1
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Chen SH, Chang SW, Chen HL. Characterization of 2D Transition Metal Dichalcogenides Through Anisotropic Exciton Behaviors. SMALL METHODS 2024; 8:e2301061. [PMID: 38098297 DOI: 10.1002/smtd.202301061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 11/03/2023] [Indexed: 05/18/2024]
Abstract
This study reports the first attempt to characterize the quality, defects, and strain of as-grown monolayer transition metal dichalcogenide (TMDC)-based 2D materials through exciton anisotropy. A standard ellipsometric parameter (Ψ) to observe anisotropic exciton behavior in monolayer 2D materials is used. According to the strong exciton effect from phonon-electron coupling processes, the change in the exciton in the Van Hove singularity is sensitive to lattice distortions such as defects and strain. In comparison with Raman spectroscopy, the variations in exciton anisotropy in Ψ are more sensitive for detecting slight changes in the quality and strain of monolayer TMDC films. Moreover, the optical power requirement for TMDC characterization through exciton anisotropy in Ψ is ≈10-5 mW cm-2, which is significantly less than that of Raman spectroscopy (≈106 mW cm-2). The standard deviation of the signals varies with strain (defects) in Raman spectra and exciton anisotropies in Ψ are 0.700 (0.795) and 0.033 (0.073), indicating that exciton anisotropy is more sensitive to slight changes in the quality of monolayer TMDC films.
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Affiliation(s)
- Shu-Hsien Chen
- Department of Materials Science and Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617, Taiwan
| | - Sih-Wei Chang
- Department of Materials Science and Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617, Taiwan
| | - Hsuen-Li Chen
- Department of Materials Science and Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617, Taiwan
- Center of Atomic Initiative for New Materials, National Taiwan University, Taipei, 10617, Taiwan
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2
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Lian Z, Li YM, Yan L, Ma L, Chen D, Taniguchi T, Watanabe K, Zhang C, Shi SF. Stark Effects of Rydberg Excitons in a Monolayer WSe 2 P-N Junction. NANO LETTERS 2024. [PMID: 38607185 DOI: 10.1021/acs.nanolett.4c00134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/13/2024]
Abstract
The enhanced Coulomb interaction in two-dimensional semiconductors leads to tightly bound electron-hole pairs known as excitons. The large binding energy of excitons enables the formation of Rydberg excitons with high principal quantum numbers (n), analogous to Rydberg atoms. Rydberg excitons possess strong interactions among themselves as well as sensitive responses to external stimuli. Here, we probe Rydberg exciton resonances through photocurrent spectroscopy in a monolayer WSe2 p-n junction formed by a split-gate geometry. We show that an external in-plane electric field not only induces a large Stark shift of Rydberg excitons up to quantum principal number 3 but also mixes different orbitals and brightens otherwise dark states such as 3p and 3d. Our study provides an exciting platform for engineering Rydberg excitons for new quantum states and quantum sensing.
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Affiliation(s)
- Zhen Lian
- Department of Physics, Carnegie Mellon University, Pittsburgh 15213, Pennsylvania, United States
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy 12180, New York, United States
| | - Yun-Mei Li
- Department of Physics, School of Physical Science and Technology, Xiamen University, Xiamen 361005, China
| | - Li Yan
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy 12180, New York, United States
| | - Lei Ma
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy 12180, New York, United States
| | - Dongxue Chen
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy 12180, New York, United States
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Chuanwei Zhang
- Department of Physics, University of Texas at Dallas, Richardson 75080, Texas, United States
- Department of Physics, Washington University in St Louis, St. Louis 63105, Missouri, United States
| | - Su-Fei Shi
- Department of Physics, Carnegie Mellon University, Pittsburgh 15213, Pennsylvania, United States
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy 12180, New York, United States
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3
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Akeredolu B, Ahemen I, Amah A, Onojah A, Shakya J, Gayathri H, Ghosh A. Improved liquid phase exfoliation technique for the fabrication of MoS 2/graphene heterostructure-based photodetector. Heliyon 2024; 10:e24964. [PMID: 38322969 PMCID: PMC10845704 DOI: 10.1016/j.heliyon.2024.e24964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2023] [Revised: 01/11/2024] [Accepted: 01/17/2024] [Indexed: 02/08/2024] Open
Abstract
2D nanosheets produced using liquid phase exfoliation method offers scalable and cost effective routes to optoelectronics devices. But this technique sometimes yields high defect, low stability, and compromised electronic properties. In this work, we employed an innovative approach that improved the existing liquid phase exfoliation method for fabricating MoS2/graphene heterostructure-based photodetector with enhanced optoelectronic properties. This technique involves hydrothermally treating MoS2 before dispersing it in a carefully chosen and environmentally friendly IPA/water solvent for ultrasonication exfoliation through an optomechanical approach. Thereafter, heterostructure nanosheets of MoS2 and graphene were formed through sequential deposition technique for the fabrication of vertical heterojunctions. Furthermore, we achieved a vertically stacked MoS2/graphene photodetector and a bare MoS2 photodetector. The MoS2/graphene hybrid nanosheets were characterized using spectroscopic and microscopic techniques. The results obtained show the size of the nanosheets is between 350 and 500 nm on average, and their thickness is less than or equal to 5 nm, and high crystallinity in the 2H semiconducting phase. The photocurrent, photoresponsivity, external quantum efficiency (EQE), and specific detectivity of MoS2/graphene heterostructure at 4 V bias voltage and 650 nm illumination wavelength were 3.55 μA, 39.44 mA/W, 7.54 %, and 2.02 × 1010 Jones, respectively, and that of MoS2 photodetector are 0.55 μA, 6.11 mA/W, 1.16 %, and 3.4 × 109 Jones. The results presented indicate that the photoresponse performances of the as-prepared MoS2/graphene were greatly improved (about 7-fold) compared to the photoresponse of the sole MoS2. Again, the MoS2/graphene heterostructure fabricated in this work show better optoelectronic characteristics as compared to the similar heterostructure prepared using the conventional solution processed method. The results provide a modest, inexpensive, and efficient method to fabricate heterojunctions with improved optoelectronic performance.
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Affiliation(s)
- B.J. Akeredolu
- Department of Physics Joseph Sarwuan Tarka University, Makurdi, P.M.B. 2373, Nigeria
- Department of Pure and Applied Physics Federal University, Wukari, P.M.B 1020, Nigeria
- Department of Physics, Indian Institute of Science, Bangalore, 560012, India
| | - I. Ahemen
- Department of Physics Joseph Sarwuan Tarka University, Makurdi, P.M.B. 2373, Nigeria
| | - A.N. Amah
- Department of Physics Joseph Sarwuan Tarka University, Makurdi, P.M.B. 2373, Nigeria
| | - A.D. Onojah
- Department of Physics Joseph Sarwuan Tarka University, Makurdi, P.M.B. 2373, Nigeria
| | - Jyoti Shakya
- Department of Physics, Indian Institute of Science, Bangalore, 560012, India
| | - H.N. Gayathri
- Department of Physics, Indian Institute of Science, Bangalore, 560012, India
| | - Arindam Ghosh
- Department of Physics, Indian Institute of Science, Bangalore, 560012, India
- Centre for Nano Science and Engineering, Indian Institute of Science, Bangalore, 560012, India
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4
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Bhardwaj A, Suryanarayana P. Strain engineering of Zeeman and Rashba effects in transition metal dichalcogenide nanotubes and their Janus variants: an ab initiostudy. NANOTECHNOLOGY 2024; 35:185701. [PMID: 38271729 DOI: 10.1088/1361-6528/ad22b5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Accepted: 01/24/2024] [Indexed: 01/27/2024]
Abstract
We study the influence of mechanical deformations on the Zeeman and Rashba effects in transition metal dichalcogenide nanotubes and their Janus variants from first principles. In particular, we perform symmetry-adapted density functional theory simulations with spin-orbit coupling to determine the variation in the electronic band structure splittings with axial and torsional deformations. We find significant effects in molybdenum and tungsten nanotubes, for which the Zeeman splitting decreases with increase in strain, going to zero for large enough tensile/shear strains, while the Rashba splitting coefficient increases linearly with shear strain, while being zero for all tensile strains, a consequence of the inversion symmetry remaining unbroken. In addition, the Zeeman splitting is relatively unaffected by nanotube diameter, whereas the Rashba coefficient decreases with increase in diameter. Overall, mechanical deformations represent a powerful tool for spintronics in nanotubes.
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Affiliation(s)
- Arpit Bhardwaj
- College of Engineering, Georgia Institute of Technology, Atlanta, GA 30332, United States of America
| | - Phanish Suryanarayana
- College of Engineering, Georgia Institute of Technology, Atlanta, GA 30332, United States of America
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5
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Handa T, Holbrook M, Olsen N, Holtzman LN, Huber L, Wang HI, Bonn M, Barmak K, Hone JC, Pasupathy AN, Zhu X. Spontaneous exciton dissociation in transition metal dichalcogenide monolayers. SCIENCE ADVANCES 2024; 10:eadj4060. [PMID: 38295176 PMCID: PMC10830119 DOI: 10.1126/sciadv.adj4060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2023] [Accepted: 12/28/2023] [Indexed: 02/02/2024]
Abstract
Since the seminal work on MoS2, photoexcitation in atomically thin transition metal dichalcogenides (TMDCs) has been assumed to result in excitons, with binding energies order of magnitude larger than thermal energy at room temperature. Here, we reexamine this foundational assumption and show that photoexcitation of TMDC monolayers can result in a substantial population of free charges. Performing ultrafast terahertz spectroscopy on large-area, single-crystal TMDC monolayers, we find that up to ~10% of excitons spontaneously dissociate into charge carriers with lifetimes exceeding 0.2 ns. Scanning tunneling microscopy reveals that photocarrier generation is intimately related to mid-gap defects, likely via trap-mediated Auger scattering. Only in state-of-the-art quality monolayers, with mid-gap trap densities as low as 109 cm-2, does intrinsic exciton physics start to dominate the terahertz response. Our findings reveal the necessity of knowing the defect density in understanding photophysics of TMDCs.
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Affiliation(s)
- Taketo Handa
- Department of Chemistry, Columbia University, New York, NY 10027, USA
| | - Madisen Holbrook
- Department of Physics, Columbia University, New York, NY 10027, USA
| | - Nicholas Olsen
- Department of Chemistry, Columbia University, New York, NY 10027, USA
| | - Luke N. Holtzman
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY 10027, USA
| | - Lucas Huber
- Department of Chemistry, Columbia University, New York, NY 10027, USA
| | - Hai I. Wang
- Max Planck Institute for Polymer Research, Mainz 55128, Germany
| | - Mischa Bonn
- Max Planck Institute for Polymer Research, Mainz 55128, Germany
| | - Katayun Barmak
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY 10027, USA
| | - James C. Hone
- Department of Mechanical Engineering, Columbia University, New York, NY 10027, USA
| | | | - Xiaoyang Zhu
- Department of Chemistry, Columbia University, New York, NY 10027, USA
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6
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Katiyar AK, Hoang AT, Xu D, Hong J, Kim BJ, Ji S, Ahn JH. 2D Materials in Flexible Electronics: Recent Advances and Future Prospectives. Chem Rev 2024; 124:318-419. [PMID: 38055207 DOI: 10.1021/acs.chemrev.3c00302] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
Flexible electronics have recently gained considerable attention due to their potential to provide new and innovative solutions to a wide range of challenges in various electronic fields. These electronics require specific material properties and performance because they need to be integrated into a variety of surfaces or folded and rolled for newly formatted electronics. Two-dimensional (2D) materials have emerged as promising candidates for flexible electronics due to their unique mechanical, electrical, and optical properties, as well as their compatibility with other materials, enabling the creation of various flexible electronic devices. This article provides a comprehensive review of the progress made in developing flexible electronic devices using 2D materials. In addition, it highlights the key aspects of materials, scalable material production, and device fabrication processes for flexible applications, along with important examples of demonstrations that achieved breakthroughs in various flexible and wearable electronic applications. Finally, we discuss the opportunities, current challenges, potential solutions, and future investigative directions about this field.
