401
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Chi ZH, Zhao XM, Zhang H, Goncharov AF, Lobanov SS, Kagayama T, Sakata M, Chen XJ. Pressure-induced metallization of molybdenum disulfide. PHYSICAL REVIEW LETTERS 2014; 113:036802. [PMID: 25083660 DOI: 10.1103/physrevlett.113.036802] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Indexed: 05/13/2023]
Abstract
X-ray diffraction, Raman spectroscopy, and electrical conductivity measurements of molybdenum disulfide MoS(2) are performed at pressures up to 81 GPa in diamond anvil cells. Above 20 GPa, we find discontinuous changes in Raman spectra and x-ray diffraction patterns which provide evidence for isostructural phase transition from 2H(c) to 2H(a) modification through layer sliding previously predicted theoretically. This first-order transition, which is completed around 40 GPa, is characterized by a collapse in the c-lattice parameter and volume and also by changes in interlayer bonding. After the phase transition completion, MoS(2) becomes metallic. The reversibility of the phase transition is identified from all these techniques.
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Affiliation(s)
- Zhen-Hua Chi
- Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, People's Republic of China
| | - Xiao-Miao Zhao
- Center for High Pressure Science and Technology Advanced Research, Shanghai 201203, People's Republic of China and Department of Physics, South China University of Technology, Guangzhou 510640, People's Republic of China
| | - Haidong Zhang
- Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C. 20015, USA
| | - Alexander F Goncharov
- Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, People's Republic of China and Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C. 20015, USA
| | - Sergey S Lobanov
- Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C. 20015, USA and V.S. Sobolev Institute of Geology and Mineralogy SB RAS, Novosibirsk 630090, Russia
| | - Tomoko Kagayama
- KYOKUGEN, Center for Quantum Science and Technology under Extreme Conditions, Osaka University, Osaka 560-8531, Japan
| | - Masafumi Sakata
- KYOKUGEN, Center for Quantum Science and Technology under Extreme Conditions, Osaka University, Osaka 560-8531, Japan
| | - Xiao-Jia Chen
- Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, People's Republic of China and Center for High Pressure Science and Technology Advanced Research, Shanghai 201203, People's Republic of China and Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C. 20015, USA
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402
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Lattice strain effects on the optical properties of MoS2 nanosheets. Sci Rep 2014; 4:5649. [PMID: 25008782 PMCID: PMC4090623 DOI: 10.1038/srep05649] [Citation(s) in RCA: 133] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Accepted: 06/24/2014] [Indexed: 12/22/2022] Open
Abstract
“Strain engineering” in functional materials has been widely explored to tailor the physical properties of electronic materials and improve their electrical and/or optical properties. Here, we exploit both in plane and out of plane uniaxial tensile strains in MoS2 to modulate its band gap and engineer its optical properties. We utilize X-ray diffraction and cross-sectional transmission electron microscopy to quantify the strains in the as-synthesized MoS2 nanosheets and apply measured shifts of Raman-active modes to confirm lattice strain modification of both the out-of-plane and in-plane phonon vibrations of the MoS2 nanosheets. The induced band gap evolution due to in-plane and out-of-plane tensile stresses is validated by photoluminescence (PL) measurements, promising a potential route for unprecedented manipulation of the physical, electrical and optical properties of MoS2.
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403
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van der Zande AM, Kunstmann J, Chernikov A, Chenet DA, You Y, Zhang X, Huang PY, Berkelbach TC, Wang L, Zhang F, Hybertsen MS, Muller DA, Reichman DR, Heinz TF, Hone JC. Tailoring the electronic structure in bilayer molybdenum disulfide via interlayer twist. NANO LETTERS 2014; 14:3869-75. [PMID: 24933687 DOI: 10.1021/nl501077m] [Citation(s) in RCA: 149] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Molybdenum disulfide bilayers with well-defined interlayer twist angle were constructed by stacking single-crystal monolayers. Varying interlayer twist angle results in strong tuning of the indirect optical transition energy and second-harmonic generation and weak tuning of direct optical transition energies and Raman mode frequencies. Electronic structure calculations show the interlayer separation changes with twist due to repulsion between sulfur atoms, resulting in shifts of the indirect optical transition energies. These results show that interlayer alignment is a crucial variable in tailoring the properties of two-dimensional heterostructures.
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Affiliation(s)
- Arend M van der Zande
- Energy Frontier Research Center, ‡Department of Mechanical Engineering, §Department of Chemistry, and ∥Departments of Physics and Electrical Engineering, Columbia University , New York, New York 10027, United States
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404
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Yang S, Tongay S, Li Y, Yue Q, Xia JB, Li SS, Li J, Wei SH. Layer-dependent electrical and optoelectronic responses of ReSe2 nanosheet transistors. NANOSCALE 2014; 6:7226-31. [PMID: 24882603 DOI: 10.1039/c4nr01741b] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The ability to control the appropriate layer thickness of transition metal dichalcogenides (TMDs) affords the opportunity to engineer many properties for a variety of applications in possible technological fields. Here we demonstrate that band-gap and mobility of ReSe2 nanosheet, a new member of the TMDs, increase when the layer number decreases, thus influencing the performances of ReSe2 transistors with different layers. A single-layer ReSe2 transistor shows much higher device mobility of 9.78 cm(2) V(-1) s(-1) than few-layer transistors (0.10 cm(2) V(-1) s(-1)). Moreover, a single-layer device shows high sensitivity to red light (633 nm) and has a light-improved mobility of 14.1 cm(2) V(-1) s(-1). Molecular physisorption is used as "gating" to modulate the carrier density of our single-layer transistors, resulting in a high photoresponsivity (Rλ) of 95 A W(-1) and external quantum efficiency (EQE) of 18 645% in O2 environment. This work highlights the fact that the properties of ReSe2 can be tuned in terms of the number of layers and gas molecule gating, and single-layer ReSe2 with appropriate band-gap is a promising material for future functional device applications.
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Affiliation(s)
- Shengxue Yang
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China.
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405
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Yim C, O'Brien M, McEvoy N, Riazimehr S, Schäfer-Eberwein H, Bablich A, Pawar R, Iannaccone G, Downing C, Fiori G, Lemme MC, Duesberg GS. Heterojunction hybrid devices from vapor phase grown MoS2. Sci Rep 2014; 4:5458. [PMID: 24975741 PMCID: PMC4074969 DOI: 10.1038/srep05458] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Accepted: 06/09/2014] [Indexed: 11/25/2022] Open
Abstract
We investigate a vertically-stacked hybrid photodiode consisting of a thin n-type molybdenum disulfide (MoS2) layer transferred onto p-type silicon. The fabrication is scalable as the MoS2 is grown by a controlled and tunable vapor phase sulfurization process. The obtained large-scale p-n heterojunction diodes exhibit notable photoconductivity which can be tuned by modifying the thickness of the MoS2 layer. The diodes have a broad spectral response due to direct and indirect band transitions of the nanoscale MoS2. Further, we observe a blue-shift of the spectral response into the visible range. The results are a significant step towards scalable fabrication of vertical devices from two-dimensional materials and constitute a new paradigm for materials engineering.
