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Lim SY, Kim HG, Choi YW, Taniguchi T, Watanabe K, Choi HJ, Cheong H. Modulation of Phonons and Excitons Due to Moiré Potentials in Twisted Bilayer of WSe 2/MoSe 2. ACS Nano 2023. [PMID: 37410957 DOI: 10.1021/acsnano.3c03883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/08/2023]
Abstract
The application of two-dimensional materials has been expanded by introducing the twisted bilayer (TBL) system. However, the landscape of the interlayer interaction in hetero-TBLs has not yet been fully understood, while that in homo-TBLs has been extensively studied, with the dependence on the twist angle between the constituent layers. Here, we present detailed analyses on the interlayer interaction that depends on the twist angle in WSe2/MoSe2 hetero-TBL via Raman and photoluminescence studies combined with first-principles calculation. We observe interlayer vibrational modes, moiré phonons, and the interlayer excitonic states that evolve with the twist angle and identify different regimes with distinct characteristics of such features. Moreover, the interlayer excitons that appear strong in the hetero-TBLs with twist angles near 0° or 60° have different energies and photoluminescence excitation spectra for the two cases, which results from different electronic structures and carrier relaxation dynamics. These results would enable a better understanding of the interlayer interaction in hetero-TBLs.
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Affiliation(s)
- Soo Yeon Lim
- Department of Physics, Sogang University, Seoul 04107, Korea
| | - Han-Gyu Kim
- Department of Physics, Yonsei University, Seoul 03722, Korea
| | - Young Woo Choi
- Department of Physics, Yonsei University, Seoul 03722, Korea
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Nakami, Tsukuba, Ibaraki 305-0044 Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, Nakami, Tsukuba, Ibaraki 305-0044 Japan
| | | | - Hyeonsik Cheong
- Department of Physics, Sogang University, Seoul 04107, Korea
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2
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Zhou H, Llanes JP, Lotfi M, Sarntinoranont M, Simmons CS, Subhash G. Label-Free Quantification of Microscopic Alignment in Engineered Tissue Scaffolds by Polarized Raman Spectroscopy. ACS Biomater Sci Eng 2023; 9:3206-3218. [PMID: 37170804 DOI: 10.1021/acsbiomaterials.3c00242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Monitoring of extracellular matrix (ECM) microstructure is essential in studying structure-associated cellular processes, improving cellular function, and for ensuring sufficient mechanical integrity in engineered tissues. This paper describes a novel method to study the microscale alignment of the matrix in engineered tissue scaffolds (ETS) that are usually composed of a variety of biomacromolecules derived by cells. First, a trained loading function was derived from Raman spectra of highly aligned native tissue via principal component analysis (PCA), where prominent changes associated with specific Raman bands (e.g., 1444, 1465, 1605, 1627-1660, and 1665-1689 cm-1) were detected with respect to the polarization angle. These changes were mainly caused by the aligned matrix of many compounds within the tissue relative to the laser polarization, including proteins, lipids, and carbohydrates. Hence this trained function was applied to quantify the alignment within ETS of various matrix components derived by cells. Furthermore, a simple metric called Amplitude Alignment Metric (AAM) was derived to correlate the orientation dependence of polarized Raman spectra of ETS to the degree of matrix alignment. It was found that the AAM was significantly higher in anisotropic ETS than isotropic ones. The PRS method revealed a lower p-value for distinguishing the alignment between these two types of ETS as compared to the microscopic method for detecting fluorescent-labeled protein matrices at a similar microscopic scale. These results indicate that the anisotropy of a complex matrix in engineered tissue can be assessed at the microscopic scale using a PRS-based simple metric, which is superior to the traditional microscopic method. This PRS-based method can serve as a complementary tool for the design and assessment of engineered tissues that mimic the native matrix organizational microstructures.
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Affiliation(s)
- Hui Zhou
- Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611, United States
| | - Janny Piñeiro Llanes
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, Florida 32611, United States
| | - Maedeh Lotfi
- Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611, United States
| | - Malisa Sarntinoranont
- Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611, United States
| | - Chelsey S Simmons
- Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611, United States
| | - Ghatu Subhash
- Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611, United States
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Zou B, Wang X, Zhou Y, Zhou Y, Wu Y, Xing T, He Y, Yang J, Chen Y, Ren P, Sun H. Optical Effect Modulation in Polarized Raman Spectroscopy of Transparent Layered α-MoO 3. Small 2023; 19:e2206932. [PMID: 36807515 DOI: 10.1002/smll.202206932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 01/15/2023] [Indexed: 05/11/2023]
Abstract
Optical anisotropy, which is quantified by birefringence (Δn) and linear dichroism (Δk), can significantly modulate the angle-resolved polarized Raman spectroscopy (ARPRS) response of anisotropic layered materials (ALMs) by external interference. This work studies the separate modulation of birefringence on the ARPRS response and the intrinsic response by selecting transparent birefringent crystal α-MoO3 as an excellent platform. It is found that there are several anomalous ARPRS responses in α-MoO3 that cannot be reproduced by the real Raman tensor widely used in non-absorbing materials; however, they can be well explained by considering the birefringence-induced Raman selection rules. Moreover, the systematic thickness-dependent study indicates that birefringence modulates the ARPRS response to render an interference pattern; however, the amplitude of modulation is considerably lower than that by linear dichroism as occurred in black phosphorous. This weak modulation brings convenience to the crystal orientation determination of transparent ALMs. Combining the atomic vibrational pattern and bond polarizability model, the intrinsic ARPRS response of α-MoO3 is analyzed, giving the physical origins of the Raman anisotropy. This study employs α-MoO3 as an example, although it is generally applicable to all transparent birefringent ALMs.
