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Chen S, Zhang Y, King WP, Bashir R, van der Zande AM. Edge-Passivated Monolayer WSe 2 Nanoribbon Transistors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2313694. [PMID: 39023387 PMCID: PMC11436303 DOI: 10.1002/adma.202313694] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Revised: 07/06/2024] [Indexed: 07/20/2024]
Abstract
The ongoing reduction in transistor sizes drives advancements in information technology. However, as transistors shrink to the nanometer scale, surface and edge states begin to constrain their performance. 2D semiconductors like transition metal dichalcogenides (TMDs) have dangling-bond-free surfaces, hence achieving minimal surface states. Nonetheless, edge state disorder still limits the performance of width-scaled 2D transistors. This work demonstrates a facile edge passivation method to enhance the electrical properties of monolayer WSe2 nanoribbons, by combining scanning transmission electron microscopy, optical spectroscopy, and field-effect transistor (FET) transport measurements. Monolayer WSe2 nanoribbons are passivated with amorphous WOxSey at the edges, which is achieved using nanolithography and a controlled remote O2 plasma process. The same nanoribbons, with and without edge passivation are sequentially fabricated and measured. The passivated-edge nanoribbon FETs exhibit 10 ± 6 times higher field-effect mobility than the open-edge nanoribbon FETs, which are characterized with dangling bonds at the edges. WOxSey edge passivation minimizes edge disorder and enhances the material quality of WSe2 nanoribbons. Owing to its simplicity and effectiveness, oxidation-based edge passivation could become a turnkey manufacturing solution for TMD nanoribbons in beyond-silicon electronics and optoelectronics.
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Affiliation(s)
- Sihan Chen
- Holonyak Micro and Nanotechnology Laboratory, University of Illinois Urbana-Champaign, Urbana, IL, 61801, USA
| | - Yue Zhang
- Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, IL, 61801, USA
| | - William P King
- Holonyak Micro and Nanotechnology Laboratory, University of Illinois Urbana-Champaign, Urbana, IL, 61801, USA
- Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, IL, 61801, USA
- Materials Research Laboratory, University of Illinois Urbana-Champaign, Urbana, IL, 61801, USA
| | - Rashid Bashir
- Holonyak Micro and Nanotechnology Laboratory, University of Illinois Urbana-Champaign, Urbana, IL, 61801, USA
- Department of Bioengineering, University of Illinois Urbana-Champaign, Urbana, IL, 61801, USA
| | - Arend M van der Zande
- Holonyak Micro and Nanotechnology Laboratory, University of Illinois Urbana-Champaign, Urbana, IL, 61801, USA
- Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, IL, 61801, USA
- Materials Research Laboratory, University of Illinois Urbana-Champaign, Urbana, IL, 61801, USA
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Fukui T, Nishimura T, Miyata Y, Ueno K, Taniguchi T, Watanabe K, Nagashio K. Single-Gate MoS 2 Tunnel FET with a Thickness-Modulated Homojunction. ACS APPLIED MATERIALS & INTERFACES 2024; 16:8993-9001. [PMID: 38324211 DOI: 10.1021/acsami.3c15535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2024]
Abstract
Two-dimensional (2D) materials stand as a promising platform for tunnel field-effect transistors (TFETs) in the pursuit of low-power electronics for the Internet of Things era. This promise arises from their dangling bond-free van der Waals heterointerface. Nevertheless, the attainment of high device performance is markedly impeded by the requirement of precise control over the 2D assembly with multiple stacks of different layers. In this study, we addressed a thickness-modulated n/p+-homojunction prepared from Nb-doped p+-MoS2 crystal, where the issue on interface traps can be neglected without any external interface control due to the homojunction. Notably, our observations reveal the existence of a negative differential resistance, even at room temperature (RT). This signifies the successful realization of TFET operation under type III band alignment conditions by a single gate at RT, suggesting that the dominant current mechanism is band-to-band tunneling due to the ideal interface.