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Affiliation(s)
- Ajit Kumar Katiyar
- School of Electrical and Electronic Engineering, Yonsei University, Seoul 03722, Republic of Korea
| | - Anh Tuan Hoang
- School of Electrical and Electronic Engineering, Yonsei University, Seoul 03722, Republic of Korea
| | - Duo Xu
- School of Electrical and Electronic Engineering, Yonsei University, Seoul 03722, Republic of Korea
| | - Juyeong Hong
- School of Electrical and Electronic Engineering, Yonsei University, Seoul 03722, Republic of Korea
| | - Beom Jin Kim
- School of Electrical and Electronic Engineering, Yonsei University, Seoul 03722, Republic of Korea
| | - Seunghyeon Ji
- School of Electrical and Electronic Engineering, Yonsei University, Seoul 03722, Republic of Korea
| | - Jong-Hyun Ahn
- School of Electrical and Electronic Engineering, Yonsei University, Seoul 03722, Republic of Korea
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7
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Yagodkin D, Kumar A, Ankerhold E, Richter J, Watanabe K, Taniguchi T, Gahl C, Bolotin KI. Probing the Formation of Dark Interlayer Excitons via Ultrafast Photocurrent. NANO LETTERS 2023; 23:9212-9218. [PMID: 37788809 PMCID: PMC10603811 DOI: 10.1021/acs.nanolett.3c01708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 08/15/2023] [Indexed: 10/05/2023]
Abstract
Optically dark excitons determine a wide range of properties of photoexcited semiconductors yet are hard to access via conventional time-resolved spectroscopies. Here, we develop a time-resolved ultrafast photocurrent technique (trPC) to probe the formation dynamics of optically dark excitons. The nonlinear nature of the trPC makes it particularly sensitive to the formation of excitons occurring at the femtosecond time scale after the excitation. As a proof of principle, we extract the interlayer exciton formation time of 0.4 ps at 160 μJ/cm2 fluence in a MoS2/MoSe2 heterostructure and show that this time decreases with fluence. In addition, our approach provides access to the dynamics of carriers and their interlayer transport. Overall, our work establishes trPC as a technique to study dark excitons in various systems that are hard to probe by other approaches.
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Affiliation(s)
- Denis Yagodkin
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Abhijeet Kumar
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Elias Ankerhold
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Johanna Richter
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Kenji Watanabe
- Research
Center for Functional Materials, National
Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International
Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Cornelius Gahl
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
| | - Kirill I. Bolotin
- Department
of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
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8
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Biswas S, Champagne A, Haber JB, Pokawanvit S, Wong J, Akbari H, Krylyuk S, Watanabe K, Taniguchi T, Davydov AV, Al Balushi ZY, Qiu DY, da Jornada FH, Neaton JB, Atwater HA. Rydberg Excitons and Trions in Monolayer MoTe 2. ACS NANO 2023; 17:7685-7694. [PMID: 37043483 DOI: 10.1021/acsnano.3c00145] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Monolayer transition metal dichalcogenide (TMDC) semiconductors exhibit strong excitonic optical resonances, which serve as a microscopic, noninvasive probe into their fundamental properties. Like the hydrogen atom, such excitons can exhibit an entire Rydberg series of resonances. Excitons have been extensively studied in most TMDCs (MoS2, MoSe2, WS2, and WSe2), but detailed exploration of excitonic phenomena has been lacking in the important TMDC material molybdenum ditelluride (MoTe2). Here, we report an experimental investigation of excitonic luminescence properties of monolayer MoTe2 to understand the excitonic Rydberg series, up to 3s. We report a significant modification of emission energies with temperature (4 to 300 K), thereby quantifying the exciton-phonon coupling. Furthermore, we observe a strongly gate-tunable exciton-trion interplay for all the Rydberg states governed mainly by free-carrier screening, Pauli blocking, and band gap renormalization in agreement with the results of first-principles GW plus Bethe-Salpeter equation approach calculations. Our results help bring monolayer MoTe2 closer to its potential applications in near-infrared optoelectronics and photonic devices.
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Affiliation(s)
- Souvik Biswas
- Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125, United States
- Kavli Nanoscience Institute, Pasadena, California 91125, United States
| | - Aurélie Champagne
- Materials and Chemical Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Department of Physics, University of California Berkeley, Berkeley, California 94720, United States
| | - Jonah B Haber
- Department of Physics, University of California Berkeley, Berkeley, California 94720, United States
| | - Supavit Pokawanvit
- Department of Applied Physics, Stanford University, Stanford, California 94305, United States
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
| | - Joeson Wong
- Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125, United States
- Kavli Nanoscience Institute, Pasadena, California 91125, United States
| | - Hamidreza Akbari
- Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125, United States
| | - Sergiy Krylyuk
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials, Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Albert V Davydov
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Zakaria Y Al Balushi
- Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125, United States
| | - Diana Y Qiu
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520, United States
| | - Felipe H da Jornada
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
| | - Jeffrey B Neaton
- Materials and Chemical Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Department of Physics, University of California Berkeley, Berkeley, California 94720, United States
- Kavli Energy Nanosciences Institute at Berkeley, Berkeley, California 94720, United States
| | - Harry A Atwater
- Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125, United States
- Kavli Nanoscience Institute, Pasadena, California 91125, United States
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9
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Austin R, Farah Y, Sayer T, Luther B, Montoya-Castillo A, Krummel A, Sambur J. Hot carrier extraction from 2D semiconductor photoelectrodes. Proc Natl Acad Sci U S A 2023; 120:e2220333120. [PMID: 37011201 PMCID: PMC10104502 DOI: 10.1073/pnas.2220333120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 03/07/2023] [Indexed: 04/05/2023] Open
Abstract
Hot carrier-based energy conversion systems could double the efficiency of conventional solar energy technology or drive photochemical reactions that would not be possible using fully thermalized, "cool" carriers, but current strategies require expensive multijunction architectures. Using an unprecedented combination of photoelectrochemical and in situ transient absorption spectroscopy measurements, we demonstrate ultrafast (<50 fs) hot exciton and free carrier extraction under applied bias in a proof-of-concept photoelectrochemical solar cell made from earth-abundant and potentially inexpensive monolayer (ML) MoS2. Our approach facilitates ultrathin 7 Å charge transport distances over 1 cm2 areas by intimately coupling ML-MoS2 to an electron-selective solid contact and a hole-selective electrolyte contact. Our theoretical investigations of the spatial distribution of exciton states suggest greater electronic coupling between hot exciton states located on peripheral S atoms and neighboring contacts likely facilitates ultrafast charge transfer. Our work delineates future two-dimensional (2D) semiconductor design strategies for practical implementation in ultrathin photovoltaic and solar fuel applications.
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Affiliation(s)
- Rachelle Austin
- Department of Chemistry, Colorado State University, Fort Collins, CO80523
| | - Yusef R. Farah
- Department of Chemistry, Colorado State University, Fort Collins, CO80523
| | - Thomas Sayer
- Department of Chemistry, University of Colorado Boulder, Boulder, CO80309
| | - Bradley M. Luther
- Department of Chemistry, Colorado State University, Fort Collins, CO80523
| | | | - Amber T. Krummel
- Department of Chemistry, Colorado State University, Fort Collins, CO80523
| | - Justin B. Sambur
- Department of Chemistry, Colorado State University, Fort Collins, CO80523
- School of Advanced Materials Discovery, Colorado State University, Fort Collins, CO80523
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10
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Wang K, Paulus B. Cluster Formation Effect of Water on Pristine and Defective MoS 2 Monolayers. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:229. [PMID: 36677982 PMCID: PMC9864297 DOI: 10.3390/nano13020229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 12/23/2022] [Accepted: 12/27/2022] [Indexed: 06/17/2023]
Abstract
The structure and electronic properties of the molybdenum disulfide (MoS2) monolayer upon water cluster adsorption are studied using density functional theory and the optical properties are further analyzed with the Bethe-Salpeter equation (BSE). Our results reveal that the water clusters are electron acceptors, and the acceptor tendency tends to increase with the size of the water cluster. The electronic band gap of both pristine and defective MoS2 is rather insensitive to water cluster adsorbates, as all the clusters are weakly bound to the MoS2 surface. However, our calculations on the BSE level show that the adsorption of the water cluster can dramatically redshift the optical absorption for both pristine and defective MoS2 monolayers. The binding energy of the excitons of MoS2 is greatly enhanced with the increasing size of the water cluster and finally converges to a value of approximately 1.16 eV and 1.09 eV for the pristine and defective MoS2 monolayers, respectively. This illustrates that the presence of the water cluster could localize the excitons of MoS2, thereby greatly enhance the excitonic binding energy.
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11
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Barhoumi M, Bouzidi S, Sfina N, Bouelnor GAA. First-principles calculations to investigate electronic and optical properties of Ti 4GaPbX 2 (X = C or N) two-dimensional materials. Chem Phys 2023. [DOI: 10.1016/j.chemphys.2022.111728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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12
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Electronic gap characterization at mesoscopic scale via scanning probe microscopy under ambient conditions. Nat Commun 2022; 13:4648. [PMID: 35941143 PMCID: PMC9359982 DOI: 10.1038/s41467-022-32439-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Accepted: 07/29/2022] [Indexed: 11/08/2022] Open
Abstract
Electronic gaps play an important role in the electric and optical properties of materials. Although various experimental techniques, such as scanning tunnelling spectroscopy and optical or photoemission spectroscopy, are normally used to perform electronic band structure characterizations, it is still challenging to measure the electronic gap at the nanoscale under ambient conditions. Here we report a scanning probe microscopic technique to characterize the electronic gap with nanometre resolution at room temperature and ambient pressure. The technique probes the electronic gap by monitoring the changes of the local quantum capacitance via the Coulomb force at a mesoscopic scale. We showcase this technique by characterizing several 2D semiconductors and van der Waals heterostructures under ambient conditions.
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13
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Kakkar S, Majumdar A, Ahmed T, Parappurath A, Gill NK, Watanabe K, Taniguchi T, Ghosh A. High-Efficiency Infrared Sensing with Optically Excited Graphene-Transition Metal Dichalcogenide Heterostructures. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2202626. [PMID: 35802900 DOI: 10.1002/smll.202202626] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 06/21/2022] [Indexed: 06/15/2023]
Abstract
Binary van der Waals heterostructures of graphene (Gr) and transition metal dichalcogenide (TMDC) have evolved as a promising candidate for photodetection with very high responsivity due to the separation of photo-excited electron-hole pairs across the interface. The spectral range of optoelectronic response in such hybrids has so far been limited by the optical bandgap of the light absorbing TMDC layer. Here, the bidirectionality of interlayer charge transfer is utilized for detecting sub-band gap photons in Gr-TMDC heterostructures. A Gr/MoSe2 heterostructure sequentially driven by visible and near infra-red (NIR) photons is employed, to demonstrate that NIR induced back transfer of charge allows fast and repeatable detection of the low energy photons (less than the optical band gap of the TMDC layer). This mechanism provides photoresponsivity as high as ≈3000 A W-1 close to the communication wavelength. The experiment provides a new strategy for achieving highly efficient photodetection over a broad range of energies beyond the spectral bandgap with the 2D semiconductor family.
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Affiliation(s)
- Saloni Kakkar
- Department of Physics, Indian Institute of Science, Bangalore, 560012, India
| | - Aniket Majumdar
- Department of Physics, Indian Institute of Science, Bangalore, 560012, India
| | - Tanweer Ahmed
- Department of Physics, Indian Institute of Science, Bangalore, 560012, India
| | - Aparna Parappurath
- Department of Physics, Indian Institute of Science, Bangalore, 560012, India
| | | | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Arindam Ghosh
- Department of Physics, Indian Institute of Science, Bangalore, 560012, India
- Center for Nano Science and Engineering, Indian Institute of Science, Bangalore, 560012, India
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14
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Liu Y, Elbanna A, Gao W, Pan J, Shen Z, Teng J. Interlayer Excitons in Transition Metal Dichalcogenide Semiconductors for 2D Optoelectronics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2107138. [PMID: 34700359 DOI: 10.1002/adma.202107138] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 10/13/2021] [Indexed: 06/13/2023]
Abstract
Optoelectronic materials that allow on-chip integrated light signal emitting, routing, modulation, and detection are crucial for the development of high-speed and high-throughput optical communication and computing technologies. Interlayer excitons in 2D van der Waals heterostructures, where electrons and holes are bounded by Coulomb interaction but spatially localized in different 2D layers, have recently attracted intense attention for their enticing properties and huge potential in device applications. Here, a general view of these 2D-confined hydrogen-like bosonic particles and the state-of-the-art developments with respect to the frontier concepts and prototypes is presented. Staggered type-II band alignment enables expansion of the interlayer direct bandgap from the intrinsic visible in monolayers up to the near- or even mid-infrared spectrum. Owing to large exciton binding energy, together with ultralong lifetime, room-temperature exciton devices and observation of quantum behaviors are demonstrated. With the rapid advances, it can be anticipated that future studies of interlayer excitons will not only allow the construction of all-exciton information processing circuits but will also continue to enrich the panoply of ideas on quantum phenomena.
