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Sun X, Lu Z, Lu Y. Enhanced interactions of excitonic complexes in free-standing WS 2. NANOSCALE 2023. [PMID: 37937449 DOI: 10.1039/d3nr04594c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2023]
Abstract
Excitonic complexes, bound states of electrons and holes, provide a promising platform in monolayer transition-metal dichalcogenide (TMDC) semiconductors for investigating diverse many-body interaction phenomena. The surrounding dielectric environment has been found to strongly influence the excitonic properties of the TMDC monolayers. While the impact of different dielectric surroundings on two-dimensional semiconductor materials and their strong correlations have been well studied, the effects on exciton formation and its properties resulting from a further reduction in dielectric screening remain elusive. In this study, we examined free-standing tungsten disulfide (WS2) monolayers, where the efficient generation of higher-order correlated excitonic complexes is readily observed. This phenomenon arises from the effective mutual interactions among excitons and internal carriers, attributed to the modulated exciton dynamics generated by the further reduced dielectric screening effect in the freestanding structure. The formation efficiency of excitonic complexes is enhanced and the multiple biexciton species (five particles such as charged biexcitons and acceptor/donor-bound biexcitons) are successfully induced under low excitation intensity and moderate temperature conditions. Our findings offer valuable insights into the influence of the dielectric environment on exciton interactions and enable a productive avenue for exploring fundamental many-body interactions, providing new possibilities for dielectric engineering of atomic thin semiconductors.
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Affiliation(s)
- Xueqian Sun
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, ACT, 2601, Australia
| | - Zhuoyuan Lu
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, ACT, 2601, Australia
| | - Yuerui Lu
- School of Engineering, College of Engineering and Computer Science, the Australian National University, Canberra, ACT, 2601, Australia
- Australian Research Council Centre of Excellence for Quantum Computation and Communication Technology, the Australian National University, Canberra, ACT, 2601, Australia.
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2
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Darman P, Yaghoobi A, Darbari S. Pinhole-free 2D Ruddlesden-Popper perovskite layer with close packed large crystalline grains, suitable for optoelectronic applications. Sci Rep 2023; 13:8374. [PMID: 37225784 DOI: 10.1038/s41598-023-35546-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2023] [Accepted: 05/19/2023] [Indexed: 05/26/2023] Open
Abstract
Here, we achieved pinhole-free 2D Ruddlesden-Popper Perovskite (RPP) BA2PbI4 layers with close packed crystalline grains with dimension of about 30 × 30 µm2, which have been demonstrated to be favorable for optoelectronic applications, such as fast response RPP-based metal/semiconductor/metal photodetectors. We explored affecting parameters in hot casting of BA2PbI4 layers, and proved that oxygen plasma treatment prior to hot casting plays a significant role to achieve high quality close packed polycrystalline RPP layers at lower hot cast temperatures. Moreover, we demonstrate that crystal growth of 2D BA2PbI4 can be dominantly controlled by the rate of solvent evaporation through substrate temperature or rotational speed, while molarity of the prepared RPP/DMF precursor is the dominant factor that determines the RPP layer thickness, and can affect the spectral response of the realized photodetector. Benefiting from the high light absorption and inherent chemical stability of 2D RPP layers, we achieved high responsivity and stability, and fast response photodetection from perovskite active layer. We achieved a fast photoresponse with rise and fall times of 189 µs and 300 µs, and the maximum responsivity of 119 mA/W and detectivity of 2.15 × 108 Jones in response to illumination wavelength of 450 nm. The presented polycrystalline RPP-based photodetector benefits from a simple and low-cost fabrication process, suitable for large area production on glass substrate, a good stability and responsivity, and a promising fast photoresponse, even around that of exfoliated single crystal RPP-based counterparts. However, it is well known that exfoliation methods suffer from poor repeatability and scalability, which make them incompatible with mass production and large area applications.
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Affiliation(s)
- Parsa Darman
- Nano-Sensors and Detectors Lab., and Nano Plasmo-Photonic Research Group, Faculty of Electrical and Computer Engineering, Tarbiat Modares University, Tehran, Iran
| | - Amin Yaghoobi
- Nano-Sensors and Detectors Lab., and Nano Plasmo-Photonic Research Group, Faculty of Electrical and Computer Engineering, Tarbiat Modares University, Tehran, Iran
| | - Sara Darbari
- Nano-Sensors and Detectors Lab., and Nano Plasmo-Photonic Research Group, Faculty of Electrical and Computer Engineering, Tarbiat Modares University, Tehran, Iran.
