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Dhingra A. Layered GeI2: A wide-bandgap semiconductor for thermoelectric applications–A perspective. FRONTIERS IN NANOTECHNOLOGY 2022. [DOI: 10.3389/fnano.2022.1095291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Layered GeI2 is a two-dimensional wide-bandgap van der Waals semiconductor, which is theorized to be a promising material for thermoelectric applications. While the value of the experimentally extrapolated indirect optical bandgap of GeI2 is found to be consistent with the existing theoretical calculations, its potential as a thermoelectric material still lacks experimental validation. In this Perspective, recent experimental efforts aimed towards investigating its dynamical properties and tuning its bandgap further, via intercalation, are discussed. A thorough understanding of its dynamical properties elucidates the extent of electron-phonon scattering in this system, knowledge of which is crucial in order to open pathways for future studies aiming to realize GeI2-based thermoelectric devices.
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Dhingra A, Lipatov A, Loes MJ, Abourahma J, Pink M, Sinitskii A, Dowben PA. Effect of Au/HfS 3 interfacial interactions on properties of HfS 3-based devices. Phys Chem Chem Phys 2022; 24:14016-14021. [PMID: 35638717 DOI: 10.1039/d2cp01254e] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
X-ray photoemission spectroscopy (XPS) has been used to examine the interaction between Au and HfS3 at the Au/HfS3 interface. XPS measurements reveal dissociative chemisorption of O2, leading to the formation of an oxide of Hf at the surface of HfS3. This surface hafnium oxide, along with the weakly chemisorbed molecular species, such as O2 and H2O, are likely responsible for the observed p-type characteristics of HfS3 reported elsewhere. HfS3 devices exhibit n-type behaviour if measured in vacuum but turn p-type in air. Au thickness-dependent XPS measurements provide clear evidence of band bending as the S 2p and Hf 4f core-level peak binding energies for Au/HfS3 are found to be shifted to higher binding energies. This band bending implies formation of a Schottky-barrier at the Au/HfS3 interface, which explains the low measured charge carrier mobilities of HfS3-based devices. The transistor measurements presented herein also indicate the existence of a Schottky barrier, consistent with the XPS core-level binding energy shifts, and show that the bulk of HfS3 is n-type.
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Affiliation(s)
- Archit Dhingra
- Department of Physics and Astronomy, Theodore Jorgensen Hall, University of Nebraska-Lincoln, 855 N 16th Street, Lincoln, Nebraska 68588-0299, USA.
| | - Alexey Lipatov
- Department of Chemistry, Hamilton Hall, University of Nebraska-Lincoln, 639 North 12th Street, Lincoln, NE 68588-0304, USA.,Department of Chemistry, Biology & Health Sciences and Karen M. Swindler Department of Chemical and Biological Engineering, South Dakota School of Mines and Technology, 501 E. Saint Joseph St., Rapid City, SD 57701, USA
| | - Michael J Loes
- Department of Chemistry, Hamilton Hall, University of Nebraska-Lincoln, 639 North 12th Street, Lincoln, NE 68588-0304, USA
| | - Jehad Abourahma
- Department of Chemistry, Hamilton Hall, University of Nebraska-Lincoln, 639 North 12th Street, Lincoln, NE 68588-0304, USA
| | - Maren Pink
- Department of Chemistry, Indiana University, 800 E. Kirkwood Ave., Bloomington, IN 47405-7102, USA
| | - Alexander Sinitskii
- Department of Chemistry, Hamilton Hall, University of Nebraska-Lincoln, 639 North 12th Street, Lincoln, NE 68588-0304, USA
| | - Peter A Dowben
- Department of Physics and Astronomy, Theodore Jorgensen Hall, University of Nebraska-Lincoln, 855 N 16th Street, Lincoln, Nebraska 68588-0299, USA.