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Affiliation(s)
- Yuanda Liu
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
| | - Ahmed Elbanna
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 637371, Singapore
| | - Weibo Gao
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 637371, Singapore
- The Photonics Institute and Center for Disruptive Photonic Technologies, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
| | - Jisheng Pan
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
| | - Zexiang Shen
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 637371, Singapore
- The Photonics Institute and Center for Disruptive Photonic Technologies, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
| | - Jinghua Teng
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
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15
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Bieniek M, Sadecka K, Szulakowska L, Hawrylak P. Theory of Excitons in Atomically Thin Semiconductors: Tight-Binding Approach. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:1582. [PMID: 35564291 PMCID: PMC9104105 DOI: 10.3390/nano12091582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Revised: 04/24/2022] [Accepted: 04/26/2022] [Indexed: 02/01/2023]
Abstract
Atomically thin semiconductors from the transition metal dichalcogenide family are materials in which the optical response is dominated by strongly bound excitonic complexes. Here, we present a theory of excitons in two-dimensional semiconductors using a tight-binding model of the electronic structure. In the first part, we review extensive literature on 2D van der Waals materials, with particular focus on their optical response from both experimental and theoretical points of view. In the second part, we discuss our ab initio calculations of the electronic structure of MoS2, representative of a wide class of materials, and review our minimal tight-binding model, which reproduces low-energy physics around the Fermi level and, at the same time, allows for the understanding of their electronic structure. Next, we describe how electron-hole pair excitations from the mean-field-level ground state are constructed. The electron-electron interactions mix the electron-hole pair excitations, resulting in excitonic wave functions and energies obtained by solving the Bethe-Salpeter equation. This is enabled by the efficient computation of the Coulomb matrix elements optimized for two-dimensional crystals. Next, we discuss non-local screening in various geometries usually used in experiments. We conclude with a discussion of the fine structure and excited excitonic spectra. In particular, we discuss the effect of band nesting on the exciton fine structure; Coulomb interactions; and the topology of the wave functions, screening and dielectric environment. Finally, we follow by adding another layer and discuss excitons in heterostructures built from two-dimensional semiconductors.
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Affiliation(s)
- Maciej Bieniek
- Department of Physics, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (K.S.); (L.S.); (P.H.)
- Department of Theoretical Physics, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
- Institut für Theoretische Physik und Astrophysik, Universität Würzburg, 97074 Würzburg, Germany
| | - Katarzyna Sadecka
- Department of Physics, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (K.S.); (L.S.); (P.H.)
- Department of Theoretical Physics, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
| | - Ludmiła Szulakowska
- Department of Physics, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (K.S.); (L.S.); (P.H.)
| | - Paweł Hawrylak
- Department of Physics, University of Ottawa, Ottawa, ON K1N 6N5, Canada; (K.S.); (L.S.); (P.H.)
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16
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Pogosov AG, Shevyrin AA, Pokhabov DA, Zhdanov EY, Kumar S. Suspended semiconductor nanostructures: physics and technology. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:263001. [PMID: 35477698 DOI: 10.1088/1361-648x/ac6308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Accepted: 03/31/2022] [Indexed: 06/14/2023]
Abstract
The current state of research on quantum and ballistic electron transport in semiconductor nanostructures with a two-dimensional electron gas separated from the substrate and nanoelectromechanical systems is reviewed. These nanostructures fabricated using the surface nanomachining technique have certain unexpected features in comparison to their non-suspended counterparts, such as additional mechanical degrees of freedom, enhanced electron-electron interaction and weak heat sink. Moreover, their mechanical functionality can be used as an additional tool for studying the electron transport, complementary to the ordinary electrical measurements. The article includes a comprehensive review of spin-dependent electron transport and multichannel effects in suspended quantum point contacts, ballistic and adiabatic transport in suspended nanostructures, as well as investigations on nanoelectromechanical systems. We aim to provide an overview of the state-of-the-art in suspended semiconductor nanostructures and their applications in nanoelectronics, spintronics and emerging quantum technologies.
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Affiliation(s)
- A G Pogosov
- Rzhanov Institute of Semiconductor Physics SB RAS, 13 Lavrentiev Ave., Novosibirsk 630090, Russia
- Department of Physics, Novosibirsk State University, 2 Pirogov Str., Novosibirsk 630090, Russia
| | - A A Shevyrin
- Rzhanov Institute of Semiconductor Physics SB RAS, 13 Lavrentiev Ave., Novosibirsk 630090, Russia
| | - D A Pokhabov
- Rzhanov Institute of Semiconductor Physics SB RAS, 13 Lavrentiev Ave., Novosibirsk 630090, Russia
- Department of Physics, Novosibirsk State University, 2 Pirogov Str., Novosibirsk 630090, Russia
| | - E Yu Zhdanov
- Rzhanov Institute of Semiconductor Physics SB RAS, 13 Lavrentiev Ave., Novosibirsk 630090, Russia
- Department of Physics, Novosibirsk State University, 2 Pirogov Str., Novosibirsk 630090, Russia
| | - S Kumar
- Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom
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17
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Wadhwa R, Ghosh A, Kumar D, Kumar P, Kumar M. Platinum nanoparticle sensitized plasmonic-enhanced broad spectral photodetection in large area vertical-aligned MoS 2flakes. NANOTECHNOLOGY 2022; 33:255702. [PMID: 35297382 DOI: 10.1088/1361-6528/ac5e85] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 03/16/2022] [Indexed: 06/14/2023]
Abstract
2D MoS2holds immense potential for electronic and optoelectronic applications due to its unique characteristics. However, the atomic-scale thickness of MoS2hinders the optical absorbance, thereby limiting its photodetection capability. Vertically-aligned MoS2(VA-MoS2) has an advantage of strong optical absorption and quick intra-layer transport, offering high speed operation. The coupling of plasmonic metal nanostructure with MoS2can further enhance the light-matter interaction. Pt/Pd (as opposed to Ag/Au) are more promising to design next-generation nano-plasmonic devices due to their intense interband activity over a broad spectral range. Herein, we report Pt nanoparticle (NPs) enhanced broadband photoresponse in VA-MoS2. The optical absorbance of MoS2is enhanced after the integration of Pt NPs, with a four-fold enhancement in photocurrent. The formation of Schottky junction at Pt-MoS2interface inhibits electron transmission, suppressing the dark current and substantially reducing NEP. The plasmonic-enabled photodetector shows enhanced responsivity (432 A W-1, 800 nm) and detectivity (1.85 × 1014Jones, 5 V) with a low response time (87 ms/84 ms), attributed to faster carrier transport. Additionally, a theoretical approach is adopted to calculate wavelength-dependent responsivity, which matches well with experimental results. These findings offer a facile approach to modulate the performance of next-generation optoelectronic devices for practical applications.
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Affiliation(s)
- Riya Wadhwa
- Functional and Renewable Energy Materials Laboratory, Department of Physics, Indian Institute of Technology Ropar, Rupnagar, Punjab-140001, India
| | - Anupam Ghosh
- Functional and Renewable Energy Materials Laboratory, Department of Physics, Indian Institute of Technology Ropar, Rupnagar, Punjab-140001, India
| | - Deepu Kumar
- Indian Institute of Technology Mandi, Himachal Pradesh-175005, India
| | - Pradeep Kumar
- Indian Institute of Technology Mandi, Himachal Pradesh-175005, India
| | - Mukesh Kumar
- Functional and Renewable Energy Materials Laboratory, Department of Physics, Indian Institute of Technology Ropar, Rupnagar, Punjab-140001, India
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18
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Jung E, Park JC, Seo YS, Kim JH, Hwang J, Lee YH. Unusually large exciton binding energy in multilayered 2H-MoTe 2. Sci Rep 2022; 12:4543. [PMID: 35296786 PMCID: PMC8927107 DOI: 10.1038/s41598-022-08692-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 12/23/2021] [Indexed: 11/15/2022] Open
Abstract
Although large exciton binding energies of typically 0.6–1.0 eV are observed for monolayer transition metal dichalcogenides (TMDs) owing to strong Coulomb interaction, multilayered TMDs yield relatively low exciton binding energies owing to increased dielectric screening. Recently, the ideal carrier-multiplication threshold energy of twice the bandgap has been realized in multilayered semiconducting 2H-MoTe2 with a conversion efficiency of 99%, which suggests strong Coulomb interaction. However, the origin of strong Coulomb interaction in multilayered 2H-MoTe2, including the exciton binding energy, has not been elucidated to date. In this study, unusually large exciton binding energy is observed through optical spectroscopy conducted on CVD-grown 2H-MoTe2. To extract exciton binding energy, the optical conductivity is fitted using the Lorentz model to describe the exciton peaks and the Tauc–Lorentz model to describe the indirect and direct bandgaps. The exciton binding energy of 4 nm thick multilayered 2H-MoTe2 is approximately 300 meV, which is unusually large by one order of magnitude when compared with other multilayered TMD semiconductors such as 2H-MoS2 or 2H-MoSe2. This finding is interpreted in terms of small exciton radius based on the 2D Rydberg model. The exciton radius of multilayered 2H-MoTe2 resembles that of monolayer 2H-MoTe2, whereas those of multilayered 2H-MoS2 and 2H-MoSe2 are large when compared with monolayer 2H-MoS2 and 2H-MoSe2. From the large exciton binding energy in multilayered 2H-MoTe2, it is expected to realize the future applications such as room-temperature and high-temperature polariton lasing.
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Affiliation(s)
- Eilho Jung
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University (SKKU), Suwon, 16419, Republic of Korea.,Department of Physics, Sungkyunkwan University (SKKU), Suwon, 16419, Republic of Korea
| | - Jin Cheol Park
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University (SKKU), Suwon, 16419, Republic of Korea.,Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, 16419, Republic of Korea
| | - Yu-Seong Seo
- Department of Physics, Sungkyunkwan University (SKKU), Suwon, 16419, Republic of Korea
| | - Ji-Hee Kim
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University (SKKU), Suwon, 16419, Republic of Korea. .,Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, 16419, Republic of Korea.
| | - Jungseek Hwang
- Department of Physics, Sungkyunkwan University (SKKU), Suwon, 16419, Republic of Korea.
| | - Young Hee Lee
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Sungkyunkwan University (SKKU), Suwon, 16419, Republic of Korea. .,Department of Physics, Sungkyunkwan University (SKKU), Suwon, 16419, Republic of Korea. .,Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, 16419, Republic of Korea.
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19
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Tang H, Neupane B, Neupane S, Ruan S, Nepal NK, Ruzsinszky A. Tunable band gaps and optical absorption properties of bent MoS 2 nanoribbons. Sci Rep 2022; 12:3008. [PMID: 35194072 PMCID: PMC8863845 DOI: 10.1038/s41598-022-06741-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Accepted: 02/03/2022] [Indexed: 11/09/2022] Open
Abstract
The large tunability of band gaps and optical absorptions of armchair MoS2 nanoribbons of different widths under bending is studied using density functional theory and many-body perturbation GW and Bethe-Salpeter equation approaches. We find that there are three critical bending curvatures, and the non-edge and edge band gaps generally show a non-monotonic trend with bending. The non-degenerate edge gap splits show an oscillating feature with ribbon width n, with a period [Formula: see text], due to quantum confinement effects. The complex strain patterns on the bent nanoribbons control the varying features of band structures and band gaps that result in varying exciton formations and optical properties. The binding energy and the spin singlet-triplet split of the exciton forming the lowest absorption peak generally decrease with bending curvatures. The large tunability of optical properties of bent MoS2 nanoribbons is promising and will find applications in tunable optoelectronic nanodevices.
