülich GmbH, 52428, Jülich, Germany
| | - Jiangjing Wang
- I. Institute of Physics (IA), RWTH Aachen University, 52056, Aachen, Germany
- Center for Alloy Innovation and Design, Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an, 710049, China
| | - Maria Häser
- I. Institute of Physics (IA), RWTH Aachen University, 52056, Aachen, Germany
| | - Marc Pohlmann
- I. Institute of Physics (IA), RWTH Aachen University, 52056, Aachen, Germany
| | - Yudong Cheng
- I. Institute of Physics (IA), RWTH Aachen University, 52056, Aachen, Germany
- Center for Alloy Innovation and Design, Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an, 710049, China
| | | | - Thomas Jansen
- Peter Grünberg Institute-Electronic Properties (PGI-6), Forschungszentrum Jülich GmbH, 52428, Jülich, Germany
| | - Christophe Bellin
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne Université, UMR CNRS 7590, MNHN, Paris, F-75005, France
| | - Daniel E Bürgler
- Peter Grünberg Institute-Electronic Properties (PGI-6), Forschungszentrum Jülich GmbH, 52428, Jülich, Germany
| | - Abdur Rehman Jalil
- Peter Grünberg Institute-Semiconductor Nanoelectronics (PGI-6), Forschungszentrum Jülich GmbH, 52428, Jülich, Germany
| | - Christoph Ringkamp
- Peter Grünberg Institute-Semiconductor Nanoelectronics (PGI-6), Forschungszentrum Jülich GmbH, 52428, Jülich, Germany
| | - Hugo Kowalczyk
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne Université, UMR CNRS 7590, MNHN, Paris, F-75005, France
| | - Claus M Schneider
- Peter Grünberg Institute-Electronic Properties (PGI-6), Forschungszentrum Jülich GmbH, 52428, Jülich, Germany
- JARA-FIT, RWTH Aachen University, 52056, Aachen, Germany
| | - Abhay Shukla
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne Université, UMR CNRS 7590, MNHN, Paris, F-75005, France
| | - Matthias Wuttig
- Peter Grünberg Institute-JARA-Institute Energy-Efficient Information Technology (PGI-10), Forschungszentrum Jülich GmbH, 52428, Jülich, Germany
- JARA-FIT, RWTH Aachen University, 52056, Aachen, Germany
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6
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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: 34] [Impact Index Per Article: 11.3] [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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7
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Yang X, Li XM, Li Y, Li Y, Sun R, Liu JN, Bai X, Li N, Xie ZK, Su L, Gong ZZ, Zhang XQ, He W, Cheng Z. Three-Dimensional Limit of Bulk Rashba Effect in Ferroelectric Semiconductor GeTe. NANO LETTERS 2021; 21:77-83. [PMID: 33263408 DOI: 10.1021/acs.nanolett.0c03161] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Ferroelectric Rashba semiconductors (FERSCs) have recently attracted intensive attention due to their giant bulk Rashba parameter, αR, which results in a locking between the spin degrees of freedom and the switchable electric polarization. However, the integration of FERSCs into microelectronic devices has provoked questions concerning whether the Rashba effect can persist when the material thickness is reduced to several nanometers. Here we find that αR can keep a large value of 2.12 eV Å in the 5.0 nm thick GeTe film. The behavior of αR with thickness can be expressed by the scaling law and provides a 3D thickness limit of the bulk Rashba effect, dc = 2.1 ± 0.5 nm. Finally, we find that the thickness can modify the Berry curvature as well, which influences the polarization and consequently alters the αR. Our results give insight into understanding the factors influencing αR in FERSCs and pave a novel route for designing Rashba-type quantum materials.
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Affiliation(s)
- Xu Yang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiao-Mei Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yang Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yan Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Rui Sun
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jia-Nan Liu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xuedong Bai
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - Na Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zong-Kai Xie
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Lei Su
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zi-Zhao Gong
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiang-Qun Zhang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Wei He
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Zhaohua Cheng
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
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8
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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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9
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Zhang X, Zhao F, Wang Y, Liang X, Zhang Z, Feng Y, Li Y, Tang L, Feng W. Two-Dimensional GeTe: Air Stability and Photocatalytic Performance for Hydrogen Evolution. ACS APPLIED MATERIALS & INTERFACES 2020; 12:37108-37115. [PMID: 32643918 DOI: 10.1021/acsami.0c08699] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
As a key method to convert solar into chemical energy, photocatalytic water decomposition has garnered attention. Moreover, the development of graphene and graphene-like two-dimensional (2D) materials has brought fresh vitality in the field of photocatalysis. Here, we prepared two to four layers of GeTe nanosheets by ultrasonic-assisted liquid-phase exfoliation in argon and air, which we referred to as Ar-GeTe and O-GeTe, respectively. The photocatalytic hydrogen production potential of 2D GeTe was experimentally investigated for the first time. The results indicated that minimally layered GeTe samples are indirect-gap semiconductors with the GeTe band gap increasing after oxidation. All samples have suitable band positions that can drive photocatalytic water splitting into H2 under mild conditions, providing maximum hydrogen evolution rates of 1.13 mmol g-1 h-1 (Ar-GeTe) and 0.54 mmol g-1 h-1 (O-GeTe). With density functional theory computations, the structural stability of GeTe in air was discussed, revealing that oxygen atoms could easily combine with Ge to form a more stable structure, thus impacting the photocatalytic performance of 2D GeTe. Therefore, the light requirement and oxygen deficiency of the material give an advantage in the field of energy supply in space.
