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Yu M, Iddawela SA, Wang J, Hilse M, Thompson JL, Reifsnyder Hickey D, Sinnott SB, Law S. Quasi-Van der Waals Epitaxial Growth of γ'-GaSe Nanometer-Thick Films on GaAs(111)B Substrates. ACS NANO 2024; 18:17185-17196. [PMID: 38870462 DOI: 10.1021/acsnano.4c04194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2024]
Abstract
GaSe is an important member of the post-transition-metal chalcogenide family and is an emerging two-dimensional (2D) semiconductor material. Because it is a van der Waals material, it can be fabricated into atomic-scale ultrathin films, making it suitable for the preparation of compact, heterostructure devices. In addition, GaSe possesses unusual optical and electronic properties, such as a shift from an indirect-bandgap single-layer film to a direct-bandgap bulk material, rare intrinsic p-type conduction, and nonlinear optical behaviors. These properties make GaSe an appealing candidate for the fabrication of field-effect transistors, photodetectors, and photovoltaics. However, the wafer-scale production of pure GaSe single-crystal thin films remains challenging. This study develops an approach for the direct growth of nanometer-thick GaSe films on GaAs substrates by using molecular beam epitaxy. It yields smooth thin GaSe films with a rare γ'-polymorph. We analyze the formation mechanism of γ'-GaSe using density-functional theory and speculate that it is stabilized by Ga vacancies since the formation enthalpy of γ'-GaSe tends to become lower than that of other polymorphs when the Ga vacancy concentration increases. Finally, we investigate the growth conditions of GaSe, providing valuable insights for exploring 2D/three-dimensional (3D) quasi-van der Waals epitaxial growth.
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Affiliation(s)
- Mingyu Yu
- Department of Materials Science and Engineering, University of Delaware, 201 Dupont Hall, 127 The Green, Newark, Delaware 19716, United States
| | - Sahani Amaya Iddawela
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Jiayang Wang
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Maria Hilse
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- 2D Crystal Consortium Materials Innovation Platform, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Jessica L Thompson
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Danielle Reifsnyder Hickey
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Susan B Sinnott
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Institute for Computational and Data Science, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Penn State Institute of Energy and the Environment, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Stephanie Law
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- 2D Crystal Consortium Materials Innovation Platform, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Penn State Institute of Energy and the Environment, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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2
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Kim Y, Lee CS, Son S, Shin KW, Byun KE, Shin HJ, Lee Z, Shin HJ. Spiral-Driven Vertical Conductivity in Nanocrystalline Graphene. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2308176. [PMID: 37803430 DOI: 10.1002/smll.202308176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Indexed: 10/08/2023]
Abstract
The structure of graphene grown in chemical vapor deposition (CVD) is sensitive to the growth condition, particularly the substrate. The conventional growth of high-quality graphene via the Cu-catalyzed cracking of hydrocarbon species has been extensively studied; however, the direct growth on noncatalytic substrates, for practical applications of graphene such as current Si technologies, remains unexplored. In this study, nanocrystalline graphene (nc-G) spirals are produced on noncatalytic substrates by inductively coupled plasma CVD. The enhanced out-of-plane electrical conductivity is achieved by a spiral-driven continuous current pathway from bottom to top layer. Furthermore, some neighboring nc-G spirals exhibit a homogeneous electrical conductance, which is not common for stacked graphene structure. Klein-edge structure developed at the edge of nc-Gs, which can easily form covalent bonding, is thought to be responsible for the uniform conductance of nc-G aggregates. These results have important implications for practical applications of graphene with vertical conductivity realized through spiral structure.
