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Zhou Z, Lin JF, Zeng Z, Ma X, Liang L, Li Y, Zhao Z, Mei Z, Yang H, Li Q, Wu J, Fan S, Chen X, Xia TL, Wei Y. Engineering van der Waals Contacts by Interlayer Dipoles. Nano Lett 2024; 24:4408-4414. [PMID: 38567928 DOI: 10.1021/acs.nanolett.4c00056] [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: 04/18/2024]
Abstract
Tuning the interfacial Schottky barrier with van der Waals (vdW) contacts is an important solution for two-dimensional (2D) electronics. Here we report that the interlayer dipoles of 2D vdW superlattices (vdWSLs) can be used to engineer vdW contacts to 2D semiconductors. A bipolar WSe2 with Ba6Ta11S28 (BTS) vdW contact was employed to exhibit this strategy. Strong interlayer dipoles can be formed due to charge transfer between the Ba3TaS5 and TaS2 layers. Mechanical exfoliation breaks the superlattice and produces two distinguished surfaces with TaS2 and Ba3TaS5 terminations. The surfaces thus have opposite surface dipoles and consequently different work functions. Therefore, all the devices fall into two categories in accordance with the rectifying direction, which were verified by electrical measurements and scanning photocurrent microscopy. The growing vdWSL family along with the addition surface dipoles enables prospective vdW contact designs and have practical application in nanoelectronics and nano optoelectronics.
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Affiliation(s)
- Zuoping Zhou
- Department of Physics, Tsinghua University, Beijing 100084, China
- Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084, China
- State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084, China
| | - Jun-Fa Lin
- Department of Physics and Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, P. R. China
| | - Zimeng Zeng
- Department of Physics, Tsinghua University, Beijing 100084, China
- State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084, China
| | - Xiaoping Ma
- Department of Physics and Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, P. R. China
- Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Liang Liang
- Department of Physics, Tsinghua University, Beijing 100084, China
- Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084, China
| | - Yuheng Li
- Department of Physics, Tsinghua University, Beijing 100084, China
- Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084, China
- State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084, China
| | - Zhongyuan Zhao
- Department of Physics, Tsinghua University, Beijing 100084, China
- Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084, China
- State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084, China
| | - Zhen Mei
- Department of Physics, Tsinghua University, Beijing 100084, China
- Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084, China
- State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084, China
| | - Huaixin Yang
- Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Qunqing Li
- Department of Physics, Tsinghua University, Beijing 100084, China
- Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084, China
- State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084, China
| | - Jian Wu
- Department of Physics, Tsinghua University, Beijing 100084, China
- State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084, China
| | - Shoushan Fan
- Department of Physics, Tsinghua University, Beijing 100084, China
- Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084, China
- State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084, China
| | - Xi Chen
- Department of Physics, Tsinghua University, Beijing 100084, China
- Frontier Science Center for Quantum Information, Beijing 100084, China
| | - Tian-Long Xia
- Department of Physics and Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, P. R. China
- Key Laboratory of Quantum State Construction and Manipulation (Ministry of Education) and Laboratory for Neutron Scattering, Renmin University of China, Beijing 100872, P. R. China
| | - Yang Wei
- Department of Physics, Tsinghua University, Beijing 100084, China
- Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084, China
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Aliyar T, Ma H, Krishnan R, Singh G, Chong BQ, Wang Y, Verzhbitskiy I, Yu Wong CP, Johnson Goh KE, Shen ZX, Koh TS, Rahman R, Weber B. Symmetry Breaking and Spin-Orbit Coupling for Individual Vacancy-Induced In-Gap States in MoS 2 Monolayers. Nano Lett 2024; 24:2142-2148. [PMID: 38323571 DOI: 10.1021/acs.nanolett.3c03681] [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: 02/08/2024]
Abstract
Spins confined to point defects in atomically thin semiconductors constitute well-defined atomic-scale quantum systems that are being explored as single-photon emitters and spin qubits. Here, we investigate the in-gap electronic structure of individual sulfur vacancies in molybdenum disulfide (MoS2) monolayers using resonant tunneling scanning probe spectroscopy in the Coulomb blockade regime. Spectroscopic mapping of defect wave functions reveals an interplay of local symmetry breaking by a charge-state-dependent Jahn-Teller lattice distortion that, when combined with strong (≃100 meV) spin-orbit coupling, leads to a locking of an unpaired spin-1/2 magnetic moment to the lattice at low temperature, susceptible to lattice strain. Our results provide new insights into the spin and electronic structure of vacancy-induced in-gap states toward their application as electrically and optically addressable quantum systems.
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Affiliation(s)
- Thasneem Aliyar
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Hongyang Ma
- School of Physics, University of New South Wales, Sydney, NSW 2052, Australia
| | - Radha Krishnan
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Gagandeep Singh
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Bi Qi Chong
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Yitao Wang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Ivan Verzhbitskiy
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore 138634, Singapore
| | - Calvin Pei Yu Wong
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore 138634, Singapore
| | - Kuan Eng Johnson Goh
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore 138634, Singapore
| | - Ze Xiang Shen
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Teck Seng Koh
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Rajib Rahman
- School of Physics, University of New South Wales, Sydney, NSW 2052, Australia
| | - Bent Weber
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
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3
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Sharma S, Dewhurst JK, Shallcross S. Light-Shaping of Valley States. Nano Lett 2023; 23:11533-11539. [PMID: 38100087 DOI: 10.1021/acs.nanolett.3c03245] [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: 12/28/2023]
Abstract
The established paradigm to create valley states, excitations at local band extrema ("valleys"), is through selective occupation of specific valleys via circularly polarized laser pulses. Here we show a second way exists to create valley states, not by valley population imbalance but by "light-shaping" in momentum space, i.e. controlling the shape of the distribution of excited charge at each valley. While noncontrasting in valley charge, such valley states are instead characterized by a valley current, identically zero at one valley and finite and large at the other. We demonstrate that these (i) are robust to quantum decoherence, (ii) allow lossless toggling of the valley state with successive femtosecond laser pulses, and (iii) permit valley contrasting excitation both with and without a gap. Our findings open a route to robust ultrafast and switchable valleytronics in a wide scope of 2d materials, bringing closer the promise of valley-based electronics.
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Affiliation(s)
- Sangeeta Sharma
- Max-Born-Institute for Non-linear Optics and Short Pulse Spectroscopy, Max-Born Strasse 2A, 12489 Berlin, Germany
- Institute for theoretical solid-state physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - John Kay Dewhurst
- Max-Planck-Institut fur Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany
| | - Samuel Shallcross
- Max-Born-Institute for Non-linear Optics and Short Pulse Spectroscopy, Max-Born Strasse 2A, 12489 Berlin, Germany
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4
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Zhao H, Zhu L, Li X, Chandrasekaran V, Baldwin JK, Pettes MT, Piryatinski A, Yang L, Htoon H. Manipulating Interlayer Excitons for Near-Infrared Quantum Light Generation. Nano Lett 2023. [PMID: 38038967 DOI: 10.1021/acs.nanolett.3c03296] [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: 12/02/2023]
Abstract
Interlayer excitons (IXs) formed at the interface of van der Waals materials possess various novel properties. In parallel development, strain engineering has emerged as an effective means for creating 2D quantum emitters. Exploring the intersection of these two exciting areas, we use MoS2/WSe2 heterostructure as a model system and demonstrate how strain, defects, and layering can be utilized to create defect-bound IXs capable of bright, robust, and tunable quantum light emission in the technologically important near-infrared spectral range. Our work presents defect-bound IXs as a promising platform for pushing the performance of 2D quantum emitters beyond their current limitations.
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Affiliation(s)
- Huan Zhao
- Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Linghan Zhu
- Department of Physics, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Xiangzhi Li
- Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Vigneshwaran Chandrasekaran
- Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Jon Kevin Baldwin
- Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Michael T Pettes
- Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Andrei Piryatinski
- Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Li Yang
- Department of Physics, Washington University in St. Louis, St. Louis, Missouri 63130, United States
- Institute of Materials Science and Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Han Htoon
- Center for Integrated Nanotechnologies, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
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5
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Kuo CY, Chang YT, Huang YT, Ni IC, Chen MH, Wu CI. MoS 2 as an Effective Cu Diffusion Barrier with a Back-End Compatible Process. ACS Appl Mater Interfaces 2023; 15:47845-47854. [PMID: 37768847 DOI: 10.1021/acsami.3c12267] [Citation(s) in RCA: 2] [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: 09/30/2023]
Abstract
This study demonstrates molybdenum disulfide (MoS2) as a superior candidate as a diffusion barrier and liner. This research explores a newly developed process to show how effectively MoS2 can be applied. First, a new approach is developed to prepare molybdenum disulfide (MoS2) by microwave plasma-enhanced sulfurization (MW-PES). MW-PES can rapidly and directly grow on the target substrate at low temperatures, which is compatible with the back-end-of-line (BEOL) technology. Second, the performance of MW-PES MoS2 as a diffusion barrier and liner is reported in the subsequent section. Through time-dependent dielectric breakdown (TDDB) measurements, MoS2 is shown to have a barrier property better than that of the current material, Ta, with the same thickness. According to the model fitting, the lifetime of the device is about 45.2 times the lifetime under normal operating conditions. Furthermore, MoS2 shows its superior thermal stability in maintaining the barrier properties. MoS2 is proven to be an excellent interface as a liner as it can provide sufficient adhesion and wettability to further effectively reduce the surface scattering of copper (Cu) and significantly lower the circuit resistance.
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Affiliation(s)
- Chi-Yuan Kuo
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei 106, Taiwan
| | - Ya-Ting Chang
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei 106, Taiwan
| | - Yu-Ting Huang
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei 106, Taiwan
| | - I-Chih Ni
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei 106, Taiwan
| | - Mei-Hsin Chen
- Department of Electro-Optical Engineering, National Taipei University of Technology, Taipei 106, Taiwan
| | - Chih-I Wu
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei 106, Taiwan
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6
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Krishnan R, Biswas S, Hsueh YL, Ma H, Rahman R, Weber B. Spin-Valley Locking for In-Gap Quantum Dots in a MoS 2 Transistor. Nano Lett 2023. [PMID: 37363814 DOI: 10.1021/acs.nanolett.3c01779] [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: 06/28/2023]
Abstract
Spins confined to atomically thin semiconductors are being actively explored as quantum information carriers. In transition metal dichalcogenides (TMDCs), the hexagonal crystal lattice gives rise to an additional valley degree of freedom with spin-valley locking and potentially enhanced spin life and coherence times. However, realizing well-separated single-particle levels and achieving transparent electrical contact to address them has remained challenging. Here, we report well-defined spin states in a few-layer MoS2 transistor, characterized with a spectral resolution of ∼50 μeV at Tel = 150 mK. Ground state magnetospectroscopy confirms a finite Berry-curvature induced coupling of spin and valley, reflected in a pronounced Zeeman anisotropy, with a large out-of-plane g-factor of g⊥ ≃ 8. A finite in-plane g-factor (g∥ ≃ 0.55-0.8) allows us to quantify spin-valley locking and estimate the spin-orbit splitting 2ΔSO ∼ 100 μeV. The demonstration of spin-valley locking is an important milestone toward realizing spin-valley quantum bits.
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Affiliation(s)
- Radha Krishnan
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371
| | - Sangram Biswas
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371
| | - Yu-Ling Hsueh
- School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Hongyang Ma
- School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Rajib Rahman
- School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Bent Weber
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371
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7
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Kayal A, Dey S, G H, Nadarajan R, Chattopadhyay S, Mitra J. Mobility Enhancement in CVD-Grown Monolayer MoS 2 Via Patterned Substrate-Induced Nonuniform Straining. Nano Lett 2023. [PMID: 37347123 DOI: 10.1021/acs.nanolett.3c01774] [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] [Subscribe] [Scholar Register] [Indexed: 06/23/2023]
Abstract
The extraordinary mechanical properties of two-dimensional transition-metal dichalcogenides make them ideal candidates for investigating strain-induced control of various physical properties. Here we explore the role of nonuniform strain in modulating optical, electronic, and transport properties of semiconducting, chemical vapor deposited monolayer MoS2, on periodically nanostructured substrates. A combination of spatially resolved spectroscopic and electronic properties explore and quantify the differential strain distribution and carrier density on a monolayer, as it conformally drapes over the periodic nanostructures. The observed accumulation in electron density at the strained regions is supported by theoretical calculations which form the likely basis for the ensuing ×60 increase in field effect mobility in strained samples. Though spatially nonuniform, the pattern-induced strain is shown to be readily controlled by changing the periodicity of the nanostructures thus providing a robust yet useful macroscopic control on strain and mobility in these systems.
