1
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Wang T, Hopper TR, Mondal N, Liu S, Yao C, Zheng X, Torrisi F, Bakulin AA. Hot Carrier Cooling and Trapping in Atomically Thin WS 2 Probed by Three-Pulse Femtosecond Spectroscopy. ACS NANO 2023; 17:6330-6340. [PMID: 36939760 PMCID: PMC10100566 DOI: 10.1021/acsnano.2c10479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Accepted: 03/14/2023] [Indexed: 06/18/2023]
Abstract
Transition metal dichalcogenides (TMDs) have shown outstanding semiconducting properties which make them promising materials for next-generation optoelectronic and electronic devices. These properties are imparted by fundamental carrier-carrier and carrier-phonon interactions that are foundational to hot carrier cooling. Recent transient absorption studies have reported ultrafast time scales for carrier cooling in TMDs that can be slowed at high excitation densities via a hot-phonon bottleneck (HPB) and discussed these findings in the light of optoelectronic applications. However, quantitative descriptions of the HPB in TMDs, including details of the electron-lattice coupling and how cooling is affected by the redistribution of energy between carriers, are still lacking. Here, we use femtosecond pump-push-probe spectroscopy as a single approach to systematically characterize the scattering of hot carriers with optical phonons, cold carriers, and defects in a benchmark TMD monolayer of polycrystalline WS2. By controlling the interband pump and intraband push excitations, we observe, in real-time (i) an extremely rapid "intrinsic" cooling rate of ∼18 ± 2.7 eV/ps, which can be slowed with increasing hot carrier density, (ii) the deprecation of this HPB at elevated cold carrier densities, exposing a previously undisclosed role of the carrier-carrier interactions in mediating cooling, and (iii) the interception of high energy hot carriers on the subpicosecond time scale by lattice defects, which may account for the lower photoluminescence yield of TMDs when excited above band gap.
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Affiliation(s)
- Tong Wang
- Department
of Chemistry and Centre for Processable Electronics, Imperial College London, London W12 0BZ, United Kingdom
| | - Thomas R. Hopper
- Department
of Chemistry and Centre for Processable Electronics, Imperial College London, London W12 0BZ, United Kingdom
- Department
of Materials Science and Engineering, Stanford
University, Stanford, California 94305, United States
| | - Navendu Mondal
- Department
of Chemistry and Centre for Processable Electronics, Imperial College London, London W12 0BZ, United Kingdom
| | - Sihui Liu
- Department
of Chemistry and Centre for Processable Electronics, Imperial College London, London W12 0BZ, United Kingdom
| | - Chengning Yao
- Department
of Chemistry and Centre for Processable Electronics, Imperial College London, London W12 0BZ, United Kingdom
| | - Xijia Zheng
- Department
of Chemistry and Centre for Processable Electronics, Imperial College London, London W12 0BZ, United Kingdom
| | - Felice Torrisi
- Department
of Chemistry and Centre for Processable Electronics, Imperial College London, London W12 0BZ, United Kingdom
- Dipartimento
di Fisica e Astronomia, Universita’
di Catania & CNR-IMM (Catania Universita’), Via S. Sofia 64, 95123 Catania, Italy
| | - Artem A. Bakulin
- Department
of Chemistry and Centre for Processable Electronics, Imperial College London, London W12 0BZ, United Kingdom
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2
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Kim H, Im J, Nam K, Han GH, Park JY, Yoo S, Haddadnezhad M, Park S, Park W, Ahn JS, Park D, Jeong MS, Choi S. Plasmon-exciton couplings in the MoS 2/AuNP plasmonic hybrid structure. Sci Rep 2022; 12:22252. [PMID: 36564476 PMCID: PMC9789063 DOI: 10.1038/s41598-022-26485-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Accepted: 12/15/2022] [Indexed: 12/24/2022] Open
Abstract
The understanding and engineering of the plasmon-exciton coupling are necessary to control the innovative optoelectronic device platform. In this study, we investigated the intertwined mechanism of each plasmon-exciton couplings in monolayer molybdenum disulfide (MoS2) and plasmonic hybrid structure. The results of absorption, simulation, electrostatics, and emission spectra show that interaction between photoexcited carrier and exciton modes are successfully coupled by energy transfer and exciton recombination processes. Especially, neutral exciton, trion, and biexciton can be selectively enhanced by designing the plasmonic hybrid platform. All of these results imply that there is another degree of freedom to control the individual enhancement of each exciton mode in the development of nano optoelectronic devices.