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Affiliation(s)
- Chanyoung Yim
- 1] School of Chemistry, Trinity College Dublin, Dublin 2, Ireland [2] Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN) and Advanced Materials and BioEngineering Research (AMBER) Centre, Trinity College Dublin, Dublin 2, Ireland
| | - Maria O'Brien
- 1] School of Chemistry, Trinity College Dublin, Dublin 2, Ireland [2] Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN) and Advanced Materials and BioEngineering Research (AMBER) Centre, Trinity College Dublin, Dublin 2, Ireland
| | - Niall McEvoy
- Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN) and Advanced Materials and BioEngineering Research (AMBER) Centre, Trinity College Dublin, Dublin 2, Ireland
| | - Sarah Riazimehr
- University of Siegen, Hölderlinstrasse 3, 57076 Siegen, Germany
| | | | - Andreas Bablich
- University of Siegen, Hölderlinstrasse 3, 57076 Siegen, Germany
| | - Ravinder Pawar
- Dipartimento di Ingegneria dell'Informazione, Università di Pisa, Via G. Caruso 16, 56122 Pisa, Italy
| | - Giuseppe Iannaccone
- Dipartimento di Ingegneria dell'Informazione, Università di Pisa, Via G. Caruso 16, 56122 Pisa, Italy
| | - Clive Downing
- Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN) and Advanced Materials and BioEngineering Research (AMBER) Centre, Trinity College Dublin, Dublin 2, Ireland
| | - Gianluca Fiori
- Dipartimento di Ingegneria dell'Informazione, Università di Pisa, Via G. Caruso 16, 56122 Pisa, Italy
| | - Max C Lemme
- University of Siegen, Hölderlinstrasse 3, 57076 Siegen, Germany
| | - Georg S Duesberg
- 1] School of Chemistry, Trinity College Dublin, Dublin 2, Ireland [2] Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN) and Advanced Materials and BioEngineering Research (AMBER) Centre, Trinity College Dublin, Dublin 2, Ireland
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406
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Lee YT, Choi K, Lee HS, Min SW, Jeon PJ, Hwang DK, Choi HJ, Im S. Graphene versus ohmic metal as source-drain electrode for MoS₂ nanosheet transistor channel. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2014; 10:2356-2361. [PMID: 24591250 DOI: 10.1002/smll.201303908] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2013] [Indexed: 06/03/2023]
Affiliation(s)
- Young Tack Lee
- Department of Physics and Institute of Physics and Applied Physics, Yonsei University, 262 Seongsanno, Seodaemun-gu, Seoul, 120-749, Korea
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407
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Zhang J, Yu H, Chen W, Tian X, Liu D, Cheng M, Xie G, Yang W, Yang R, Bai X, Shi D, Zhang G. Scalable growth of high-quality polycrystalline MoS(2) monolayers on SiO(2) with tunable grain sizes. ACS NANO 2014; 8:6024-30. [PMID: 24818518 DOI: 10.1021/nn5020819] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We report a scalable growth of monolayer MoS2 films on SiO2 substrates by chemical vapor deposition. As-grown polycrystalline MoS2 films are continuous over the entire substrate surface with a tunable grain size from ∼20 nm up to ∼1 μm. An obvious blue-shift (up to 80 meV) of photoluminescence peaks was observed from a series samples with different grain sizes. Back-gated field effect transistors based on a polycrystalline MoS2 film with a typical grain size of ∼600 nm shows a field mobility of ∼7 cm(2)/(V s) and on/off ratio of ∼10(6), comparable to those achieved from exfoliated MoS2. Our work provides a route toward scaled-up synthesis of high-quality monolayer MoS2 for electronic and optoelectronic devices.
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Affiliation(s)
- Jing Zhang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China
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408
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Roy T, Tosun M, Kang JS, Sachid AB, Desai SB, Hettick M, Hu CC, Javey A. Field-effect transistors built from all two-dimensional material components. ACS NANO 2014; 8:6259-6264. [PMID: 24779528 DOI: 10.1021/nn501723y] [Citation(s) in RCA: 255] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We demonstrate field-effect transistors using heterogeneously stacked two-dimensional materials for all of the components, including the semiconductor, insulator, and metal layers. Specifically, MoS2 is used as the active channel material, hexagonal-BN as the top-gate dielectric, and graphene as the source/drain and the top-gate contacts. This transistor exhibits n-type behavior with an ON/OFF current ratio of >10(6), and an electron mobility of ∼33 cm(2)/V·s. Uniquely, the mobility does not degrade at high gate voltages, presenting an important advantage over conventional Si transistors where enhanced surface roughness scattering severely reduces carrier mobilities at high gate-fields. A WSe2-MoS2 diode with graphene contacts is also demonstrated. The diode exhibits excellent rectification behavior and a low reverse bias current, suggesting high quality interfaces between the stacked layers. In this work, all interfaces are based on van der Waals bonding, presenting a unique device architecture where crystalline, layered materials with atomically uniform thicknesses are stacked on demand, without the lattice parameter constraints. The results demonstrate the promise of using an all-layered material system for future electronic applications.
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Affiliation(s)
- Tania Roy
- Electrical Engineering and Computer Sciences, University of California , Berkeley, California 94720, United States
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409
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Xie X, Sarkar D, Liu W, Kang J, Marinov O, Deen MJ, Banerjee K. Low-frequency noise in bilayer MoS(2) transistor. ACS NANO 2014; 8:5633-5640. [PMID: 24708223 DOI: 10.1021/nn4066473] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Low-frequency noise is a significant limitation on the performance of nanoscale electronic devices. This limitation is especially important for devices based on two-dimensional (2D) materials such as graphene and transition metal dichalcogenides (TMDs), which have atomically thin bodies and, hence, are severely affected by surface contaminants. Here, we investigate the low-frequency noise of transistors based on molybdenum disulfide (MoS2), which is a typical example of TMD. The noise measurements performed on bilayer MoS2 channel transistors show a noise peak in the gate-voltage dependence data, which has also been reported for graphene. To understand the peak, a trap decay-time based model is developed by revisiting the carrier number fluctuation model. Our analysis reveals that the peak originates from the fact that the decay time of the traps for a 2D device channel is governed by the van der Waals bonds between the 2D material and the surroundings. Our model is generic to all 2D materials and can be applied to explain the V, M and Λ shaped dependence of noise on the gate voltage in graphene transistors, as well as the noise shape dependency on the number of atomic layers of other 2D materials. Since the van der Waals bonding between the surface traps and 2D materials is weak, in accordance with the developed physical model, an annealing process is shown to significantly reduce the trap density, thereby reducing the low-frequency noise.
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Affiliation(s)
- Xuejun Xie
- Department of Electrical and Computer Engineering, University of California , Santa Barbara, California 93106, United States
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410
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Lin J, Cretu O, Zhou W, Suenaga K, Prasai D, Bolotin KI, Cuong NT, Otani M, Okada S, Lupini AR, Idrobo JC, Caudel D, Burger A, Ghimire NJ, Yan J, Mandrus DG, Pennycook SJ, Pantelides ST. Flexible metallic nanowires with self-adaptive contacts to semiconducting transition-metal dichalcogenide monolayers. NATURE NANOTECHNOLOGY 2014; 9:436-42. [PMID: 24776648 DOI: 10.1038/nnano.2014.81] [Citation(s) in RCA: 135] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Accepted: 03/20/2014] [Indexed: 05/04/2023]
Abstract
In the pursuit of ultrasmall electronic components, monolayer electronic devices have recently been fabricated using transition-metal dichalcogenides. Monolayers of these materials are semiconducting, but nanowires with stoichiometry MX (M = Mo or W, X = S or Se) have been predicted to be metallic. Such nanowires have been chemically synthesized. However, the controlled connection of individual nanowires to monolayers, an important step in creating a two-dimensional integrated circuit, has so far remained elusive. In this work, by steering a focused electron beam, we directly fabricate MX nanowires that are less than a nanometre in width and Y junctions that connect designated points within a transition-metal dichalcogenide monolayer. In situ electrical measurements demonstrate that these nanowires are metallic, so they may serve as interconnects in future flexible nanocircuits fabricated entirely from the same monolayer. Sequential atom-resolved Z-contrast images reveal that the nanowires rotate and flex continuously under momentum transfer from the electron beam, while maintaining their structural integrity. They therefore exhibit self-adaptive connections to the monolayer from which they are sculpted. We find that the nanowires remain conductive while undergoing severe mechanical deformations, thus showing promise for mechanically robust flexible electronics. Density functional theory calculations further confirm the metallicity of the nanowires and account for their beam-induced mechanical behaviour. These results show that direct patterning of one-dimensional conducting nanowires in two-dimensional semiconducting materials with nanometre precision is possible using electron-beam-based techniques.