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Affiliation(s)
- Bo Zou
- School of Science and Ministry of Industry and Information Technology Key Laboratory of Micro-Nano Optoelectronic Information System, Harbin Institute of Technology Shenzhen, Shenzhen, Guangdong, 518055, P. R. China
| | - Xiaonan Wang
- School of Science and Ministry of Industry and Information Technology Key Laboratory of Micro-Nano Optoelectronic Information System, Harbin Institute of Technology Shenzhen, Shenzhen, Guangdong, 518055, P. R. China
| | - Yu Zhou
- School of Science and Ministry of Industry and Information Technology Key Laboratory of Micro-Nano Optoelectronic Information System, Harbin Institute of Technology Shenzhen, Shenzhen, Guangdong, 518055, P. R. China
| | - Yan Zhou
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, P. R. China
| | - Yanyan Wu
- School of Science and Ministry of Industry and Information Technology Key Laboratory of Micro-Nano Optoelectronic Information System, Harbin Institute of Technology Shenzhen, Shenzhen, Guangdong, 518055, P. R. China
| | - Tiantian Xing
- School of Science and Ministry of Industry and Information Technology Key Laboratory of Micro-Nano Optoelectronic Information System, Harbin Institute of Technology Shenzhen, Shenzhen, Guangdong, 518055, P. R. China
| | - Yang He
- School of Science and Ministry of Industry and Information Technology Key Laboratory of Micro-Nano Optoelectronic Information System, Harbin Institute of Technology Shenzhen, Shenzhen, Guangdong, 518055, P. R. China
| | - Jinfeng Yang
- School of Science and Ministry of Industry and Information Technology Key Laboratory of Micro-Nano Optoelectronic Information System, Harbin Institute of Technology Shenzhen, Shenzhen, Guangdong, 518055, P. R. China
| | - Yuxiang Chen
- School of Science and Ministry of Industry and Information Technology Key Laboratory of Micro-Nano Optoelectronic Information System, Harbin Institute of Technology Shenzhen, Shenzhen, Guangdong, 518055, P. R. China
| | - Peng Ren
- School of Science and Ministry of Industry and Information Technology Key Laboratory of Micro-Nano Optoelectronic Information System, Harbin Institute of Technology Shenzhen, Shenzhen, Guangdong, 518055, P. R. China
| | - Huarui Sun
- School of Science and Ministry of Industry and Information Technology Key Laboratory of Micro-Nano Optoelectronic Information System, Harbin Institute of Technology Shenzhen, Shenzhen, Guangdong, 518055, P. R. China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi, 030006, P. R. China
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Guo Z, Wang L, Han M, Zhao E, Zhu L, Guo W, Tan J, Liu B, Chen XQ, Lin J. One-Step Growth of Bilayer 2H-1T' MoTe 2 van der Waals Heterostructures with Interlayer-Coupled Resonant Phonon Vibration. ACS Nano 2022; 16:11268-11277. [PMID: 35848623 DOI: 10.1021/acsnano.2c04664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
2H-1T' MoTe2 van der Waals heterostructures (vdWHs) have promising applications in optoelectronics due to a seamlessly homogeneous semiconductor-metal coupled interface. However, the existing methods to fabricate such vdWHs involved complicated steps that may deteriorate the interfacial coupling and are also lacking precise thickness control capability. Here, a one-step growth method was developed to controllably grow bilayer 2H-1T' MoTe2 vdWHs in the small growth window overlapped for both phases. Atomic-resolution low-voltage transmission electron microscopy shows the distinct moiré patterns in the bilayer vdWHs, revealing the epitaxial nature of the top 2H phase with the lattice parameters regulated by the underneath 1T' phase. Such epitaxially stacked bilayer vdWHs modulate the interlayer coupling by resonating their vibration modes, as unveiled by the angle-resolved polarized Raman spectroscopy and first-principles calculations.