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3
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Ahmed T, Bellare P, Debnath R, Roy A, Ravishankar N, Ghosh A. Thermal History-Dependent Current Relaxation in hBN/MoS 2 van der Waals Dimers. ACS NANO 2020; 14:5909-5916. [PMID: 32310636 DOI: 10.1021/acsnano.0c01079] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Combining atomically thin layers of van der Waals (vdW) materials in a chosen vertical sequence is an emerging route to create devices with desired functionalities. While this method aims to exploit the individual properties of partnering layers, strong interlayer coupling can significantly alter their electronic and optical properties. Here we explored the impact of the vdW epitaxy on electrical transport in atomically thin molybdenum disulfide (MoS2) when it forms a vdW dimer with crystalline films of hexagonal boron nitride (hBN). We observe a thermal history-dependent long-term (over ∼40 h) current relaxation in the overlap region of MoS2/hBN heterostructures, which is absent in bare MoS2 layers (or homoepitaxial MoS2/MoS2 dimers) on the same substrate. Concurrent relaxation in the low-frequency Raman modes in MoS2 in the heterostructure region suggests a slow structural relaxation between trigonal and octahedral polymorphs of MoS2 as a likely driving mechanism that also results in inhomogeneous charge distribution in the MoS2 layer. Our experiment yields an aspect of vdW heteroepitaxy that can be generic to electrical devices with atomically thin transition-metal dichalcogenides.
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Affiliation(s)
- Tanweer Ahmed
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
| | - Pavithra Bellare
- Materials Research Centre, Indian Institute of Science, Bangalore 560012, India
| | - Rahul Debnath
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
| | - Ahin Roy
- Materials Research Centre, Indian Institute of Science, Bangalore 560012, India
| | | | - Arindam Ghosh
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
- Centre for Nano Science and Engineering, Indian Institute of Science, Bangalore 560012, India
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4
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Kang J. Phonon-Assisted Hopping through Defect States in MoS 2: A Multiscale Simulation. J Phys Chem Lett 2020; 11:3615-3622. [PMID: 32316728 DOI: 10.1021/acs.jpclett.0c00868] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Understanding the carrier transport mechanism in transition metal dichalcogenides (TMDs) is essential for their device application. Experiments demonstrated that at low carrier density and room temperature, the conductivity in TMDs is dominant by activation hopping transport through localized S-vacancy states. In this work, a multiscale model combining ab initio calculation and the Marcus theory is applied to study such transport. We identify phonon-assisted hopping (PAH) as the most possible mechanism for the activation hopping. It is found that the macroscopic conductivity is mainly contributed by a few microscopic percolation paths. Analysis on the hopping distance indicates nearest-neighbor hopping behavior. The dependence of PAH mobility on defect concentration, temperature, and energy mismatch between defect sites is discussed. It is shown that all these factors can strongly affect the mobility. We further proposed that alloying can be an efficient way to tune the mobility due to increased energy mismatch effect.
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Affiliation(s)
- Jun Kang
- Beijing Computational Science Research Center, Beijing 100193, China
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5
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Moon BH, Bae JJ, Han GH, Kim H, Choi H, Lee YH. Anomalous Conductance near Percolative Metal-Insulator Transition in Monolayer MoS 2 at Low Voltage Regime. ACS NANO 2019; 13:6631-6637. [PMID: 31122017 DOI: 10.1021/acsnano.9b00755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Conductivity of the insulating phase increases generally at an elevated drain-source voltage due to the field-enhanced hopping or heating effect. Meanwhile, a transport mechanism governed by percolation in a low compensated semiconductor gives rise to the reduced conductivity at a low-field regime. Here, in addition to this behavior, we report the anomalous conductivity behavior to transform from a percolative metallic to an insulating phase at the low voltage regime in monolayer molybdenum disulfide (MoS2). Percolation transport at low source-drain voltage is governed by inhomogeneously distributed potential in strongly interacting monolayer MoS2 with a substrate, distinct from the quantum phase transition in multilayer MoS2. At a high source-drain voltage regime, the insulating phase is transformed further to a metallic phase, exhibiting multiphases of metallic-insulating-metallic transitions in monolayer MoS2. These behaviors highlight MoS2 as a model system to study various classical and quantum transports as well as metal-insulator transition in two-dimensional systems.