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Affiliation(s)
- Junhao Lin
- 1] Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA [2] Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA [3]
| | - Ovidiu Cretu
- 1] National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565, Japan [2]
| | - Wu Zhou
- Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Kazu Suenaga
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565, Japan
| | - Dhiraj Prasai
- Interdisciplinary Graduate Program in Materials Science, Vanderbilt University, Nashville, Tennessee 37235, USA
| | - Kirill I Bolotin
- Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA
| | - Nguyen Thanh Cuong
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565, Japan
| | - Minoru Otani
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565, Japan
| | - Susumu Okada
- Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571, Japan
| | - Andrew R Lupini
- Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Juan-Carlos Idrobo
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Dave Caudel
- 1] Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA [2] Department of Physics, Fisk University, Nashville, Tennessee 37208, USA
| | - Arnold Burger
- Department of Physics, Fisk University, Nashville, Tennessee 37208, USA
| | - Nirmal J Ghimire
- 1] Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA [2] Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Jiaqiang Yan
- 1] Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA [2] Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - David G Mandrus
- 1] Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA [2] Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA [3] Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Stephen J Pennycook
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Sokrates T Pantelides
- 1] Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA [2] Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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411
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Tosun M, Chuang S, Fang H, Sachid AB, Hettick M, Lin Y, Zeng Y, Javey A. High-gain inverters based on WSe2 complementary field-effect transistors. ACS NANO 2014; 8:4948-4953. [PMID: 24684575 DOI: 10.1021/nn5009929] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
In this work, the operation of n- and p-type field-effect transistors (FETs) on the same WSe2 flake is realized,and a complementary logic inverter is demonstrated. The p-FET is fabricated by contacting WSe2 with a high work function metal, Pt, which facilities hole injection at the source contact. The n-FET is realized by utilizing selective surface charge transfer doping with potassium to form degenerately doped n+ contacts for electron injection. An ON/OFF current ratio of >10(4) is achieved for both n- and p-FETs with similar ON current densities. A dc voltage gain of >12 is measured for the complementary WSe2 inverter. This work presents an important advance toward realization of complementary logic devices based on layered chalcogenide semiconductors for electronic applications.
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Affiliation(s)
- Mahmut Tosun
- Electrical Engineering and Computer Sciences, University of California , Berkeley, California 94720, United States
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412
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Hosseini Shokouh SH, Pezeshki A, Ali Raza SR, Choi K, Min SW, Jeon PJ, Lee HS, Im S. Molybdenum disulfide nanoflake-zinc oxide nanowire hybrid photoinverter. ACS NANO 2014; 8:5174-5181. [PMID: 24717126 DOI: 10.1021/nn501230v] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We demonstrate a hybrid inverter-type nanodevice composed of a MoS2 nanoflake field-effect transistor (FET) and ZnO nanowire Schottky diode on one substrate, aiming at a one-dimensional (1D)-two-dimensional (2D) hybrid integrated electronic circuit with multifunctional capacities of low power consumption, high gain, and photodetection. In the present work, we used a nanotransfer printing method using polydimethylsiloxane for the fabrication of patterned bottom-gate MoS2 nanoflake FETs, so that they could be placed near the ZnO nanowire Schottky diodes that were initially fabricated. The ZnO nanowire Schottky diode and MoS2 FET worked respectively as load and driver for a logic inverter, which exhibits a high voltage gain of ∼50 at a supply voltage of 5 V and also shows a low power consumption of less than 50 nW. Moreover, our inverter effectively operates as a photoinverter, detecting visible photons, since MoS2 FETs appear very photosensitive, while the serially connected ZnO nanowire Schottky diode was blind to visible light. Our 1D-2D hybrid nanoinverter would be quite promising for both logic and photosensing applications due to its performance and simple device configuration as well.
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413
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Park W, Baik J, Kim TY, Cho K, Hong WK, Shin HJ, Lee T. Photoelectron spectroscopic imaging and device applications of large-area patternable single-layer MoS2 synthesized by chemical vapor deposition. ACS NANO 2014; 8:4961-4968. [PMID: 24730654 DOI: 10.1021/nn501019g] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Molybdenum disulfide (MoS2) films, which are only a single atomic layer thick, have been synthesized by chemical vapor deposition (CVD) and have gained significant attention due to their band-gap semiconducting properties. However, in order for them to be useful for the fabrication of practical devices, patterning processes that can be used to form specific MoS2 structures must be integrated with the existing synthetic approaches. Here, we report a method for the synthesis of centimeter-scale, high-quality single-layer MoS2 that can be directly patterned during CVD, so that postpatterning processes can be avoided and device fabrication can be streamlined. Utilizing X-ray photoelectron spectroscopic imaging, we characterize the chemical states of these CVD-synthesized single-layer MoS2 films and demonstrate that the triangular-shaped MoS2 are single-crystalline single-domain monolayers. We also demonstrate the use of these high-quality and directly patterned MoS2 films in electronic device applications by fabricating and characterizing field effect transistors.
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Affiliation(s)
- Woanseo Park
- Department of Physics and Astronomy and Institute of Applied Physics, Seoul National University , Seoul 151-747, Korea
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414
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Ganatra R, Zhang Q. Few-layer MoS2: a promising layered semiconductor. ACS NANO 2014; 8:4074-99. [PMID: 24660756 DOI: 10.1021/nn405938z] [Citation(s) in RCA: 461] [Impact Index Per Article: 46.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Due to the recent expanding interest in two-dimensional layered materials, molybdenum disulfide (MoS2) has been receiving much research attention. Having an ultrathin layered structure and an appreciable direct band gap of 1.9 eV in the monolayer regime, few-layer MoS2 has good potential applications in nanoelectronics, optoelectronics, and flexible devices. In addition, the capability of controlling spin and valley degrees of freedom makes it a promising material for spintronic and valleytronic devices. In this review, we attempt to provide an overview of the research relevant to the structural and physical properties, fabrication methods, and electronic devices of few-layer MoS2. Recent developments and advances in studying the material are highlighted.
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Affiliation(s)
- Rudren Ganatra
- NOVITAS, Nanoelectronics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University , 639798 Singapore
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415
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Nguyen LN, Lan YW, Chen JH, Chang TR, Zhong YL, Jeng HT, Li LJ, Chen CD. Resonant tunneling through discrete quantum states in stacked atomic-layered MoS2. NANO LETTERS 2014; 14:2381-2386. [PMID: 24745962 DOI: 10.1021/nl404790n] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Two-dimensional crystals can be assembled into three-dimensional stacks with atomic layer precision, which have already shown plenty of fascinating physical phenomena and been used for prototype vertical-field-effect-transistors.1,2 In this work, interlayer electron tunneling in stacked high-quality crystalline MoS2 films were investigated. A trilayered MoS2 film was sandwiched between top and bottom electrodes with an adjacent bottom gate, and the discrete energy levels in each layer could be tuned by bias and gate voltages. When the discrete energy levels aligned, a resonant tunneling peak appeared in the current-voltage characteristics. The peak position shifts linearly with perpendicular magnetic field, indicating formation of Landau levels. From this linear dependence, the effective mass and Fermi velocity are determined and are confirmed by electronic structure calculations. These fundamental parameters are useful for exploitation of its unique properties.
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Affiliation(s)
- Linh-Nam Nguyen
- Institute of Physics, Academia Sinica , Taipei 11529, Taiwan
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416
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Koskinen P, Fampiou I, Ramasubramaniam A. Density-functional tight-binding simulations of curvature-controlled layer decoupling and band-gap tuning in bilayer MoS2. PHYSICAL REVIEW LETTERS 2014; 112:186802. [PMID: 24856713 DOI: 10.1103/physrevlett.112.186802] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Indexed: 06/03/2023]
Abstract
Monolayer transition-metal dichalcogenides (TMDCs) display valley-selective circular dichroism due to the presence of time-reversal symmetry and the absence of inversion symmetry, making them promising candidates for valleytronics. In contrast, in bilayer TMDCs both symmetries are present and these desirable valley-selective properties are lost. Here, by using density-functional tight-binding electronic structure simulations and revised periodic boundary conditions, we show that bending of bilayer MoS2 sheets breaks band degeneracies and localizes states on separate layers due to bending-induced strain gradients across the sheets. We propose a strategy for employing bending deformations in bilayer TMDCs as a simple yet effective means of dynamically and reversibly tuning their band gaps while simultaneously tuning valley-selective physics.