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Affiliation(s)
- Hong Tang
- Department of Physics, Temple University, Philadelphia, PA, 19122, USA.
| | - Bimal Neupane
- Department of Physics, Temple University, Philadelphia, PA, 19122, USA
| | - Santosh Neupane
- Department of Physics, Temple University, Philadelphia, PA, 19122, USA
| | - Shiqi Ruan
- Department of Physics, Temple University, Philadelphia, PA, 19122, USA
| | - Niraj K Nepal
- Department of Physics, Temple University, Philadelphia, PA, 19122, USA
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20
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Vaquero D, Salvador-Sánchez J, Clericò V, Diez E, Quereda J. The Low-Temperature Photocurrent Spectrum of Monolayer MoSe2: Excitonic Features and Gate Voltage Dependence. NANOMATERIALS 2022; 12:nano12030322. [PMID: 35159666 PMCID: PMC8838275 DOI: 10.3390/nano12030322] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Revised: 01/11/2022] [Accepted: 01/18/2022] [Indexed: 02/01/2023]
Abstract
Two-dimensional transition metal dichalcogenides (2D-TMDs) are among the most promising materials for exploring and exploiting exciton transitions. Excitons in 2D-TMDs present remarkably long lifetimes, even at room temperature. The spectral response of exciton transitions in 2D-TMDs has been thoroughly characterized over the past decade by means of photoluminescence spectroscopy, transmittance spectroscopy, and related techniques; however, the spectral dependence of their electronic response is still not fully characterized. In this work, we investigate the electronic response of exciton transitions in monolayer MoSe2 via low-temperature photocurrent spectroscopy. We identify the spectral features associated with the main exciton and trion transitions, with spectral bandwidths down to 15 meV. We also investigate the effect of the Fermi level on the position and intensity of excitonic spectral features, observing a very strong modulation of the photocurrent, which even undergoes a change in sign when the Fermi level crosses the charge neutrality point. Our results demonstrate the unexploited potential of low-temperature photocurrent spectroscopy for studying excitons in low-dimensional materials, and provide new insight into excitonic transitions in 1L-MoSe2.
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21
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Kandhasamy DM, Muthu Mareeswaran P, Chellappan S, Namasivayam D, Aldahish A, Chidambaram K. Synthesis and Photoluminescence Properties of MoS 2/Graphene Heterostructure by Liquid-Phase Exfoliation. ACS OMEGA 2022; 7:629-637. [PMID: 35036729 PMCID: PMC8757342 DOI: 10.1021/acsomega.1c05250] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 12/21/2021] [Indexed: 06/14/2023]
Abstract
Here, we report the synthesis of MoS2/graphene heterostructure in single-stage, liquid-phase exfoliation using a 7:3 isopropyl alcohol/water mixture. Further, the synthesized heterostructure was characterized using UV-visible and micro-Raman spectroscopies, transmission electron microscopy (TEM), and dynamic light scattering (DLS) analysis. UV-visible and micro-Raman analyses confirmed that the synthesized heterostructure had mostly few-layered (two-to-four sheets) MoS2. The photophysical properties of the heterostructure were analyzed using steady-state and time-resolved luminescence techniques. Enhanced photoluminescence was observed in the case of the heterostructure probably due to an increase in the defect sites or reduction in the rate of nonradiative decay upon formation of the sandwiched heterostructure. Applications of this heterostructure for fluorescence live-cell imaging were carried out, and the heterostructure demonstrated a better luminescence contrast compared to its individual counterpart MoS2 in phosphate-buffered saline (PBS).
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Affiliation(s)
- Durai Murugan Kandhasamy
- Department
of Bioelectronics and Biosensors, Alagappa
University, Karaikudi 630003, Tamil Nadu, India
| | | | - Selvaraju Chellappan
- National
Centre for Ultrafast Processes, University
of Madras, Taramani Campus, Chennai 600113, India
| | - Dhenadhayalan Namasivayam
- Department
of Chemistry, National Taiwan University and Institute of Atomic and
Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Afaf Aldahish
- Department
of Pharmacology, School of Pharmacy, King
Khalid University, Abha 62529, Saudi Arabia
| | - Kumarappan Chidambaram
- Department
of Pharmacology, School of Pharmacy, King
Khalid University, Abha 62529, Saudi Arabia
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22
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Ma Y, Kalt RA, Stemmer A. Local strain and tunneling current modulate excitonic luminescence in MoS 2 monolayers. RSC Adv 2022; 12:24922-24929. [PMID: 36199876 PMCID: PMC9434384 DOI: 10.1039/d2ra05123k] [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: 08/16/2022] [Accepted: 08/26/2022] [Indexed: 11/21/2022] Open
Abstract
Local strain in monolayer molybdenum disulfide (MoS2) on an evaporated Au surface is studied by scanning tunneling microscopy (STM) induced excitonic luminescence on a length scale of 10 nm.
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Affiliation(s)
- Yalan Ma
- Nanotechnology Group, ETH Zürich, Säumerstrasse 4, Rüschlikon, 8803, Switzerland
| | - Romana Alice Kalt
- Nanotechnology Group, ETH Zürich, Säumerstrasse 4, Rüschlikon, 8803, Switzerland
| | - Andreas Stemmer
- Nanotechnology Group, ETH Zürich, Säumerstrasse 4, Rüschlikon, 8803, Switzerland
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23
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Ji C, Jia H, zhou C, Wang Q, Xue W. Surface plasmon enhancement in the different spatial distributions of nanowire and two-dimensional material. Phys Chem Chem Phys 2022; 24:8296-8302. [DOI: 10.1039/d1cp05982c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Surface plasmon (SP) nanostructures have been widely researched to improve the low light absorption of two-dimensional transition metal dichalcogenides (TMDCs). However, the impact of the different coupling forms of them,...
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24
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Bhardwaj A, Sharma A, Suryanarayana P. Torsional strain engineering of transition metal dichalcogenide nanotubes: an ab initiostudy. NANOTECHNOLOGY 2021; 32:47LT01. [PMID: 34348245 DOI: 10.1088/1361-6528/ac1a90] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Accepted: 08/03/2021] [Indexed: 06/13/2023]
Abstract
We study the effect of torsional deformations on the electronic properties of single-walled transition metal dichalcogenide (TMD) nanotubes. In particular, considering forty-five select armchair and zigzag TMD nanotubes, we perform symmetry-adapted Kohn-Sham density functional theory calculations to determine the variation in bandgap and effective mass of charge carriers with twist. We find that metallic nanotubes remain so even after deformation, whereas semiconducting nanotubes experience a decrease in bandgap with twist-originally direct bandgaps become indirect-resulting in semiconductor to metal transitions. In addition, the effective mass of holes and electrons continuously decrease and increase with twist, respectively, resulting in n-type to p-type semiconductor transitions. We find that this behavior is likely due to rehybridization of orbitals in the metal and chalcogen atoms, rather than charge transfer between them. Overall, torsional deformations represent a powerful avenue to engineer the electronic properties of semiconducting TMD nanotubes, with applications to devices like sensors and semiconductor switches.
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Affiliation(s)
- Arpit Bhardwaj
- College of Engineering, Georgia Institute of Technology, Atlanta, GA 30332, United States of America
| | - Abhiraj Sharma
- College of Engineering, Georgia Institute of Technology, Atlanta, GA 30332, United States of America
| | - Phanish Suryanarayana
- College of Engineering, Georgia Institute of Technology, Atlanta, GA 30332, United States of America
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25
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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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26
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Atthapak C, Ektarawong A, Pakornchote T, Alling B, Bovornratanaraks T. Effect of atomic configuration and spin-orbit coupling on thermodynamic stability and electronic bandgap of monolayer 2H-Mo 1-xW xS 2 solid solutions. Phys Chem Chem Phys 2021; 23:13535-13543. [PMID: 34095934 DOI: 10.1039/d1cp01119g] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Through a combination of density functional theory calculations and cluster-expansion formalism, the effect of the configuration of the transition metal atoms and spin-orbit coupling on the thermodynamic stability and electronic bandgap of monolayer 2H-Mo1-xWxS2 is investigated. Our investigation reveals that, in spite of exhibiting a weak ordering tendency of Mo and W atoms at 0 K, monolayer 2H-Mo1-xWxS2 is thermodynamically stable as a single-phase random solid solution across the entire composition range at temperatures higher than 45 K. The spin-orbit coupling effect, induced mainly by W atoms, is found to have a minimal impact on the mixing thermodynamics of Mo and W atoms in monolayer 2H-Mo1-xWxS2; however, it significantly induces change in the electronic bandgap of the monolayer solid solution. We find that the band-gap energies of ordered and disordered solid solutions of monolayer 2H-Mo1-xWxS2 do not follow Vegard's law. In addition, the degree of the SOC-induced change in band-gap energy of monolayer 2H-Mo1-xWxS2 solid solutions not only depends on the Mo and W contents, but for a given alloy composition it is also affected by the configuration of the Mo and W atoms. This poses a challenge of fine-tuning the bandgap of monolayer 2H-Mo1-xWxS2 in practice just by varying the contents of Mo and W.
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Affiliation(s)
- C Atthapak
- Extreme Conditions Physics Research Laboratory, Physics of Energy Materials Research Unit, Department of Physics, Faculty of Science, Chulalongkorn University, Bangkok, Thailand. and Thailand Center of Excellence in Physics, Ministry of Higher Education, Science, Research and Innovation, 328 Si Ayutthaya Road, Bangkok, 10400, Thailand
| | - A Ektarawong
- Extreme Conditions Physics Research Laboratory, Physics of Energy Materials Research Unit, Department of Physics, Faculty of Science, Chulalongkorn University, Bangkok, Thailand. and Thailand Center of Excellence in Physics, Ministry of Higher Education, Science, Research and Innovation, 328 Si Ayutthaya Road, Bangkok, 10400, Thailand
| | - T Pakornchote
- Extreme Conditions Physics Research Laboratory, Physics of Energy Materials Research Unit, Department of Physics, Faculty of Science, Chulalongkorn University, Bangkok, Thailand. and Thailand Center of Excellence in Physics, Ministry of Higher Education, Science, Research and Innovation, 328 Si Ayutthaya Road, Bangkok, 10400, Thailand
| | - B Alling
- Theoretical Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83, Linköping, Sweden
| | - T Bovornratanaraks
- Extreme Conditions Physics Research Laboratory, Physics of Energy Materials Research Unit, Department of Physics, Faculty of Science, Chulalongkorn University, Bangkok, Thailand. and Thailand Center of Excellence in Physics, Ministry of Higher Education, Science, Research and Innovation, 328 Si Ayutthaya Road, Bangkok, 10400, Thailand
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27
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Taffelli A, Dirè S, Quaranta A, Pancheri L. MoS 2 Based Photodetectors: A Review. SENSORS (BASEL, SWITZERLAND) 2021; 21:2758. [PMID: 33919731 PMCID: PMC8070690 DOI: 10.3390/s21082758] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 03/30/2021] [Accepted: 04/08/2021] [Indexed: 12/16/2022]
Abstract
Photodetectors based on transition metal dichalcogenides (TMDs) have been widely reported in the literature and molybdenum disulfide (MoS2) has been the most extensively explored for photodetection applications. The properties of MoS2, such as direct band gap transition in low dimensional structures, strong light-matter interaction and good carrier mobility, combined with the possibility of fabricating thin MoS2 films, have attracted interest for this material in the field of optoelectronics. In this work, MoS2-based photodetectors are reviewed in terms of their main performance metrics, namely responsivity, detectivity, response time and dark current. Although neat MoS2-based detectors already show remarkable characteristics in the visible spectral range, MoS2 can be advantageously coupled with other materials to further improve the detector performance Nanoparticles (NPs) and quantum dots (QDs) have been exploited in combination with MoS2 to boost the response of the devices in the near ultraviolet (NUV) and infrared (IR) spectral range. Moreover, heterostructures with different materials (e.g., other TMDs, Graphene) can speed up the response of the photodetectors through the creation of built-in electric fields and the faster transport of charge carriers. Finally, in order to enhance the stability of the devices, perovskites have been exploited both as passivation layers and as electron reservoirs.
