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Munson KT, Torsi R, Mathela S, Feidler MA, Lin YC, Robinson JA, Asbury JB. Influence of Substrate-Induced Charge Doping on Defect-Related Excitonic Emission in Monolayer MoS 2. J Phys Chem Lett 2024:7850-7856. [PMID: 39052863 DOI: 10.1021/acs.jpclett.4c01578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/27/2024]
Abstract
Many applications of transition metal dichalcogenides (TMDs) involve transfer to functional substrates that can strongly impact their optical and electronic properties. We investigate the impact that substrate interactions have on free carrier densities and defect-related excitonic (XD) emission from MoS2 monolayers grown by metal-organic chemical vapor deposition. C-plane sapphire substrates mimic common hydroxyl-terminated substrates. We demonstrate that transferring MoS2 monolayers to pristine c-plane sapphire dramatically increases the free electron density within MoS2 layers, quenches XD emission, and accelerates exciton recombination at the optical band edge. In contrast, transferring MoS2 monolayers onto inert hexagonal boron nitride (h-BN) has no measurable influence on these properties. Our findings demonstrate the promise of utilizing substrate engineering to control charge doping interactions and to quench broad XD background emission features that can influence the purity of single photon emitters in TMDs being developed for quantum photonic applications.
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Affiliation(s)
- Kyle T Munson
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Riccardo Torsi
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Shreya Mathela
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Maxwell A Feidler
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Yu-Chuan Lin
- Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu City 300, Taiwan
| | - Joshua A Robinson
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - John B Asbury
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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2
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Hussain SA, Zheng B, Xu Z, Liu Y, Wang H, Sun X, Zhu C, Wu G, Zheng W, Zhu X, Li D, Jiang Y, Pan A. Enhancing photoluminescence of WSe 2 in vapor grown WSe 2/VOCl bilayer heterojunctions via surface passivation. OPTICS LETTERS 2024; 49:3970-3973. [PMID: 39008753 DOI: 10.1364/ol.529048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2024] [Accepted: 06/22/2024] [Indexed: 07/17/2024]
Abstract
Monolayer tungsten selenide (WSe2) has attracted attention due to its direct bandgap-generated strong light emission and light-matter interaction. Herein, vertical WSe2/VOCl bilayer heterojunctions with enhanced PL of WSe2 were synthesized by the vapor growth method. The morphology, crystal structure, and chemical composition of the WSe2/VOCl heterojunctions were systematically investigated, which confirmed the successful formation of the heterojunctions. The PL emission intensity of WSe2 obtained from the WSe2/VOCl heterojunction was about 2.4 times higher than that of the WSe2 monolayer, demonstrating the high optical quality of the WSe2/VOCl heterojunction, which was further confirmed by time-resolved PL measurements. The insulator top VOCl, which was deposited on the surface of the semiconductor bottom WSe2 as a surface passivation material, reducing the impurities and resulting in an atomically clean surface, successfully enhanced the PL emission of the bottom WSe2. This vertical WSe2/VOCl bilayer heterojunction with PL enhancement could provide a promising platform for optical devices.
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3
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Singh S, Kim KH, Jo K, Musavigharavi P, Kim B, Zheng J, Trainor N, Chen C, Redwing JM, Stach EA, Olsson RH, Jariwala D. Nonvolatile Control of Valley Polarized Emission in 2D WSe 2-AlScN Heterostructures. ACS NANO 2024; 18:17958-17968. [PMID: 38918951 DOI: 10.1021/acsnano.4c04684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/27/2024]
Abstract
Achieving robust and electrically controlled valley polarization in monolayer transition metal dichalcogenides (ML-TMDs) is a frontier challenge for realistic valleytronic applications. Theoretical investigations show that the integration of 2D materials with ferroelectrics is a promising strategy; however, an experimental demonstration has remained elusive. Here, we fabricate ferroelectric field-effect transistors using a ML-WSe2 channel and an Al0.68Sc0.32N (AlScN) ferroelectric dielectric and experimentally demonstrate efficient tuning as well as non-volatile control of valley polarization. We measure a large array of transistors and obtain a maximum valley polarization of ∼27% at 80 K with stable retention up to 5400 s. The enhancement in the valley polarization is ascribed to the efficient exciton-to-trion (X-T) conversion and its coupling with an out-of-plane electric field, viz., the quantum-confined Stark effect. This changes the valley depolarization pathway from strong exchange interactions to slow spin-flip intervalley scattering. Our research demonstrates a promising approach for achieving non-volatile control over valley polarization for practical valleytronic device applications.
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Affiliation(s)
- Simrjit Singh
- Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
- Department of Applied Physics and Science Education, Eindhoven University of Technology, Eindhoven 5600 MB, The Netherlands
| | - Kwan-Ho Kim
- Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Kiyoung Jo
- Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Pariasadat Musavigharavi
- Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
- Department of Materials Science and Engineering, University of Central Florida, Orlando, Florida 32816, United States
| | - Bumho Kim
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Jeffrey Zheng
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Nicholas Trainor
- Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16801, United States
| | - Chen Chen
- 2D Crystal Consortium Materials Innovation Platform, Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16801, United States
| | - Joan M Redwing
- Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16801, United States
- 2D Crystal Consortium Materials Innovation Platform, Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16801, United States
| | - Eric A Stach
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Roy H Olsson
- Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Deep Jariwala
- Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
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4
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Jung J, Choi H, Lee Y, Kim Y, Taniguchi T, Watanabe K, Choi M, Jang JH, Chung H, Kim D, Kim Y, Cho C. Defect Passivation of 2D Semiconductors by Fixating Chemisorbed Oxygen Molecules via h-BN Encapsulations. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2310197. [PMID: 38493313 PMCID: PMC11165525 DOI: 10.1002/advs.202310197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2024] [Revised: 02/25/2024] [Indexed: 03/18/2024]
Abstract
Hexagonal boron nitride (h-BN) is a key ingredient for various 2D van der Waals heterostructure devices, but the exact role of h-BN encapsulation in relation to the internal defects of 2D semiconductors remains unclear. Here, it is reported that h-BN encapsulation greatly removes the defect-related gap states by stabilizing the chemisorbed oxygen molecules onto the defects of monolayer WS2 crystals. Electron energy loss spectroscopy (EELS) combined with theoretical analysis clearly confirms that the oxygen molecules are chemisorbed onto the defects of WS2 crystals and are fixated by h-BN encapsulation, with excluding a possibility of oxygen molecules trapped in bubbles or wrinkles formed at the interface between WS2 and h-BN. Optical spectroscopic studies show that h-BN encapsulation prevents the desorption of oxygen molecules over various excitation and ambient conditions, resulting in a greatly lowered and stabilized free electron density in monolayer WS2 crystals. This suppresses the exciton annihilation processes by two orders of magnitude compared to that of bare WS2. Furthermore, the valley polarization becomes robust against the various excitation and ambient conditions in the h-BN encapsulated WS2 crystals.