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Affiliation(s)
- Pekka Koskinen
- NanoScience Center, Department of Physics, University of Jyväskylä, 40014 Jyväskylä, Finland
| | - Ioanna Fampiou
- Department of Mechanical and Industrial Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA
| | - Ashwin Ramasubramaniam
- Department of Mechanical and Industrial Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA
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417
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Lu N, Guo H, Wang L, Wu X, Zeng XC. van der Waals trilayers and superlattices: modification of electronic structures of MoS2 by intercalation. NANOSCALE 2014; 6:4566-71. [PMID: 24676364 DOI: 10.1039/c4nr00783b] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
We perform a comprehensive first-principles study of the electronic properties of van der Waals (vdW) trilayers via intercalating a two-dimensional (2D) monolayer (ML = BN, MoSe2, WS2, or WSe2) between a MoS2 bilayer to form various MoS2/ML/MoS2 sandwich trilayers. We find that the BN monolayer is the most effective sheet to decouple the interlayer vdW coupling of the MoS2 bilayer, and the resulting sandwich trilayer can recover the electronic structures of the MoS2 monolayer, particularly the direct-gap character. Further study of the MoS2/BN superlattices confirms the effectiveness of the BN monolayer for the decoupling of the MoS2-MoS2 interaction. In addition, the intercalation of a transition-metal dichalcogenide (TMDC) MoSe2 or WSe2 sheet makes the sandwich trilayer undergo an indirect-gap to direct-gap transition due to the newly formed heterogeneous S/Se interfaces. In contrast, the MoS2/WS2/MoS2 sandwich trilayer still retains the indirect-gap character of the MoS2 bilayer due to the lack of the heterogeneous S/Se interfaces. Moreover, the 3D superlattice of the MoS2/TMDC heterostructures also exhibits similar electronic band characters to the MoS2/TMDC/MoS2 trilayer heterostructures, albeit a slight decrease of the bandgap compared to the trilayers. Compared to the bulk MoS2, the 3D MoS2/TMDC superlattice can give rise to new and distinctive properties. Our study offers not only new insights into electronic properties of the vdW multilayer heterostructures but also guidance in designing new heterostructures to modify electronic structures of 2D TMDC crystals.
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Affiliation(s)
- Ning Lu
- Center for Nano Science and Technology, Department of Physics, Anhui Normal University, Wuhu, Anhui 241000, China
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418
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Naumov NG, Korlyukov AA, Piryazev DA, Virovets AV, Fedorov VE. High-precision X-ray diffraction data, experimental and theoretical study of 2H-MoS2. Russ Chem Bull 2014. [DOI: 10.1007/s11172-013-0266-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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419
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420
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Liu H, Neal AT, Zhu Z, Luo Z, Xu X, Tománek D, Ye PD. Phosphorene: an unexplored 2D semiconductor with a high hole mobility. ACS NANO 2014; 8:4033-41. [PMID: 24655084 DOI: 10.1021/nn501226z] [Citation(s) in RCA: 2273] [Impact Index Per Article: 227.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
We introduce the 2D counterpart of layered black phosphorus, which we call phosphorene, as an unexplored p-type semiconducting material. Same as graphene and MoS2, single-layer phosphorene is flexible and can be mechanically exfoliated. We find phosphorene to be stable and, unlike graphene, to have an inherent, direct, and appreciable band gap. Our ab initio calculations indicate that the band gap is direct, depends on the number of layers and the in-layer strain, and is significantly larger than the bulk value of 0.31-0.36 eV. The observed photoluminescence peak of single-layer phosphorene in the visible optical range confirms that the band gap is larger than that of the bulk system. Our transport studies indicate a hole mobility that reflects the structural anisotropy of phosphorene and complements n-type MoS2. At room temperature, our few-layer phosphorene field-effect transistors with 1.0 μm channel length display a high on-current of 194 mA/mm, a high hole field-effect mobility of 286 cm(2)/V·s, and an on/off ratio of up to 10(4). We demonstrate the possibility of phosphorene integration by constructing a 2D CMOS inverter consisting of phosphorene PMOS and MoS2 NMOS transistors.
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Affiliation(s)
- Han Liu
- School of Electrical and Computer Engineering and ‡Birck Nanotechnology Center, Purdue University , West Lafayette, Indiana 47907, United States
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421
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Sharma D, Amani M, Motayed A, Shah PB, Birdwell AG, Najmaei S, Ajayan PM, Lou J, Dubey M, Li Q, Davydov AV. Electrical transport and low-frequency noise in chemical vapor deposited single-layer MoS2 devices. NANOTECHNOLOGY 2014; 25:155702. [PMID: 24642948 DOI: 10.1088/0957-4484/25/15/155702] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We have studied temperature-dependent (77-300 K) electrical characteristics and low-frequency noise (LFN) in chemical vapor deposited (CVD) single-layer molybdenum disulfide (MoS2) based back-gated field-effect transistors (FETs). Electrical characterization and LFN measurements were conducted on MoS2 FETs with Al2O3 top-surface passivation. We also studied the effect of top-surface passivation etching on the electrical characteristics of the device. Significant decrease in channel current and transconductance was observed in these devices after the Al2O3 passivation etching. For passivated devices, the two-terminal resistance variation with temperature showed a good fit to the activation energy model, whereas for the etched devices the trend indicated a hopping transport mechanism. A significant increase in the normalized drain current noise power spectral density (PSD) was observed after the etching of the top passivation layer. The observed channel current noise was explained using a standard unified model incorporating carrier number fluctuation and correlated surface mobility fluctuation mechanisms. Detailed analysis of the gate-referred noise voltage PSD indicated the presence of different trapping states in passivated devices when compared to the etched devices. Etched devices showed weak temperature dependence of the channel current noise, whereas passivated devices exhibited near-linear temperature dependence.
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Affiliation(s)
- Deepak Sharma
- Department of Electrical and Computer Engineering, George Mason University, Fairfax, VA 22030, USA. National Institute of Standards and Technology, Material Measurement Laboratory, Gaithersburg, MD 20899, USA
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422
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Cho K, Kim TY, Park W, Park J, Kim D, Jang J, Jeong H, Hong S, Lee T. Gate-bias stress-dependent photoconductive characteristics of multi-layer MoS2 field-effect transistors. NANOTECHNOLOGY 2014; 25:155201. [PMID: 24642746 DOI: 10.1088/0957-4484/25/15/155201] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We investigated the photoconductive characteristics of molybdenum disulfide (MoS2) field-effect transistors (FETs) that were fabricated with mechanically exfoliated multi-layer MoS2 flakes. Upon exposure to UV light, we observed an increase in the MoS2 FET current because of electron-hole pair generation. The MoS2 FET current decayed after the UV light was turned off. The current decay processes were fitted using exponential functions with different decay characteristics. Specifically, a fast decay was used at the early stages immediately after turning off the light to account for the exciton relaxation, and a slow decay was used at later stages long after turning off the light due to charge trapping at the oxygen-related defect sites on the MoS2 surface. This photocurrent decay phenomenon of the MoS2 FET was influenced by the measurement environment (i.e., vacuum or oxygen environment) and the electrical gate-bias stress conditions (positive or negative gate biases). The results of this study will enhance the understanding of the influence of environmental and measurement conditions on the optical and electrical properties of MoS2 FETs.
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Affiliation(s)
- Kyungjune Cho
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul 151-747, Korea
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423
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Cheng L, Liu J, Gu X, Gong H, Shi X, Liu T, Wang C, Wang X, Liu G, Xing H, Bu W, Sun B, Liu Z. PEGylated WS(2) nanosheets as a multifunctional theranostic agent for in vivo dual-modal CT/photoacoustic imaging guided photothermal therapy. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2014; 26:1886-93. [PMID: 24375758 DOI: 10.1002/adma.201304497] [Citation(s) in RCA: 754] [Impact Index Per Article: 75.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 10/10/2013] [Indexed: 05/22/2023]
Abstract
A new generation of photothermal theranostic agents is developed based on PEGylated WS2 nanosheets. Bimodal in vivo CT/photoacoustic imaging reveals strong tumor contrast after either intratumoral or intravenous injection of WS2 -PEG. In vivo photothermal treatment is then conducted in a mouse tumor model, achieving excellent therapeutic efficacy with complete ablation of tumors. This work promises further exploration of transition-metal dichalcogenides for biomedical applications, such as cancer imaging and therapy.