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Affiliation(s)
- Alberto Taffelli
- Department of Industrial Engineering, University of Trento, Via Sommarive 9, 38123 Trento, Italy; (S.D.); (A.Q.); (L.P.)
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28
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Di Sabatino S, Berger JA, Romaniello P. Optical spectra of 2D monolayers from time-dependent density functional theory. Faraday Discuss 2020; 224:467-482. [PMID: 32940315 DOI: 10.1039/d0fd00073f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The optical spectra of two-dimensional (2D) periodic systems provide a challenge for time-dependent density-functional theory (TDDFT) because of the large excitonic effects in these materials. In this work we explore how accurately these spectra can be described within a pure Kohn-Sham time-dependent density-functional framework, i.e., a framework in which no theory beyond Kohn-Sham density-functional theory, such as GW, is required to correct the Kohn-Sham gap. To achieve this goal we adapted a recent approach we developed for the optical spectra of 3D systems [S. Cavo, J. A. Berger and P. Romaniello, Phys. Rev. B, 2020, 101, 115109] to those of 2D systems. Our approach relies on the link between the exchange-correlation kernel of TDDFT and the derivative discontinuity of ground-state density-functional theory, which guarantees a correct quasi-particle gap, and on a generalization of the polarization functional [J. A. Berger, Phys. Rev. Lett., 2015, 115, 137402], which describes the excitonic effects. We applied our approach to two prototypical 2D monolayers, h-BN and MoS2. We find that our protocol gives a qualitatively good description of the optical spectrum of h-BN, whereas improvements are needed for MoS2 to describe the intensity of the excitonic peaks.
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Affiliation(s)
- S Di Sabatino
- Laboratoire de Physique Théorique, Université de Toulouse, CNRS, UPS, France.
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29
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Wolz L, Heshmatpour C, Perri A, Polli D, Cerullo G, Finley JJ, Thyrhaug E, Hauer J, Stier AV. Time-domain photocurrent spectroscopy based on a common-path birefringent interferometer. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2020; 91:123101. [PMID: 33379948 DOI: 10.1063/5.0023543] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 11/05/2020] [Indexed: 06/12/2023]
Abstract
We present diffraction-limited photocurrent (PC) microscopy in the visible spectral range based on broadband excitation and an inherently phase-stable common-path interferometer. The excellent path-length stability guarantees high accuracy without the need for active feedback or post-processing of the interferograms. We illustrate the capabilities of the setup by recording PC spectra of a bulk GaAs device and compare the results to optical transmission data.
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Affiliation(s)
- Lukas Wolz
- Department of Physics, Technical University of Munich, Walter Schottky Institut, 85748 Garching, Germany
| | - Constantin Heshmatpour
- Dynamical Spectroscopy, Department of Chemistry, Technical University of Munich, 85748 Garching, Germany
| | - Antonio Perri
- IFN-CNR and Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy
| | - Dario Polli
- IFN-CNR and Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy
| | - Giulio Cerullo
- IFN-CNR and Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy
| | - Jonathan J Finley
- Department of Physics, Technical University of Munich, Walter Schottky Institut, 85748 Garching, Germany
| | - Erling Thyrhaug
- Dynamical Spectroscopy, Department of Chemistry, Technical University of Munich, 85748 Garching, Germany
| | - Jürgen Hauer
- Dynamical Spectroscopy, Department of Chemistry, Technical University of Munich, 85748 Garching, Germany
| | - Andreas V Stier
- Department of Physics, Technical University of Munich, Walter Schottky Institut, 85748 Garching, Germany
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30
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Wang T, Li Z, Li Y, Lu Z, Miao S, Lian Z, Meng Y, Blei M, Taniguchi T, Watanabe K, Tongay S, Smirnov D, Zhang C, Shi SF. Giant Valley-Polarized Rydberg Excitons in Monolayer WSe 2 Revealed by Magneto-photocurrent Spectroscopy. NANO LETTERS 2020; 20:7635-7641. [PMID: 32902286 DOI: 10.1021/acs.nanolett.0c03167] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
A strong Coulomb interaction could lead to a strongly bound exciton with high-order excited states, similar to the Rydberg atom. The interaction of giant Rydberg excitons can be engineered for a correlated ordered exciton array with a Rydberg blockade, which is promising for realizing quantum simulation. Monolayer transition metal dichalcogenides, with their greatly enhanced Coulomb interaction, are an ideal platform to host the Rydberg excitons in two dimensions. Here, we employ helicity-resolved magneto-photocurrent spectroscopy to identify Rydberg exciton states up to 11s in monolayer WSe2. Notably, the radius of the Rydberg exciton at 11s can be as large as 214 nm, orders of magnitude larger than the 1s exciton. The giant valley-polarized Rydberg exciton not only provides an exciting platform to study the strong exciton-exciton interaction and nonlinear exciton response but also allows the investigation of the different interplay between the Coulomb interaction and Landau quantization, tunable from a low- to high-magnetic-field limit.
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Affiliation(s)
- Tianmeng Wang
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Zhipeng Li
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Yunmei Li
- Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Zhengguang Lu
- National High Magnetic Field Lab, Tallahassee, Florida 32310, United States
- Department of Physics, Florida State University, Tallahassee, Florida 32306, United States
| | - Shengnan Miao
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Zhen Lian
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Yuze Meng
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Mark Blei
- School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona 85287, United States
| | - Takashi Taniguchi
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Sefaattin Tongay
- School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona 85287, United States
| | - Dmitry Smirnov
- National High Magnetic Field Lab, Tallahassee, Florida 32310, United States
| | - Chuanwei Zhang
- Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Su-Fei Shi
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
- Department of Electrical, Computer & Systems Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
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31
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Afanas'ev VV, Delie G, Houssa M, Shlyakhov I, Stesmans A, Trepalin V. Band alignment at interfaces of two-dimensional materials: internal photoemission analysis. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:413002. [PMID: 32413887 DOI: 10.1088/1361-648x/ab937c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Accepted: 05/15/2020] [Indexed: 06/11/2023]
Abstract
The article overviews experimental results obtained by applying internal photoemission (IPE) spectroscopy methods to characterize electron states in single- or few-monolayer thick two-dimensional materials and at their interfaces. Several conducting (graphene) and semiconducting (transitional metal dichalcogenides MoS2, WS2, MoSe2, and WSe2) films on top of thermal SiO2have been analyzed by IPE, which reveals significant sensitivity of interface band offsets and barriers to the details of the material and interface fabrication, indicating violation of the Schottky-Mott rule. This variability is associated with charges and dipoles formed at the interfaces with van der Waals bonding as opposed to the chemically bonded interfaces of three-dimensional semiconductors and metals. Chemical modification of the underlying SiO2surface is shown to be a significant factor, affecting interface barriers due to violation of the interface electroneutrality.
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Affiliation(s)
- Valery V Afanas'ev
- Laboratory of Semiconductor Physics, Department of Physics and Astronomy, University of Leuven, Belgium
| | - Gilles Delie
- Laboratory of Semiconductor Physics, Department of Physics and Astronomy, University of Leuven, Belgium
| | - Michel Houssa
- Laboratory of Semiconductor Physics, Department of Physics and Astronomy, University of Leuven, Belgium
| | - Ilya Shlyakhov
- Laboratory of Semiconductor Physics, Department of Physics and Astronomy, University of Leuven, Belgium
| | - Andre Stesmans
- Laboratory of Semiconductor Physics, Department of Physics and Astronomy, University of Leuven, Belgium
| | - Vadim Trepalin
- Laboratory of Semiconductor Physics, Department of Physics and Astronomy, University of Leuven, Belgium
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32
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Wang K, Paulus B. Tuning the binding energy of excitons in the MoS 2 monolayer by molecular functionalization and defective engineering. Phys Chem Chem Phys 2020; 22:11936-11942. [PMID: 32409806 DOI: 10.1039/d0cp01239d] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
First-principle calculations within many-body perturbation theory are carried out to investigate the influence of the adsorbed molecules and sulfur (S) defects on the electronic and optical properties of the MoS2 monolayer. The exciton binding energy in the range of 0.05 eV to 1.14 eV is observed as a function of molecular coverage, when NO and 1,3,5-triazin (C3H3N3) are adsorbed on the pristine surface. These results can be explained by the interaction between the exciton and the adsorbed molecule. Furthermore, the combined effect of molecular functionalization and defective doping is studied. Our results show that both the electronic and optical band gaps of the MoS2 monolayer strongly depend on the molecular species and the defective coverage, and can be tuned up to ∼2 eV. This work demonstrates the great potential of controlling the MoS2 monolayer's excitonic properties by molecular functionalization and defective engineering.
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Affiliation(s)
- Kangli Wang
- Institut für Chemie und Biochemie, Freie Universität Berlin, Arnimallee 22, 14195 Berlin, Germany.
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33
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Wang T, Miao S, Li Z, Meng Y, Lu Z, Lian Z, Blei M, Taniguchi T, Watanabe K, Tongay S, Smirnov D, Shi SF. Giant Valley-Zeeman Splitting from Spin-Singlet and Spin-Triplet Interlayer Excitons in WSe 2/MoSe 2 Heterostructure. NANO LETTERS 2020; 20:694-700. [PMID: 31865705 DOI: 10.1021/acs.nanolett.9b04528] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Transition metal dichalcogenides (TMDCs) heterostructure with a type II alignment hosts unique interlayer excitons with the possibility of spin-triplet and spin-singlet states. However, the associated spectroscopy signatures remain elusive, strongly hindering the understanding of the Moiré potential modulation of the interlayer exciton. In this work, we unambiguously identify the spin-singlet and spin-triplet interlayer excitons in the WSe2/MoSe2 heterobilayer with a 60° twist angle through the gate- and magnetic field-dependent photoluminescence spectroscopy. Both the singlet and triplet interlayer excitons show giant valley-Zeeman splitting between the K and K' valleys, a result of the large Landé g-factor of the singlet interlayer exciton and triplet interlayer exciton, which are experimentally determined to be ∼10.7 and ∼15.2, respectively, which is in good agreement with theoretical expectation. The photoluminescence (PL) from the singlet and triplet interlayer excitons show opposite helicities, determined by the atomic registry. Helicity-resolved photoluminescence excitation (PLE) spectroscopy study shows that both singlet and triplet interlayer excitons are highly valley-polarized at the resonant excitation with the valley polarization of the singlet interlayer exciton approaching unity at ∼20 K. The highly valley-polarized singlet and triplet interlayer excitons with giant valley-Zeeman splitting inspire future applications in spintronics and valleytronics.