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Affiliation(s)
- Yohan Kim
- Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), 44919, Ulsan, Republic of Korea
| | - Chang-Seok Lee
- Device Research Center, Samsung Advanced Institute of Technology, 443-801, Suwon, Republic of Korea
| | - Seungwoo Son
- Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), 44919, Ulsan, Republic of Korea
| | - Keun Wook Shin
- Device Research Center, Samsung Advanced Institute of Technology, 443-801, Suwon, Republic of Korea
| | - Kyung-Eun Byun
- Device Research Center, Samsung Advanced Institute of Technology, 443-801, Suwon, Republic of Korea
| | - Hyeon-Jin Shin
- Device Research Center, Samsung Advanced Institute of Technology, 443-801, Suwon, Republic of Korea
| | - Zonghoon Lee
- Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), 44919, Ulsan, Republic of Korea
| | - Hyung-Joon Shin
- Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), 44919, Ulsan, Republic of Korea
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3
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Redkov A. Spiral growth of multicomponent crystals: theoretical aspects. Front Chem 2023; 11:1189729. [PMID: 37252372 PMCID: PMC10213516 DOI: 10.3389/fchem.2023.1189729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2023] [Accepted: 04/28/2023] [Indexed: 05/31/2023] Open
Abstract
This paper presents recent advances in the theory of multicomponent crystal growth from gas or solution, focusing on the most common step-flow mechanisms: Burton-Cabrera-Frank, Chernov, and Gilmer-Ghez-Cabrera. Analytical expressions for the spiral crystal growth rate are presented, taking into account the properties of all species involved in the growth process. The paper also outlines theoretical approaches to consider these mechanisms in multicomponent systems, providing a foundation for future developments and exploration of previously unexplored effects. Some special cases are discussed, including the formation of nanoislands of pure components on the surface and their self-organization, the impact of applied mechanical stress on the growth rate, and the mechanisms of its influence on growth kinetics. The growth due to chemical reactions on the surface is also considered. Possible future directions for developing the theory are outlined. A brief overview of numerical approaches and software codes that are useful in theoretical studies of crystal growth is also given.
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Wang X, Zhou H, Bai L, Wang HQ. Growth, structure, and morphology of van der Waals epitaxy Cr 1+δTe 2 films. NANOSCALE RESEARCH LETTERS 2023; 18:23. [PMID: 36826603 DOI: 10.1186/s11671-023-03791-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2022] [Accepted: 02/07/2023] [Indexed: 05/24/2023]
Abstract
The preparation of two-dimensional magnetic materials is a key process to their applications and the study of their structure and morphology plays an important role in the growth of high-quality thin films. Here, the growth, structure, and morphology of Cr1+δTe2 films grown by molecular beam epitaxy on mica with variations of Te/Cr flux ratio, growth temperature, and film thickness have been systematically investigated by scanning tunneling microscopy, reflection high-energy electron diffraction, scanning electron microscope, and X-ray photoelectron spectroscopy. We find that a structural change from multiple phases to a single phase occurs with the increase in growth temperature, irrespective of the Cr/Te flux ratios, which is attributed to the desorption difference of Te atoms at different temperatures, and that the surface morphology of the films grown at relatively high growth temperatures (≥ 300 °C) exhibits a quasi-hexagonal mesh-like structure, which consists of nano-islands with bending surface induced by the screw dislocations, as well as that the films would undergo a growth-mode change from 2D at the initial stage in a small film thickness (2 nm) to 3D at the later stage in thick thicknesses (12 nm and 24 nm). This work provides a general model for the study of pseudo-layered materials grown on flexible layered substrates.
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Affiliation(s)
- Xiaodan Wang
- Engineering Research Center of Micro-Nano Optoelectronic Materials and Devices, Ministry of Education; Fujian Key Laboratory of Semiconductor Materials and Applications, CI Center for OSED, and Department of Physics, Xiamen University, Xiamen, 361005, People's Republic of China
- School of Physics, Shandong University, Jinan, 250100, People's Republic of China
| | - Hua Zhou
- School of Physics, Shandong University, Jinan, 250100, People's Republic of China.
| | - Lihui Bai
- School of Physics, Shandong University, Jinan, 250100, People's Republic of China
| | - Hui-Qiong Wang
- Engineering Research Center of Micro-Nano Optoelectronic Materials and Devices, Ministry of Education; Fujian Key Laboratory of Semiconductor Materials and Applications, CI Center for OSED, and Department of Physics, Xiamen University, Xiamen, 361005, People's Republic of China.