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3
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Exciton polariton interactions in Van der Waals superlattices at room temperature. Nat Commun 2023; 14:1512. [PMID: 36932078 PMCID: PMC10023709 DOI: 10.1038/s41467-023-36912-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Accepted: 02/23/2023] [Indexed: 03/19/2023] Open
Abstract
Monolayer transition-metal dichalcogenide (TMD) materials have attracted a great attention because of their unique properties and promising applications in integrated optoelectronic devices. Being layered materials, they can be stacked vertically to fabricate artificial van der Waals lattices, which offer unique opportunities to tailor the electronic and optical properties. The integration of TMD heterostructures in planar microcavities working in strong coupling regime is particularly important to control the light-matter interactions and form robust polaritons, highly sought for room temperature applications. Here, we demonstrate the systematic control of the coupling-strength by embedding multiple WS2 monolayers in a planar microcavity. The vacuum Rabi splitting is enhanced from 36 meV for one monolayer up to 72 meV for the four-monolayer microcavity. In addition, carrying out time-resolved pump-probe experiments at room temperature we demonstrate the nature of polariton interactions which are dominated by phase space filling effects. Furthermore, we also observe the presence of long-living dark excitations in the multiple monolayer superlattices. Our results pave the way for the realization of polaritonic devices based on planar microcavities embedding multiple monolayers and could potentially lead the way for future devices towards the exploitation of interaction-driven phenomena at room temperature.
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Xing F, Ji G, Li Z, Zhong W, Wang F, Liu Z, Xin W, Tian J. Preparation, properties and applications of two-dimensional superlattices. MATERIALS HORIZONS 2023; 10:722-744. [PMID: 36562255 DOI: 10.1039/d2mh01206e] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
As a combination concept of a 2D material and a superlattice, two-dimensional superlattices (2DSs) have attracted increasing attention recently. The natural advantages of 2D materials in their properties, dimension, diversity and compatibility, and their gradually improved technologies for preparation and device fabrication serve as solid foundations for the development of 2DSs. Compared with the existing 2D materials and even their heterostructures, 2DSs relate to more materials and elaborate architectures, leading to novel systems with more degrees of freedom to modulate material properties at the nanoscale. Here, three typical types of 2DSs, including the component, strain-induced and moiré superlattices, are reviewed. The preparation methods, properties and state-of-the-art applications of each type are summarized. An outlook of the challenges and future developments is also presented. We hope that this work can provide a reference for the development of 2DS-related research.
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Affiliation(s)
- Fei Xing
- School of Physics and Optoelectronic Engineering, Shandong University of Technology, Zibo, 255049, China
| | - Guangmin Ji
- School of Physics and Optoelectronic Engineering, Shandong University of Technology, Zibo, 255049, China
| | - Zongwen Li
- School of Physics and Optoelectronic Engineering, Shandong University of Technology, Zibo, 255049, China
| | - Weiheng Zhong
- Key Laboratory of UV-Emitting Materials and Technology, Ministry of Education, Northeast Normal University, Changchun, 130024, China.
| | - Feiyue Wang
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou, 510275, China
| | - Zhibo Liu
- Key Laboratory of Weak Light Nonlinear Photonics, Ministry of Education, Teda Applied Physics Institute and School of Physics, Nankai University, Tianjin, 300071, China.
| | - Wei Xin
- Key Laboratory of UV-Emitting Materials and Technology, Ministry of Education, Northeast Normal University, Changchun, 130024, China.
| | - Jianguo Tian
- Key Laboratory of Weak Light Nonlinear Photonics, Ministry of Education, Teda Applied Physics Institute and School of Physics, Nankai University, Tianjin, 300071, China.
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Zimmerman M, Rapaport R, Gazit S. Collective interlayer pairing and pair superfluidity in vertically stacked layers of dipolar excitons. Proc Natl Acad Sci U S A 2022; 119:e2205845119. [PMID: 35858431 PMCID: PMC9335227 DOI: 10.1073/pnas.2205845119] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Accepted: 06/06/2022] [Indexed: 01/21/2023] Open
Abstract
Layered bosonic dipolar fluids have been suggested to host a condensate of interlayer molecular bound states. However, experimental observation has remained elusive. Motivated by two recent experimental works [C. Hubert et al., Phys. Rev. X9, 021026 (2019) and D. J. Choksy et al., Phys. Rev. B 103, 045126 (2021)], we theoretically study, using numerically exact quantum Monte Carlo calculations, the experimental signatures of collective interlayer pairing in vertically stacked indirect exciton (IX) layers. We find that IX energy shifts associated with each layer evolve nontrivially as a function of density imbalance following a nonmonotonic trend with a jump discontinuity at density balance, identified with the interlayer IX molecule gap. This behavior discriminates between the superfluidity of interlayer bound pairs and independent dipole condensation in distinct layers. Considering finite temperature and finite density imbalance conditions, we find a cascade of Berezinskii-Kosterlitz-Thouless (BKT) transitions, initially into a pair superfluid and only then, at lower temperatures, into complete superfluidity of both layers. Our results may provide a theoretical interpretation of existing experimental observations in GaAs double quantum well (DQW) bilayer structures. Furthermore, to optimize the visibility of pairing dynamics in future studies, we present an analysis suggesting realistic experimental settings in GaAs and transition metal dichalcogenide (TMD) bilayer DQW heterostructures where collective interlayer pairing and pair superfluidity can be clearly observed.