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Affiliation(s)
- Hyuntae Kim
- grid.412977.e0000 0004 0532 7395Department of Physics, Incheon National University, Incheon, 22012 Republic of Korea
| | - Jaeseung Im
- grid.412977.e0000 0004 0532 7395Department of Physics, Incheon National University, Incheon, 22012 Republic of Korea
| | - Kiin Nam
- grid.412977.e0000 0004 0532 7395Department of Physics, Incheon National University, Incheon, 22012 Republic of Korea
| | - Gang Hee Han
- grid.412977.e0000 0004 0532 7395Department of Physics, Incheon National University, Incheon, 22012 Republic of Korea
| | - Jin Young Park
- grid.412977.e0000 0004 0532 7395Department of Physics, Incheon National University, Incheon, 22012 Republic of Korea
| | - Sungjae Yoo
- grid.264381.a0000 0001 2181 989XDepartment of Chemistry, Sungkyunkwan University, Suwon, 16419 Republic of Korea
| | - MohammadNavid Haddadnezhad
- grid.264381.a0000 0001 2181 989XDepartment of Chemistry, Sungkyunkwan University, Suwon, 16419 Republic of Korea
| | - Sungho Park
- grid.264381.a0000 0001 2181 989XDepartment of Chemistry, Sungkyunkwan University, Suwon, 16419 Republic of Korea
| | - Woongkyu Park
- grid.482524.d0000 0004 0614 4232Medical and Bio Photonics Research Center, Korea Photonics Technology Institute (KOPTI), Gwangju, 61007 Republic of Korea
| | - Jae Sung Ahn
- grid.482524.d0000 0004 0614 4232Medical and Bio Photonics Research Center, Korea Photonics Technology Institute (KOPTI), Gwangju, 61007 Republic of Korea
| | - Doojae Park
- grid.256753.00000 0004 0470 5964Department of Applied Optics and Physics, Hallym University, Chuncheon, 24252 Republic of Korea
| | - Mun Seok Jeong
- grid.49606.3d0000 0001 1364 9317Department of Physics, Hanyang University, Seoul, 04763 Republic of Korea ,grid.49606.3d0000 0001 1364 9317Department of Energy Engineering, Hanyang University, Seoul, 04763 Republic of Korea
| | - Soobong Choi
- grid.412977.e0000 0004 0532 7395Department of Physics, Incheon National University, Incheon, 22012 Republic of Korea
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3
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Sharma A, Zhu Y, Halbich R, Sun X, Zhang L, Wang B, Lu Y. Engineering the Dynamics and Transport of Excitons, Trions, and Biexcitons in Monolayer WS 2. ACS APPLIED MATERIALS & INTERFACES 2022; 14:41165-41177. [PMID: 36048513 DOI: 10.1021/acsami.2c08199] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The study of transport and diffusion dynamics of quasi-particles such as excitons, trions, and biexcitons in two-dimensional (2D) semiconductors has opened avenues for their application in high-speed excitonic and optoelectronic devices. However, long-range transport and fast diffusion of these quasi-particles have not been reported for 2D systems such as transition metal dichalcogenides (TMDCs). The reported diffusion coefficients from TMDCs are low, limiting their use in high-speed excitonic devices and other optoelectronic applications. Here, we report the highest exciton diffusion coefficient value in monolayer WS2 achieved via engineering the radiative lifetime and diffusion lengths using static back-gate voltage and substrate engineering. Electrostatic doping is observed to modulate the radiative lifetime and in turn the diffusion coefficient of excitons by ∼three times at room temperature. By combining electrostatic doping and substrate engineering, we push the diffusion coefficient to an extremely high value of 86.5 cm2/s, which has not been reported before in TMDCs and is even higher than the values in some 1D systems. At low temperatures, we further report the control of dynamic and spatial diffusion of excitons, trions, and biexcitons from WS2. The electrostatic control of dynamics and transport of these quasi-particles in monolayers establishes monolayer TMDCs as ideal candidates for high-speed excitonic circuits, optoelectronic, and photonic device applications.