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Affiliation(s)
- Jin‐Woo Jung
- Department of Physics and ChemistryDaegu Gyeongbuk Institute of Science and Technology (DGIST)Daegu42988South Korea
| | - Hyeon‐Seo Choi
- Department of Physics and ChemistryDaegu Gyeongbuk Institute of Science and Technology (DGIST)Daegu42988South Korea
| | - Young‐Jun Lee
- Department of Physics and ChemistryDaegu Gyeongbuk Institute of Science and Technology (DGIST)Daegu42988South Korea
| | - Youngjae Kim
- School of PhysicsKorea Institute for Advanced Study (KIAS)Seoul02455South Korea
| | - Takashi Taniguchi
- International Center for Materials NanoarchitectonicsNational Institute for Materials ScienceTsukuba305‐0044Japan
| | - Kenji Watanabe
- Research Center for Functional MaterialsNational Institute for Materials ScienceTsukuba305‐0044Japan
| | - Min‐Yeong Choi
- Electron Microscopy and Spectroscopy TeamKorea Basic Science InstituteDaejeon34133South Korea
| | - Jae Hyuck Jang
- Electron Microscopy and Spectroscopy TeamKorea Basic Science InstituteDaejeon34133South Korea
- Graduate School of Analytic Science and TechnologyChungnam National UniversityDaejeon34134South Korea
| | - Hee‐Suk Chung
- Electron Microscopy and Spectroscopy TeamKorea Basic Science InstituteDaejeon34133South Korea
| | - Dohun Kim
- Department of Physics and ChemistryDaegu Gyeongbuk Institute of Science and Technology (DGIST)Daegu42988South Korea
| | - Youngwook Kim
- Department of Physics and ChemistryDaegu Gyeongbuk Institute of Science and Technology (DGIST)Daegu42988South Korea
| | - Chang‐Hee Cho
- Department of Physics and ChemistryDaegu Gyeongbuk Institute of Science and Technology (DGIST)Daegu42988South Korea
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5
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Ağırcan H, Convertino D, Rossi A, Martini L, Pace S, Mishra N, Küster K, Starke U, Kartal Şireli G, Coletti C, Forti S. Determination and investigation of defect domains in multi-shape monolayer tungsten disulfide. NANOSCALE ADVANCES 2024; 6:2850-2859. [PMID: 38817435 PMCID: PMC11134227 DOI: 10.1039/d4na00125g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Accepted: 04/15/2024] [Indexed: 06/01/2024]
Abstract
Single-layer tungsten disulfide (WS2) is among the most widely investigated two-dimensional materials. Synthesizing it over large areas would enable the exploitation of its appealing optical and electronic properties in industrial applications. However, defects of different nature, concentration and distribution profoundly affect the optical as well as the electronic properties of this crystal. Controlling the defect density distribution can be an effective way to tailor the local dielectric environment and therefore the electronic properties of the system. In this work we investigate the defects in single-layer WS2, grown in different shapes by liquid phase chemical vapor deposition, where the concentration of certain defect species can be controlled by the growth conditions. The properties of the material are surveyed by means of optical spectroscopy, photoelectron spectroscopy and Kelvin probe force microscopy. We determine the chemical nature of the defects and study their influence on the optical and electronic properties of WS2. This work contributes to the understanding of the microscopic nature of the intrinsic defects in WS2, helping the development of defect-based technologies which rely on the control and engineering of defects in dielectric 2D crystals.
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Affiliation(s)
- H Ağırcan
- Center for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia Piazza San Silvestro 12 I-56127 Pisa Italy
- Department of Metallurgical & Materials Engineering Istanbul Technical University 34469 Maslak Istanbul Turkey
| | - D Convertino
- Center for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia Piazza San Silvestro 12 I-56127 Pisa Italy
| | - A Rossi
- Center for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia Piazza San Silvestro 12 I-56127 Pisa Italy
- Graphene Labs, Istituto Italiano di Tecnologia Via Morego 30 16163 Genova Italy
| | - L Martini
- Center for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia Piazza San Silvestro 12 I-56127 Pisa Italy
| | - S Pace
- Center for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia Piazza San Silvestro 12 I-56127 Pisa Italy
- Graphene Labs, Istituto Italiano di Tecnologia Via Morego 30 16163 Genova Italy
| | - N Mishra
- Center for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia Piazza San Silvestro 12 I-56127 Pisa Italy
- Graphene Labs, Istituto Italiano di Tecnologia Via Morego 30 16163 Genova Italy
| | - K Küster
- Max-Planck-Institut für Festkörperforschung Heisenbergstr. 1 70569 Stuttgart Germany
| | - U Starke
- Max-Planck-Institut für Festkörperforschung Heisenbergstr. 1 70569 Stuttgart Germany
| | - G Kartal Şireli
- Department of Metallurgical & Materials Engineering Istanbul Technical University 34469 Maslak Istanbul Turkey
| | - C Coletti
- Center for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia Piazza San Silvestro 12 I-56127 Pisa Italy
- Graphene Labs, Istituto Italiano di Tecnologia Via Morego 30 16163 Genova Italy
| | - S Forti
- Center for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia Piazza San Silvestro 12 I-56127 Pisa Italy
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Lin WH, Li CS, Wu CI, Rossman GR, Atwater HA, Yeh NC. Dramatically Enhanced Valley-Polarized Emission by Alloying and Electrical Tuning of Monolayer WTe 2 x S 2(1- x ) Alloys at Room Temperature with 1T'-WTe 2 -Contact. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2304890. [PMID: 37974381 PMCID: PMC10787083 DOI: 10.1002/advs.202304890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 09/25/2023] [Indexed: 11/19/2023]
Abstract
Monolayer ternary tellurides based on alloying different transition metal dichalcogenides (TMDs) can result in new two-dimensional (2D) materials ranging from semiconductors to metals and superconductors with tunable optical and electrical properties. Semiconducting WTe2 x S2(1- x ) monolayer possesses two inequivalent valleys in the Brillouin zone, each valley coupling selectively with circularly polarized light (CPL). The degree of valley polarization (DVP) under the excitation of CPL represents the purity of valley polarized photoluminescence (PL), a critical parameter for opto-valleytronic applications. Here, new strategies to efficiently tailor the valley-polarized PL from semiconducting monolayer WTe2 x S2(1- x ) at room temperature (RT) through alloying and back-gating are presented. The DVP at RT is found to increase drastically from < 5% in WS2 to 40% in WTe0.12 S1.88 by Te-alloying to enhance the spin-orbit coupling. Further enhancement and control of the DVP from 40% up to 75% is demonstrated by electrostatically doping the monolayer WTe0.12 S1.88 via metallic 1T'-WTe2 electrodes, where the use of 1T'-WTe2 substantially lowers the Schottky barrier height (SBH) and weakens the Fermi-level pinning of the electrical contacts. The demonstration of drastically enhanced DVP and electrical tunability in the valley-polarized emission from 1T'-WTe2 /WTe0.12 S1.88 heterostructures paves new pathways towards harnessing valley excitons in ultrathin valleytronic devices for RT applications.
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Affiliation(s)
- Wei-Hsiang Lin
- Department of Applied Physics, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Chia-Shuo Li
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, 106, P. R. China
| | - Chih-I Wu
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, 106, P. R. China
| | - George R Rossman
- Department of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Harry A Atwater
- Department of Applied Physics, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Nai-Chang Yeh
- Department of Physics, California Institute of Technology, Pasadena, CA, 91125, USA
- Kavli Nanoscience Institute, California Institute of Technology, Pasadena, CA, 91125, USA
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7
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Sheng K, Zhang B, Wang ZY. Piezoelectricity and valley polarization in a semilithiated 2H-TiTe 2 monolayer with near room-temperature ferromagnetism. Phys Chem Chem Phys 2023; 25:23738-23745. [PMID: 37615079 DOI: 10.1039/d3cp02532b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
Two-dimensional ferromagnetic semiconductors with coupled valley physics and piezoelectric responses offer unprecedented opportunities to miniaturize low-power multifunctional integrated devices. Prompted by epitaxial fabrication of nonmagnetic 2H-TiTe2 monolayer on the Au(111) substrate, we predict through both density functional theory and Monte Carlo simulations that the semilithiated 2H-TiTe2 monolayer (Li@2H-TiTe2) is a stable near room-temperature semiconducting ferromagnet. Under an out-of-plane magnetization, Li@2H-TiTe2 exhibits a clean valley polarization up to 160 meV in its conduction band and a valley-contrasting Berry curvature due to the broken inversion and time-reversal symmetries, in favor of achievable anomalous valley Hall effect. Alternatively, the simultaneous charge, spin, valley Hall currents can be realized as well in the ferromagnetic system with circularly polarized light. Furthermore, the missing mirror symmetry generates a scarce vertical piezoelectricity as large as 0.89 pm V-1. These findings indicate that asymmetric surface functionalization by Li deposition on the 2H-TiTe2 monolayer opens up a vital avenue to predesign superior and tailored multifunctional materials.