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Affiliation(s)
- Zenglong Guo
- Department of Physics, Shenzhen Institute for Quantum Science and Engineering (SIQSE), Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
- Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
| | - Lei Wang
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 110016 Shenyang, People's Republic of China
- School of Materials Science and Engineering, University of Science and Technology of China, 110016 Shenyang, People's Republic of China
| | - Mengjiao Han
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, People's Republic of China
| | - Erding Zhao
- Department of Physics, Shenzhen Institute for Quantum Science and Engineering (SIQSE), Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
- Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
| | - Liang Zhu
- Department of Physics, Shenzhen Institute for Quantum Science and Engineering (SIQSE), Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
- Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
| | - Weiteng Guo
- Department of Physics, Shenzhen Institute for Quantum Science and Engineering (SIQSE), Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
- Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
| | - Junyang Tan
- Shenzhen Geim Graphene Center, Tsinghua-Berkeley Shenzhen Institute and Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055, People's Republic of China
| | - Bilu Liu
- Shenzhen Geim Graphene Center, Tsinghua-Berkeley Shenzhen Institute and Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055, People's Republic of China
| | - Xing-Qiu Chen
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 110016 Shenyang, People's Republic of China
- School of Materials Science and Engineering, University of Science and Technology of China, 110016 Shenyang, People's Republic of China
| | - Junhao Lin
- Department of Physics, Shenzhen Institute for Quantum Science and Engineering (SIQSE), Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
- Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
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Kim UJ, Nam SH, Seo J, Yang M, Fu Q, Liu Z, Son H, Lee M, Hahm MG. Visualizing Line Defects in non-van der Waals Bi 2O 2Se Using Raman Spectroscopy. ACS Nano 2022; 16:3637-3646. [PMID: 35166540 DOI: 10.1021/acsnano.1c06598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Atomic-layered materials, such as high-quality bismuth oxychalcogenides, which are composed of oppositely charged alternate layers grown using chemical vapor deposition, have attracted considerable attention. Their physical properties are well-suited for high-speed, low-power-consumption optoelectronic devices, and the rapid determination of their crystallographic characteristics is crucial for scalability and integration. In this study, we introduce how the crystallographic structure and quality of such materials can be projected through Raman spectroscopy analysis. Frequency modes at ∼55, ∼78, ∼360, and ∼434 cm-1 were detected, bearing out theoretical calculations from the literature. The low-frequency modes positioned at 55 and 78 cm-1 were activated by structural defects, such as grain boundaries and O-rich edges in the Bi2O2Se crystals, accompanied by sensitivity to the excitation energy. Furthermore, the line defects at ∼55 cm-1 exhibited a strong 2-fold polarization dependence, similar to graphene/graphite edges. Our results can help illuminate the mechanism for activating the Raman-active mode from the infrared active mode by defects, as well as the electronic structures of these two-dimensional layered materials. We also suggest that the nanoscale width line defects in Bi2O2Se can be visualized using Raman spectroscopy.
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Affiliation(s)
- Un Jeong Kim
- Advanced Sensor Laboratory, Samsung Advanced Institute of Technology, Suwon, Gyeonggi-do 16419, Republic of Korea
| | - Seung Hyun Nam
- Department of Materials Science and Engineering, Inha University, 100 Inha-ro, Michuhol-gu, Incheon, 22212, Republic of Korea
| | - Juyeon Seo
- Department of Materials Science and Engineering, Inha University, 100 Inha-ro, Michuhol-gu, Incheon, 22212, Republic of Korea
| | - Mino Yang
- Korea Basic Science Institute Seoul, Seoul, 02841, Republic of Korea
| | - Qundong Fu
- School of Materials Science & Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore
| | - Zheng Liu
- School of Materials Science & Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore
| | - Hyungbin Son
- School of Integrative Engineering, Chung-Ang University, Seoul, 06974, Republic of Korea
| | - Moonsang Lee
- Department of Materials Science and Engineering, Inha University, 100 Inha-ro, Michuhol-gu, Incheon, 22212, Republic of Korea
| | - Myung Gwan Hahm
- Department of Materials Science and Engineering, Inha University, 100 Inha-ro, Michuhol-gu, Incheon, 22212, Republic of Korea
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6
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Dai Y, Yu Q, Yang X, Guo K, Zhang Y, Zhang Y, Zhang J, Li J, Chen J, Deng H, Xian T, Wang X, Wu J, Zhang K. Controllable Synthesis of Narrow-Gap van der Waals Semiconductor Nb 2GeTe 4 with Asymmetric Architecture for Ultrafast Photonics. ACS Nano 2022; 16:4239-4250. [PMID: 35191693 DOI: 10.1021/acsnano.1c10241] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Ultrafast photonics has become an interdisciplinary topic of great consequence due to the spectacular progress of compact and efficient ultrafast pulse generation. Wide spectrum bandwidth is the key element for ultrafast pulse generation due to the Fourier transform limitation. Herein, monoclinic Nb2GeTe4, an emerging class of ternary narrow-gap semiconductors, was used as a real saturable absorber (SA), which manifests superior wide-range optical absorption. The crystallization form and growth mechanism of Nb2GeTe4 were revealed by a thermodynamic phase diagram. Furthermore, the Nb2GeTe4-SA showed reliable saturation intensity and larger modulation depth, ascribed to a built-in electric field driven by the asymmetric crystal architecture confirmed via X-ray diffraction, polarized Raman spectra, and scanning transmission electron microscopy. Based on the Nb2GeTe4-SA, femtosecond mode-locked operation with good overall performance was achieved by a properly designed ring cavity. These results suggest that Nb2GeTe4 shows great promise for ultrafast photonic applications and arouse interests in exploring the intriguing properties of the ternary van der Waals material family.