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Affiliation(s)
- Byoung Hee Moon
- Center for Integrated Nanostructure Physics , Institute for Basic Science (IBS) , Suwon 16419 , Republic of Korea
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Jung Jun Bae
- WIT Co., Ltd. , 89, Seoho-ro, Gwonseon-gu , Suwon 16614 , Republic of Korea
| | - Gang Hee Han
- Center for Integrated Nanostructure Physics , Institute for Basic Science (IBS) , Suwon 16419 , Republic of Korea
| | - Hyun Kim
- Center for Integrated Nanostructure Physics , Institute for Basic Science (IBS) , Suwon 16419 , Republic of Korea
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Homin Choi
- Center for Integrated Nanostructure Physics , Institute for Basic Science (IBS) , Suwon 16419 , Republic of Korea
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
| | - Young Hee Lee
- Center for Integrated Nanostructure Physics , Institute for Basic Science (IBS) , Suwon 16419 , Republic of Korea
- Department of Energy Science , Sungkyunkwan University , Suwon 16419 , Republic of Korea
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Wu Z, Zhou BT, Cai X, Cheung P, Liu GB, Huang M, Lin J, Han T, An L, Wang Y, Xu S, Long G, Cheng C, Law KT, Zhang F, Wang N. Intrinsic valley Hall transport in atomically thin MoS 2. Nat Commun 2019; 10:611. [PMID: 30723283 PMCID: PMC6363770 DOI: 10.1038/s41467-019-08629-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Accepted: 01/23/2019] [Indexed: 11/25/2022] Open
Abstract
Electrons hopping in two-dimensional honeycomb lattices possess a valley degree of freedom in addition to charge and spin. In the absence of inversion symmetry, these systems were predicted to exhibit opposite Hall effects for electrons from different valleys. Such valley Hall effects have been achieved only by extrinsic means, such as substrate coupling, dual gating, and light illuminating. Here we report the first observation of intrinsic valley Hall transport without any extrinsic symmetry breaking in the non-centrosymmetric monolayer and trilayer MoS2, evidenced by considerable nonlocal resistance that scales cubically with local resistance. Such a hallmark survives even at room temperature with a valley diffusion length at micron scale. By contrast, no valley Hall signal is observed in the centrosymmetric bilayer MoS2. Our work elucidates the topological origin of valley Hall effects and marks a significant step towards the purely electrical control of valley degree of freedom in topological valleytronics. Electrons hopping in two-dimensional honeycomb lattices possess a valley degree of freedom. Here, the authors observe room-temperature valley Hall transport without any extrinsic symmetry breaking in the non-centrosymmetric monolayer and trilayer MoS2 by purely electronic means, whereas no valley signal is detected for centrosymmetric bilayer MoS2.
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Affiliation(s)
- Zefei Wu
- Department of Physics and the Center for Quantum Materials, the Hong Kong University of Science and Technology, Hong Kong, China.
| | - Benjamin T Zhou
- Department of Physics and the Center for Quantum Materials, the Hong Kong University of Science and Technology, Hong Kong, China
| | - Xiangbin Cai
- Department of Physics and the Center for Quantum Materials, the Hong Kong University of Science and Technology, Hong Kong, China
| | - Patrick Cheung
- Department of Physics, University of Texas at Dallas, Richardson, TX, 75080, USA
| | - Gui-Bin Liu
- School of Physics, Beijing Institute of Technology, 100081, Beijing, China
| | - Meizhen Huang
- Department of Physics and the Center for Quantum Materials, the Hong Kong University of Science and Technology, Hong Kong, China
| | - Jiangxiazi Lin
- Department of Physics and the Center for Quantum Materials, the Hong Kong University of Science and Technology, Hong Kong, China
| | - Tianyi Han
- Department of Physics and the Center for Quantum Materials, the Hong Kong University of Science and Technology, Hong Kong, China
| | - Liheng An
- Department of Physics and the Center for Quantum Materials, the Hong Kong University of Science and Technology, Hong Kong, China
| | - Yuanwei Wang
- Department of Physics and the Center for Quantum Materials, the Hong Kong University of Science and Technology, Hong Kong, China
| | - Shuigang Xu
- Department of Physics and the Center for Quantum Materials, the Hong Kong University of Science and Technology, Hong Kong, China
| | - Gen Long
- Department of Physics and the Center for Quantum Materials, the Hong Kong University of Science and Technology, Hong Kong, China
| | - Chun Cheng
- Department of Materials Science and Engineering, Southern University of Science and Technology, 518055, Shenzhen, China
| | - Kam Tuen Law
- Department of Physics and the Center for Quantum Materials, the Hong Kong University of Science and Technology, Hong Kong, China
| | - Fan Zhang
- Department of Physics, University of Texas at Dallas, Richardson, TX, 75080, USA.
| | - Ning Wang
- Department of Physics and the Center for Quantum Materials, the Hong Kong University of Science and Technology, Hong Kong, China.