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Affiliation(s)
- Kang Sheng
- School of Physical Science and Technology, Southwest University, Chongqing 400715, China
- Chongqing Key Laboratory of Micro-Nano Structure Optoelectronics, Chongqing 400715, China.
| | - Bokai Zhang
- School of Physical Science and Technology, Southwest University, Chongqing 400715, China
- Chongqing Key Laboratory of Micro-Nano Structure Optoelectronics, Chongqing 400715, China.
| | - Zhi-Yong Wang
- School of Physical Science and Technology, Southwest University, Chongqing 400715, China
- Chongqing Key Laboratory of Micro-Nano Structure Optoelectronics, Chongqing 400715, China.
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8
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Aftab S, Iqbal MZ, Hegazy HH, Azam S, Kabir F. Trends in energy and charge transfer in 2D and integrated perovskite heterostructures. NANOSCALE 2023; 15:3610-3629. [PMID: 36728545 DOI: 10.1039/d2nr07141j] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Two-dimensional (2D) van der Waals (vdW) heterostructured transition metal dichalcogenides (TMDs) open up new possibilities for a wide range of optoelectronic applications. Interlayer couplings are responsible for several fascinating physics phenomena, which are in addition to the multifunctionalities that have been discovered in the field of optoelectronics. These couplings can influence the overall charge, or the energy transfer processes via stacking, separation, and dielectric angles. This focused review article summarizes the most recent and promising strategies for interlayer exciton emission in 2D or integrated perovskites and TMD heterostructures. These types of devices require a thorough comprehension and effective control of interlayer couplings in order to realize their functionalities and improve performance, which is demonstrated in this article with the energy or charge transfer mechanisms in the individual devices. An ideal platform for examining the interlayer coupling and the related physical processes is provided by a summary of the recent research findings in 2D perovskites and TMDs. Furthermore, it would encourage more investigation into the comprehension and regulation of excitonic effects and the related optoelectronic applications in vdW heterostructures over a broad spectral response range. Finally, the current challenges and prospects are summarized in this paper.
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Affiliation(s)
- Sikandar Aftab
- Department of Intelligent Mechatronics Engineering, Sejong University, Seoul 05006, South Korea.
| | - Muhammad Zahir Iqbal
- Nanotechnology Research Laboratory, Faculty of Engineering Sciences, GIK Institute of Engineering Sciences and Technology, Topi 23640, Khyber Pakhtunkhwa, Pakistan
| | - Hosameldin Helmy Hegazy
- Research Center for Advanced Materials Science (RCAMS), King Khalid University, Abha 61413, P. O. Box 9004, Saudi Arabia
- Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha, Saudi Arabia
| | - Sikander Azam
- Department of Physics, Faculty of Engineering and Applied Sciences, Riphah International University, I-14 Campus, Islamabad, Islamabad, Pakistan.
| | - Fahmid Kabir
- School of Engineering Science, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
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Li X, Yang C, Xia Y, Zeng X, Shen P, Li L, Xu F, Cai D, Wu Y, Wu Z, Li S, Kang J. Nonvolatile Electrical Valley Manipulation in WS 2 by Ferroelectric Gating. ACS NANO 2022; 16:20598-20606. [PMID: 36414329 DOI: 10.1021/acsnano.2c07469] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Valleytronics in transition metal dichalcogenides has been intensively investigated for potential applications in next-generation information storage, data processing, and signal transmission devices. Here a ferroelectric gating approach is engaged in achieving nonvolatile electrical tuning of the valley-excitonic properties of monolayer and bilayer WS2. The gating effects include carrier doping and ferroelectric coupling, which are further distinguished by comparing two geometries where the gate electrodes are in direct contact with or insulated from the WS2 crystal. The results show that the carrier doping from gate electrodes acts on WS2 through carrier screening, which only moderately alters the valley polarization. In contrast, the ferroelectric gating promotes electron-phonon interaction, introduces a strong surface polarization field, and controls the interfacial charge trapping/detrapping, causing a Stark shift in exciton energy and strongly enhancing room-temperature valley polarization. In bilayer WS2, the intralayer-interlayer exciton transition is further induced, contributing to even higher valley polarization. The ferroelectric coupling effect can still be maintained after the removal of gate voltage, showing its nonvolatile nature. The role of ferroelectricity is further verified by the anomalous temperature dependence in valley polarization. This work has revealed effective electrical control over valley excitons in semiconductors through interaction with ferroelectric materials. The reported high room-temperature valley polarization in WS2 will boost the development of valleytronics devices.
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Affiliation(s)
- Xu Li
- Department of Physics, Engineering Research Center for Micro-Nano Optoelectronic Materials and Devices, Ministry of Education, Fujian Provincial Key Laboratory of Semiconductor Materials and Applications, Jiujiang Research Institute, Xiamen University, Xiamen361005, P.R. China
| | - Chengbiao Yang
- Department of Physics, Engineering Research Center for Micro-Nano Optoelectronic Materials and Devices, Ministry of Education, Fujian Provincial Key Laboratory of Semiconductor Materials and Applications, Jiujiang Research Institute, Xiamen University, Xiamen361005, P.R. China
| | - Yuanzheng Xia
- Department of Physics, Engineering Research Center for Micro-Nano Optoelectronic Materials and Devices, Ministry of Education, Fujian Provincial Key Laboratory of Semiconductor Materials and Applications, Jiujiang Research Institute, Xiamen University, Xiamen361005, P.R. China
| | - Xinlong Zeng
- Department of Physics, Engineering Research Center for Micro-Nano Optoelectronic Materials and Devices, Ministry of Education, Fujian Provincial Key Laboratory of Semiconductor Materials and Applications, Jiujiang Research Institute, Xiamen University, Xiamen361005, P.R. China
| | - Peng Shen
- Department of Physics, Engineering Research Center for Micro-Nano Optoelectronic Materials and Devices, Ministry of Education, Fujian Provincial Key Laboratory of Semiconductor Materials and Applications, Jiujiang Research Institute, Xiamen University, Xiamen361005, P.R. China
| | - Linglong Li
- School of Physics, Southeast University, Nanjing211189, P.R. China
| | - Feiya Xu
- Department of Physics, Engineering Research Center for Micro-Nano Optoelectronic Materials and Devices, Ministry of Education, Fujian Provincial Key Laboratory of Semiconductor Materials and Applications, Jiujiang Research Institute, Xiamen University, Xiamen361005, P.R. China
| | - Duanjun Cai
- Department of Physics, Engineering Research Center for Micro-Nano Optoelectronic Materials and Devices, Ministry of Education, Fujian Provincial Key Laboratory of Semiconductor Materials and Applications, Jiujiang Research Institute, Xiamen University, Xiamen361005, P.R. China
| | - Yaping Wu
- Department of Physics, Engineering Research Center for Micro-Nano Optoelectronic Materials and Devices, Ministry of Education, Fujian Provincial Key Laboratory of Semiconductor Materials and Applications, Jiujiang Research Institute, Xiamen University, Xiamen361005, P.R. China
| | - Zhiming Wu
- Department of Physics, Engineering Research Center for Micro-Nano Optoelectronic Materials and Devices, Ministry of Education, Fujian Provincial Key Laboratory of Semiconductor Materials and Applications, Jiujiang Research Institute, Xiamen University, Xiamen361005, P.R. China
| | - Shuping Li
- Department of Physics, Engineering Research Center for Micro-Nano Optoelectronic Materials and Devices, Ministry of Education, Fujian Provincial Key Laboratory of Semiconductor Materials and Applications, Jiujiang Research Institute, Xiamen University, Xiamen361005, P.R. China
| | - Junyong Kang
- Department of Physics, Engineering Research Center for Micro-Nano Optoelectronic Materials and Devices, Ministry of Education, Fujian Provincial Key Laboratory of Semiconductor Materials and Applications, Jiujiang Research Institute, Xiamen University, Xiamen361005, P.R. China
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10
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Pippia G, Van Hamme D, Martín-García B, Prato M, Moreels I. A colloidal route to semiconducting tungsten disulfide nanosheets with monolayer thickness. NANOSCALE 2022; 14:15859-15868. [PMID: 36259965 DOI: 10.1039/d2nr04307f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Transition metal dichalcogenides (TMDs) are a class of materials that have been extensively studied in the last decade, with molybdenum disulfide (MoS2) being the main protagonist. Typically, the interesting TMD properties, e.g. a direct band gap transition, or broken inversion symmetry, are only present in monolayer thick TMDs, and in the absence of strong lateral confinement, we require different materials or alloys thereof when we want to obtain TMDs with varying (direct) band gap energies. With this in mind, tungsten disulfide (WS2) is emerging as a direct competitor of MoS2 due to its similar properties but larger band gap energy. While several colloidal strategies have been reported for the synthesis of WS2, the synthesis of monolayer WS2 and detailed studies on the effect of synthesis parameters on the synthesis outcome have remained elusive. In this work we therefore focused on a colloidal synthesis method for monolayer WS2 using a design of experiment (DOE) approach. After optimization, we obtained nanosheets with a band gap transition consistent with the expected value for a monolayer. The thickness was further confirmed by Raman spectroscopy. While we could identify two temperature ranges where we could obtain a monolayer, sample characterization by XPS spectroscopy revealed the presence of different ratios of the metallic phase, with the sample synthesized at lower temperature displaying a lower concentration of the metallic phase.
