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Gu S, Liu W, Mi S, Xian G, Guo J, Pang F, Chen S, Yang H, Gao HJ, Cheng Z. Twist angle-dependent work functions in CVD-grown twisted bilayer graphene probed by Kelvin probe force microscopy. NANOSCALE 2023; 15:5825-5833. [PMID: 36857709 DOI: 10.1039/d2nr07242d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Tailoring the interlayer twist angle of bilayer graphene (BLG) significantly affects its electronic properties, including its superconductivity, topological transitions, ferromagnetic states, and correlated insulating states. These exotic electronic properties are sensitive to the work functions of BLG samples. In this study, the twist angle-dependent work functions of chemical vapour deposition-grown twisted bilayer graphene (tBLG) were investigated in detail using Kelvin probe force microscopy (KPFM) in combination with Raman spectroscopy. The thickness-dependent surface potentials of Bernal-stacked multilayer graphene were measured. It is found that with the increase in the number of layers, the work function decreases and tends to saturate. Bernal-stacked BLG and tBLG were determined via KPFM due to their twist angle-specific surface potentials. The detailed relationship between the twist angle and surface potential was determined via in situ KPFM and Raman spectral measurements. With the increase in the twist angle, the work function of tBLG will increase rapidly and then increase slowly when it is greater than 5°. The thermal stability of tBLG was investigated through a controlled annealing process. tBLG will become Bernal-stacked BLG after annealing at 350 °C. Our work provides the twist angle-dependent surface potentials of tBLG and provides the relevant conditions for the stability of the twist angle, which lays the foundation for further exploration of its twist angle-dependent electronic properties.
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Affiliation(s)
- Shangzhi Gu
- Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Department of Physics, Renmin University of China, Beijing 100872, China.
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190, China.
| | - Wenyu Liu
- Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Department of Physics, Renmin University of China, Beijing 100872, China.
| | - Shuo Mi
- Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Department of Physics, Renmin University of China, Beijing 100872, China.
| | - Guoyu Xian
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190, China.
| | - Jiangfeng Guo
- Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Department of Physics, Renmin University of China, Beijing 100872, China.
| | - Fei Pang
- Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Department of Physics, Renmin University of China, Beijing 100872, China.
| | - Shanshan Chen
- Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Department of Physics, Renmin University of China, Beijing 100872, China.
| | - Haitao Yang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190, China.
| | - Hong-Jun Gao
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190, China.
| | - Zhihai Cheng
- Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Department of Physics, Renmin University of China, Beijing 100872, China.
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Dat VD, Vu TV, Lavrentyev AA, Khyzhun OY, Hieu NN, Tong HD. First-principles study on the structural properties of 2D MXene SnSiGeN 4 and its electronic properties under the effects of strain and an external electric field. RSC Adv 2022; 12:29113-29123. [PMID: 36320756 PMCID: PMC9555058 DOI: 10.1039/d2ra05265b] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Accepted: 09/24/2022] [Indexed: 12/04/2022] Open
Abstract
The MXene SnSiGeN4 monolayer as a new member of the MoSi2N4 family was proposed for the first time, and its structural and electronic properties were explored by applying first-principles calculations with both PBE and hybrid HSE06 approaches. The layered hexagonal honeycomb structure of SnSiGeN4 was determined to be stable under dynamical effects or at room temperature of 300 K, with a rather high cohesive energy of 7.0 eV. The layered SnSiGeN4 has a Young's modulus of 365.699 N m-1 and a Poisson's ratio of 0.295. The HSE06 approach predicted an indirect band gap of around 2.4 eV for the layered SnSiGeN4. While the major donation from the N-p orbitals to the band structure makes SnSiGeN4's band gap close to those of similar 2D MXenes, the smaller distributions from the other orbitals of Sn, Si, and Ge slightly vary this band gap. The work functions of the GeN and SiN surfaces are 6.367 eV and 5.903 eV, respectively. The band gap of the layered SnSiGeN4 can be easily tuned by strain and an external electric field. A semiconductor-metal transition can occur at certain values of strain, and with an electric field higher than 5 V nm-1. The electron mobility of the layered SnSiGeN4 can reach up to 677.4 cm2 V-1 s-1, which is much higher than the hole mobility of about 52 cm2 V-1 s-1. The mentioned characteristics make the layered SnSiGeN4 a very promising material for use in electronic and photoelectronic devices, and for solar energy conversion.
