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Matthiesen M, Hortensius JR, Mañas-Valero S, Kapon I, Dumcenco D, Giannini E, Šiškins M, Ivanov BA, van der Zant HSJ, Coronado E, Kuzmenko AB, Afanasiev D, Caviglia AD. Controlling Magnetism with Light in a Zero Orbital Angular Momentum Antiferromagnet. Phys Rev Lett 2023; 130:076702. [PMID: 36867817 DOI: 10.1103/physrevlett.130.076702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 11/17/2022] [Accepted: 12/21/2022] [Indexed: 06/18/2023]
Abstract
Antiferromagnetic materials feature intrinsic ultrafast spin dynamics, making them ideal candidates for future magnonic devices operating at THz frequencies. A major focus of current research is the investigation of optical methods for the efficient generation of coherent magnons in antiferromagnetic insulators. In magnetic lattices endowed with orbital angular momentum, spin-orbit coupling enables spin dynamics through the resonant excitation of low-energy electric dipoles such as phonons and orbital resonances which interact with spins. However, in magnetic systems with zero orbital angular momentum, microscopic pathways for the resonant and low-energy optical excitation of coherent spin dynamics are lacking. Here, we consider experimentally the relative merits of electronic and vibrational excitations for the optical control of zero orbital angular momentum magnets, focusing on a limit case: the antiferromagnet manganese phosphorous trisulfide (MnPS_{3}), constituted by orbital singlet Mn^{2+} ions. We study the correlation of spins with two types of excitations within its band gap: a bound electron orbital excitation from the singlet orbital ground state of Mn^{2+} into an orbital triplet state, which causes coherent spin precession, and a vibrational excitation of the crystal field that causes thermal spin disorder. Our findings cast orbital transitions as key targets for magnetic control in insulators constituted by magnetic centers of zero orbital angular momentum.
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Affiliation(s)
- Mattias Matthiesen
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, Netherlands
- DQMP-University of Geneva, École de Physique, 24, Quai Ernest-Ansermet, CH-1211 Geneva, Switzerland
| | - Jorrit R Hortensius
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, Netherlands
| | - Samuel Mañas-Valero
- Instituto de Ciencia Molecular (ICMol), Universitat de Valencia, Catedrático José Beltrán 2, 46980 Paterna, Spain
| | - Itzik Kapon
- DQMP-University of Geneva, École de Physique, 24, Quai Ernest-Ansermet, CH-1211 Geneva, Switzerland
| | - Dumitru Dumcenco
- DQMP-University of Geneva, École de Physique, 24, Quai Ernest-Ansermet, CH-1211 Geneva, Switzerland
| | - Enrico Giannini
- DQMP-University of Geneva, École de Physique, 24, Quai Ernest-Ansermet, CH-1211 Geneva, Switzerland
| | - Makars Šiškins
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, Netherlands
| | - Boris A Ivanov
- Radboud University, Institute for Molecules and Materials, 6525 AJ Nijmegen, Netherlands
- Institute of Magnetism, National Academy of Sciences and Ministry of Education and Science, 03142 Kyiv, Ukraine
| | - Herre S J van der Zant
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, Netherlands
| | - Eugenio Coronado
- Instituto de Ciencia Molecular (ICMol), Universitat de Valencia, Catedrático José Beltrán 2, 46980 Paterna, Spain
| | - Alexey B Kuzmenko
- DQMP-University of Geneva, École de Physique, 24, Quai Ernest-Ansermet, CH-1211 Geneva, Switzerland
| | - Dmytro Afanasiev
- Radboud University, Institute for Molecules and Materials, 6525 AJ Nijmegen, Netherlands
| | - Andrea D Caviglia
- DQMP-University of Geneva, École de Physique, 24, Quai Ernest-Ansermet, CH-1211 Geneva, Switzerland
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2
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Tenasini G, Soler-Delgado D, Wang Z, Yao F, Dumcenco D, Giannini E, Watanabe K, Taniguchi T, Moulsdale C, Garcia-Ruiz A, Fal'ko VI, Gutiérrez-Lezama I, Morpurgo AF. Band Gap Opening in Bilayer Graphene-CrCl 3/CrBr 3/CrI 3 van der Waals Interfaces. Nano Lett 2022; 22:6760-6766. [PMID: 35930625 DOI: 10.1021/acs.nanolett.2c02369] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
We report experimental investigations of transport through bilayer graphene (BLG)/chromium trihalide (CrX3; X = Cl, Br, I) van der Waals interfaces. In all cases, a large charge transfer from BLG to CrX3 takes place (reaching densities in excess of 1013 cm-2), and generates an electric field perpendicular to the interface that opens a band gap in BLG. We determine the gap from the activation energy of the conductivity and find excellent agreement with the latest theory accounting for the contribution of the σ bands to the BLG dielectric susceptibility. We further show that for BLG/CrCl3 and BLG/CrBr3 the band gap can be extracted from the gate voltage dependence of the low-temperature conductivity, and use this finding to refine the gap dependence on the magnetic field. Our results allow a quantitative comparison of the electronic properties of BLG with theoretical predictions and indicate that electrons occupying the CrX3 conduction band are correlated.
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Affiliation(s)
| | | | - Zhe Wang
- MOE Key Laboratory for Non-equilibrium Synthesis and Modulation of Condensed Matter, Shaanxi Province Key Laboratory of Advanced Materials and Mesoscopic Physics, School of Physics, Xi'an Jiaotong University, Xi'an 710049, China
| | | | | | | | - Kenji Watanabe
- Research Center for Functional Materials, NIMS, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, NIMS, 1-1 Namiki, Tsukuba 305-0044, Japan
| | | | | | - Vladimir I Fal'ko
- Henry Royce Institute for Advanced Materials, Manchester M13 9PL, U.K
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3
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Soler-Delgado D, Yao F, Dumcenco D, Giannini E, Li J, Occhialini CA, Comin R, Ubrig N, Morpurgo AF. Probing Magnetism in Exfoliated VI 3 Layers with Magnetotransport. Nano Lett 2022; 22:6149-6155. [PMID: 35867517 DOI: 10.1021/acs.nanolett.2c01361] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
We perform magnetotransport experiments on VI3 multilayers to investigate the relation between ferromagnetism in bulk and in exfoliated layers. The magnetoconductance measured on field-effect transistors and tunnel barriers shows that the Curie temperature of exfoliated multilayers is TC = 57 K, larger than in bulk (TC,bulk = 50 K). Below T ≈ 40 K, we observe an unusual evolution of the tunneling magnetoconductance, analogous to the phenomenology observed in bulk. Comparing the magnetoconductance measured for fields applied in- or out-of-plane corroborates the analogy, allows us to determine that the orientation of the easy-axis in multilayers is similar to that in bulk, and suggests that the in-plane component of the magnetization points in different directions in different layers. Besides establishing that the magnetic state of bulk and multilayers are similar, our experiments illustrate the complementarity of magnetotransport and magneto-optical measurements to probe magnetism in 2D materials.
