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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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Serraon ACF, Del Rosario JAD, Abel Chuang PY, Chong MN, Morikawa Y, Padama AAB, Ocon JD. Alkaline earth atom doping-induced changes in the electronic and magnetic properties of graphene: a density functional theory study. RSC Adv 2021; 11:6268-6283. [PMID: 35423162 PMCID: PMC8694801 DOI: 10.1039/d0ra08115a] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Accepted: 12/28/2020] [Indexed: 12/15/2022] Open
Abstract
Density functional theory was used to investigate the effects of doping alkaline earth metal atoms (beryllium, magnesium, calcium and strontium) on graphene. Electron transfer from the dopant atom to the graphene substrate was observed and was further probed by a combined electron localization function/non-covalent interaction (ELF/NCI) approach. This approach demonstrates that predominantly ionic bonding occurs between the alkaline earth dopants and the substrate, with beryllium doping having a variant characteristic as a consequence of electronegativity equalization attributed to its lower atomic number relative to carbon. The ionic bonding induces spin-polarized electronic structures and lower workfunctions for Mg-, Ca-, and Sr-doped graphene systems as compared to the pristine graphene. However, due to its variant bonding characteristic, Be-doped graphene exhibits non-spin-polarized p-type semiconductor behavior, which is consistent with previous works, and an increase in workfunction relative to pristine graphene. Dirac half-metal-like behavior was predicted for magnesium doped graphene while calcium doped and strontium doped graphene were predicted to have bipolar magnetic semiconductor behavior. These changes in the electronic and magnetic properties of alkaline earth doped graphene may be of importance for spintronic and other electronic device applications. Alkaline earth atom dopants on graphene induce work function tuning and spin polarized electronic properties by ionic bonding.![]()
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Affiliation(s)
- Ace Christian F Serraon
- Laboratory of Electrochemical Engineering, Department of Chemical Engineering, College of Engineering, University of the Philippines Diliman Quezon City 1101 Philippines +63 981 8500 loc. 3213
| | - Julie Anne D Del Rosario
- Laboratory of Electrochemical Engineering, Department of Chemical Engineering, College of Engineering, University of the Philippines Diliman Quezon City 1101 Philippines +63 981 8500 loc. 3213
| | - Po-Ya Abel Chuang
- Thermal and Electrochemical Energy Laboratory, School of Engineering, University of California Merced CA 95343 USA
| | - Meng Nan Chong
- School of Engineering, Chemical Engineering Discipline, Monash University Malaysia Bandar Sunway Selangor Darul Ehsan 47500 Malaysia
| | - Yoshitada Morikawa
- Department of Precision Engineering, Graduate School of Engineering, Osaka University Suita Osaka 565-0871 Japan
| | - Allan Abraham B Padama
- Institute of Mathematical Sciences and Physics, College of Arts and Sciences, University of the Philippines Los Baños Laguna 4031 Philippines
| | - Joey D Ocon
- Laboratory of Electrochemical Engineering, Department of Chemical Engineering, College of Engineering, University of the Philippines Diliman Quezon City 1101 Philippines +63 981 8500 loc. 3213
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Wei J, Huang JK, Du J, Bian B, Li S, Wang D. Effect of the geometry of precursor crucibles on the growth of MoS 2 flakes by chemical vapor deposition. NEW J CHEM 2020. [DOI: 10.1039/d0nj05486k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Chemical vapor deposition (CVD) employing a furnace with multiple temperature zones is still the best and most widely used method for preparing high-quality MoS2 flakes.
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Affiliation(s)
- Jinlei Wei
- School of Science, Jiangnan University
- Wuxi 214122
- China
- School of Materials Science and Engineering, The University of New South Wales
- Sydney
| | - Jing-Kai Huang
- School of Materials Science and Engineering, The University of New South Wales
- Sydney
- Australia
| | - Jianhao Du
- School of Materials Science and Engineering, The University of New South Wales
- Sydney
- Australia
| | - Baoan Bian
- School of Science, Jiangnan University
- Wuxi 214122
- China
| | - Sean Li
- School of Materials Science and Engineering, The University of New South Wales
- Sydney
- Australia
| | - Danyang Wang
- School of Materials Science and Engineering, The University of New South Wales
- Sydney
- Australia
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