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Affiliation(s)
- Yongping Dai
- CAS Key Laboratory of Nanophotonic Materials and Devices & Key Laboratory of Nanodevices and Applications, i-Lab, Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences, Suzhou 215123, China
- Nano Science and Technology Institute, University of Science and Technology of China, Suzhou 215123, China
| | - Qiang Yu
- CAS Key Laboratory of Nanophotonic Materials and Devices & Key Laboratory of Nanodevices and Applications, i-Lab, Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences, Suzhou 215123, China
- College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China
| | - Xiaoxin Yang
- Nano Science and Technology Institute, University of Science and Technology of China, Suzhou 215123, China
- Shenzhen Key Laboratory of Nanobiomechanics, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Kun Guo
- College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China
| | - Yan Zhang
- CAS Key Laboratory of Nanophotonic Materials and Devices & Key Laboratory of Nanodevices and Applications, i-Lab, Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences, Suzhou 215123, China
| | - Yushuang Zhang
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha, Hunan 410082, China
| | - Junrong Zhang
- CAS Key Laboratory of Nanophotonic Materials and Devices & Key Laboratory of Nanodevices and Applications, i-Lab, Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences, Suzhou 215123, China
| | - Jie Li
- CAS Key Laboratory of Nanophotonic Materials and Devices & Key Laboratory of Nanodevices and Applications, i-Lab, Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences, Suzhou 215123, China
| | - Jie Chen
- CAS Key Laboratory of Nanophotonic Materials and Devices & Key Laboratory of Nanodevices and Applications, i-Lab, Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences, Suzhou 215123, China
- Shanghai IC R&D Center, Shanghai 201210, China
| | - Haiqin Deng
- College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China
| | - Tianhao Xian
- State Key Laboratory of Advanced Optical Communication System and Networks, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Xiao Wang
- Shenzhen Key Laboratory of Nanobiomechanics, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Jian Wu
- College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China
| | - Kai Zhang
- CAS Key Laboratory of Nanophotonic Materials and Devices & Key Laboratory of Nanodevices and Applications, i-Lab, Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences, Suzhou 215123, China
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Lee S, Jung JE, Kim HG, Lee Y, Park JM, Jang J, Yoon S, Ghosh A, Kim M, Kim J, Na W, Kim J, Choi HJ, Cheong H, Kim K. γ-GeSe: A New Hexagonal Polymorph from Group IV-VI Monochalcogenides. Nano Lett 2021; 21:4305-4313. [PMID: 33970636 DOI: 10.1021/acs.nanolett.1c00714] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The family of group IV-VI monochalcogenides has an atomically puckered layered structure, and their atomic bond configuration suggests the possibility for the realization of various polymorphs. Here, we report the synthesis of the first hexagonal polymorph from the family of group IV-VI monochalcogenides, which is conventionally orthorhombic. Recently predicted four-atomic-thick hexagonal GeSe, so-called γ-GeSe, is synthesized and clearly identified by complementary structural characterizations, including elemental analysis, electron diffraction, high-resolution transmission electron microscopy imaging, and polarized Raman spectroscopy. The electrical and optical measurements indicate that synthesized γ-GeSe exhibits high electrical conductivity of 3 × 105 S/m, which is comparable to those of other two-dimensional layered semimetallic crystals. Moreover, γ-GeSe can be directly grown on h-BN substrates, demonstrating a bottom-up approach for constructing vertical van der Waals heterostructures incorporating γ-GeSe. The newly identified crystal symmetry of γ-GeSe warrants further studies on various physical properties of γ-GeSe.
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Affiliation(s)
- Sol Lee
- Department of Physics, Yonsei University, Seoul 03722, Korea
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul 03722, Korea
| | - Joong-Eon Jung
- Department of Physics, Yonsei University, Seoul 03722, Korea
| | - Han-Gyu Kim
- Department of Physics, Yonsei University, Seoul 03722, Korea
| | - Yangjin Lee
- Department of Physics, Yonsei University, Seoul 03722, Korea
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul 03722, Korea
| | - Je Myoung Park
- Department of Physics, Sogang University, Seoul 04107, Korea
| | - Jeongsu Jang
- Department of Physics, Yonsei University, Seoul 03722, Korea
| | - Sangho Yoon
- Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 37673, Korea
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Korea
| | - Arnab Ghosh
- Department of Physics, Yonsei University, Seoul 03722, Korea
| | - Minseol Kim
- Department of Physics, Yonsei University, Seoul 03722, Korea
| | - Joonho Kim
- Department of Physics, Yonsei University, Seoul 03722, Korea
| | - Woongki Na
- Department of Physics, Sogang University, Seoul 04107, Korea
| | - Jonghwan Kim
- Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 37673, Korea
- Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), Pohang 37673, Korea
| | | | - Hyeonsik Cheong
- Department of Physics, Sogang University, Seoul 04107, Korea
| | - Kwanpyo Kim
- Department of Physics, Yonsei University, Seoul 03722, Korea
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul 03722, Korea
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8
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Jang M, Bae H, Lee Y, Na W, Yu B, Choi S, Cheong H, Lee H, Kim K. Unidirectional Alignment of AgCN Microwires on Distorted Transition Metal Dichalcogenide Crystals. ACS Appl Mater Interfaces 2021; 13:8727-8735. [PMID: 33561342 DOI: 10.1021/acsami.0c20246] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Van der Waals epitaxy on the surface of two-dimensional (2D) layered crystals has gained significant research interest for the assembly of well-ordered nanostructures and fabrication of vertical heterostructures based on 2D crystals. Although van der Waals epitaxial assembly on the hexagonal phase of transition metal dichalcogenides (TMDCs) has been relatively well characterized, a comparable study on the distorted octahedral phase (1T' or Td) of TMDCs is largely lacking. Here, we investigate the assembly behavior of one-dimensional (1D) AgCN microwires on various distorted TMDC crystals, namely 1T'-MoTe2, Td-WTe2, and 1T'-ReS2. The unidirectional alignment of AgCN chains is observed on these crystals, reflecting the symmetry of underlying distorted TMDCs. Polarized Raman spectroscopy and transmission electron microscopy directly confirm that AgCN chains display the remarkable alignment behavior along the distorted chain directions of underlying TMDCs. The observed unidirectional assembly behavior can be attributed to the favorable adsorption configurations of 1D chains along the substrate distortion, which is supported by our theoretical calculations and observation of similar assembly behavior from different cyanide chains. The aligned AgCN microwires can be harnessed as facile markers to identify polymorphs and crystal orientations of TMDCs.