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Affiliation(s)
- Liang Cheng
- Institute of Functional Nano & Soft Materials (FUNSOM), Collaborative Innovation Center of Suzhou, Nano Science and Technology, Soochow University, Suzhou, Jiangsu, 215123, China
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424
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Lopez-Sanchez O, Alarcon Llado E, Koman V, Fontcuberta i Morral A, Radenovic A, Kis A. Light generation and harvesting in a van der Waals heterostructure. ACS NANO 2014; 8:3042-8. [PMID: 24601517 PMCID: PMC3971963 DOI: 10.1021/nn500480u] [Citation(s) in RCA: 162] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Accepted: 02/28/2014] [Indexed: 05/20/2023]
Abstract
Two-dimensional (2D) materials are a new type of materials under intense study because of their interesting physical properties and wide range of potential applications from nanoelectronics to sensing and photonics. Monolayers of semiconducting transition metal dichalcogenides MoS2 or WSe2 have been proposed as promising channel materials for field-effect transistors. Their high mechanical flexibility, stability, and quality coupled with potentially inexpensive production methods offer potential advantages compared to organic and crystalline bulk semiconductors. Due to quantum mechanical confinement, the band gap in monolayer MoS2 is direct in nature, leading to a strong interaction with light that can be exploited for building phototransistors and ultrasensitive photodetectors. Here, we report on the realization of light-emitting diodes based on vertical heterojunctions composed of n-type monolayer MoS2 and p-type silicon. Careful interface engineering allows us to realize diodes showing rectification and light emission from the entire surface of the heterojunction. Electroluminescence spectra show clear signs of direct excitons related to the optical transitions between the conduction and valence bands. Our p-n diodes can also operate as solar cells, with typical external quantum efficiency exceeding 4%. Our work opens up the way to more sophisticated optoelectronic devices such as lasers and heterostructure solar cells based on hybrids of 2D semiconductors and silicon.
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Affiliation(s)
- Oriol Lopez-Sanchez
- Electrical Engineering Institute, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Esther Alarcon Llado
- Institute of Materials, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Volodymyr Koman
- Institute of Microtechnology, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Anna Fontcuberta i Morral
- Institute of Materials, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Aleksandra Radenovic
- Institute of Bioengineering, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Andras Kis
- Electrical Engineering Institute, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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425
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Liu K, Feng J, Kis A, Radenovic A. Atomically thin molybdenum disulfide nanopores with high sensitivity for DNA translocation. ACS NANO 2014; 8:2504-11. [PMID: 24547924 DOI: 10.1021/nn406102h] [Citation(s) in RCA: 263] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Atomically thin nanopore membranes are considered to be a promising approach to achieve single base resolution with the ultimate aim of rapid and cheap DNA sequencing. Molybdenum disulfide (MoS2) is newly emerging as a material complementary to graphene due to its semiconductive nature and other interesting physical properties that can enable a wide range of potential sensing and nanoelectronics applications. Here, we demonstrate that monolayer or few-layer thick exfoliated MoS2 with subnanometer thickness can be transferred and suspended on a predesigned location on the 20 nm thick SiNx membranes. Nanopores in MoS2 are further sculpted with variable sizes using a transmission electron microscope (TEM) to drill through suspended portions of the MoS2 membrane. Various types of double-stranded (ds) DNA with different lengths and conformations are translocated through such a novel architecture, showing improved sensitivity (signal-to-noise ratio>10) compared to the conventional silicon nitride (SiNx) nanopores with tens of nanometers thickness. Unlike graphene nanopores, no special surface treatment is needed to avoid hydrophobic interaction between DNA and the surface. Our results imply that MoS2 membranes with nanopore can complement graphene nanopore membranes and offer potentially better performance in transverse detection.
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Affiliation(s)
- Ke Liu
- Laboratory of Nanoscale Biology, Institute of Bioengineering, School of Engineering, EPFL , 1015 Lausanne, Switzerland
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426
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Cui Q, Ceballos F, Kumar N, Zhao H. Transient absorption microscopy of monolayer and bulk WSe2. ACS NANO 2014; 8:2970-2976. [PMID: 24547746 DOI: 10.1021/nn500277y] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We present an experimental investigation on the exciton dynamics of monolayer and bulk WSe2 samples, both of which are studied by femtosecond transient absorption microscopy. Under the excitation of a 405 nm pump pulse, the differential reflection signal of a probe pulse (tuned to the A-exciton resonance) reaches a peak rapidly that indicates an ultrafast formation process of excitons. By resolving the differential reflection signal in both time and space, we directly determine the exciton lifetimes of 18±1 and 160±10 ps and the exciton diffusion coefficients of 15±5 and 9±3 cm2/s in the monolayer and bulk samples, respectively. From these values, we deduce other parameters characterizing the exciton dynamics such as the diffusion length, the mobility, the mean free path, and the mean free length. These fundamental parameters are useful for understanding the excitons in monolayer and bulk WSe2 and are important for applications in optoelectronics, photonics, and electronics.
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Affiliation(s)
- Qiannan Cui
- Department of Physics and Astronomy, The University of Kansas , Lawrence, Kansas 66045, United States
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427
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Lu N, Guo H, Li L, Dai J, Wang L, Mei WN, Wu X, Zeng XC. MoS2/MX2 heterobilayers: bandgap engineering via tensile strain or external electrical field. NANOSCALE 2014; 6:2879-2886. [PMID: 24473269 DOI: 10.1039/c3nr06072a] [Citation(s) in RCA: 129] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We have performed a comprehensive first-principles study of the electronic and magnetic properties of two-dimensional (2D) transition-metal dichalcogenide (TMD) heterobilayers MX2/MoS2 (M = Mo, Cr, W, Fe, V; X = S, Se). For M = Mo, Cr, W; X = S, Se, all heterobilayers show semiconducting characteristics with an indirect bandgap with the exception of the WSe2/MoS2 heterobilayer which retains the direct-bandgap character of the constituent monolayer. For M = Fe, V; X = S, Se, the MX2/MoS2 heterobilayers exhibit metallic characters. Particular attention of this study has been focused on engineering the bandgap of the TMD heterobilayer materials via application of either a tensile strain or an external electric field. We find that with increasing either the biaxial or uniaxial tensile strain, the MX2/MoS2 (M = Mo, Cr, W; X = S, Se) heterobilayers can undergo a semiconductor-to-metal transition. For the WSe2/MoS2 heterobilayer, a direct-to-indirect bandgap transition may occur beyond a critical biaxial or uniaxial strain. For M (=Fe, V) and X (=S, Se), the magnetic moments of both metal and chalcogen atoms are enhanced when the MX2/MoS2 heterobilayers are under a biaxial tensile strain. Moreover, the bandgap of MX2/MoS2 (M = Mo, Cr, W; X = S, Se) heterobilayers can be reduced by the vertical electric field. For two heterobilayers MSe2/MoS2 (M = Mo, Cr), PBE calculations suggest that the indirect-to-direct bandgap transition may occur under an external electric field. The transition is attributed to the enhanced spontaneous polarization. The tunable bandgaps in general and possible indirect-direct bandgap transitions due to tensile strain or external electric field make the TMD heterobilayer materials a viable candidate for optoelectronic applications.
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Affiliation(s)
- Ning Lu
- Department of Physics, Anhui Normal University, Wuhu, Anhui 241000, China
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428
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Gu W, Shen J, Ma X. Fabrication and electrical properties of MoS2 nanodisc-based back-gated field effect transistors. NANOSCALE RESEARCH LETTERS 2014; 9:100. [PMID: 24576344 PMCID: PMC3943990 DOI: 10.1186/1556-276x-9-100] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Accepted: 02/19/2014] [Indexed: 05/31/2023]
Abstract
Two-dimensional (2D) molybdenum disulfide (MoS2) is an attractive alternative semiconductor material for next-generation low-power nanoelectronic applications, due to its special structure and large bandgap. Here, we report the fabrication of large-area MoS2 nanodiscs and their incorporation into back-gated field effect transistors (FETs) whose electrical properties we characterize. The MoS2 nanodiscs, fabricated via chemical vapor deposition (CVD), are homogeneous and continuous, and their thickness of around 5 nm is equal to a few layers of MoS2. In addition, we find that the MoS2 nanodisc-based back-gated field effect transistors with nickel electrodes achieve very high performance. The transistors exhibit an on/off current ratio of up to 1.9 × 105, and a maximum transconductance of up to 27 μS (5.4 μS/μm). Moreover, their mobility is as high as 368 cm2/Vs. Furthermore, the transistors have good output characteristics and can be easily modulated by the back gate. The electrical properties of the MoS2 nanodisc transistors are better than or comparable to those values extracted from single and multilayer MoS2 FETs.