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Affiliation(s)
- Arijit Kayal
- School of Physics, IISER Thiruvananthapuram, Trivandrum, Kerala 695551, India
| | - Sraboni Dey
- School of Physics, IISER Thiruvananthapuram, Trivandrum, Kerala 695551, India
| | - Harikrishnan G
- School of Physics, IISER Thiruvananthapuram, Trivandrum, Kerala 695551, India
| | - Renjith Nadarajan
- School of Physics, IISER Thiruvananthapuram, Trivandrum, Kerala 695551, India
| | | | - Joy Mitra
- School of Physics, IISER Thiruvananthapuram, Trivandrum, Kerala 695551, India
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8
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Azam N, Mahjouri-Samani M. Time-Resolved Growth of 2D WSe 2 Monolayer Crystals. ACS Nano 2023. [PMID: 37339265 DOI: 10.1021/acsnano.3c02280] [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: 06/22/2023]
Abstract
Understanding and controlling the growth evolution of atomically thin monolayer two-dimensional (2D) materials such as transition metal dichalcogenides (TMDCs) are vital for next-generation 2D electronics and optoelectronic devices. However, their growth kinetics are not fully observed or well understood due to the bottlenecks associated with the existing synthesis methods. This study demonstrates the time-resolved and ultrafast growth of 2D materials by a laser-based synthesis approach that enables the rapid initiation and termination of the vaporization process during crystal growth. The use of stoichiometric powder (e.g., WSe2) minimizes the complex chemistry during the vaporization and growth process, allowing rapid initiation/termination control over the generated flux. An extensive set of experiments is performed to understand the growth evolution, achieving subsecond growth as low as 10 ms along with a 100 μm/s growth rate on a noncatalytic substrate such as Si/SiO2. Overall, this study allows us to observe and understand the 2D crystal evolution and growth kinetics with time-resolved and subsecond time scales.
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Affiliation(s)
- Nurul Azam
- Electrical and Computer Engineering Department, Auburn University, Auburn, Alabama 36849, United States
| | - Masoud Mahjouri-Samani
- Electrical and Computer Engineering Department, Auburn University, Auburn, Alabama 36849, United States
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9
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Juvêncio Ramalho Costa F, Brito TGL, Barcelos ID, Zagonel LF. Impacts of dielectric screening on the luminescence of monolayer WSe 2. Nanotechnology 2023. [PMID: 37257442 DOI: 10.1088/1361-6528/acda3b] [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: 06/02/2023]
Abstract
Single layers of transition metal dichalcogenides, such as WSe2 have gathered increasing attention due to their intense electron-hole interactions, being considered promising candidates for developing novel optical applications. Within the few-layer regime, these systems become highly sensitive to the surrounding environment, enabling the possibility of using a proper substrate to tune desired aspects of these atomically-thin semiconductors. In this scenario, the dielectric environment provided by the substrates exerts significant influence on electronic and optical properties of these layered materials, affecting the electronic band-gap and the exciton binding energy. However, the corresponding effect on the luminescence of transition metal dichalcogenides is still under discussion. To elucidate these impacts, we used a broad set of materials as substrates for single-layers of WSe2, enabling the observation of these effects over a wide range of electrical permittivities. Our results demonstrate that an increasing permittivity induces a systematic red-shift of the optical band-gap of WSe2, intrinsically related to a considerable reduction of the luminescence intensity. Moreover, we annealed the samples to ensure a tight coupling between WSe2 and its substrates, reducing the effect of undesired adsorbates trapped in the interface. Ultimately, our findings reveal how critical the annealing temperature can be, indicating that above a certain threshold, the heating treatment can induce adverse impacts on the luminescence. Furthermore, our conclusions highlight the influence the dielectric properties of the substrate have on the luminescence of WSe2, showing that a low electrical permittivity favours preserving the native properties of the adjacent monolayer.
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Affiliation(s)
| | - Thiago Gonzalez-Llana Brito
- Applied Physics, State University of Campinas, "Gleb Wataghin" Institute of Physics", Sérgio Buarque de Holanda Street, University city 13083859, Campinas, São Paulo, 13083-872, BRAZIL
| | - Ingrid David Barcelos
- Laboratório Nacional de Luz Síncrotron , Centro Nacional de Pesquisa em Energia e Materiais, Rua Giuseppe Maximo Scolfaro, 10000, Campinas, 13083-970, BRAZIL
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10
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Ji J, Kwak HM, Yu J, Park S, Park JH, Kim H, Kim S, Kim S, Lee DS, Kum HS. Understanding the 2D-material and substrate interaction during epitaxial growth towards successful remote epitaxy: a review. Nano Converg 2023; 10:19. [PMID: 37115353 PMCID: PMC10147895 DOI: 10.1186/s40580-023-00368-4] [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] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Accepted: 04/09/2023] [Indexed: 06/19/2023]
Abstract
Remote epitaxy, which was discovered and reported in 2017, has seen a surge of interest in recent years. Although the technology seemed to be difficult to reproduce by other labs at first, remote epitaxy has come a long way and many groups are able to consistently reproduce the results with a wide range of material systems including III-V, III-N, wide band-gap semiconductors, complex-oxides, and even elementary semiconductors such as Ge. As with any nascent technology, there are critical parameters which must be carefully studied and understood to allow wide-spread adoption of the new technology. For remote epitaxy, the critical parameters are the (1) quality of two-dimensional (2D) materials, (2) transfer or growth of 2D materials on the substrate, (3) epitaxial growth method and condition. In this review, we will give an in-depth overview of the different types of 2D materials used for remote epitaxy reported thus far, and the importance of the growth and transfer method used for the 2D materials. Then, we will introduce the various growth methods for remote epitaxy and highlight the important points in growth condition for each growth method that enables successful epitaxial growth on 2D-coated single-crystalline substrates. We hope this review will give a focused overview of the 2D-material and substrate interaction at the sample preparation stage for remote epitaxy and during growth, which have not been covered in any other review to date.
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Affiliation(s)
- Jongho Ji
- Department of Electrical and Electronic Engineering, Yonsei University, Seoul, South Korea
| | - Hoe-Min Kwak
- School of Electrical Engineering and Computer Science, Gwnagju Institute of Science and Technology, Gwangju, South Korea
| | - Jimyeong Yu
- Department of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul, South Korea
| | - Sangwoo Park
- Department of Electrical and Electronic Engineering, Yonsei University, Seoul, South Korea
| | - Jeong-Hwan Park
- Venture Business Laboratory, Nagoya University, Furo-Cho, Chikusa-ku, Nagoya, 464-8603, Japan
| | - Hyunsoo Kim
- Department of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul, South Korea
| | - Seokgi Kim
- Department of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul, South Korea
| | - Sungkyu Kim
- Department of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul, South Korea.
| | - Dong-Seon Lee
- School of Electrical Engineering and Computer Science, Gwnagju Institute of Science and Technology, Gwangju, South Korea.
| | - Hyun S Kum
- Department of Electrical and Electronic Engineering, Yonsei University, Seoul, South Korea.
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11
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Torun E, Paleari F, Milošević MV, Wirtz L, Sevik C. Intrinsic Control of Interlayer Exciton Generation in Van der Waals Materials via Janus Layers. Nano Lett 2023; 23:3159-3166. [PMID: 37037187 DOI: 10.1021/acs.nanolett.2c04724] [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: 06/19/2023]
Abstract
We demonstrate the possibility of engineering the optical properties of transition metal dichalcogenide heterobilayers when one of the constitutive layers has a Janus structure. We investigate different MoS2@Janus layer combinations using first-principles methods including excitons and exciton-phonon coupling. The direction of the intrinsic electric field from the Janus layer modifies the electronic band alignments and, consequently, the energy separation between dark interlayer exciton states and bright in-plane excitons. We find that in-plane lattice vibrations strongly couple the two states, so that exciton-phonon scattering may be a viable generation mechanism for interlayer excitons upon light absorption. In particular, in the case of MoS2@WSSe, the energy separation of the low-lying interlayer exciton from the in-plane exciton is resonant with the transverse optical phonon modes (40 meV). We thus identify this heterobilayer as a prime candidate for efficient generation of charge-separated electron-hole pairs.
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Affiliation(s)
- Engin Torun
- Department of Physics and Materials Science, University of Luxembourg, 162a avenue de la Faïencerie, Luxembourg L-1511, Luxembourg
| | | | - Milorad V Milošević
- Department of Physics & NANOlab Center of Excellence, University of Antwerp, Groenenborgerlaan 171, Antwerp B-2020, Belgium
- Instituto de Fisica, Universidade Federal de Mato Grosso, Cuiaba, Mato Grosso 78060-900, Brazil
| | - Ludger Wirtz
- Department of Physics and Materials Science, University of Luxembourg, 162a avenue de la Faïencerie, Luxembourg L-1511, Luxembourg
| | - Cem Sevik
- Department of Physics & NANOlab Center of Excellence, University of Antwerp, Groenenborgerlaan 171, Antwerp B-2020, Belgium
- Department of Mechanical Engineering, Faculty of Engineering, Eskisehir Technical University, Eskisehir 26555, Turkey
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Faria Junior PE, Fabian J. Signatures of Electric Field and Layer Separation Effects on the Spin-Valley Physics of MoSe 2/WSe 2 Heterobilayers: From Energy Bands to Dipolar Excitons. Nanomaterials (Basel) 2023; 13:1187. [PMID: 37049281 PMCID: PMC10096971 DOI: 10.3390/nano13071187] [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] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 03/22/2023] [Accepted: 03/24/2023] [Indexed: 06/19/2023]
Abstract
Multilayered van der Waals heterostructures based on transition metal dichalcogenides are suitable platforms on which to study interlayer (dipolar) excitons, in which electrons and holes are localized in different layers. Interestingly, these excitonic complexes exhibit pronounced valley Zeeman signatures, but how their spin-valley physics can be further altered due to external parameters-such as electric field and interlayer separation-remains largely unexplored. Here, we perform a systematic analysis of the spin-valley physics in MoSe2/WSe2 heterobilayers under the influence of an external electric field and changes of the interlayer separation. In particular, we analyze the spin (Sz) and orbital (Lz) degrees of freedom, and the symmetry properties of the relevant band edges (at K, Q, and Γ points) of high-symmetry stackings at 0° (R-type) and 60° (H-type) angles-the important building blocks present in moiré or atomically reconstructed structures. We reveal distinct hybridization signatures on the spin and the orbital degrees of freedom of low-energy bands, due to the wave function mixing between the layers, which are stacking-dependent, and can be further modified by electric field and interlayer distance variation. We find that H-type stackings favor large changes in the g-factors as a function of the electric field, e.g., from -5 to 3 in the valence bands of the Hhh stacking, because of the opposite orientation of Sz and Lz of the individual monolayers. For the low-energy dipolar excitons (direct and indirect in k-space), we quantify the electric dipole moments and polarizabilities, reflecting the layer delocalization of the constituent bands. Furthermore, our results show that direct dipolar excitons carry a robust valley Zeeman effect nearly independent of the electric field, but tunable by the interlayer distance, which can be rendered experimentally accessible via applied external pressure. For the momentum-indirect dipolar excitons, our symmetry analysis indicates that phonon-mediated optical processes can easily take place. In particular, for the indirect excitons with conduction bands at the Q point for H-type stackings, we find marked variations of the valley Zeeman (∼4) as a function of the electric field, which notably stands out from the other dipolar exciton species. Our analysis suggests that stronger signatures of the coupled spin-valley physics are favored in H-type stackings, which can be experimentally investigated in samples with twist angle close to 60°. In summary, our study provides fundamental microscopic insights into the spin-valley physics of van der Waals heterostructures, which are relevant to understanding the valley Zeeman splitting of dipolar excitonic complexes, and also intralayer excitons.
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Kim HJ, Chong M, Rhee TG, Khim YG, Jung MH, Kim YM, Jeong HY, Choi BK, Chang YJ. Machine-learning-assisted analysis of transition metal dichalcogenide thin-film growth. Nano Converg 2023; 10:10. [PMID: 36806667 PMCID: PMC9941396 DOI: 10.1186/s40580-023-00359-5] [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] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Accepted: 01/31/2023] [Indexed: 05/14/2023]
Abstract
In situ reflective high-energy electron diffraction (RHEED) is widely used to monitor the surface crystalline state during thin-film growth by molecular beam epitaxy (MBE) and pulsed laser deposition. With the recent development of machine learning (ML), ML-assisted analysis of RHEED videos aids in interpreting the complete RHEED data of oxide thin films. The quantitative analysis of RHEED data allows us to characterize and categorize the growth modes step by step, and extract hidden knowledge of the epitaxial film growth process. In this study, we employed the ML-assisted RHEED analysis method to investigate the growth of 2D thin films of transition metal dichalcogenides (ReSe2) on graphene substrates by MBE. Principal component analysis (PCA) and K-means clustering were used to separate statistically important patterns and visualize the trend of pattern evolution without any notable loss of information. Using the modified PCA, we could monitor the diffraction intensity of solely the ReSe2 layers by filtering out the substrate contribution. These findings demonstrate that ML analysis can be successfully employed to examine and understand the film-growth dynamics of 2D materials. Further, the ML-based method can pave the way for the development of advanced real-time monitoring and autonomous material synthesis techniques.