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Affiliation(s)
- Xin Zhang
- Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science and Engineering, Tianjin University, Tianjin 300072, P. R. China
| | - Fulai Zhao
- Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science and Engineering, Tianjin University, Tianjin 300072, P. R. China
| | - Yu Wang
- Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science and Engineering, Tianjin University, Tianjin 300072, P. R. China
| | - Xuejing Liang
- Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science and Engineering, Tianjin University, Tianjin 300072, P. R. China
| | - Zhixing Zhang
- Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science and Engineering, Tianjin University, Tianjin 300072, P. R. China
| | - Yiyu Feng
- Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science and Engineering, Tianjin University, Tianjin 300072, P. R. China
- Key Laboratory of Advanced Ceramics and Machining Technology, Ministry of Education, Tianjin 300072, P. R. China
- Key Laboratory of Materials Processing and Mold, Ministry of Education, Zhengzhou University, Zhengzhou 450002, China
| | - Yu Li
- Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science and Engineering, Tianjin University, Tianjin 300072, P. R. China
- Key Laboratory of Advanced Ceramics and Machining Technology, Ministry of Education, Tianjin 300072, P. R. China
| | - Lin Tang
- Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science and Engineering, Tianjin University, Tianjin 300072, P. R. China
- Key Laboratory of Advanced Ceramics and Machining Technology, Ministry of Education, Tianjin 300072, P. R. China
| | - Wei Feng
- Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science and Engineering, Tianjin University, Tianjin 300072, P. R. China
- Key Laboratory of Advanced Ceramics and Machining Technology, Ministry of Education, Tianjin 300072, P. R. China
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10
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Song S, Lo CWT, Aminzare M, Tseng YC, Valiyaveettil SM, Mozharivskyj Y. Enhancing the thermoelectric performance of Sn 0.5Ge 0.5Te via doping with Sb/Bi and alloying with Cu 2Te: Optimization of transport properties and thermal conductivities. Dalton Trans 2020; 49:6135-6144. [PMID: 32328598 DOI: 10.1039/d0dt00544d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The current work provides a comparative study of the thermoelectric properties of the Sn0.5Ge0.5Te phases doped with Sb and Bi and alloyed with Cu2Te. The Sn0.5Ge0.5Te composition was chosen based on the fact that it delivers the highest ZT value within the Sn1-xGexTe series (x≤ 0.5). Doping Sn0.5Ge0.5Te with electron-richer Sb and Bi improves both the charge transport properties and thermal conductivities. Alloying with Cu2Te optimizes the thermoelectric performance of the samples even further, yielding a ZT value of 0.99 for (Sn0.5Ge0.5)0.91Bi0.06Te(Cu2Te)0.05 at 500 °C. Hall measurements were performed to understand the effects of doping and alloying.
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Affiliation(s)
- Shaochang Song
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario, Canada.
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11
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Pawbake A, Bellin C, Paulatto L, Béneut K, Biscaras J, Narayana C, Late DJ, Shukla A. Pressure-Induced Phase Transitions in Germanium Telluride: Raman Signatures of Anharmonicity and Oxidation. PHYSICAL REVIEW LETTERS 2019; 122:145701. [PMID: 31050486 DOI: 10.1103/physrevlett.122.145701] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 03/15/2019] [Indexed: 06/09/2023]
Abstract
Pressure-induced phase transitions in GeTe, a prototype phase change material, have been studied to date with diffraction which is not sensitive to anharmonicity-induced dynamical effects. GeTe is also prone to surface oxidation which may compromise surface sensitive measurements. These factors could be responsible for the lack of clarity about the phases and transitions intervening in the phase diagram of GeTe. We have used high-pressure Raman scattering and ab initio pseudopotential density functional calculations to unambiguously establish the high-pressure phase diagram and identify three phases up to 57 GPa, a low-pressure rhombohedral phase, an intermediate pressure cubic phase, and a high-pressure orthorhombic phase. We detect substantial broadening and softening of Raman modes at low pressure and identify the transition regions and possible intermediate phases.
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Affiliation(s)
- Amit Pawbake
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne Université, UMR CNRS 7590, MNHN, IRD UMR 206, 4 Place Jussieu, F-75005 Paris, France
| | - Christophe Bellin
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne Université, UMR CNRS 7590, MNHN, IRD UMR 206, 4 Place Jussieu, F-75005 Paris, France
| | - Lorenzo Paulatto
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne Université, UMR CNRS 7590, MNHN, IRD UMR 206, 4 Place Jussieu, F-75005 Paris, France
| | - Keevin Béneut
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne Université, UMR CNRS 7590, MNHN, IRD UMR 206, 4 Place Jussieu, F-75005 Paris, France
| | - Johan Biscaras
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne Université, UMR CNRS 7590, MNHN, IRD UMR 206, 4 Place Jussieu, F-75005 Paris, France
| | - Chandrabhas Narayana
- Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560 064, India
| | - Dattatray J Late
- Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411008, India
| | - Abhay Shukla
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne Université, UMR CNRS 7590, MNHN, IRD UMR 206, 4 Place Jussieu, F-75005 Paris, France
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12
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Wei Y, Nukala P, Salverda M, Matzen S, Zhao HJ, Momand J, Everhardt AS, Agnus G, Blake GR, Lecoeur P, Kooi BJ, Íñiguez J, Dkhil B, Noheda B. A rhombohedral ferroelectric phase in epitaxially strained Hf 0.5Zr 0.5O 2 thin films. NATURE MATERIALS 2018; 17:1095-1100. [PMID: 30349031 DOI: 10.1038/s41563-018-0196-0] [Citation(s) in RCA: 93] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 09/14/2018] [Indexed: 06/08/2023]
Abstract
Hafnia-based thin films are a favoured candidate for the integration of robust ferroelectricity at the nanoscale into next-generation memory and logic devices. This is because their ferroelectric polarization becomes more robust as the size is reduced, exposing a type of ferroelectricity whose mechanism still remains to be understood. Thin films with increased crystal quality are therefore needed. We report the epitaxial growth of Hf0.5Zr0.5O2 thin films on (001)-oriented La0.7Sr0.3MnO3/SrTiO3 substrates. The films, which are under epitaxial compressive strain and predominantly (111)-oriented, display large ferroelectric polarization values up to 34 μC cm-2 and do not need wake-up cycling. Structural characterization reveals a rhombohedral phase, different from the commonly reported polar orthorhombic phase. This finding, in conjunction with density functional theory calculations, allows us to propose a compelling model for the formation of the ferroelectric phase. In addition, these results point towards thin films of simple oxides as a vastly unexplored class of nanoscale ferroelectrics.
