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Bussolotti F, Kawai H, Maddumapatabandi TD, Fu W, Khoo KH, Goh KEJ. Role of S-Vacancy Concentration in Air Oxidation of WS 2 Single Crystals. ACS Nano 2024; 18:8706-8717. [PMID: 38465866 DOI: 10.1021/acsnano.3c10389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2024]
Abstract
Semiconducting transition metal dichalcogenides (TMDs) are a class of two-dimensional materials with potential applications in optoelectronics, spintronics, valleytronics, and quantum information processing. Understanding their stability under ambient conditions is critical for determining their in-air processability during device fabrication and for predicting their long-term device performance stability. While the effects of environmental conditions (i.e., oxygen, moisture, and light) on TMD degradation are well-acknowledged, the role of defects in driving their oxidation remains unclear. We conducted a systematic X-ray photoelectron spectroscopy study on WS2 single crystals with different surface S-vacancy concentrations formed via controlled argon sputtering. Oxidation primarily occurred at defect concentrations ≥ 10%, resulting in stoichiometric WO3 formation, while a stable surface was observed at lower concentrations. Theoretical calculations informed us that single S-vacancies do not spontaneously oxidize, while defect pairing at high vacancy concentrations facilitates O2 dissociation and subsequent oxide formation. Our XPS results also point to vacancy-related structural and electrostatic disorder as the main origin for the p-type characteristics that persists even after oxidation. Despite the complex interplay between defects and TMD oxidation processes, our work unveils scientifically informed guidance for working effectively with TMDs.
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Affiliation(s)
- Fabio Bussolotti
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634, Republic of Singapore
| | - Hiroyo Kawai
- Institute of High-Performance Computing (IHPC), Agency for Science, Technology and Research, 1 Fusionopolis Way, #16-16 Connexis, Singapore 138632, Republic of Singapore
| | - Thathsara D Maddumapatabandi
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634, Republic of Singapore
| | - Wei Fu
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634, Republic of Singapore
| | - Khoong Hong Khoo
- Institute of High-Performance Computing (IHPC), Agency for Science, Technology and Research, 1 Fusionopolis Way, #16-16 Connexis, Singapore 138632, Republic of Singapore
| | - Kuan Eng Johnson Goh
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634, Republic of Singapore
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2
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Fu W, John M, Maddumapatabandi TD, Bussolotti F, Yau YS, Lin M, Johnson Goh KE. Toward Edge Engineering of Two-Dimensional Layered Transition-Metal Dichalcogenides by Chemical Vapor Deposition. ACS Nano 2023; 17:16348-16368. [PMID: 37646426 DOI: 10.1021/acsnano.3c04581] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Abstract
The manipulation of edge configurations and structures in atomically-thin transition metal dichalcogenides (TMDs) for versatile functionalization has attracted intensive interest in recent years. The chemical vapor deposition (CVD) approach has shown promise for TMD edge engineering of atomic edge configurations (1H, 1T or 1T'-zigzag or armchair edges) as well as diverse edge morphologies (1D nanoribbons, 2D dendrites, 3D spirals, etc.). These edge-rich TMD layers offer versatile candidates for probing the physical and chemical properties and exploring potential applications in electronics, optoelectronics, catalysis, sensing, and quantum technologies. In this Review, we present an overview of the current state-of-the-art in the manipulation of TMD atomic edges and edge-rich structures using CVD. We highlight the vast range of distinct properties associated with these edge configurations and structures and provide insights into the opportunities afforded by such edge-functionalized crystals. The objective of this Review is to motivate further research and development efforts to use CVD as a scalable approach to harness the benefits of such crystal-edge engineering.
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Affiliation(s)
- Wei Fu
- Institute of Materials Research and Engineering (IMRE), Agency for Science Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03 138634, Singapore
| | - Mark John
- Institute of Materials Research and Engineering (IMRE), Agency for Science Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03 138634, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3 117551, Singapore
| | - Thathsara D Maddumapatabandi
- Institute of Materials Research and Engineering (IMRE), Agency for Science Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03 138634, Singapore
| | - Fabio Bussolotti
- Institute of Materials Research and Engineering (IMRE), Agency for Science Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03 138634, Singapore
| | - Yong Sean Yau
- Institute of Materials Research and Engineering (IMRE), Agency for Science Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03 138634, Singapore
| | - Ming Lin
- Institute of Materials Research and Engineering (IMRE), Agency for Science Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03 138634, Singapore
| | - Kuan Eng Johnson Goh
- Institute of Materials Research and Engineering (IMRE), Agency for Science Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03 138634, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3 117551, Singapore
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue 639798, Singapore
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3
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Zhang Y, Venkatakrishnarao D, Bosman M, Fu W, Das S, Bussolotti F, Lee R, Teo SL, Huang D, Verzhbitskiy I, Jiang Z, Jiang Z, Chai J, Tong SW, Ooi ZE, Wong CPY, Ang YS, Goh KEJ, Lau CS. Liquid-Metal-Printed Ultrathin Oxides for Atomically Smooth 2D Material Heterostructures. ACS Nano 2023; 17:7929-7939. [PMID: 37021759 DOI: 10.1021/acsnano.3c02128] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Two-dimensional (2D) semiconductors are promising channel materials for continued downscaling of complementary metal-oxide-semiconductor (CMOS) logic circuits. However, their full potential continues to be limited by a lack of scalable high-k dielectrics that can achieve atomically smooth interfaces, small equivalent oxide thicknesses (EOTs), excellent gate control, and low leakage currents. Here, large-area liquid-metal-printed ultrathin Ga2O3 dielectrics for 2D electronics and optoelectronics are reported. The atomically smooth Ga2O3/WS2 interfaces enabled by the conformal nature of liquid metal printing are directly visualized. Atomic layer deposition compatibility with high-k Ga2O3/HfO2 top-gate dielectric stacks on a chemical-vapor-deposition-grown monolayer WS2 is demonstrated, achieving EOTs of ∼1 nm and subthreshold swings down to 84.9 mV/dec. Gate leakage currents are well within requirements for ultrascaled low-power logic circuits. These results show that liquid-metal-printed oxides can bridge a crucial gap in dielectric integration of 2D materials for next-generation nanoelectronics.