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Affiliation(s)
- Weixia Gu
- School of Mathematics and Physics, Suzhou University of Science and Technology, 1# Kerui Road, Suzhou, Jiangsu 215009, China
| | - Jiaoyan Shen
- School of Mathematics and Physics, Suzhou University of Science and Technology, 1# Kerui Road, Suzhou, Jiangsu 215009, China
| | - Xiying Ma
- School of Mathematics and Physics, Suzhou University of Science and Technology, 1# Kerui Road, Suzhou, Jiangsu 215009, China
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429
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Jariwala D, Sangwan VK, Lauhon LJ, Marks TJ, Hersam MC. Emerging device applications for semiconducting two-dimensional transition metal dichalcogenides. ACS NANO 2014; 8:1102-20. [PMID: 24476095 DOI: 10.1021/nn500064s] [Citation(s) in RCA: 980] [Impact Index Per Article: 98.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/14/2023]
Abstract
With advances in exfoliation and synthetic techniques, atomically thin films of semiconducting transition metal dichalcogenides have recently been isolated and characterized. Their two-dimensional structure, coupled with a direct band gap in the visible portion of the electromagnetic spectrum, suggests suitability for digital electronics and optoelectronics. Toward that end, several classes of high-performance devices have been reported along with significant progress in understanding their physical properties. Here, we present a review of the architecture, operating principles, and physics of electronic and optoelectronic devices based on ultrathin transition metal dichalcogenide semiconductors. By critically assessing and comparing the performance of these devices with competing technologies, the merits and shortcomings of this emerging class of electronic materials are identified, thereby providing a roadmap for future development.
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Affiliation(s)
- Deep Jariwala
- Department of Materials Science and Engineering, ‡Department of Chemistry, and §Department of Medicine, Northwestern University , Evanston, Illinois 60208, United States
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430
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Gu X, Cui W, Song T, Liu C, Shi X, Wang S, Sun B. Solution-processed 2D niobium diselenide nanosheets as efficient hole-transport layers in organic solar cells. CHEMSUSCHEM 2014; 7:416-420. [PMID: 24464869 DOI: 10.1002/cssc.201300615] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Revised: 10/30/2013] [Indexed: 06/03/2023]
Abstract
Thin-layer, two-dimensional NbSe2 nanosheets with lower trap density have been obtained and act as an alternative hole-transporting layer to replace MoO3 in organic solar cells. If poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}):[6,6]-phenyl-C71-butyric acid methyl ester acts as an active layer, a power conversion efficiency of 8.10 % has been achieved without any further thermal treatment. The properties of this hole-transporting layer were investigated and the improvements in the devices are discussed.
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Affiliation(s)
- Xing Gu
- Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM) & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, 199 Ren-Ai Road, Suzhou Industrial Park, Suzhou, Jiangsu 215123 (PR China)
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431
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Wang R, Chien HC, Kumar J, Kumar N, Chiu HY, Zhao H. Third-harmonic generation in ultrathin films of MoS2. ACS APPLIED MATERIALS & INTERFACES 2014; 6:314-318. [PMID: 24320052 DOI: 10.1021/am4042542] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We observe optical third-harmonic generation in atomically thin films of MoS2 and deduce effective third-order nonlinear susceptibilities on the order of 10(-19) m(2)/V(2), which is comparable to that of commonly used semiconductors under resonant conditions. By measuring the susceptibility as a function of light wavelength, we find significant enhancements of the susceptibility by excitonic resonances. The demonstrated third-harmonic generation can be used for nonlinear optical identification of MoS2 atomic layers with high contrast, better distinguishing power of multilayers, and less restrictions to substrate selections. The size of the third-order nonlinear susceptibility suggests feasibility of exploring other types of third-order nonlinear optical effects of MoS2 two-dimensional crystals.
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Affiliation(s)
- Rui Wang
- Department of Physics and Astronomy, The University of Kansas , Lawrence, Kansas 66045, United States
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432
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High yield exfoliation of two-dimensional chalcogenides using sodium naphthalenide. Nat Commun 2014; 5:2995. [DOI: 10.1038/ncomms3995] [Citation(s) in RCA: 571] [Impact Index Per Article: 57.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Accepted: 11/22/2013] [Indexed: 12/22/2022] Open
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433
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Li BL, Luo HQ, Lei JL, Li NB. Hemin-functionalized MoS2 nanosheets: enhanced peroxidase-like catalytic activity with a steady state in aqueous solution. RSC Adv 2014. [DOI: 10.1039/c4ra01746c] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
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434
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Zibouche N, Philipsen P, Heine T, Kuc A. Electron transport in MoWSeS monolayers in the presence of an external electric field. Phys Chem Chem Phys 2014; 16:11251-5. [DOI: 10.1039/c4cp00966e] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The influence of an external electric field on single-layer transition-metal dichalcogenides TX2 with T = Mo, W and X = S, Se (MoWSeS) has been investigated by means of density-functional theory within two-dimensional periodic boundary conditions under consideration of relativistic effects including the spin–orbit interactions.
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Affiliation(s)
- Nourdine Zibouche
- School of Engineering and Science
- Jacobs University Bremen
- 28759 Bremen, Germany
| | - Pier Philipsen
- Scientific Computing & Modelling NV
- 1081 HV Amsterdam, The Netherlands
| | - Thomas Heine
- School of Engineering and Science
- Jacobs University Bremen
- 28759 Bremen, Germany
| | - Agnieszka Kuc
- School of Engineering and Science
- Jacobs University Bremen
- 28759 Bremen, Germany
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435
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Liu W, Yang X, Zhang Y, Xu M, Chen H. Ultra-stable two-dimensional MoS2 solution for highly efficient organic solar cells. RSC Adv 2014. [DOI: 10.1039/c4ra04116j] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A simple self-assembly procedure was developed for preparing a solution of 2D exfoliated MoS2 sheets with very long-term stability suitable for high-performance solar cell fabrication.
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Affiliation(s)
- Wenqing Liu
- State Key Laboratory of Silicon Materials
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization
- Department of Polymer Science and Engineering
- Zhejiang University
- Hangzhou 310027, P.R. China
| | - Xi Yang
- State Key Laboratory of Silicon Materials
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization
- Department of Polymer Science and Engineering
- Zhejiang University
- Hangzhou 310027, P.R. China
| | - Yingying Zhang
- State Key Laboratory of Silicon Materials
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization
- Department of Polymer Science and Engineering
- Zhejiang University
- Hangzhou 310027, P.R. China
| | - Mingsheng Xu
- State Key Laboratory of Silicon Materials
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization
- Department of Polymer Science and Engineering
- Zhejiang University
- Hangzhou 310027, P.R. China
| | - Hongzheng Chen
- State Key Laboratory of Silicon Materials
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization
- Department of Polymer Science and Engineering
- Zhejiang University
- Hangzhou 310027, P.R. China
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436
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Çakır D, Sahin H, Peeters FM. Doping of rhenium disulfide monolayers: a systematic first principles study. Phys Chem Chem Phys 2014; 16:16771-9. [DOI: 10.1039/c4cp02007c] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The absence of a direct-to-indirect band gap transition in ReS2 when going from the monolayer to bulk makes it special among the other semiconducting transition metal dichalcogenides.
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Affiliation(s)
- Deniz Çakır
- Department of Physics
- University of Antwerp
- 2020 Antwerp, Belgium
| | - Hasan Sahin
- Department of Physics
- University of Antwerp
- 2020 Antwerp, Belgium
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437
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Pu J, Li LJ, Takenobu T. Flexible and stretchable thin-film transistors based on molybdenum disulphide. Phys Chem Chem Phys 2014; 16:14996-5006. [DOI: 10.1039/c3cp55270e] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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438
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Song JG, Park J, Lee W, Choi T, Jung H, Lee CW, Hwang SH, Myoung JM, Jung JH, Kim SH, Lansalot-Matras C, Kim H. Layer-controlled, wafer-scale, and conformal synthesis of tungsten disulfide nanosheets using atomic layer deposition. ACS NANO 2013; 7:11333-40. [PMID: 24252136 DOI: 10.1021/nn405194e] [Citation(s) in RCA: 134] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The synthesis of atomically thin transition-metal disulfides (MS2) with layer controllability and large-area uniformity is an essential requirement for their application in electronic and optical devices. In this work, we describe a process for the synthesis of WS2 nanosheets through the sulfurization of an atomic layer deposition (ALD) WO3 film with systematic layer controllability and wafer-level uniformity. The X-ray photoemission spectroscopy, Raman, and photoluminescence measurements exhibit that the ALD-based WS2 nanosheets have good stoichiometry, clear Raman shift, and bandgap dependence as a function of the number of layers. The electron mobility of the monolayer WS2 measured using a field-effect transistor (FET) with a high-k dielectric gate insulator is shown to be better than that of CVD-grown WS2, and the subthreshold swing is comparable to that of an exfoliated MoS2 FET device. Moreover, by utilizing the high conformality of the ALD process, we have developed a process for the fabrication of WS2 nanotubes.