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Affiliation(s)
- Hyuk Jin Kim
- Department of Physics, University of Seoul, Seoul, 02504, Republic of Korea
| | - Minsu Chong
- Department of Physics, University of Seoul, Seoul, 02504, Republic of Korea
| | - Tae Gyu Rhee
- Department of Physics, University of Seoul, Seoul, 02504, Republic of Korea
- Department of Smart Cities, University of Seoul, Seoul, 02504, Republic of Korea
| | - Yeong Gwang Khim
- Department of Physics, University of Seoul, Seoul, 02504, Republic of Korea
- Department of Smart Cities, University of Seoul, Seoul, 02504, Republic of Korea
| | - Min-Hyoung Jung
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, 16419, Republic of Korea
| | - Young-Min Kim
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, 16419, Republic of Korea
| | - Hu Young Jeong
- Graduate School of Semiconductor Materials and Devices Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Byoung Ki Choi
- Department of Physics, University of Seoul, Seoul, 02504, Republic of Korea
- Advanced Light Source (ALS), E. O. Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Young Jun Chang
- Department of Physics, University of Seoul, Seoul, 02504, Republic of Korea.
- Department of Smart Cities, University of Seoul, Seoul, 02504, Republic of Korea.
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14
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Sanchez Rodriguez JJ, Nunez Leon AN, Abbasi J, Shinde PS, Fedin I, Gupta A. Colloidal Synthesis, Characterization, and Photoconductivity of Quasi-Layered CuCrS 2 Nanosheets. Nanomaterials (Basel) 2022; 12:4164. [PMID: 36500786 PMCID: PMC9736551 DOI: 10.3390/nano12234164] [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] [Figures] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Revised: 11/18/2022] [Accepted: 11/22/2022] [Indexed: 06/17/2023]
Abstract
The current need to accelerate the adoption of photovoltaic (PV) systems has increased the need to explore new nanomaterials that can harvest and convert solar energy into electricity. Transition metal dichalcogenides (TMDCs) are good candidates because of their tunable physical and chemical properties. CuCrS2 has shown good electrical and thermoelectrical properties; however, its optical and photoconductivity properties remain unexplored. In this study, we synthesized CuCrS2 nanosheets with average dimensions of 43.6 ± 6.7 nm in length and 25.6 ± 4.1 nm in width using a heat-up synthesis approach and fabricated films by the spray-coating method to probe their photoresponse. This method yielded CuCrS2 nanosheets with an optical bandgap of ~1.21 eV. The fabricated film had an average thickness of ~570 nm, exhibiting a net current conversion efficiency of ~11.3%. These results demonstrate the potential use of CuCrS2 as an absorber layer in solar cells.
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15
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Raju P, Zhu H, Yang Y, Zhang K, Ioannou D, Li Q. Steep-slope transistors enabled with 2D quantum coupling stacks. Nanotechnology 2022; 34:055001. [PMID: 36317282 DOI: 10.1088/1361-6528/ac9e5e] [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] [Received: 08/18/2022] [Accepted: 10/28/2022] [Indexed: 06/16/2023]
Abstract
As down scaling of transistors continues, there is a growing interest in developing steep-slope transistors with reduced subthreshold slope (SS) below the Boltzmann limit. In this work, we successfully fabricated steep-slope MoS2transistors by incorporating a graphene layer, inserted in the gate stack. For our comprehensive study, we have applied density functional theory to simulate and calculate the change of SS effected by different 2D quantum materials, including graphene, germanene and 2D topological insulators, inserted within the gate dielectric. This theoretical study showed that graphene/MoS2devices had steep SS (27.2 mV/decade), validating our experimental approach (49.2 mV/decade). Furthermore, the simulations demonstrated very steep SS (8.6 mV/decade) in WTe2/MoS2devices. We conclude that appropriate combination of various 2D quantum materials for the gate-channel stacks, leads to steep SS and is an effective method to extend the scaling of transistors with exceptional performance.
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Affiliation(s)
- Parameswari Raju
- Department of Electrical and Computer Engineering, Fairfax, George Mason University, Fairfax, VA 22030, United States of America
- Quantum Science & Engineering Center, George Mason University, Fairfax, VA 22030, United States of America
| | - Hao Zhu
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, People's Republic of China
| | - Yafen Yang
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, People's Republic of China
| | - Kai Zhang
- State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433, People's Republic of China
| | - Dimitris Ioannou
- Department of Electrical and Computer Engineering, Fairfax, George Mason University, Fairfax, VA 22030, United States of America
| | - Qiliang Li
- Department of Electrical and Computer Engineering, Fairfax, George Mason University, Fairfax, VA 22030, United States of America
- Quantum Science & Engineering Center, George Mason University, Fairfax, VA 22030, United States of America
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16
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Shi J, Lin Z, Zhu Z, Zhou J, Xu GQ, Xu QH. Probing Excitonic Rydberg States by Plasmon Enhanced Nonlinear Optical Spectroscopy in Monolayer WS 2 at Room Temperature. ACS Nano 2022; 16:15862-15872. [PMID: 36169603 DOI: 10.1021/acsnano.2c02276] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The optoelectronic properties of two-dimensional (2D) transition metal dichalcogenide (TMDC) monolayers such as WS2 are largely dominated by excitons due to strong Coulomb interactions in these 2D confined monolayers, which lead to formation of Rydberg-like excitonic states below the free quasiparticle band gap. The precise knowledge of high order Rydberg excitonic states is of great importance for both fundamental understanding such as many-electron effects and device applications such as optical switching and quantum process information. Bright excitonic states could be probed by linear optical spectroscopy, while probing dark excitonic states generally requires nonlinear optical (NLO) spectroscopy. Conventional optical methods for probing high-order Rydberg excitonic states were generally performed at cryogenic temperatures to ensure enough signal-to-noise ratio (SNR) and narrow line width. Here we have designed a hybrid nanostructure of monolayer WS2 integrated with a plasmonic cavity and investigated their NLO properties at the single particle level. Giant enhancement in NLO responses, stronger excitonic resonance effects, and narrowed line widths of NLO excitation spectra were observed when monolayer WS2 was placed in our carefully designed plasmonic cavity. Optimum enhancement of 1000-, 3000-, and 3800-fold were achieved for two-photon photoluminescence (2PPL), second harmonic generation (SHG), and third-harmonic generation (THG), respectively, in the optimized cavity structure. The line width of SHG excitation spectra was reduced from 43 down to 15 meV. Plasmon enhanced NLO responses brought improved SNR and spectral resolution, which allowed us to distinguish discrete excitonic states with small energy differences at room temperature. By using three complementary NLO techniques in combination with linear optical spectroscopy, energies of Rydberg excitonic states of A (1s, 2s, 2p, 3s, 3p, 4s), B (1s), and C and D excitons of monolayer WS2 have been accurately determined, which allow us to determine exciton binding energy and quasiparticle bandgap. It was interesting to find that the 2p lies 30 meV below 2s, which lends strong support to the theoretical prediction of nonlocal dielectric screening effects based on a non-hydrogenic model. Our results show that plasmon enhanced NLO spectroscopy could serve as a general method for probing high order Rydberg excitonic states of 2D materials.
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Affiliation(s)
- Jia Shi
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Zexin Lin
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Ziyu Zhu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Jiadong Zhou
- Key Lab of Advanced Optoelectronic Quantum Architecture and Measurement (Ministry of Education), Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems, and School of Physics, Beijing Institute of Technology, Beijing 100081, China
| | - Guo Qin Xu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
- National University of Singapore (Suzhou) Research Institute, Suzhou 215123, China
| | - Qing-Hua Xu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
- National University of Singapore (Suzhou) Research Institute, Suzhou 215123, China
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17
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Zabrosaev IV, Kozodaev MG, Romanov RI, Chernikova AG, Mishra P, Doroshina NV, Arsenin AV, Volkov VS, Koroleva AA, Markeev AM. Field-Effect Transistor Based on 2D Microcrystalline MoS 2 Film Grown by Sulfurization of Atomically Layer Deposited MoO 3. Nanomaterials (Basel) 2022; 12:3262. [PMID: 36234390 PMCID: PMC9565359 DOI: 10.3390/nano12193262] [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] [Figures] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 09/08/2022] [Accepted: 09/16/2022] [Indexed: 06/16/2023]
Abstract
Atomically thin molybdenum disulfide (MoS2) is a promising channel material for next-generation thin-body field-effect transistors (FETs), which makes the development of methods allowing for its controllable synthesis over a large area an essential task. Currently, one of the cost-effective ways of its synthesis is the sulfurization of preliminary grown oxide- or metallic film. However, despite apparent progress in this field, the electronic quality of the obtained MoS2 is inferior to that of exfoliated samples, making the detailed investigation of the sulfurized films' properties of great interest. In this work, we synthesized continuous MoS2 films with a thickness of ≈2.2 nm via the sulfurization of an atomic-layer-deposited MoO3 layer. X-ray photoelectron spectroscopy, transmission electron microscopy, and Raman spectroscopy indicated the appropriate chemical composition and microcrystalline structure of the obtained MoS2 films. The semiconductor quality of the synthesized films was confirmed by the fabrication of a field-effect transistor (FET) with an Ion/Ioff ratio of ≈40, which was limited primarily by the high contact resistance. The Schottky barrier height at the Au/MoS2 interface was found to be ≈1.2 eV indicating the necessity of careful contact engineering. Due to its simplicity and cost-effectiveness, such a technique of MoS2 synthesis still appears to be highly attractive for its applications in next-generation microelectronics. Therefore, further research of the electronic properties of films obtained via this technique is required.
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Affiliation(s)
- Ivan V. Zabrosaev
- Moscow Institute of Physics and Technology, National Research University, Institutskii per. 9, 141701 Dolgoprudny, Russia
| | - Maxim G. Kozodaev
- Moscow Institute of Physics and Technology, National Research University, Institutskii per. 9, 141701 Dolgoprudny, Russia
| | - Roman I. Romanov
- Moscow Institute of Physics and Technology, National Research University, Institutskii per. 9, 141701 Dolgoprudny, Russia
| | - Anna G. Chernikova
- Moscow Institute of Physics and Technology, National Research University, Institutskii per. 9, 141701 Dolgoprudny, Russia
| | - Prabhash Mishra
- Center for Photonics & 2D Materials, Moscow Institute of Physics and Technology, National Research University, 141700 Dolgoprudny, Russia
- Center for Nanoscience and Nanotechnology, Jamia Millia Islamia (Central University), New Delhi 110025, India
| | - Natalia V. Doroshina
- Center for Photonics & 2D Materials, Moscow Institute of Physics and Technology, National Research University, 141700 Dolgoprudny, Russia
| | - Aleksey V. Arsenin
- Center for Photonics & 2D Materials, Moscow Institute of Physics and Technology, National Research University, 141700 Dolgoprudny, Russia
| | - Valentyn S. Volkov
- Center for Photonics & 2D Materials, Moscow Institute of Physics and Technology, National Research University, 141700 Dolgoprudny, Russia
| | - Alexandra A. Koroleva
- Moscow Institute of Physics and Technology, National Research University, Institutskii per. 9, 141701 Dolgoprudny, Russia
| | - Andrey M. Markeev
- Moscow Institute of Physics and Technology, National Research University, Institutskii per. 9, 141701 Dolgoprudny, Russia
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18
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Acar M, Ertuğrul M, Gür E. Transfer-free, scalable vertical heterostructure FET on MoS 2/WS 2continuous films. Nanotechnology 2022; 33:475201. [PMID: 35970141 DOI: 10.1088/1361-6528/ac8997] [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] [Received: 03/01/2022] [Accepted: 08/14/2022] [Indexed: 06/15/2023]
Abstract
Taking into account the novel layered structure and unusual electronic properties of MoS2and WS2on the side the lack of dangling bonds between these two components and donor-acceptor linkage effects, growth of the MoS2/WS2vertical heterojunction film on the amorphous SiO2/Si substrate have created high demand. In this study, we reported the continuous, scalable, and vertical MoS2/WS2heterostructure film by using a sputtering without a transfer step. The WS2film was continuously grown on MoS2and eventually led to the formation of the MoS2/WS2vertical heterojunction film. Dozens of FETs fabricated on MoS2/WS2continuous heterojunction film were created on the same substrate in a single lithographic fabrication step, allowing them to be commercialized and not only used in research applications. RAMAN spectra proved the formation of the MoS2/WS2heterostructure film. In XPS measurements, it was shown that a separate MoS2and WS2layer was grown instead of the alloy structure. The polarity behavior of the MoS2/WS2heterostructure FET was found to be modulated with different drain voltages as p-type to ambipolar and finally n-type conductivity because of the transition of band structure and Schottky barrier heights at different drain voltages. Electron mobility (7.2 cm2V.s-1) and on/off ratio (104-105) exhibited by the MoS2/WS2heterostructure FETs displayed a more improved electrical performance than that of individual WS2, MoS2devices. It was observed that the mobility value of MoS2/WS2FET was approximately 514 times greater than WS2FET and 800 times greater than MoS2FET. Additionally, the MoS2/WS2FET on/off ratio was larger than 2 order MoS2FET and 1 order WS2FET. The film of continuous vertical heterojunctions as in the MoS2/WS2currents in the study would be a promising candidate for nanoelectronics fields. This work demonstrated the progress towards realizing carrier-type controlled high-performance MoS2/WS2heterojunction-based FETs for future logic devices.