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Affiliation(s)
- David Soler-Delgado
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
- Department of Applied Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
| | - Fengrui Yao
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
- Department of Applied Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
| | - Dumitru Dumcenco
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
| | - Enrico Giannini
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
| | - Jiaruo Li
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Connor A Occhialini
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Riccardo Comin
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Nicolas Ubrig
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
- Department of Applied Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
| | - Alberto F Morpurgo
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
- Department of Applied Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
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4
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Wang Z, Gutiérrez-Lezama I, Dumcenco D, Ubrig N, Taniguchi T, Watanabe K, Giannini E, Gibertini M, Morpurgo AF. Magnetization dependent tunneling conductance of ferromagnetic barriers. Nat Commun 2021; 12:6659. [PMID: 34795253 PMCID: PMC8602639 DOI: 10.1038/s41467-021-26973-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 10/29/2021] [Indexed: 11/13/2022] Open
Abstract
Recent experiments on van der Waals antiferromagnets have shown that measuring the temperature (T) and magnetic field (H) dependence of the conductance allows their magnetic phase diagram to be mapped. Similarly, experiments on ferromagnetic CrBr3 barriers enabled the Curie temperature to be determined at H = 0, but a precise interpretation of the magnetoconductance data at H ≠ 0 is conceptually more complex, because at finite H there is no well-defined phase boundary. Here we perform systematic transport measurements on CrBr3 barriers and show that the tunneling magnetoconductance depends on H and T exclusively through the magnetization M(H, T) over the entire temperature range investigated. The phenomenon is reproduced by the spin-dependent Fowler–Nordheim model for tunneling, and is a direct manifestation of the spin splitting of the CrBr3 conduction band. Our analysis unveils a new approach to probe quantitatively different properties of atomically thin ferromagnetic insulators related to their magnetization by performing simple conductance measurements. Many standard techniques for investigating magnetic properties in the bulk are ill suited to atomically thin van der Waals materials. Here, Wang et al take a prototypical van der Waals ferromagnet, Chromium Bromide, and show how tunneling conductance can elucidate the material magnetic properties.
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Affiliation(s)
- Zhe Wang
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, Shaanxi Province Key Laboratory of Advanced Materials and Mesoscopic Physics, School of Physics, Xi'an Jiaotong University, Xi'an, 710049, China. .,Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211, Geneva, Switzerland.
| | - Ignacio Gutiérrez-Lezama
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211, Geneva, Switzerland.,Group of Applied Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211, Geneva, Switzerland
| | - Dumitru Dumcenco
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211, Geneva, Switzerland
| | - Nicolas Ubrig
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211, Geneva, Switzerland.,Group of Applied Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211, Geneva, Switzerland
| | - 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
| | - Enrico Giannini
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211, Geneva, Switzerland
| | - Marco Gibertini
- Dipartimento di Scienze Fisiche, Informatiche e Matematiche, University of Modena and Reggio Emilia, IT-41125, Modena, Italy.,Centro S3, CNR-Istituto Nanoscienze, IT-41125, Modena, Italy
| | - Alberto F Morpurgo
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211, Geneva, Switzerland. .,Group of Applied Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211, Geneva, Switzerland.
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5
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Trovatello C, Miranda HPC, Molina-Sánchez A, Borrego-Varillas R, Manzoni C, Moretti L, Ganzer L, Maiuri M, Wang J, Dumcenco D, Kis A, Wirtz L, Marini A, Soavi G, Ferrari AC, Cerullo G, Sangalli D, Conte SD. Strongly Coupled Coherent Phonons in Single-Layer MoS 2. ACS Nano 2020; 14:5700-5710. [PMID: 32233453 DOI: 10.1021/acsnano.0c00309] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
We present a transient absorption setup combining broadband detection over the visible-UV range with high temporal resolution (∼20 fs) which is ideally suited to trigger and detect vibrational coherences in different classes of materials. We generate and detect coherent phonons (CPs) in single-layer (1L)-MoS2, as a representative semiconducting 1L-transition metal dichalcogenide (TMD), where the confined dynamical interaction between excitons and phonons is unexplored. The coherent oscillatory motion of the out-of-plane A'1 phonons, triggered by the ultrashort laser pulses, dynamically modulates the excitonic resonances on a time scale of few tens of fs. We observe an enhancement by almost 2 orders of magnitude of the CP amplitude when detected in resonance with the C exciton peak, combined with a resonant enhancement of CP generation efficiency. Ab initio calculations of the change in the 1L-MoS2 band structure induced by the A'1 phonon displacement confirm a strong coupling with the C exciton. The resonant behavior of the CP amplitude follows the same spectral profile of the calculated Raman susceptibility tensor. These results explain the CP generation process in 1L-TMDs and demonstrate that CP excitation in 1L-MoS2 can be described as a Raman-like scattering process.
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Affiliation(s)
- Chiara Trovatello
- Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, I-20133 Milano, Italy
| | - Henrique P C Miranda
- Institute of Condensed Matter and Nanoscience (IMCN), Université Catholique de Louvain, B-1348 Louvain-laneuve, Belgium
| | - Alejandro Molina-Sánchez
- Institute of Materials Science (ICMUV), University of Valencia, Catedrático Beltrán 2, E-46980 Valencia, Spain
| | - Rocío Borrego-Varillas
- Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, I-20133 Milano, Italy
| | | | - Luca Moretti
- Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, I-20133 Milano, Italy
| | - Lucia Ganzer
- Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, I-20133 Milano, Italy
| | - Margherita Maiuri
- Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, I-20133 Milano, Italy
| | - Junjia Wang
- Cambridge Graphene Centre, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA, United Kingdom
| | - Dumitru Dumcenco
- Electrical Engineering Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne CH-1015, Switzerland
| | - Andras Kis
- Electrical Engineering Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne CH-1015, Switzerland
| | - Ludger Wirtz
- Université du Luxembourg, 162 A, avenue de la Faencerie, Luxembourg City L-1511, Luxembourg
| | - Andrea Marini
- Division of Ultrafast Process in Materials (FLASHit), CNR-ISM, Area della Ricerca di Roma 1, 00016 Monterotondo Scalo, Italy
| | - Giancarlo Soavi
- Cambridge Graphene Centre, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA, United Kingdom
| | - Andrea C Ferrari
- Cambridge Graphene Centre, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA, United Kingdom
| | - Giulio Cerullo
- Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, I-20133 Milano, Italy
- IFN-CNR, Piazza L. da Vinci 32, I-20133 Milano, Italy
| | - Davide Sangalli
- Division of Ultrafast Process in Materials (FLASHit), CNR-ISM, Area della Ricerca di Roma 1, 00016 Monterotondo Scalo, Italy
| | - Stefano Dal Conte
- Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, I-20133 Milano, Italy
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6
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Long G, Henck H, Gibertini M, Dumcenco D, Wang Z, Taniguchi T, Watanabe K, Giannini E, Morpurgo AF. Persistence of Magnetism in Atomically Thin MnPS 3 Crystals. Nano Lett 2020; 20:2452-2459. [PMID: 32142288 DOI: 10.1021/acs.nanolett.9b05165] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The magnetic state of atomically thin semiconducting layered antiferromagnets such as CrI3 and CrCl3 can be probed by forming tunnel barriers and measuring their resistance as a function of magnetic field (H) and temperature (T). This is possible because the spins within each individual layer are ferromagnetically aligned and the tunneling magnetoresistance depends on the relative orientation of the magnetization in adjacent layers. The situation is different for systems that are antiferromagnetic within the layers in which case it is unclear whether magnetoresistance measurements can provide information about the magnetic state. Here, we address this issue by investigating tunnel transport through atomically thin crystals of MnPS3, a van der Waals semiconductor that in the bulk exhibits easy-axis antiferromagnetic order within the layers. For thick multilayers below T ∼ 78 K, a T-dependent magnetoresistance sets in at μ0H ∼ 5 T and is found to track the boundary between the antiferromagnetic and the spin-flop phases known from bulk measurements. We show that the magnetoresistance persists as thickness is reduced with nearly unchanged characteristic temperature and magnetic field scales, albeit with a different dependence on H, indicating the persistence of magnetism in the ultimate limit of individual monolayers.