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Affiliation(s)
- Yiyu Zhang
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
| | - Dasari Venkatakrishnarao
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
| | - Michel Bosman
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, 117575 Singapore
| | - Wei Fu
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
| | - Sarthak Das
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
| | - Fabio Bussolotti
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
| | - Rainer Lee
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
| | - Siew Lang Teo
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
| | - Ding Huang
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
| | - Ivan Verzhbitskiy
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
| | - Zhuojun Jiang
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
| | - Zhuoling Jiang
- Science, Mathematics and Technology, Singapore University of Technology and Design, 8 Somapah Road, 487372 Singapore
| | - Jianwei Chai
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
| | - Shi Wun Tong
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
| | - Zi-En Ooi
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
| | - Calvin Pei Yu Wong
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
| | - Yee Sin Ang
- Science, Mathematics and Technology, Singapore University of Technology and Design, 8 Somapah Road, 487372 Singapore
| | - Kuan Eng Johnson Goh
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117551 Singapore
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore
| | - Chit Siong Lau
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
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4
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Lau CS, Chee JY, Cao L, Ooi ZE, Tong SW, Bosman M, Bussolotti F, Deng T, Wu G, Yang SW, Wang T, Teo SL, Wong CPY, Chai JW, Chen L, Zhang ZM, Ang KW, Ang YS, Goh KEJ. Gate-Defined Quantum Confinement in CVD 2D WS 2. Adv Mater 2022; 34:e2103907. [PMID: 34437744 DOI: 10.1002/adma.202103907] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 06/19/2021] [Indexed: 06/13/2023]
Abstract
Temperature-dependent transport measurements are performed on the same set of chemical vapor deposition (CVD)-grown WS2 single- and bilayer devices before and after atomic layer deposition (ALD) of HfO2 . This isolates the influence of HfO2 deposition on low-temperature carrier transport and shows that carrier mobility is not charge impurity limited as commonly thought, but due to another important but commonly overlooked factor: interface roughness. This finding is corroborated by circular dichroic photoluminescence spectroscopy, X-ray photoemission spectroscopy, cross-sectional scanning transmission electron microscopy, carrier-transport modeling, and density functional modeling. Finally, electrostatic gate-defined quantum confinement is demonstrated using a scalable approach of large-area CVD-grown bilayer WS2 and ALD-grown HfO2 . The high dielectric constant and low leakage current enabled by HfO2 allows an estimated quantum dot size as small as 58 nm. The ability to lithographically define increasingly smaller devices is especially important for transition metal dichalcogenides due to their large effective masses, and should pave the way toward their use in quantum information processing applications.
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Affiliation(s)
- Chit Siong Lau
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
| | - Jing Yee Chee
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
| | - Liemao Cao
- Science, Mathematics and Technology, Singapore University of Technology, 8 Somapah Road, Singapore, 487372, Singapore
| | - Zi-En Ooi
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
| | - Shi Wun Tong
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
| | - Michel Bosman
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore, 117575, Singapore
| | - Fabio Bussolotti
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
| | - Tianqi Deng
- Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, #16-16 Connexis, Singapore, 138632, Singapore
| | - Gang Wu
- Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, #16-16 Connexis, Singapore, 138632, Singapore
| | - Shuo-Wang Yang
- Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, #16-16 Connexis, Singapore, 138632, Singapore
| | - Tong Wang
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
| | - Siew Lang Teo
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
| | - Calvin Pei Yu Wong
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
| | - Jian Wei Chai
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
| | - Li Chen
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore
| | - Zhong Ming Zhang
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
| | - Kah-Wee Ang
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore
| | - Yee Sin Ang
- Science, Mathematics and Technology, Singapore University of Technology, 8 Somapah Road, Singapore, 487372, Singapore
| | - Kuan Eng Johnson Goh
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117551, Singapore
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5
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Bussolotti F, Yang J, Kawai H, Wong CPY, Goh KEJ. Impact of S-Vacancies on the Charge Injection Barrier at the Electrical Contact with the MoS 2 Monolayer. ACS Nano 2021; 15:2686-2697. [PMID: 33502172 DOI: 10.1021/acsnano.0c07982] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Making electrical contacts to semiconducting transition metal dichalcogenides (TMDCs) represents a major bottleneck for high device performance, often manifesting as strong Fermi level pinning and high contact resistance. Despite intense ongoing research, the mechanism by which lattice defects in TMDCs impact the transport properties across the contact-TMDC interface remains unsettled. Here we study the impact of S-vacancies on the electronic properties at a MoS2 monolayer interfaced with graphite by photoemission spectroscopy, where the defect density is selectively controlled by Ar sputtering. A clear reduction of the MoS2 core level and valence band binding energies is observed as the defect density increases. The experimental results are explained in terms of (i) gap states' energy distribution and (ii) S-vacancies' electrostatic disorder effect. Our model indicates that the Fermi level pinning at deep S-vacancy gap states is the origin of the commonly reported large electron injection barrier (∼0.5 eV) at the MoS2 ML interface with low work function metals. At the contact with high work function electrodes, S-vacancies do not significantly affect the hole injection barrier, which is intrinsically favored by Fermi level pinning at shallow occupied gap states. Our results clarify the importance of S-vacancies and electrostatic disorder in TMDC-based electronic devices, which could lead to strategies for optimizing device performance and production.
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Affiliation(s)
- Fabio Bussolotti
- Institute of Materials Research & Engineering (IMRE), Agency for Science, Technology, and Research (A*STAR), 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634, Singapore
| | - Jing Yang
- Institute of High Performance Computing (IHPC), Agency for Science, Technology and Research (A*STAR), 1 Fusionopolis Way, #16-16 Connexis, Singapore 138632, Singapore
| | - Hiroyo Kawai
- Institute of High Performance Computing (IHPC), Agency for Science, Technology and Research (A*STAR), 1 Fusionopolis Way, #16-16 Connexis, Singapore 138632, Singapore
| | - Calvin Pei Yu Wong
- Institute of Materials Research & Engineering (IMRE), Agency for Science, Technology, and Research (A*STAR), 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634, Singapore
| | - Kuan Eng Johnson Goh
- Institute of Materials Research & Engineering (IMRE), Agency for Science, Technology, and Research (A*STAR), 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
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6
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Chua R, Yang J, He X, Yu X, Yu W, Bussolotti F, Wong PKJ, Loh KP, Breese MBH, Goh KEJ, Huang YL, Wee ATS. Can Reconstructed Se-Deficient Line Defects in Monolayer VSe 2 Induce Magnetism? Adv Mater 2020; 32:e2000693. [PMID: 32383232 DOI: 10.1002/adma.202000693] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 04/02/2020] [Accepted: 04/13/2020] [Indexed: 06/11/2023]
Abstract
There have been several recent conflicting reports on the ferromagnetism of clean monolayer VSe2 . Herein, the controllable formation of 1D defect line patterns in vanadium diselenide (VSe2 ) monolayers initiated by thermal annealing is presented. Using scanning tunneling microscopy and q-plus atomic force microscopy techniques, the 1D line features are determined to be 8-member-ring arrays, formed via a Se deficient reconstruction process. The reconstructed VSe2 monolayer with Se-deficient line defects displays room-temperature ferromagnetism under X-ray magnetic circular dichroism and magnetic force microscopy, consistent with the density functional theory calculations. This study possibly resolves the controversy on whether ferromagnetism is intrinsic in monolayer VSe2 , and highlights the importance of controlling and understanding the atomic structures of surface defects in 2D crystals, which could play key roles in the material properties and hence potential device applications.