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Affiliation(s)
- Jeong-Gyu Song
- School of Electrical and Electronics Engineering and §Department of Materials Science and Engineering, Yonsei University , Seoul 120-749, Korea
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439
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Zhang Z, Zou X, Crespi VH, Yakobson BI. Intrinsic magnetism of grain boundaries in two-dimensional metal dichalcogenides. ACS NANO 2013; 7:10475-81. [PMID: 24206002 DOI: 10.1021/nn4052887] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Grain boundaries (GBs) are structural imperfections that typically degrade the performance of materials. Here we show that dislocations and GBs in two-dimensional (2D) metal dichalcogenides MX2 (M = Mo, W; X = S, Se) can actually improve the material by giving it a qualitatively new physical property: magnetism. The dislocations studied all display a substantial magnetic moment of ∼1 Bohr magneton. In contrast, dislocations in other well-studied 2D materials are typically nonmagnetic. GBs composed of pentagon-heptagon pairs interact ferromagnetically and transition from semiconductor to half-metal or metal as a function of tilt angle and/or doping level. When the tilt angle exceeds 47°, the structural energetics favor square-octagon pairs and the GB becomes an antiferromagnetic semiconductor. These exceptional magnetic properties arise from interplay of dislocation-induced localized states, doping, and locally unbalanced stoichiometry. Purposeful engineering of topological GBs may be able to convert MX2 into a promising 2D magnetic semiconductor.
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Affiliation(s)
- Zhuhua Zhang
- Department of Mechanical Engineering and Materials Science, Department of Chemistry, and the Smalley Institute for Nanoscale Science and Technology, Rice University , Houston, Texas 77005, United States
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440
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Park W, Yang JH, Kang CG, Lee YG, Hwang HJ, Cho C, Lim SK, Kang SC, Hong WK, Lee SK, Lee S, Lee BH. Characteristics of a pressure sensitive touch sensor using a piezoelectric PVDF-TrFE/MoS2 stack. NANOTECHNOLOGY 2013; 24:475501. [PMID: 24177860 DOI: 10.1088/0957-4484/24/47/475501] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A new touch sensor device has been demonstrated with molybdenum disulfide (MoS2) field effect transistors stacked with a piezoelectric polymer, polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE). The performance of two device stack structures, metal/PVDF-TrFE/MoS2 (MPM) and metal/PVDF-TrFE/Al2O3/MoS2 (MPAM), were compared as a function of the thickness of PVDF-TrFE and Al2O3. The sensitivity of the touch sensor has been improved by two orders of magnitude by reducing the charge scattering and enhancing the passivation effects using a thin Al2O3 interfacial layer. Reliable switching behavior has been demonstrated up to 120 touch press cycles.
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Affiliation(s)
- Woojin Park
- School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
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441
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Balendhran S, Walia S, Alsaif M, Nguyen EP, Ou JZ, Zhuiykov S, Sriram S, Bhaskaran M, Kalantar-Zadeh K. Field effect biosensing platform based on 2D α-MoO(3). ACS NANO 2013; 7:9753-9760. [PMID: 24180694 DOI: 10.1021/nn403241f] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Electrical-based biosensing platforms offer ease of fabrication and simple sensing solutions. Recently, two-dimensional (2D) semiconductors have been proven to be excellent for the fabrication of field effect transistors (FETs) due to their large transconductance, which can be efficiently used for developing sensitive bioplatforms. We present a 2D molybdenum trioxide (MoO3) FET based biosensing platform, using bovine serum albumin as a model protein. The conduction channel is a nanostructured film made of 2D α-MoO3 nanoflakes, with the majority of nanoflake thicknesses being equal to or less than 2.8 nm. The response time is impressively low (less than 10 s), which is due to the high permittivity of the 2D α-MoO3 nanoflakes. The system offers a competitive solution for future biosensing applications.
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442
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Hu T, Li R, Dong J. A new (2 × 1) dimerized structure of monolayer 1T-molybdenum disulfide, studied from first principles calculations. J Chem Phys 2013; 139:174702. [DOI: 10.1063/1.4827082] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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443
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Roy K, Padmanabhan M, Goswami S, Sai TP, Ramalingam G, Raghavan S, Ghosh A. Graphene-MoS2 hybrid structures for multifunctional photoresponsive memory devices. NATURE NANOTECHNOLOGY 2013; 8:826-30. [PMID: 24141541 DOI: 10.1038/nnano.2013.206] [Citation(s) in RCA: 541] [Impact Index Per Article: 49.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Accepted: 09/11/2013] [Indexed: 05/20/2023]
Abstract
Combining the electronic properties of graphene and molybdenum disulphide (MoS2) in hybrid heterostructures offers the possibility to create devices with various functionalities. Electronic logic and memory devices have already been constructed from graphene-MoS2 hybrids, but they do not make use of the photosensitivity of MoS2, which arises from its optical-range bandgap. Here, we demonstrate that graphene-on-MoS2 binary heterostructures display remarkable dual optoelectronic functionality, including highly sensitive photodetection and gate-tunable persistent photoconductivity. The responsivity of the hybrids was found to be nearly 1 × 10(10) A W(-1) at 130 K and 5 × 10(8) A W(-1) at room temperature, making them the most sensitive graphene-based photodetectors. When subjected to time-dependent photoillumination, the hybrids could also function as a rewritable optoelectronic switch or memory, where the persistent state shows almost no relaxation or decay within experimental timescales, indicating near-perfect charge retention. These effects can be quantitatively explained by gate-tunable charge exchange between the graphene and MoS2 layers, and may lead to new graphene-based optoelectronic devices that are naturally scalable for large-area applications at room temperature.
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Affiliation(s)
- Kallol Roy
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
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444
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Salvatore GA, Münzenrieder N, Barraud C, Petti L, Zysset C, Büthe L, Ensslin K, Tröster G. Fabrication and transfer of flexible few-layers MoS2 thin film transistors to any arbitrary substrate. ACS NANO 2013; 7:8809-8815. [PMID: 23991756 DOI: 10.1021/nn403248y] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Recently, transition metal dichalcogenides (TMDCs) have attracted interest thanks to their large field effective mobility (>100 cm(2)/V · s), sizable band gap (around 1-2 eV), and mechanical properties, which make them suitable for high performance and flexible electronics. In this paper, we present a process scheme enabling the fabrication and transfer of few-layers MoS2 thin film transistors from a silicon template to any arbitrary organic or inorganic and flexible or rigid substrate or support. The two-dimensional semiconductor is mechanically exfoliated from a bulk crystal on a silicon/polyvinyl alcohol (PVA)/polymethyl methacrylane (PMMA) stack optimized to ensure high contrast for the identification of subnanometer thick flakes. Thin film transistors (TFTs) with structured source/drain and gate electrodes are fabricated following a designed procedure including steps of UV lithography, wet etching, and atomic layer deposited (ALD) dielectric. Successively, after the dissolution of the PVA sacrificial layer in water, the PMMA film, with the devices on top, can be transferred to another substrate of choice. Here, we transferred the devices on a polyimide plastic foil and studied the performance when tensile strain is applied parallel to the TFT channel. We measured an electron field effective mobility of 19 cm(2)/(V s), an I(on)/I(off)ratio greater than 10(6), a gate leakage current as low as 0.3 pA/μm, and a subthreshold swing of about 250 mV/dec. The devices continue to work when bent to a radius of 5 mm and after 10 consecutive bending cycles. The proposed fabrication strategy can be extended to any kind of 2D materials and enable the realization of electronic circuits and optical devices easily transferrable to any other support.