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Affiliation(s)
- Myeongjin Jang
- Department of Physics, Yonsei University, Seoul 03722, Korea
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul 03722, Korea
| | - Hyeonhu Bae
- Department of Physics, Konkuk University, Seoul 05029, Korea
| | - Yangjin Lee
- Department of Physics, Yonsei University, Seoul 03722, Korea
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul 03722, Korea
| | - Woongki Na
- Department of Physics, Sogang University, Seoul 04107, Korea
| | - Byungkyu Yu
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul 03722, Korea
| | - Soyeon Choi
- Department of Physics, Yonsei University, Seoul 03722, Korea
| | - Hyeonsik Cheong
- Department of Physics, Sogang University, Seoul 04107, Korea
| | - Hoonkyung Lee
- Department of Physics, Konkuk University, Seoul 05029, Korea
| | - Kwanpyo Kim
- Department of Physics, Yonsei University, Seoul 03722, Korea
- Center for Nanomedicine, Institute for Basic Science (IBS), Seoul 03722, Korea
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9
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Abstract
We performed polarized Raman spectroscopy on mechanically exfoliated few-layer MoTe2 samples and observed both 1T' and Td phases at room temperature. Few-layer 1T' and Td MoTe2 exhibited a significant difference especially in interlayer vibration modes, from which the interlayer coupling strengths were extracted using the linear chain model: strong in-plane anisotropy was observed in both phases. Furthermore, temperature-dependent Raman measurements revealed a peculiar phase transition behavior in few-layer 1T' MoTe2. In contrast to bulk 1T' MoTe2 crystals, where the phase transition to the Td phase occurs at ∼250 K, the temperature-driven phase transition to the Td phase is increasingly suppressed as the thickness is reduced, and the transition and the critical temperature varied dramatically from sample to sample even for the same thickness. Raman spectra of intermediate phases that correspond to neither 1T' nor Td phase with different interlayer vibration modes were observed, which suggests that several metastable phases exist with similar total energies.
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Affiliation(s)
- Yeryun Cheon
- Department of Physics, Sogang University, Seoul 04107, Korea
| | - Soo Yeon Lim
- Department of Physics, Sogang University, Seoul 04107, Korea
| | - Kangwon Kim
- Department of Physics, Sogang University, Seoul 04107, Korea
| | - Hyeonsik Cheong
- Department of Physics, Sogang University, Seoul 04107, Korea
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10
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Dhanabalan B, Leng YC, Biffi G, Lin ML, Tan PH, Infante I, Manna L, Arciniegas MP, Krahne R. Directional Anisotropy of the Vibrational Modes in 2D-Layered Perovskites. ACS Nano 2020; 14:4689-4697. [PMID: 32275388 PMCID: PMC8007126 DOI: 10.1021/acsnano.0c00435] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The vibrational modes in organic/inorganic layered perovskites are of fundamental importance for their optoelectronic properties. The hierarchical architecture of the Ruddlesden-Popper phase of these materials allows for distinct directionality of the vibrational modes with respect to the main axes of the pseudocubic lattice in the octahedral plane. Here, we study the directionality of the fundamental phonon modes in single exfoliated Ruddlesden-Popper perovskite flakes with polarized Raman spectroscopy at ultralow frequencies. A wealth of Raman bands is distinguished in the range from 15 to 150 cm-1 (2-15 meV), whose features depend on the organic cation species, on temperature, and on the direction of the linear polarization of the incident light. By controlling the angle of the linear polarization of the excitation laser with respect to the in-plane axes of the octahedral layer, we gain detailed information on the symmetry of the vibrational modes. The choice of two different organic moieties, phenethylammonium (PEA) and butylammonium (BA), allows us to discern the influence of the linker molecules, evidencing strong anisotropy of the vibrations for the (PEA)2PbBr4 samples. Temperature-dependent Raman measurements reveal that the broad phonon bands observed at room temperature consist of a series of sharp modes and that such mode splitting strongly differs for the different organic moieties and vibrational bands. Softer molecules such as BA result in lower vibrational frequencies and splitting into fewer modes, while more rigid molecules such as PEA lead to higher frequency oscillations and larger number of Raman peaks at low temperature. Interestingly, in distinct bands the number of peaks in the Raman bands is doubled for the rigid PEA compared to the soft BA linkers. Our work shows that the coupling to specific vibrational modes can be controlled by the incident light polarization and choice of the organic moiety, which could be exploited for tailoring exciton-phonon interaction, and for optical switching of the optoelectronic properties of such 2D layered materials.
