1
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Chen D, Anantharaman SB, Wu J, Qiu DY, Jariwala D, Guo P. Optical spectroscopic detection of Schottky barrier height at a two-dimensional transition-metal dichalcogenide/metal interface. NANOSCALE 2024; 16:5169-5176. [PMID: 38390639 DOI: 10.1039/d3nr05799b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/24/2024]
Abstract
Atomically thin two-dimensional transition-metal dichalcogenides (2D-TMDs) have emerged as semiconductors for next-generation nanoelectronics. As 2D-TMD-based devices typically utilize metals as the contacts, it is crucial to understand the properties of the 2D-TMD/metal interface, including the characteristics of the Schottky barriers formed at the semiconductor-metal junction. Conventional methods for investigating the Schottky barrier height (SBH) at these interfaces predominantly rely on contact-based electrical measurements with complex gating structures. In this study, we introduce an all-optical approach for non-contact measurement of the SBH, utilizing high-quality WS2/Au heterostructures as a model system. Our approach employs a below-bandgap pump to excite hot carriers from the gold into WS2 with varying thicknesses. By monitoring the resultant carrier density changes within the WS2 layers with a broadband probe, we traced the dynamics and magnitude of charge transfer across the interface. A systematic sweep of the pump wavelength enables us to determine the SBH values and unveil an inverse relationship between the SBH and the thickness of the WS2 layers. First-principles calculations reveal the correlation between the probability of injection and the density of states near the conduction band minimum of WS2. The versatile optical methodology for probing TMD/metal interfaces can shed light on the intricate charge transfer characteristics within various 2D heterostructures, facilitating the development of more efficient and scalable nano-electronic and optoelectronic technologies.
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Affiliation(s)
- Du Chen
- Department of Chemical and Environmental Engineering, Yale University, New Haven, CT 06520, USA.
- Energy Sciences Institute, Yale University, West Haven, CT 06516, USA
| | - Surendra B Anantharaman
- Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Jinyuan Wu
- Energy Sciences Institute, Yale University, West Haven, CT 06516, USA
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT 06520, USA
| | - Diana Y Qiu
- Energy Sciences Institute, Yale University, West Haven, CT 06516, USA
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT 06520, USA
| | - Deep Jariwala
- Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Peijun Guo
- Department of Chemical and Environmental Engineering, Yale University, New Haven, CT 06520, USA.
- Energy Sciences Institute, Yale University, West Haven, CT 06516, USA
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2
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Dutta S, Husain S, Kumar P, Gupta NK, Chaudhary S, Svedlindh P, Barman A. Manipulating ultrafast magnetization dynamics of ferromagnets using the odd-even layer dependence of two-dimensional transition metal di-chalcogenides. NANOSCALE 2024; 16:4105-4113. [PMID: 38349614 DOI: 10.1039/d3nr06197c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
Two-dimensional transition metal dichalcogenides (TMDs) have drawn immense interest due to their strong spin-orbit coupling and unique layer number dependence in response to spin-valley coupling. This leads to the possibility of controlling the spin degree of freedom of the ferromagnet (FM) in thin film heterostructures and may prove to be of interest for next-generation spin-based devices. Here, we experimentally demonstrate the odd-even layer dependence of WS2 nanolayers by measurements of the ultrafast magnetization dynamics in WS2/Co3FeB thin film heterostructures by using time-resolved Kerr magnetometry. The fluence (photon energy per unit area) dependent magnetic damping (α) reveals the existence of broken symmetry and the dominance of inter- and intraband scattering for odd and even layers of WS2, respectively. The higher demagnetization time, τm, in 3 and 5 layers of WS2 is indicative of the interaction between spin-orbit and spin-valley coupling due to the broken symmetry. The lower τm in even layers as compared to the bare FM layer suggests the presence of a spin transport. By correlating τm and α, we pinpointed the dominant mechanisms of ultrafast demagnetization. The mechanism changes from spin transport to spin-flip scattering for even layers of WS2 with increasing fluence. A fundamental understanding of the two-dimensional material and its odd-even layer dependence at ultrashort timescales provides valuable information for designing next-generation spin-based devices.
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Affiliation(s)
- Soma Dutta
- Department of Condensed Matter and Materials Physics, S. N. Bose National Centre for Basic Sciences, Block JD, Sector-III, Salt Lake, Kolkata 700 106, India.
| | - Sajid Husain
- Department of Materials Science and Engineering, Uppsala University, Box 35, SE-751 03 Uppsala, Sweden.
| | - Prabhat Kumar
- Department of Thin Films and Nanostructures, Institute of Physics of the Czech Academy of Sciences, Cukrovarnická 10/112, 162 00 Prague, Czech Republic
| | - Nanhe Kumar Gupta
- Thin Film Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
| | - Sujeet Chaudhary
- Thin Film Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
| | - Peter Svedlindh
- Department of Materials Science and Engineering, Uppsala University, Box 35, SE-751 03 Uppsala, Sweden.
| | - Anjan Barman
- Department of Condensed Matter and Materials Physics, S. N. Bose National Centre for Basic Sciences, Block JD, Sector-III, Salt Lake, Kolkata 700 106, India.