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5
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Yi R, Wang J, Yue X, Liang Y, Li Z, Sheng H, Guan M, Zhu Y, Sun Q, Wang L, Huang X, Lu G. Synthesis of Thin Bi 9 O 7.5 S 6 Nanosheets for Improved Photodetection in a Wide Wavelength Range. Chem Asian J 2021; 16:3748-3753. [PMID: 34549536 DOI: 10.1002/asia.202100963] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 09/17/2021] [Indexed: 12/30/2022]
Abstract
Bismuth-based compounds possess layered structures with a variety of stacking modes, endowing the compounds with diverse properties. As one type of bismuth oxysulfides, Bi9 O7.5 S6 nanocrystals has great applications in photodetection; however, the responsivity of bulky Bi9 O7.5 S6 is limited due to the poor charge separation. Herein, single-crystalline Bi9 O7.5 S6 thin nanosheets are successfully synthesized by using a solvothermal method. The thickness of the obtained Bi9 O7.5 S6 nanosheets is down to 15 nm and can be easily tuned by varying the reaction period. Moreover, the Bi9 O7.5 S6 nanosheets show strong light absorption in the visible and near infrared range, making it a promising candidate in optoelectronics. As a demonstration, the thin Bi9 O7.5 S6 nanosheets are used as active layer in an optoelectronic device, which exhibits sensitive photoelectric response to light in a wide range of 400-800 nm. The responsivity of the device reaches up to 1140 μA W-1 , and the performance of the device is stable after long-period illumination. This work demonstrates a great potential of the thin Bi9 O7.5 S6 nanosheets in optoelectronic devices, and these nanosheets may also be extended to various optoelectronic applications.
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Affiliation(s)
- Ronghua Yi
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, P. R. China
| | - Jin Wang
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, P. R. China
| | - Xiaoping Yue
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, P. R. China
| | - Yan Liang
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, P. R. China
| | - Zhuoyao Li
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, P. R. China
| | - Huixiang Sheng
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, P. R. China
| | - Mengdan Guan
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, P. R. China
| | - Yameng Zhu
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, P. R. China
| | - Qizeng Sun
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, P. R. China
| | - Li Wang
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, P. R. China
| | - Xiao Huang
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, P. R. China
| | - Gang Lu
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, 211816, P. R. China.,National Laboratory of Solid State Microstructures, Nanjing University, Nanjing, 210093, P. R. China
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6
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Diep NQ, Wu SK, Liu CW, Huynh SH, Chou WC, Lin CM, Zhang DZ, Ho CH. Pressure induced structural phase crossover of a GaSe epilayer grown under screw dislocation driven mode and its phase recovery. Sci Rep 2021; 11:19887. [PMID: 34615957 PMCID: PMC8494905 DOI: 10.1038/s41598-021-99419-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 09/09/2021] [Indexed: 02/08/2023] Open
Abstract
Hydrostatically pressurized studies using diamond anvil cells on the structural phase transition of the free-standing screw-dislocation-driven (SDD) GaSe thin film synthesized by molecular beam epitaxy have been demonstrated via in-situ angle-dispersive synchrotron X-ray diffraction and Raman spectroscopy. The early pressure-driven hexagonal-to-rock salt transition at approximately ~ 20 GPa as well as the outstandingly structural-phase memory after depressurization in the SDD-GaSe film was recognized, attributed to the screw dislocation-assisted mechanism. Note that, the reversible pressure-induced structural transition was not evidenced from the GaSe bulk, which has a layer-by-layer stacking structure. In addition, a remarkable 1.7 times higher in bulk modulus of the SDD-GaSe film in comparison to bulk counterpart was observed, which was mainly contributed by its four times higher in the incompressibility along c-axis. This is well-correlated to the slower shifting slopes of out-of-plane phonon-vibration modes in the SDD-GaSe film, especially at low-pressure range (< 5 GPa). As a final point, we recommend that the intense density of screw dislocation cores in the SDD-GaSe lattice structure plays a crucial role in these novel phenomena.