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Affiliation(s)
- Tomohiro Fukui
- Department of Materials Engineering, The University of Tokyo, Tokyo 113-8656, Japan
| | - Tomonori Nishimura
- Department of Materials Engineering, The University of Tokyo, Tokyo 113-8656, Japan
| | - Yasumitsu Miyata
- Department of Physics, Tokyo Metropolitan University, Hachioji 192-0397, Japan
| | - Keiji Ueno
- Department of Chemistry, Saitama University, Saitama 338-8570, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, Ibaraki 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, Ibaraki 305-0044, Japan
| | - Kosuke Nagashio
- Department of Materials Engineering, The University of Tokyo, Tokyo 113-8656, Japan
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Huynh T, Ngo TD, Choi H, Choi M, Lee W, Nguyen TD, Tran TT, Lee K, Hwang JY, Kim J, Yoo WJ. Analysis of p-Type Doping in Graphene Induced by Monolayer-Oxidized TMDs. ACS APPLIED MATERIALS & INTERFACES 2024; 16:3694-3702. [PMID: 38214703 DOI: 10.1021/acsami.3c16229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2024]
Abstract
Doping is one of the most difficult technological challenges for realizing reliable two-dimensional (2D) material-based semiconductor devices, arising from their ultrathinness. Here, we systematically investigate the impact of different types of nonstoichiometric solid MOx (M are W or Mo) dopants obtained by oxidizing transition metal dichalcogenides (TMDs: WSe2 or MoS2) formed on graphene FETs, which results in p-type doping along with disorders. From the results obtained in this study, we were able to suggest an analytical technique to optimize the optimal UV-ozone (UVO) treatment to achieve high p-type doping concentration in graphene FETs (∼2.5 × 1013 cm-2 in this study) without generating defects, mainly by analyzing the time dependency of D and D' peaks measured by Raman spectroscopy. Furthermore, an analysis of the structure of graphene sheets using TEM indicates that WOx plays a better protective role in graphene, compared to MoOx, suggesting that WOx is more effective for preventing the degradation of graphene during UVO treatment. To enhance the practical application aspect of our work, we have fabricated a graphene photodetector by selectively doping the graphene through oxidized TMDs, creating a p-n junction, which resulted in improved photoresponsivity compared to the intrinsic graphene device. Our results offer a practical guideline for the utilization of surface charge transfer doping of graphene toward CMOS applications.
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Affiliation(s)
- Tuyen Huynh
- SKKU Advanced Institute of Nano Technology, Sungkyunkwan University, Suwon, Gyeonggi-do 16419, Korea
| | - Tien Dat Ngo
- SKKU Advanced Institute of Nano Technology, Sungkyunkwan University, Suwon, Gyeonggi-do 16419, Korea
| | - Hyungyu Choi
- SKKU Advanced Institute of Nano Technology, Sungkyunkwan University, Suwon, Gyeonggi-do 16419, Korea
| | - Minsup Choi
- Department of Materials Science and Engineering, Chungnam National University, Daejeon 34134, Korea
| | - Wonki Lee
- Institute of Advanced Composite Materials, Korea Institute of Science and Technology (KIST), Wanju-gun, Jeolabuk-do 55324, Korea
| | - Tuan Dung Nguyen
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon, Gyeonggi-do 16419, Korea
| | - Trang Thu Tran
- Department of Energy Science, Sungkyunkwan University, Suwon, Gyeonggi-do 16419, Korea
| | - Kwangro Lee
- SKKU Advanced Institute of Nano Technology, Sungkyunkwan University, Suwon, Gyeonggi-do 16419, Korea
| | - Jun Yeon Hwang
- Institute of Advanced Composite Materials, Korea Institute of Science and Technology (KIST), Wanju-gun, Jeolabuk-do 55324, Korea
| | - Jeongyong Kim
- Department of Energy Science, Sungkyunkwan University, Suwon, Gyeonggi-do 16419, Korea
| | - Won Jong Yoo
- SKKU Advanced Institute of Nano Technology, Sungkyunkwan University, Suwon, Gyeonggi-do 16419, Korea
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Wang P, Fang F. Defect-Mediated Atomic Layer Etching Processes on Cl-Si(100): An Atomistic Insight. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2023; 127:21106-21113. [PMID: 37937159 PMCID: PMC10626627 DOI: 10.1021/acs.jpcc.3c05378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 09/21/2023] [Accepted: 10/09/2023] [Indexed: 11/09/2023]
Abstract
Defects play a significant role in atomic layer etching (ALE) processes; however, a fundamental understanding at the atomic level is still lacking. To bridge this knowledge gap, this study investigated the role of point defects in the laser-induced ALE of Cl-Si(100) using density functional theory (DFT) and real-time time-dependent DFT calculations. In the calculations, both the pristine surface and the defective surface were considered for comparative analysis. The key finding is the enhanced desorption of SiCl molecules, facilitated by point defects under laser pulse irradiation. The presence of point defects was found to effectively reduce both the desorption energy barrier and the laser intensity threshold required for desorption. Additionally, extra defective levels within the band gap were observed through the density-of-state diagram. Based on these findings, a defect-mediated etching regime was proposed to elucidate the layer-by-layer etching process. This study provides atomistic insight into understanding the role of defects in laser-induced ALE processes. The presence of point defects can enhance the etching selectivity between the topmost layer and the underlying layers, thereby contributing to highly efficient and damage-free etching processes through the defect-mediated etching mechanism.