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Affiliation(s)
- Yingfen Wei
- Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
| | - Pavan Nukala
- Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
- Laboratoire Structures, Propriétés et Modélisation des Solides, CentraleSupélec, CNRS-UMR8580, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Mart Salverda
- Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
| | - Sylvia Matzen
- Center for Nanoscience and Nanotechnology, CNRS-UMR 9001, Université Paris-Saclay, Palaiseau, France
| | - Hong Jian Zhao
- Materials Research and Technology Department, Luxembourg Institute of Science and Technology (LIST), Esch/Alzette, Luxembourg
| | - Jamo Momand
- Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
| | - Arnoud S Everhardt
- Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
| | - Guillaume Agnus
- Center for Nanoscience and Nanotechnology, CNRS-UMR 9001, Université Paris-Saclay, Palaiseau, France
| | - Graeme R Blake
- Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
| | - Philippe Lecoeur
- Center for Nanoscience and Nanotechnology, CNRS-UMR 9001, Université Paris-Saclay, Palaiseau, France
| | - Bart J Kooi
- Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands
| | - Jorge Íñiguez
- Materials Research and Technology Department, Luxembourg Institute of Science and Technology (LIST), Esch/Alzette, Luxembourg
| | - Brahim Dkhil
- Laboratoire Structures, Propriétés et Modélisation des Solides, CentraleSupélec, CNRS-UMR8580, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Beatriz Noheda
- Zernike Institute for Advanced Materials, University of Groningen, Groningen, the Netherlands.
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13
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Zhang P, Zhao F, Long P, Wang Y, Yue Y, Liu X, Feng Y, Li R, Hu W, Li Y, Feng W. Sonication-assisted liquid-phase exfoliated α-GeTe: a two-dimensional material with high Fe 3+ sensitivity. NANOSCALE 2018; 10:15989-15997. [PMID: 29856449 DOI: 10.1039/c8nr03091j] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We describe sonication-assisted liquid-phase exfoliation of rhombohedral germanium telluride (α-GeTe) to obtain a good dispersion of α-GeTe nanosheets in ethanol. The thickness of the α-GeTe nanosheets is dependent on the exfoliation conditions, and few-layer α-GeTe nanosheets of 2-4 layers and even monolayer α-GeTe were obtained. We use first-principles calculations to investigate the structural, electronic, and optical properties of monolayer and bulk α-GeTe and compare the optical band gap of centrifugally fractionated α-GeTe nanosheet dispersions with the computational predictions. We demonstrate that few layer α-GeTe nanosheets are purified selectively through centrifugation, and they exhibit high sensitivity to Fe3+. The scalable production of two-dimensional α-GeTe nanosheets can be used in the future optoelectronic industry.
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Affiliation(s)
- Panpan Zhang
- School of Materials Science and Engineering, Tianjin University, Tianjin 300072, P. R. China.
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14
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Chen B, de Wal D, ten Brink GH, Palasantzas G, Kooi BJ. Resolving Crystallization Kinetics of GeTe Phase-Change Nanoparticles by Ultrafast Calorimetry. CRYSTAL GROWTH & DESIGN 2018; 18:1041-1046. [PMID: 29445317 PMCID: PMC5806086 DOI: 10.1021/acs.cgd.7b01498] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Indexed: 06/01/2023]
Abstract
Chalcogenide-based phase change materials (PCMs) are promising candidates for the active element in novel electrical nonvolatile memories and have been applied successfully in rewritable optical disks. Nanostructured PCMs are considered as the next generation building blocks for their low power consumption, high storage density, and fast switching speed. Yet their crystallization kinetics at high temperature, the rate-limiting property upon switching, faces great challenges due to the short time and length scales involved. Here we present a facile method to synthesize highly controlled, ligand-free GeTe nanoparticles, an important PCM, with an average diameter under 10 nm. Subsequent crystallization by slow and ultrafast rates allows unravelling of the crystallization kinetics, demonstrating the breakdown of Arrhenius behavior for the crystallization rate and a fragile-to-strong transition in the viscosity as well as the overall crystal growth rate for the as-deposited GeTe nanoparticles. The obtained results pave the way for further development of phase-change memory based on GeTe with sub-lithographic sizes.