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Affiliation(s)
- Balaji Dhanabalan
- Istituto
Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genoa, Italy
- Dipartimento
di Chimica e Chimica Industriale, Università
degli Studi di Genova, Via Dodecaneso, 31, 16146 Genova, Italy
| | - Yu-Chen Leng
- State
Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, 100083 Beijing, China
- Center
of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, 100190 Beijing, China
| | - Giulia Biffi
- Istituto
Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genoa, Italy
- Dipartimento
di Chimica e Chimica Industriale, Università
degli Studi di Genova, Via Dodecaneso, 31, 16146 Genova, Italy
| | - Miao-Ling Lin
- State
Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, 100083 Beijing, China
- Center
of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, 100190 Beijing, China
| | - Ping-Heng Tan
- State
Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, 100083 Beijing, China
- Center
of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, 100190 Beijing, China
| | - Ivan Infante
- Istituto
Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genoa, Italy
| | - Liberato Manna
- Istituto
Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genoa, Italy
| | | | - Roman Krahne
- Istituto
Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genoa, Italy
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11
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Islam A, Du W, Pashaei V, Jia H, Wang Z, Lee J, Ye GJ, Chen XH, Feng PXL. Discerning Black Phosphorus Crystal Orientation and Anisotropy by Polarized Reflectance Measurement. ACS Appl Mater Interfaces 2018; 10:25629-25637. [PMID: 29938499 DOI: 10.1021/acsami.8b05408] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Strong in-plane anisotropy of atomic layer and thin-film black phosphorus (P) offers new device perspectives and stimulates increasing interest and explorations, where precisely determining the black P crystal orientation and anisotropic axes is a necessity. Here, we demonstrate that the crystal orientation and intrinsic in-plane optical anisotropy of black P crystals in a broad thickness range (from ∼5 to ∼300 nm) can be directly and precisely determined, by polarized reflectance measurement alone, in visible range. Combining experiments with modeling of optical anisotropy and multilayer interference effects, we elucidate the underlying principles and validate these measurements. The polarized reflectance method is not only easy to implement but also deterministic, nondestructive, and effective for both on-substrate and suspended black P atomic layers and thin films.
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Affiliation(s)
- Arnob Islam
- Department of Electrical Engineering & Computer Science, Case School of Engineering , Case Western Reserve University , 10900 Euclid Avenue , Cleveland , Ohio 44106 , United States
| | - Wei Du
- Department of Electrical Engineering & Computer Science, Case School of Engineering , Case Western Reserve University , 10900 Euclid Avenue , Cleveland , Ohio 44106 , United States
| | - Vida Pashaei
- Department of Electrical Engineering & Computer Science, Case School of Engineering , Case Western Reserve University , 10900 Euclid Avenue , Cleveland , Ohio 44106 , United States
| | - Hao Jia
- Department of Electrical Engineering & Computer Science, Case School of Engineering , Case Western Reserve University , 10900 Euclid Avenue , Cleveland , Ohio 44106 , United States
| | - Zenghui Wang
- Department of Electrical Engineering & Computer Science, Case School of Engineering , Case Western Reserve University , 10900 Euclid Avenue , Cleveland , Ohio 44106 , United States
| | - Jaesung Lee
- Department of Electrical Engineering & Computer Science, Case School of Engineering , Case Western Reserve University , 10900 Euclid Avenue , Cleveland , Ohio 44106 , United States
| | - Guo Jun Ye
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics , University of Science and Technology of China , Hefei , Anhui 230026 , China
| | - Xian Hui Chen
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics , University of Science and Technology of China , Hefei , Anhui 230026 , China
| | - Philip X-L Feng
- Department of Electrical Engineering & Computer Science, Case School of Engineering , Case Western Reserve University , 10900 Euclid Avenue , Cleveland , Ohio 44106 , United States
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12
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Simoncini A, Tagliaferri V, Ucciardello N. High Thermal Conductivity of Copper Matrix Composite Coatings with Highly-Aligned Graphite Nanoplatelets. Materials (Basel) 2017; 10:ma10111226. [PMID: 29068424 PMCID: PMC5706173 DOI: 10.3390/ma10111226] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Revised: 10/18/2017] [Accepted: 10/23/2017] [Indexed: 11/29/2022]
Abstract
Nanocomposite coatings with highly-aligned graphite nanoplatelets in a copper matrix were successfully fabricated by electrodeposition. For the first time, the disposition and thermal conductivity of the nanofiller has been evaluated. The degree of alignment and inclination of the filling materials has been quantitatively evaluated by polarized micro-Raman spectroscopy. The room temperature values of the thermal conductivity were extracted for the graphite nanoplatelets by the dependence of the Raman G-peak frequency on the laser power excitation. Temperature dependency of the G-peak shift has been also measured. Most remarkable is the global thermal conductivity of 640 ± 20 W·m−1·K−1 (+57% of copper) obtained for the composite coating by the flash method. Our experimental results are accounted for by an effective medium approximation (EMA) model that considers the influence of filler geometry, orientation, and thermal conductivity inside a copper matrix.