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3
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Shanmugam A, Thekke Purayil MA, Dhurjati SA, Thalakulam M. Physical vapor deposition-free scalable high-efficiency electrical contacts to MoS 2. NANOTECHNOLOGY 2023; 35:115201. [PMID: 38055966 DOI: 10.1088/1361-6528/ad12e4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Accepted: 12/05/2023] [Indexed: 12/08/2023]
Abstract
Fermi-level pinning caused by the kinetic damage during metallization has been recognized as one of the major reasons for the non-ideal behavior of electrical contacts, forbidding reaching the Schottky-Mott limit. In this manuscript, we present a scalable technique wherein Indium, a low-work-function metal, is diffused to contact a few-layered MoS2flake. The technique exploits a smooth outflow of Indium over gold electrodes to make edge contacts to pre-transferred MoS2flakes. We compare the performance of three pairs of contacts made onto the same MoS2flake, the bottom-gold, top-gold, and Indium contacts, and find that the Indium contacts are superior to other contacts. The Indium contacts maintain linearI-Vcharacteristics down to cryogenic temperatures with an extracted Schottky barrier height of ∼2.1 meV. First-principle calculations show the induced in-gap states close to the Fermi level, and the damage-free contact interface could be the reason for the nearly Ohmic behavior of the Indium/MoS2interface.
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Affiliation(s)
- Anusha Shanmugam
- Indian Institute of Science Education & Research Thiruvananthapuram, Kerala 695551, India
| | | | | | - Madhu Thalakulam
- Indian Institute of Science Education & Research Thiruvananthapuram, Kerala 695551, India
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4
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Ding EX, Liu P, Yoon HH, Ahmed F, Du M, Shafi AM, Mehmood N, Kauppinen EI, Sun Z, Lipsanen H. Highly Sensitive MoS 2 Photodetectors Enabled with a Dry-Transferred Transparent Carbon Nanotube Electrode. ACS APPLIED MATERIALS & INTERFACES 2023; 15:4216-4225. [PMID: 36635093 PMCID: PMC9880956 DOI: 10.1021/acsami.2c19917] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/05/2022] [Accepted: 01/05/2023] [Indexed: 06/17/2023]
Abstract
Fabricating electronic and optoelectronic devices by transferring pre-deposited metal electrodes has attracted considerable attention, owing to the improved device performance. However, the pre-deposited metal electrode typically involves complex fabrication procedures. Here, we introduce our facile electrode fabrication process which is free of lithography, lift-off, and reactive ion etching by directly press-transferring a single-walled carbon nanotube (SWCNT) film. We fabricated Schottky diodes for photodetector applications using dry-transferred SWCNT films as the transparent electrode to increase light absorption in photoactive MoS2 channels. The MoS2 flake vertically stacked with an SWCNT electrode can exhibit excellent photodetection performance with a responsivity of ∼2.01 × 103 A/W and a detectivity of ∼3.2 × 1012 Jones. Additionally, we carried out temperature-dependent current-voltage measurement and Fowler-Nordheim (FN) plot analysis to explore the dominant charge transport mechanism. The enhanced photodetection in the vertical configuration is found to be attributed to the FN tunneling and internal photoemission of charge carriers excited from indium tin oxide across the MoS2 layer. Our study provides a novel concept of using a photoactive MoS2 layer as a tunneling layer itself with a dry-transferred transparent SWCNT electrode for high-performance and energy-efficient optoelectronic devices.
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Affiliation(s)
- Er-Xiong Ding
- Department
of Electronics and Nanoengineering, School of Electrical Engineering, Aalto University, EspooFI-02150, Finland
| | - Peng Liu
- Department
of Electronics and Nanoengineering, School of Electrical Engineering, Aalto University, EspooFI-02150, Finland
- Department
of Applied Physics, School of Science, Aalto
University, EspooFI-02150, Finland
| | - Hoon Hahn Yoon
- Department
of Electronics and Nanoengineering, School of Electrical Engineering, Aalto University, EspooFI-02150, Finland
| | - Faisal Ahmed
- Department
of Electronics and Nanoengineering, School of Electrical Engineering, Aalto University, EspooFI-02150, Finland
| | - Mingde Du
- Department
of Electronics and Nanoengineering, School of Electrical Engineering, Aalto University, EspooFI-02150, Finland
| | - Abde Mayeen Shafi
- Department
of Electronics and Nanoengineering, School of Electrical Engineering, Aalto University, EspooFI-02150, Finland
| | - Naveed Mehmood
- Department
of Electronics and Nanoengineering, School of Electrical Engineering, Aalto University, EspooFI-02150, Finland
| | - Esko I. Kauppinen
- Department
of Applied Physics, School of Science, Aalto
University, EspooFI-02150, Finland
| | - Zhipei Sun
- Department
of Electronics and Nanoengineering, School of Electrical Engineering, Aalto University, EspooFI-02150, Finland
| | - Harri Lipsanen
- Department
of Electronics and Nanoengineering, School of Electrical Engineering, Aalto University, EspooFI-02150, Finland
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5
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Sun Y, Jiang L, Wang Z, Hou Z, Dai L, Wang Y, Zhao J, Xie YH, Zhao L, Jiang Z, Ren W, Niu G. Multiwavelength High-Detectivity MoS 2 Photodetectors with Schottky Contacts. ACS NANO 2022; 16:20272-20280. [PMID: 36508482 DOI: 10.1021/acsnano.2c06062] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Photodetection is one of the vital functions for the multifunctional "More than Moore" (MtM) microchips urgently required by Internet of Things (IoT) and artificial intelligence (AI) applications. The further improvement of the performance of photodetectors faces various challenges, including materials, fabrication processes, and device structures. We demonstrate in this work MoS2 photodetectors with a nanoscale channel length and a back-gate device structure. With the mechanically exfoliated six-monolayer-thick MoS2, a Schottky contact between source/drain electrodes and MoS2, a high responsivity of 4.1 × 103 A W-1, and a detectivity of 1.34 × 1013 cm Hz1/2 W-1 at 650 nm were achieved. The devices are also sensitive to multiwavelength lights, including 520 and 405 nm. The electrical and optoelectronic properties of the MoS2 photodetectors were studied in depth, and the working mechanism of the devices was analyzed. The photoinduced Schottky barrier lowering (PIBL) was found to be important for the high performance of the phototransistor.