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Affiliation(s)
- Rebekah Chua
- NUS Graduate School for Integrative Sciences & Engineering (NGS), University Hall, Tan Chin Tuan Wing, 21 Lower Kent Ridge, Singapore, 119077, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117542, Singapore
| | - Jing Yang
- Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, #16-16 Connexis, Singapore, 138632, Singapore
| | - Xiaoyue He
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117542, Singapore
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China
| | - Xiaojiang Yu
- Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore, 117603, Singapore
| | - Wei Yu
- Department of Chemistry, National University of Singapore, 2 Science Drive 3, Singapore, 117542, Singapore
| | - Fabio Bussolotti
- Institute of Materials Research & Engineering (IMRE), A*STAR (Agency for Science, Technology, and Research), 2 Fusionopolis Way, Innovis, Singapore, 138634, Singapore
| | - Ping Kwan Johnny Wong
- Centre for Advanced 2D Materials, National University of Singapore, Block S14, Level 6, 6 Science Drive 2, Singapore, 117546, Singapore
| | - Kian Ping Loh
- NUS Graduate School for Integrative Sciences & Engineering (NGS), University Hall, Tan Chin Tuan Wing, 21 Lower Kent Ridge, Singapore, 119077, Singapore
- Department of Chemistry, National University of Singapore, 2 Science Drive 3, Singapore, 117542, Singapore
- Centre for Advanced 2D Materials, National University of Singapore, Block S14, Level 6, 6 Science Drive 2, Singapore, 117546, Singapore
| | - Mark B H Breese
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117542, Singapore
- Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore, 117603, Singapore
| | - Kuan Eng Johnson Goh
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117542, Singapore
- Institute of Materials Research & Engineering (IMRE), A*STAR (Agency for Science, Technology, and Research), 2 Fusionopolis Way, Innovis, Singapore, 138634, Singapore
| | - Yu Li Huang
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117542, Singapore
| | - Andrew T S Wee
- NUS Graduate School for Integrative Sciences & Engineering (NGS), University Hall, Tan Chin Tuan Wing, 21 Lower Kent Ridge, Singapore, 119077, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117542, Singapore
- Centre for Advanced 2D Materials, National University of Singapore, Block S14, Level 6, 6 Science Drive 2, Singapore, 117546, Singapore
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7
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Wong PKJ, Zhang W, Zhou J, Bussolotti F, Yin X, Zhang L, N'Diaye AT, Morton SA, Chen W, Goh KEJ, de Jong MP, Feng YP, Wee ATS. Correction to Metallic 1T Phase, 3d 1 Electronic Configuration and Charge Density Wave Order in Molecular-Beam Epitaxy Grown Monolayer Vanadium Ditelluride. ACS Nano 2020; 14:1210. [PMID: 31860267 DOI: 10.1021/acsnano.9b09833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
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8
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Wong PKJ, Zhang W, Zhou J, Bussolotti F, Yin X, Zhang L, N'Diaye AT, Morton SA, Chen W, Goh J, de Jong MP, Feng YP, Wee ATS. Metallic 1T Phase, 3d 1 Electronic Configuration and Charge Density Wave Order in Molecular Beam Epitaxy Grown Monolayer Vanadium Ditelluride. ACS Nano 2019; 13:12894-12900. [PMID: 31693338 DOI: 10.1021/acsnano.9b05349] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We present a combined experimental and theoretical study of monolayer vanadium ditelluride, VTe2, grown on highly oriented pyrolytic graphite by molecular-beam epitaxy. Using various in situ microscopic and spectroscopic techniques, including scanning tunneling microscopy/spectroscopy, synchrotron X-ray and angle-resolved photoemission, and X-ray absorption, together with theoretical analysis by density functional theory calculations, we demonstrate direct evidence of the metallic 1T phase and 3d1 electronic configuration in monolayer VTe2 that also features a (4 × 4) charge density wave order at low temperatures. In contrast to previous theoretical predictions, our element-specific characterization by X-ray magnetic circular dichroism rules out a ferromagnetic order intrinsic to the monolayer. Our findings provide essential knowledge necessary for understanding this interesting yet less explored metallic monolayer in the emerging family of van der Waals magnets.
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Affiliation(s)
- Ping Kwan Johnny Wong
- Centre for Advanced 2D Materials (CA2DM) and Graphene Research Centre (GRC) , National University of Singapore , 6 Science Drive 2 , Singapore 117546 , Singapore
| | - Wen Zhang
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
| | - Jun Zhou
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
| | - Fabio Bussolotti
- Institute of Materials Research and Engineering (IMRE) , Agency for Science, Technology, and Research (A*Star) , 2 Fusionopolis Way, Innovis , Singapore 138634 , Singapore
| | - Xinmao Yin
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
| | - Lei Zhang
- Centre for Advanced 2D Materials (CA2DM) and Graphene Research Centre (GRC) , National University of Singapore , 6 Science Drive 2 , Singapore 117546 , Singapore
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
| | - Alpha T N'Diaye
- Advanced Light Source (ALS) , Lawrence Berkeley National Laboratory , Berkeley CA94720 , United States
| | - Simon A Morton
- Advanced Light Source (ALS) , Lawrence Berkeley National Laboratory , Berkeley CA94720 , United States
| | - Wei Chen
- Centre for Advanced 2D Materials (CA2DM) and Graphene Research Centre (GRC) , National University of Singapore , 6 Science Drive 2 , Singapore 117546 , Singapore
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
- Department of Chemistry , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
| | - Johnson Goh
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
- Institute of Materials Research and Engineering (IMRE) , Agency for Science, Technology, and Research (A*Star) , 2 Fusionopolis Way, Innovis , Singapore 138634 , Singapore
| | - Michel P de Jong
- NanoElectronics Group, MESA+ Institute for Nanotechnology , University of Twente , P.O. Box 217, 7500 AE , Enschede , The Netherlands
| | - Yuan Ping Feng
- Centre for Advanced 2D Materials (CA2DM) and Graphene Research Centre (GRC) , National University of Singapore , 6 Science Drive 2 , Singapore 117546 , Singapore
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
| | - Andrew T S Wee
- Centre for Advanced 2D Materials (CA2DM) and Graphene Research Centre (GRC) , National University of Singapore , 6 Science Drive 2 , Singapore 117546 , Singapore
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
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9
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Wong PKJ, Zhang W, Bussolotti F, Yin X, Herng TS, Zhang L, Huang YL, Vinai G, Krishnamurthi S, Bukhvalov DW, Zheng YJ, Chua R, N'Diaye AT, Morton SA, Yang CY, Ou Yang KH, Torelli P, Chen W, Goh KEJ, Ding J, Lin MT, Brocks G, de Jong MP, Castro Neto AH, Wee ATS. Evidence of Spin Frustration in a Vanadium Diselenide Monolayer Magnet. Adv Mater 2019; 31:e1901185. [PMID: 30997712 DOI: 10.1002/adma.201901185] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 03/30/2019] [Indexed: 06/09/2023]
Abstract
Monolayer VSe2 , featuring both charge density wave and magnetism phenomena, represents a unique van der Waals magnet in the family of metallic 2D transition-metal dichalcogenides (2D-TMDs). Herein, by means of in situ microscopy and spectroscopic techniques, including scanning tunneling microscopy/spectroscopy, synchrotron X-ray and angle-resolved photoemission, and X-ray absorption, direct spectroscopic signatures are established, that identify the metallic 1T-phase and vanadium 3d1 electronic configuration in monolayer VSe2 grown on graphite by molecular-beam epitaxy. Element-specific X-ray magnetic circular dichroism, complemented with magnetic susceptibility measurements, further reveals monolayer VSe2 as a frustrated magnet, with its spins exhibiting subtle correlations, albeit in the absence of a long-range magnetic order down to 2 K and up to a 7 T magnetic field. This observation is attributed to the relative stability of the ferromagnetic and antiferromagnetic ground states, arising from its atomic-scale structural features, such as rotational disorders and edges. The results of this study extend the current understanding of metallic 2D-TMDs in the search for exotic low-dimensional quantum phenomena, and stimulate further theoretical and experimental studies on van der Waals monolayer magnets.