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Affiliation(s)
- Tianmeng Wang
- Department of Chemical and Biological Engineering , Rensselaer Polytechnic Institute , Troy , New York 12180 , United States
| | - Shengnan Miao
- Department of Chemical and Biological Engineering , Rensselaer Polytechnic Institute , Troy , New York 12180 , United States
| | - Zhipeng Li
- Department of Chemical and Biological Engineering , Rensselaer Polytechnic Institute , Troy , New York 12180 , United States
| | - Yuze Meng
- Department of Chemical and Biological Engineering , Rensselaer Polytechnic Institute , Troy , New York 12180 , United States
| | - Zhengguang Lu
- National High Magnetic Field Lab , Tallahassee , Florida 32310 , United States
- Department of Physics , Florida State University , Tallahassee , Florida 32306 , United States
| | - Zhen Lian
- Department of Chemical and Biological Engineering , Rensselaer Polytechnic Institute , Troy , New York 12180 , United States
| | - Mark Blei
- School for Engineering of Matter, Transport and Energy , Arizona State University , Tempe , Arizona 85287 , United States
| | - Takashi Taniguchi
- National Institute for Materials Science , 1-1 Namiki , Tsukuba 305-0044 , Japan
| | - Kenji Watanabe
- National Institute for Materials Science , 1-1 Namiki , Tsukuba 305-0044 , Japan
| | - Sefaattin Tongay
- National Institute for Materials Science , 1-1 Namiki , Tsukuba 305-0044 , Japan
| | - Dmitry Smirnov
- National High Magnetic Field Lab , Tallahassee , Florida 32310 , United States
| | - Su-Fei Shi
- Department of Chemical and Biological Engineering , Rensselaer Polytechnic Institute , Troy , New York 12180 , United States
- Department of Electrical, Computer, and Systems Engineering , Rensselaer Polytechnic Institute , Troy , New York 12180 , United States
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34
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Wang Y, Zhang L, Su C, Xiao H, Lv S, Zhang F, Sui Q, Jia L, Jiang M. Direct Observation of Monolayer MoS 2 Prepared by CVD Using In-Situ Differential Reflectance Spectroscopy. NANOMATERIALS 2019; 9:nano9111640. [PMID: 31752275 PMCID: PMC6915464 DOI: 10.3390/nano9111640] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 11/02/2019] [Accepted: 11/03/2019] [Indexed: 11/16/2022]
Abstract
The in-situ observation is of great significance to the study of the growth mechanism and controllability of two-dimensional transition metal dichalcogenides (TMDCs). Here, the differential reflectance spectroscopy (DRS) was performed to monitor the growth of molybdenum disulfide (MoS2) on a SiO2/Si substrate prepared by chemical vapor deposition (CVD). A home-built in-situ DRS setup was applied to monitor the growth of MoS2 in-situ. The formation and evolution of monolayer MoS2 are revealed by differential reflectance (DR) spectra. The morphology, vibration mode, absorption characteristics and thickness of monolayer MoS2 have been confirmed by optical microscopy, Raman spectroscopy, ex-situ DR spectra, and atomic force microscopy (AFM) respectively. The results demonstrated that DRS was a powerful tool for in-situ observations and has great potential for growth mechanism and controllability of TMDCs prepared by CVD. To the best of the authors' knowledge, it was the first report in which the CVD growth of two-dimensional TMDCs has been investigated in-situ by reflectance spectroscopy.
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Affiliation(s)
- Yina Wang
- School of Control Science and Engineering, Shandong University, Jinan 250061, China; (Y.W.); (C.S.); (H.X.); (F.Z.); (Q.S.); (L.J.); (M.J.)
| | - Lei Zhang
- School of Control Science and Engineering, Shandong University, Jinan 250061, China; (Y.W.); (C.S.); (H.X.); (F.Z.); (Q.S.); (L.J.); (M.J.)
- Correspondence:
| | - Chenhui Su
- School of Control Science and Engineering, Shandong University, Jinan 250061, China; (Y.W.); (C.S.); (H.X.); (F.Z.); (Q.S.); (L.J.); (M.J.)
| | - Hang Xiao
- School of Control Science and Engineering, Shandong University, Jinan 250061, China; (Y.W.); (C.S.); (H.X.); (F.Z.); (Q.S.); (L.J.); (M.J.)
| | - Shanshan Lv
- Institute of Marine Science and Technology, Shandong University, Qingdao 266237, China;
| | - Faye Zhang
- School of Control Science and Engineering, Shandong University, Jinan 250061, China; (Y.W.); (C.S.); (H.X.); (F.Z.); (Q.S.); (L.J.); (M.J.)
| | - Qingmei Sui
- School of Control Science and Engineering, Shandong University, Jinan 250061, China; (Y.W.); (C.S.); (H.X.); (F.Z.); (Q.S.); (L.J.); (M.J.)
| | - Lei Jia
- School of Control Science and Engineering, Shandong University, Jinan 250061, China; (Y.W.); (C.S.); (H.X.); (F.Z.); (Q.S.); (L.J.); (M.J.)
- Institute of Marine Science and Technology, Shandong University, Qingdao 266237, China;
| | - Mingshun Jiang
- School of Control Science and Engineering, Shandong University, Jinan 250061, China; (Y.W.); (C.S.); (H.X.); (F.Z.); (Q.S.); (L.J.); (M.J.)
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Potential modulations in flatland: near-infrared sensitization of MoS 2 phototransistors by a solvatochromic dye directly tethered to sulfur vacancies. Sci Rep 2019; 9:16682. [PMID: 31723200 PMCID: PMC6853947 DOI: 10.1038/s41598-019-53186-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Accepted: 10/24/2019] [Indexed: 12/03/2022] Open
Abstract
Near-infrared sensitization of monolayer MoS2 is here achieved via the covalent attachment of a novel heteroleptic nickel bis-dithiolene complex into sulfur vacancies in the MoS2 structure. Photocurrent action spectroscopy of the sensitized films reveals a discreet contribution from the sensitizer dye centred around 1300 nm (0.95 eV), well below the bandgap of MoS2 (2.1 eV), corresponding to the excitation of the monoanionic dithiolene complex. A mechanism of conductivity enhancement is proposed based on a photo-induced flattening of the corrugated energy landscape present at sulfur vacancy defect sites within the MoS2 due to a dipole change within the dye molecule upon photoexcitation. This method of sensitization might be readily extended to other functional molecules that can impart a change to the dielectric environment at the MoS2 surface under stimulation, thereby extending the breadth of detector applications for MoS2 and other transition metal dichalcogenides.
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36
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Lee H, Deshmukh S, Wen J, Costa VZ, Schuder JS, Sanchez M, Ichimura AS, Pop E, Wang B, Newaz AKM. Layer-Dependent Interfacial Transport and Optoelectrical Properties of MoS 2 on Ultraflat Metals. ACS APPLIED MATERIALS & INTERFACES 2019; 11:31543-31550. [PMID: 31364836 DOI: 10.1021/acsami.9b09868] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Layered materials based on transition-metal dichalcogenides (TMDs) are promising for a wide range of electronic and optoelectronic devices. Realizing such practical applications often requires metal-TMD connections or contacts. Hence, a complete understanding of electronic band alignments and potential barrier heights governing the transport through metal-TMD junctions is critical. However, it is presently unclear how the energy bands of a TMD align while in contact with a metal as a function of the number of layers. In pursuit of removing this knowledge gap, we have performed conductive atomic force microscopy (CAFM) of few-layered (1 to 5 layers) MoS2 immobilized on ultraflat conducting Au surfaces [root-mean-square (rms) surface roughness < 0.2 nm] and indium-tin oxide (ITO) substrates (rms surface roughness < 0.7 nm) forming a vertical metal (CAFM tip)-semiconductor-metal device. We have observed that the current increases with the number of layers up to five layers. By applying Fowler-Nordheim tunneling theory, we have determined the barrier heights for different layers and observed how this barrier decreases as the number of layers increases. Using density functional theory calculations, we successfully demonstrated that the barrier height decreases as the layer number increases. By illuminating TMDs on a transparent ultraflat conducting ITO substrate, we observed a reduction in current when compared to the current measured in the dark, hence demonstrating negative photoconductivity. Our study provides a fundamental understanding of the local electronic and optoelectronic behaviors of the TMD-metal junction, which depends on the numbers of TMD layers and may pave an avenue toward developing nanoscale electronic devices with tailored layer-dependent transport properties.
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Affiliation(s)
| | | | - Jing Wen
- School of Chemical, Biological and Materials Engineering , University of Oklahoma , Norman , Oklahoma 73019 , United States
- Key Laboratory for Photonic and Electronic Bandgap Materials, Ministry of Education, School of Physics and Electronic Engineering , Harbin Normal University , Harbin 150025 , P. R. China
| | | | | | | | | | | | - Bin Wang
- School of Chemical, Biological and Materials Engineering , University of Oklahoma , Norman , Oklahoma 73019 , United States
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Kim RH, Leem J, Muratore C, Nam S, Rao R, Jawaid A, Durstock M, McConney M, Drummy L, Rai R, Voevodin A, Glavin N. Photonic crystallization of two-dimensional MoS 2 for stretchable photodetectors. NANOSCALE 2019; 11:13260-13268. [PMID: 31197304 DOI: 10.1039/c9nr02173f] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Low temperature synthesis of high quality two-dimensional (2D) materials directly on flexible substrates remains a fundamental limitation towards scalable realization of robust flexible electronics possessing the unique physical properties of atomically thin structures. Herein, we describe room temperature sputtering of uniform, stoichiometric amorphous MoS2 and subsequent large area (>6.25 cm2) photonic crystallization of 5 nm 2H-MoS2 films in air to enable direct, scalable fabrication of ultrathin 2D photodetectors on stretchable polydimethylsiloxane (PDMS) substrates. The lateral photodetector devices demonstrate an average responsivity of 2.52 μW A-1 and a minimum response time of 120 ms under 515.6 nm illumination. Additionally, the surface wrinkled, or buckled, PDMS substrate with conformal MoS2 retained the photoconductive behavior at tensile strains as high as 5.72% and over 1000 stretching cycles. The results indicate that the photonic crystallization method provides a significant advancement in incorporating high quality semiconducting 2D materials applied directly on polymer substrates for wearable and flexible electronic systems.
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Affiliation(s)
- Richard Hahnkee Kim
- Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson AFB, OH 45433, USA. and National Research Council, Washington, D.C. 20418, USA
| | - Juyoung Leem
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | | | - SungWoo Nam
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Rahul Rao
- Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson AFB, OH 45433, USA. and UES, Inc., Dayton, OH 45432, USA
| | - Ali Jawaid
- Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson AFB, OH 45433, USA. and UES, Inc., Dayton, OH 45432, USA
| | - Michael Durstock
- Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson AFB, OH 45433, USA.
| | - Michael McConney
- Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson AFB, OH 45433, USA.
| | - Lawrence Drummy
- Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson AFB, OH 45433, USA.
| | - Rachel Rai
- Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson AFB, OH 45433, USA. and University of Dayton, Dayton, OH 45409, USA
| | - Andrey Voevodin
- Department of Materials Science and Engineering, University of North Texas, Denton, TX 76203, USA
| | - Nicholas Glavin
- Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson AFB, OH 45433, USA.
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38
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In-plane Aligned Colloidal 2D WS 2 Nanoflakes for Solution-Processable Thin Films with High Planar Conductivity. Sci Rep 2019; 9:9002. [PMID: 31227748 PMCID: PMC6588575 DOI: 10.1038/s41598-019-45192-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 05/29/2019] [Indexed: 11/23/2022] Open
Abstract
Two-dimensional transition-metal dichalcolgenides (2D-TMDs) are among the most intriguing materials for next-generation electronic and optoelectronic devices. Albeit still at the embryonic stage, building thin films by manipulating and stacking preformed 2D nanosheets is now emerging as a practical and cost-effective bottom-up paradigm to obtain excellent electrical properties over large areas. Herein, we exploit the ultrathin morphology and outstanding solution stability of 2D WS2 colloidal nanocrystals to make thin films of TMDs assembled on a millimetre scale by a layer-by-layer deposition approach. We found that a room-temperature surface treatment with a superacid, performed with the precise scope of removing the native insulating surfactants, promotes in-plane assembly of the colloidal WS2 nanoflakes into stacks parallel to the substrate, along with healing of sulphur vacancies in the lattice that are detrimental to electrical conductivity. The as-obtained 2D WS2 thin films, characterized by a smooth and compact morphology, feature a high planar conductivity of up to 1 μS, comparable to the values reported for epitaxially grown WS2 monolayers, and enable photocurrent generation upon light irradiation over a wide range of visible to near-infrared frequencies.
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Gusakova J, Tay BK, Gusakov V. First-Principles Study of Structural and Electronic Properties of MoS1.5Se0.5 Alloy. INTERNATIONAL JOURNAL OF NANOSCIENCE 2019. [DOI: 10.1142/s0219581x19400064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The effects of relative positions of Se atoms in a monomolecular layer of MoS[Formula: see text]Se[Formula: see text] have been studied. It is demonstrated that the distribution of Se atoms between top and bottom chalcogen planes is most energetically favorable. For a more probable distribution of Se atoms this monolayer alloy is a direct semiconductor with the fundamental bandgap of 2.35[Formula: see text]eV. We have also evaluated the optical band gaps of the alloy at 77[Formula: see text]K (1.86[Formula: see text]eV) and room temperature (1.80[Formula: see text]eV), which are in a good agreement with the experimentally measured bandgap of 1.79[Formula: see text]eV.