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7
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Xue J, Huang S, Wang JY, Xu HQ. Mott variable-range hopping transport in a MoS2 nanoflake. RSC Adv 2019; 9:17885-17890. [PMID: 35520576 PMCID: PMC9064683 DOI: 10.1039/c9ra03150b] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2019] [Accepted: 05/28/2019] [Indexed: 11/21/2022] Open
Abstract
The transport characteristics of a disordered, multilayered MoS2 nanoflake in the insulator regime are studied by electrical and magnetotransport measurements. The MoS2 nanoflake is exfoliated from a bulk MoS2 crystal and the conductance G and magnetoresistance are measured in a four-probe setup over a wide range of temperatures. At high temperatures, we observe that ln G exhibits a −T−1 temperature dependence and the transport in the nanoflake dominantly arises from thermal activation. At low temperatures, where the transport in the nanoflake dominantly takes place via variable-range hopping (VRH) processes, we observe that ln G exhibits a −T−1/3 temperature dependence, an evidence for the two-dimensional (2D) Mott VRH transport. Furthermore, we observe that the measured low-field magnetoresistance of the nanoflake in the insulator regime exhibits a quadratic magnetic field dependence ∼ αB2 with α ∼ T−1, fully consistent with the 2D Mott VRH transport in the nanoflake. The transport characteristics of a disordered, multilayered MoS2 nanoflake in the insulator regime are studied by electrical and magnetotransport measurements.![]()
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Affiliation(s)
- Jianhong Xue
- Beijing Key Laboratory of Quantum Devices
- Key Laboratory for the Physics and Chemistry of Nanodevices
- Department of Electronics
- Peking University
- Beijing 100871
| | - Shaoyun Huang
- Beijing Key Laboratory of Quantum Devices
- Key Laboratory for the Physics and Chemistry of Nanodevices
- Department of Electronics
- Peking University
- Beijing 100871
| | - Ji-Yin Wang
- Beijing Key Laboratory of Quantum Devices
- Key Laboratory for the Physics and Chemistry of Nanodevices
- Department of Electronics
- Peking University
- Beijing 100871
| | - H. Q. Xu
- Beijing Key Laboratory of Quantum Devices
- Key Laboratory for the Physics and Chemistry of Nanodevices
- Department of Electronics
- Peking University
- Beijing 100871
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8
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Hsieh K, Kochat V, Zhang X, Gong Y, Tiwary CS, Ajayan PM, Ghosh A. Effect of Carrier Localization on Electrical Transport and Noise at Individual Grain Boundaries in Monolayer MoS 2. NANO LETTERS 2017; 17:5452-5457. [PMID: 28786685 DOI: 10.1021/acs.nanolett.7b02099] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Despite its importance in the large-scale synthesis of transition metal dichalcogenides (TMDC) molecular layers, the generic quantum effects on electrical transport across individual grain boundaries (GBs) in TMDC monolayers remain unclear. Here we demonstrate that strong carrier localization due to the increased density of defects determines both temperature dependence of electrical transport and low-frequency noise at the GBs of chemical vapor deposition (CVD)-grown MoS2 layers. Using field effect devices designed to explore transport across individual GBs, we show that the localization length of electrons in the GB region is ∼30-70% lower than that within the grain, even though the room temperature conductance across the GB, oriented perpendicular to the overall flow of current, may be lower or higher than the intragrain region. Remarkably, we find that the stronger localization is accompanied by nearly 5 orders of magnitude enhancement in the low-frequency noise at the GB region, which increases exponentially when the temperature is reduced. The microscopic framework of electrical transport and noise developed in this paper may be readily extended to other strongly localized two-dimensional systems, including other members of the TMDC family.