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Affiliation(s)
- Nhu Quynh Diep
- Department of Electrophysics, College of Sciences, National Yang-Ming Chiao-Tung University, Hsinchu, 30010, Taiwan
| | - Ssu Kuan Wu
- Department of Electrophysics, College of Sciences, National Yang-Ming Chiao-Tung University, Hsinchu, 30010, Taiwan
| | - Cheng Wei Liu
- Department of Electrophysics, College of Sciences, National Yang-Ming Chiao-Tung University, Hsinchu, 30010, Taiwan
| | - Sa Hoang Huynh
- Department of Electrophysics, College of Sciences, National Yang-Ming Chiao-Tung University, Hsinchu, 30010, Taiwan.
| | - Wu Ching Chou
- Department of Electrophysics, College of Sciences, National Yang-Ming Chiao-Tung University, Hsinchu, 30010, Taiwan.
| | - Chih Ming Lin
- Department of Physics, College of Sciences, National Tsing Hua University, Hsinchu, 300044, Taiwan.
| | - Dong Zhou Zhang
- GeoSoilEnviroCARS, Argonne National Laboratory, 9700 S Cass Ave, Lemont, 60439, IL, USA
| | - Ching Hwa Ho
- Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei, 106, Taiwan
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7
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Zhao Y, Kong X, Shearer MJ, Ding F, Jin S. Chemical Etching of Screw Dislocated Transition Metal Dichalcogenides. NANO LETTERS 2021; 21:7815-7822. [PMID: 34491064 DOI: 10.1021/acs.nanolett.1c02799] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Chemical etching can create novel structures inaccessible by growth and provide complementary understanding on the growth mechanisms of complex nanostructures. Screw dislocation-driven growth influences the layer stackings of transition metal dichalcogenides (MX2) resulting in complex spiral morphologies. Herein, we experimentally and theoretically study the etching of screw dislocated WS2 and WSe2 nanostructures using H2O2 etchant. The kinetic Wulff constructions and Monte Carlo simulations establish the etching principles of single MX2 layers. Atomic force microscopy characterization reveals diverse etching morphology evolution behaviors around the dislocation cores and along the exterior edges, including triangular, hexagonal, or truncated hexagonal holes and smooth or rough edges. These behaviors are influenced by the edge orientations, layer stackings, and the strain of screw dislocations. Ab initio calculation and kinetic Monte Carlo simulations support the experimental observations and provide further mechanistic insights. This knowledge can help one to understand more complex structures created by screw dislocations through etching.
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Affiliation(s)
- Yuzhou Zhao
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Xiao Kong
- Centre for Multidimensional Carbon Materials, Institute for Basic Science, Ulsan 44919, Korea
| | - Melinda J Shearer
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Feng Ding
- Centre for Multidimensional Carbon Materials, Institute for Basic Science, Ulsan 44919, Korea
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan 44919, Korea
| | - Song Jin
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
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8
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Dong J, Zhang L, Wu B, Ding F, Liu Y. Theoretical Study of Chemical Vapor Deposition Synthesis of Graphene and Beyond: Challenges and Perspectives. J Phys Chem Lett 2021; 12:7942-7963. [PMID: 34387496 DOI: 10.1021/acs.jpclett.1c02316] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Two-dimensional (2D) materials have attracted great attention in recent years because of their unique dimensionality and related properties. Chemical vapor deposition (CVD), a crucial technique for thin-film epitaxial growth, has become the most promising method of synthesizing 2D materials. Different from traditional thin-film growth, where strong chemical bonds are involved in both thin films and substrates, the interaction in 2D materials and substrates involves the van der Waals force and is highly anisotropic, and therefore, traditional thin-film growth theories cannot be applied to 2D material CVD synthesis. During the last 15 years, extensive theoretical studies were devoted to the CVD synthesis of 2D materials. This Perspective attempts to present a theoretical framework for 2D material CVD synthesis as well as the challenges and opportunities in exploring CVD mechanisms. We hope that this Perspective can provide an in-depth understanding of 2D material CVD synthesis and can further stimulate 2D material synthesis.