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Affiliation(s)
- Gen Long
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
- Group of Applied Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
| | - Hugo Henck
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
- Group of Applied Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
| | - Marco Gibertini
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
- National Centre for Computational Design and Discovery of Novel Materials (MARVEL), École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - Dumitru Dumcenco
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
| | - Zhe Wang
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
- Group of Applied Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
| | - 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
| | - Enrico Giannini
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
| | - Alberto F Morpurgo
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
- Group of Applied Physics, University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
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7
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Boureau V, Sklenard B, McLeod R, Ovchinnikov D, Dumcenco D, Kis A, Cooper D. Quantitative Mapping of the Charge Density in a Monolayer of MoS 2 at Atomic Resolution by Off-Axis Electron Holography. ACS Nano 2020; 14:524-530. [PMID: 31820927 DOI: 10.1021/acsnano.9b06716] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The electric potential, electric field, and charge density of a monolayer of MoS2 have been quantitatively measured at atomic-scale resolution. This has been performed by off-axis electron holography using a double aberration-corrected transmission electron microscope operated at 80 kV and a low electron beam current density. Using this low dose rate and acceleration voltage, the specimen damage is limited during imaging. In order to improve the sensitivity of the measurement, a series of holograms have been acquired. Instabilities of the microscope such as the drifts of the specimen, biprism, and optical aberrations during the acquisition have been corrected by data processing. Phase images of the MoS2 monolayer have been acquired with a sensitivity of 2π/698 rad associated with a spatial resolution of 2.4 Å. The improvement in the signal-to-noise ratio allows the charge density to be directly calculated from the phase images using Poisson's equation. Density functional theory simulations of the potential and charge density of this MoS2 monolayer were performed for comparison to the experiment. The experimental measurements and simulations are consistent with each other, and notably, the charge density in a sulfur monovacancy (VS) site is shown.
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Affiliation(s)
- Victor Boureau
- Université Grenoble Alpes, CEA, LETI , F-38054 Grenoble , France
| | - Benoit Sklenard
- Université Grenoble Alpes, CEA, LETI , F-38054 Grenoble , France
| | - Robert McLeod
- Université Grenoble Alpes, CEA, INAC , F-38054 Grenoble , France
| | - Dmitry Ovchinnikov
- Electrical Engineering Institute , Ecole Polytechnique Federale de Lausanne , CH-1015 Lausanne , Switzerland
| | - Dumitru Dumcenco
- Electrical Engineering Institute , Ecole Polytechnique Federale de Lausanne , CH-1015 Lausanne , Switzerland
| | - Andras Kis
- Electrical Engineering Institute , Ecole Polytechnique Federale de Lausanne , CH-1015 Lausanne , Switzerland
| | - David Cooper
- Université Grenoble Alpes, CEA, LETI , F-38054 Grenoble , France
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8
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Negri M, Francaviglia L, Dumcenco D, Bosi M, Kaplan D, Swaminathan V, Salviati G, Kis A, Fabbri F, Fontcuberta I Morral A. Quantitative Nanoscale Absorption Mapping: A Novel Technique To Probe Optical Absorption of Two-Dimensional Materials. Nano Lett 2020; 20:567-576. [PMID: 31874041 DOI: 10.1021/acs.nanolett.9b04304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Two-dimensional semiconductors, in particular transition metal dichalcogenides and related heterostructures, have gained increasing interest as they constitute potential new building blocks for the next generation of electronic and optoelectronic applications. In this work, we develop a novel nondestructive and noncontact technique for mapping the absorption properties of 2D materials, by taking advantage of the underlying substrate cathodoluminescence emission. We map the quantitative absorption of MoS2 and MoSe2 monolayers, obtained on sapphire and oxidized silicon, with nanoscale resolution. We extend our technique to the characterization of the absorption properties of MoS2/MoSe2 van der Waals heterostructures. We demonstrate that interlayer excitonic phenomena enhance the absorption in the UV range. Our technique also highlights the presence of defects such as grain boundaries and ad-layers. We provide measurements on the absorption of grain boundaries in monolayer MoS2 at different merging angles. We observe a higher absorption yield of randomly oriented monolayers with respect to 60° rotated monolayers. This work opens up a new possibility for characterizing the functional properties two-dimensional semiconductors at the nanoscale.
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Affiliation(s)
- Marco Negri
- Institute of Materials, Faculty of Engineering , École Polytechnique Fédérale de Lausanne , 1015 Lausanne , Switzerland
| | - Luca Francaviglia
- Institute of Materials, Faculty of Engineering , École Polytechnique Fédérale de Lausanne , 1015 Lausanne , Switzerland
| | - Dumitru Dumcenco
- Institute of Materials, Faculty of Engineering , École Polytechnique Fédérale de Lausanne , 1015 Lausanne , Switzerland
- Electrical Engineering Institute , École Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne , Switzerland
| | - Matteo Bosi
- Institute for Materials for Electronics and Magnetism (IMEM-CNR) , Parco Area delle Scienze 37/A , 43124 Parma , Italy
| | - Daniel Kaplan
- Fuze Precision Armaments and Technology Directorate , U.S. Army RDECOM-ARDEC , Picatinny Arsenal , New Jersey 07806 , United States
| | - Venkataraman Swaminathan
- Fuze Precision Armaments and Technology Directorate , U.S. Army RDECOM-ARDEC , Picatinny Arsenal , New Jersey 07806 , United States
| | - Giancarlo Salviati
- Institute for Materials for Electronics and Magnetism (IMEM-CNR) , Parco Area delle Scienze 37/A , 43124 Parma , Italy
| | - Andras Kis
- Electrical Engineering Institute , École Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne , Switzerland
| | - Filippo Fabbri
- NEST , Istituto Nanoscienze-CNR, Scuola Normale Superiore , Piazza San Silvestro 12 , 56127 Pisa , Italy
| | - Anna Fontcuberta I Morral
- Institute of Materials, Faculty of Engineering , École Polytechnique Fédérale de Lausanne , 1015 Lausanne , Switzerland
- Institute of Physics, Faculty of Basic Sciences , École Polytechnique Fédérale de Lausanne , 1015 Lausanne , Switzerland
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9
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Wang Z, Gibertini M, Dumcenco D, Taniguchi T, Watanabe K, Giannini E, Morpurgo AF. Determining the phase diagram of atomically thin layered antiferromagnet CrCl 3. Nat Nanotechnol 2019; 14:1116-1122. [PMID: 31712666 DOI: 10.1038/s41565-019-0565-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 09/30/2019] [Indexed: 06/10/2023]
Abstract
Changes in the spin configuration of atomically thin, magnetic van der Waals multilayers can cause drastic modifications in their opto-electronic properties. Conversely, the opto-electronic response of these systems provides information about the magnetic state, which is very difficult to obtain otherwise. Here, we show that in CrCl3 multilayers, the dependence of the tunnelling conductance on applied magnetic field, temperature and number of layers tracks the evolution of the magnetic state, enabling the magnetic phase diagram to be determined experimentally. Besides a high-field spin-flip transition occurring for all thicknesses, the in-plane magnetoconductance exhibits an even-odd effect due to a low-field spin-flop transition. Through a quantitative analysis of the phenomena, we determine the interlayer exchange coupling as well as the layer magnetization and show that in CrCl3 shape anisotropy dominates. Our results reveal the rich behaviour of atomically thin layered antiferromagnets with weak magnetic anisotropy.