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Affiliation(s)
- Alessandro Simoncini
- Department of Enterprise Engineering "Mario Lucertini", University of Rome "Tor Vergata", Via del Politecnico 1, 00133 Rome, Italy.
| | - Vincenzo Tagliaferri
- Department of Enterprise Engineering "Mario Lucertini", University of Rome "Tor Vergata", Via del Politecnico 1, 00133 Rome, Italy.
| | - Nadia Ucciardello
- Department of Enterprise Engineering "Mario Lucertini", University of Rome "Tor Vergata", Via del Politecnico 1, 00133 Rome, Italy.
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13
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Wen W, Zhu Y, Liu X, Hsu HP, Fei Z, Chen Y, Wang X, Zhang M, Lin KH, Huang FS, Wang YP, Huang YS, Ho CH, Tan PH, Jin C, Xie L. Anisotropic Spectroscopy and Electrical Properties of 2D ReS 2(1-x) Se 2x Alloys with Distorted 1T Structure. Small 2017; 13:1603788. [PMID: 28112865 DOI: 10.1002/smll.201603788] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Revised: 12/18/2016] [Indexed: 06/06/2023]
Abstract
2D black phosphorus (BP) and rhenium dichalcogenides (ReX2 , X = S, Se) possess intrinsic in-plane anisotropic physical properties arising from their low crystal lattice symmetry, which has inspired their novel applications in electronics, photonics, and optoelectronics. Different from BP with poor environmental stability, ReX2 has low-symmetry distorted 1T structures with excellent stability. In ReX2 , the electronic structure is weakly dependent on layer numbers, which restricts their property tunability and device applications. Here, the properties are tuned, such as optical bandgap, Raman anisotropy, and electrical transport, by alloying 2D ReS2 and ReSe2 . Photoluminescence emission energy of ReS2(1-x) Se2x monolayers (x from 0 to 1 with a step of 0.1) can be continuously tuned ranging from 1.62 to 1.31 eV. Polarization behavior of Raman modes, such as ReS2 -like peak at 212 cm-1 , shifts as the composition changes. Anisotropic electrical property is maintained in ReS2(1-x) Se2x with high electron mobility along b-axis for all compositions of ReS2(1-x) Se2x .
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Affiliation(s)
- Wen Wen
- CAS Key Laboratory of Standardization and Measurement for Nanotechnology, National Center for Nanoscience and Technology, Beijing, 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Yiming Zhu
- CAS Key Laboratory of Standardization and Measurement for Nanotechnology, National Center for Nanoscience and Technology, Beijing, 100190, P. R. China
- Department of Applied Physics, Chongqing University, Chongqing, 401331, P. R. China
| | - Xuelu Liu
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China
| | - Hung-Pin Hsu
- Department of Electronic Engineering, Ming Chi University of Technology, Taipei, 243, Taiwan, Republic of China
| | - Zhen Fei
- State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027, P. R. China
| | - Yanfeng Chen
- CAS Key Laboratory of Standardization and Measurement for Nanotechnology, National Center for Nanoscience and Technology, Beijing, 100190, P. R. China
| | - Xinsheng Wang
- CAS Key Laboratory of Standardization and Measurement for Nanotechnology, National Center for Nanoscience and Technology, Beijing, 100190, P. R. China
| | - Mei Zhang
- CAS Key Laboratory of Standardization and Measurement for Nanotechnology, National Center for Nanoscience and Technology, Beijing, 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Kuan-Hung Lin
- Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei, 106, Taiwan, Republic of China
| | - Fei-Sheng Huang
- Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei, 106, Taiwan, Republic of China
| | - Yi-Ping Wang
- Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei, 106, Taiwan, Republic of China
| | - Ying-Sheng Huang
- Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei, 106, Taiwan, Republic of China
| | - Ching-Hwa Ho
- Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei, 106, Taiwan, Republic of China
| | - Ping-Heng Tan
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China
| | - Chuanhong Jin
- State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027, P. R. China
| | - Liming Xie
- CAS Key Laboratory of Standardization and Measurement for Nanotechnology, National Center for Nanoscience and Technology, Beijing, 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
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14
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Sereda V, Ralbovsky NM, Vasudev MC, Naik RR, Lednev IK. Polarized Raman Spectroscopy for Determining the Orientation of di-D-phenylalanine Molecules in a Nanotube. J Raman Spectrosc 2016; 47:1056-1062. [PMID: 27795612 PMCID: PMC5079532 DOI: 10.1002/jrs.4884] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Self-assembly of short peptides into nanostructures has become an important strategy for the bottom-up fabrication of nanomaterials. Significant interest to such peptide-based building blocks is due to the opportunity to control the structure and properties of well-structured nanotubes, nanofibrils, and hydrogels. X-ray crystallography and solution NMR, two major tools of structural biology, have significant limitations when applied to peptide nanotubes because of their non-crystalline structure and large weight. Polarized Raman spectroscopy was utilized for structural characterization of well-aligned D-Diphenylalanine nanotubes. The orientation of selected chemical groups relative to the main axis of the nanotube was determined. Specifically, the C-N bond of CNH3+groups is oriented parallel to the nanotube axis, the peptides' carbonyl groups are tilted at approximately 54° from the axis and the COO- groups run perpendicular to the axis. The determined orientation of chemical groups allowed the understanding of the orientation of D-diphenylalanine molecule that is consistent with its equilibrium conformation. The obtained data indicate that there is only one orientation of D-diphenylalanine molecules with respect to the nanotube main axis.