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Affiliation(s)
- Yanxiao Sun
- Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, School of Electronic Science and Engineering & The International Joint Laboratory for Micro/Nano Manufacturing and Measurement Technology, Xi'an Jiaotong University, Xi'an710049, People's Republic of China
| | - Luyue Jiang
- Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, School of Electronic Science and Engineering & The International Joint Laboratory for Micro/Nano Manufacturing and Measurement Technology, Xi'an Jiaotong University, Xi'an710049, People's Republic of China
| | - Zhe Wang
- Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, School of Electronic Science and Engineering & The International Joint Laboratory for Micro/Nano Manufacturing and Measurement Technology, Xi'an Jiaotong University, Xi'an710049, People's Republic of China
| | - Zhenfei Hou
- Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, School of Electronic Science and Engineering & The International Joint Laboratory for Micro/Nano Manufacturing and Measurement Technology, Xi'an Jiaotong University, Xi'an710049, People's Republic of China
| | - Liyan Dai
- Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, School of Electronic Science and Engineering & The International Joint Laboratory for Micro/Nano Manufacturing and Measurement Technology, Xi'an Jiaotong University, Xi'an710049, People's Republic of China
| | - Yankun Wang
- Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, School of Electronic Science and Engineering & The International Joint Laboratory for Micro/Nano Manufacturing and Measurement Technology, Xi'an Jiaotong University, Xi'an710049, People's Republic of China
| | - Jinyan Zhao
- Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, School of Electronic Science and Engineering & The International Joint Laboratory for Micro/Nano Manufacturing and Measurement Technology, Xi'an Jiaotong University, Xi'an710049, People's Republic of China
| | - Ya-Hong Xie
- Department of Materials Science and Engineering, University of California, Los Angeles, Los AngelesCalifornia90024, United States
| | - Libo Zhao
- The State Key Laboratory for Manufacturing Systems Engineering & The International Joint Laboratory for Micro/Nano Manufacturing and Measurement Technology, Xi'an Jiaotong University, Xi'an710049, People's Republic of China
| | - Zhuangde Jiang
- The State Key Laboratory for Manufacturing Systems Engineering & The International Joint Laboratory for Micro/Nano Manufacturing and Measurement Technology, Xi'an Jiaotong University, Xi'an710049, People's Republic of China
| | - Wei Ren
- Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, School of Electronic Science and Engineering & The International Joint Laboratory for Micro/Nano Manufacturing and Measurement Technology, Xi'an Jiaotong University, Xi'an710049, People's Republic of China
| | - Gang Niu
- Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, School of Electronic Science and Engineering & The International Joint Laboratory for Micro/Nano Manufacturing and Measurement Technology, Xi'an Jiaotong University, Xi'an710049, People's Republic of China
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6
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Huang TX, Yang M, Giang H, Dong B, Fang N. Resolving the Heterogeneous Adsorption of Antibody Fragment on a 2D Layered Molybdenum Disulfide by Super-Resolution Imaging. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:7455-7461. [PMID: 35676767 DOI: 10.1021/acs.langmuir.2c00420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The development of nanomaterials such as two-dimensional (2D) layered materials advanced applications in many fields, including biosensors format based on field-effect transistors. The unique physical and chemical properties of 2D layered materials enable the detection limit of biomolecules as low as ∼1 pg/mL. The majority of 2D layered materials contain different structural features and defects introduced in chemical synthesis and fabrication processing. These structural features have different physicochemical properties, causing heterogeneous adsorption of bioreceptors like antibodies, enzymes, etc. Understanding the correlation between the adsorption of bioreceptors and properties of structural features is essential for building highly efficient, sensitive biosensors based on 2D layered materials. Here, we utilize a single-molecule localization-based super-resolved fluorescence imaging method to unveil the inhomogeneous adsorption of antibody fragments on 2D layered molybdenum disulfide (MoS2). The surface coverage of antibody fragments on MoS2 thin flakes is quantitatively measured and compared at different structural features and different layer thicknesses. The methodology in the current work can be extended to study bioreceptor adsorption on other types of 2D layered materials and pave a way to improve biosensors' sensitivity based on defect engineering 2D layered materials.