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Affiliation(s)
- Zhe Wang
- Department of Quantum Matter Physics, University of Geneva, Geneva, Switzerland.
- Group of Applied Physics, University of Geneva, Geneva, Switzerland.
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Science, Xi'an Jiaotong University, Xi'an, China.
| | - Marco Gibertini
- Department of Quantum Matter Physics, University of Geneva, Geneva, Switzerland.
- National Centre for Computational Design and Discovery of Novel Materials, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
| | - Dumitru Dumcenco
- Department of Quantum Matter Physics, University of Geneva, Geneva, Switzerland
| | | | - Kenji Watanabe
- National Institute for Materials Science, Tsukuba, Japan
| | - Enrico Giannini
- Department of Quantum Matter Physics, University of Geneva, Geneva, Switzerland
| | - Alberto F Morpurgo
- Department of Quantum Matter Physics, University of Geneva, Geneva, Switzerland.
- Group of Applied Physics, University of Geneva, Geneva, Switzerland.
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10
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Manzeli S, Dumcenco D, Migliato Marega G, Kis A. Self-sensing, tunable monolayer MoS 2 nanoelectromechanical resonators. Nat Commun 2019; 10:4831. [PMID: 31645562 PMCID: PMC6811529 DOI: 10.1038/s41467-019-12795-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 09/30/2019] [Indexed: 11/09/2022] Open
Abstract
Excellent mechanical properties and the presence of piezoresistivity make single layers of transition metal dichalcogenides (TMDCs) viable candidates for integration in nanoelectromechanical systems (NEMS). We report on the realization of electromechanical resonators based on single-layer MoS2 with both piezoresistive and capacitive transduction schemes. Operating in the ultimate limit of membrane thickness, the resonant frequency of MoS2 resonators is primarily defined by the built-in mechanical tension and is in the very high frequency range. Using electrostatic interaction with a gate electrode, we tune the resonant frequency, allowing for the extraction of resonator parameters such as mass density and built-in strain. Furthermore, we study the origins of nonlinear dynamic response at high driving force. The results shed light on the potential of TMDC-based NEMS for the investigation of nanoscale mechanical effects at the limits of vertical downscaling and applications such as resonators for RF-communications, force and mass sensors.
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Affiliation(s)
- Sajedeh Manzeli
- Electrical Engineering Institute, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland.,Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland
| | - Dumitru Dumcenco
- Electrical Engineering Institute, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland.,Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland.,Department of Quantum Matter Physics, Université de Genève, 1211, Geneva, Switzerland
| | - Guilherme Migliato Marega
- Electrical Engineering Institute, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland.,Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland
| | - Andras Kis
- Electrical Engineering Institute, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland. .,Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland.
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11
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Surrente A, Kłopotowski Ł, Zhang N, Baranowski M, Mitioglu AA, Ballottin MV, Christianen PCM, Dumcenco D, Kung YC, Maude DK, Kis A, Plochocka P. Intervalley Scattering of Interlayer Excitons in a MoS 2/MoSe 2/MoS 2 Heterostructure in High Magnetic Field. Nano Lett 2018; 18:3994-4000. [PMID: 29791166 DOI: 10.1021/acs.nanolett.8b01484] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Degenerate extrema in the energy dispersion of charge carriers in solids, also referred to as valleys, can be regarded as a binary quantum degree of freedom, which can potentially be used to implement valleytronic concepts in van der Waals heterostructures based on transition metal dichalcogenides. Using magneto-photoluminescence spectroscopy, we achieve a deeper insight into the valley polarization and depolarization mechanisms of interlayer excitons formed across a MoS2/MoSe2/MoS2 heterostructure. We account for the nontrivial behavior of the valley polarization as a function of the magnetic field by considering the interplay between exchange interaction and phonon-mediated intervalley scattering in a system consisting of Zeeman-split energy levels. Our results represent a crucial step toward the understanding of the properties of interlayer excitons with strong implications for the implementation of atomically thin valleytronic devices.
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Affiliation(s)
- Alessandro Surrente
- Laboratoire National des Champs Magnétiques Intenses , UPR 3228, CNRS-UGA-UPS-INSA, 38042/31400 Grenoble/Toulouse , France
| | - Łukasz Kłopotowski
- Institute of Physics , Polish Academy of Sciences , Al. Lotników 32/46 , 02-668 Warsaw , Poland
| | - Nan Zhang
- Laboratoire National des Champs Magnétiques Intenses , UPR 3228, CNRS-UGA-UPS-INSA, 38042/31400 Grenoble/Toulouse , France
| | - Michal Baranowski
- Laboratoire National des Champs Magnétiques Intenses , UPR 3228, CNRS-UGA-UPS-INSA, 38042/31400 Grenoble/Toulouse , France
- Department of Experimental Physics, Faculty of Fundamental Problems of Technology , Wroclaw University of Science and Technology , 50-370 Wroclaw , Poland
| | - Anatolie A Mitioglu
- High Field Magnet Laboratory (HFML - EMFL) , Radboud University , 6525 ED Nijmegen , The Netherlands
| | - Mariana V Ballottin
- High Field Magnet Laboratory (HFML - EMFL) , Radboud University , 6525 ED Nijmegen , The Netherlands
| | - Peter C M Christianen
- High Field Magnet Laboratory (HFML - EMFL) , Radboud University , 6525 ED Nijmegen , The Netherlands
| | - Dumitru Dumcenco
- Electrical Engineering Institute and Institute of Materials Science and Engineering , École Polytechnique Fédérale de Lausanne , CH-1015 Lausanne , Switzerland
- Department of Quantum Matter Physics , Université de Genève , 24 quai Ernest Ansermet , CH-1211 Geneva , Switzerland
| | - Yen-Cheng Kung
- Electrical Engineering Institute and Institute of Materials Science and Engineering , École Polytechnique Fédérale de Lausanne , CH-1015 Lausanne , Switzerland
| | - Duncan K Maude
- Laboratoire National des Champs Magnétiques Intenses , UPR 3228, CNRS-UGA-UPS-INSA, 38042/31400 Grenoble/Toulouse , France
| | - Andras Kis
- Electrical Engineering Institute and Institute of Materials Science and Engineering , École Polytechnique Fédérale de Lausanne , CH-1015 Lausanne , Switzerland
| | - Paulina Plochocka
- Laboratoire National des Champs Magnétiques Intenses , UPR 3228, CNRS-UGA-UPS-INSA, 38042/31400 Grenoble/Toulouse , France
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12
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Baranowski M, Surrente A, Klopotowski L, Urban JM, Zhang N, Maude DK, Wiwatowski K, Mackowski S, Kung YC, Dumcenco D, Kis A, Plochocka P. Probing the Interlayer Exciton Physics in a MoS 2/MoSe 2/MoS 2 van der Waals Heterostructure. Nano Lett 2017; 17:6360-6365. [PMID: 28895745 DOI: 10.1021/acs.nanolett.7b03184] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Stacking atomic monolayers of semiconducting transition metal dichalcogenides (TMDs) has emerged as an effective way to engineer their properties. In principle, the staggered band alignment of TMD heterostructures should result in the formation of interlayer excitons with long lifetimes and robust valley polarization. However, these features have been observed simultaneously only in MoSe2/WSe2 heterostructures. Here we report on the observation of long-lived interlayer exciton emission in a MoS2/MoSe2/MoS2 trilayer van der Waals heterostructure. The interlayer nature of the observed transition is confirmed by photoluminescence spectroscopy, as well as by analyzing the temporal, excitation power, and temperature dependence of the interlayer emission peak. The observed complex photoluminescence dynamics suggests the presence of quasi-degenerate momentum-direct and momentum-indirect bandgaps. We show that circularly polarized optical pumping results in long-lived valley polarization of interlayer exciton. Intriguingly, the interlayer exciton photoluminescence has helicity opposite to the excitation. Our results show that through a careful choice of the TMDs forming the van der Waals heterostructure it is possible to control the circular polarization of the interlayer exciton emission.