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Affiliation(s)
- Ping Kwan Johnny Wong
- Centre for Advanced 2D Materials (CA2DM) and Graphene Research Centre (GRC), National University of Singapore, 6 Science Drive 2, Singapore, 117546, Singapore
| | - Wen Zhang
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117542, Singapore
| | - Fabio Bussolotti
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*Star), 2 Fusionopolis Way, Innovis, Singapore, 138634, Singapore
| | - Xinmao Yin
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117542, Singapore
| | - Tun Seng Herng
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore, 117575, Singapore
| | - Lei Zhang
- Centre for Advanced 2D Materials (CA2DM) and Graphene Research Centre (GRC), National University of Singapore, 6 Science Drive 2, Singapore, 117546, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117542, Singapore
| | - Yu Li Huang
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117542, Singapore
| | - Giovanni Vinai
- Instituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Area Science Park, S.S. Km 163.5, Trieste, I-34149, Italy
| | - Sridevi Krishnamurthi
- Computational Materials Science, Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500, AE, Enschede, The Netherlands
| | - Danil W Bukhvalov
- College of Science, Institute of Materials Physics and Chemistry, Nanjing Forestry University, Nanjing, 210037, P. R. China
- Institute of Physics and Technology, Ural Federal University, Mira Street 19, 620002, Yekaterinburg, Russia
| | - Yu Jie Zheng
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117542, Singapore
| | - Rebekah Chua
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117542, Singapore
| | - Alpha T N'Diaye
- Advanced Light Source (ALS), Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Simon A Morton
- Advanced Light Source (ALS), Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Chao-Yao Yang
- Department of Physics, National Taiwan University, Taipei, 10617, Taiwan
| | - Kui-Hon Ou Yang
- Department of Physics, National Taiwan University, Taipei, 10617, Taiwan
| | - Piero Torelli
- Instituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Area Science Park, S.S. Km 163.5, Trieste, I-34149, Italy
| | - Wei Chen
- Centre for Advanced 2D Materials (CA2DM) and Graphene Research Centre (GRC), National University of Singapore, 6 Science Drive 2, Singapore, 117546, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117542, Singapore
- Department of Chemistry, National University of Singapore, 2 Science Drive 3, Singapore, 117542, Singapore
| | - Kuan Eng Johnson Goh
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117542, Singapore
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*Star), 2 Fusionopolis Way, Innovis, Singapore, 138634, Singapore
| | - Jun Ding
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore, 117575, Singapore
| | - Minn-Tsong Lin
- Department of Physics, National Taiwan University, Taipei, 10617, Taiwan
| | - Geert Brocks
- Computational Materials Science, Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500, AE, Enschede, The Netherlands
| | - Michel P de Jong
- NanoElectronics Group, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500, AE, Enschede, The Netherlands
| | - Antonio H Castro Neto
- Centre for Advanced 2D Materials (CA2DM) and Graphene Research Centre (GRC), National University of Singapore, 6 Science Drive 2, Singapore, 117546, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117542, Singapore
| | - Andrew Thye Shen Wee
- Centre for Advanced 2D Materials (CA2DM) and Graphene Research Centre (GRC), National University of Singapore, 6 Science Drive 2, Singapore, 117546, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117542, Singapore
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10
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Schwarze M, Gaul C, Scholz R, Bussolotti F, Hofacker A, Schellhammer KS, Nell B, Naab BD, Bao Z, Spoltore D, Vandewal K, Widmer J, Kera S, Ueno N, Ortmann F, Leo K. Molecular parameters responsible for thermally activated transport in doped organic semiconductors. Nat Mater 2019; 18:242-248. [PMID: 30692647 DOI: 10.1038/s41563-018-0277-0] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Accepted: 12/19/2018] [Indexed: 06/09/2023]
Abstract
Doped organic semiconductors typically exhibit a thermal activation of their electrical conductivity, whose physical origin is still under scientific debate. In this study, we disclose relationships between molecular parameters and the thermal activation energy (EA) of the conductivity, revealing that charge transport is controlled by the properties of host-dopant integer charge transfer complexes (ICTCs) in efficiently doped organic semiconductors. At low doping concentrations, charge transport is limited by the Coulomb binding energy of ICTCs, which can be minimized by systematic modification of the charge distribution on the individual ions. The investigation of a wide variety of material systems reveals that static energetic disorder induced by ICTC dipole moments sets a general lower limit for EA at large doping concentrations. The impact of disorder can be reduced by adjusting the ICTC density and the intramolecular relaxation energy of host ions, allowing an increase of conductivity by many orders of magnitude.