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Affiliation(s)
- Teng-Xiang Huang
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30303, United States
| | - Meek Yang
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, United States
| | - Hannah Giang
- Department of Chemistry, Southern Illinois University Carbondale, Carbondale, Illinois 62901, United Stated
| | - Bin Dong
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, United States
| | - Ning Fang
- Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), The MOE Key Laboratory of Spectrochemical Analysis and Instrumentation, State Key Laboratory of Physical Chemistry of Solid Surfaces, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
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7
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Köster J, Storm A, Gorelik TE, Mohn MJ, Port F, Gonçalves MR, Kaiser U. Evaluation of TEM methods for their signature of the number of layers in mono- and few-layer TMDs as exemplified by MoS2 and MoTe2. Micron 2022; 160:103303. [DOI: 10.1016/j.micron.2022.103303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 05/23/2022] [Accepted: 05/26/2022] [Indexed: 11/16/2022]
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8
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Chen L, Wang W, Lin Z, Lu Y, Chen H, Li B, Li Z, Xia H, Li L, Zhang T. Conducting molybdenum sulfide/graphene oxide/polyvinyl alcohol nanocomposite hydrogel for repairing spinal cord injury. J Nanobiotechnology 2022; 20:210. [PMID: 35524268 PMCID: PMC9074236 DOI: 10.1186/s12951-022-01396-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Accepted: 03/23/2022] [Indexed: 11/10/2022] Open
Abstract
A sort of composite hydrogel with good biocompatibility, suppleness, high conductivity, and anti-inflammatory activity based on polyvinyl alcohol (PVA) and molybdenum sulfide/graphene oxide (MoS2/GO) nanomaterial has been developed for spinal cord injury (SCI) restoration. The developed (MoS2/GO/PVA) hydrogel exhibits excellent mechanical properties, outstanding electronic conductivity, and inflammation attenuation activity. It can promote neural stem cells into neurons differentiation as well as inhibit the astrocytes development in vitro. In addition, the composite hydrogel shows a high anti-inflammatory effect. After implantation of the composite hydrogel in mice, it could activate the endogenous regeneration of the spinal cord and inhibit the activation of glial cells in the injured area, thus resulting in the recovery of locomotor function. Overall, our work provides a new sort of hydrogels for SCI reparation, which shows great promise for improving the dilemma in SCI therapy.
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Affiliation(s)
- Lingling Chen
- Guangdong Key Lab of Orthopedic Technology and Implant Materials, Key Laboratory of Trauma & Tissue Repair of Tropical Area of PLA, Orthopedic Center, General Hospital of Southern Theater Command of PLA, Guangzhou, 510010, Guangdong, China
| | - Wanshun Wang
- Guangdong Key Lab of Orthopedic Technology and Implant Materials, Key Laboratory of Trauma & Tissue Repair of Tropical Area of PLA, Orthopedic Center, General Hospital of Southern Theater Command of PLA, Guangzhou, 510010, Guangdong, China.,The Second Clinical Medical College, Guangzhou University of Chinese Medicine, Guangzhou, 510405, Guangdong, China
| | - Zefeng Lin
- Guangdong Key Lab of Orthopedic Technology and Implant Materials, Key Laboratory of Trauma & Tissue Repair of Tropical Area of PLA, Orthopedic Center, General Hospital of Southern Theater Command of PLA, Guangzhou, 510010, Guangdong, China
| | - Yao Lu
- Southern Medical University, 1023 South Shatai Road, Guangzhou, 510515, Guangdong, China.,Department of Orthopedics, Clinical Research Centre, Zhujiang Hospital, Southern Medical University, 253 Gongye Road, Guangzhou, 510282, Guangdong, China
| | - Hu Chen
- Guangdong Key Lab of Orthopedic Technology and Implant Materials, Key Laboratory of Trauma & Tissue Repair of Tropical Area of PLA, Orthopedic Center, General Hospital of Southern Theater Command of PLA, Guangzhou, 510010, Guangdong, China.,Southern Medical University, 1023 South Shatai Road, Guangzhou, 510515, Guangdong, China
| | - Binglin Li
- Guangdong Key Lab of Orthopedic Technology and Implant Materials, Key Laboratory of Trauma & Tissue Repair of Tropical Area of PLA, Orthopedic Center, General Hospital of Southern Theater Command of PLA, Guangzhou, 510010, Guangdong, China
| | - Zhan Li
- Guangdong Key Lab of Orthopedic Technology and Implant Materials, Key Laboratory of Trauma & Tissue Repair of Tropical Area of PLA, Orthopedic Center, General Hospital of Southern Theater Command of PLA, Guangzhou, 510010, Guangdong, China
| | - Hong Xia
- Guangdong Key Lab of Orthopedic Technology and Implant Materials, Key Laboratory of Trauma & Tissue Repair of Tropical Area of PLA, Orthopedic Center, General Hospital of Southern Theater Command of PLA, Guangzhou, 510010, Guangdong, China. .,Southern Medical University, 1023 South Shatai Road, Guangzhou, 510515, Guangdong, China.
| | - Lihua Li
- Department of Applied Physics, The Hong Kong Polytechnic University, Kowloon, 999077, Hong Kong, China.
| | - Tao Zhang
- Guangdong Key Lab of Orthopedic Technology and Implant Materials, Key Laboratory of Trauma & Tissue Repair of Tropical Area of PLA, Orthopedic Center, General Hospital of Southern Theater Command of PLA, Guangzhou, 510010, Guangdong, China. .,Southern Medical University, 1023 South Shatai Road, Guangzhou, 510515, Guangdong, China.
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9
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Temperature- and light-dependent photoconductivity studies of thermally evaporated WTe2 thin film for photodetection application. APPLIED NANOSCIENCE 2022. [DOI: 10.1007/s13204-021-02076-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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10
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Brunet Cabré M, Paiva AE, Velický M, Colavita PE, McKelvey K. Electrochemical kinetics as a function of transition metal dichalcogenide thickness. Electrochim Acta 2021. [DOI: 10.1016/j.electacta.2021.139027] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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11
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Kidd TE, Weber J, O'Leary E, Stollenwerk AJ. Preparation of Ultrathin Gold Films with Subatomic Surface Roughness. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:9472-9477. [PMID: 34310876 DOI: 10.1021/acs.langmuir.1c01203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Nanoscale device fabrication requires control over film growth at the atomic scale. Growth conditions must be tuned in consideration of interface parameters like chemical bonding, surface free energy, and lattice matching. In metals, electronic properties may also be utilized for control of physical parameters. Quantum size effects can induce metals to spontaneously form specific shapes and sizes according to their electronic structure. Unfortunately, such electronic growth is generally known only for a few systems and is typically only stable under cryogenic conditions. In this work, we explore a recently discovered class of electronic growth systems in which metal films are grown upon the relatively inert surfaces of van der Waals crystals. In this class of materials, the electronic growth is highly stable at room temperature and actually requires higher temperature annealing to achieve proper equilibrium. We work with the Au/MoS2 system, which shows excellent stability and can readily form discrete and atomically flat nanostructures. Here, we show how the electronic growth modes facilitate the formation of atomically flat films with nanometer scale thickness. The surface roughness of these films was found to be less than a single atom over several square microns, creating nearly perfect surfaces for studies of self-assembled monolayers or other applications.