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Affiliation(s)
- Jichen Dong
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P.R. China
- University of Chinese Academy of Sciences, Beijing 100049, P.R. China
| | - Leining Zhang
- Centre for Multidimensional Carbon Materials, Institute for Basic Science, Ulsan 44919, South Korea
| | - Bin Wu
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P.R. China
- University of Chinese Academy of Sciences, Beijing 100049, P.R. China
| | - Feng Ding
- Centre for Multidimensional Carbon Materials, Institute for Basic Science, Ulsan 44919, South Korea
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan 44919, South Korea
| | - Yunqi Liu
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P.R. China
- University of Chinese Academy of Sciences, Beijing 100049, P.R. China
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9
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Yu Y, Jung GS, Liu C, Lin YC, Rouleau CM, Yoon M, Eres G, Duscher G, Xiao K, Irle S, Puretzky AA, Geohegan DB. Strain-Induced Growth of Twisted Bilayers during the Coalescence of Monolayer MoS 2 Crystals. ACS NANO 2021; 15:4504-4517. [PMID: 33651582 DOI: 10.1021/acsnano.0c08516] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Tailoring the grain boundaries (GBs) and twist angles between two-dimensional (2D) crystals are two crucial synthetic challenges to deterministically enable envisioned applications such as moiré excitons, emerging magnetism, or single-photon emission. Here, we reveal how twisted 2D bilayers can be synthesized from the collision and coalescence of two growing monolayer MoS2 crystals during chemical vapor deposition. The twisted bilayer (TB) moiré angles are found to preserve the misorientation angle (θ) of the colliding crystals. The shapes of the TB regions are rationalized by a kink propagation model that predicts the GB formed by the coalescing crystals. Optical spectroscopy measurements reveal a θ-dependent long-range strain in crystals with stitched grain boundaries and a sharp (θ > 20°) threshold for the appearance of TBs, which relieves this strain. Reactive molecular dynamics simulations explain this strain from the continued growth of the crystals during coalescence due to the insertion of atoms at unsaturated defects along the GB, a process that self-terminates when the defects become saturated. The simulations also reproduce atomic-resolution electron microscopy observations of faceting along the GB, which is shown to arise from the growth-induced long-range strain. These facets align with the axes of the colliding crystals to provide favorable nucleation sites for second-layer growth of a TB with twist angles that preserve the misorientation angle θ. This interplay between strain generation and aligned nucleation provides a synthetic pathway for the growth of TBs with deterministic angles.
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Affiliation(s)
- Yiling Yu
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Gang Seob Jung
- Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Chenze Liu
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Yu-Chuan Lin
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Christopher M Rouleau
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Mina Yoon
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Gyula Eres
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Gerd Duscher
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Kai Xiao
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Stephan Irle
- Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Alexander A Puretzky
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - David B Geohegan
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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10
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Zhao Y, Zhang C, Kohler DD, Scheeler JM, Wright JC, Voyles PM, Jin S. Supertwisted spirals of layered materials enabled by growth on non-Euclidean surfaces. Science 2020; 370:442-445. [DOI: 10.1126/science.abc4284] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Accepted: 09/02/2020] [Indexed: 11/02/2022]
Affiliation(s)
- Yuzhou Zhao
- Department of Chemistry, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - Chenyu Zhang
- Department of Materials Science and Engineering, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - Daniel D. Kohler
- Department of Chemistry, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - Jason M. Scheeler
- Department of Chemistry, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - John C. Wright
- Department of Chemistry, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - Paul M. Voyles
- Department of Materials Science and Engineering, University of Wisconsin–Madison, Madison, WI 53706, USA
| | - Song Jin
- Department of Chemistry, University of Wisconsin–Madison, Madison, WI 53706, USA
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11
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Molecular Beam Epitaxy of Layered Group III Metal Chalcogenides on GaAs(001) Substrates. MATERIALS 2020; 13:ma13163447. [PMID: 32764315 PMCID: PMC7475857 DOI: 10.3390/ma13163447] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 07/27/2020] [Accepted: 07/30/2020] [Indexed: 11/17/2022]
Abstract
Development of molecular beam epitaxy (MBE) of two-dimensional (2D) layered materials is an inevitable step in realizing novel devices based on 2D materials and heterostructures. However, due to existence of numerous polytypes and occurrence of additional phases, the synthesis of 2D films remains a difficult task. This paper reports on MBE growth of GaSe, InSe, and GaTe layers and related heterostructures on GaAs(001) substrates by using a Se valve cracking cell and group III metal effusion cells. The sophisticated self-consistent analysis of X-ray diffraction, transmission electron microscopy, and Raman spectroscopy data was used to establish the correlation between growth conditions, formed polytypes and additional phases, surface morphology and crystalline structure of the III–VI 2D layers. The photoluminescence and Raman spectra of the grown films are discussed in detail to confirm or correct the structural findings. The requirement of a high growth temperature for the fabrication of optically active 2D layers was confirmed for all materials. However, this also facilitated the strong diffusion of group III metals in III–VI and III–VI/II–VI heterostructures. In particular, the strong In diffusion into the underlying ZnSe layers was observed in ZnSe/InSe/ZnSe quantum well structures, and the Ga diffusion into the top InSe layer grown at ~450 °C was confirmed by the Raman data in the InSe/GaSe heterostructures. The results on fabrication of the GaSe/GaTe quantum well structures are presented as well, although the choice of optimum growth temperatures to make them optically active is still a challenge.