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Affiliation(s)
- Bin Chen
- Zernike Institute for Advanced
Materials,
Univerisity of Grnoingen, Nijenborgh 4, 9747
AG, Groningen, The Netherlands
| | - Dennis de Wal
- Zernike Institute for Advanced
Materials,
Univerisity of Grnoingen, Nijenborgh 4, 9747
AG, Groningen, The Netherlands
| | - Gert H. ten Brink
- Zernike Institute for Advanced
Materials,
Univerisity of Grnoingen, Nijenborgh 4, 9747
AG, Groningen, The Netherlands
| | - George Palasantzas
- Zernike Institute for Advanced
Materials,
Univerisity of Grnoingen, Nijenborgh 4, 9747
AG, Groningen, The Netherlands
| | - Bart J. Kooi
- Zernike Institute for Advanced
Materials,
Univerisity of Grnoingen, Nijenborgh 4, 9747
AG, Groningen, The Netherlands
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15
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Inverting polar domains via electrical pulsing in metallic germanium telluride. Nat Commun 2017; 8:15033. [PMID: 28401949 PMCID: PMC5394341 DOI: 10.1038/ncomms15033] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 02/22/2017] [Indexed: 01/29/2023] Open
Abstract
Germanium telluride (GeTe) is both polar and metallic, an unusual combination of properties in any material system. The large concentration of free-carriers in GeTe precludes the coupling of external electric field with internal polarization, rendering it ineffective for conventional ferroelectric applications and polarization switching. Here we investigate alternate ways of coupling the polar domains in GeTe to external electrical stimuli through optical second harmonic generation polarimetry and in situ TEM electrical testing on single-crystalline GeTe nanowires. We show that anti-phase boundaries, created from current pulses (heat shocks), invert the polarization of selective domains resulting in reorganization of certain 71o domain boundaries into 109o boundaries. These boundaries subsequently interact and evolve with the partial dislocations, which migrate from domain to domain with the carrier-wind force (electrical current). This work suggests that current pulses and carrier-wind force could be external stimuli for domain engineering in ferroelectrics with significant current leakage. Polar metals such as GeTe could store information using electric domains but the high conductivity screens electric fields, preventing the use of usual domain control techniques. Here, the authors demonstrate that polar domains in GeTe can be manipulated using electrically generated heat shocks.
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16
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Boschker JE, Wang R, Calarco R. GeTe: a simple compound blessed with a plethora of properties. CrystEngComm 2017. [DOI: 10.1039/c7ce01040k] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
A selection from the wide range of functional properties present in the binary compound, GeTe, are reviewed is this paper.
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Affiliation(s)
- Jos E. Boschker
- Paul-Drude-Institut für Festkörperelektronik
- 10117 Berlin
- Germany
| | - Ruining Wang
- Paul-Drude-Institut für Festkörperelektronik
- 10117 Berlin
- Germany
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17
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Chen B, Ten Brink GH, Palasantzas G, Kooi BJ. Size-dependent and tunable crystallization of GeSbTe phase-change nanoparticles. Sci Rep 2016; 6:39546. [PMID: 27996054 PMCID: PMC5172365 DOI: 10.1038/srep39546] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 11/24/2016] [Indexed: 11/09/2022] Open
Abstract
Chalcogenide-based nanostructured phase-change materials (PCMs) are considered promising building blocks for non-volatile memory due to their high write and read speeds, high data-storage density, and low power consumption. Top-down fabrication of PCM nanoparticles (NPs), however, often results in damage and deterioration of their useful properties. Gas-phase condensation based on magnetron sputtering offers an attractive and straightforward solution to continuously down-scale the PCMs into sub-lithographic sizes. Here we unprecedentedly present the size dependence of crystallization for Ge2Sb2Te5 (GST) NPs, whose production is currently highly challenging for chemical synthesis or top-down fabrication. Both amorphous and crystalline NPs have been produced with excellent size and composition control with average diameters varying between 8 and 17 nm. The size-dependent crystallization of these NPs was carefully analyzed through in-situ heating in a transmission electron microscope, where the crystallization temperatures (Tc) decrease when the NPs become smaller. Moreover, methane incorporation has been observed as an effective method to enhance the amorphous phase stability of the NPs. This work therefore elucidates that GST NPs synthesized by gas-phase condensation with tailored properties are promising alternatives in designing phase-change memories constrained by optical lithography limitations.
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Affiliation(s)
- Bin Chen
- Zernike Institute for Advanced Materials University of Groningen, Nijenborgh 4, 9747AG Groningen, the Netherlands
| | - Gert H Ten Brink
- Zernike Institute for Advanced Materials University of Groningen, Nijenborgh 4, 9747AG Groningen, the Netherlands
| | - George Palasantzas
- Zernike Institute for Advanced Materials University of Groningen, Nijenborgh 4, 9747AG Groningen, the Netherlands
| | - Bart J Kooi
- Zernike Institute for Advanced Materials University of Groningen, Nijenborgh 4, 9747AG Groningen, the Netherlands
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18
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Ordered Peierls distortion prevented at growth onset of GeTe ultra-thin films. Sci Rep 2016; 6:32895. [PMID: 27612303 PMCID: PMC5017194 DOI: 10.1038/srep32895] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 08/03/2016] [Indexed: 11/26/2022] Open
Abstract
Using reflection high-energy electron diffraction (RHEED), the growth onset of molecular beam epitaxy (MBE) deposited germanium telluride (GeTe) film on Si(111)-(√3 × √3)R30°-Sb surfaces is investigated, and a larger than expected in-plane lattice spacing is observed during the deposition of the first two molecular layers. High-resolution transmission electron microscopy (HRTEM) confirms that the growth proceeds via closed layers, and that those are stable after growth. The comparison of the experimental Raman spectra with theoretical calculated ones allows assessing the shift of the phonon modes for a quasi-free-standing ultra-thin GeTe layer with larger in-plane lattice spacing. The manifestation of the latter phenomenon is ascribed to the influence of the interface and the confinement of GeTe within the limited volume of material available at growth onset, either preventing the occurrence of Peierls dimerization or their ordered arrangement to occur normally.