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Affiliation(s)
- Vo D. Dat
- Laboratory for Computational Physics, Institute for Computational Science and Artificial Intelligence, Van Lang UniversityHo Chi Minh CityVietnam,Faculty of Mechanical – Electrical and Computer Engineering, Van Lang UniversityHo Chi Minh CityVietnam
| | - Tuan V. Vu
- Laboratory for Computational Physics, Institute for Computational Science and Artificial Intelligence, Van Lang UniversityHo Chi Minh CityVietnam,Faculty of Mechanical – Electrical and Computer Engineering, Van Lang UniversityHo Chi Minh CityVietnam
| | - A. A. Lavrentyev
- Department of Electrical Engineering and Electronics, Don State Technical University1 Gagarin Square, 344010 Rostov-on-DonRussian Federation
| | - O. Y. Khyzhun
- Frantsevych Institute for Problems of Materials Science, National Academy of Sciences of Ukraine3 Krzhyzhanovsky StreetUA-03142 KyivUkraine
| | - Nguyen N. Hieu
- Institute of Research and Development, Duy Tan UniversityDa Nang 550000Vietnam,Faculty of Natural Sciences, Duy Tan UniversityDa Nang 550000Vietnam
| | - Hien D. Tong
- Faculty of Engineering, Vietnamese-German UniversityBinh DuongVietnam
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Lee JJ, Jung DH, Shin DH, Lee H. Highly stable semitransparent multilayer graphene/LaVO 3vertical-heterostructure photodetectors. NANOTECHNOLOGY 2022; 33:395202. [PMID: 35617873 DOI: 10.1088/1361-6528/ac73a1] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Accepted: 05/26/2022] [Indexed: 06/15/2023]
Abstract
A heterostructure composed of a combination of semi-metallic graphene (Gr) and high-absorption LaVO3is ideal for high-performance translucent photodetector (PD) applications. Here, we present multilayer Gr/LaVO3vertical-heterostructure semitransparent PDs with various layer numbers (Ln). AtLn= 2, the PD shows the best performance with a responsivity (R) of 0.094 A W-1and a specific detectivity (D*) of 7.385 × 107cm Hz1/2W-1at 532 nm. Additionally, the average visible transmittance of the PD is 63%, i.e. it is semitransparent. We increased photocurrent (PC) by approximately 13%, from 0.564 to 0.635μA cm-2by using an Al reflector on the semitransparent PD. The PC of an unencapsulated PD maintains about 86% (from 0.571 to 0.493μA cm-2) of its initial PC value after 2000 h at 25 °C temperature/30% relative humidity, showing good stability. This behavior is superior to that of previously reported graphene-based PDs. These results show that these PDs have great potential for semitransparent optoelectronic applications.
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Affiliation(s)
- Jae Jun Lee
- Department of Applied Physics, Institute of Natural Sciences, and Integrated Education Institute for Frontier Science and Technology (BK21 Four), Kyung Hee University, Yongin 17104, Republic of Korea
| | - Dae Ho Jung
- Department of Applied Physics, Institute of Natural Sciences, and Integrated Education Institute for Frontier Science and Technology (BK21 Four), Kyung Hee University, Yongin 17104, Republic of Korea
| | - Dong Hee Shin
- Department of Physics, Andong National University, Andong, Gyeongbuk, 36729, Republic of Korea
| | - Hosun Lee
- Department of Applied Physics, Institute of Natural Sciences, and Integrated Education Institute for Frontier Science and Technology (BK21 Four), Kyung Hee University, Yongin 17104, Republic of Korea
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Dat VD, Vu TV. Janus monolayer HfSO with improved optical properties as a novel material for photovoltaic and photocatalyst applications. NEW J CHEM 2022. [DOI: 10.1039/d1nj05096f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
First principles calculations were performed to investigate the photocatalytic behavior of 2D Janus monolayer HfSO at equilibrium and under the influence of strains and external electric fields.
