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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] [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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Chen L, Cheng Z, He S, Zhang X, Deng K, Zong D, Wu Z, Xia M. Large-area single-crystal TMD growth modulated by sapphire substrates. NANOSCALE 2024; 16:978-1004. [PMID: 38112240 DOI: 10.1039/d3nr05400d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2023]
Abstract
Transition metal dichalcogenides (TMDs) have recently attracted extensive attention due to their unique physical and chemical properties; however, the preparation of large-area TMD single crystals is still a great challenge. Chemical vapor deposition (CVD) is an effective method to synthesize large-area and high-quality TMD films, in which sapphires as suitable substrates play a crucial role in anchoring the source material, promoting nucleation and modulating epitaxial growth. In this review, we provide an insightful overview of different epitaxial mechanisms and growth behaviors associated with the atomic structure of sapphire surfaces and the growth parameters. First, we summarize three epitaxial growth mechanisms of TMDs on sapphire substrates, namely, van der Waals epitaxy, step-guided epitaxy, and dual-coupling-guided epitaxy. Second, we introduce the effects of polishing, cutting, and annealing processing of the sapphire surface on the TMD growth. Finally, we discuss the influence of other growth parameters, such as temperature, pressure, carrier gas, and substrate position, on the growth kinetics of TMDs. This review might provide deep insights into the controllable growth of large-area single-crystal TMDs on sapphires, which will propel their practical applications in high-performance nanoelectronics and optoelectronics.
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Affiliation(s)
- Lina Chen
- Department of Applied Physics, School of Physics, Xi'an Jiaotong University, 710049, People's Republic of China.
| | - Zhaofang Cheng
- Department of Applied Physics, School of Physics, Xi'an Jiaotong University, 710049, People's Republic of China.
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi'an Jiaotong University, 710049, People's Republic of China
| | - Shaodan He
- Department of Applied Physics, School of Physics, Xi'an Jiaotong University, 710049, People's Republic of China.
| | - Xudong Zhang
- Department of Applied Physics, School of Physics, Xi'an Jiaotong University, 710049, People's Republic of China.
| | - Kelun Deng
- Department of Applied Physics, School of Physics, Xi'an Jiaotong University, 710049, People's Republic of China.
| | - Dehua Zong
- Department of Applied Physics, School of Physics, Xi'an Jiaotong University, 710049, People's Republic of China.
| | - Zipeng Wu
- Department of Applied Physics, School of Physics, Xi'an Jiaotong University, 710049, People's Republic of China.
| | - Minggang Xia
- Department of Applied Physics, School of Physics, Xi'an Jiaotong University, 710049, People's Republic of China.
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi'an Jiaotong University, 710049, People's Republic of China
- Shaanxi Province Key Laboratory of Quantum Information and Optoelectronic Quantum Devices, School of Physics, Xi'an Jiaotong University, 710049, People's Republic of China
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