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Affiliation(s)
- Timothy E Kidd
- Department of Physics, University of Northern Iowa, Cedar Falls, Iowa 50614, United States
| | - Jacob Weber
- Department of Physics, University of Northern Iowa, Cedar Falls, Iowa 50614, United States
| | - Evan O'Leary
- Department of Physics, University of Northern Iowa, Cedar Falls, Iowa 50614, United States
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12
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Panasci S, Schilirò E, Greco G, Cannas M, Gelardi FM, Agnello S, Roccaforte F, Giannazzo F. Strain, Doping, and Electronic Transport of Large Area Monolayer MoS 2 Exfoliated on Gold and Transferred to an Insulating Substrate. ACS APPLIED MATERIALS & INTERFACES 2021; 13:31248-31259. [PMID: 34165956 PMCID: PMC9280715 DOI: 10.1021/acsami.1c05185] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Gold-assisted mechanical exfoliation currently represents a promising method to separate ultralarge (centimeter scale) transition metal dichalcogenide (TMD) monolayers (1L) with excellent electronic and optical properties from the parent van der Waals (vdW) crystals. The strong interaction between Au and chalcogen atoms is key to achieving this nearly perfect 1L exfoliation yield. On the other hand, it may significantly affect the doping and strain of 1L TMDs in contact with Au. In this paper, we systematically investigated the morphology, strain, doping, and electrical properties of large area 1L MoS2 exfoliated on ultraflat Au films (0.16-0.21 nm roughness) and finally transferred to an insulating Al2O3 substrate. Raman mapping and correlative analysis of the E' and A1' peak positions revealed a moderate tensile strain (ε ≈ 0.2%) and p-type doping (n ≈ -0.25 × 1013 cm-2) of 1L MoS2 in contact with Au. Nanoscale resolution current mapping and current-voltage (I-V) measurements by conductive atomic force microscopy (C-AFM) showed direct tunneling across the 1L MoS2 on Au, with a broad distribution of tunneling barrier values (ΦB from 0.7 to 1.7 eV) consistent with p-type doping of MoS2. After the final transfer of 1L MoS2 on Al2O3/Si, the strain was converted to compressive strain (ε ≈ -0.25%). Furthermore, an n-type doping (n ≈ 0.5 × 1013 cm-2) was deduced by Raman mapping and confirmed by electrical measurements of an Al2O3/Si back-gated 1L MoS2 transistor. These results provide a deeper understanding of the Au-assisted exfoliation mechanism and can contribute to its widespread application for the realization of novel devices and artificial vdW heterostructures.
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Affiliation(s)
- Salvatore
Ethan Panasci
- CNR-IMM, Strada VIII, 5 95121, Catania, Italy
- Department
of Physics and Astronomy, University of
Catania, Via Santa Sofia
64, 95123 Catania, Italy
| | | | | | - Marco Cannas
- Department
of Physics and Chemistry Emilio Segrè, University of Palermo, Via Archirafi 36, 90123 Palermo, Italy
| | - Franco M. Gelardi
- Department
of Physics and Chemistry Emilio Segrè, University of Palermo, Via Archirafi 36, 90123 Palermo, Italy
| | - Simonpietro Agnello
- CNR-IMM, Strada VIII, 5 95121, Catania, Italy
- Department
of Physics and Chemistry Emilio Segrè, University of Palermo, Via Archirafi 36, 90123 Palermo, Italy
- ATeN
Center, Università degli Studi di
Palermo, Viale delle
Scienze, Edificio 18, 90128 Palermo, Italy
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13
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Pollmann E, Sleziona S, Foller T, Hagemann U, Gorynski C, Petri O, Madauß L, Breuer L, Schleberger M. Large-Area, Two-Dimensional MoS 2 Exfoliated on Gold: Direct Experimental Access to the Metal-Semiconductor Interface. ACS OMEGA 2021; 6:15929-15939. [PMID: 34179637 PMCID: PMC8223410 DOI: 10.1021/acsomega.1c01570] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 05/06/2021] [Indexed: 06/13/2023]
Abstract
Two-dimensional semiconductors such as MoS2 are promising for future electrical devices. The interface to metals is a crucial and critical aspect for these devices because undesirably high resistances due to Fermi level pinning are present, resulting in unwanted energy losses. To date, experimental information on such junctions has been obtained mainly indirectly by evaluating transistor characteristics. The fact that the metal-semiconductor interface is typically embedded, further complicates the investigation of the underlying physical mechanisms at the interface. Here, we present a method to provide access to a realistic metal-semiconductor interface by large-area exfoliation of single-layer MoS2 on clean polycrystalline gold surfaces. This approach allows us to measure the relative charge neutrality level at the MoS2-gold interface and its spatial variation almost directly using Kelvin probe force microscopy even under ambient conditions. By bringing together hitherto unconnected findings about the MoS2-gold interface, we can explain the anomalous Raman signature of MoS2 in contact to metals [ACS Nano. 7, 2013, 11350] which has been the subject of intense recent discussions. In detail, we identify the unusual Raman mode as the A1g mode with a reduced Raman shift (397 cm-1) due to the weakening of the Mo-S bond. Combined with our X-ray photoelectron spectroscopy data and the measured charge neutrality level, this is in good agreement with a previously predicted mechanism for Fermi level pinning at the MoS2-gold interface [Nano Lett. 14, 2014, 1714]. As a consequence, the strength of the MoS2-gold contact can be determined from the intensity ratio between the reduced A1greduced mode and the unperturbed A1g mode.