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Affiliation(s)
- Valentin Sereda
- Department of Chemistry, University at Albany, SUNY, 1400 Washington Avenue, Albany, NY 12222, United States
| | - Nicole M. Ralbovsky
- Department of Chemistry, University at Albany, SUNY, 1400 Washington Avenue, Albany, NY 12222, United States
| | - Milana C. Vasudev
- Department of Bioengineering, University of Massachusetts Dartmouth, 285 Old Westport Road, Dartmouth MA 02747, United States
| | - Rajesh R. Naik
- Soft Matter Materials Branch, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Dayton, Ohio 45433, United States
| | - Igor K. Lednev
- Department of Chemistry, University at Albany, SUNY, 1400 Washington Avenue, Albany, NY 12222, United States
- Corresponding author: , Phone: (518) 591 8863, Fax: (518) 442-3462
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15
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Chenet DA, Aslan B, Huang PY, Fan C, van der Zande AM, Heinz TF, Hone JC. In-Plane Anisotropy in Mono- and Few-Layer ReS2 Probed by Raman Spectroscopy and Scanning Transmission Electron Microscopy. Nano Lett 2015; 15:5667-5672. [PMID: 26280493 DOI: 10.1021/acs.nanolett.5b00910] [Citation(s) in RCA: 182] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Rhenium disulfide (ReS2) is a semiconducting layered transition metal dichalcogenide that exhibits a stable distorted 1T phase. The reduced symmetry of this system leads to in-plane anisotropy in various material properties. Here, we demonstrate the strong anisotropy in the Raman scattering response for linearly polarized excitation. Polarized Raman scattering is shown to permit a determination of the crystallographic orientation of ReS2 through comparison with direct structural analysis by scanning transmission electron microscopy (STEM). Analysis of the frequency difference of appropriate Raman modes is also shown to provide a means of precisely determining layer thickness up to four layers.
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Affiliation(s)
| | | | | | | | - Arend M van der Zande
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Tony F Heinz
- Department of Applied Physics, Stanford University , Stanford, California 94305, United States
- SLAC National Accelerator Laboratory , 2575 Sand Hill Road, Menlo Park, California 94025, United States
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16
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Ribeiro HB, Pimenta MA, de Matos CJS, Moreira RL, Rodin AS, Zapata JD, de Souza EAT, Castro Neto AH. Unusual angular dependence of the Raman response in black phosphorus. ACS Nano 2015; 9:4270-6. [PMID: 25752593 DOI: 10.1021/acsnano.5b00698] [Citation(s) in RCA: 138] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Anisotropic materials are characterized by a unique optical response, which is highly polarization-dependent. Of particular interest are layered materials formed by the stacking of two-dimensional (2D) crystals that are naturally anisotropic in the direction perpendicular to the 2D planes. Black phosphorus (BP) is a stack of 2D phosphorene crystals and a highly anisotropic semiconductor with a direct band gap. We show that the angular dependence of polarized Raman spectra of BP is rather unusual and can be explained only by considering complex values for the Raman tensor elements. This result can be traced back to the electron-photon and electron-phonon interactions in this material.
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Affiliation(s)
- Henrique B Ribeiro
- †Mackgraphe-Graphene and Nanomaterials Research Center, Mackenzie Presbyterian University, 01302-907 São Paulo, Brazil
| | | | - Christiano J S de Matos
- †Mackgraphe-Graphene and Nanomaterials Research Center, Mackenzie Presbyterian University, 01302-907 São Paulo, Brazil
| | | | - Aleksandr S Rodin
- §Centre for Advanced 2D Materials and Graphene Research Centre Faculty of Science, National University of Singapore, 119077 Singapore
| | - Juan D Zapata
- †Mackgraphe-Graphene and Nanomaterials Research Center, Mackenzie Presbyterian University, 01302-907 São Paulo, Brazil
- ⊥Universidad de Antioquia, Medellin Colombia
| | - Eunézio A T de Souza
- †Mackgraphe-Graphene and Nanomaterials Research Center, Mackenzie Presbyterian University, 01302-907 São Paulo, Brazil
| | - Antonio H Castro Neto
- §Centre for Advanced 2D Materials and Graphene Research Centre Faculty of Science, National University of Singapore, 119077 Singapore
- ∥Department of Physics Faculty of Science, National University of Singapore, 119077 Singapore
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