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Affiliation(s)
- Giovanni A Salvatore
- Electronics Laboratory, Swiss Federal Institute of Technology , ETZ Gloriastrasse 35, Zürich, 8092, Switzerland
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445
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Song HS, Li SL, Gao L, Xu Y, Ueno K, Tang J, Cheng YB, Tsukagoshi K. High-performance top-gated monolayer SnS2 field-effect transistors and their integrated logic circuits. NANOSCALE 2013; 5:9666-70. [PMID: 23989804 DOI: 10.1039/c3nr01899g] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Two-dimensional (2D) layered semiconductors are very promising for post-silicon ultrathin channels and flexible electronics due to the remarkable dimensional and mechanical properties. Besides molybdenum disulfide (MoS2), the first recognized 2D semiconductor, it is also important to explore the wide spectrum of layered metal chalcogenides (LMCs) and to identify possible compounds with high performance. Here we report the fabrication of high-performance top-gated field-effect transistors (FETs) and related logic gates from monolayer tin disulfide (SnS2), a non-transition metal dichalcogenide. The measured carrier mobility of our monolayer devices reaches 50 cm(2) V(-1) s(-1), much higher than that of the back-gated counterparts (~1 cm(2) V(-1) s(-1)). Based on a direct-coupled FET logic technique, advanced Boolean logic gates and operations are also implemented, with a voltage gain of 3.5 and output swing of >90% for the NOT and NOR gates, respectively. The superior electrical and integration properties make monolayer SnS2 a strong candidate for next-generation atomic electronics.
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Affiliation(s)
- H S Song
- Wuhan National Laboratory for Optoelectronics (WNLO) and School of Optical and Electronic Information, Huazhong University of Science and Technology (HUST), Wuhan 430074, P. R. China. Tsukagoshi.Kazuhito@ nims.go.jp
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446
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Yue Q, Shao Z, Chang S, Li J. Adsorption of gas molecules on monolayer MoS2 and effect of applied electric field. NANOSCALE RESEARCH LETTERS 2013; 8:425. [PMID: 24134512 PMCID: PMC4015638 DOI: 10.1186/1556-276x-8-425] [Citation(s) in RCA: 215] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Accepted: 10/02/2013] [Indexed: 05/20/2023]
Abstract
: Using first-principles calculations, we investigate the adsorption of various gas molecules (H2, O2, H2O, NH3, NO, NO2, and CO) on monolayer MoS2. The most stable adsorption configuration, adsorption energy, and charge transfer are obtained. It is shown that all the molecules are weakly adsorbed on the monolayer MoS2 surface and act as charge acceptors for the monolayer, except NH3 which is found to be a charge donor. Furthermore, we show that charge transfer between the adsorbed molecule and MoS2 can be significantly modulated by a perpendicular electric field. Our theoretical results are consistent with the recent experiments and suggest MoS2 as a potential material for gas sensing application.
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Affiliation(s)
- Qu Yue
- College of Science, National University of Defense Technology, Changsha 410073, China
| | - Zhengzheng Shao
- College of Science, National University of Defense Technology, Changsha 410073, China
| | - Shengli Chang
- College of Science, National University of Defense Technology, Changsha 410073, China
| | - Jingbo Li
- State Key Laboratory for Superlattice and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
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447
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Electromechanics in MoS₂ and WS₂: nanotubes vs. monolayers. Sci Rep 2013; 3:2961. [PMID: 24129919 PMCID: PMC3797429 DOI: 10.1038/srep02961] [Citation(s) in RCA: 122] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Accepted: 10/01/2013] [Indexed: 12/18/2022] Open
Abstract
The transition-metal dichalcogenides (TMD) MoS2 and WS2 show remarkable electromechanical properties. Strain modifies the direct band gap into an indirect one, and substantial strain even induces an semiconductor-metal transition. Providing strain through mechanical contacts is difficult for TMD monolayers, but state-of-the-art for TMD nanotubes. We show using density-functional theory that similar electromechanical properties as in monolayer and bulk TMDs are found for large diameter TMD single- (SWNT) and multi-walled nanotubes (MWNTs). The semiconductor-metal transition occurs at elongations of 16%. We show that Raman signals of the in-plane and out-of-plane lattice vibrations depend significantly and linearly on the strain, showing that Raman spectroscopy is an excellent tool to determine the strain of the individual nanotubes and hence monitor the progress of nanoelectromechanical experiments in situ. TMD MWNTs show twice the electric conductance compared to SWNTs, and each wall of the MWNTs contributes to the conductance proportional to its diameter.
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448
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Yoon J, Park W, Bae GY, Kim Y, Jang HS, Hyun Y, Lim SK, Kahng YH, Hong WK, Lee BH, Ko HC. Highly flexible and transparent multilayer MoS2 transistors with graphene electrodes. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2013; 9:3295-3300. [PMID: 23420782 DOI: 10.1002/smll.201300134] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Indexed: 06/01/2023]
Abstract
A highly flexible and transparent transistor is developed based on an exfoliated MoS2 channel and CVD-grown graphene source/drain electrodes. Introducing the 2D nanomaterials provides a high mechanical flexibility, optical transmittance (∼74%), and current on/off ratio (>10(4)) with an average field effect mobility of ∼4.7 cm(2) V(-1) s(-1), all of which cannot be achieved by other transistors consisting of a MoS2 active channel/metal electrodes or graphene channel/graphene electrodes. In particular, a low Schottky barrier (∼22 meV) forms at the MoS2 /graphene interface, which is comparable to the MoS2 /metal interface. The high stability in electronic performance of the devices upon bending up to ±2.2 mm in compressive and tensile modes, and the ability to recover electrical properties after degradation upon annealing, reveal the efficacy of using 2D materials for creating highly flexible and transparent devices.
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Affiliation(s)
- Jongwon Yoon
- School of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), 261 Cheomdan-gwagiro (Oryong-Dong), Buk-Gu, Gwangju 500-712, Korea
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449
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Cho K, Park W, Park J, Jeong H, Jang J, Kim TY, Hong WK, Hong S, Lee T. Electric stress-induced threshold voltage instability of multilayer MoS2 field effect transistors. ACS NANO 2013; 7:7751-8. [PMID: 23924186 DOI: 10.1021/nn402348r] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
We investigated the gate bias stress effects of multilayered MoS2 field effect transistors (FETs) with a back-gated configuration. The electrical stability of the MoS2 FETs can be significantly influenced by the electrical stress type, relative sweep rate, and stress time in an ambient environment. Specifically, when a positive gate bias stress was applied to the MoS2 FET, the current of the device decreased and its threshold shifted in the positive gate bias direction. In contrast, with a negative gate bias stress, the current of the device increased and the threshold shifted in the negative gate bias direction. The gate bias stress effects were enhanced when a gate bias was applied for a longer time or when a slower sweep rate was used. These phenomena can be explained by the charge trapping due to the adsorption or desorption of oxygen and/or water on the MoS2 surface with a positive or negative gate bias, respectively, under an ambient environment. This study will be helpful in understanding the electrical-stress-induced instability of the MoS2-based electronic devices and will also give insight into the design of desirable devices for electronics applications.
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Affiliation(s)
- Kyungjune Cho
- Department of Physics and Astronomy, Seoul National University , Gwanak-ro, Gwanak-gu, Seoul 151-744, Korea
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450
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Lee GH, Yu YJ, Cui X, Petrone N, Lee CH, Choi MS, Lee DY, Lee C, Yoo WJ, Watanabe K, Taniguchi T, Nuckolls C, Kim P, Hone J. Flexible and transparent MoS2 field-effect transistors on hexagonal boron nitride-graphene heterostructures. ACS NANO 2013; 7:7931-6. [PMID: 23924287 DOI: 10.1021/nn402954e] [Citation(s) in RCA: 452] [Impact Index Per Article: 41.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/14/2023]
Abstract
Atomically thin forms of layered materials, such as conducting graphene, insulating hexagonal boron nitride (hBN), and semiconducting molybdenum disulfide (MoS2), have generated great interests recently due to the possibility of combining diverse atomic layers by mechanical "stacking" to create novel materials and devices. In this work, we demonstrate field-effect transistors (FETs) with MoS2 channels, hBN dielectric, and graphene gate electrodes. These devices show field-effect mobilities of up to 45 cm(2)/Vs and operating gate voltage below 10 V, with greatly reduced hysteresis. Taking advantage of the mechanical strength and flexibility of these materials, we demonstrate integration onto a polymer substrate to create flexible and transparent FETs that show unchanged performance up to 1.5% strain. These heterostructure devices consisting of ultrathin two-dimensional (2D) materials open up a new route toward high-performance flexible and transparent electronics.
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Affiliation(s)
- Gwan-Hyoung Lee
- Department of Mechanical Engineering, Columbia University , New York, New York 10027, United States
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