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Affiliation(s)
- M Baranowski
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA , 143 avenue de Rangueil, 31400 Toulouse, France
- Department of Experimental Physics, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology , Wybrzeze Wyspianskiego 27, 50-370 Wrocaw, Poland
| | - A Surrente
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA , 143 avenue de Rangueil, 31400 Toulouse, France
| | - L Klopotowski
- Institute of Physics, Polish Academy of Sciences , al. Lotnikow 32/46, 02-668 Warsaw, Poland
| | - J M Urban
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA , 143 avenue de Rangueil, 31400 Toulouse, France
| | - N Zhang
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA , 143 avenue de Rangueil, 31400 Toulouse, France
| | - D K Maude
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA , 143 avenue de Rangueil, 31400 Toulouse, France
| | - K Wiwatowski
- Faculty of Physics, Astronomy, and Informatics, Nicolaus Copernicus University , Grudziadzka 5, 87-100 Torun, Poland
| | - S Mackowski
- Faculty of Physics, Astronomy, and Informatics, Nicolaus Copernicus University , Grudziadzka 5, 87-100 Torun, Poland
| | - Y C Kung
- Electrical Engineering Institute and Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland
| | - D Dumcenco
- Electrical Engineering Institute and Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland
| | - A Kis
- Electrical Engineering Institute and Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland
| | - P Plochocka
- Laboratoire National des Champs Magnétiques Intenses, CNRS-UGA-UPS-INSA , 143 avenue de Rangueil, 31400 Toulouse, France
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13
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Surrente A, Dumcenco D, Yang Z, Kuc A, Jing Y, Heine T, Kung YC, Maude DK, Kis A, Plochocka P. Defect Healing and Charge Transfer-Mediated Valley Polarization in MoS 2/MoSe 2/MoS 2 Trilayer van der Waals Heterostructures. Nano Lett 2017; 17:4130-4136. [PMID: 28603999 DOI: 10.1021/acs.nanolett.7b00904] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Monolayer transition metal dichalcogenides (TMDCs) grown by chemical vapor deposition (CVD) are plagued by a significantly lower optical quality compared to exfoliated TMDCs. In this work, we show that the optical quality of CVD-grown MoSe2 is completely recovered if the material is sandwiched in MoS2/MoSe2/MoS2 trilayer van der Waals heterostructures. We show by means of density functional theory that this remarkable and unexpected result is due to defect healing: S atoms of the more reactive MoS2 layers are donated to heal Se vacancy defects in the middle MoSe2 layer. In addition, the trilayer structure exhibits a considerable charge-transfer mediated valley polarization of MoSe2 without the need for resonant excitation. Our fabrication approach, relying solely on simple flake transfer technique, paves the way for the scalable production of large-area TMDC materials with excellent optical quality.
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Affiliation(s)
- Alessandro Surrente
- Laboratoire National des Champs Magnétiques Intenses, UPR 3228, CNRS-UGA-UPS-INSA , Grenoble and Toulouse, France
| | - Dumitru Dumcenco
- Electrical Engineering Institute and Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland
| | - Zhuo Yang
- Laboratoire National des Champs Magnétiques Intenses, UPR 3228, CNRS-UGA-UPS-INSA , Grenoble and Toulouse, France
| | - Agnieszka Kuc
- Wilhelm Ostwald Institute of Physical and Theoretical Chemistry Leipzig, University of Leipzig , 04109 Saxony Germany
- School of Engineering and Science, Jacobs University Bremen , Campus Ring 1, 28759 Bremen, Germany
| | - Yu Jing
- Wilhelm Ostwald Institute of Physical and Theoretical Chemistry Leipzig, University of Leipzig , 04109 Saxony Germany
| | - Thomas Heine
- Wilhelm Ostwald Institute of Physical and Theoretical Chemistry Leipzig, University of Leipzig , 04109 Saxony Germany
- School of Engineering and Science, Jacobs University Bremen , Campus Ring 1, 28759 Bremen, Germany
| | - Yen-Cheng Kung
- Electrical Engineering Institute and Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland
| | - Duncan K Maude
- Laboratoire National des Champs Magnétiques Intenses, UPR 3228, CNRS-UGA-UPS-INSA , Grenoble and Toulouse, France
| | - Andras Kis
- Electrical Engineering Institute and Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland
| | - Paulina Plochocka
- Laboratoire National des Champs Magnétiques Intenses, UPR 3228, CNRS-UGA-UPS-INSA , Grenoble and Toulouse, France
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14
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Liu K, Lihter M, Sarathy A, Caneva S, Qiu H, Deiana D, Tileli V, Alexander DTL, Hofmann S, Dumcenco D, Kis A, Leburton JP, Radenovic A. Geometrical Effect in 2D Nanopores. Nano Lett 2017; 17:4223-4230. [PMID: 28592108 DOI: 10.1021/acs.nanolett.7b01091] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A long-standing problem in the application of solid-state nanopores is the lack of the precise control over the geometry of artificially formed pores compared to the well-defined geometry in their biological counterpart, that is, protein nanopores. To date, experimentally investigated solid-state nanopores have been shown to adopt an approximately circular shape. In this Letter, we investigate the geometrical effect of the nanopore shape on ionic blockage induced by DNA translocation using triangular h-BN nanopores and approximately circular molybdenum disulfide (MoS2) nanopores. We observe a striking geometry-dependent ion scattering effect, which is further corroborated by a modified ionic blockage model. The well-acknowledged ionic blockage model is derived from uniform ion permeability through the 2D nanopore plane and hemisphere like access region in the nanopore vicinity. On the basis of our experimental results, we propose a modified ionic blockage model, which is highly related to the ionic profile caused by geometrical variations. Our findings shed light on the rational design of 2D nanopores and should be applicable to arbitrary nanopore shapes.
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Affiliation(s)
| | | | | | - Sabina Caneva
- Department of Engineering, University of Cambridge , JJ Thomson Avenue, CB3 0FA Cambridge, United Kingdom
| | | | | | | | | | - Stephan Hofmann
- Department of Engineering, University of Cambridge , JJ Thomson Avenue, CB3 0FA Cambridge, United Kingdom
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15
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De Fazio D, Goykhman I, Yoon D, Bruna M, Eiden A, Milana S, Sassi U, Barbone M, Dumcenco D, Marinov K, Kis A, Ferrari AC. High Responsivity, Large-Area Graphene/MoS2 Flexible Photodetectors. ACS Nano 2016; 10:8252-62. [PMID: 27537529 PMCID: PMC5323022 DOI: 10.1021/acsnano.6b05109] [Citation(s) in RCA: 111] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2016] [Accepted: 08/18/2016] [Indexed: 05/23/2023]
Abstract
We present flexible photodetectors (PDs) for visible wavelengths fabricated by stacking centimeter-scale chemical vapor deposited (CVD) single layer graphene (SLG) and single layer CVD MoS2, both wet transferred onto a flexible polyethylene terephthalate substrate. The operation mechanism relies on injection of photoexcited electrons from MoS2 to the SLG channel. The external responsivity is 45.5A/W and the internal 570A/W at 642 nm. This is at least 2 orders of magnitude higher than bulk-semiconductor flexible membranes. The photoconductive gain is up to 4 × 10(5). The photocurrent is in the 0.1-100 μA range. The devices are semitransparent, with 8% absorptance at 642 nm, and are stable upon bending to a curvature of 1.4 cm. These capabilities and the low-voltage operation (<1 V) make them attractive for wearable applications.