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12
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Diep NQ, Liu CW, Wu SK, Chou WC, Huynh SH, Chang EY. Screw-Dislocation-Driven Growth Mode in Two Dimensional GaSe on GaAs(001) Substrates Grown by Molecular Beam Epitaxy. Sci Rep 2019; 9:17781. [PMID: 31780756 PMCID: PMC6883029 DOI: 10.1038/s41598-019-54406-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Accepted: 11/13/2019] [Indexed: 11/30/2022] Open
Abstract
Regardless of the dissimilarity in the crystal symmetry, the two-dimensional GaSe materials grown on GaAs(001) substrates by molecular beam epitaxy reveal a screw-dislocation-driven growth mechanism. The spiral-pyramidal structure of GaSe multi-layers was typically observed with the majority in ε-phase. Comprehensive investigations on temperature-dependent photoluminescence, Raman scattering, and X-ray diffraction indicated that the structure has been suffered an amount of strain, resulted from the screw-dislocation-driven growth mechanism as well as the stacking disorders between monolayer at the boundaries of the GaSe nanoflakes. In addition, Raman spectra under various wavelength laser excitations explored that the common ε-phase of 2D GaSe grown directly on GaAs can be transformed into the β-phase by introducing a Se-pretreatment period at the initial growth process. This work provides an understanding of molecular beam epitaxy growth of 2D materials on three-dimensional substrates and paves the way to realize future electronic and optoelectronic heterogeneous integrated technology as well as second harmonic generation applications.
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Affiliation(s)
- Nhu Quynh Diep
- Department of Electrophysics, College of Sciences, National Chiao Tung University, 1001 University Road, Hsinchu, 30010, Taiwan, R.O.C
| | - Cheng-Wei Liu
- Department of Electrophysics, College of Sciences, National Chiao Tung University, 1001 University Road, Hsinchu, 30010, Taiwan, R.O.C
| | - Ssu-Kuan Wu
- Department of Electrophysics, College of Sciences, National Chiao Tung University, 1001 University Road, Hsinchu, 30010, Taiwan, R.O.C
| | - Wu-Ching Chou
- Department of Electrophysics, College of Sciences, National Chiao Tung University, 1001 University Road, Hsinchu, 30010, Taiwan, R.O.C..
| | - Sa Hoang Huynh
- Department of Materials Science and Engineering, College of Engineering, National Chiao Tung University, 1001 University Road, Hsinchu, 30010, Taiwan, R.O.C.,School of Physics and Astronomy, Cardiff University, Cardiff, CF24 3AA, United Kingdom
| | - Edward Yi Chang
- Department of Materials Science and Engineering, College of Engineering, National Chiao Tung University, 1001 University Road, Hsinchu, 30010, Taiwan, R.O.C.,International College of Semiconductor Technology, National Chiao Tung University, 1001 University Road, Hsinchu, 30010, Taiwan, R.O.C
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