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Affiliation(s)
- Merve Acar
- Department of Electrical and Electronics Engineering, Faculty of Engineering, Atatürk University, 25240, Erzurum, Turkey
| | - Mehmet Ertuğrul
- Department of Electrical and Electronics Engineering, Faculty of Engineering, Atatürk University, 25240, Erzurum, Turkey
- Department of Nanoscience and Nanotechnology, Graduate School of Natural and Applied Sciences, Ataturk University, 25240 Erzurum, Turkey
| | - Emre Gür
- Department of Nanoscience and Nanotechnology, Graduate School of Natural and Applied Sciences, Ataturk University, 25240 Erzurum, Turkey
- Department of Physics, Faculty of Science, Atatürk University, 25240, Erzurum, Turkey
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19
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Baker EAD, Pitfield J, Price CJ, Hepplestone SP. Computational analysis of the enhancement of photoelectrolysis using transition metal dichalcogenide heterostructures. J Phys Condens Matter 2022; 34:375001. [PMID: 35767988 DOI: 10.1088/1361-648x/ac7d2c] [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] [Received: 03/18/2022] [Accepted: 06/29/2022] [Indexed: 06/15/2023]
Abstract
Finding a material with all the desired properties for a photocatalytic water splitter is a challenge yet to be overcome, requiring both a surface with ideal energetics for all steps in the hydrogen and oxygen evolution reactions (HER and OER) and a bulk band gap large enough to mediate said steps. We have instead examined separating these challenges by investigating the energetic properties of two-dimensional transition metal dichalcogenides (TMDCs) that could be used as a surface coating to a material with a large enough bulk band gap. First we investigated the energetics of monolayer MoS2and PdSe2using density functional theory and then investigated how these energetics changed when they were combined into a heterostructure. Our results show that the surface properties were practically (<0.2 eV) unchanged when combined and the MoS2layer aligns well with the OER and HER. This work highlights the potential of TMDC monolayers as surface coatings for bulk materials that have sufficient band gaps for photocatalytic applications.
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Affiliation(s)
- Edward A D Baker
- Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL, United Kingdom
| | - Joe Pitfield
- Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL, United Kingdom
| | - Conor J Price
- Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL, United Kingdom
| | - Steven P Hepplestone
- Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL, United Kingdom
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20
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Rahaman M, Zahn DRT. Plasmon-enhanced Raman spectroscopy of two-dimensional semiconductors. J Phys Condens Matter 2022; 34:333001. [PMID: 35671747 DOI: 10.1088/1361-648x/ac7689] [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] [Received: 01/21/2022] [Accepted: 06/07/2022] [Indexed: 06/15/2023]
Abstract
Two-dimensional (2D) semiconductors have grown fast into an extraordinary research field due to their unique physical properties compared to other semiconducting materials. The class of materials proved extremely fertile for both fundamental studies and a wide range of applications from electronics/spintronics/optoelectronics to photocatalysis and CO2reduction. 2D materials are highly confined in the out-of-plane direction and often possess very good environmental stability. Therefore, they have also become a popular material system for the manipulation of optoelectronic properties via numerous external parameters. Being a versatile characterization technique, Raman spectroscopy is used extensively to study and characterize various physical properties of 2D materials. However, weak signals and low spatial resolution hinder its application in more advanced systems where decoding local information plays an important role in advancing our understanding of these materials for nanotechnology applications. In this regard, plasmon-enhanced Raman spectroscopy has been introduced in recent time to investigate local heterogeneous information of 2D semiconductors. In this review, we summarize the recent progress of plasmon-enhanced Raman spectroscopy of 2D semiconductors. We discuss the current state-of-art and provide future perspectives on this specific branch of Raman spectroscopy applied to 2D semiconductors.
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Affiliation(s)
- Mahfujur Rahaman
- Semiconductor Physics, Chemnitz University of Technology, 09107 Chemnitz, Germany
- Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, 19104 Pennsilvania, United States of America
| | - Dietrich R T Zahn
- Semiconductor Physics, Chemnitz University of Technology, 09107 Chemnitz, Germany
- Center for Materials, Architectures and Integration of Nanomembranes (MAIN), 09126 Chemnitz, Germany
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21
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Malik M, Iqbal MA, Choi JR, Pham PV. 2D Materials for Efficient Photodetection: Overview, Mechanisms, Performance and UV-IR Range Applications. Front Chem 2022; 10:905404. [PMID: 35668828 PMCID: PMC9165695 DOI: 10.3389/fchem.2022.905404] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2022] [Accepted: 04/15/2022] [Indexed: 11/25/2022] Open
Abstract
Two-dimensional (2D) materials have been widely used in photodetectors owing to their diverse advantages in device fabrication and manipulation, such as integration flexibility, availability of optical operation through an ultrabroad wavelength band, fulfilling of photonic demands at low cost, and applicability in photodetection with high-performance. Recently, transition metal dichalcogenides (TMDCs), black phosphorus (BP), III-V materials, heterostructure materials, and graphene have emerged at the forefront as intriguing basics for optoelectronic applications in the field of photodetection. The versatility of photonic systems composed of these materials enables their wide range of applications, including facilitation of chemical reactions, speeding-up of responses, and ultrasensitive light detection in the ultraviolet (UV), visible, mid-infrared (MIR), and far-infrared (FIR) ranges. This review provides an overview, evaluation, recent advancements as well as a description of the innovations of the past few years for state-of-the-art photodetectors based on two-dimensional materials in the wavelength range from UV to IR, and on the combinations of different two-dimensional crystals with other nanomaterials that are appealing for a variety of photonic applications. The device setup, materials synthesis, operating methods, and performance metrics for currently utilized photodetectors, along with device performance enhancement factors, are summarized.
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Affiliation(s)
- Maria Malik
- Centre of Excellence in Solid State Physics, University of the Punjab, Lahore, Pakistan
| | - Muhammad Aamir Iqbal
- School of Materials Science and Engineering, Zhejiang University, Hangzhou, China
| | | | - Phuong V Pham
- Hangzhou Global Scientific and Technological Innovation Center, School of Micro-Nano Electronics, Zhejiang University, Hangzhou, China
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22
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Ren MQ, Han S, Fan JQ, Wang L, Wang P, Ren W, Peng K, Li S, Wang SZ, Zheng FW, Zhang P, Li F, Ma X, Xue QK, Song CL. Semiconductor-Metal Phase Transition and Emergent Charge Density Waves in 1 T-ZrX 2 (X = Se, Te) at the Two-Dimensional Limit. Nano Lett 2022; 22:476-484. [PMID: 34978815 DOI: 10.1021/acs.nanolett.1c04372] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
A charge density wave (CDW) is a collective quantum phenomenon in metals and features a wavelike modulation of the conduction electron density. A microscopic understanding and experimental control of this many-body electronic state in atomically thin materials remain hot topics in materials physics. By means of material engineering, we realized a dimensionality and Zr intercalation induced semiconductor-metal phase transition in 1T-ZrX2 (X = Se, Te) ultrathin films, accompanied by a commensurate 2 × 2 CDW order. Furthermore, we observed a CDW energy gap of up to 22 meV around the Fermi level. Fourier-transformed scanning tunneling microscopy and angle-resolved photoemission spectroscopy reveal that 1T-ZrX2 films exhibit the simplest Fermi surface among the known CDW materials in TMDCs, consisting only of a Zr 4d derived elliptical electron conduction band at the corners of the Brillouin zone.
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Affiliation(s)
- Ming-Qiang Ren
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China
| | - Sha Han
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China
| | - Jia-Qi Fan
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China
| | - Li Wang
- Vacuum Interconnected Nanotech Workstation, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, People's Republic of China
| | - Pengdong Wang
- Vacuum Interconnected Nanotech Workstation, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, People's Republic of China
| | - Wei Ren
- Vacuum Interconnected Nanotech Workstation, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, People's Republic of China
| | - Kun Peng
- Vacuum Interconnected Nanotech Workstation, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, People's Republic of China
| | - Shujing Li
- College of Mathematics and Physics, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China
| | - Shu-Ze Wang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China
| | - Fa-Wei Zheng
- Institute of Applied Physics and Computational Mathematics, Beijing 100088, People's Republic of China
| | - Ping Zhang
- College of Mathematics and Physics, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China
| | - Fangsen Li
- Vacuum Interconnected Nanotech Workstation, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, People's Republic of China
| | - Xucun Ma
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China
- Frontier Science Center for Quantum Information, Beijing 100084, People's Republic of China
| | - Qi-Kun Xue
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China
- Frontier Science Center for Quantum Information, Beijing 100084, People's Republic of China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, People's Republic of China
| | - Can-Li Song
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China
- Frontier Science Center for Quantum Information, Beijing 100084, People's Republic of China
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23
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Khusyainov D, Guskov A, Ovcharenko S, Tiercelin N, Preobrazhensky V, Buryakov A, Sigov A, Mishina E. Increasing the Efficiency of a Spintronic THz Emitter Based on WSe 2/FeCo. Materials (Basel) 2021; 14:6479. [PMID: 34772004 DOI: 10.3390/ma14216479] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Revised: 10/21/2021] [Accepted: 10/22/2021] [Indexed: 11/17/2022]
Abstract
We report an increase in terahertz (THz) radiation efficiency due to FeCo/WSe2 structures in the reflection geometry. This can be attributed to an absorption increase in the alloy FeCo layer at the input FeCo/WSe2 interface due to constructive interference, as well as to the backward transport of hot carriers from FeCo to WSe2. In contrast to the transmission geometry, the THz generation efficiency in the reflection is much less dependent on the magnetic layer thickness. Our results suggest a cheap and efficient way to improve the characteristics of THz spintronic emitters with the conservation of a full set of their important properties.
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24
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Ramezani M, Sampaio IC, Watanabe K, Taniguchi T, Schönenberger C, Baumgartner A. Superconducting Contacts to a Monolayer Semiconductor. Nano Lett 2021; 21:5614-5619. [PMID: 34161104 PMCID: PMC8283752 DOI: 10.1021/acs.nanolett.1c00615] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 06/02/2021] [Indexed: 05/28/2023]
Abstract
We demonstrate superconducting vertical interconnect access (VIA) contacts to a monolayer of molybdenum disulfide (MoS2), a layered semiconductor with highly relevant electronic and optical properties. As a contact material we use MoRe, a superconductor with a high critical magnetic field and high critical temperature. The electron transport is mostly dominated by a single superconductor/normal conductor junction with a clear superconductor gap. In addition, we find MoS2 regions that are strongly coupled to the superconductor, resulting in resonant Andreev tunneling and junction-dependent gap characteristics, suggesting a superconducting proximity effect. Magnetoresistance measurements show that the bandstructure and the high intrinsic carrier mobility remain intact in the bulk of the MoS2. This type of VIA contact is applicable to a large variety of layered materials and superconducting contacts, opening up a path to monolayer semiconductors as a platform for superconducting hybrid devices.