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Affiliation(s)
- Domenico De Fazio
- Cambridge
Graphene Centre, University of Cambridge, Cambridge CB3 0FA, United Kingdom
| | - Ilya Goykhman
- Cambridge
Graphene Centre, University of Cambridge, Cambridge CB3 0FA, United Kingdom
| | - Duhee Yoon
- Cambridge
Graphene Centre, University of Cambridge, Cambridge CB3 0FA, United Kingdom
| | - Matteo Bruna
- Cambridge
Graphene Centre, University of Cambridge, Cambridge CB3 0FA, United Kingdom
| | - Anna Eiden
- Cambridge
Graphene Centre, University of Cambridge, Cambridge CB3 0FA, United Kingdom
| | - Silvia Milana
- Cambridge
Graphene Centre, University of Cambridge, Cambridge CB3 0FA, United Kingdom
| | - Ugo Sassi
- Cambridge
Graphene Centre, University of Cambridge, Cambridge CB3 0FA, United Kingdom
| | - Matteo Barbone
- Cambridge
Graphene Centre, University of Cambridge, Cambridge CB3 0FA, United Kingdom
| | - Dumitru Dumcenco
- Electrical
Engineering Institute, Ecole Polytechnique
Federale de Lausanne, Lausanne CH-1015, Switzerland
| | - Kolyo Marinov
- Electrical
Engineering Institute, Ecole Polytechnique
Federale de Lausanne, Lausanne CH-1015, Switzerland
| | - Andras Kis
- Electrical
Engineering Institute, Ecole Polytechnique
Federale de Lausanne, Lausanne CH-1015, Switzerland
| | - Andrea C. Ferrari
- Cambridge
Graphene Centre, University of Cambridge, Cambridge CB3 0FA, United Kingdom
- E-mail:
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16
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Yuan H, Liu Z, Xu G, Zhou B, Wu S, Dumcenco D, Yan K, Zhang Y, Mo SK, Dudin P, Kandyba V, Yablonskikh M, Barinov A, Shen Z, Zhang S, Huang Y, Xu X, Hussain Z, Hwang HY, Cui Y, Chen Y. Evolution of the Valley Position in Bulk Transition-Metal Chalcogenides and Their Monolayer Limit. Nano Lett 2016; 16:4738-4745. [PMID: 27357620 DOI: 10.1021/acs.nanolett.5b05107] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Layered transition metal chalcogenides with large spin orbit coupling have recently sparked much interest due to their potential applications for electronic, optoelectronic, spintronics, and valleytronics. However, most current understanding of the electronic structure near band valleys in momentum space is based on either theoretical investigations or optical measurements, leaving the detailed band structure elusive. For example, the exact position of the conduction band valley of bulk MoS2 remains controversial. Here, using angle-resolved photoemission spectroscopy with submicron spatial resolution (micro-ARPES), we systematically imaged the conduction/valence band structure evolution across representative chalcogenides MoS2, WS2, and WSe2, as well as the thickness dependent electronic structure from bulk to the monolayer limit. These results establish a solid basis to understand the underlying valley physics of these materials, and also provide a link between chalcogenide electronic band structure and their physical properties for potential valleytronics applications.
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Affiliation(s)
- Hongtao Yuan
- Geballe Laboratory for Advanced Materials, Stanford University , Stanford, California 94305, United States
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States
| | - Zhongkai Liu
- Geballe Laboratory for Advanced Materials, Stanford University , Stanford, California 94305, United States
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States
- School of Physical Science and Technology, ShanghaiTech University , Shanghai 200031, China
- CAS-Shanghai Science Research Center , 239 Zhang Heng Road, Shanghai 201203, China
| | - Gang Xu
- Geballe Laboratory for Advanced Materials, Stanford University , Stanford, California 94305, United States
| | - Bo Zhou
- Physics Department, Clarendon Laboratory, University of Oxford , Parks Road, Oxford OX1 3PU, United Kingdom
- Advanced Light Source, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Sanfeng Wu
- Department of Physics, Department of Materials Science and Engineering, University of Washington , Seattle, Washington 98195, United States
| | - Dumitru Dumcenco
- Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology , Taipei 106, Taiwan (ROC)
- Electrical Engineering Institute, Ecole Polytechnique Federale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland
| | - Kai Yan
- Geballe Laboratory for Advanced Materials, Stanford University , Stanford, California 94305, United States
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States
| | - Yi Zhang
- Advanced Light Source, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Sung-Kwan Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Pavel Dudin
- Diamond Light Source , Didcot, Oxfordshire OX11 0BW, United Kingdom
| | - Victor Kandyba
- Elettra-Sincrotrone Trieste ScPA , Trieste, Basovizza 34149, Italy
| | | | - Alexei Barinov
- Elettra-Sincrotrone Trieste ScPA , Trieste, Basovizza 34149, Italy
| | - Zhixun Shen
- Geballe Laboratory for Advanced Materials, Stanford University , Stanford, California 94305, United States
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States
| | - Shoucheng Zhang
- Geballe Laboratory for Advanced Materials, Stanford University , Stanford, California 94305, United States
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States
| | - Yingsheng Huang
- Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology , Taipei 106, Taiwan (ROC)
| | - Xiaodong Xu
- Department of Physics, Department of Materials Science and Engineering, University of Washington , Seattle, Washington 98195, United States
| | - Zahid Hussain
- Advanced Light Source, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States
| | - Harold Y Hwang
- Geballe Laboratory for Advanced Materials, Stanford University , Stanford, California 94305, United States
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States
| | - Yi Cui
- Geballe Laboratory for Advanced Materials, Stanford University , Stanford, California 94305, United States
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States
- Department of Materials Science and Engineering, Stanford University , Stanford, California 94305, United States
| | - Yulin Chen
- School of Physical Science and Technology, ShanghaiTech University , Shanghai 200031, China
- CAS-Shanghai Science Research Center , 239 Zhang Heng Road, Shanghai 201203, China
- Physics Department, Clarendon Laboratory, University of Oxford , Parks Road, Oxford OX1 3PU, United Kingdom
- Diamond Light Source , Didcot, Oxfordshire OX11 0BW, United Kingdom
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17
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Ovchinnikov D, Gargiulo F, Allain A, Pasquier DJ, Dumcenco D, Ho CH, Yazyev OV, Kis A. Disorder engineering and conductivity dome in ReS2 with electrolyte gating. Nat Commun 2016; 7:12391. [PMID: 27499375 PMCID: PMC4979068 DOI: 10.1038/ncomms12391] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 06/29/2016] [Indexed: 11/09/2022] Open
Abstract
Atomically thin rhenium disulphide (ReS2) is a member of the transition metal dichalcogenide family of materials. This two-dimensional semiconductor is characterized by weak interlayer coupling and a distorted 1T structure, which leads to anisotropy in electrical and optical properties. Here we report on the electrical transport study of mono- and multilayer ReS2 with polymer electrolyte gating. We find that the conductivity of monolayer ReS2 is completely suppressed at high carrier densities, an unusual feature unique to monolayers, making ReS2 the first example of such a material. Using dual-gated devices, we can distinguish the gate-induced doping from the electrostatic disorder induced by the polymer electrolyte itself. Theoretical calculations and a transport model indicate that the observed conductivity suppression can be explained by a combination of a narrow conduction band and Anderson localization due to electrolyte-induced disorder.