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Affiliation(s)
- Ankur Sharma
- School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Yi Zhu
- School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
- Department of Engineering, University of Cambridge, Cambridge CB3 0FA, United Kingdom
| | - Robert Halbich
- School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Xueqian Sun
- School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Linglong Zhang
- School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Bowen Wang
- School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
| | - Yuerui Lu
- School of Engineering, College of Engineering and Computer Science, The Australian National University, Canberra, ACT 2601, Australia
- ARC Centre of Excellence in Quantum Computation and Communication Technology ANU Node, Canberra, ACT 2601, Australia
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4
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Hannan Mousavi S, Simchi H. Spin polarization in lateral two-dimensional heterostructures. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:145303. [PMID: 33498031 DOI: 10.1088/1361-648x/abdffd] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Accepted: 01/26/2021] [Indexed: 06/12/2023]
Abstract
In this work, we study the spin polarization in the MoS(Se)2-WS(Se)2transition metal dichalcogenide heterostructures by using the non-equilibrium Green's function method and a three-band tight-binding model near the edges of the first Brillouin zone. Although it has been shown that the structures have no significant spin polarization in a specific range of energy of electrons, by applying a transverse electric field in the sheet of the metal atoms, shedding light on the sample, and under a small bias voltage, a significant spin polarization in the structure could be created. Besides, by applying a suitable bias voltage between leads and applying the electric field, a noticeable spin polarization can be found even without shedding the light on the heterostructures.
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Affiliation(s)
- S Hannan Mousavi
- Electrical Engineering Department, Islamic Azad University, Central Tehran Branch, Tehran, Iran
| | - H Simchi
- Department of Physics, Iran University of Science and Technology, Narmak, Tehran 16844, Iran
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5
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Das S, Wang Y, Dai Y, Li S, Sun Z. Ultrafast transient sub-bandgap absorption of monolayer MoS 2. LIGHT, SCIENCE & APPLICATIONS 2021; 10:27. [PMID: 33514690 PMCID: PMC7846580 DOI: 10.1038/s41377-021-00462-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 12/21/2020] [Accepted: 12/30/2020] [Indexed: 05/23/2023]
Abstract
The light-matter interaction in materials is of remarkable interest for various photonic and optoelectronic applications, which is intrinsically determined by the bandgap of the materials involved. To extend the applications beyond the bandgap limit, it is of great significance to study the light-matter interaction below the material bandgap. Here, we report the ultrafast transient absorption of monolayer molybdenum disulfide in its sub-bandgap region from ~0.86 µm to 1.4 µm. Even though this spectral range is below the bandgap, we observe a significant absorbance enhancement up to ~4.2% in the monolayer molybdenum disulfide (comparable to its absorption within the bandgap region) due to pump-induced absorption by the excited carrier states. The different rise times of the transient absorption at different wavelengths indicate the various contributions of the different carrier states (i.e., real carrier states in the short-wavelength region of ~<1 µm, and exciton states in the long wavelength region of ~>1 µm). Our results elucidate the fundamental understanding regarding the optical properties, excited carrier states, and carrier dynamics in the technologically important near-infrared region, which potentially leads to various photonic and optoelectronic applications (e.g., excited-state-based photodetectors and modulators) of two-dimensional materials and their heterostructures beyond their intrinsic bandgap limitations.
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Affiliation(s)
- Susobhan Das
- Department of Electronics and Nanoengineering, Aalto University, 02150, Espoo, Finland.
| | - Yadong Wang
- Department of Electronics and Nanoengineering, Aalto University, 02150, Espoo, Finland
| | - Yunyun Dai
- Department of Electronics and Nanoengineering, Aalto University, 02150, Espoo, Finland
| | - Shisheng Li
- International Center for Young Scientists (ICYS), National Institute for Materials Science (NIMS), Tsukuba, Japan
| | - Zhipei Sun
- Department of Electronics and Nanoengineering, Aalto University, 02150, Espoo, Finland.
- QTF Centre of Excellence, Department of Applied Physics, Aalto University, Espoo, Finland.
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6
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Roest LI, van Heijst SE, Maduro L, Rojo J, Conesa-Boj S. Charting the low-loss region in electron energy loss spectroscopy with machine learning. Ultramicroscopy 2021; 222:113202. [PMID: 33453606 DOI: 10.1016/j.ultramic.2021.113202] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 12/22/2020] [Accepted: 01/05/2021] [Indexed: 11/25/2022]
Abstract
Exploiting the information provided by electron energy-loss spectroscopy (EELS) requires reliable access to the low-loss region where the zero-loss peak (ZLP) often overwhelms the contributions associated to inelastic scatterings off the specimen. Here we deploy machine learning techniques developed in particle physics to realise a model-independent, multidimensional determination of the ZLP with a faithful uncertainty estimate. This novel method is then applied to subtract the ZLP for EEL spectra acquired in flower-like WS2 nanostructures characterised by a 2H/3R mixed polytypism. From the resulting subtracted spectra we determine the nature and value of the bandgap of polytypic WS2, finding EBG=1.6-0.2+0.3eV with a clear preference for an indirect bandgap. Further, we demonstrate how this method enables us to robustly identify excitonic transitions down to very small energy losses. Our approach has been implemented and made available in an open source Python package dubbed EELSfitter.