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Affiliation(s)
- Mehdi Ramezani
- Department
of Physics, University of Basel, CH-4056, Basel, Switzerland
- Swiss
Nanoscience Institute, University of Basel, CH-4056, Basel, Switzerland
| | | | - Kenji Watanabe
- Research
Center for Functional Materials, National
Institute for Material Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
| | - Takashi Taniguchi
- International
Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Christian Schönenberger
- Department
of Physics, University of Basel, CH-4056, Basel, Switzerland
- Swiss
Nanoscience Institute, University of Basel, CH-4056, Basel, Switzerland
| | - Andreas Baumgartner
- Department
of Physics, University of Basel, CH-4056, Basel, Switzerland
- Swiss
Nanoscience Institute, University of Basel, CH-4056, Basel, Switzerland
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25
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Bretscher H, Li Z, Xiao J, Qiu DY, Refaely-Abramson S, Alexander-Webber JA, Tanoh A, Fan Y, Delport G, Williams CA, Stranks SD, Hofmann S, Neaton JB, Louie SG, Rao A. Rational Passivation of Sulfur Vacancy Defects in Two-Dimensional Transition Metal Dichalcogenides. ACS Nano 2021; 15:8780-8789. [PMID: 33983711 PMCID: PMC8158852 DOI: 10.1021/acsnano.1c01220] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Accepted: 05/07/2021] [Indexed: 06/01/2023]
Abstract
Structural defects vary the optoelectronic properties of monolayer transition metal dichalcogenides, leading to concerted efforts to control defect type and density via materials growth or postgrowth passivation. Here, we explore a simple chemical treatment that allows on-off switching of low-lying, defect-localized exciton states, leading to tunable emission properties. Using steady-state and ultrafast optical spectroscopy, supported by ab initio calculations, we show that passivation of sulfur vacancy defects, which act as exciton traps in monolayer MoS2 and WS2, allows for controllable and improved mobilities and an increase in photoluminescence up to 275-fold, more than twice the value achieved by other chemical treatments. Our findings suggest a route for simple and rational defect engineering strategies for tunable and switchable electronic and excitonic properties through passivation.
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Affiliation(s)
| | - Zhaojun Li
- University
of Cambridge, Cambridge, CB2 1TN, U.K.
- Uppsala
University, Uppsala, 751 20, Sweden
| | - James Xiao
- University
of Cambridge, Cambridge, CB2 1TN, U.K.
| | - Diana Yuan Qiu
- Yale
University, New Haven, Connecticut 06520, United States
| | | | | | - Arelo Tanoh
- University
of Cambridge, Cambridge, CB2 1TN, U.K.
| | - Ye Fan
- University
of Cambridge, Cambridge, CB2 1TN, U.K.
| | | | | | | | | | - Jeffrey B. Neaton
- University
of California Berkeley, Berkeley, California 94720, United States
- Lawrence
Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Steven G. Louie
- University
of California Berkeley, Berkeley, California 94720, United States
- Lawrence
Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Akshay Rao
- University
of Cambridge, Cambridge, CB2 1TN, U.K.
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26
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So JP, Jeong KY, Lee JM, Kim KH, Lee SJ, Huh W, Kim HR, Choi JH, Kim JM, Kim YS, Lee CH, Nam S, Park HG. Polarization Control of Deterministic Single-Photon Emitters in Monolayer WSe 2. Nano Lett 2021; 21:1546-1554. [PMID: 33502866 DOI: 10.1021/acs.nanolett.1c00078] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Single-photon emitters, the basic building blocks of quantum communication and information, have been developed using atomically thin transition metal dichalcogenides (TMDCs). Although the bandgap of TMDCs was spatially engineered in artificially created defects for single-photon emitters, it remains a challenge to precisely align the emitter's dipole moment to optical cavities for the Purcell enhancement. Here, we demonstrate position- and polarization-controlled single-photon emitters in monolayer WSe2. A tensile strain of ∼0.2% was applied to monolayer WSe2 by placing it onto a dielectric rod structure with a nanosized gap. Excitons were localized in the nanogap sites, resulting in the generation of linearly polarized single-photon emission with a g(2) of ∼0.1 at 4 K. Additionally, we measured the abrupt change in polarization of single photons with respect to the nanogap size. Our robust spatial and polarization control of emission provides an efficient way to demonstrate deterministic and scalable single-photon sources by integrating with nanocavities.
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Affiliation(s)
- Jae-Pil So
- Department of Physics, Korea University, Seoul 02841, Republic of Korea
| | - Kwang-Yong Jeong
- Department of Physics, Korea University, Seoul 02841, Republic of Korea
| | - Jung Min Lee
- Department of Physics, Korea University, Seoul 02841, Republic of Korea
| | - Kyoung-Ho Kim
- Department of Physics, Chungbuk National University, Cheongju 28644, Republic of Korea
| | - Soon-Jae Lee
- Department of Physics, Korea University, Seoul 02841, Republic of Korea
| | - Woong Huh
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Republic of Korea
| | - Ha-Reem Kim
- Department of Physics, Korea University, Seoul 02841, Republic of Korea
| | - Jae-Hyuck Choi
- Department of Physics, Korea University, Seoul 02841, Republic of Korea
| | - Jin Myung Kim
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Champaign, Illinois 61801, United States
| | - Yoon Seok Kim
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Republic of Korea
| | - Chul-Ho Lee
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Republic of Korea
- Department of Integrative Energy Engineering, Korea University, Seoul 02841, Republic of Korea
| | - SungWoo Nam
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Champaign, Illinois 61801, United States
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Champaign, Illinois 61801, United States
| | - Hong-Gyu Park
- Department of Physics, Korea University, Seoul 02841, Republic of Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Republic of Korea
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science, Seoul 02841, Republic of Korea
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27
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Lunardon M, Ran J, Mosconi D, Marega C, Wang Z, Xia H, Agnoli S, Granozzi G. Hybrid Transition Metal Dichalcogenide/Graphene Microspheres for Hydrogen Evolution Reaction. Nanomaterials (Basel) 2020; 10:nano10122376. [PMID: 33260654 PMCID: PMC7759811 DOI: 10.3390/nano10122376] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 11/24/2020] [Accepted: 11/27/2020] [Indexed: 11/17/2022]
Abstract
A peculiar 3D graphene-based architecture, i.e., partial reduced-Graphene Oxide Aerogel Microspheres (prGOAM), having a dandelion-like morphology with divergent microchannels to implement innovative electrocatalysts for the hydrogen evolution reaction (HER) is investigated in this paper. prGOAM was used as a scaffold to incorporate exfoliated transition metals dichalcogenide (TMDC) nanosheets, and the final hybrid materials have been tested for HER and photo-enhanced HER. The aim was to create a hybrid material where electronic contacts among the two pristine materials are established in a 3D architecture, which might increase the final HER activity while maintaining accessible the TMDC catalytic sites. The adopted bottom-up approach, based on combining electrospraying with freeze-casting techniques, successfully provides a route to prepare TMDC/prGOAM hybrid systems where the dandelion-like morphology is retained. Interestingly, the microspherical morphology is also maintained in the tested electrode and after the electrocatalytic experiments, as demonstrated by scanning electron microscopy images. Comparing the HER activity of the TMDC/prGOAM hybrid systems with that of TMDC/partially reduced-Graphene Oxide (prGO) and TMDC/Vulcan was evidenced in the role of the divergent microchannels present in the 3D architecture. HER photoelectron catalytic (PEC) tests have been carried out and demonstrated an interesting increase in HER performance.
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Affiliation(s)
- Marco Lunardon
- Department of Chemical Sciences, University of Padova, Via F. Marzolo 1, 35131 Padova, Italy; (M.L.); (J.R.); (D.M.); (C.M.); (S.A.)
| | - JiaJia Ran
- Department of Chemical Sciences, University of Padova, Via F. Marzolo 1, 35131 Padova, Italy; (M.L.); (J.R.); (D.M.); (C.M.); (S.A.)
| | - Dario Mosconi
- Department of Chemical Sciences, University of Padova, Via F. Marzolo 1, 35131 Padova, Italy; (M.L.); (J.R.); (D.M.); (C.M.); (S.A.)
| | - Carla Marega
- Department of Chemical Sciences, University of Padova, Via F. Marzolo 1, 35131 Padova, Italy; (M.L.); (J.R.); (D.M.); (C.M.); (S.A.)
| | - Zhanhua Wang
- State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute, Sichuan University, Chengdu 610065, China; (Z.W.); (H.X.)
| | - Hesheng Xia
- State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute, Sichuan University, Chengdu 610065, China; (Z.W.); (H.X.)
| | - Stefano Agnoli
- Department of Chemical Sciences, University of Padova, Via F. Marzolo 1, 35131 Padova, Italy; (M.L.); (J.R.); (D.M.); (C.M.); (S.A.)
| | - Gaetano Granozzi
- Department of Chemical Sciences, University of Padova, Via F. Marzolo 1, 35131 Padova, Italy; (M.L.); (J.R.); (D.M.); (C.M.); (S.A.)
- Correspondence: ; Tel.: +39-3347151920
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28
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Girardi L, Blanco M, Agnoli S, Rizzi GA, Granozzi G. A DVD-MoS 2/Ag 2S/Ag Nanocomposite Thiol-Conjugated with Porphyrins for an Enhanced Light-Mediated Hydrogen Evolution Reaction. Nanomaterials (Basel) 2020; 10:nano10071266. [PMID: 32610453 PMCID: PMC7408523 DOI: 10.3390/nano10071266] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 06/18/2020] [Accepted: 06/25/2020] [Indexed: 11/16/2022]
Abstract
We have recently demonstrated in a previous work an appreciable photoelectrocatalytic (PEC) behavior towards hydrogen evolution reaction (HER) of a MoS2/Ag2S/Ag nanocomposite electrochemically deposited on a commercial writable Digital Versatile Disc (DVD), consisting therefore on an interesting strategy to convert a common waster product in an added-value material. Herein, we present the conjugation of this MoS2/Ag2S/Ag-DVD nanocomposite with thiol-terminated tetraphenylporphyrins, taking advantage of the grafting of thiol groups through covalent S-S bridges, for integrating the well-known porphyrins photoactivity into the nanocomposite. Moreover, we employ two thiol-terminated porphyrins with different hydrophilicity, demonstrating that they either suppress or improve the PEC-HER performance of the overall hybrid, as a function of the molecule polarity, sustaining the concept of a local proton relay. Actually, the active polar porphyrin-MoS2/Ag2S/Ag-DVD hybrid material presented, when illuminated, a better HER performance, compared to the pristine nanocomposite, since the porphyrin may inject photoelectrons in the conduction band of the semiconductors at the formed heterojunction, presenting also a stable operational behavior during overnight chopped light chronoamperometric measurement, thanks to the robust bond created.
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Affiliation(s)
- Leonardo Girardi
- Department of Chemical Sciences and INSTM Unit, University of Padova, Via F. Marzolo 1, 35131 Padova, Italy; (L.G.); (S.A.); (G.G.)
| | - Matías Blanco
- Department of Chemical Sciences and INSTM Unit, University of Padova, Via F. Marzolo 1, 35131 Padova, Italy; (L.G.); (S.A.); (G.G.)
- Department of Organic Chemistry, Universidad Autónoma de Madrid, Ciudad Universitaria de Cantoblanco, Calle Francisco Tomás y Valiente, 7, 28049 Madrid, Spain
- Correspondence: (M.B.); (G.A.R.); Tel.: +34-914975022 (M.B.); +39-0498275722 (G.A.R.)
| | - Stefano Agnoli
- Department of Chemical Sciences and INSTM Unit, University of Padova, Via F. Marzolo 1, 35131 Padova, Italy; (L.G.); (S.A.); (G.G.)
| | - Gian Andrea Rizzi
- Department of Chemical Sciences and INSTM Unit, University of Padova, Via F. Marzolo 1, 35131 Padova, Italy; (L.G.); (S.A.); (G.G.)
- Correspondence: (M.B.); (G.A.R.); Tel.: +34-914975022 (M.B.); +39-0498275722 (G.A.R.)
| | - Gaetano Granozzi
- Department of Chemical Sciences and INSTM Unit, University of Padova, Via F. Marzolo 1, 35131 Padova, Italy; (L.G.); (S.A.); (G.G.)
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29
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Raya SS, Ansari AS, Shong B. Molecular Adsorption of NH 3 and NO 2 on Zr and Hf Dichalcogenides (S, Se, Te) Monolayers: A Density Functional Theory Study. Nanomaterials (Basel) 2020; 10:E1215. [PMID: 32580390 DOI: 10.3390/nano10061215] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 06/18/2020] [Accepted: 06/20/2020] [Indexed: 11/17/2022]
Abstract
Due to their atomic thicknesses and semiconducting properties, two-dimensional transition metal dichalcogenides (TMDCs) are gaining increasing research interest. Among them, Hf- and Zr-based TMDCs demonstrate the unique advantage that their oxides (HfO2 and ZrO2) are excellent dielectric materials. One possible method to precisely tune the material properties of two-dimensional atomically thin nanomaterials is to adsorb molecules on their surfaces as non-bonded dopants. In the present work, the molecular adsorption of NO2 and NH3 on the two-dimensional trigonal prismatic (1H) and octahedral (1T) phases of Hf and Zr dichalcogenides (S, Se, Te) is studied using dispersion-corrected periodic density functional theory (DFT) calculations. The adsorption configuration, energy, and charge-transfer properties during molecular adsorption are investigated. In addition, the effects of the molecular dopants (NH3 and NO2) on the electronic structure of the materials are studied. It was observed that the adsorbed NH3 donates electrons to the conduction band of the Hf (Zr) dichalcogenides, while NO2 receives electrons from the valance band. Furthermore, the NO2 dopant affects than NH3 significantly. The resulting band structure of the molecularly doped Zr and Hf dichalcogenides are modulated by the molecular adsorbates. This study explores, not only the properties of the two-dimensional 1H and 1T phases of Hf and Zr dichalcogenides (S, Se, Te), but also tunes their electronic properties by adsorbing non-bonded dopants.