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Affiliation(s)
- Peizhi Wang
- Centre
of Micro/Nano Manufacturing Technology (MNMT-Dublin), University College Dublin, Dublin D4, Ireland
| | - Fengzhou Fang
- Centre
of Micro/Nano Manufacturing Technology (MNMT-Dublin), University College Dublin, Dublin D4, Ireland
- State
Key Laboratory of Precision Measuring Technology and Instruments,
Laboratory of Micro/Nano Manufacturing Technology (MNMT), Tianjin University, Tianjin 300072, China
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Wang Z, Nie Y, Ou H, Chen D, Cen Y, Liu J, Wu D, Hong G, Li B, Xing G, Zhang W. Electronic and Optoelectronic Monolayer WSe 2 Devices via Transfer-Free Fabrication Method. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:1368. [PMID: 37110953 PMCID: PMC10145331 DOI: 10.3390/nano13081368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 04/06/2023] [Accepted: 04/12/2023] [Indexed: 06/19/2023]
Abstract
Monolayer transition metal dichalcogenides (TMDs) have drawn significant attention for their potential applications in electronics and optoelectronics. To achieve consistent electronic properties and high device yield, uniform large monolayer crystals are crucial. In this report, we describe the growth of high-quality and uniform monolayer WSe2 film using chemical vapor deposition on polycrystalline Au substrates. This method allows for the fabrication of continuous large-area WSe2 film with large-size domains. Additionally, a novel transfer-free method is used to fabricate field-effect transistors (FETs) based on the as-grown WSe2. The exceptional metal/semiconductor interfaces achieved through this fabrication method result in monolayer WSe2 FETs with extraordinary electrical performance comparable to those with thermal deposition electrodes, with a high mobility of up to ≈62.95 cm2 V-1 s-1 at room temperature. In addition, the as-fabricated transfer-free devices can maintain their original performance after weeks without obvious device decay. The transfer-free WSe2-based photodetectors exhibit prominent photoresponse with a high photoresponsivity of ~1.7 × 104 A W-1 at Vds = 1 V and Vg = -60 V and a maximum detectivity value of ~1.2 × 1013 Jones. Our study presents a robust pathway for the growth of high-quality monolayer TMDs thin films and large-scale device fabrication.
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Affiliation(s)
- Zixuan Wang
- Joint Key Laboratory of the Ministry of Education, Institute of Applied Physics and Materials Engineering, University of Macau, Avenida da Universidade, Taipa, Macao SAR 999078, China
- International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, China
| | - Yecheng Nie
- International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, China
| | - Haohui Ou
- International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, China
| | - Dao Chen
- International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, China
| | - Yingqian Cen
- International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, China
| | - Jidong Liu
- International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, China
| | - Di Wu
- International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, China
| | - Guo Hong
- Department of Materials Science and Engineering & Center of Super-Diamond and Advanced Films, College of Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR 999077, China
| | - Benxuan Li
- International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, China
- Electrical Engineering Division, Engineering Department, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA, UK
| | - Guichuan Xing
- Joint Key Laboratory of the Ministry of Education, Institute of Applied Physics and Materials Engineering, University of Macau, Avenida da Universidade, Taipa, Macao SAR 999078, China
| | - Wenjing Zhang
- International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, China
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Lee D, Choi Y, Kim J, Kim J. Recessed-Channel WSe 2 Field-Effect Transistor via Self-Terminated Doping and Layer-by-Layer Etching. ACS NANO 2022; 16:8484-8492. [PMID: 35575475 DOI: 10.1021/acsnano.2c03402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Effective channel control with low contact resistance can be accomplished through selective ion implantation in Si and III-V semiconductor technologies; however, this approach cannot be adopted for ultrathin van der Waals materials. Herein, we demonstrate a self-aligned fabrication process based on self-terminated p-doping and layer-by-layer chemical etching to achieve low contact resistance as well as a high on/off current ratio in ultrathin tungsten diselenide (WSe2) field-effect transistors (FETs). Damage-free layer-by-layer thinning of the WSe2 channel is repeated up to a thickness of approximately 1.4 nm, while maintaining the selectively p-doped source/drain regions. The device characteristics of the recessed-channel WSe2 FET are systematically monitored during this layer-by-layer recess-channel process. The WSe2 etching rate is estimated to be 2-3 layers per cycle of oxidation and subsequent chemical etching. The self-terminated tungsten oxide (WOX) layer grown through ultraviolet-ozone treatment induces robust p-doping in the neighboring (or underlying) WSe2 through the electron withdrawal mechanism, which remains in the source/drain regions after channel oxide removal. The adopted self-terminated and self-aligned recess-channel process for ultrathin WSe2 FETs enables the realization of a high on/off output current ratio (>108) and field-effect mobility (∼190 cm2/V·s), while maintaining low contact resistance (0.9-6.1 kΩ·μm) without a postannealing process. The proposed facile and reproducible doping and atomic-layer-etching method for the fabrication of a recessed-channel FET with an ultrathin body can be helpful for high-performance two-dimensional semiconductor devices and is applicable to post-Si complementary metal-oxide semiconductor devices.