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Affiliation(s)
- Erik Pollmann
- Faculty
of Physics and CENIDE, University of Duisburg-Essen, D-47057 Duisburg, Germany
| | - Stephan Sleziona
- Faculty
of Physics and CENIDE, University of Duisburg-Essen, D-47057 Duisburg, Germany
| | - Tobias Foller
- Faculty
of Physics and CENIDE, University of Duisburg-Essen, D-47057 Duisburg, Germany
| | - Ulrich Hagemann
- ICAN
and CENIDE, University of Duisburg-Essen, D-47057 Duisburg, Germany
| | - Claudia Gorynski
- Faculty
of Engineering and CENIDE, University Duisburg-Essen, D-47057 Duisburg, Germany
| | - Oliver Petri
- Faculty
of Physics and CENIDE, University of Duisburg-Essen, D-47057 Duisburg, Germany
| | - Lukas Madauß
- Faculty
of Physics and CENIDE, University of Duisburg-Essen, D-47057 Duisburg, Germany
| | - Lars Breuer
- Faculty
of Physics and CENIDE, University of Duisburg-Essen, D-47057 Duisburg, Germany
| | - Marika Schleberger
- Faculty
of Physics and CENIDE, University of Duisburg-Essen, D-47057 Duisburg, Germany
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14
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Improved Photoelectrochemical Performance of MoS 2 through Morphology-Controlled Chemical Vapor Deposition Growth on Graphene. NANOMATERIALS 2021; 11:nano11061585. [PMID: 34204208 PMCID: PMC8235607 DOI: 10.3390/nano11061585] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 06/13/2021] [Accepted: 06/15/2021] [Indexed: 01/03/2023]
Abstract
The morphology of MoS2 nanostructures was manipulated from thin films to vertically aligned few-layer nanosheets on graphene, in a controllable and practical manner, using metalorganic chemical vapor deposition. The effects of graphene layer and MoS2 morphology on photoelectrochemical (PEC) performance were systematically studied on the basis of electronic structure and transitions, carrier dynamic behavior, and PEC measurements. The heterojunction quality of the graphene/vertical few-layer MoS2 nanosheets was ensured by low-temperature growth at 250−300 °C, resulting in significantly improved charge transfer properties. As a result, the PEC photocurrent density and photoconversion efficiency of the few-layer MoS2 nanosheets significantly increased upon the insertion of a graphene layer. Among the graphene/MoS2 samples, the few-layer MoS2 nanosheet samples exhibited shorter carrier lifetimes and smaller charge transfer resistances than the thin film samples, suggesting that vertically aligned nanosheets provide highly conductive edges as an efficient pathway for photo-generated carriers and have better electronic contact with graphene. In addition, the height of vertical MoS2 nanosheets on graphene should be controlled within the carrier diffusion length (~200 nm) to achieve the optimal PEC performance. These results can be utilized effectively to exploit the full potential of two-dimensional MoS2 for various PEC applications.
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15
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Shen H, Ren J, Li J, Chen Y, Lan S, Wang J, Wang H, Li D. Multistate Memory Enabled by Interface Engineering Based on Multilayer Tungsten Diselenide. ACS APPLIED MATERIALS & INTERFACES 2020; 12:58428-58434. [PMID: 33332079 DOI: 10.1021/acsami.0c19443] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The diversification of data types and the explosive increase of data size in the information era continuously required to miniaturize the memory devices with high data storage capability. Atomically thin two-dimensional (2D) transition metal dichalcogenides (TMDs) are promising candidates for flexible and transparent electronic and optoelectronic devices with high integration density. Multistate memory devices based on TMDs could possess high data storage capability with a large integration density and thus exhibit great potential applications in the field of data storage. Here, we report the multistate data storage based on multilayer tungsten diselenide (WSe2) transistors by interface engineering. The multiple resistance states of the WSe2 transistors are achieved by applying different gate voltage pulses, and the switching ratio of the memory can be as large as 105 with high cycling endurance. The water and oxygen molecules (H2O/O2) trapped at the interface between the SiO2 substrate and WSe2 introduce the trap states and thus the large hysteresis of the transfer curves, which leads to the multistate data storage. In addition, the laminated Au thin film electrodes make the contact interface between the electrodes and WSe2 free of dangling bond and Fermi level pinning, thus giving rise to the excellent performance of memory devices. Importantly, the interface trap states can be easily controlled by a simple oxygen plasma treatment of the SiO2 substrate, and subsequently, the performance of the multistate memory devices can be manipulated. Our findings provide a simple and efficient strategy to engineer the interface states for the multistate data storage applications and would motivate more investigations on the trap state-associated applications.