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30
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Kazanov D, Rakhlin M, Poshakinskiy A, Shubina T. Towards Exciton-Polaritons in an Individual MoS 2 Nanotube. Nanomaterials (Basel) 2020; 10:E373. [PMID: 32093325 PMCID: PMC7075280 DOI: 10.3390/nano10020373] [Citation(s) in RCA: 5] [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] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 02/12/2020] [Accepted: 02/17/2020] [Indexed: 12/03/2022]
Abstract
We measure low-temperature micro-photoluminescence spectra along a MoS 2 nanotube, which exhibit the peaks of the optical whispering gallery modes below the exciton resonance. The energy fluctuation and width of these peaks are determined by the changes of the nanotube wall thickness and propagation of the optical modes along the nanotube axis, respectively. We demonstrate the potential of the high-quality nanotubes for realization of the strong coupling between exciton and optical modes when the Rabi splitting can reach 400 meV. We show how the formation of exciton-polaritons in such structures will be manifested in the micro-photoluminescence spectra and analyze the conditions needed to realize that.
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Affiliation(s)
- Dmitrii Kazanov
- Ioffe Institute, 26 Politekhnicheskaya, 194021 St Petersburg, Russia; (M.R.); (A.P.); (T.S.)
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31
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Yankovich AB, Munkhbat B, Baranov DG, Cuadra J, Olsén E, Lourenço-Martins H, Tizei LHG, Kociak M, Olsson E, Shegai T. Visualizing Spatial Variations of Plasmon-Exciton Polaritons at the Nanoscale Using Electron Microscopy. Nano Lett 2019; 19:8171-8181. [PMID: 31639311 DOI: 10.1021/acs.nanolett.9b03534] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Polaritons are compositional light-matter quasiparticles that have enabled remarkable breakthroughs in quantum and nonlinear optics, as well as in material science. Recently, plasmon-exciton polaritons (plexcitons) have been realized in hybrid material systems composed of transition metal dichalcogenide (TMDC) materials and metal nanoparticles, expanding polaritonic concepts to room temperature and nanoscale systems that also benefit from the exotic properties of TMDC materials. Despite the enormous progress in understanding TMDC-based plexcitons using optical-based methods, experimental evidence of plexcitons formation has remained indirect and mapping their nanometer-scale characteristics has remained an open challenge. Here, we demonstrate that plexcitons generated by a hybrid system composed of an individual silver nanoparticle and a few-layer WS2 flake can be spectroscopically mapped with nanometer spatial resolution using electron energy loss spectroscopy in a scanning transmission electron microscope. Experimental anticrossing measurements using the absorption-dominated extinction signal provide the ultimate evidence for plexciton hybridization in the strong coupling regime. Spatially resolved EELS maps reveal the existence of unexpected nanoscale variations in the deep-subwavelength nature of plexcitons generated by this system. These findings pioneer new possibilities for in-depth studies of the local atomic structure dependence of polariton-related phenomena in TMDC hybrid material systems with nanometer spatial resolution.
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Affiliation(s)
- Andrew B Yankovich
- Department of Physics , Chalmers University of Technology , 412 96 , Gothenburg , Sweden
| | - Battulga Munkhbat
- Department of Physics , Chalmers University of Technology , 412 96 , Gothenburg , Sweden
| | - Denis G Baranov
- Department of Physics , Chalmers University of Technology , 412 96 , Gothenburg , Sweden
| | - Jorge Cuadra
- Department of Physics , Chalmers University of Technology , 412 96 , Gothenburg , Sweden
| | - Erik Olsén
- Department of Physics , Chalmers University of Technology , 412 96 , Gothenburg , Sweden
| | - Hugo Lourenço-Martins
- Laboratoire de Physique des Solides , Paris-Sud Université, CNRS UMR 8502 , Orsay , France
| | - Luiz H G Tizei
- Laboratoire de Physique des Solides , Paris-Sud Université, CNRS UMR 8502 , Orsay , France
| | - Mathieu Kociak
- Laboratoire de Physique des Solides , Paris-Sud Université, CNRS UMR 8502 , Orsay , France
| | - Eva Olsson
- Department of Physics , Chalmers University of Technology , 412 96 , Gothenburg , Sweden
| | - Timur Shegai
- Department of Physics , Chalmers University of Technology , 412 96 , Gothenburg , Sweden
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32
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Yu Y, Bataller AW, Younts R, Yu Y, Li G, Puretzky AA, Geohegan DB, Gundogdu K, Cao L. Room-Temperature Electron-Hole Liquid in Monolayer MoS 2. ACS Nano 2019; 13:10351-10358. [PMID: 31483608 DOI: 10.1021/acsnano.9b04124] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [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
Excitons in semiconductors are usually noninteracting and behave like an ideal gas, but may condense to a strongly correlated liquid-like state, i.e., electron-hole liquid (EHL), at high density and appropriate temperature. An EHL is a macroscopic quantum state with exotic properties and represents the ultimate attainable charge excitation density in steady states. It bears great promise for a variety of fields such as ultra-high-power photonics and quantum science and technology. However, the condensation of gas-like excitons to an EHL has often been restricted to cryogenic temperatures, which significantly limits the prospect of EHLs for use in practical applications. Herein we demonstrate the formation of an EHL at room temperature in monolayer MoS2 by taking advantage of the monolayer's extraordinarily strong exciton binding energy. This work demonstrates the potential for the liquid-like state of charge excitations to be a useful platform for the studies of macroscopic quantum phenomena and the development of optoelectronic devices.
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Affiliation(s)
- Yiling Yu
- Department of Materials Science and Engineering , North Carolina State University , Raleigh , North Carolina 27695 , United States
| | - Alexander W Bataller
- Department of Physics , North Carolina State University , Raleigh , North Carolina 27695 , United States
| | - Robert Younts
- Department of Physics , North Carolina State University , Raleigh , North Carolina 27695 , United States
| | - Yifei Yu
- Department of Materials Science and Engineering , North Carolina State University , Raleigh , North Carolina 27695 , United States
| | - Guoqing Li
- Department of Materials Science and Engineering , North Carolina State University , Raleigh , North Carolina 27695 , United States
| | - Alexander A Puretzky
- Center for Nanophase Materials Sciences , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
| | - David B Geohegan
- Center for Nanophase Materials Sciences , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
| | - Kenan Gundogdu
- Department of Physics , North Carolina State University , Raleigh , North Carolina 27695 , United States
| | - Linyou Cao
- Department of Materials Science and Engineering , North Carolina State University , Raleigh , North Carolina 27695 , United States
- Department of Physics , North Carolina State University , Raleigh , North Carolina 27695 , United States
- Department of Electrical and Computer Engineering , North Carolina State University , Raleigh , North Carolina 27695 , United States
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33
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Busschaert S, Flöry N, Papadopoulos S, Parzefall M, Heeg S, Novotny L. Beam Steering with a Nonlinear Optical Phased Array Antenna. Nano Lett 2019; 19:6097-6103. [PMID: 31424948 DOI: 10.1021/acs.nanolett.9b02029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [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
Transition metal dichalcogenides (TMDCs) exhibit high second harmonic (SH) generation in the visible due to their noncentrosymmetric crystal structure in odd-layered form and direct bandgap transition when thinned down to a monolayer. In order to emit the SH radiation into a desired direction, one requires a means to control the phase of the in-plane nonlinear polarization. Here, we couple the SH response of a monolayer MoS2 to an optical phased array antenna and demonstrate controllable steering of the nonlinear emission. By exploiting the intrinsic SH generation by the phased array antenna we achieve uniform emission efficiency into a broad angular range. Our work has relevance for novel optoelectronic applications, such as programmable optical interconnects and on-chip LIDAR.
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Affiliation(s)
| | - Nikolaus Flöry
- Photonics Laboratory , ETH Zürich , 8093 Zürich , Switzerland
| | | | | | - Sebastian Heeg
- Photonics Laboratory , ETH Zürich , 8093 Zürich , Switzerland
| | - Lukas Novotny
- Photonics Laboratory , ETH Zürich , 8093 Zürich , Switzerland
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34
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Abstract
Layered materials are very attractive for studies of light-matter interactions at the nanoscale. In particular, isolated quantum systems such as color centers and quantum dots embedded in these materials are gaining interest due to their potential use in a variety of quantum technologies and nanophotonics. Here, we review the field of nonclassical light emission from van der Waals crystals and atomically thin two-dimensional materials. We focus on transition metal dichalcogenides and hexagonal boron nitride and discuss the fabrication and properties of quantum emitters in these systems and proof-of-concept experiments that provide a foundation for their integration in on-chip nanophotonic circuits. These experiments include tuning of the emission wavelength, electrical excitation, and coupling of the emitters to waveguides, dielectric cavities, and plasmonic resonators. Finally, we discuss current challenges in the field and provide an outlook to further stimulate scientific discussion.
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Affiliation(s)
- Milos Toth
- Institute of Biomedical Materials and Devices, University of Technology Sydney, Ultimo, New South Wales 2007, Australia; ,
| | - Igor Aharonovich
- Institute of Biomedical Materials and Devices, University of Technology Sydney, Ultimo, New South Wales 2007, Australia; ,
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35
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Bisht A, Cuadra J, Wersäll M, Canales A, Antosiewicz TJ, Shegai T. Collective Strong Light-Matter Coupling in Hierarchical Microcavity-Plasmon-Exciton Systems. Nano Lett 2019; 19:189-196. [PMID: 30500202 DOI: 10.1021/acs.nanolett.8b03639] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Polaritons are compositional light-matter quasiparticles that arise as a result of strong coupling between the vacuum field of a resonant optical cavity and electronic excitations in quantum emitters. Reaching such a regime is often hard, as it requires materials possessing high oscillator strengths to interact with the relevant optical mode. Two-dimensional transition metal dichalcogenides (TMDCs) have recently emerged as promising candidates for realization of strong coupling regime at room temperature. However, these materials typically provide coupling strengths in the range of 10-40 meV, which may be insufficient for reaching strong coupling with low quality factor resonators. Here, we demonstrate a universal scheme that allows a straightforward realization of strong coupling with 2D materials and beyond. By intermixing plasmonic excitations in nanoparticle arrays with excitons in a WS2 monolayer inside a resonant metallic microcavity, we fabricate a hierarchical system with the collective microcavity-plasmon-exciton Rabi splitting exceeding ∼500 meV at room temperature. Photoluminescence measurements of the coupled systems show dominant emission from the lower polariton branch, indicating the participation of excitons in the coupling process. Strong coupling has been recently suggested to affect numerous optical- and material-related properties including chemical reactivity, exciton transport, and optical nonlinearities. With the universal scheme presented here, strong coupling across a wide spectral range is within easy reach and therefore exploration of these exciting phenomena can be further pursued in a much broader class of materials.