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Affiliation(s)
- Laurien I Roest
- Kavli Institute of Nanoscience, Delft University of Technology, 2628CJ Delft, The Netherlands; Nikhef Theory Group, Science Park 105, 1098 XG Amsterdam, The Netherlands
| | - Sabrya E van Heijst
- Kavli Institute of Nanoscience, Delft University of Technology, 2628CJ Delft, The Netherlands
| | - Louis Maduro
- Kavli Institute of Nanoscience, Delft University of Technology, 2628CJ Delft, The Netherlands
| | - Juan Rojo
- Nikhef Theory Group, Science Park 105, 1098 XG Amsterdam, The Netherlands; Department of Physics and Astronomy, VU, 1081 HV Amsterdam, The Netherlands
| | - Sonia Conesa-Boj
- Kavli Institute of Nanoscience, Delft University of Technology, 2628CJ Delft, The Netherlands.
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7
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Eroglu ZE, Comegys O, Quintanar LS, Azam N, Elafandi S, Mahjouri-Samani M, Boulesbaa A. Ultrafast dynamics of exciton formation and decay in two-dimensional tungsten disulfide (2D-WS 2) monolayers. Phys Chem Chem Phys 2020; 22:17385-17393. [PMID: 32705108 DOI: 10.1039/d0cp03220d] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Excitons in two-dimensional transition metal dichalcogenide monolayers (2D-TMDs) are of essential importance due to their key involvement in 2D-TMD-based applications. For instance, exciton dissociation and exciton radiative recombination are indispensible processes in photovoltaic and light-emitting devices, respectively. These two processes depend drastically on the photogeneration efficiency and lifetime of excitons. Here, we incorporate femtosecond pump-probe spectroscopy to investigate the ultrafast dynamics of exciton formation and decay in a single crystal of monolayer 2D tungsten disulfide (WS2). Investigation of the formation dynamics of the lowest exciton (XA) indicated that the formation time linearly increases from ∼150 fs upon resonant excitation, to ∼500 fs following excitation that is ∼1.1 eV above the band-gap. This dependence is attributed to the time it takes highly excited electrons in the conduction band (CB) to relax to the CB minimum (CBM) and contribute to the formation of XA. This is confirmed by infrared measurements of electron intraband relaxation dynamics. Furthermore, pump-probe experiments suggested that the XA ground state depletion recovery dynamics depend on the excitation energy as well. The average recovery time increased from ∼10 ps in the case of resonant excitation to ∼50 ps following excitation well above the band-gap. Having the ability to control whether generating short-lived or long-lived electron-hole pairs in 2D-TMD monolayers opens a new horizon for the application of these materials. For instance, long-lived electron-hole pairs are appropriate for photovoltaic devices, but short-lived excitons are more beneficial for lasers with ultrashort pulses.
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Affiliation(s)
- Zeynep Ezgi Eroglu
- Department of Chemistry & Biochemistry, California State University, Northridge, 18111 Nordhoff Street, Northridge, 91330 CA, USA.
| | - Olivia Comegys
- Department of Chemistry & Biochemistry, California State University, Northridge, 18111 Nordhoff Street, Northridge, 91330 CA, USA.
| | - Leo S Quintanar
- Department of Chemistry & Biochemistry, California State University, Northridge, 18111 Nordhoff Street, Northridge, 91330 CA, USA.
| | - Nurul Azam
- Department of Electrical and Computer Engineering, Auburn University, Auburn, AL 36849, USA
| | - Salah Elafandi
- Department of Electrical and Computer Engineering, Auburn University, Auburn, AL 36849, USA
| | - Masoud Mahjouri-Samani
- Department of Electrical and Computer Engineering, Auburn University, Auburn, AL 36849, USA
| | - Abdelaziz Boulesbaa
- Department of Chemistry & Biochemistry, California State University, Northridge, 18111 Nordhoff Street, Northridge, 91330 CA, USA.
