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Luo J, Ren G, Campbell BM, Zhang D, Cao T, Mishra R, Sadtler B. Spontaneous Seed Formation during Electrodeposition Drives Epitaxial Growth of Metastable Bismuth Selenide Microcrystals. J Am Chem Soc 2022; 144:18272-18285. [PMID: 36173417 DOI: 10.1021/jacs.2c05261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Materials with metastable phases can exhibit vastly different properties from their thermodynamically favored counterparts. Methods to synthesize metastable phases without the need for high-temperature or high-pressure conditions would facilitate their widespread use. We report on the electrochemical growth of microcrystals of bismuth selenide, Bi2Se3, in the metastable orthorhombic phase at room temperature in aqueous solution. Rather than direct epitaxy with the growth substrate, the spontaneous formation of a seed layer containing nanocrystals of cubic BiSe enforces the metastable phase. We first used single-crystal silicon substrates with a range of resistivities and different orientations to identify the conditions needed to produce the metastable phase. When the applied potential during electrochemical growth is positive of the reduction potential of Bi3+, an initial, Bi-rich seed layer forms. Electron microscopy imaging and diffraction reveal that the seed layer consists of nanocrystals of cubic BiSe embedded within an amorphous matrix of Bi and Se. Using density functional theory calculations, we show that epitaxial matching between cubic BiSe and orthorhombic Bi2Se3 can help stabilize the metastable orthorhombic phase over the thermodynamically stable rhombohedral phase. The spontaneous formation of the seed layer enables us to grow orthorhombic Bi2Se3 on a variety of substrates including single-crystal silicon with different orientations, polycrystalline fluorine-doped tin oxide, and polycrystalline gold. The ability to stabilize the metastable phase through room-temperature electrodeposition in aqueous solution without requiring a single-crystal substrate broadens the range of applications for this semiconductor in optoelectronic and electrochemical devices.
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Affiliation(s)
- Jiang Luo
- Department of Chemistry, Washington University, St. Louis, Missouri 63130, United States
| | - Guodong Ren
- Institute of Materials Science & Engineering, Washington University, St. Louis, Missouri 63130, United States
| | - Brandon M Campbell
- Department of Chemistry, Washington University, St. Louis, Missouri 63130, United States
| | - Dongyan Zhang
- Department of Chemistry, Washington University, St. Louis, Missouri 63130, United States
| | - Tengfei Cao
- Department of Mechanical Engineering & Materials Science, Washington University, St. Louis, Missouri 63130, United States
| | - Rohan Mishra
- Institute of Materials Science & Engineering, Washington University, St. Louis, Missouri 63130, United States.,Department of Mechanical Engineering & Materials Science, Washington University, St. Louis, Missouri 63130, United States
| | - Bryce Sadtler
- Department of Chemistry, Washington University, St. Louis, Missouri 63130, United States.,Institute of Materials Science & Engineering, Washington University, St. Louis, Missouri 63130, United States
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Park H, Jeong K, Maeng I, Sim KI, Pathak S, Kim J, Hong SB, Jung TS, Kang C, Kim JH, Hong J, Cho MH. Enhanced Spin-to-Charge Conversion Efficiency in Ultrathin Bi 2Se 3 Observed by Spintronic Terahertz Spectroscopy. ACS APPLIED MATERIALS & INTERFACES 2021; 13:23153-23160. [PMID: 33945256 DOI: 10.1021/acsami.1c03168] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Owing to their remarkable spin-charge conversion (SCC) efficiency, topological insulators (TIs) are the most attractive candidates for spin-orbit torque generators. The simple method of enhancing SCC efficiency is to reduce the thickness of TI films to minimize the trivial bulk contribution. However, when the thickness reaches the ultrathin regime, the SCC efficiency decreases owing to intersurface hybridization. To overcome these contrary effects, we induced dehybridization of the ultrathin TI film by breaking the inversion symmetry between surfaces. For the TI film grown on an oxygen-deficient transition-metal oxide, the unbonded transition-metal d-orbitals affected only the bottom surface, resulting in asymmetric surface band structures. Spintronic terahertz emission spectroscopy, an emerging tool for investigating the SCC characteristics, revealed that the resulting SCC efficiency in symmetry-broken ultrathin Bi2Se3 was enhanced by up to ∼2.4 times.
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Affiliation(s)
- Hanbum Park
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Kwangsik Jeong
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
- Division of Physics and Semiconductor Science, Dongguk University, Seoul 04620, Republic of Korea
| | - InHee Maeng
- YUHS-KRIBB, Medical Convergence Research Institute, College of Medicine, Yonsei University, Seoul 03722, Republic of Korea
| | - Kyung Ik Sim
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon 16419, Republic of Korea
| | - Sachin Pathak
- Department of Physics, School of Engineering, University of Petroleum and Energy Studies, Dehradun 248007, Uttarakhand, India
- Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of Korea
| | - Jonghoon Kim
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Seok-Bo Hong
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Taek Sun Jung
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Chul Kang
- Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju 61005, Republic of Korea
| | - Jae Hoon Kim
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Jongill Hong
- Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of Korea
| | - Mann-Ho Cho
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
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