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Affiliation(s)
- Martin Schwarze
- Dresden Integrated Center for Applied Physics and Photonic Materials, Technische Universität Dresden, Dresden, Germany.
| | - Christopher Gaul
- Center for Advancing Electronics Dresden and Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, Germany
| | - Reinhard Scholz
- Dresden Integrated Center for Applied Physics and Photonic Materials, Technische Universität Dresden, Dresden, Germany
| | - Fabio Bussolotti
- Institute for Molecular Science, Department of Photo-Molecular Science, Myodaiji, Okazaki, Aichi, Japan
| | - Andreas Hofacker
- Dresden Integrated Center for Applied Physics and Photonic Materials, Technische Universität Dresden, Dresden, Germany
| | - Karl Sebastian Schellhammer
- Center for Advancing Electronics Dresden and Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, Germany
| | - Bernhard Nell
- Dresden Integrated Center for Applied Physics and Photonic Materials, Technische Universität Dresden, Dresden, Germany
| | - Benjamin D Naab
- Department of Chemical Engineering, Stanford University, Stanford, CA, USA
| | - Zhenan Bao
- Department of Chemical Engineering, Stanford University, Stanford, CA, USA
| | - Donato Spoltore
- Dresden Integrated Center for Applied Physics and Photonic Materials, Technische Universität Dresden, Dresden, Germany
| | - Koen Vandewal
- Dresden Integrated Center for Applied Physics and Photonic Materials, Technische Universität Dresden, Dresden, Germany
- Institute for Materials Research (IMO), Hasselt University, Diepenbeek, Belgium
| | - Johannes Widmer
- Dresden Integrated Center for Applied Physics and Photonic Materials, Technische Universität Dresden, Dresden, Germany
- Heliatek GmbH, Dresden, Germany
| | - Satoshi Kera
- Institute for Molecular Science, Department of Photo-Molecular Science, Myodaiji, Okazaki, Aichi, Japan
| | - Nobuo Ueno
- Graduate School of Advanced Integration Science, Chiba University, Chiba, Japan
| | - Frank Ortmann
- Center for Advancing Electronics Dresden and Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, Germany.
| | - Karl Leo
- Dresden Integrated Center for Applied Physics and Photonic Materials, Technische Universität Dresden, Dresden, Germany.
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11
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Gaul C, Hutsch S, Schwarze M, Schellhammer KS, Bussolotti F, Kera S, Cuniberti G, Leo K, Ortmann F. Insight into doping efficiency of organic semiconductors from the analysis of the density of states in n-doped C 60 and ZnPc. Nat Mater 2018; 17:439-444. [PMID: 29483635 DOI: 10.1038/s41563-018-0030-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 01/23/2018] [Indexed: 06/08/2023]
Abstract
Doping plays a crucial role in semiconductor physics, with n-doping being controlled by the ionization energy of the impurity relative to the conduction band edge. In organic semiconductors, efficient doping is dominated by various effects that are currently not well understood. Here, we simulate and experimentally measure, with direct and inverse photoemission spectroscopy, the density of states and the Fermi level position of the prototypical materials C60 and zinc phthalocyanine n-doped with highly efficient benzimidazoline radicals (2-Cyc-DMBI). We study the role of doping-induced gap states, and, in particular, of the difference Δ1 between the electron affinity of the undoped material and the ionization potential of its doped counterpart. We show that this parameter is critical for the generation of free carriers and influences the conductivity of the doped films. Tuning of Δ1 may provide alternative strategies to optimize the electronic properties of organic semiconductors.
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Affiliation(s)
- Christopher Gaul
- Center for Advancing Electronics Dresden and Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, Germany
| | - Sebastian Hutsch
- Center for Advancing Electronics Dresden and Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, Germany
| | - Martin Schwarze
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, Dresden, Germany
| | - Karl Sebastian Schellhammer
- Center for Advancing Electronics Dresden and Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, Germany
- Institute for Materials Science and Max Bergmann Center for Biomaterials, Technische Universität Dresden, Dresden, Germany
| | - Fabio Bussolotti
- Institute for Molecular Science, Department of Photo-Molecular Science, Myodaiji, Okazaki, Japan
- Institute of Materials Research and Engineering, Agency of Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Satoshi Kera
- Institute for Molecular Science, Department of Photo-Molecular Science, Myodaiji, Okazaki, Japan
| | - Gianaurelio Cuniberti
- Center for Advancing Electronics Dresden and Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, Germany
- Institute for Materials Science and Max Bergmann Center for Biomaterials, Technische Universität Dresden, Dresden, Germany
| | - Karl Leo
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, Dresden, Germany
| | - Frank Ortmann
- Center for Advancing Electronics Dresden and Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, Germany.
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12
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Lim YF, Priyadarshi K, Bussolotti F, Gogoi PK, Cui X, Yang M, Pan J, Tong SW, Wang S, Pennycook SJ, Goh KEJ, Wee ATS, Wong SL, Chi D. Modification of Vapor Phase Concentrations in MoS 2 Growth Using a NiO Foam Barrier. ACS Nano 2018; 12:1339-1349. [PMID: 29338197 DOI: 10.1021/acsnano.7b07682] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Single-layer molybdenum disulfide (MoS2) has attracted significant attention due to its electronic and physical properties, with much effort invested toward obtaining large-area high-quality monolayer MoS2 films. In this work, we demonstrate a reactive-barrier-based approach to achieve growth of highly homogeneous single-layer MoS2 on sapphire by the use of a nickel oxide foam barrier during chemical vapor deposition. Due to the reactivity of the NiO barrier with MoO3, the concentration of precursors reaching the substrate and thus nucleation density is effectively reduced, allowing grain sizes of up to 170 μm and continuous monolayers on the centimeter length scale being obtained. The quality of the monolayer is further revealed by angle-resolved photoemission spectroscopy measurement by observation of a very well resolved electronic band structure and spin-orbit splitting of the bands at room temperature with only two major domain orientations, indicating the successful growth of a highly crystalline and well-oriented MoS2 monolayer.