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Affiliation(s)
- Gabriele Pippia
- Ghent University, Department of Chemistry, Krijgslaan 281, 9000 Gent, Belgium.
| | - Diem Van Hamme
- Ghent University, Department of Chemistry, Krijgslaan 281, 9000 Gent, Belgium.
| | - Beatriz Martín-García
- CIC nanoGUNE BRTA, Tolosa Hiribidea 76, 20018 Donostia-San Sebastián, Basque Country, Spain
| | - Mirko Prato
- Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - Iwan Moreels
- Ghent University, Department of Chemistry, Krijgslaan 281, 9000 Gent, Belgium.
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11
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Kayal A, Barman PK, Sarma PV, Shaijumon MM, Kini RN, Mitra J. Symmetric domain segmentation in WS 2flakes: correlating spatially resolved photoluminescence, conductance with valley polarization. NANOTECHNOLOGY 2022; 33:495203. [PMID: 36041399 DOI: 10.1088/1361-6528/ac8d9d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Accepted: 08/30/2022] [Indexed: 06/15/2023]
Abstract
The incidence of intra-flake heterogeneity of spectroscopic and electrical properties in chemical vapour deposited (CVD) WS2flakes is explored in a multi-physics investigation via spatially resolved spectroscopic maps correlated with electrical, electronic and mechanical properties. The investigation demonstrates that the three-fold symmetric segregation of spectroscopic response, in topographically uniform WS2flakes are accompanied by commensurate segmentation of electronic properties e.g. local carrier density and the differences in the mechanics of tip-sample interactions, evidenced via scanning probe microscopy phase maps. Overall, the differences are understood to originate from point defects, namely sulfur vacancies within the flake along with a dominant role played by the substrate. While evolution of the multi-physics maps upon sulfur annealing elucidates the role played by sulfur vacancy, substrate-induced effects are investigated by contrasting data from WS2flake on Si and Au surfaces. Local charge depletion induced by the nature of the sample-substrate junction in case of WS2on Au is seen to invert the electrical response with comprehensible effects on their spectroscopic properties. Finally, the role of these optoelectronic properties in preserving valley polarization that affects valleytronic applications in WS2flakes, is investigated via circular polarization discriminated photoluminescence experiments. The study provides a thorough understanding of spatial heterogeneity in optoelectronic properties of WS2and other transition metal chalcogenides, which are critical for device fabrication and potential applications.
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Affiliation(s)
- Arijit Kayal
- School of Physics, IISER Thiruvananthapuram, Kerala 695551, India
| | | | - Prasad V Sarma
- School of Physics, IISER Thiruvananthapuram, Kerala 695551, India
| | - M M Shaijumon
- School of Physics, IISER Thiruvananthapuram, Kerala 695551, India
| | - R N Kini
- School of Physics, IISER Thiruvananthapuram, Kerala 695551, India
| | - J Mitra
- School of Physics, IISER Thiruvananthapuram, Kerala 695551, India
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12
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Zhou HL, Zhang XY, Xue XM, Yang Y, Wang SJ, Su D, Yang ZR, Wang YF, Song Y, Wu J, Wu W, Zhang T. Nanoscale Valley Modulation by Surface Plasmon Interference. NANO LETTERS 2022; 22:6923-6929. [PMID: 36006735 DOI: 10.1021/acs.nanolett.2c01442] [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
Excitons in two-dimensional (2D) materials have attracted the attention of the community to develop improved photoelectronic devices. Previous reports are based on direct excitation where the out-of-plane illumination projects a uniform single-mode light spot. However, because of the optical diffraction limit, the minimal spot size is a few micrometers, inhibiting the precise manipulation and control of excitons at the nanoscale level. Herein, we introduced the in-plane coherent surface plasmonic interference (SPI) field to excite and modulate excitons remotely. Compared to the out-of-plane light, a uniform in-plane SPI suggests a more compact spatial volume and an abundance of mode selections for a single or an array of device modulation. Our results not only build up a fundamental platform for operating and encoding the exciton states at the nanoscale level but also provide a new avenue toward all-optical integrated valleytronic chips for future quantum computation and information applications.
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Affiliation(s)
- Huan-Li Zhou
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing, Jiangsu 210096, China
| | - Xiao-Yang Zhang
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing, Jiangsu 210096, China
| | - Xiao-Mei Xue
- Key Laboratory of Micro-Inertial Instrument and Advanced Navigation Technology, Ministry of Education, and School of Instrument Science and Engineering, Southeast University, Nanjing, Jiangsu 210096, China
| | - Yi Yang
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing, Jiangsu 210096, China
| | - Shan-Jiang Wang
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing, Jiangsu 210096, China
| | - Dan Su
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing, Jiangsu 210096, China
| | - Zong-Ru Yang
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing, Jiangsu 210096, China
| | - Yun-Fan Wang
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing, Jiangsu 210096, China
| | - Yuanjun Song
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing, Jiangsu 210096, China
| | - Jingyuan Wu
- Department of Optoelectronic Science and Engineering, College of Science, Donghua University, Shanghai 201620, China
| | - Weiping Wu
- Laboratory of Thin Film Optics, State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
| | - Tong Zhang
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing, Jiangsu 210096, China
- Key Laboratory of Micro-Inertial Instrument and Advanced Navigation Technology, Ministry of Education, and School of Instrument Science and Engineering, Southeast University, Nanjing, Jiangsu 210096, China
- Suzhou Key Laboratory of Metal Nano-Optoelectronic Technology, Southeast University Suzhou Campus, Suzhou, Jiangsu 215123, China
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13
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Zhang Q, Sun H, Tang J, Dai X, Wang Z, Ning CZ. Prolonging valley polarization lifetime through gate-controlled exciton-to-trion conversion in monolayer molybdenum ditelluride. Nat Commun 2022; 13:4101. [PMID: 35835766 PMCID: PMC9283389 DOI: 10.1038/s41467-022-31672-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Accepted: 06/29/2022] [Indexed: 11/16/2022] Open
Abstract
Monolayer 2D semiconductors provide an attractive option for valleytronics due to valley-addressability. But the short valley-polarization lifetimes for excitons have hindered potential valleytronic applications. In this paper, we demonstrate a strategy for prolonging the valley-polarization lifetime by converting excitons to trions through efficient gate control and exploiting the much longer valley-polarization lifetimes for trions than for excitons. At charge neutrality, the valley lifetime of monolayer MoTe2 increases by a factor of 1000 to the order of nanoseconds from excitons to trions. The exciton-to-trion conversion changes the dominant depolarization mechanism from the fast electron-hole exchange for excitons to the slow spin-flip process for trions. Moreover, the degree of valley polarization increases to 38% for excitons and 33% for trions through electrical manipulation. Our results reveal the depolarization dynamics and the interplay of various depolarization channels for excitons and trions, providing an effective strategy for prolonging the valley polarization. Here, the authors devise a strategy for prolonging the valley polarization lifetime in monolayer MoTe2 by converting excitons to trions through gate control, and by taking advantage of the longer valley polarization lifetime of trions.