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Affiliation(s)
- Hongzhi Shen
- School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Junwen Ren
- School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Junze Li
- School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Yingying Chen
- School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Shangui Lan
- School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Jiaqi Wang
- School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Haizhen Wang
- School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Dehui Li
- School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China
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16
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Song C, Noh G, Kim TS, Kang M, Song H, Ham A, Jo MK, Cho S, Chai HJ, Cho SR, Cho K, Park J, Song S, Song I, Bang S, Kwak JY, Kang K. Growth and Interlayer Engineering of 2D Layered Semiconductors for Future Electronics. ACS NANO 2020; 14:16266-16300. [PMID: 33301290 DOI: 10.1021/acsnano.0c06607] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Layered materials that do not form a covalent bond in a vertical direction can be prepared in a few atoms to one atom thickness without dangling bonds. This distinctive characteristic of limiting thickness around the sub-nanometer level allowed scientists to explore various physical phenomena in the quantum realm. In addition to the contribution to fundamental science, various applications were proposed. Representatively, they were suggested as a promising material for future electronics. This is because (i) the dangling-bond-free nature inhibits surface scattering, thus carrier mobility can be maintained at sub-nanometer range; (ii) the ultrathin nature allows the short-channel effect to be overcome. In order to establish fundamental discoveries and utilize them in practical applications, appropriate preparation methods are required. On the other hand, adjusting properties to fit the desired application properly is another critical issue. Hence, in this review, we first describe the preparation method of layered materials. Proper growth techniques for target applications and the growth of emerging materials at the beginning stage will be extensively discussed. In addition, we suggest interlayer engineering via intercalation as a method for the development of artificial crystal. Since infinite combinations of the host-intercalant combination are possible, it is expected to expand the material system from the current compound system. Finally, inevitable factors that layered materials must face to be used as electronic applications will be introduced with possible solutions. Emerging electronic devices realized by layered materials are also discussed.
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Affiliation(s)
- Chanwoo Song
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Gichang Noh
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
- Center for Electronic Materials, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
| | - Tae Soo Kim
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Minsoo Kang
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Hwayoung Song
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Ayoung Ham
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Min-Kyung Jo
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
- Operando Methodology and Measurement Team, Interdisciplinary Materials Measurement Institute, Korea Research Institute of Standards and Science (KRISS), Daejeon 34113, Korea
| | - Seorin Cho
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Hyun-Jun Chai
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Seong Rae Cho
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Kiwon Cho
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Jeongwon Park
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Seungwoo Song
- Operando Methodology and Measurement Team, Interdisciplinary Materials Measurement Institute, Korea Research Institute of Standards and Science (KRISS), Daejeon 34113, Korea
| | - Intek Song
- Department of Applied Chemistry, Andong National University, Andong 36728, Korea
| | - Sunghwan Bang
- Materials & Production Engineering Research Institute, LG Electronics, Pyeongtaek-si 17709, Korea
| | - Joon Young Kwak
- Center for Electronic Materials, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
| | - Kibum Kang
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
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17
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Schauble K, Zakhidov D, Yalon E, Deshmukh S, Grady RW, Cooley KA, McClellan CJ, Vaziri S, Passarello D, Mohney SE, Toney MF, Sood AK, Salleo A, Pop E. Uncovering the Effects of Metal Contacts on Monolayer MoS 2. ACS NANO 2020; 14:14798-14808. [PMID: 32905703 DOI: 10.1021/acsnano.0c03515] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Metal contacts are a key limiter to the electronic performance of two-dimensional (2D) semiconductor devices. Here, we present a comprehensive study of contact interfaces between seven metals (Y, Sc, Ag, Al, Ti, Au, Ni, with work functions from 3.1 to 5.2 eV) and monolayer MoS2 grown by chemical vapor deposition. We evaporate thin metal films onto MoS2 and study the interfaces by Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, and electrical characterization. We uncover that (1) ultrathin oxidized Al dopes MoS2 n-type (>2 × 1012 cm-2) without degrading its mobility, (2) Ag, Au, and Ni deposition causes varying levels of damage to MoS2 (e.g. broadening Raman E' peak from <3 to >6 cm-1), and (3) Ti, Sc, and Y react with MoS2. Reactive metals must be avoided in contacts to monolayer MoS2, but control studies reveal the reaction is mostly limited to the top layer of multilayer films. Finally, we find that (4) thin metals do not significantly strain MoS2, as confirmed by X-ray diffraction. These are important findings for metal contacts to MoS2 and broadly applicable to many other 2D semiconductors.