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Affiliation(s)
- Yee-Fun Lim
- Institute of Materials Research and Engineering, Agency for Science Technology and Research , 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634
| | - Kumar Priyadarshi
- Institute of Materials Research and Engineering, Agency for Science Technology and Research , 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634
- Indian Institute of Science Education and Research , Dr. Homi Bhabha Road, Pashan Pune 411008, India
| | - Fabio Bussolotti
- Institute of Materials Research and Engineering, Agency for Science Technology and Research , 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634
| | - Pranjal Kumar Gogoi
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117542
| | - Xiaoyang Cui
- Institute of Materials Research and Engineering, Agency for Science Technology and Research , 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634
| | - Ming Yang
- Institute of Materials Research and Engineering, Agency for Science Technology and Research , 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634
| | - Jisheng Pan
- Institute of Materials Research and Engineering, Agency for Science Technology and Research , 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634
| | - Shi Wun Tong
- Institute of Materials Research and Engineering, Agency for Science Technology and Research , 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634
| | - Shijie Wang
- Institute of Materials Research and Engineering, Agency for Science Technology and Research , 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634
| | - Stephen J Pennycook
- Department of Materials Science & Engineering, National University of Singapore , 9 Engineering Drive 1, Singapore 117575
| | - Kuan Eng Johnson Goh
- Institute of Materials Research and Engineering, Agency for Science Technology and Research , 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117542
| | - Andrew T S Wee
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117542
| | - Swee Liang Wong
- Institute of Materials Research and Engineering, Agency for Science Technology and Research , 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117542
| | - Dongzhi Chi
- Institute of Materials Research and Engineering, Agency for Science Technology and Research , 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634
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13
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Schwarze M, Naab BD, Tietze ML, Scholz R, Pahner P, Bussolotti F, Kera S, Kasemann D, Bao Z, Leo K. Analyzing the n-Doping Mechanism of an Air-Stable Small-Molecule Precursor. ACS Appl Mater Interfaces 2018; 10:1340-1346. [PMID: 29236472 DOI: 10.1021/acsami.7b14034] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Efficient n-doping of organic semiconductors requires electron-donating molecules with small ionization energies, making such n-dopants usually sensitive to degradation under air exposure. A workaround consists in the usage of air-stable precursor molecules containing the actual n-doping species. Here, we systematically analyze the doping mechanism of the small-molecule precursor o-MeO-DMBI-Cl, which releases a highly reducing o-MeO-DMBI radical upon thermal evaporation. n-Doping of N,N-bis(fluoren-2-yl)-naphthalene tetracarboxylic diimide yields air-stable and highly conductive films suitable for application as electron transport layer in organic solar cells. By photoelectron spectroscopy, we determine a reduced doping efficiency at high doping concentrations. We attribute this reduction to a change of the precursor decomposition mechanism with rising crucible temperature, yielding an undesired demethylation at high evaporation rates. Our results do not only show the possibility of efficient and air-stable n-doping, but also support the design of novel air-stable precursor molecules of strong n-dopants.
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Affiliation(s)
| | - Benjamin D Naab
- Department of Chemical Engineering, Stanford University , Stanford, California 94303, United States
| | | | | | | | - Fabio Bussolotti
- Department of Photo-Molecular Science, Institute for Molecular Science , Myodaiji, Okazaki, Aichi 444-8585, Japan
| | - Satoshi Kera
- Department of Photo-Molecular Science, Institute for Molecular Science , Myodaiji, Okazaki, Aichi 444-8585, Japan
| | | | - Zhenan Bao
- Department of Chemical Engineering, Stanford University , Stanford, California 94303, United States
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14
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Bussolotti F, Chai J, Yang M, Kawai H, Zhang Z, Wang S, Wong SL, Manzano C, Huang Y, Chi D, Goh KEJ. Electronic properties of atomically thin MoS2 layers grown by physical vapour deposition: band structure and energy level alignment at layer/substrate interfaces. RSC Adv 2018; 8:7744-7752. [PMID: 35539107 PMCID: PMC9078486 DOI: 10.1039/c8ra00635k] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Accepted: 02/12/2018] [Indexed: 11/21/2022] Open
Abstract
We present an analysis of the electronic properties of an MoS2 monolayer (ML) and bilayer (BL) as-grown on a highly ordered pyrolytic graphite (HOPG) substrate by physical vapour deposition (PVD), using lab-based angle-resolved photoemission spectroscopy (ARPES) supported by scanning tunnelling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) for morphology and elemental assessments, respectively. Despite the presence of multiple domains (causing in-plane rotational disorder) and structural defects, electronic band dispersions were clearly observed, reflecting the high density of electronic states along the high symmetry directions of MoS2 single crystal domains. In particular, the thickness dependent direct-to-indirect band gap transition previously reported only for MoS2 layers obtained by exfoliation or via epitaxial growth processes, was found to be also accessible in our PVD grown MoS2 samples. At the same time, electronic gap states were detected, and attributed mainly to structural defects in the 2D layers. Finally, we discuss and clarify the role of the electronic gap states and the interlayer coupling in controlling the energy level alignment at the MoS2/substrate interface. The band structure of defective, rotationally disordered 2D TMDC layers is reported.![]()
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Affiliation(s)
- Fabio Bussolotti
- Institute of Materials Research and Engineering
- A*STAR (Agency for Science, Technology and Research)
- Singapore 138634
- Singapore
| | - Jainwei Chai
- Institute of Materials Research and Engineering
- A*STAR (Agency for Science, Technology and Research)
- Singapore 138634
- Singapore
| | - Ming Yang
- Institute of Materials Research and Engineering
- A*STAR (Agency for Science, Technology and Research)
- Singapore 138634
- Singapore
| | - Hiroyo Kawai
- Institute of Materials Research and Engineering
- A*STAR (Agency for Science, Technology and Research)
- Singapore 138634
- Singapore
| | - Zheng Zhang
- Institute of Materials Research and Engineering
- A*STAR (Agency for Science, Technology and Research)
- Singapore 138634
- Singapore
| | - Shijie Wang
- Institute of Materials Research and Engineering
- A*STAR (Agency for Science, Technology and Research)
- Singapore 138634
- Singapore
| | - Swee Liang Wong
- Institute of Materials Research and Engineering
- A*STAR (Agency for Science, Technology and Research)
- Singapore 138634
- Singapore
| | - Carlos Manzano
- Institute of Materials Research and Engineering
- A*STAR (Agency for Science, Technology and Research)
- Singapore 138634
- Singapore
| | - Yuli Huang
- Institute of Materials Research and Engineering
- A*STAR (Agency for Science, Technology and Research)
- Singapore 138634
- Singapore
| | - Dongzhi Chi
- Institute of Materials Research and Engineering
- A*STAR (Agency for Science, Technology and Research)
- Singapore 138634
- Singapore
| | - Kuan Eng Johnson Goh
- Institute of Materials Research and Engineering
- A*STAR (Agency for Science, Technology and Research)
- Singapore 138634
- Singapore
- Department of Physics
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15
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Bussolotti F, Yang J, Yamaguchi T, Yonezawa K, Sato K, Matsunami M, Tanaka K, Nakayama Y, Ishii H, Ueno N, Kera S. Hole-phonon coupling effect on the band dispersion of organic molecular semiconductors. Nat Commun 2017; 8:173. [PMID: 28765525 PMCID: PMC5539254 DOI: 10.1038/s41467-017-00241-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 06/13/2017] [Indexed: 11/09/2022] Open
Abstract
The dynamic interaction between the traveling charges and the molecular vibrations is critical for the charge transport in organic semiconductors. However, a direct evidence of the expected impact of the charge-phonon coupling on the band dispersion of organic semiconductors is yet to be provided. Here, we report on the electronic properties of rubrene single crystal as investigated by angle resolved ultraviolet photoelectron spectroscopy. A gap opening and kink-like features in the rubrene electronic band dispersion are observed. In particular, the latter results in a large enhancement of the hole effective mass (> 1.4), well above the limit of the theoretical estimations. The results are consistent with the expected modifications of the band structures in organic semiconductors as introduced by hole-phonon coupling effects and represent an important experimental step toward the understanding of the charge localization phenomena in organic materials.The charge transport properties in organic semiconductors are affected by the impact of molecular vibrations, yet it has been challenging to quantify them to date. Here, Bussolotti et al. provide direct experimental evidence on the band dispersion modified by molecular vibrations in a rubrene single crystal.