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Affiliation(s)
- Ankit Bisht
- Department of Physics , Chalmers University of Technology , 412 96 , Göteborg , Sweden
| | - Jorge Cuadra
- Department of Physics , Chalmers University of Technology , 412 96 , Göteborg , Sweden
| | - Martin Wersäll
- Department of Physics , Chalmers University of Technology , 412 96 , Göteborg , Sweden
| | - Adriana Canales
- Department of Physics , Chalmers University of Technology , 412 96 , Göteborg , Sweden
| | - Tomasz J Antosiewicz
- Department of Physics , Chalmers University of Technology , 412 96 , Göteborg , Sweden
- Faculty of Physics , University of Warsaw , Pasteura 5 , 02-093 Warsaw , Poland
| | - Timur Shegai
- Department of Physics , Chalmers University of Technology , 412 96 , Göteborg , Sweden
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36
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Hussain S, Akbar K, Vikraman D, Afzal RA, Song W, An KS, Farooq A, Park JY, Chun SH, Jung J. WS (1-x)Se x Nanoparticles Decorated Three-Dimensional Graphene on Nickel Foam: A Robust and Highly Efficient Electrocatalyst for the Hydrogen Evolution Reaction. Nanomaterials (Basel) 2018; 8:E929. [PMID: 30413067 PMCID: PMC6266445 DOI: 10.3390/nano8110929] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Revised: 10/30/2018] [Accepted: 11/04/2018] [Indexed: 11/19/2022]
Abstract
To find an effective alternative to scarce, high-cost noble platinum (Pt) electrocatalyst for hydrogen evolution reaction (HER), researchers are pursuing inexpensive and highly efficient materials as an electrocatalyst for large scale practical application. Layered transition metal dichalcogenides (TMDCs) are promising candidates for durable HER catalysts due to their cost-effective, highly active edges and Earth-abundant elements to replace Pt electrocatalysts. Herein, we design an active, stable earth-abundant TMDCs based catalyst, WS(1-x)Sex nanoparticles-decorated onto a 3D porous graphene/Ni foam. The WS(1-x)Sex/graphene/NF catalyst exhibits fast hydrogen evolution kinetics with a moderate overpotential of ~-93 mV to drive a current density of 10 mA cm-2, a small Tafel slope of ~51 mV dec-1, and a long cycling lifespan more than 20 h in 0.5 M sulfuric acid, which is much better than WS₂/NF and WS₂/graphene/NF catalysts. Our outcomes enabled a way to utilize the TMDCs decorated graphene and precious-metal-free electrocatalyst as mechanically robust and electrically conductive catalyst materials.
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Affiliation(s)
- Sajjad Hussain
- Graphene Research Institute, Sejong University, Seoul 05006, Korea.
- Institute of Nano and Advanced Materials Engineering, Sejong University, Seoul 05006, Korea.
| | - Kamran Akbar
- Department of Physics, Sejong University, Seoul 05006, Korea.
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Korea.
| | - Dhanasekaran Vikraman
- Division of Electronics and Electrical Engineering, Dongguk University-Seoul, Seoul 04620, Korea.
| | - Rana Arslan Afzal
- Institute of Nano and Advanced Materials Engineering, Sejong University, Seoul 05006, Korea.
| | - Wooseok Song
- Thin Film Materials Research Center, Korea Research Institute of Chemical Technology, Daejeon 34114, Korea.
| | - Ki-Seok An
- Thin Film Materials Research Center, Korea Research Institute of Chemical Technology, Daejeon 34114, Korea.
| | - Ayesha Farooq
- Department of Physics, COMSATS IIT, Islamabad 45550, Pakistan.
| | - Jun-Young Park
- Institute of Nano and Advanced Materials Engineering, Sejong University, Seoul 05006, Korea.
| | - Seung-Hyun Chun
- Department of Physics, Sejong University, Seoul 05006, Korea.
| | - Jongwan Jung
- Graphene Research Institute, Sejong University, Seoul 05006, Korea.
- Institute of Nano and Advanced Materials Engineering, Sejong University, Seoul 05006, Korea.
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37
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Stührenberg M, Munkhbat B, Baranov DG, Cuadra J, Yankovich AB, Antosiewicz TJ, Olsson E, Shegai T. Strong Light-Matter Coupling between Plasmons in Individual Gold Bi-pyramids and Excitons in Mono- and Multilayer WSe 2. Nano Lett 2018; 18:5938-5945. [PMID: 30081635 DOI: 10.1021/acs.nanolett.8b02652] [Citation(s) in RCA: 18] [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: 06/08/2023]
Abstract
Monolayer transition-metal dichalcogenides (TMDCs) have attracted a lot of research attention recently, motivated by their remarkable optical properties and potential for strong light-matter interactions. Realization of strong plasmon-exciton coupling is especially desirable in this context because it holds promise for the enabling of room-temperature quantum and nonlinear optical applications. These efforts naturally require investigations at a single-nanoantenna level, which, in turn, should possess a compact optical mode interacting with a small amount of excitonic material. However, standard plasmonic nanoantenna designs such as nanoparticle dimers or particle-on-film suffer from misalignment of the local electric field in the gap with the in-plane transition dipole moment of monolayer TMDCs. Here, we circumvent this problem by utilizing gold bi-pyramids (BPs) as very efficient plasmonic nanoantennas. We demonstrate strong coupling between individual BPs and tungsten diselenide (WSe2) monolayers at room temperature. We further study the coupling between multilayers of WSe2 and BPs to elucidate the effect of the number of layers on the coupling strength. Importantly, BPs adopt a reduced-symmetry configuration when deposited on WSe2, such that only one sharp antenna tip efficiently interacts with excitons. Despite the small interaction area, we manage to achieve strong coupling, with Rabi splitting exceeding ∼100 meV. Our results suggest a feasible way toward realizing plasmon-exciton polaritons involving nanoscopic areas of TMDCs, thus pointing toward quantum and nonlinear optics applications at ambient conditions.
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Affiliation(s)
- Michael Stührenberg
- Department of Physics , Chalmers University of Technology , 412 96 Göteborg , Sweden
| | - Battulga Munkhbat
- Department of Physics , Chalmers University of Technology , 412 96 Göteborg , Sweden
| | - Denis G Baranov
- Department of Physics , Chalmers University of Technology , 412 96 Göteborg , Sweden
| | - Jorge Cuadra
- Department of Physics , Chalmers University of Technology , 412 96 Göteborg , Sweden
| | - Andrew B Yankovich
- Department of Physics , Chalmers University of Technology , 412 96 Göteborg , Sweden
| | - Tomasz J Antosiewicz
- Department of Physics , Chalmers University of Technology , 412 96 Göteborg , Sweden
- Faculty of Physics , University of Warsaw , Pasteura 5 , 02-093 Warsaw , Poland
| | - Eva Olsson
- Department of Physics , Chalmers University of Technology , 412 96 Göteborg , Sweden
| | - Timur Shegai
- Department of Physics , Chalmers University of Technology , 412 96 Göteborg , Sweden
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38
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Bassman L, Krishnamoorthy A, Kumazoe H, Misawa M, Shimojo F, Kalia RK, Nakano A, Vashishta P. Electronic Origin of Optically-Induced Sub-Picosecond Lattice Dynamics in MoSe 2 Monolayer. Nano Lett 2018; 18:4653-4658. [PMID: 29990437 DOI: 10.1021/acs.nanolett.8b00474] [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
Atomically thin layers of transition metal dichalcogenide (TMDC) semiconductors exhibit outstanding electronic and optical properties, with numerous applications such as valleytronics. While unusually rapid and efficient transfer of photoexcitation energy to atomic vibrations was found in recent experiments, its electronic origin remains unknown. Here, we study the lattice dynamics induced by electronic excitation in a model TMDC monolayer, MoSe2, using nonadiabatic quantum molecular dynamics simulations. Simulation results show sub-picosecond disordering of the lattice upon photoexcitation, as measured by the Debye-Waller factor, as well as increasing disorder for higher densities of photogenerated electron-hole pairs. Detailed analysis shows that the rapid, photoinduced lattice dynamics are due to phonon-mode softening, which in turn arises from electronic Fermi surface nesting. Such mechanistic understanding can help guide optical control of material properties for functionalizing TMDC layers, enabling emerging applications such as phase change memories and neuromorphic computing.
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Affiliation(s)
| | | | - Hiroyuki Kumazoe
- Department of Physics , Kumamoto University , Kumamoto 860-8555 , Japan
| | - Masaaki Misawa
- Department of Physics , Kumamoto University , Kumamoto 860-8555 , Japan
| | - Fuyuki Shimojo
- Department of Physics , Kumamoto University , Kumamoto 860-8555 , Japan
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39
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Cuadra J, Baranov DG, Wersäll M, Verre R, Antosiewicz TJ, Shegai T. Observation of Tunable Charged Exciton Polaritons in Hybrid Monolayer WS 2-Plasmonic Nanoantenna System. Nano Lett 2018; 18:1777-1785. [PMID: 29369640 DOI: 10.1021/acs.nanolett.7b04965] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [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
Formation of dressed light-matter states in optical structures, manifested as Rabi splitting of the eigen energies of a coupled system, is one of the key effects in quantum optics. In pursuing this regime with semiconductors, light is usually made to interact with excitons, electrically neutral quasiparticles of semiconductors; meanwhile interactions with charged three-particle states, trions, have received little attention. Here, we report on strong interaction between localized surface plasmons in silver nanoprisms and excitons and trions in monolayer tungsten disulfide (WS2). We show that the plasmon-exciton interactions in this system can be efficiently tuned by controlling the charged versus neutral exciton contribution to the coupling process. In particular, we show that a stable trion state emerges and couples efficiently to the plasmon resonance at low temperature by forming three bright intermixed plasmon-exciton-trion polariton states. Our findings open up a possibility to exploit electrically charged polaritons at the single nanoparticle level.
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Affiliation(s)
- Jorge Cuadra
- Department of Physics , Chalmers University of Technology , 412 96 , Göteborg , Sweden
| | - Denis G Baranov
- Department of Physics , Chalmers University of Technology , 412 96 , Göteborg , Sweden
| | - Martin Wersäll
- Department of Physics , Chalmers University of Technology , 412 96 , Göteborg , Sweden
| | - Ruggero Verre
- Department of Physics , Chalmers University of Technology , 412 96 , Göteborg , Sweden
| | - Tomasz J Antosiewicz
- Department of Physics , Chalmers University of Technology , 412 96 , Göteborg , Sweden
- Centre of New Technologies , University of Warsaw , Banacha 2c , 02-097 Warsaw , Poland
| | - Timur Shegai
- Department of Physics , Chalmers University of Technology , 412 96 , Göteborg , Sweden
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40
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Wu F, Chen L, Zhang A, Hong YL, Shih NY, Cho SY, Drake GA, Fleetham T, Cong S, Cao X, Liu Q, Liu Y, Xu C, Ma Y, Shim M, Thompson ME, Ren W, Cheng HM, Zhou C. High-Performance Sub-Micrometer Channel WSe 2 Field-Effect Transistors Prepared Using a Flood-Dike Printing Method. ACS Nano 2017; 11:12536-12546. [PMID: 29219301 DOI: 10.1021/acsnano.7b06654] [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: 06/07/2023]
Abstract
Printing technology has potential to offer a cost-effective and scalable way to fabricate electronic devices based on two-dimensional (2D) transition metal dichalcogenides (TMDCs). However, limited by the registration accuracy and resolution of printing, the previously reported printed TMDC field-effect transistors (FETs) have relatively long channel lengths (13-200 μm), thus suffering low current-driving capabilities (≤0.02 μA/μm). Here, we report a "flood-dike" self-aligned printing technique that allows the formation of source/drain metal contacts on TMDC materials with sub-micrometer channel lengths in a reliable way. This self-aligned printing technique involves three steps: (i) printing of gold ink on a WSe2 flake to form the first gold electrode, (ii) modifying the surface of the first gold electrode with a self-assembled monolayer (SAM) to lower the surface tension and render the surface hydrophobic, and (iii) printing of gold ink close to the SAM-treated first electrode at a certain distance. During the third step, the gold ink would first spread toward the edge of the first electrode and then get stopped by the hydrophobic SAM coating, ending up forming a sub-micrometer channel. With this printing technique, we have successfully downscaled the channel length to ∼750 nm and achieved enhanced on-state current densities of ∼0.64 μA/μm (average) and high on/off current ratios of ∼3 × 105 (average). Furthermore, with our high-performance printed WSe2 FETs, driving capabilities for quantum-dot light-emitting diodes (LEDs), inorganic LEDs, and organic LEDs have been demonstrated, which reveals the potential of using printed TMDC electronics for display backplane applications.