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Affiliation(s)
- Qiyao Zhang
- Department of Electronic Engineering, Tsinghua University, 100084, Beijing, China.,Frontier Science Center for Quantum Information, 100084, Beijing, China.,Tsinghua International Center for Nano-Optoelectronics, Tsinghua University, 100084, Beijing, China
| | - Hao Sun
- Department of Electronic Engineering, Tsinghua University, 100084, Beijing, China.,Frontier Science Center for Quantum Information, 100084, Beijing, China.,Tsinghua International Center for Nano-Optoelectronics, Tsinghua University, 100084, Beijing, China
| | - Jiacheng Tang
- Department of Electronic Engineering, Tsinghua University, 100084, Beijing, China.,Frontier Science Center for Quantum Information, 100084, Beijing, China.,Tsinghua International Center for Nano-Optoelectronics, Tsinghua University, 100084, Beijing, China
| | - Xingcan Dai
- Department of Electronic Engineering, Tsinghua University, 100084, Beijing, China
| | - Zhen Wang
- Department of Electronic Engineering, Tsinghua University, 100084, Beijing, China.,Frontier Science Center for Quantum Information, 100084, Beijing, China.,Tsinghua International Center for Nano-Optoelectronics, Tsinghua University, 100084, Beijing, China
| | - Cun-Zheng Ning
- Department of Electronic Engineering, Tsinghua University, 100084, Beijing, China. .,Frontier Science Center for Quantum Information, 100084, Beijing, China. .,Tsinghua International Center for Nano-Optoelectronics, Tsinghua University, 100084, Beijing, China.
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14
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Dang J, Yang M, Xie X, Yang Z, Dai D, Zuo Z, Wang C, Jin K, Xu X. Enhanced Valley Polarization in WS 2 /LaMnO 3 Heterostructure. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2106029. [PMID: 35266315 DOI: 10.1002/smll.202106029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2021] [Revised: 11/23/2021] [Indexed: 06/14/2023]
Abstract
Monolayer transition metal dichalcogenides have attracted great attention for potential applications in valleytronics. However, the valley polarization degree is usually not high because of the intervalley scattering. Here, a largely enhanced valley polarization up to 80% in monolayer WS2 under nonresonant excitation at 4.2 K is demonstrated using WS2 /LaMnO3 thin film heterostructure, which is much higher than that for monolayer WS2 on SiO2 /Si substrate with a valley polarization of 15%. Furthermore, the greatly enhanced valley polarization can be maintained to a high temperature of about 160 K with a valley polarization of 53%. The temperature dependence of valley polarization is strongly correlated with the thermomagnetic curve of LaMnO3 , indicating an exciton-magnon coupling between WS2 and LaMnO3 . A simple model is introduced to illustrate the underlying mechanisms. The coupling of WS2 and LaMnO3 is further confirmed with an observation of two interlayer excitons with opposite valley polarizations in the heterostructure, resulting from the spin-orbit coupling induced splitting of the conduction bands in monolayer transition metal dichalcogenides. The results provide a pathway to control the valleytronic properties of transition metal dichalcogenides by means of ferromagnetic van der Waals engineering, paving a way to practical valleytronic applications.
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Affiliation(s)
- Jianchen Dang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- CAS Center for Excellence in Topological Quantum Computation and School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Mingwei Yang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- CAS Center for Excellence in Topological Quantum Computation and School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xin Xie
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- CAS Center for Excellence in Topological Quantum Computation and School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Zhen Yang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- CAS Center for Excellence in Topological Quantum Computation and School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Danjie Dai
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- CAS Center for Excellence in Topological Quantum Computation and School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Zhanchun Zuo
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- CAS Center for Excellence in Topological Quantum Computation and School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Can Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- CAS Center for Excellence in Topological Quantum Computation and School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China
| | - Kuijuan Jin
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- CAS Center for Excellence in Topological Quantum Computation and School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China
| | - Xiulai Xu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- CAS Center for Excellence in Topological Quantum Computation and School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China
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15
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Lin WH, Wu PC, Akbari H, Rossman GR, Yeh NC, Atwater HA. Electrically Tunable and Dramatically Enhanced Valley-Polarized Emission of Monolayer WS 2 at Room Temperature with Plasmonic Archimedes Spiral Nanostructures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2104863. [PMID: 34725874 DOI: 10.1002/adma.202104863] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 10/03/2021] [Indexed: 05/27/2023]
Abstract
Monolayer transition metal dichalcogenides (TMDs) have intrinsic valley degrees of freedom, making them appealing for exploiting valleytronic applications in information storage and processing. WS2 monolayer possesses two inequivalent valleys in the Brillouin zone, each valley coupling selectively with a circular polarization of light. The degree of valley polarization (DVP) under the excitation of circularly polarized light (CPL) is a parameter that determines the purity of valley polarized photoluminescence (PL) of monolayer WS2 . Here efficient tailoring of valley-polarized PL from monolayer WS2 at room temperature (RT) through surface plasmon-exciton interactions with plasmonic Archimedes spiral (PAS) nanostructures is reported. The DVP of WS2 at RT can be enhanced from <5% to 40% and 50% by using 2 turns (2T) and 4 turns (4T) of PAS, respectively. Further enhancement and control of excitonic valley polarization is demonstrated by electrostatically doping monolayer WS2 . For CPL on WS2 -2TPAS heterostructures, the 40% valley polarization is enhanced to 70% by modulating the carrier doping via a backgate, which may be attributed to the screening of momentum-dependent long-range electron-hole exchange interactions. The manifestation of electrically tunable valley-polarized emission from WS2 -PAS heterostructures presents a new strategy toward harnessing valley excitons for application in ultrathin valleytronic devices.
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Affiliation(s)
- Wei-Hsiang Lin
- Department of Applied Physics, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Pin Chieh Wu
- Department of Photonics, National Cheng Kung University, Tainan, 70101, Taiwan
| | - Hamidreza Akbari
- Department of Applied Physics, California Institute of Technology, Pasadena, CA, 91125, USA
| | - George R Rossman
- Department of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Nai-Chang Yeh
- Department of Physics, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Harry A Atwater
- Department of Applied Physics, California Institute of Technology, Pasadena, CA, 91125, USA
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16
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Guo J, Lu Z, Wang K, Zhao X, Hu G, Yuan X, Ren J. Large valley polarization in a novel two-dimensional semiconductor H-ZrX 2(X =Cl, Br, I). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 34:075701. [PMID: 34768243 DOI: 10.1088/1361-648x/ac394f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Accepted: 11/12/2021] [Indexed: 06/13/2023]
Abstract
Inspired by the new progress in the research field of two-dimensional valleytronics materials, we propose a new class of transition metal halides, i.e. H-ZrX2(X = Cl, Br, I), and investigated their valleytronics properties under the first-principles calculations. It harbors the spin-valley coupling at K and K' points in the top of valence band, in which the valley spin splitting of ZrI2can reach up to 115 meV. By carrying out the strain engineering, the valley spin splitting and Berry curvature can be effectively tuned. The long-sought valley polarization reaches up to 108 meV by doping Cr atom, which corresponds to the large Zeeman magnetic field of 778 T. Furthermore, the valley polarization in ZrX2can be lineally adjusted or flipped by manipulating the magnetization orientation of the doped magnetic atoms. All the results demonstrate the well-founded application prospects of single-layer ZrX2, which can be considered as great candidate for the development of valleytronics and spintronics.