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Affiliation(s)
- Kimberly Hsieh
- Department of Physics, Indian Institute of Science , Bangalore 560012, India
| | - Vidya Kochat
- Department of Material Science and NanoEngineering, Rice University , Houston, Texas 77005, United States
| | - Xiang Zhang
- Department of Material Science and NanoEngineering, Rice University , Houston, Texas 77005, United States
| | - Yongji Gong
- Department of Material Science and NanoEngineering, Rice University , Houston, Texas 77005, United States
| | - Chandra Sekhar Tiwary
- Department of Material Science and NanoEngineering, Rice University , Houston, Texas 77005, United States
| | - Pulickel M Ajayan
- Department of Material Science and NanoEngineering, Rice University , Houston, Texas 77005, United States
| | - Arindam Ghosh
- Department of Physics, Indian Institute of Science , Bangalore 560012, India
- Centre for Nano Science and Engineering, Indian Institute of Science , Bangalore 560012, India
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9
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Kim TY, Song Y, Cho K, Amani M, Ho Ahn G, Kim JK, Pak J, Chung S, Javey A, Lee T. Analysis of the interface characteristics of CVD-grown monolayer MoS 2 by noise measurements. NANOTECHNOLOGY 2017; 28:145702. [PMID: 28276342 DOI: 10.1088/1361-6528/aa60f9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We investigated the current-voltage and noise characteristics of two-dimensional (2D) monolayer molybdenum disulfide (MoS2) synthesized by chemical vapor deposition (CVD). A large number of trap states were produced during the CVD process of synthesizing MoS2, resulting in a disordered monolayer MoS2 system. The interface trap density between CVD-grown MoS2 and silicon dioxide was extracted from the McWhorter surface noise model. Notably, generation-recombination noise which is attributed to charge trap states was observed at the low carrier density regime. The relation between the temperature and resistance following the power law of a 2D inverted-random void model supports the idea that disordered CVD-grown monolayer MoS2 can be analyzed using a percolation theory. This study can offer a viewpoint to interpret synthesized low-dimensional materials as highly disordered systems.
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Affiliation(s)
- Tae-Young Kim
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul 08826, Republic of Korea
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10
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Moon BH, Han GH, Kim H, Choi H, Bae JJ, Kim J, Jin Y, Jeong HY, Joo MK, Lee YH, Lim SC. Junction-Structure-Dependent Schottky Barrier Inhomogeneity and Device Ideality of Monolayer MoS 2 Field-Effect Transistors. ACS APPLIED MATERIALS & INTERFACES 2017; 9:11240-11246. [PMID: 28266221 DOI: 10.1021/acsami.6b16692] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Although monolayer transition metal dichalcogenides (TMDs) exhibit superior optical and electrical characteristics, their use in digital switching devices is limited by incomplete understanding of the metal contact. Comparative studies of Au top and edge contacts with monolayer MoS2 reveal a temperature-dependent ideality factor and Schottky barrier height (SBH). The latter originates from inhomogeneities in MoS2 caused by defects, charge puddles, and grain boundaries, which cause local variation in the work function at Au-MoS2 junctions and thus different activation temperatures for thermionic emission. However, the effect of inhomogeneities due to impurities on the SBH varies with the junction structure. The weak Au-MoS2 interaction in the top contact, which yields a higher SBH and ideality factor, is more affected by inhomogeneities than the strong interaction in the edge contact. Observed differences in the SBH and ideality factor in different junction structures clarify how the SBH and inhomogeneities can be controlled in devices containing TMD materials.
