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Chang YR, Nishimura T, Taniguchi T, Watanabe K, Nagashio K. Performance Enhancement of SnS/ h-BN Heterostructure p-Type FET via the Thermodynamically Predicted Surface Oxide Conversion Method. ACS APPLIED MATERIALS & INTERFACES 2022; 14:19928-19937. [PMID: 35442622 DOI: 10.1021/acsami.2c05534] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Searching for the counterpart of well-developed two-dimensional (2D) n-type field effect transistors (FETs) is indispensable for complementary logic circuit applications for 2D devices. Although SnS is regarded as a potential candidate for high-performance p-type FETs, recent experiments only show poor results deviating from the theoretically predicted high mobility. In this research, the serious performance degradation due to the surface oxidation of SnS, which commonly occurs in most 2D materials, is addressed through surface oxide conversion using highly reactive Ti. In this conversion process, which is confirmed by systematic characterization, the reduction of SnS surface oxide is accompanied by the formation of functional titanium oxide, which works as both a conductive intermediate layer to improve the contact property and a buffer layer of the high-k top gate insulator at the channel region. Consequently, a record-high field effect mobility of 87.4 cm2 V-1 s-1 in SnS p-type FETs is achieved. The surface oxide conversion method applied here is consistent with our previous thermodynamic prediction, and this novel technique can be widely introduced to all 2D materials that are vulnerable to oxidation and facilitate the future development of 2D devices.
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Affiliation(s)
- Yih-Ren Chang
- Department of Materials Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
| | - Tomonori Nishimura
- Department of Materials Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute of Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute of Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Kosuke Nagashio
- Department of Materials Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
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Chang YR, Nishimura T, Nagashio K. Thermodynamic Perspective on the Oxidation of Layered Materials and Surface Oxide Amelioration in 2D Devices. ACS APPLIED MATERIALS & INTERFACES 2021; 13:43282-43289. [PMID: 34478258 DOI: 10.1021/acsami.1c13279] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Surface oxidation is an unneglectable problem for 2D semiconductors because it hinders the practical application of 2D material-based devices. In this research, the oxidation of layered materials is investigated by a thermodynamic approach to verify their oxidation tendency. It was found that almost all 2D materials are thermodynamically unstable in the presence of oxygen at room temperature. Two potential solutions for surface oxidation are proposed in this work: (i) the conversion of the surface oxides to functional oxides through the deposition of active metals and (ii) the recovery of original 2D materials from the surface oxides by 2D material heterostructure formation with the same chalcogen group. Supported by thermodynamic calculations, both approaches are feasible to ameliorate the surface oxides of 2D materials by the appropriate selection of metals for deposition or 2D materials for heterostructure formation. Thermodynamic data of 64 elements and 75 2D materials are included and compared in this research, which can improve gate insulator or electrode contact material selection in 2D devices to solve the surface oxidation issue. For instance, yttrium and titanium are good candidates for surface oxide conversion, while zirconium and hafnium chalcogenide can trigger the recovery of original 2D materials from their surface oxides. The systematic diagrams presented in this work can serve as a guideline for considering surface oxidation in future device fabrication from various 2D materials.
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Affiliation(s)
- Yih-Ren Chang
- Department of Materials Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
| | - Tomonori Nishimura
- Department of Materials Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
| | - Kosuke Nagashio
- Department of Materials Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
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Luo X, Huang B, Guo X, Lu W, Zheng G, Huang B, Li J, Li P, Yang Y. High ZT Value of Pure SnSe Polycrystalline Materials Prepared by High-Energy Ball Milling plus Hot Pressing Sintering. ACS APPLIED MATERIALS & INTERFACES 2021; 13:43011-43021. [PMID: 34469095 DOI: 10.1021/acsami.1c09208] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The research of thermoelectric materials is of great significance to solve the energy crisis and environmental problems. In this work, a series of pure SnSe bulk crystals were prepared by melting, high-energy ball milling, and hot pressing processes. The results show that the ZT value of the prepared pure SnSe polycrystalline material is up to 2.1 at 873 K. On the one hand, due to the reduction of grain size and lattice distortion caused by long-time high-energy ball milling, the lattice thermal conductivity is significantly reduced, which is only 0.18 W K-1 m-1 at 873 K. On the other hand, high-energy ball milling leads to the increase of Sn vacancies, which improves the conductivity of SnSe polycrystalline materials. Since the whole process of ball milling was carried out in a closed ball milling tank filled with high-purity argon, no oxidation of the SnSe powder is also a guarantee to obtain pure SnSe polycrystalline materials with high ZT value.