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Affiliation(s)
- Jiatian Guo
- School of Physics and Electronics, Shandong Normal University, Jinan 250014, People's Republic of China
| | - Zhutong Lu
- School of Physics and Electronics, Shandong Normal University, Jinan 250014, People's Republic of China
| | - Keyu Wang
- School of Physics and Electronics, Shandong Normal University, Jinan 250014, People's Republic of China
| | - Xiuwen Zhao
- School of Physics and Electronics, Shandong Normal University, Jinan 250014, People's Republic of China
| | - Guichao Hu
- School of Physics and Electronics, Shandong Normal University, Jinan 250014, People's Republic of China
| | - Xiaobo Yuan
- School of Physics and Electronics, Shandong Normal University, Jinan 250014, People's Republic of China
| | - Junfeng Ren
- School of Physics and Electronics, Shandong Normal University, Jinan 250014, People's Republic of China
- Shandong Provincial Engineering and Technical Center of Light Manipulations & Institute of Materials and Clean Energy, Shandong Normal University, Jinan 250014, People's Republic of China
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17
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Li S, Wang S, Xu T, Zhang H, Tang Y, Liu S, Jiang T, Zhou S, Cheng H. Growth mechanism and atomic structure of group-IIA compound-promoted CVD-synthesized monolayer transition metal dichalcogenides. NANOSCALE 2021; 13:13030-13041. [PMID: 34477786 DOI: 10.1039/d1nr03273a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Developing promoters that can boost the growth quality, efficiency, and robustness of two-dimensional (2D) transition metal dichalcogenides is significant for their industrial applications. Herein a new group (group IIA) of promoters in the periodic table has been disclosed, whose chlorides (especially CaCl2 and SrCl2) exhibit a versatile promoting effect on the CVD growth of various TMD monolayers, including hexagonal MoS2, MoSe2, Re doped MoS2, and triclinic ReS2. The promoting effect of group IIA promoters relies on the appropriate dose and is strongly substrate-dependent. The performances of five typical group IA-IIA metal chlorides are ranked by quantitative investigations, displaying periodic variations closely related to the electronegativities of the metal elements. A brand-new acid-base match model is proposed, attributing the promoting mechanism to an increase of the substrate basicity due to the usage of promoters, thus leading to the sufficient adsorption of the acidic precursor. Aberration-corrected annular dark field scanning transmission electron microscopy (ADF-STEM) was applied, unveiling anomalous grain boundaries (GBs) with a low density of coincident sites in the as-grown ReS2 and detailed atomic configurations of Re doped MoS2. This work expands the promoter library and gives an insight into GB engineering for the CVD growth of 2D TMDs.
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Affiliation(s)
- Shouheng Li
- Science and Technology on Advanced Ceramic Fibers and Composites Laboratory, College of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073, P. R. China.
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18
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Goswami T, Bhatt H, Babu KJ, Kaur G, Ghorai N, Ghosh HN. Ultrafast Insights into High Energy (C and D) Excitons in Few Layer WS 2. J Phys Chem Lett 2021; 12:6526-6534. [PMID: 34242025 DOI: 10.1021/acs.jpclett.1c01627] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
High energy (C and D) excitons possess extraordinary influence over the optical properties of atomically thin transition metal dichalcogenides (TMDCs), and the comprehensive understanding of these would play a pivotal role in advancing research on 2D optoelectronics. Herein, we employed transient absorption spectroscopy to monitor the underlying photophysical processes involved with different excitonic features in few layer WS2, modeled as a TMDC representative. We observed a strong intervalley coupling across the momentum space and proposed the most plausible relaxation pathway for different excitons in few layer scenario. C and D exciton dynamics were significantly slower as compared to canonical A and B excitons, as a consequence of the indirect Λ-Γ relaxation in C and D and direct K-K combination in A and B. Most importantly, all four excitons emerge in the system and influence each other irrespective of the incident photon energy, which would be extremely impactful in fabricating wide range photonic devices.
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Affiliation(s)
- Tanmay Goswami
- Institute of Nano Science and Technology, Knowledge City, Sector 81, SAS Nagar, Punjab 140306, India
| | - Himanshu Bhatt
- Institute of Nano Science and Technology, Knowledge City, Sector 81, SAS Nagar, Punjab 140306, India
| | - K Justice Babu
- Institute of Nano Science and Technology, Knowledge City, Sector 81, SAS Nagar, Punjab 140306, India
| | - Gurpreet Kaur
- Institute of Nano Science and Technology, Knowledge City, Sector 81, SAS Nagar, Punjab 140306, India
| | - Nandan Ghorai
- Institute of Nano Science and Technology, Knowledge City, Sector 81, SAS Nagar, Punjab 140306, India
| | - Hirendra N Ghosh
- Institute of Nano Science and Technology, Knowledge City, Sector 81, SAS Nagar, Punjab 140306, India
- Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India
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19
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Karpińska M, Liang M, Kempt R, Finzel K, Kamminga M, Dyksik M, Zhang N, Knodlseder C, Maude DK, Baranowski M, Kłopotowski Ł, Ye J, Kuc A, Plochocka P. Nonradiative Energy Transfer and Selective Charge Transfer in a WS 2/(PEA) 2PbI 4 Heterostructure. ACS APPLIED MATERIALS & INTERFACES 2021; 13:33677-33684. [PMID: 34227384 DOI: 10.1021/acsami.1c08377] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
van der Waals heterostructures are currently the focus of intense investigation; this is essentially due to the unprecedented flexibility offered by the total relaxation of lattice matching requirements and their new and exotic properties compared to the individual layers. Here, we investigate the hybrid transition-metal dichalcogenide/2D perovskite heterostructure WS2/(PEA)2PbI4 (where PEA stands for phenylethylammonium). We present the first density functional theory (DFT) calculations of a heterostructure ensemble, which reveal a novel band alignment, where direct electron transfer is blocked by the organic spacer of the 2D perovskite. In contrast, the valence band forms a cascade from WS2 through the PEA to the PbI4 layer allowing hole transfer. These predictions are supported by optical spectroscopy studies, which provide compelling evidence for both charge transfer and nonradiative transfer of the excitation (energy transfer) between the layers. Our results show that TMD/2D perovskite (where TMD stands for transition-metal dichalcogenides) heterostructures provide a flexible and convenient way to engineer the band alignment.