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19
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Jha CK, Karwasara S, Nagendran S. Can low-valent germanium chemistry be practiced under ambient conditions? A tale of a water-stable yet reactive germylene monochloride complex. Chemistry 2014; 20:10240-4. [PMID: 25044284 DOI: 10.1002/chem.201403598] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Indexed: 11/07/2022]
Abstract
A germylene monochloride complex ((DPM)GeCl, 1) that is water stable was isolated for the first time. Interestingly, it reacts with cesium fluoride under ambient conditions (non-inert atmosphere and water-containing solvent) to afford water stable germylene monofluoride complex ((DPM)GeF, 2). Due to the usage of DPM (dipyrrinate) ligand, germylene monohalides 1 and 2 show fluorescence in the visible region at 555 and 538 nm, respectively. Compounds 1 and 2 are the first fluorescent germylene complexes and were characterized by multinuclear NMR spectroscopy. The structure of compound 1 was also proved by single crystal X-ray diffraction studies.
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Affiliation(s)
- Chandan Kumar Jha
- Department of Chemistry, Indian Institute of Technology Delhi (IIT Delhi), Hauz Khas, New Delhi, 110016 (India)
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20
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Szwarcman D, Prosandeev S, Louis L, Berger S, Rosenberg Y, Lereah Y, Bellaiche L, Markovich G. The stabilization of a single domain in free-standing ferroelectric nanocrystals. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:122202. [PMID: 24594615 DOI: 10.1088/0953-8984/26/12/122202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
High resolution electron microscopy, electron diffraction and electron holography were used to study individual free-standing ∼ 30 nm barium titanate nanocrystals. Large unidirectional variations in the tetragonal distortion were mapped across the smaller nanocrystals, peaking to anomalously large values of up to 4% at the centers of the nanocrystals. This indicated that the nanocrystals consist of highly strained single ferroelectric domains. Simulations using an effective Hamiltonian for modeling a nanocrystal under a small depolarizing field and negative pressure qualitatively confirm this picture. These simulations, along with the development of a phenomenological model, show that the tetragonal distortion variation is a combined effect of: (i) electrostrictive coupling between the spontaneous polarization and strain inside the nanocrystal, and (ii) a surface-induced effective stress existing inside the nanodot. As a result, a 'strain skin layer', having a smaller tetragonal distortion relative to the core of the nanocrystal, is created.
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Affiliation(s)
- Daniel Szwarcman
- Department of Chemical Physics, School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv 69978, Israel
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21
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Li L, Gan Z, McCartney MR, Liang H, Yu H, Yin WJ, Yan Y, Gao Y, Wang J, Smith DJ. Determination of polarization-fields across polytype interfaces in InAs nanopillars. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2014; 26:1052-1057. [PMID: 24535970 DOI: 10.1002/adma.201304021] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Revised: 09/14/2013] [Indexed: 06/03/2023]
Abstract
Polarization fields within InAs nanopillars with zincblende(ZB)/wurtzite(WZ) polytype stacking are quantified. The displacement of charged ions inside individual tetrahedra of WZ regions is measured at the atomic scale. The variations of spontaneous polarization along the interface normal are related to strain at interfaces of different polytypes. Thus, direct correlation between local atomic structure and electric properties is demonstrated.
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Affiliation(s)
- Luying Li
- Center for Nanoscale Characterization and Devices, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, China; Department of Physics, Arizona State University, Tempe, Arizona, 85287-1504, USA
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22
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Przybylińska H, Springholz G, Lechner RT, Hassan M, Wegscheider M, Jantsch W, Bauer G. Magnetic-field-induced ferroelectric polarization reversal in the multiferroic Ge(1-x)Mn(x)Te semiconductor. PHYSICAL REVIEW LETTERS 2014; 112:047202. [PMID: 24580486 DOI: 10.1103/physrevlett.112.047202] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Revised: 11/14/2013] [Indexed: 06/03/2023]
Abstract
Ge(1-x)Mn(x)Te is shown to be a multiferroic semiconductor, exhibiting both ferromagnetic and ferroelectric properties. By ferromagnetic resonance we demonstrate that both types of order are coupled to each other. As a result, magnetic-field-induced ferroelectric polarization reversal is achieved. Switching of the spontaneous electric dipole moment is monitored by changes in the magnetocrystalline anisotropy. This also reveals that the ferroelectric polarization reversal is accompanied by a reorientation of the hard and easy magnetization axes. By tuning the GeMnTe composition, the interplay between ferromagnetism and ferroelectricity can be controlled.