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Affiliation(s)
- J. Gusakova
- Novitas Center, Nanyang Technological University, 50 Nanyang Ave., 639798 Singapore, Singapore
| | - B. K. Tay
- CINTRA UMI CNRS/NTU/THALES, 50 Nanyang Drive, 637553 Singapore, Singapore
| | - V. Gusakov
- Scientific-Practical Materials Research Center of NASB, P. Browka Str. 19, 220072 Minsk, Belarus
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Zheng YJ, Chen Y, Huang YL, Gogoi PK, Li MY, Li LJ, Trevisanutto PE, Wang Q, Pennycook SJ, Wee ATS, Quek SY. Point Defects and Localized Excitons in 2D WSe 2. ACS NANO 2019; 13:6050-6059. [PMID: 31074961 DOI: 10.1021/acsnano.9b02316] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Identifying the point defects in 2D materials is important for many applications. Recent studies have proposed that W vacancies are the predominant point defect in 2D WSe2, in contrast to theoretical studies, which predict that chalcogen vacancies are the most likely intrinsic point defects in transition metal dichalcogenide semiconductors. We show using first-principles calculations, scanning tunneling microscopy (STM), and scanning transmission electron microscopy experiments that W vacancies are not present in our CVD-grown 2D WSe2. We predict that O-passivated Se vacancies (OSe) and O interstitials (Oins) are present in 2D WSe2, because of facile O2 dissociation at Se vacancies or due to the presence of WO3 precursors in CVD growth. These defects give STM images in good agreement with experiment. The optical properties of point defects in 2D WSe2 are important because single-photon emission (SPE) from 2D WSe2 has been observed experimentally. While strain gradients funnel the exciton in real space, point defects are necessary for the localization of the exciton at length scales that enable photons to be emitted one at a time. Using state-of-the-art GW-Bethe-Salpeter-equation calculations, we predict that only Oins defects give localized excitons within the energy range of SPE in previous experiments, making them a likely source of previously observed SPE. No other point defects (OSe, Se vacancies, W vacancies, and SeW antisites) give localized excitons in the same energy range. Our predictions suggest ways to realize SPE in related 2D materials and point experimentalists toward other energy ranges for SPE in 2D WSe2.
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Affiliation(s)
- Yu Jie Zheng
- Department of Physics , National University of Singapore , 2 Science Drive 3 , 117542 , Singapore
- Centre for Advanced 2D Materials , National University of Singapore , Block S14, Level 6, 6 Science Drive 2 , 117546 , Singapore
| | - Yifeng Chen
- Centre for Advanced 2D Materials , National University of Singapore , Block S14, Level 6, 6 Science Drive 2 , 117546 , Singapore
| | - Yu Li Huang
- Department of Physics , National University of Singapore , 2 Science Drive 3 , 117542 , Singapore
- Institute of Materials Research & Engineering (IMRE) , A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way , Innovis , 138634 , Singapore
| | - Pranjal Kumar Gogoi
- Department of Physics , National University of Singapore , 2 Science Drive 3 , 117542 , Singapore
| | - Ming-Yang Li
- Physical Sciences and Engineering , King Abdullah University of Science and Technology , Thuwal , 23955-6900 , Saudi Arabia
| | - Lain-Jong Li
- Physical Sciences and Engineering , King Abdullah University of Science and Technology , Thuwal , 23955-6900 , Saudi Arabia
| | - Paolo E Trevisanutto
- Centre for Advanced 2D Materials , National University of Singapore , Block S14, Level 6, 6 Science Drive 2 , 117546 , Singapore
| | - Qixing Wang
- Department of Physics , National University of Singapore , 2 Science Drive 3 , 117542 , Singapore
| | - Stephen J Pennycook
- Department of Materials Science & Engineering , National University of Singapore , 9 Engineering Drive 1 , 117575 , Singapore
| | - Andrew T S Wee
- Department of Physics , National University of Singapore , 2 Science Drive 3 , 117542 , Singapore
- Centre for Advanced 2D Materials , National University of Singapore , Block S14, Level 6, 6 Science Drive 2 , 117546 , Singapore
| | - Su Ying Quek
- Department of Physics , National University of Singapore , 2 Science Drive 3 , 117542 , Singapore
- Centre for Advanced 2D Materials , National University of Singapore , Block S14, Level 6, 6 Science Drive 2 , 117546 , Singapore
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Electrical control of spatial resolution in mixed-dimensional heterostructured photodetectors. Proc Natl Acad Sci U S A 2019; 116:6586-6593. [PMID: 30890635 PMCID: PMC6452663 DOI: 10.1073/pnas.1817229116] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Low-dimensional nanomaterials, such as one-dimensional (1D) nanomaterials and layered 2D materials, have exhibited significance for their respective unique electronic and optoelectronic properties. Here we show that a mixed-dimensional heterostructure with building blocks from multiple dimensions will present a synergistic effect on photodetection. A carbon nanotube (CNT)-[Formula: see text]-graphene photodetector is representative on this issue. Its spatial resolution can be electrically switched between high-resolution mode (HRM) and low-resolution mode (LRM) revealed by scanning photocurrent microscopy (SPCM). The reconfigurable spatial resolution can be attributed to the asymmetric geometry and the gate-tunable Fermi levels of these low-dimensional materials. Significantly, an interference fringe with 334 nm in period was successfully discriminated by the device working at HRM, confirming the efficient electrical control. Electrical control of spatial resolution in CNT-[Formula: see text]-graphene devices reveals the potential of the mixed-dimensional architectures in future nanoelectronics and nano-optoelectronics.
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Zhang JZ, Ma JZ. Two-dimensional excitons in monolayer transition metal dichalcogenides from radial equation and variational calculations. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:105702. [PMID: 30664498 DOI: 10.1088/1361-648x/aaf8c5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Exciton energy spectra of monolayer transition metal dichalcogenides (TMDs) in various dielectric environments are studied with an effective mass model using the Keldysh potential for the screened electron-hole interaction. Two-dimensional (2D) excitons are calculated by solving a radial equation (RE) with a shooting method, using boundary conditions that are derived by applying the asymptotic properties of the Keldysh potential. For any given main quantum number n, the exciton Bohr orbit shrinks as [Formula: see text] becomes larger (m is the orbital quantum number) resulting in increased strength of the electron-hole interaction and a decrease of the exciton energy. Further, both the exciton energy and its effective radius decrease linearly with [Formula: see text]. The screened hydrogen model (SHM) (Olsen et al 2016 Phys. Rev. Lett. 116 056401) is examined by comparing its exciton energy spectra with our RE solutions. While the SHM is found to describe the nonhydrogenic exciton Rydberg series (i.e. the energy's dependence on n) reasonably well, it fails to account for the linear dependence of the exciton energy on the orbital quantum number. The exciton effective radius expression of the SHM can characterize the exciton radius's dependence on n, but it cannot properly describe the exciton radius's dependence on m, which is the cause of the SHM's poor description of the exciton energy's m-dependence. Analytical variational wave-functions are constructed with the 2D hydrogenic wave-functions for a number of strongly bound exciton states, and very close exciton energies and wave-functions are obtained with the variational method and the RE solution (exciton energies are within a 6% of deviation). The variational wave-functions are further applied to study the Stark effects in 2D TMDs, with an analytical expression derived for evaluating the redshift the ground state energy.
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Affiliation(s)
- J-Z Zhang
- School of Physics, Jilin University, Changchun 130012, People's Republic of China
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43
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Lu D, Zhou Q, Li F, Li X, Lu G. Influence of interlayer interactions on the relaxation dynamics of excitons in ultrathin MoS 2. NANOSCALE ADVANCES 2019; 1:1186-1192. [PMID: 36133182 PMCID: PMC9473163 DOI: 10.1039/c8na00086g] [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: 07/12/2018] [Accepted: 12/17/2018] [Indexed: 06/16/2023]
Abstract
Interlayer interactions play a crucial role in modifying the optical and electronic properties of layered materials in a complex way, which is of key importance for the performance of the optoelectronic devices based on these novel materials. In this contribution, we performed an investigation into the underlying influence of interlayer interactions on the relaxation dynamics of excitons in ultrathin MoS2 using the femtosecond transient absorption spectroscopy technique. The experimental results manifest that interlayer interactions in bilayer MoS2 can largely facilitate the exciton-phonon scattering process and inhibit the radiative recombination process, which consequently accelerates the relaxation rate of A excitons and results in the decrease of the relaxation lifetime of A excitons in bilayer MoS2.
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Affiliation(s)
- Dongxiao Lu
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University Changchun 130012 China
- State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University 2699 Qianjin Street Changchun 130012 China
| | - Qiang Zhou
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University Changchun 130012 China
| | - Fangfei Li
- State Key Laboratory of Superhard Materials, College of Physics, Jilin University Changchun 130012 China
| | - Xiaowei Li
- Center for Advanced Optoelectronic Functional Materials Research, Key Laboratory of UV-Emitting Materials and Technology, Northeast Normal University, Ministry of Education 5268 Renmin Street Changchun 130024 China
| | - Geyu Lu
- State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University 2699 Qianjin Street Changchun 130012 China
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Neupane GP, Zhou K, Chen S, Yildirim T, Zhang P, Lu Y. In-Plane Isotropic/Anisotropic 2D van der Waals Heterostructures for Future Devices. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2019; 15:e1804733. [PMID: 30714302 DOI: 10.1002/smll.201804733] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Revised: 12/27/2018] [Indexed: 06/09/2023]
Abstract
Mono- to few-layers of 2D semiconducting materials have uniquely inherent optical, electronic, and magnetic properties that make them ideal for probing fundamental scientific phenomena up to the 2D quantum limit and exploring their emerging technological applications. This Review focuses on the fundamental optoelectronic studies and potential applications of in-plane isotropic/anisotropic 2D semiconducting heterostructures. Strong light-matter interaction, reduced dimensionality, and dielectric screening in mono- to few-layers of 2D semiconducting materials result in strong many-body interactions, leading to the formation of robust quasiparticles such as excitons, trions, and biexcitons. An in-plane isotropic nature leads to the quasi-2D particles, whereas, an anisotropic nature leads to quasi-1D particles. Hence, in-plane isotropic/anisotropic 2D heterostructures lead to the formation of quasi-1D/2D particle systems allowing for the manipulation of high binding energy quasi-1D particle populations for use in a wide variety of applications. This Review emphasizes an exciting 1D-2D particles dynamic in such heterostructures and their potential for high-performance photoemitters and exciton-polariton lasers. Moreover, their scopes are also broadened in thermoelectricity, piezoelectricity, photostriction, energy storage, hydrogen evolution reactions, and chemical sensor fields. The unique in-plane isotropic/anisotropic 2D heterostructures may open the possibility of engineering smart devices in the nanodomain with complex opto-electromechanical functions.
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Affiliation(s)
- Guru Prakash Neupane
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, 518052, Guangdong, China
- Research School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT, 2601, Australia
| | - Kai Zhou
- College of Mechatronics and Control Engineering, Shenzhen University, Nan-hai Ave 3688, Shenzhen, 518060, Guangdong, China
| | - Songsong Chen
- College of Mechatronics and Control Engineering, Shenzhen University, Nan-hai Ave 3688, Shenzhen, 518060, Guangdong, China
| | - Tanju Yildirim
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, 518052, Guangdong, China
| | - Peixin Zhang
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, 518052, Guangdong, China
| | - Yuerui Lu
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, 518052, Guangdong, China
- Research School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT, 2601, Australia
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Bataller AW, Younts RA, Rustagi A, Yu Y, Ardekani H, Kemper A, Cao L, Gundogdu K. Dense Electron-Hole Plasma Formation and Ultralong Charge Lifetime in Monolayer MoS 2 via Material Tuning. NANO LETTERS 2019; 19:1104-1111. [PMID: 30608697 DOI: 10.1021/acs.nanolett.8b04408] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Many-body interactions in photoexcited semiconductors can bring about strongly interacting electronic states, culminating in the fully ionized matter of electron-hole plasma (EHP) and electron-hole liquid (EHL). These exotic phases exhibit unique electronic properties, such as metallic conductivity and metastable high photoexcitation density, which can be the basis for future transformative applications. However, the cryogenic condition required for its formation has limited the study of dense plasma phases to a purely academic pursuit in a restricted parameter space. This paradigm can potentially change with the recent experimental observation of these phases in atomically thin MoS2 and MoTe2 at room temperature. A fundamental understanding of EHP and EHL dynamics is critical for developing novel applications on this versatile layered platform. In this work, we studied the formation and dissipation of EHP in monolayer MoS2. Unlike previous results in bulk semiconductors, our results reveal that electromechanical material changes in monolayer MoS2 during photoexcitation play a significant role in dense EHP formation. Within the free-standing geometry, photoexcitation is accompanied by an unconstrained thermal expansion, resulting in a direct-to-indirect gap electronic transition at a critical lattice spacing and fluence. This dramatic altering of the material's energetic landscape extends carrier lifetimes by 2 orders of magnitude and allows the density required for EHP formation. The result is a stable dense plasma state that is sustained with modest optical photoexcitation. Our findings pave the way for novel applications based on dense plasma states in two-dimensional semiconductors.