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8
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Lukman S, Ding L, Xu L, Tao Y, Riis-Jensen AC, Zhang G, Wu QYS, Yang M, Luo S, Hsu C, Yao L, Liang G, Lin H, Zhang YW, Thygesen KS, Wang QJ, Feng Y, Teng J. High oscillator strength interlayer excitons in two-dimensional heterostructures for mid-infrared photodetection. NATURE NANOTECHNOLOGY 2020; 15:675-682. [PMID: 32601449 DOI: 10.1038/s41565-020-0717-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Accepted: 05/19/2020] [Indexed: 05/12/2023]
Abstract
The development of infrared photodetectors is mainly limited by the choice of available materials and the intricate crystal growth process. Moreover, thermally activated carriers in traditional III-V and II-VI semiconductors enforce low operating temperatures in the infrared photodetectors. Here we demonstrate infrared photodetection enabled by interlayer excitons (ILEs) generated between tungsten and hafnium disulfide, WS2/HfS2. The photodetector operates at room temperature and shows an even higher performance at higher temperatures owing to the large exciton binding energy and phonon-assisted optical transition. The unique band alignment in the WS2/HfS2 heterostructure allows interlayer bandgap tuning from the mid- to long-wave infrared spectrum. We postulate that the sizeable charge delocalization and ILE accumulation at the interface result in a greatly enhanced oscillator strength of the ILEs and a high responsivity of the photodetector. The sensitivity of ILEs to the thickness of two-dimensional materials and the external field provides an excellent platform to realize robust tunable room temperature infrared photodetectors.
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Affiliation(s)
- Steven Lukman
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Lu Ding
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Lei Xu
- Department of Physics, National University of Singapore, Singapore, Singapore
| | - Ye Tao
- School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, Singapore
| | - Anders C Riis-Jensen
- CAMD and Center for Nanostructured Graphene (CNG), Department of Physics, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Gang Zhang
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Qing Yang Steve Wu
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Ming Yang
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
- Department of Physics, National University of Singapore, Singapore, Singapore
| | - Sheng Luo
- Department of Electrical and Computer Engineering, Faculty of Engineering, National University of Singapore, Singapore, Singapore
| | - Chuanghan Hsu
- Department of Electrical and Computer Engineering, Faculty of Engineering, National University of Singapore, Singapore, Singapore
| | - Liangzi Yao
- Institute of Physics, Academia Sinica, Taipei, Taiwan
| | - Gengchiau Liang
- Department of Electrical and Computer Engineering, Faculty of Engineering, National University of Singapore, Singapore, Singapore
| | - Hsin Lin
- Institute of Physics, Academia Sinica, Taipei, Taiwan
| | - Yong-Wei Zhang
- Institute of High Performance Computing, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Kristian S Thygesen
- CAMD and Center for Nanostructured Graphene (CNG), Department of Physics, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Qi Jie Wang
- School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, Singapore
| | - Yuanping Feng
- Department of Physics, National University of Singapore, Singapore, Singapore
| | - Jinghua Teng
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore.
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9
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MOYNIHAN EOIN, ROST STEFAN, O'CONNELL EOGHAN, RAMASSE QUENTIN, FRIEDRICH CHRISTOPH, BANGERT URSEL. Plasmons in MoS
2
studied via experimental and theoretical correlation of energy loss spectra. J Microsc 2020; 279:256-264. [DOI: 10.1111/jmi.12900] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2019] [Revised: 02/21/2020] [Accepted: 05/08/2020] [Indexed: 11/30/2022]
Affiliation(s)
- EOIN MOYNIHAN
- TEMUL, Department of PhysicsSchool of Sciences & Bernal Institute, University of Limerick Limerick Ireland
| | - STEFAN ROST
- Peter Grünberg Institut and Institute for Advanced Simulation Forschungszentrum Jülich and JARAGermany and RWTH Aachen University Aachen Germany
| | - EOGHAN O'CONNELL
- TEMUL, Department of PhysicsSchool of Sciences & Bernal Institute, University of Limerick Limerick Ireland
| | | | - CHRISTOPH FRIEDRICH
- Peter Grünberg Institut and Institute for Advanced Simulation Forschungszentrum Jülich and JARA Jülich Germany
| | - URSEL BANGERT
- TEMUL, Department of PhysicsSchool of Sciences & Bernal Institute, University of Limerick Limerick Ireland
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