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Affiliation(s)
- H Przybylińska
- Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
| | - G Springholz
- Institut für Halbleiter-und Festkörperphysik, Johannes Kepler Universität, A-4040 Linz, Austria
| | - R T Lechner
- Institut für Halbleiter-und Festkörperphysik, Johannes Kepler Universität, A-4040 Linz, Austria and Institut für Physik, Montanuniversität Leoben, A-8700 Leoben, Austria
| | - M Hassan
- Institut für Halbleiter-und Festkörperphysik, Johannes Kepler Universität, A-4040 Linz, Austria and Department of Physics, University of the Punjab, Lahore-54590, Pakistan
| | - M Wegscheider
- Institut für Halbleiter-und Festkörperphysik, Johannes Kepler Universität, A-4040 Linz, Austria
| | - W Jantsch
- Institut für Halbleiter-und Festkörperphysik, Johannes Kepler Universität, A-4040 Linz, Austria
| | - G Bauer
- Institut für Halbleiter-und Festkörperphysik, Johannes Kepler Universität, A-4040 Linz, Austria
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23
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Schulz S, Heimann S, Kaiser K, Prymak O, Assenmacher W, Brüggemann JT, Mallick B, Mudring AV. Solution-Based Synthesis of GeTe Octahedra at Low Temperature. Inorg Chem 2013; 52:14326-33. [DOI: 10.1021/ic402266j] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Stephan Schulz
- Institute
of Inorganic Chemistry and Center for Nanointegration Duisburg-Essen
(CENIDE), University of Duisburg-Essen, Universitätsstraße 5-7, D-45117 Essen, Germany
| | - Stefan Heimann
- Institute
of Inorganic Chemistry and Center for Nanointegration Duisburg-Essen
(CENIDE), University of Duisburg-Essen, Universitätsstraße 5-7, D-45117 Essen, Germany
| | - Kevin Kaiser
- Institute
of Inorganic Chemistry and Center for Nanointegration Duisburg-Essen
(CENIDE), University of Duisburg-Essen, Universitätsstraße 5-7, D-45117 Essen, Germany
| | - Oleg Prymak
- Institute
of Inorganic Chemistry and Center for Nanointegration Duisburg-Essen
(CENIDE), University of Duisburg-Essen, Universitätsstraße 5-7, D-45117 Essen, Germany
| | - Wilfried Assenmacher
- Institute
of Inorganic Chemistry, University of Bonn, Römerstraße 164, D-53117 Bonn, Germany
| | - Jörg Thomas Brüggemann
- Inorganic
Chemistry III−Materials Engineering and Characterization, Ruhr-University Bochum, 44780 Bochum, Germany
| | - Bert Mallick
- Inorganic
Chemistry III−Materials Engineering and Characterization, Ruhr-University Bochum, 44780 Bochum, Germany
| | - Anja-Verena Mudring
- Inorganic
Chemistry III−Materials Engineering and Characterization, Ruhr-University Bochum, 44780 Bochum, Germany
- Materials
Science and Engineering, Iowa State University, Ames, Iowa 50010, United States
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24
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Polking MJ, Jain PK, Bekenstein Y, Banin U, Millo O, Ramesh R, Alivisatos AP. Controlling localized surface plasmon resonances in GeTe nanoparticles using an amorphous-to-crystalline phase transition. PHYSICAL REVIEW LETTERS 2013; 111:037401. [PMID: 23909359 DOI: 10.1103/physrevlett.111.037401] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Indexed: 06/02/2023]
Abstract
Infrared absorption measurements of amorphous and crystalline nanoparticles of GeTe reveal a localized surface plasmon resonance (LSPR) mode in the crystalline phase that is absent in the amorphous phase. The LSPR mode emerges upon crystallization of amorphous nanoparticles. The contrasting plasmonic properties are elucidated with scanning tunneling spectroscopy measurements indicating a Burstein-Moss shift of the band gap in the crystalline phase and a finite density of electronic states throughout the band gap in the amorphous phase that limits the effective free carrier density.
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Affiliation(s)
- Mark J Polking
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
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25
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Xu L, Kim C, Shukla AK, Dong A, Mattox TM, Milliron DJ, Cabana J. Monodisperse Sn nanocrystals as a platform for the study of mechanical damage during electrochemical reactions with Li. NANO LETTERS 2013; 13:1800-5. [PMID: 23477483 DOI: 10.1021/nl400418c] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Monodisperse Sn spherical nanocrystals of 10.0 ± 0.2 nm were prepared in dispersible colloidal form. They were used as a model platform to study the impact of size on the accommodation of colossal volume changes during electrochemical lithiation using ex situ transmission electron microscopy (TEM). Significant mechanical damage was observed after full lithiation, indicating that even crystals at these very small dimensions are not sufficient to prevent particle pulverization that compromises electrode durability.
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Affiliation(s)
- Linping Xu
- Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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26
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Gerard C, Das R, Mahadevan P, Sarma DD. Effective Mass-Driven Structural Transition in a Mn-Doped ZnS Nanoplatelet. J Phys Chem Lett 2013; 4:1023-1027. [PMID: 26291371 DOI: 10.1021/jz4002746] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Mn doping in ZnS nanoplatelets has been shown to induce a structural transition from the wurtzite to the zinc blende phase. We trace the origin of this transition to quantum confinement effects, which shift the valence band maximum of the wurtzite and zinc blende polymorphs of ZnS at different rates as a function of the nanocrystal size, arising from different effective hole masses in the two structures. This modifies the covalency associated with Mn incorporation and is reflected in the size-dependent binding energy difference for the two structures.