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Affiliation(s)
- Byoung Hee Moon
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
- Department of Energy Science, Sungkyunkwan University , Suwon 16419, Republic of Korea
| | - Gang Hee Han
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
| | - Hyun Kim
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
- Department of Energy Science, Sungkyunkwan University , Suwon 16419, Republic of Korea
| | - Homin Choi
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
- Department of Energy Science, Sungkyunkwan University , Suwon 16419, Republic of Korea
| | - Jung Jun Bae
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
| | - Jaesu Kim
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
- Department of Energy Science, Sungkyunkwan University , Suwon 16419, Republic of Korea
| | - Youngjo Jin
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
- Department of Energy Science, Sungkyunkwan University , Suwon 16419, Republic of Korea
| | - Hye Yun Jeong
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
| | - Min-Kyu Joo
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
| | - Young Hee Lee
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
- Department of Energy Science, Sungkyunkwan University , Suwon 16419, Republic of Korea
| | - Seong Chu Lim
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
- Department of Energy Science, Sungkyunkwan University , Suwon 16419, Republic of Korea
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11
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Prakash A, Cai Y, Zhang G, Zhang YW, Ang KW. Black Phosphorus N-Type Field-Effect Transistor with Ultrahigh Electron Mobility via Aluminum Adatoms Doping. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2017; 13. [PMID: 27862963 DOI: 10.1002/smll.201602909] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 10/03/2016] [Indexed: 05/11/2023]
Abstract
High-performance black phosphorus n-type field-effect transistors are realized using Al adatoms as effective electron donors, which achieved a record high mobility of >1495 cm2 V-1 s-1 at 260 K. The electron mobility is corroborated to charged-impurity scattering at low temperature, whilst metallic-like conduction is observed at high gate bias with increased carrier density due to enhanced electron-phonon interactions at high temperature.
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Affiliation(s)
- Amit Prakash
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, 117583, Singapore
| | - Yongqing Cai
- Institute of Higher Performance Computing, 1 Fusionopolis Way, 138632, Singapore
| | - Gang Zhang
- Institute of Higher Performance Computing, 1 Fusionopolis Way, 138632, Singapore
| | - Yong-Wei Zhang
- Institute of Higher Performance Computing, 1 Fusionopolis Way, 138632, Singapore
| | - Kah-Wee Ang
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, 117583, Singapore
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12
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Kim JS, Kim J, Zhao J, Kim S, Lee JH, Jin Y, Choi H, Moon BH, Bae JJ, Lee YH, Lim SC. Electrical Transport Properties of Polymorphic MoS2. ACS NANO 2016; 10:7500-7506. [PMID: 27399325 DOI: 10.1021/acsnano.6b02267] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The engineering of polymorphs in two-dimensional layered materials has recently attracted significant interest. Although the semiconducting (2H) and metallic (1T) phases are known to be stable in thin-film MoTe2, semiconducting 2H-MoS2 is locally converted into metallic 1T-MoS2 through chemical lithiation. In this paper, we describe the observation of the 2H, 1T, and 1T' phases coexisting in Li-treated MoS2, which result in unusual transport phenomena. Although multiphase MoS2 shows no transistor-gating response, the channel resistance decreases in proportion to the temperature, similar to the behavior of a typical semiconductor. Transmission electron microscopy images clearly show that the 1T and 1T' phases are randomly distributed and intervened with 2H-MoS2, which is referred to as the 1T and 1T' puddling phenomenon. The resistance curve fits well with 2D-variable range-hopping transport behavior, where electrons hop over 1T domains that are bounded by semiconducting 2H phases. However, near 30 K, electrons hop over charge puddles. The large temperature coefficient of resistance (TCR) of multiphase MoS2, -2.0 × 10(-2) K(-1) at 300 K, allows for efficient IR detection at room temperature by means of the photothermal effect.
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Affiliation(s)
- Jun Suk Kim
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
- Department of Energy Science, Sungkyunkwan University (SKKU) , Suwon 16419, Republic of Korea
| | - Jaesu Kim
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
- Department of Energy Science, Sungkyunkwan University (SKKU) , Suwon 16419, Republic of Korea
| | - Jiong Zhao
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
| | - Sungho Kim
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
| | - Jin Hee Lee
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
- Department of Energy Science, Sungkyunkwan University (SKKU) , Suwon 16419, Republic of Korea
| | - Youngjo Jin
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
- Department of Energy Science, Sungkyunkwan University (SKKU) , Suwon 16419, Republic of Korea
| | - Homin Choi
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
- Department of Energy Science, Sungkyunkwan University (SKKU) , Suwon 16419, Republic of Korea
| | - Byoung Hee Moon
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
| | - Jung Jun Bae
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
| | - Young Hee Lee
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
- Department of Energy Science, Sungkyunkwan University (SKKU) , Suwon 16419, Republic of Korea
| | - Seong Chu Lim
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
- Department of Energy Science, Sungkyunkwan University (SKKU) , Suwon 16419, Republic of Korea
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13
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Mondal B, Som A, Chakraborty I, Baksi A, Sarkar D, Pradeep T. Unusual reactivity of MoS2 nanosheets. NANOSCALE 2016; 8:10282-10290. [PMID: 27128579 DOI: 10.1039/c6nr00878j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The reactivity of the 2D nanosheets of MoS2 with silver ions in solution, leading to their spontaneous morphological and chemical transformations, is reported. This unique reactivity of the nanoscale form of MoS2 was in stark contrast to its bulk counterpart. While the gradual morphological transformation involving several steps has been captured with an electron microscope, precise chemical identification of the species involved was achieved by electron spectroscopy and mass spectrometry. The energetics of the system investigated supports the observed chemical transformation. The reaction with mercury and gold ions shows similar and dissimilar reaction products, respectively and points to the stability of the metal-sulphur bond in determining the chemical compositions of the final products.