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Affiliation(s)
- Dongryul Lee
- School of Chemical and Biological Engineering, Korea University, Seoul 02841, South Korea
| | - Yongha Choi
- School of Chemical and Biological Engineering, Korea University, Seoul 02841, South Korea
| | - Junghun Kim
- School of Chemical and Biological Engineering, Korea University, Seoul 02841, South Korea
| | - Jihyun Kim
- School of Chemical and Biological Engineering, Seoul National University, Seoul 08826, South Korea
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Liu X, Choi MS, Hwang E, Yoo WJ, Sun J. Fermi Level Pinning Dependent 2D Semiconductor Devices: Challenges and Prospects. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2108425. [PMID: 34913205 DOI: 10.1002/adma.202108425] [Citation(s) in RCA: 49] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 11/29/2021] [Indexed: 06/14/2023]
Abstract
Motivated by the high expectation for efficient electrostatic modulation of charge transport at very low voltages, atomically thin 2D materials with a range of bandgaps are investigated extensively for use in future semiconductor devices. However, researchers face formidable challenges in 2D device processing mainly originated from the out-of-plane van der Waals (vdW) structure of ultrathin 2D materials. As major challenges, untunable Schottky barrier height and the corresponding strong Fermi level pinning (FLP) at metal interfaces are observed unexpectedly with 2D vdW materials, giving rise to unmodulated semiconductor polarity, high contact resistance, and lowered device mobility. Here, FLP observed from recently developed 2D semiconductor devices is addressed differently from those observed from conventional semiconductor devices. It is understood that the observed FLP is attributed to inefficient doping into 2D materials, vdW gap present at the metal interface, and hybridized compounds formed under contacting metals. To provide readers with practical guidelines for the design of 2D devices, the impact of FLP occurring in 2D semiconductor devices is further reviewed by exploring various origins responsible for the FLP, effects of FLP on 2D device performances, and methods for improving metallic contact to 2D materials.
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Affiliation(s)
- Xiaochi Liu
- School of Physics and Electronics, Central South University, Changsha, 410083, China
| | - Min Sup Choi
- SKKU Advanced Institute of Nano Technology, Sungkyunkwan University, Suwon, 16419, South Korea
| | - Euyheon Hwang
- SKKU Advanced Institute of Nano Technology, Sungkyunkwan University, Suwon, 16419, South Korea
| | - Won Jong Yoo
- SKKU Advanced Institute of Nano Technology, Sungkyunkwan University, Suwon, 16419, South Korea
| | - Jian Sun
- School of Physics and Electronics, Central South University, Changsha, 410083, China
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Li X, Li B, Lei J, Bets KV, Sang X, Okogbue E, Liu Y, Unocic RR, Yakobson BI, Hone J, Harutyunyan AR. Nickel particle-enabled width-controlled growth of bilayer molybdenum disulfide nanoribbons. SCIENCE ADVANCES 2021; 7:eabk1892. [PMID: 34890223 PMCID: PMC8664269 DOI: 10.1126/sciadv.abk1892] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2021] [Accepted: 10/25/2021] [Indexed: 05/19/2023]
Abstract
Transition metal dichalcogenides exhibit a variety of electronic behaviors depending on the number of layers and width. Therefore, developing facile methods for their controllable synthesis is of central importance. We found that nickel nanoparticles promote both heterogeneous nucleation of the first layer of molybdenum disulfide and simultaneously catalyzes homoepitaxial tip growth of a second layer via a vapor-liquid-solid (VLS) mechanism, resulting in bilayer nanoribbons with width controlled by the nanoparticle diameter. Simulations further confirm the VLS growth mechanism toward nanoribbons and its orders of magnitude higher growth speed compared to the conventional noncatalytic growth of flakes. Width-dependent Coulomb blockade oscillation observed in the transfer characteristics of the nanoribbons at temperatures up to 60 K evidences the value of this proposed synthesis strategy for future nanoelectronics.
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Affiliation(s)
- Xufan Li
- Honda Research Institute USA Inc., San Jose, CA 95134, USA
| | - Baichang Li
- Mechanical Engineering Department, Columbia University, New York, NY 10025, USA
| | - Jincheng Lei
- Department of Materials Science and Nano Engineering, Rice University, Houston, TX 77005, USA
| | - Ksenia V. Bets
- Department of Materials Science and Nano Engineering, Rice University, Houston, TX 77005, USA
| | - Xiahan Sang
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | | | - Yang Liu
- Mechanical Engineering Department, Columbia University, New York, NY 10025, USA
| | - Raymond R. Unocic
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Boris I. Yakobson
- Department of Materials Science and Nano Engineering, Rice University, Houston, TX 77005, USA
| | - James Hone
- Mechanical Engineering Department, Columbia University, New York, NY 10025, USA
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