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Affiliation(s)
- Celine Gerard
- †Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India
| | - Ruma Das
- ‡Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Center for Basic Sciences, JD Block, Sector III, Salt Lake, Kolkata-700098, India
| | - Priya Mahadevan
- ‡Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Center for Basic Sciences, JD Block, Sector III, Salt Lake, Kolkata-700098, India
| | - D D Sarma
- †Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India
- ∥Council of Scientific and Industrial Research-Network of Institutes for Solar Energy (CSIR-NISE), New-Delhi, India
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27
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Xiao G, Wang Y, Ning J, Wei Y, Liu B, Yu WW, Zou G, Zou B. Recent advances in IV–VI semiconductor nanocrystals: synthesis, mechanism, and applications. RSC Adv 2013. [DOI: 10.1039/c3ra23209c] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
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28
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Gao MR, Xu YF, Jiang J, Yu SH. Nanostructured metal chalcogenides: synthesis, modification, and applications in energy conversion and storage devices. Chem Soc Rev 2013; 42:2986-3017. [DOI: 10.1039/c2cs35310e] [Citation(s) in RCA: 1243] [Impact Index Per Article: 113.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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29
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Kim MH, Gupta G, Kim J. Facile solution routes for the syntheses of GeTe nanocrystals. RSC Adv 2013. [DOI: 10.1039/c2ra21790b] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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30
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Enriquez-Flores CI, Gervacio-Arciniega JJ, Cruz-Valeriano E, de Urquijo-Ventura P, Gutierrez-Salazar BJ, Espinoza-Beltran FJ. Fast frequency sweeping in resonance-tracking SPM for high-resolution AFAM and PFM imaging. NANOTECHNOLOGY 2012; 23:495705. [PMID: 23149480 DOI: 10.1088/0957-4484/23/49/495705] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
A new resonance-tracking (RT) method using fast frequency sweeping excitation was developed for quantitative scanning probe microscopy (SPM) imaging. This method allows quantitative imaging of elastic properties and ferroelectrical domains with nanoscale resolution at high data acquisition rates. It consists of a commercial AFM system combined with a high-frequency lock-in amplifier, a programmed function generator and a fast data acquisition card. The resonance-tracking method was applied to the atomic force acoustic microscopy (AFAM) and to the piezoresponse force microscopy (PFM) modes. Plots of amplitude versus time and phase versus time for resonant spectra working with different sweeping frequencies were obtained to evaluate the response speed of the lock-in amplifier. It was proved that this resonance-tracking method allows suitable spectral acquisition at a rate of about 5 ms/pixel, which is useful for SPM imaging in a practical scanning time. In order to demonstrate the system performance, images of RT-AFAM for TiN films and RT-PFM for GeTe are shown.
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Affiliation(s)
- C I Enriquez-Flores
- CINVESTAV Unidad Querétaro, Lib. Norponiente 2000, Real de Juriquilla, 76230 Querétaro, Qro., Mexico.
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31
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Xiao C, Qin X, Zhang J, An R, Xu J, Li K, Cao B, Yang J, Ye B, Xie Y. High thermoelectric and reversible p-n-p conduction type switching integrated in dimetal chalcogenide. J Am Chem Soc 2012; 134:18460-6. [PMID: 23066707 DOI: 10.1021/ja308936b] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The subject of the involved phase transition in solid materials has formed not only the basis of materials technology but also the central issue of solid-state chemistry for centuries. The ability to design and control the required changes in physical properties within phase transition becomes key prerequisite for the modern functionalized materials. Herein, we have experimentally achieved the high thermoelectric performance (ZT value reaches 1.5 at 700 K) and reversible p-n-p semiconducting switching integrated in a dimetal chalcogenide, AgBiSe(2) during the continuous hexagonal-rhombohedral-cubic phase transition. The clear-cut evidences in temperature-dependent positron annihilation and Raman spectra confirmed that the p-n-p switching is derived from the bimetal atoms exchange within phase transition, whereas the full disordering of bimetal atoms after the bimetal exchange results in the high thermoelectric performance. The combination of p-n-p switching and high thermoelectric performance enables the dimetal chalcogenides perfect candidates for novel multifunctional electronic devices. The discovery of bimetal atoms exchange during the phase transition brings novel phenomena with unusual properties which definitely enrich solid-state chemistry and materials science.
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Affiliation(s)
- Chong Xiao
- Division of Nanomaterials and Nanochemistry, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science & Technology of China, Hefei, Anhui, 230026, P. R. China
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32
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Caldwell MA, Jeyasingh RGD, Wong HSP, Milliron DJ. Nanoscale phase change memory materials. NANOSCALE 2012; 4:4382-92. [PMID: 22740071 DOI: 10.1039/c2nr30541k] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Phase change memory materials store information through their reversible transitions between crystalline and amorphous states. For typical metal chalcogenide compounds, their phase transition properties directly impact critical memory characteristics and the manipulation of these is a major focus in the field. Here, we discuss recent work that explores the tuning of such properties by scaling the materials to nanoscale dimensions, including fabrication and synthetic strategies used to produce nanoscale phase change memory materials. The trends that emerge are relevant to understanding how such memory technologies will function as they scale to ever smaller dimensions and also suggest new approaches to designing materials for phase change applications. Finally, the challenges and opportunities raised by integrating nanoscale phase change materials into switching devices are discussed.
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33
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Deng Z, Cao D, He J, Lin S, Lindsay SM, Liu Y. Solution synthesis of ultrathin single-crystalline SnS nanoribbons for photodetectors via phase transition and surface processing. ACS NANO 2012; 6:6197-6207. [PMID: 22738287 DOI: 10.1021/nn302504p] [Citation(s) in RCA: 100] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We report the solution-phase synthesis and surface processing of ~2-5 μm long single-crystalline IV-VI tin(II) sulfide (SnS) ultrathin nanoribbons, with thicknesses down to 10 nm, and their use in single nanoribbon based photodetectors. The SnS nanoribbons grow via a metastable-to-stable phase transition from zinc blende (ZB) nanospheres to orthorhombic nanoribbons; dual-phase intermediate heterostructures with zinc blende nanosphere heads and orthorhombic nanoribbon tails were observed. Exchange of long, insulating organic oleylamine ligands by short, inorganic HS(-) ligands converts the organic SnS nanoribbons into completely inorganic, hydrophilic structures. Field-effect transistor (FET) devices were made from single SnS nanoribbons, both before and after ligand exchange, which exhibit p-type semiconductor behavior. The SnS single nanoribbon based photodetector devices showed highly sensitive and rapid photocurrent responses to illumination by blue, green, and red light. The switching behavior of photocurrent generation and annihilation is complete within approximately 1 ms and exhibits high photoconductivity gains (up to 2.3 × 10(4)) and good stability. The ON/OFF ratio of the photodetector can be engineered to 80 (4 nA/50 pA) using a small drain current (10 mV) for the all inorganic SnS nanoribbons. This work paves the way for the colloidal growth of low-cost, environmentally benign, single-crystalline narrow band gap semiconductor nanostructures from abundant elements for applications in photodetectors and other nanoscale devices.