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Affiliation(s)
- Vo D. Dat
- Group of Computational Physics and Simulation of Advanced Materials, Institute of Applied Technology, Thu Dau Mot University, Binh Duong Province, Vietnam
| | - Tuan V. Vu
- Division of Computational Physics, Institute for Computational Science, Ton Duc Thang University, Ho Chi Minh City, Vietnam
- Faculty of Electrical & Electronics Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam
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Chae S, Le TH, Park CS, Choi Y, Kim S, Lee U, Heo E, Lee H, Kim YA, Kwon OS, Yoon H. Anomalous restoration of sp 2 hybridization in graphene functionalization. NANOSCALE 2020; 12:13351-13359. [PMID: 32572409 DOI: 10.1039/d0nr03422c] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The functionalization of nanocarbon materials such as graphene has attracted considerable attention over the past decades. In this work, we designed and synthesized a unique N-heterocyclic carbene compound with a pyrene tail group (NHCp) to investigate how carbene species can be used for the functionalization of graphene. Although the carbene moiety of NHCp has the ability to covalently bond to graphene, the pyrene tail can noncovalently interact with graphene and allows monitoring its surrounding microenvironment. The major characteristics of the resulting nanohybrids were highly dependent on the type of graphene and the NHCp-to-graphene weight ratio. Importantly, despite the covalent functionalization of graphene, an anomalous decrease in the intensity of the Raman D peak and improved conductivity were observed for the nanohybrids. It was found that the covalent bond of NHCp to the graphene edge may allow the hybridization of their orbitals, which affects electronic energy levels and alters the double resonance process that originates the D peak at the edge defect. Importantly, the NHCp compound can act as a π acceptor (not just as a σ donor) via the NHCp-graphene covalent bridge. This is the first report showing that the concept of π-backdonation can be realized in two-dimensional materials, such as graphene, and rationally designed carbene molecules can functionalize graphene without losing their beneficial sp2 hybridization characteristics.
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Affiliation(s)
- Subin Chae
- Department of Polymer Engineering, Graduate School, Chonnam National University, 77 Yongbong-ro, Gwangju 61186, South Korea
| | - Thanh-Hai Le
- Department of Polymer Engineering, Graduate School, Chonnam National University, 77 Yongbong-ro, Gwangju 61186, South Korea
| | - Chul Soon Park
- Department of Polymer Engineering, Graduate School, Chonnam National University, 77 Yongbong-ro, Gwangju 61186, South Korea and Infectious Disease Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), 125 Gwahak-ro, Daejeon 34141, South Korea.
| | - Yunseok Choi
- Department of Polymer Engineering, Graduate School, Chonnam National University, 77 Yongbong-ro, Gwangju 61186, South Korea
| | - Semin Kim
- Department of Polymer Engineering, Graduate School, Chonnam National University, 77 Yongbong-ro, Gwangju 61186, South Korea
| | - Unhan Lee
- Department of Polymer Engineering, Graduate School, Chonnam National University, 77 Yongbong-ro, Gwangju 61186, South Korea
| | - Eunseo Heo
- Department of Polymer Engineering, Graduate School, Chonnam National University, 77 Yongbong-ro, Gwangju 61186, South Korea
| | - Haney Lee
- Alan G. MacDiarmid Energy Research Institute & School of Polymer Science and Engineering, Chonnam National University, 77 Yongbong-ro, Gwangju 61186, South Korea.
| | - Yoong Ahm Kim
- Alan G. MacDiarmid Energy Research Institute & School of Polymer Science and Engineering, Chonnam National University, 77 Yongbong-ro, Gwangju 61186, South Korea. and Department of Polymer Engineering, Graduate School, Chonnam National University, 77 Yongbong-ro, Gwangju 61186, South Korea
| | - Oh Seok Kwon
- Infectious Disease Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), 125 Gwahak-ro, Daejeon 34141, South Korea. and Department of NanoBiotechnology, Korea University of Science and Technology (UST), 125 Gwahak-ro, Daejeon 34141, South Korea
| | - Hyeonseok Yoon
- Alan G. MacDiarmid Energy Research Institute & School of Polymer Science and Engineering, Chonnam National University, 77 Yongbong-ro, Gwangju 61186, South Korea. and Department of Polymer Engineering, Graduate School, Chonnam National University, 77 Yongbong-ro, Gwangju 61186, South Korea
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