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Affiliation(s)
- Miriam Karpińska
- Laboratoire National des Champs Magnétiques Intenses, UPR 3228, CNRS-UGA-UPS-INSA, 38042 Grenoble and 31400 Toulouse, France
- Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw, Poland
| | - Minpeng Liang
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Roman Kempt
- Technische Universität Dresden, Bergstr. 66c, 01062 Dresden, Germany
| | - Kati Finzel
- Technische Universität Dresden, Bergstr. 66c, 01062 Dresden, Germany
| | - Machteld Kamminga
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Mateusz Dyksik
- Laboratoire National des Champs Magnétiques Intenses, UPR 3228, CNRS-UGA-UPS-INSA, 38042 Grenoble and 31400 Toulouse, France
- Department of Experimental Physics, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, 50-370 Wroclaw, Poland
| | - Nan Zhang
- Laboratoire National des Champs Magnétiques Intenses, UPR 3228, CNRS-UGA-UPS-INSA, 38042 Grenoble and 31400 Toulouse, France
| | - Catherine Knodlseder
- Laboratoire National des Champs Magnétiques Intenses, UPR 3228, CNRS-UGA-UPS-INSA, 38042 Grenoble and 31400 Toulouse, France
| | - Duncan K Maude
- Laboratoire National des Champs Magnétiques Intenses, UPR 3228, CNRS-UGA-UPS-INSA, 38042 Grenoble and 31400 Toulouse, France
| | - Michał Baranowski
- Department of Experimental Physics, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, 50-370 Wroclaw, Poland
| | | | - Jianting Ye
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Agnieszka Kuc
- Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstrasse 400, 01328 Dresden, Germany
| | - Paulina Plochocka
- Laboratoire National des Champs Magnétiques Intenses, UPR 3228, CNRS-UGA-UPS-INSA, 38042 Grenoble and 31400 Toulouse, France
- Department of Experimental Physics, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, 50-370 Wroclaw, Poland
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20
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Lloyd LT, Wood RE, Mujid F, Sohoni S, Ji KL, Ting PC, Higgins JS, Park J, Engel GS. Sub-10 fs Intervalley Exciton Coupling in Monolayer MoS 2 Revealed by Helicity-Resolved Two-Dimensional Electronic Spectroscopy. ACS NANO 2021; 15:10253-10263. [PMID: 34096707 DOI: 10.1021/acsnano.1c02381] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The valley pseudospin at the K and K' high-symmetry points in monolayer transition metal dichalcogenides (TMDs) has potential as an optically addressable degree of freedom in next-generation optoelectronics. However, intervalley scattering and relaxation of charge carriers leads to valley depolarization and limits practical applications. In addition, enhanced Coulomb interactions lead to pronounced excitonic effects that dominate the optical response and initial valley depolarization dynamics but complicate the interpretation of ultrafast spectroscopic experiments at short time delays. Employing broadband helicity-resolved two-dimensional electronic spectroscopy (2DES), we observe ultrafast (∼10 fs) intervalley coupling between all A and B valley exciton states that results in a complete breakdown of the valley index in large-area monolayer MoS2 films. These couplings and subsequent dynamics exhibit minimal excitation fluence or temperature dependence and are robust toward changes in sample grain size and inherent strain. Our observations strongly suggest that this direct intervalley coupling on the time scale of optical excitation is an inherent property of large-area MoS2 distinct from dynamic carrier or exciton scattering, phonon-driven processes, and multiexciton effects. This ultrafast intervalley coupling poses a fundamental challenge for exciton-based valleytronics in monolayer TMDs and must be overcome to fully realize large-area valleytronic devices.
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Affiliation(s)
- Lawson T Lloyd
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Ryan E Wood
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Fauzia Mujid
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
| | - Siddhartha Sohoni
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Karen L Ji
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Po-Chieh Ting
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Jacob S Higgins
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Jiwoong Park
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, United States
| | - Gregory S Engel
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
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21
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Wu L, Cong C, Yang W, Chen Y, Shao Y, Do TTH, Wen W, Feng S, Zou C, Zhang H, Du B, Cao B, Shang J, Xiong Q, Loh KP, Yu T. Observation of Strong Valley Magnetic Response in Monolayer Transition Metal Dichalcogenide Alloys of Mo 0.5W 0.5Se 2 and Mo 0.5W 0.5Se 2/WS 2 Heterostructures. ACS NANO 2021; 15:8397-8406. [PMID: 33881826 DOI: 10.1021/acsnano.0c10478] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Monolayer transition metal dichalcogenide (TMD) alloys have emerged as a unique material system for promising applications in electronics, optoelectronics, and spintronics due to their tunable electronic structures, effective masses of carriers, and valley polarization with various alloy compositions. Although spin-orbit engineering has been extensively studied in monolayer TMD alloys, the valley Zeeman effect in these alloys still remains largely unexplored. Here we demonstrate the enhanced valley magnetic response in Mo0.5W0.5Se2 alloy monolayers and Mo0.5W0.5Se2/WS2 heterostructures probed by magneto-photoluminescence spectroscopy. The large g factors of negatively charged excitons (trions) of Mo0.5W0.5Se2 have been extracted for both pure Mo0.5W0.5Se2 monolayers and Mo0.5W0.5Se2/WS2 heterostructures, which are attributed to the significant impact of doping-induced strong many-body Coulomb interactions on trion emissions under an out-of-plane magnetic field. Moreover, compared with the monolayer Mo0.5W0.5Se2, the slightly reduced valley Zeeman splitting in Mo0.5W0.5Se2/WS2 is a consequence of the weakened exchange interaction arising from p-doping in Mo0.5W0.5Se2 via interlayer charge transfer between Mo0.5W0.5Se2 and WS2. Such interlayer charge transfer further evidences the formation of type-II band alignment, in agreement with the density functional theory calculations. Our findings give insights into the spin-valley and interlayer coupling effects in monolayer TMD alloys and their heterostructures, which are essential to develop valleytronic applications based on the emerging family of TMD alloys.
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Affiliation(s)
- Lishu Wu
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Chunxiao Cong
- State Key Laboratory of ASIC and System, School of Information Science and Technology, Fudan University, Shanghai 200433, P. R. China
| | - Weihuang Yang
- Key Laboratory of RF Circuits and System of Ministry of Education, Hangzhou Dianzi University, Hangzhou 310018, Zhejiang, P. R. China
| | - Yu Chen
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Yan Shao
- Department of Chemistry, National University of Singapore, Singapore 117543, Singapore
| | - T Thu Ha Do
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Wen Wen
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Shun Feng
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Chenji Zou
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Hongbo Zhang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Bowen Du
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Bingchen Cao
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Jingzhi Shang
- Xi'an Institute of Flexible Electronics, Northwestern Polytechnical University, Xi'an 710072, Shaanxi, P. R. China
| | - Qihua Xiong
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Kian Ping Loh
- Department of Chemistry, National University of Singapore, Singapore 117543, Singapore
| | - Ting Yu
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
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22
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Zhao S, Li X, Dong B, Wang H, Wang H, Zhang Y, Han Z, Zhang H. Valley manipulation in monolayer transition metal dichalcogenides and their hybrid systems: status and challenges. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2021; 84:026401. [PMID: 33440363 DOI: 10.1088/1361-6633/abdb98] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Recently, the emerging conceptual valley-related devices have attracted much attention due to the progress on generating, controlling, and detecting the valley degree of freedom in the transition metal dichalcogenide (TMD) monolayers. In general, it is known that achieving valley degree of freedom with long valley lifetime is crucial in the implementation of valleytronic devices. Here, we provide a brief introduction of the basic understandings of valley degree of freedom. We as well review the recent experimental advancement in the modulation of valley degree of freedom. The strategies include optical/magnetic/electric field tuning, moiré patterns, plasmonic metasurface, defects and strain engineering. In addition, we summarize the corresponding mechanisms, which can help to obtain large degree of polarization and long valley lifetimes in monolayer TMDs. Based on these methods, two-dimensional valley-optoelectronic systems based on TMD heterostructures can be constructed, providing opportunities for such as the new paradigm in data processing and transmission. Challenges and perspectives on the development of valleytronics are highlighted as well.