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Affiliation(s)
| | | | | | - Yi-Lun Hong
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences , Shenyang 110016, People's Republic of China
- School of Materials Science and Engineering, University of Science and Technology of China , 72 Wenhua Road, Shenyang 110016, People's Republic of China
| | | | - Seong-Yong Cho
- Department of Materials Science and Engineering and Materials Research Laboratory, University of Illinois , Urbana, Illinois 61801, United States
| | - Gryphon A Drake
- Department of Materials Science and Engineering and Materials Research Laboratory, University of Illinois , Urbana, Illinois 61801, United States
| | | | | | | | | | | | | | | | - Moonsub Shim
- Department of Materials Science and Engineering and Materials Research Laboratory, University of Illinois , Urbana, Illinois 61801, United States
| | | | - Wencai Ren
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences , Shenyang 110016, People's Republic of China
| | - Hui-Ming Cheng
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences , Shenyang 110016, People's Republic of China
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41
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Rooney AP, Kozikov A, Rudenko AN, Prestat E, Hamer MJ, Withers F, Cao Y, Novoselov KS, Katsnelson MI, Gorbachev R, Haigh SJ. Observing Imperfection in Atomic Interfaces for van der Waals Heterostructures. Nano Lett 2017; 17:5222-5228. [PMID: 28741958 DOI: 10.1021/acs.nanolett.7b01248] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Vertically stacked van der Waals heterostructures are a lucrative platform for exploring the rich electronic and optoelectronic phenomena in two-dimensional materials. Their performance will be strongly affected by impurities and defects at the interfaces. Here we present the first systematic study of interfaces in van der Waals heterostructure using cross-sectional scanning transmission electron microscope (STEM) imaging. By measuring interlayer separations and comparing these to density functional theory (DFT) calculations we find that pristine interfaces exist between hBN and MoS2 or WS2 for stacks prepared by mechanical exfoliation in air. However, for two technologically important transition metal dichalcogenide (TMDC) systems, MoSe2 and WSe2, our measurement of interlayer separations provide the first evidence for impurity species being trapped at buried interfaces with hBN interfaces that are flat at the nanometer length scale. While decreasing the thickness of encapsulated WSe2 from bulk to monolayer we see a systematic increase in the interlayer separation. We attribute these differences to the thinnest TMDC flakes being flexible and hence able to deform mechanically around a sparse population of protruding interfacial impurities. We show that the air sensitive two-dimensional (2D) crystal NbSe2 can be fabricated into heterostructures with pristine interfaces by processing in an inert-gas environment. Finally we find that adopting glovebox transfer significantly improves the quality of interfaces for WSe2 compared to processing in air.
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Affiliation(s)
- Aidan P Rooney
- School of Materials, University of Manchester , Manchester M13 9PL, United Kingdom
| | - Aleksey Kozikov
- Manchester Centre for Mesoscience and Nanotechnology, University of Manchester , Manchester M13 9PL, United Kingdom
- School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom
- National Graphene Institute, University of Manchester , Manchester M13 9PL, United Kingdom
| | - Alexander N Rudenko
- Institute for Molecules and Materials, Radboud University , 6525 AJ Nijmegen, Netherlands
| | - Eric Prestat
- School of Materials, University of Manchester , Manchester M13 9PL, United Kingdom
| | - Matthew J Hamer
- Manchester Centre for Mesoscience and Nanotechnology, University of Manchester , Manchester M13 9PL, United Kingdom
- School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom
- National Graphene Institute, University of Manchester , Manchester M13 9PL, United Kingdom
| | - Freddie Withers
- College of Engineering, Mathematics, and Physical Sciences, University of Exeter , Exeter, Devon EX4 4SB, United Kingdom
| | - Yang Cao
- Manchester Centre for Mesoscience and Nanotechnology, University of Manchester , Manchester M13 9PL, United Kingdom
- School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom
- National Graphene Institute, University of Manchester , Manchester M13 9PL, United Kingdom
| | - Kostya S Novoselov
- Manchester Centre for Mesoscience and Nanotechnology, University of Manchester , Manchester M13 9PL, United Kingdom
- School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom
- National Graphene Institute, University of Manchester , Manchester M13 9PL, United Kingdom
| | - Mikhail I Katsnelson
- Institute for Molecules and Materials, Radboud University , 6525 AJ Nijmegen, Netherlands
| | - Roman Gorbachev
- Manchester Centre for Mesoscience and Nanotechnology, University of Manchester , Manchester M13 9PL, United Kingdom
- School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom
- National Graphene Institute, University of Manchester , Manchester M13 9PL, United Kingdom
| | - Sarah J Haigh
- School of Materials, University of Manchester , Manchester M13 9PL, United Kingdom
- National Graphene Institute, University of Manchester , Manchester M13 9PL, United Kingdom
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42
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Desai SB, Madhvapathy SR, Amani M, Kiriya D, Hettick M, Tosun M, Zhou Y, Dubey M, Ager JW, Chrzan D, Javey A. Gold-Mediated Exfoliation of Ultralarge Optoelectronically-Perfect Monolayers. Adv Mater 2016; 28:4053-8. [PMID: 27007751 DOI: 10.1002/adma.201506171] [Citation(s) in RCA: 145] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Revised: 01/25/2016] [Indexed: 05/21/2023]
Abstract
Gold-mediated exfoliation of ultralarge optoelectronically perfect monolayers with lateral dimensions up to ≈500 μm is reported. Electrical, optical, and X-ray photo-electron spectroscopy characterization show that the quality of the gold-exfoliated flakes is similar to that of tape-exfoliated flakes. Large-area flakes allow manufacturing of large-area mono-layer transition metal dichalcogenide electronics.
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Affiliation(s)
- Sujay B Desai
- Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Berkeley Sensor and Actuator Center, University of California, Berkeley, CA, 94720, USA
| | - Surabhi R Madhvapathy
- Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Matin Amani
- Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Berkeley Sensor and Actuator Center, University of California, Berkeley, CA, 94720, USA
| | - Daisuke Kiriya
- Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Berkeley Sensor and Actuator Center, University of California, Berkeley, CA, 94720, USA
| | - Mark Hettick
- Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Berkeley Sensor and Actuator Center, University of California, Berkeley, CA, 94720, USA
| | - Mahmut Tosun
- Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Berkeley Sensor and Actuator Center, University of California, Berkeley, CA, 94720, USA
| | - Yuzhi Zhou
- Materials Science and Engineering Department, University of California, Berkeley, CA, 94720, USA
| | - Madan Dubey
- Sensors and Electronic Devices Directorate, US Army Research Laboratory, Adelphi, MD, 20723, USA
| | - Joel W Ager
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Materials Science and Engineering Department, University of California, Berkeley, CA, 94720, USA
| | - Daryl Chrzan
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Materials Science and Engineering Department, University of California, Berkeley, CA, 94720, USA
| | - Ali Javey
- Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Berkeley Sensor and Actuator Center, University of California, Berkeley, CA, 94720, USA
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43
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Abstract
Semiconducting, two-dimensional molybdenum disulfide (MoS2) is considered a promising new material for highly sensitive photodetection, because of its atomically thin profile and favorable bandgap. However, reported photodetectors to date show strong variation in performance due to the detrimental and uncontrollable effects of environmental adsorbates on devices due to large surface to volume ratio. Here, we report on highly stable and high-performance monolayer and bilayer MoS2 photodetectors encapsulated with atomic layer deposited hafnium oxide. The protected devices show enhanced electronic properties by isolating them from the ambience as strong n-type doping, vanishing hysteresis, and reduced device resistance. By controlling the gate voltage the responsivity and temporal response can be tuned by several orders of magnitude with R ∼ 10-10(4) A/W and t ∼ 10 ms to 10 s. At strong negative gate voltage, the detector is operated at higher speed and simultaneously exhibits a low-bound, record sensitivity of D* ≥ 7.7 × 10(11) Jones. Our results lead the way for future application of ultrathin, flexible, and high-performance MoS2 detectors and prompt for further investigation in encapsulated transition metal dichalcogenide optoelectronics.
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Affiliation(s)
- Dominik Kufer
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology , Castelldefels, Barcelona 08860, Spain
| | - Gerasimos Konstantatos
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology , Castelldefels, Barcelona 08860, Spain
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44
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Tsai MY, Tarasov A, Hesabi ZR, Taghinejad H, Campbell PM, Joiner CA, Adibi A, Vogel EM. Flexible MoS2 Field-Effect Transistors for Gate-Tunable Piezoresistive Strain Sensors. ACS Appl Mater Interfaces 2015; 7:12850-5. [PMID: 26010011 DOI: 10.1021/acsami.5b02336] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Atomically thin molybdenum disulfide (MoS2) is a promising two-dimensional semiconductor for high-performance flexible electronics, sensors, transducers, and energy conversion. Here, piezoresistive strain sensing with flexible MoS2 field-effect transistors (FETs) made from highly uniform large-area films is demonstrated. The origin of the piezoresistivity in MoS2 is the strain-induced band gap change, which is confirmed by optical reflection spectroscopy. In addition, the sensitivity to strain can be tuned by more than 1 order of magnitude by adjusting the Fermi level via gate biasing.
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Affiliation(s)
- Meng-Yen Tsai
- †School of Materials Science and Engineering and ‡School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Alexey Tarasov
- †School of Materials Science and Engineering and ‡School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Zohreh R Hesabi
- †School of Materials Science and Engineering and ‡School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Hossein Taghinejad
- †School of Materials Science and Engineering and ‡School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Philip M Campbell
- †School of Materials Science and Engineering and ‡School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Corey A Joiner
- †School of Materials Science and Engineering and ‡School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Ali Adibi
- †School of Materials Science and Engineering and ‡School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Eric M Vogel
- †School of Materials Science and Engineering and ‡School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
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45
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Howell SL, Jariwala D, Wu CC, Chen KS, Sangwan VK, Kang J, Marks TJ, Hersam MC, Lauhon LJ. Investigation of band-offsets at monolayer-multilayer MoS₂ junctions by scanning photocurrent microscopy. Nano Lett 2015; 15:2278-84. [PMID: 25807012 DOI: 10.1021/nl504311p] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The thickness-dependent band structure of MoS2 implies that discontinuities in energy bands exist at the interface of monolayer (1L) and multilayer (ML) thin films. The characteristics of such heterojunctions are analyzed here using current versus voltage measurements, scanning photocurrent microscopy, and finite element simulations of charge carrier transport. Rectifying I-V curves are consistently observed between contacts on opposite sides of 1L/ML junctions, and a strong bias-dependent photocurrent is observed at the junction. Finite element device simulations with varying carrier concentrations and electron affinities show that a type II band alignment at single layer/multilayer junctions reproduces both the rectifying electrical characteristics and the photocurrent response under bias. However, the zero-bias junction photocurrent and its energy dependence are not explained by conventional photovoltaic and photothermoelectric mechanisms, indicating the contributions of hot carriers.
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Affiliation(s)
- Sarah L Howell
- †Department of Materials Science and Engineering, ‡Department of Chemistry, §Department of Medicine, and ∥Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States
| | - Deep Jariwala
- †Department of Materials Science and Engineering, ‡Department of Chemistry, §Department of Medicine, and ∥Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States
| | - Chung-Chiang Wu
- †Department of Materials Science and Engineering, ‡Department of Chemistry, §Department of Medicine, and ∥Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States
| | - Kan-Sheng Chen
- †Department of Materials Science and Engineering, ‡Department of Chemistry, §Department of Medicine, and ∥Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States
| | - Vinod K Sangwan
- †Department of Materials Science and Engineering, ‡Department of Chemistry, §Department of Medicine, and ∥Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States
| | - Junmo Kang
- †Department of Materials Science and Engineering, ‡Department of Chemistry, §Department of Medicine, and ∥Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States
| | - Tobin J Marks
- †Department of Materials Science and Engineering, ‡Department of Chemistry, §Department of Medicine, and ∥Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States
| | - Mark C Hersam
- †Department of Materials Science and Engineering, ‡Department of Chemistry, §Department of Medicine, and ∥Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States
| | - Lincoln J Lauhon
- †Department of Materials Science and Engineering, ‡Department of Chemistry, §Department of Medicine, and ∥Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States
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Chen L, Liu B, Abbas AN, Ma Y, Fang X, Liu Y, Zhou C. Screw-dislocation-driven growth of two-dimensional few-layer and pyramid-like WSe₂ by sulfur-assisted chemical vapor deposition. ACS Nano 2014; 8:11543-11551. [PMID: 25350314 DOI: 10.1021/nn504775f] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Two-dimensional (2D) layered tungsten diselenides (WSe2) material has recently drawn a lot of attention due to its unique optoelectronic properties and ambipolar transport behavior. However, direct chemical vapor deposition (CVD) synthesis of 2D WSe2 is not as straightforward as other 2D materials due to the low reactivity between reactants in WSe2 synthesis. In addition, the growth mechanism of WSe2 in such CVD process remains unclear. Here we report the observation of a screw-dislocation-driven (SDD) spiral growth of 2D WSe2 flakes and pyramid-like structures using a sulfur-assisted CVD method. Few-layer and pyramid-like WSe2 flakes instead of monolayer were synthesized by introducing a small amount of sulfur as a reducer to help the selenization of WO3, which is the precursor of tungsten. Clear observations of steps, helical fringes, and herringbone contours under atomic force microscope characterization reveal the existence of screw dislocations in the as-grown WSe2. The generation and propagation mechanisms of screw dislocations during the growth of WSe2 were discussed. Back-gated field-effect transistors were made on these 2D WSe2 materials, which show on/off current ratios of 10(6) and mobility up to 44 cm(2)/(V·s).
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Affiliation(s)
- Liang Chen
- Department of Electrical Engineering, University of Southern California , Los Angeles, California 90089, United States
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