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Affiliation(s)
- F Bussolotti
- Institute for Molecular Science, Myodaiji, Okazaki, 444-8585, Japan. .,Institute of Materials Research and Engineering (IMRE), 2 Fusionopolis Way, Innovis, Singapore, #08-03, Singapore.
| | - J Yang
- Graduate School of Advanced Integration Science, Chiba University, Chiba, 263-8522, Japan.,College of Physical Science and Technology, Yangzhou University, Jiangsu, 225009, People's Republic of China
| | - T Yamaguchi
- Institute for Molecular Science, Myodaiji, Okazaki, 444-8585, Japan.,SOKENDAI (The Graduate University for Advanced Studies), Hayama, Kanagawa, 240-0193, Japan
| | - K Yonezawa
- Institute for Molecular Science, Myodaiji, Okazaki, 444-8585, Japan
| | - K Sato
- Graduate School of Advanced Integration Science, Chiba University, Chiba, 263-8522, Japan
| | - M Matsunami
- Institute for Molecular Science, Myodaiji, Okazaki, 444-8585, Japan.,Toyota Technological Institute, 2-12-1 Hisakata, Tempaku-ku, Nagoya, 468-8511, Japan
| | - K Tanaka
- Institute for Molecular Science, Myodaiji, Okazaki, 444-8585, Japan.,SOKENDAI (The Graduate University for Advanced Studies), Hayama, Kanagawa, 240-0193, Japan
| | - Y Nakayama
- Graduate School of Advanced Integration Science, Chiba University, Chiba, 263-8522, Japan.,Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda-shi, Chiba-ken, 278-8510, Japan
| | - H Ishii
- Graduate School of Advanced Integration Science, Chiba University, Chiba, 263-8522, Japan
| | - N Ueno
- Graduate School of Advanced Integration Science, Chiba University, Chiba, 263-8522, Japan
| | - S Kera
- Institute for Molecular Science, Myodaiji, Okazaki, 444-8585, Japan. .,Graduate School of Advanced Integration Science, Chiba University, Chiba, 263-8522, Japan. .,SOKENDAI (The Graduate University for Advanced Studies), Hayama, Kanagawa, 240-0193, Japan.
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16
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Kirchhuebel T, Gruenewald M, Sojka F, Kera S, Bussolotti F, Ueba T, Ueno N, Rouillé G, Forker R, Fritz T. Self-Assembly of Tetraphenyldibenzoperiflanthene (DBP) Films on Ag(111) in the Monolayer Regime. Langmuir 2016; 32:1981-7. [PMID: 26844381 DOI: 10.1021/acs.langmuir.5b04069] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Tetraphenyldibenzoperiflanthene (DBP) is a promising candidate as a component of highly efficient organic photovoltaic cells and organic light-emitting diodes. The structural properties of thin films of this particular lander-type molecule on Ag(111) were investigated by complementary techniques. Highly ordered structures were obtained, and their mutual alignment was characterized by means of low-energy electron diffraction (LEED). Scanning tunneling microscopy (STM) images reveal two slightly different arrangements within the first monolayer (ML), both describable as specific herringbone patterns with two molecules per unit cell whose dibenzoperiflanthene framework is parallel to the surface. In contrast, single DBP molecules in the second ML were imaged with much higher intramolecular resolution, resembling the shape of the frontier orbitals in the gas phase as calculated by means of density functional theory (DFT). Further deposition leads to the growth of highly ordered bilayer islands on top of the first ML with identical unit cell dimensions and orientation but slightly inclined molecules. This suggests that the first ML acts as a template for the epitaxial growth of further layers. Simultaneously, a significant number of second-layer molecules mainly located at step edges or scattered over narrow terraces do not form highly ordered aggregates.
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Affiliation(s)
- Tino Kirchhuebel
- Institute of Solid State Physics, Friedrich Schiller University Jena , Helmholtzweg 5, 07743 Jena, Germany
| | - Marco Gruenewald
- Institute of Solid State Physics, Friedrich Schiller University Jena , Helmholtzweg 5, 07743 Jena, Germany
| | - Falko Sojka
- Institute of Solid State Physics, Friedrich Schiller University Jena , Helmholtzweg 5, 07743 Jena, Germany
| | - Satoshi Kera
- Institute for Molecular Science , Myodaiji, Okazaki 444-8585, Japan
- SOKENDAI, The Graduate University for Advanced Studies , Okazaki 444-8585, Japan
- Graduate School of Advanced Integration Science, Chiba University , Chiba 263-8522, Japan
| | - Fabio Bussolotti
- Institute for Molecular Science , Myodaiji, Okazaki 444-8585, Japan
| | - Takahiro Ueba
- Institute for Molecular Science , Myodaiji, Okazaki 444-8585, Japan
- SOKENDAI, The Graduate University for Advanced Studies , Okazaki 444-8585, Japan
| | - Nobuo Ueno
- Graduate School of Advanced Integration Science, Chiba University , Chiba 263-8522, Japan
| | - Gaël Rouillé
- Laboratory Astrophysics Group of the Max Planck Institute for Astronomy, Institute of Solid State Physics, Friedrich Schiller University Jena , Helmholtzweg 3, 07743 Jena, Germany
| | - Roman Forker
- Institute of Solid State Physics, Friedrich Schiller University Jena , Helmholtzweg 5, 07743 Jena, Germany
| | - Torsten Fritz
- Institute of Solid State Physics, Friedrich Schiller University Jena , Helmholtzweg 5, 07743 Jena, Germany
- Department of Chemistry, Graduate School of Science and Institute for Academic Initiatives, Osaka University , 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
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18
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Bussolotti F, Kera S, Kudo K, Kahn A, Ueno N. Gap states in pentacene thin film induced by inert gas exposure. Phys Rev Lett 2013; 110:267602. [PMID: 23848923 DOI: 10.1103/physrevlett.110.267602] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Indexed: 06/02/2023]
Abstract
We studied gas-exposure effects on pentacene (Pn) films on SiO2 and Au(111) substrates by ultrahigh sensitivity photoelectron spectroscopy, which can detect the density of states of ∼10(16) states eV-1 cm-3 comparable to electrical measurements. The results show the striking effects for Pn/SiO2: exposure to inert gas (N2 and Ar) produces a sharp rise in gap states from ∼10(16) to ∼10(18) states eV-1 cm-3 and pushes the Fermi level closer to the valence band (0.15-0.17 eV), as does exposure to O2 (0.20 eV), while no such gas-exposure effect is observed for Pn/Au(111). The results demonstrate that these gap states originate from small imperfections in the Pn packing structure, which are induced by gas penetration into the film through the crystal grain boundaries.