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Affiliation(s)
- Zhengtao Deng
- The Biodesign Institute, and Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287, United States.
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34
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Polking MJ, Han MG, Yourdkhani A, Petkov V, Kisielowski CF, Volkov VV, Zhu Y, Caruntu G, Alivisatos AP, Ramesh R. Ferroelectric order in individual nanometre-scale crystals. NATURE MATERIALS 2012; 11:700-709. [PMID: 22772655 DOI: 10.1038/nmat3371] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 05/29/2012] [Indexed: 05/29/2023]
Abstract
Ferroelectricity in finite-dimensional systems continues to arouse interest, motivated by predictions of vortex polarization states and the utility of ferroelectric nanomaterials in memory devices, actuators and other applications. Critical to these areas of research are the nanoscale polarization structure and scaling limit of ferroelectric order, which are determined here in individual nanocrystals comprising a single ferroelectric domain. Maps of ferroelectric structural distortions obtained from aberration-corrected transmission electron microscopy, combined with holographic polarization imaging, indicate the persistence of a linearly ordered and monodomain polarization state at nanometre dimensions. Room-temperature polarization switching is demonstrated down to ~5 nm dimensions. Ferroelectric coherence is facilitated in part by control of particle morphology, which along with electrostatic boundary conditions is found to determine the spatial extent of cooperative ferroelectric distortions. This work points the way to multi-Tbit/in(2) memories and provides a glimpse of the structural and electrical manifestations of ferroelectricity down to its ultimate limits.
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Affiliation(s)
- Mark J Polking
- Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, California 94720, USA
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35
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de la Mata M, Magen C, Gazquez J, Utama MIB, Heiss M, Lopatin S, Furtmayr F, Fernández-Rojas CJ, Peng B, Morante JR, Rurali R, Eickhoff M, Fontcuberta i Morral A, Xiong Q, Arbiol J. Polarity assignment in ZnTe, GaAs, ZnO, and GaN-AlN nanowires from direct dumbbell analysis. NANO LETTERS 2012; 12:2579-2586. [PMID: 22493937 DOI: 10.1021/nl300840q] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Aberration corrected scanning transmission electron microscopy (STEM) with high angle annular dark field (HAADF) imaging and the newly developed annular bright field (ABF) imaging are used to define a new guideline for the polarity determination of semiconductor nanowires (NWs) from binary compounds in two extreme cases: (i) when the dumbbell is formed with atoms of similar mass (GaAs) and (ii) in the case where one of the atoms is extremely light (N or O: ZnO and GaN/AlN). The theoretical fundaments of these procedures allow us to overcome the main challenge in the identification of dumbbell polarity. It resides in the separation and identification of the constituent atoms in the dumbbells. The proposed experimental via opens new routes for the fine characterization of nanostructures, e.g., in electronic and optoelectronic fields, where the polarity is crucial for the understanding of their physical properties (optical and electronic) as well as their growth mechanisms.
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Affiliation(s)
- Maria de la Mata
- Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, E-08193 Bellaterra, CAT, Spain
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36
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Peierls distortion mediated reversible phase transition in GeTe under pressure. Proc Natl Acad Sci U S A 2012; 109:5948-52. [PMID: 22474349 DOI: 10.1073/pnas.1202875109] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
With the advent of big synchrotron facilities around the world, pressure is now routinely placed to design a new material or manipulate the properties of materials. In GeTe, an important phase-change material that utilizes the property contrast between the crystalline and amorphous states for data storage, we observed a reversible phase transition of rhombohedral ↔ rocksalt ↔ orthorhombic ↔ monoclinic coupled with a semiconductor ↔ metal interconversion under pressure on the basis of ab initio molecular dynamics simulations. This interesting reversible phase transition under pressure is believed to be mediated by Peierls distortion in GeTe. Our results suggest a unique way to understand the reversible phase transition and hence the resistance switching that is crucial to the applications of phase-change materials in nonvolatile memory. The present finding can also be expanded to other IV-VI semiconductors.
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37
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Saruyama M, So YG, Kimoto K, Taguchi S, Kanemitsu Y, Teranishi T. Spontaneous formation of wurzite-CdS/zinc blende-CdTe heterodimers through a partial anion exchange reaction. J Am Chem Soc 2011; 133:17598-601. [PMID: 21972931 DOI: 10.1021/ja2078224] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ion exchange of ionic semiconductor nanoparticles (NPs) is a facile method for the synthesis of type-II semiconductor heterostructured NPs with staggered alignment of band edges for photoelectric applications. Through consideration of the crystallographic orientation and strain at the heterointerface, well-designed heterostructures can be constructed through ion exchange reactions. Here we report the selective synthesis of anisotropically phase-segregated cadmium sulfide (CdS)/ cadmium telluride (CdTe) heterodimers via a novel anion exchange reaction of CdS NPs with an organic telluride precursor. The wurtzite-CdS/zinc blende-CdTe heterodimers in this study resulted from spontaneous phase segregation induced by the differences in the crystal structures of the two phases, accompanying a centrosymmetry breaking of the spherical CdS NPs. The CdS/CdTe heterodimers exhibited photoinduced spatial charge separation because of their staggered band-edge alignment.
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Affiliation(s)
- Masaki Saruyama
- Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennoidai, Tsukuba, Ibaraki 305-8571, Japan
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