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Affiliation(s)
- Alexander W Bataller
- Department of Physics , North Carolina State University , Raleigh , North Carolina 27695 , United States
| | - Robert A Younts
- Department of Physics , North Carolina State University , Raleigh , North Carolina 27695 , United States
| | - Avinash Rustagi
- Department of Physics , North Carolina State University , Raleigh , North Carolina 27695 , United States
| | - Yiling Yu
- Department of Materials Science and Engineering , North Carolina State University , Raleigh , North Carolina 27695 , United States
| | - Hossein Ardekani
- Department of Physics , North Carolina State University , Raleigh , North Carolina 27695 , United States
| | - Alexander Kemper
- Department of Physics , North Carolina State University , Raleigh , North Carolina 27695 , United States
| | - Linyou Cao
- Department of Materials Science and Engineering , North Carolina State University , Raleigh , North Carolina 27695 , United States
| | - Kenan Gundogdu
- Department of Physics , North Carolina State University , Raleigh , North Carolina 27695 , United States
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Guo Y, Wu Q, Li Y, Lu N, Mao K, Bai Y, Zhao J, Wang J, Zeng XC. Copper(i) sulfide: a two-dimensional semiconductor with superior oxidation resistance and high carrier mobility. NANOSCALE HORIZONS 2019; 4:223-230. [PMID: 32254160 DOI: 10.1039/c8nh00216a] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Two-dimensional (2D) semiconductors with suitable direct band gaps, high carrier mobility, and excellent open-air stability are especially desirable for material applications. Herein, we show theoretical evidence of a new phase of a copper(i) sulfide (Cu2S) monolayer, denoted δ-Cu2S, with both novel electronic properties and superior oxidation resistance. We find that both monolayer and bilayer δ-Cu2S have much lower formation energy than the known β-Cu2S phase. Given that β-Cu2S sheets have been recently synthesized in the laboratory (Adv. Mater.2016, 28, 8271), the higher stability of δ-Cu2S than that of β-Cu2S sheets suggests a high possibility of experimental realization of δ-Cu2S. Stability analysis indicates that δ-Cu2S is dynamically and thermally stable. Notably, δ-Cu2S exhibits superior oxidation resistance, due to the high activation energy of 1.98 eV for the chemisorption of O2 on δ-Cu2S. On its electronic properties, δ-Cu2S is a semiconductor with a modest direct band gap (1.26 eV) and an ultrahigh electron mobility of up to 6880 cm2 V-1 s-1, about 27 times that (246 cm2 V-1 s-1) of the β-Cu2S bilayer. The marked difference between the electron and hole mobilities of δ-Cu2S suggests easy separation of electrons and holes for solar energy conversion. Combination of these novel properties makes δ-Cu2S a promising 2D material for future applications in electronics and optoelectronics with high thermal and chemical stability.
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Affiliation(s)
- Yu Guo
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Dalian University of Technology), Ministry of Education, Dalian, Liaoning 116024, China.
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Pei J, Yang J, Yildirim T, Zhang H, Lu Y. Many-Body Complexes in 2D Semiconductors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1706945. [PMID: 30129218 DOI: 10.1002/adma.201706945] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 06/10/2018] [Indexed: 05/25/2023]
Abstract
2D semiconductors such as transition metal dichalcogenides (TMDs) and black phosphorus (BP) are currently attracting great attention due to their intrinsic bandgaps and strong excitonic emissions, making them potential candidates for novel optoelectronic applications. Optoelectronic devices fabricated from 2D semiconductors exhibit many-body complexes (exciton, trion, biexciton, etc.) which determine the materials optical and electrical properties. Characterization and manipulation of these complexes have become a reality due to their enhanced binding energies as a direct result from reduced dielectric screening and enhanced Coulomb interactions in the 2D regime. Furthermore, the atomic thickness and extremely large surface-to-volume ratio of 2D semiconductors allow the possibility of modulating their inherent optical, electrical, and optoelectronic properties using a variety of different environmental stimuli. To fully realize the potential functionalities of these many-body complexes in optoelectronics, a comprehensive understanding of their formation mechanism is essential. A topical and concise summary of the recent frontier research progress related to many-body complexes in 2D semiconductors is provided here. Moreover, detailed discussions covering the aspects of fundamental theory, experimental investigations, modulation of properties, and optoelectronic applications are given. Lastly, personal insights into the current challenges and future outlook of many-body complexes in 2D semiconducting materials are presented.
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Affiliation(s)
- Jiajie Pei
- Collaborative Innovation Center for Optoelectronic Science and Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, P. R. China
| | - Jiong Yang
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, 518060, P. R. China
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, P. R. China
| | - Tanju Yildirim
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, 518060, P. R. China
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, P. R. China
| | - Han Zhang
- Collaborative Innovation Center for Optoelectronic Science and Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, P. R. China
| | - Yuerui Lu
- Research School of Engineering, The Australian National University, Canberra, ACT 2601, Australia
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48
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Wang L, Wang W, Wang Q, Chi X, Kang Z, Zhou Q, Pan L, Zhang H, Wang Y. Study on photoelectric characteristics of monolayer WS2 films. RSC Adv 2019; 9:37195-37200. [PMID: 35542289 PMCID: PMC9075536 DOI: 10.1039/c9ra07924f] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 11/28/2019] [Accepted: 10/21/2019] [Indexed: 01/29/2023] Open
Abstract
It is important to determine the time-dependent evolution of the excited monolayer WS2, which will provide a basis for the reasonable design of optoelectronic devices based on two-dimensional transition metal dichalcogenides. Here, we made a simple and large-area photodetector based on the monolayer WS2, with high light sensitivity and fast response, benefiting from the special dynamics of carrier involving the exciton, trion, and charge. Moreover, we tested the relaxation behavior of the excited monolayer WS2 by employing transient absorption (TA). It was found that the multi-body interaction among exciton would occur after the density of pump photon increases to 3.45 × 1014 photons per cm2. The exciton dissociation accompanying the generation of trion would appear in the photo-induced relaxation process, which would be a benefit for the operation of this photodetector. Increasing the energy of the exciton is good for the generation of carrier by comparing the relaxation behavior of WS2 excited to A and B exciton states. However, the bound exciton relaxation, originating from the capture process of the defect state, would exist and play an unfavorable role during the functioning of devices. It is important to determine the time-dependent evolution of the excited monolayer WS2, which will provide a basis for the reasonable design of optoelectronic devices based on two-dimensional transition metal dichalcogenides.![]()
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Affiliation(s)
- Lin Wang
- Femtosecond Laser Laboratory
- Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education)
- College of Physics
- Jilin University
- Changchun 130012
| | - Wenyan Wang
- Femtosecond Laser Laboratory
- Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education)
- College of Physics
- Jilin University
- Changchun 130012
| | - Quan Wang
- Femtosecond Laser Laboratory
- Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education)
- College of Physics
- Jilin University
- Changchun 130012
| | - Xiaochun Chi
- Femtosecond Laser Laboratory
- Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education)
- College of Physics
- Jilin University
- Changchun 130012
| | - Zhihui Kang
- Femtosecond Laser Laboratory
- Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education)
- College of Physics
- Jilin University
- Changchun 130012
| | - Qiang Zhou
- State Key Laboratory of Superhard Materials
- College of Physics
- Jilin University
- Changchun 130012
- P. R. China
| | - Lingyun Pan
- Femtosecond Laser Laboratory
- Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education)
- College of Physics
- Jilin University
- Changchun 130012
| | - Hanzhuang Zhang
- Femtosecond Laser Laboratory
- Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education)
- College of Physics
- Jilin University
- Changchun 130012
| | - Yinghui Wang
- Femtosecond Laser Laboratory
- Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education)
- College of Physics
- Jilin University
- Changchun 130012
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49
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Thakar K, Mukherjee B, Grover S, Kaushik N, Deshmukh M, Lodha S. Multilayer ReS 2 Photodetectors with Gate Tunability for High Responsivity and High-Speed Applications. ACS APPLIED MATERIALS & INTERFACES 2018; 10:36512-36522. [PMID: 30251824 DOI: 10.1021/acsami.8b11248] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Rhenium disulfide (ReS2) is an attractive candidate for photodetection applications owing to its thickness-independent direct band gap. Despite various photodetection studies using two-dimensional semiconductors, the trade-off between responsivity and response time under varying measurement conditions has not been studied in detail. This report presents a comprehensive study of the architectural, laser power and gate bias dependence of responsivity and speed in supported and suspended ReS2 phototransistors. Photocurrent scans show uniform photogeneration across the entire channel because of enhanced optical absorption and a direct band gap in multilayer ReS2. A high responsivity of 4 A W-1 (at 50 ms response time) and a low response time of 20 μs (at 4 mA W-1 responsivity) make this one of the fastest reported transition-metal dichalcogenide photodetectors. Occupancy of intrinsic (bulk ReS2) and extrinsic (ReS2/SiO2 interface) traps is modulated using gate bias to demonstrate tunability of the response time (responsivity) over 4 orders (15×) of magnitude, highlighting the versatility of these photodetectors. Differences in the trap distributions of suspended and supported channel architectures, and their occupancy under different gate biases enable switching the dominant operating mechanism between either photogating or photoconduction. Further, a new metric that captures intrinsic photodetector performance by including the trade-off between its responsivity and speed, besides normalizing for the applied bias and geometry, is proposed and benchmarked for this work.
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Affiliation(s)
- Kartikey Thakar
- Department of Electrical Engineering , Indian Institute of Technology Bombay , Mumbai , 400076 , India
| | - Bablu Mukherjee
- Department of Electrical Engineering , Indian Institute of Technology Bombay , Mumbai , 400076 , India
| | - Sameer Grover
- Department of Condensed Matter Physics and Materials Science , Tata Institute of Fundamental Research , Mumbai , 400005 , India
| | - Naveen Kaushik
- Department of Electrical Engineering , Indian Institute of Technology Bombay , Mumbai , 400076 , India
| | - Mandar Deshmukh
- Department of Condensed Matter Physics and Materials Science , Tata Institute of Fundamental Research , Mumbai , 400005 , India
| | - Saurabh Lodha
- Department of Electrical Engineering , Indian Institute of Technology Bombay , Mumbai , 400076 , India
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Refaely-Abramson S, Qiu DY, Louie SG, Neaton JB. Defect-Induced Modification of Low-Lying Excitons and Valley Selectivity in Monolayer Transition Metal Dichalcogenides. PHYSICAL REVIEW LETTERS 2018; 121:167402. [PMID: 30387666 DOI: 10.1103/physrevlett.121.167402] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2018] [Indexed: 05/24/2023]
Abstract
We study the effect of point-defect chalcogen vacancies on the optical properties of monolayer transition metal dichalcogenides using ab initio GW and Bethe-Salpeter equation calculations. We find that chalcogen vacancies introduce unoccupied in-gap states and occupied resonant defect states within the quasiparticle continuum of the valence band. These defect states give rise to a number of strongly bound defect excitons and hybridize with excitons of the pristine system, reducing the valley-selective circular dichroism. Our results suggest a pathway to tune spin-valley polarization and other optical properties through defect engineering.
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Affiliation(s)
- Sivan Refaely-Abramson
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Diana Y Qiu
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Steven G Louie
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Jeffrey B Neaton
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Kavli Energy Nanosciences Institute at Berkeley, Berkeley, California 94720, USA
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