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Affiliation(s)
- Fabio Bussolotti
- Department of Nanomaterial Science, Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan.
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19
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Xin Q, Duhm S, Bussolotti F, Akaike K, Kubozono Y, Aoki H, Kosugi T, Kera S, Ueno N. Accessing surface Brillouin zone and band structure of picene single crystals. Phys Rev Lett 2012; 108:226401. [PMID: 23003630 DOI: 10.1103/physrevlett.108.226401] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2012] [Indexed: 06/01/2023]
Abstract
We have experimentally revealed the band structure and the surface Brillouin zone of insulating picene single crystals (SCs), the mother organic system for a recently discovered aromatic superconductor, with ultraviolet photoelectron spectroscopy (UPS) and low-energy electron diffraction with a laser for photoconduction. A hole effective mass of 2.24m(0) and the hole mobility μ(h)≥9.0 cm(2)/V s (298 K) were deduced in the Γ-Y direction. We have further shown that some picene SCs did not show charging during UPS even without the laser, which indicates that pristine UPS works for high-quality organic SCs.
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Affiliation(s)
- Qian Xin
- Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan.
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20
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Bussolotti F, Yamada-Takamura Y, Wang Y, Friedlein R. Structure-dependent band dispersion in epitaxial anthracene films. J Chem Phys 2011; 135:124709. [DOI: 10.1063/1.3643717] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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21
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Friedlein R, Wang Y, Fleurence A, Bussolotti F, Ogata Y, Yamada-Takamura Y. Stacks of Nucleic Acids as Molecular Wires: Direct Measurement of the Intermolecular Band Dispersion in Multilayer Guanine Assemblies. J Am Chem Soc 2010; 132:12808-10. [DOI: 10.1021/ja104839d] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Rainer Friedlein
- School of Materials Science & Research Center for Integrated Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa, 923-1292, Japan.
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Parisse P, Bussolotti F, Passacantando M, Ottaviano L. 3D island growth of 6,13 Pentacenequinone on silicon oxide and gold. Journal of Non-Crystalline Solids 2010. [DOI: 10.1016/j.jnoncrysol.2010.05.071] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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23
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Bussolotti F, Friedlein R. Hybrid interfaces of biological molecules and metals: The prototypical case of adenine on Cu(110). J Chem Phys 2010. [DOI: 10.1063/1.3430743] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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24
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Gargiani P, Izzo MG, Bussolotti F, Betti MG, Achilli S, Trioni MI. Bi ordered phases on Cu(100): Periodic arrays of dislocations influence the electronic properties. J Chem Phys 2010; 132:174706. [DOI: 10.1063/1.3424741] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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25
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Passacantando M, Bussolotti F, Santucci S, Di Bartolomeo A, Giubileo F, Iemmo L, Cucolo AM. Field emission from a selected multiwall carbon nanotube. Nanotechnology 2008; 19:395701. [PMID: 21832602 DOI: 10.1088/0957-4484/19/39/395701] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The electron field emission characteristics of individual multiwalled carbon nanotubes were investigated by a piezoelectric nanomanipulation system operating inside a scanning electron microscopy chamber. The experimental set-up ensures a precise evaluation of the geometric parameters (multiwalled carbon nanotube length and diameter and anode-cathode separation) of the field emission system. For several multiwalled carbon nanotubes, reproducible and quite stable emission current behaviour was obtained, with a dependence on the applied voltage well described by a series resistance modified Fowler-Nordheim model. A turn-on field of ∼30 V µm(-1) and a field enhancement factor of around 100 at a cathode-anode distance of the order of 1 µm were evaluated. Finally, the effect of selective electron beam irradiation on the nanotube field emission capabilities was extensively investigated.
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Affiliation(s)
- M Passacantando
- Dipartimento di Fisica, Università degli Studi dell'Aquila and INFN and CNR-INFM Laboratorio Regionale CASTI, Via Vetoio, 67010 Coppito (AQ), Italy
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Bussolotti F, Grossi V, Santucci S, Lozzi L, Passacantando M. Effect of thermal treatment on morphology and electrical transport properties of carbon nanotubes film. ACTA ACUST UNITED AC 2008. [DOI: 10.1088/1742-6596/100/1/012012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Parisse P, Verna A, Rinaldi M, Bussolotti F, Grossi V, Passacantando M, Nardone M, Santucci S, Ottaviano L. Submicron patterning of a catalyst film by scanning probe nanolithography for a selective chemical vapor deposition of carbon nanotubes. Journal of Applied Physics 2007. [DOI: 10.1063/1.2711144] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Kanjilal A, Bussolotti F, Crispoldi F, Beccari M, Di Castro V, Grazia Betti M, Mariani C. Growth of long range ordered pentacene/benzenethiol/Cu(100) heterostructure. ACTA ACUST UNITED AC 2006. [DOI: 10.1051/jp4:2006132057] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Alagia M, Baldacchini C, Betti MG, Bussolotti F, Carravetta V, Ekström U, Mariani C, Stranges S. Core-shell photoabsorption and photoelectron spectra of gas-phase pentacene: Experiment and theory. J Chem Phys 2005; 122:124305. [PMID: 15836376 DOI: 10.1063/1.1864852] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The C K-edge photoabsorption and 1s core-level photoemission of pentacene (C22H14) free molecules are experimentally measured, and calculated by self-consistent-field and static-exchange approximation ab initio methods. Six nonequivalent C atoms present in the molecule contribute to the C 1s photoemission spectrum. The complex near-edge structures of the carbon K-edge absorption spectrum present two main groups of discrete transitions between 283 and 288 eV photon energy, due to absorption to pi* virtual orbitals, and broader structures at higher energy, involving sigma* virtual orbitals. The sharp absorption structures to the pi* empty orbitals lay well below the thresholds for the C 1s ionizations, caused by strong excitonic and localization effects. We can definitely explain the C K-edge absorption spectrum as due to both final (virtual) and initial (core) orbital effects, mainly involving excitations to the two lowest-unoccupied molecular orbitals of pi* symmetry, from the six chemically shifted C 1s core orbitals.
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Affiliation(s)
- Michele Alagia
- ISMN-CNR, Sez. Roma 1, Piazzale Aldo Moro 5, I-00185 Roma, Italy
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