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Affiliation(s)
- Dmitry Ovchinnikov
- Electrical Engineering Institute, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.,Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Fernando Gargiulo
- Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Adrien Allain
- Electrical Engineering Institute, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.,Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Diego José Pasquier
- Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Dumitru Dumcenco
- Electrical Engineering Institute, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.,Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Ching-Hwa Ho
- Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 106, Taiwan
| | - Oleg V Yazyev
- Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Andras Kis
- Electrical Engineering Institute, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.,Institute of Materials Science and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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18
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Feng J, Liu K, Graf M, Dumcenco D, Kis A, Di Ventra M, Radenovic A. Observation of ionic Coulomb blockade in nanopores. Nat Mater 2016; 15:850-5. [PMID: 27019385 DOI: 10.1038/nmat4607] [Citation(s) in RCA: 120] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Accepted: 02/24/2016] [Indexed: 05/12/2023]
Abstract
Emergent behaviour from electron-transport properties is routinely observed in systems with dimensions approaching the nanoscale. However, analogous mesoscopic behaviour resulting from ionic transport has so far not been observed, most probably because of bottlenecks in the controlled fabrication of subnanometre nanopores for use in nanofluidics. Here, we report measurements of ionic transport through a single subnanometre pore junction, and the observation of ionic Coulomb blockade: the ionic counterpart of the electronic Coulomb blockade observed for quantum dots. Our findings demonstrate that nanoscopic, atomically thin pores allow for the exploration of phenomena in ionic transport, and suggest that nanopores may also further our understanding of transport through biological ion channels.
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Affiliation(s)
- Jiandong Feng
- Laboratory of Nanoscale Biology, Institute of Bioengineering, School of Engineering, EPFL, 1015 Lausanne, Switzerland
| | - Ke Liu
- Laboratory of Nanoscale Biology, Institute of Bioengineering, School of Engineering, EPFL, 1015 Lausanne, Switzerland
| | - Michael Graf
- Laboratory of Nanoscale Biology, Institute of Bioengineering, School of Engineering, EPFL, 1015 Lausanne, Switzerland
| | - Dumitru Dumcenco
- Laboratory of Nanoscale Electronics and Structures, Institute of Electrical Engineering, School of Engineering, EPFL, 1015 Lausanne, Switzerland
| | - Andras Kis
- Laboratory of Nanoscale Electronics and Structures, Institute of Electrical Engineering, School of Engineering, EPFL, 1015 Lausanne, Switzerland
| | - Massimiliano Di Ventra
- Department of Physics, University of California, San Diego, La Jolla, California 92093, USA
| | - Aleksandra Radenovic
- Laboratory of Nanoscale Biology, Institute of Bioengineering, School of Engineering, EPFL, 1015 Lausanne, Switzerland
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Feng J, Graf M, Liu K, Ovchinnikov D, Dumcenco D, Heiranian M, Nandigana V, Aluru NR, Kis A, Radenovic A. Single-layer MoS2 nanopores as nanopower generators. Nature 2016; 536:197-200. [DOI: 10.1038/nature18593] [Citation(s) in RCA: 613] [Impact Index Per Article: 76.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2015] [Accepted: 05/13/2016] [Indexed: 12/23/2022]
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Feng J, Liu K, Bulushev RD, Khlybov S, Dumcenco D, Kis A, Radenovic A. Identification of single nucleotides in MoS2 nanopores. Nat Nanotechnol 2015; 10:1070-6. [PMID: 26389660 DOI: 10.1038/nnano.2015.219] [Citation(s) in RCA: 288] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Accepted: 08/20/2015] [Indexed: 05/19/2023]
Abstract
The size of the sensing region in solid-state nanopores is determined by the size of the pore and the thickness of the pore membrane, so ultrathin membranes such as graphene and single-layer molybdenum disulphide could potentially offer the necessary spatial resolution for nanopore DNA sequencing. However, the fast translocation speeds (3,000-50,000 nt ms(-1)) of DNA molecules moving across such membranes limit their usability. Here, we show that a viscosity gradient system based on room-temperature ionic liquids can be used to control the dynamics of DNA translocation through MoS2 nanopores. The approach can be used to statistically detect all four types of nucleotide, which are identified according to current signatures recorded during their transient residence in the narrow orifice of the atomically thin MoS2 nanopore. Our technique, which exploits the high viscosity of room-temperature ionic liquids, provides optimal single nucleotide translocation speeds for DNA sequencing, while maintaining a signal-to-noise ratio higher than 10.
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Affiliation(s)
- Jiandong Feng
- Laboratory of Nanoscale Biology, Institute of Bioengineering, School of Engineering, EPFL, Lausanne 1015, Switzerland
| | - Ke Liu
- Laboratory of Nanoscale Biology, Institute of Bioengineering, School of Engineering, EPFL, Lausanne 1015, Switzerland
| | - Roman D Bulushev
- Laboratory of Nanoscale Biology, Institute of Bioengineering, School of Engineering, EPFL, Lausanne 1015, Switzerland
| | - Sergey Khlybov
- Laboratory of Nanoscale Biology, Institute of Bioengineering, School of Engineering, EPFL, Lausanne 1015, Switzerland
| | - Dumitru Dumcenco
- Laboratory of Nanoscale Electronics and Structure, Institute of Electrical Engineering, School of Engineering, EPFL, Lausanne 1015, Switzerland
| | - Andras Kis
- Laboratory of Nanoscale Electronics and Structure, Institute of Electrical Engineering, School of Engineering, EPFL, Lausanne 1015, Switzerland
| | - Aleksandra Radenovic
- Laboratory of Nanoscale Biology, Institute of Bioengineering, School of Engineering, EPFL, Lausanne 1015, Switzerland
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Feng J, Liu K, Graf M, Lihter M, Bulushev RD, Dumcenco D, Alexander DTL, Krasnozhon D, Vuletic T, Kis A, Radenovic A. Electrochemical Reaction in Single Layer MoS2: Nanopores Opened Atom by Atom. Nano Lett 2015; 15:3431-8. [PMID: 25928894 DOI: 10.1021/acs.nanolett.5b00768] [Citation(s) in RCA: 132] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Ultrathin nanopore membranes based on 2D materials have demonstrated ultimate resolution toward DNA sequencing. Among them, molybdenum disulfide (MoS2) shows long-term stability as well as superior sensitivity enabling high throughput performance. The traditional method of fabricating nanopores with nanometer precision is based on the use of focused electron beams in transmission electron microscope (TEM). This nanopore fabrication process is time-consuming, expensive, not scalable, and hard to control below 1 nm. Here, we exploited the electrochemical activity of MoS2 and developed a convenient and scalable method to controllably make nanopores in single-layer MoS2 with subnanometer precision using electrochemical reaction (ECR). The electrochemical reaction on the surface of single-layer MoS2 is initiated at the location of defects or single atom vacancy, followed by the successive removals of individual atoms or unit cells from single-layer MoS2 lattice and finally formation of a nanopore. Step-like features in the ionic current through the growing nanopore provide direct feedback on the nanopore size inferred from a widely used conductance vs pore size model. Furthermore, DNA translocations can be detected in situ when as-fabricated MoS2 nanopores are used. The atomic resolution and accessibility of this approach paves the way for mass production of nanopores in 2D membranes for potential solid-state nanopore sequencing.