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Affiliation(s)
- Xian Luo
- School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072, P. R. China
| | - Bowei Huang
- School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072, P. R. China
| | - Xiang Guo
- School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072, P. R. China
| | - Wenjie Lu
- School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072, P. R. China
| | - Guiyuan Zheng
- School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072, P. R. China
| | - Bin Huang
- School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072, P. R. China
| | - Jiankang Li
- Xi'an Aerospace New Material Co., Ltd., Xi'an 710065, P. R. China
| | - Pengtao Li
- School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072, P. R. China
| | - Yanqing Yang
- School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072, P. R. China
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Zhang B, Li A, Han G, Zhang Z, Peng K, Gong X, Zhou X, Han X. Dynamic Epitaxial Crystallization of SnSe 2 on the Oxidized SnSe Surface and Its Atomistic Mechanisms. ACS APPLIED MATERIALS & INTERFACES 2020; 12. [PMID: 32412229 DOI: 10.1021/acsami.0c05029] [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
Surface oxidation of SnSe sharply reduces its thermoelectric properties though the bulk single-crystalline materials of SnSe claim the record high zT values. Investigation on the oxidation behaviors of SnSe together with the subsequent phase transition and element migration is fundamentally important to maintaining the ultrahigh zT values, with a potential for further improvement. In this work, we disclose the dynamic epitaxial crystallization of SnSe2 on the amorphous surface of partially oxidized SnSe crystals and the corresponding atomistic mechanisms via transmission electron microscopy (TEM). It is revealed that the thermally annealed amorphous surface crystallized to SnO2 and SnSe2 in the outermost and secondary layers, respectively, forming distinctive SnSe/SnSe2/SnO2 multilayer heterostructures with specific orientation relationships between the two selenides. By means of in situ scanning TEM (STEM), the dynamic epitaxial crystallization process of SnSe2 was revealed when the oxidized SnSe surface was subjected to electron beam irradiation. Through the atomic-scale characterization and modeling analysis, we find that the exposed dangling Se diatoms on the SnSe surface serve as nucleation sites for lateral epitaxial crystallization of SnSe2. The same valence and similar coordination configuration of Se atoms in these two phases are supposed to facilitate the sharing of Se atoms, with lattice distortions in the SnSe2/SnSe interface. These findings are valuable for understanding the surface oxidation behavior of SnSe and revealing the interface structures of SnSe2/SnSe heterojunctions and also offering new routes for SnSe-related multilayer or heterostructure system design.
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Affiliation(s)
- Bin Zhang
- Analytical and Testing Center of Chongqing University, Chongqing 401331, P. R. China
| | - Ang Li
- Beijing Key Laboratory and Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124, P. R. China
| | - Guang Han
- College of Materials Science and Engineering, Chongqing University, Chongqing 400044, P. R. China
| | - Zhenhua Zhang
- Department of Materials and Environmental Engineering, Institute for Advanced Magnetic Materials, Hangzhou Dianzi University, Hangzhou 310018, P. R. China
| | - Kunling Peng
- Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, P. R. China
- College of Physics and Center for Quantum Materials and Devices, Institute of Advanced Interdisciplinary Studies, Chongqing University, Chongqing 401331, P. R. China
| | - Xiangnan Gong
- Analytical and Testing Center of Chongqing University, Chongqing 401331, P. R. China
| | - Xiaoyuan Zhou
- Analytical and Testing Center of Chongqing University, Chongqing 401331, P. R. China
- College of Physics and Center for Quantum Materials and Devices, Institute of Advanced Interdisciplinary Studies, Chongqing University, Chongqing 401331, P. R. China
| | - Xiaodong Han
- Beijing Key Laboratory and Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124, P. R. China
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Wei W, Chang C, Yang T, Liu J, Tang H, Zhang J, Li Y, Xu F, Zhang Z, Li JF, Tang G. Achieving High Thermoelectric Figure of Merit in Polycrystalline SnSe via Introducing Sn Vacancies. J Am Chem Soc 2017; 140:499-505. [PMID: 29243922 DOI: 10.1021/jacs.7b11875] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Thermoelectric power generation technology has emerged as a clean "heat engine" that can convert heat to electricity. Recently, the discovery of an ultrahigh thermoelectric figure of merit in SnSe crystals has drawn a great deal of attention. In view of their facile processing and scale-up applications, polycrystalline SnSe materials with ZT values comparable to those of the SnSe crystals are greatly desired. Here we achieve a record high ZT value ∼2.1 at 873 K in polycrystalline Sn1-xSe with Sn vacancies. We demonstrate that the carrier concentration increases by artificially introducing Sn vacancies, contributing significantly to the enhancements of electrical conductivity and thermoelectric power factor. The detailed analysis of the data in the light of first-principles calculations results indicates that the increased carrier concentration can be attributed to the Sn-vacancy-induced Fermi level downshift and the interplay between the vacancy states and valence bands. Furthermore, vacancies break translation symmetry and thus enhance phonon scattering, leading to extralow thermal conductivity. Such high ZT value ∼2.1 is achieved by synergistically optimizing both electrical- and thermal-transport properties of polycrystalline SnSe. The vast increase in ZT for polycrystalline SnSe may accelerate practical applications of this material in highly effective solid-state thermoelectric devices.