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Affiliation(s)
- Michal Zimmerman
- The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
| | - Ronen Rapaport
- The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
| | - Snir Gazit
- The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
- The Fritz Haber Research Center for Molecular Dynamics, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
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Wu W, Li D, Xu Y, Zeng XC. Two-Dimensional GeC 2 with Tunable Electronic and Carrier Transport Properties and a High Current ON/OFF Ratio. J Phys Chem Lett 2021; 12:11488-11496. [PMID: 34793176 DOI: 10.1021/acs.jpclett.1c03477] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
In this study, we present that 2D tetrahex-GeC2 materials possess novel electronic and carrier transport properties based on density functional theory computations combined with the nonequilibrium Green's function method. We show that under the 4% (-4%) in-plane expansion (compression) along the a-direction (b-direction) of the tetrahex-GeC2 monolayer, the bandgap can be enlarged to a desirable 1.26 eV (1.32 eV), close to that of silicon. The carrier transport properties of both the sub-10 nm tetrahex-GeC2 monolayer and the bilayer show strong anisotropy within the bias from -1 to 1 V. The current ON (a-direction)/OFF (b-direction) ratio amounts to 105 for the tetrahex-GeC2 monolayer. A striking negative differential conductance arises with the maximum Ipeak/Ivalley on the order of 104 under the 4% uniaxial expansion along the b-direction of the tetrahex-GeC2 monolayer. Overall, the 2D tetrahex-GeC2 monolayer and bilayer possess highly tunable electronic and carrier transport properties under uniaxial strain, which can be exploited for potential applications in nanoelectronics.
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Affiliation(s)
- Wenjun Wu
- School of Microelectronics and Control Engineering, Changzhou University, Changzhou 213164, Jiangsu China
| | - Dongze Li
- School of Microelectronics and Control Engineering, Changzhou University, Changzhou 213164, Jiangsu China
| | - Yuehua Xu
- School of Microelectronics and Control Engineering, Changzhou University, Changzhou 213164, Jiangsu China
| | - Xiao Cheng Zeng
- Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
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Grzeszczyk M, Olkowska-Pucko K, Nogajewski K, Watanabe K, Taniguchi T, Kossacki P, Babiński A, Molas MR. Exposing the trion's fine structure by controlling the carrier concentration in hBN-encapsulated MoS 2. NANOSCALE 2021; 13:18726-18733. [PMID: 34739017 DOI: 10.1039/d1nr03855a] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Atomically thin materials, like semiconducting transition metal dichalcogenides, are highly sensitive to the environment. This opens up an opportunity to externally control their properties by changing their surroundings. In this work, high-quality van der Waals heterostructures assembled from hBN-encapsulated monolayer MoS2 are studied with the aid of photoluminescence, photoluminescence excitation, and reflectance contrast experiments. We demonstrate that carrier concentration in MoS2 monolayers, arising from charge transfer from impurities in the substrate, can be significantly tuned within one order of magnitude by the modification of the bottom hBN flake thickness. The studied structures, characterized by spectral lines with linewidths approaching the narrow homogeneously broadened limit enabled observations of subtle optical and spin-valley properties of excitonic complexes. Our results allowed us to resolve three optically-active negatively charged excitons in MoS2 monolayers, which are assigned to the intravalley singlet, intervalley singlet, and intervalley triplet states.
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Affiliation(s)
- Magdalena Grzeszczyk
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-093 Warsaw, Poland.
| | - Katarzyna Olkowska-Pucko
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-093 Warsaw, Poland.
| | - Karol Nogajewski
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-093 Warsaw, Poland.
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 305-0044, Japan
| | - Piotr Kossacki
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-093 Warsaw, Poland.
| | - Adam Babiński
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-093 Warsaw, Poland.
| | - Maciej R Molas
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, 02-093 Warsaw, Poland.
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