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Affiliation(s)
- J Feng
- †Laboratory of Nanoscale Biology, Institute of Bioengineering, School of Engineering, EPFL, 1015 Lausanne, Switzerland
| | - K Liu
- †Laboratory of Nanoscale Biology, Institute of Bioengineering, School of Engineering, EPFL, 1015 Lausanne, Switzerland
| | - M Graf
- †Laboratory of Nanoscale Biology, Institute of Bioengineering, School of Engineering, EPFL, 1015 Lausanne, Switzerland
| | - M Lihter
- †Laboratory of Nanoscale Biology, Institute of Bioengineering, School of Engineering, EPFL, 1015 Lausanne, Switzerland
- ‡Institut za fiziku, Bijenička 46, Zagreb, Croatia
| | - R D Bulushev
- †Laboratory of Nanoscale Biology, Institute of Bioengineering, School of Engineering, EPFL, 1015 Lausanne, Switzerland
| | - D Dumcenco
- §Laboratory of Nanoscale Electronics and Structure, Institute of Electrical Engineering, School of Engineering, EPFL, 1015 Lausanne, Switzerland
| | - D T L Alexander
- ∥Centre Interdisciplinaire de Microscopie Électronique (CIME), EPFL, 1015 Lausanne, Switzerland
| | - D Krasnozhon
- §Laboratory of Nanoscale Electronics and Structure, Institute of Electrical Engineering, School of Engineering, EPFL, 1015 Lausanne, Switzerland
| | - T Vuletic
- ‡Institut za fiziku, Bijenička 46, Zagreb, Croatia
| | - A Kis
- §Laboratory of Nanoscale Electronics and Structure, Institute of Electrical Engineering, School of Engineering, EPFL, 1015 Lausanne, Switzerland
| | - A Radenovic
- †Laboratory of Nanoscale Biology, Institute of Bioengineering, School of Engineering, EPFL, 1015 Lausanne, Switzerland
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Dumcenco D, Ovchinnikov D, Marinov K, Lazić P, Gibertini M, Marzari N, Sanchez OL, Kung YC, Krasnozhon D, Chen MW, Bertolazzi S, Gillet P, Fontcuberta i Morral A, Radenovic A, Kis A. Large-Area Epitaxial Monolayer MoS2. ACS Nano 2015; 9:4611-20. [PMID: 25843548 PMCID: PMC4415455 DOI: 10.1021/acsnano.5b01281] [Citation(s) in RCA: 317] [Impact Index Per Article: 35.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Accepted: 03/30/2015] [Indexed: 05/19/2023]
Abstract
Two-dimensional semiconductors such as MoS2 are an emerging material family with wide-ranging potential applications in electronics, optoelectronics, and energy harvesting. Large-area growth methods are needed to open the way to applications. Control over lattice orientation during growth remains a challenge. This is needed to minimize or even avoid the formation of grain boundaries, detrimental to electrical, optical, and mechanical properties of MoS2 and other 2D semiconductors. Here, we report on the growth of high-quality monolayer MoS2 with control over lattice orientation. We show that the monolayer film is composed of coalescing single islands with limited numbers of lattice orientation due to an epitaxial growth mechanism. Optical absorbance spectra acquired over large areas show significant absorbance in the high-energy part of the spectrum, indicating that MoS2 could also be interesting for harvesting this region of the solar spectrum and fabrication of UV-sensitive photodetectors. Even though the interaction between the growth substrate and MoS2 is strong enough to induce lattice alignment via van der Waals interaction, we can easily transfer the grown material and fabricate devices. Local potential mapping along channels in field-effect transistors shows that the single-crystal MoS2 grains in our film are well connected, with interfaces that do not degrade the electrical conductivity. This is also confirmed by the relatively large and length-independent mobility in devices with a channel length reaching 80 μm.
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Affiliation(s)
- Dumitru Dumcenco
- Electrical Engineering Institute, Institute of Materials, Institute of Condensed Matter Physics, and Institute of Bioengineering, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Dmitry Ovchinnikov
- Electrical Engineering Institute, Institute of Materials, Institute of Condensed Matter Physics, and Institute of Bioengineering, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Kolyo Marinov
- Electrical Engineering Institute, Institute of Materials, Institute of Condensed Matter Physics, and Institute of Bioengineering, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Predrag Lazić
- Institute Ruđer Bošković (IRB), HR-10000 Zagreb, Croatia
| | - Marco Gibertini
- Electrical Engineering Institute, Institute of Materials, Institute of Condensed Matter Physics, and Institute of Bioengineering, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Nicola Marzari
- Electrical Engineering Institute, Institute of Materials, Institute of Condensed Matter Physics, and Institute of Bioengineering, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Oriol Lopez Sanchez
- Electrical Engineering Institute, Institute of Materials, Institute of Condensed Matter Physics, and Institute of Bioengineering, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Yen-Cheng Kung
- Electrical Engineering Institute, Institute of Materials, Institute of Condensed Matter Physics, and Institute of Bioengineering, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Daria Krasnozhon
- Electrical Engineering Institute, Institute of Materials, Institute of Condensed Matter Physics, and Institute of Bioengineering, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Ming-Wei Chen
- Electrical Engineering Institute, Institute of Materials, Institute of Condensed Matter Physics, and Institute of Bioengineering, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Simone Bertolazzi
- Electrical Engineering Institute, Institute of Materials, Institute of Condensed Matter Physics, and Institute of Bioengineering, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Philippe Gillet
- Electrical Engineering Institute, Institute of Materials, Institute of Condensed Matter Physics, and Institute of Bioengineering, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Anna Fontcuberta i Morral
- Electrical Engineering Institute, Institute of Materials, Institute of Condensed Matter Physics, and Institute of Bioengineering, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Aleksandra Radenovic
- Electrical Engineering Institute, Institute of Materials, Institute of Condensed Matter Physics, and Institute of Bioengineering, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Andras Kis
- Electrical Engineering Institute, Institute of Materials, Institute of Condensed Matter Physics, and Institute of Bioengineering, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
- Address correspondence to
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Abstract
We report on the fabrication of field-effect transistors based on single layers and bilayers of the semiconductor WS2 and the investigation of their electronic transport properties. We find that the doping level strongly depends on the device environment and that long in situ annealing drastically improves the contact transparency, allowing four-terminal measurements to be performed and the pristine properties of the material to be recovered. Our devices show n-type behavior with a high room-temperature on/off current ratio of ∼10(6). They show clear metallic behavior at high charge carrier densities and mobilities as high as ∼140 cm(2)/(V s) at low temperatures (above 300 cm(2)/(V s) in the case of bilayers). In the insulating regime, the devices exhibit variable-range hopping, with a localization length of about 2 nm that starts to increase as the Fermi level enters the conduction band. The promising electronic properties of WS2, comparable to those of single-layer MoS2 and WSe2, together with its strong spin-orbit coupling, make it interesting for future applications in electronic, optical, and valleytronic devices.
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Affiliation(s)
- Dmitry Ovchinnikov
- Electrical Engineering Institute, Ecole Polytechnique Federale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland
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