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Affiliation(s)
- Kirstin Schauble
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
| | - Dante Zakhidov
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
| | - Eilam Yalon
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
| | - Sanchit Deshmukh
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
| | - Ryan W Grady
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
| | - Kayla A Cooley
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Connor J McClellan
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
| | - Sam Vaziri
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
| | - Donata Passarello
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Suzanne E Mohney
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Michael F Toney
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - A K Sood
- Department of Physics, India Institute of Science, Bangalore 560012, India
| | - Alberto Salleo
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
| | - Eric Pop
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
- Precourt Institute for Energy, Stanford University, Stanford, California 94305, United States
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18
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19
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Seo DB, Trung TN, Kim DO, Duc DV, Hong S, Sohn Y, Jeong JR, Kim ET. Plasmonic Ag-Decorated Few-Layer MoS 2 Nanosheets Vertically Grown on Graphene for Efficient Photoelectrochemical Water Splitting. NANO-MICRO LETTERS 2020; 12:172. [PMID: 34138153 PMCID: PMC7770824 DOI: 10.1007/s40820-020-00512-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Accepted: 07/28/2020] [Indexed: 05/28/2023]
Abstract
A controllable approach that combines surface plasmon resonance and two-dimensional (2D) graphene/MoS2 heterojunction has not been implemented despite its potential for efficient photoelectrochemical (PEC) water splitting. In this study, plasmonic Ag-decorated 2D MoS2 nanosheets were vertically grown on graphene substrates in a practical large-scale manner through metalorganic chemical vapor deposition of MoS2 and thermal evaporation of Ag. The plasmonic Ag-decorated MoS2 nanosheets on graphene yielded up to 10 times higher photo-to-dark current ratio than MoS2 nanosheets on indium tin oxide. The significantly enhanced PEC activity could be attributed to the synergetic effects of SPR and favorable graphene/2D MoS2 heterojunction. Plasmonic Ag nanoparticles not only increased visible-light and near-infrared absorption of 2D MoS2, but also induced highly amplified local electric field intensity in 2D MoS2. In addition, the vertically aligned 2D MoS2 on graphene acted as a desirable heterostructure for efficient separation and transportation of photo-generated carriers. This study provides a promising path for exploiting the full potential of 2D MoS2 for practical large-scale and efficient PEC water-splitting applications.
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Affiliation(s)
- Dong-Bum Seo
- Department of Materials Science and Engineering, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Tran Nam Trung
- Department of Materials Science and Engineering, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Dong-Ok Kim
- Department of Materials Science and Engineering, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Duong Viet Duc
- Department of Materials Science and Engineering, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Sungmin Hong
- Department of Chemistry, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Youngku Sohn
- Department of Chemistry, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Jong-Ryul Jeong
- Department of Materials Science and Engineering, Chungnam National University, Daejeon, 34134, Republic of Korea
| | - Eui-Tae Kim
- Department of Materials Science and Engineering, Chungnam National University, Daejeon, 34134, Republic of Korea.
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20
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Somvanshi D, Ber E, Bailey CS, Pop E, Yalon E. Improved Current Density and Contact Resistance in Bilayer MoSe 2 Field Effect Transistors by AlO x Capping. ACS APPLIED MATERIALS & INTERFACES 2020; 12:36355-36361. [PMID: 32678569 PMCID: PMC7588022 DOI: 10.1021/acsami.0c09541] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Atomically thin semiconductors are of interest for future electronics applications, and much attention has been given to monolayer (1L) sulfides, such as MoS2, grown by chemical vapor deposition (CVD). However, reports on the electrical properties of CVD-grown selenides, and MoSe2 in particular, are scarce. Here, we compare the electrical properties of 1L and bilayer (2L) MoSe2 grown by CVD and capped by sub-stoichiometric AlOx. The 2L channels exhibit ∼20× lower contact resistance (RC) and ∼30× larger current density compared with 1L channels. RC is further reduced by >5× with AlOx capping, which enables improved transistor current density. Overall, 2L AlOx-capped MoSe2 transistors (with ∼500 nm channel length) achieve improved current density (∼65 μA/μm at VDS = 4 V), a good Ion/Ioff ratio of >106, and an RC of ∼60 kΩ·μm. The weaker performance of 1L devices is due to their sensitivity to processing and ambient. Our results suggest that 2L (or few layers) is preferable to 1L for improved electronic properties in applications that do not require a direct band gap, which is a key finding for future two-dimensional electronics.
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Affiliation(s)
- Divya Somvanshi
- Viterbi
Department of Electrical Engineering, Technion-Israel
Institute of Technology, Haifa 32000, Israel
| | - Emanuel Ber
- Viterbi
Department of Electrical Engineering, Technion-Israel
Institute of Technology, Haifa 32000, Israel
| | - Connor S. Bailey
- Department
of Electrical Engineering, Stanford University, Stanford, California 94305, United States
| | - Eric Pop
- Department
of Electrical Engineering, Stanford University, Stanford, California 94305, United States
- Department
of Materials Science & Engineering, Stanford University, Stanford, California 94305, United States
- Precourt
Institute for Energy, Stanford University, Stanford, California 94305, United States
| | - Eilam Yalon
- Viterbi
Department of Electrical Engineering, Technion-Israel
Institute of Technology, Haifa 32000, Israel
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21
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Site-specific electrical contacts with the two-dimensional materials. Nat Commun 2020; 11:3982. [PMID: 32770067 PMCID: PMC7414847 DOI: 10.1038/s41467-020-17784-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 07/15/2020] [Indexed: 11/18/2022] Open
Abstract
Electrical contact is an essential issue for all devices. Although the contacts of the emergent two-dimensional materials have been extensively investigated, it is still challenging to produce excellent contacts. The face and edge type contacts have been applied previously, however a comparative study on the site-specific contact performances is lacking. Here we report an in situ transmission electron microscopy study on the contact properties with a series of 2D materials. By manipulating the contact configurations in real time, it is confirmed that, for 2D semiconductors the vdW type face contacts exhibit superior conductivity compared with the non-vdW type contacts. The direct quantum tunneling across the vdW bonded interfaces are virtually more favorable than the Fowler–Nordheim tunneling across chemically bonded interfaces for contacts. Meanwhile, remarkable area, thickness, geometry, and defect site dependences are revealed. Our work sheds light on the significance of contact engineering for 2D materials in future applications. Here, the authors use in situ transmission electron microscopy to measure the interface properties of electrical contacts with MoS2, ReS2, and graphene, and find that direct quantum tunnelling across van-der-Waals-bonded interfaces is more favourable than Fowler–Nordheim tunnelling across chemically bonded interfaces.
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