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Affiliation(s)
- Wei Wei
- MIIT Key Laboratory of Advanced Metallic and Intermetallic Materials Technology, School of Materials Science and Engineering, Nanjing University of Science and Technology , Nanjing 210094, China
| | - Cheng Chang
- School of Materials Science and Engineering, Beihang University , Beijing 100091, China
| | - Teng Yang
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences , 72 Wenhua Road, Shenyang 110016, China
| | - Jizi Liu
- MIIT Key Laboratory of Advanced Metallic and Intermetallic Materials Technology, School of Materials Science and Engineering, Nanjing University of Science and Technology , Nanjing 210094, China
| | - Huaichao Tang
- State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University , Beijing 100084, China
| | - Jian Zhang
- Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences , Hefei 230031, China
| | - Yusheng Li
- MIIT Key Laboratory of Advanced Metallic and Intermetallic Materials Technology, School of Materials Science and Engineering, Nanjing University of Science and Technology , Nanjing 210094, China
| | - Feng Xu
- MIIT Key Laboratory of Advanced Metallic and Intermetallic Materials Technology, School of Materials Science and Engineering, Nanjing University of Science and Technology , Nanjing 210094, China
| | - Zhidong Zhang
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences , 72 Wenhua Road, Shenyang 110016, China
| | - Jing-Feng Li
- State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University , Beijing 100084, China
| | - Guodong Tang
- MIIT Key Laboratory of Advanced Metallic and Intermetallic Materials Technology, School of Materials Science and Engineering, Nanjing University of Science and Technology , Nanjing 210094, China
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Zhou Y, Zhao LD. Promising Thermoelectric Bulk Materials with 2D Structures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1702676. [PMID: 28737228 DOI: 10.1002/adma.201702676] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2017] [Revised: 06/14/2017] [Indexed: 06/07/2023]
Abstract
Given that more than two thirds of all energy is lost, mostly as waste heat, in utilization processes worldwide, thermoelectric materials, which can directly convert waste heat to electricity, provide an alternative option for optimizing energy utilization processes. After the prediction that superlattices may show high thermoelectric performance, various methods based on quantum effects and superlattice theory have been adopted to analyze bulk materials, leading to the rapid development of thermoelectric materials. Bulk materials with two-dimensional (2D) structures show outstanding properties, and their high performance originates from both their low thermal conductivity and high Seebeck coefficient due to their strong anisotropic features. Here, the advantages of superlattices for enhancing the thermoelectric performance, the transport mechanism in bulk materials with 2D structures, and optimization methods are discussed. The phenomenological transport mechanism in these materials indicates that thermal conductivities are reduced in 2D materials with intrinsically short mean free paths. Recent progress in the transport mechanisms of Bi2 Te3 -, SnSe-, and BiCuSeO-based systems is summarized. Finally, possible research directions to enhance the thermoelectric performance of bulk materials with 2D structures are briefly considered.
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Affiliation(s)
- Yiming Zhou
- School of Materials Science and Engineering, Beihang University, Beijing, 100191, China
- Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, 100191, China
| | - Li-Dong Zhao
- School of Materials Science and Engineering, Beihang University, Beijing, 100191, China
- Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, 100191, China
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