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Affiliation(s)
- Siwen Zhao
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, People's Republic of China
- College of Materials Science and Engineering, Shenzhen University, Shenzhen 518060, People's Republic of China
| | - Xiaoxi Li
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, People's Republic of China
- School of Material Science and Engineering, University of Science and Technology of China, Hefei 230026, People's Republic of China
| | - Baojuan Dong
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, People's Republic of China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, People's Republic of China
| | - Huide Wang
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, People's Republic of China
| | - Hanwen Wang
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, People's Republic of China
- School of Material Science and Engineering, University of Science and Technology of China, Hefei 230026, People's Republic of China
| | - Yupeng Zhang
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, People's Republic of China
| | - Zheng Han
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, People's Republic of China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, People's Republic of China
| | - Han Zhang
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, People's Republic of China
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23
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Riche F, Bragança H, Qu F, Lopez-Richard V, Xie SJ, Dias AC, Marques GE. Robust room temperature emissions of trion in darkish WSe 2monolayers: effects of dark neutral and charged excitonic states. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:365702. [PMID: 32365339 DOI: 10.1088/1361-648x/ab8fd4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2020] [Accepted: 05/04/2020] [Indexed: 06/11/2023]
Abstract
Owing to nonzero charge and spin degrees of freedom, trions offer unprecedented tunability and open new paths for applications in devices based on 2D semiconductors. However, in monolayer WSe2, the trion photoluminescence is commonly detected only at low temperatures and vanishes at room temperature, which undermines practical applications. To unveil how to overcome this obstacle, we have developed a comprehensive theory to probe the impact of different excitonic channels on the trion emission in WSe2monolayers, which combinesab initiotight-binding formalism, Bethe-Salpeter equation and a set of coupled rate equations to describe valley dynamics of excitonic particles. Through a systematic study in which new scattering channels are progressively included, we found that, besides the low electron density, strong many-body correlations between bright and dark excitonic states quenches the trion emission in WSe2. Therefore, the reduction of scatterings from bright to dark states is required to achieve trion emission at room temperature for experimentally accessible carrier concentrations.
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Affiliation(s)
- Flavio Riche
- Instituto de Física, Universidade de Brasília, Brasília-DF, Brazil
| | - Helena Bragança
- Departamento de Física, Universidade Federal de Ouro Preto, Ouro Preto-MG, Brazil
- Departamento de Física, Universidade Federal de São Carlos, São Carlos-SP, Brazil
| | - Fanyao Qu
- Instituto de Física, Universidade de Brasília, Brasília-DF, Brazil
| | - Victor Lopez-Richard
- Departamento de Física, Universidade Federal de São Carlos, São Carlos-SP, Brazil
| | - S J Xie
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan, People's Republic of China
| | - A C Dias
- Instituto de Física, Universidade de Brasília, Brasília-DF, Brazil
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24
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Chi Z, Chen H, Zhao Q, Weng YX. Observation of the hot-phonon effect in monolayer MoS 2. NANOTECHNOLOGY 2020; 31:235712. [PMID: 32097893 DOI: 10.1088/1361-6528/ab79ad] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Femtosecond transient absorption measurements have been performed to study the pump wavelength- and fluence-dependent hot carrier relaxation dynamics in monolayer MoS2. The relaxation process of the photoinduced carriers monitored within hundreds of femtoseconds after photoexcitation is demonstrated to be achieved through the carrier-phonon scattering mechanism. It is observed that an efficient hot-phonon effect can slow down the relaxation rate by around three times with the injected carrier density changing from 1 × 1012 to 3 × 1013 cm-2. A pronounced increase in the hot carrier relaxation time with decreasing temperature is further detected, which is attributed to the decreased phonon occupancy at lower temperature.
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Affiliation(s)
- Zhen Chi
- Center for Quantum Technology Research, School of Physics, Beijing Institute of Technology, Beijing 100081, People's Republic of China. Beijing National Laboratory for Condensed Matter Physics, CAS Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
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25
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Tanaka K, Hachiya K, Zhang W, Matsuda K, Miyauchi Y. Machine-Learning Analysis to Predict the Exciton Valley Polarization Landscape of 2D Semiconductors. ACS NANO 2019; 13:12687-12693. [PMID: 31584791 DOI: 10.1021/acsnano.9b04220] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We demonstrate the applicability of employing machine-learning-based analysis to predict the low-temperature exciton valley polarization landscape of monolayer tungsten diselenide (1L-WSe2) using position-dependent information extracted from its photoluminescence (PL) spectra at room temperature. We performed low- and room-temperature polarization-resolved PL mapping and used the obtained experimental data to create regression models for the prediction using the Random Forest machine-learning algorithm. The local information extracted from the room-temperature PL spectra and the low-temperature exciton valley polarization was used as the input and output data for the machine-learning process, respectively. The spatial distribution of the exciton valley polarization in a 1L-WSe2 sample that was not used for the learning of the decision trees was successfully predicted. Furthermore, we numerically obtained the degree of importance for each input variable and demonstrated that this parameter provides helpful information for examining the physics that shape the spatially heterogeneous valley polarization landscape of 1L-WSe2.
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Affiliation(s)
- Kenya Tanaka
- Institute of Advanced Energy , Kyoto University , Gokasho, Uji, Kyoto 611-0011 , Japan
| | - Kengo Hachiya
- Institute of Advanced Energy , Kyoto University , Gokasho, Uji, Kyoto 611-0011 , Japan
| | - Wenjin Zhang
- Institute of Advanced Energy , Kyoto University , Gokasho, Uji, Kyoto 611-0011 , Japan
| | - Kazunari Matsuda
- Institute of Advanced Energy , Kyoto University , Gokasho, Uji, Kyoto 611-0011 , Japan
| | - Yuhei Miyauchi
- Institute of Advanced Energy , Kyoto University , Gokasho, Uji, Kyoto 611-0011 , Japan
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26
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Zhang J, Du L, Feng S, Zhang RW, Cao B, Zou C, Chen Y, Liao M, Zhang B, Yang SA, Zhang G, Yu T. Enhancing and controlling valley magnetic response in MoS 2/WS 2 heterostructures by all-optical route. Nat Commun 2019; 10:4226. [PMID: 31530805 PMCID: PMC6748949 DOI: 10.1038/s41467-019-12128-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2019] [Accepted: 08/20/2019] [Indexed: 11/24/2022] Open
Abstract
Van der Waals heterostructures of transition metal dichalcogenides with interlayer coupling offer an exotic platform to realize fascinating phenomena. Due to the type II band alignment of these heterostructures, electrons and holes are separated into different layers. The localized electrons induced doping in one layer, in principle, would lift the Fermi level to cross the spin-polarized upper conduction band and lead to strong manipulation of valley magnetic response. Here, we report the significantly enhanced valley Zeeman splitting and magnetic tuning of polarization for the direct optical transition of MoS2 in MoS2/WS2 heterostructures. Such strong enhancement of valley magnetic response in MoS2 stems from the change of the spin-valley degeneracy from 2 to 4 and strong many-body Coulomb interactions induced by ultrafast charge transfer. Moreover, the magnetic splitting can be tuned monotonically by laser power, providing an effective all-optical route towards engineering and manipulating of valleytronic devices and quantum-computation. Van der Waals heterostructures may offer a suitable platform for all-optical manipulation of valleytronic devices. Here, the authors observe a strong enhancement of the valley magnetic response in MoS2, and magnetic tuning of the polarization of MoS2 direct optical transition
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Affiliation(s)
- Jing Zhang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 63737, Singapore
| | - Luojun Du
- CAS Key Laboratory of Nanoscale Physics and Devices, Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China.,Department of Electronics and Nanoengineering, Aalto University, FI-02150, Tietotie 3, Finland
| | - Shun Feng
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 63737, Singapore
| | - Run-Wu Zhang
- Research Laboratory for Quantum Materials, Singapore University of Technology and Design, Singapore, 487372, Singapore.,Key Lab of advanced optoelectronic quantum architecture and measurement (MOE), Beijing Key Lab of Nanophotonics & ultrafine Optoelectronic Systems, and School of Physics, Beijing Institute of Technology, 100081, Beijing, China
| | - Bingchen Cao
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 63737, Singapore
| | - Chenji Zou
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 63737, Singapore
| | - Yu Chen
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 63737, Singapore
| | - Mengzhou Liao
- CAS Key Laboratory of Nanoscale Physics and Devices, Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China
| | - Baile Zhang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 63737, Singapore
| | - Shengyuan A Yang
- Research Laboratory for Quantum Materials, Singapore University of Technology and Design, Singapore, 487372, Singapore
| | - Guangyu Zhang
- CAS Key Laboratory of Nanoscale Physics and Devices, Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China. .,Songshan Lake Materials Laboratory, Dongguan, 523808, Guangdong, China.
| | - Ting Yu
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 63737, Singapore.
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