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Affiliation(s)
- Biswajit Mondal
- DST Unit of Nanoscience (DST UNS) and Thematic Unit of Excellence (TUE), Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036, India.
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Qiu D, Lee DU, Park CS, Lee KS, Kim EK. Transport properties of unrestricted carriers in bridge-channel MoS2 field-effect transistors. NANOSCALE 2015; 7:17556-17562. [PMID: 26446693 DOI: 10.1039/c5nr04397b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Unsuppressed carrier scattering from the underlying substrate in a layered two-dimensional material system is extensively observed, which degrades significantly the performance of devices. Beyond the material itself, understanding the intrinsic interfacial and surficial properties is an important issue for the analysis of a high-κ/MoS2 heterostructure. Here, we report on the electronic transport properties of bridge-channel MoS2 field-effect transistors fabricated by a contamination-free transfer method. After neglecting all the surrounding perturbations, it is possible to reveal the significant improvement of room-temperature mobility and subthreshold slope. A systematic study on variable-temperature transport measurements has quantified the trap density of states both in free-standing and SiO2-supported MoS2 systems. Compared to the bridge-channel MoS2 devices with an ideal interface, the unsuspended devices have a large amount of band tail states, and then the impact of their electronic states on the device performance is also discussed.
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Affiliation(s)
- Dongri Qiu
- Quantum-Function Research Laboratory and Department of Physics, Hanyang University, Seoul 133-791, South Korea.
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Wu YC, Liu CH, Chen SY, Shih FY, Ho PH, Chen CW, Liang CT, Wang WH. Extrinsic Origin of Persistent Photoconductivity in Monolayer MoS2 Field Effect Transistors. Sci Rep 2015; 5:11472. [PMID: 26112341 PMCID: PMC4650635 DOI: 10.1038/srep11472] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Accepted: 05/18/2015] [Indexed: 12/03/2022] Open
Abstract
Recent discoveries of the photoresponse of molybdenum disulfide (MoS2) have shown the considerable potential of these two-dimensional transition metal dichalcogenides for optoelectronic applications. Among the various types of photoresponses of MoS2, persistent photoconductivity (PPC) at different levels has been reported. However, a detailed study of the PPC effect and its mechanism in MoS2 is still not available, despite the importance of this effect on the photoresponse of the material. Here, we present a systematic study of the PPC effect in monolayer MoS2 and conclude that the effect can be attributed to random localized potential fluctuations in the devices. Notably, the potential fluctuations originate from extrinsic sources based on the substrate effect of the PPC. Moreover, we point out a correlation between the PPC effect in MoS2 and the percolation transport behavior of MoS2. We demonstrate a unique and efficient means of controlling the PPC effect in monolayer MoS2, which may offer novel functionalities for MoS2-based optoelectronic applications in the future.
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Affiliation(s)
- Yueh-Chun Wu
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan
| | - Cheng-Hua Liu
- 1] Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan [2] Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Shao-Yu Chen
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan
| | - Fu-Yu Shih
- 1] Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan [2] Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Po-Hsun Ho
- Department of Materials Science and Engineering, National Taiwan University, Taipei 106, Taiwan
| | - Chun-Wei Chen
- Department of Materials Science and Engineering, National Taiwan University, Taipei 106, Taiwan
| | - Chi-Te Liang
- Department of Physics, National Taiwan University, Taipei 106, Taiwan
| | - Wei-Hua Wang
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan
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