Growth of Monolayer MoS 2 on Hydrophobic Substrates as a Novel and Feasible Method to Prevent the Ambient Degradation of
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MRS Advances © 2020 Materials Research Society DOI: 10.1557/adv.2020.292
Growth of Monolayer MoS2 on Hydrophobic Substrates as a Novel and Feasible Method to Prevent the Ambient Degradation of Monolayer MoS2 Kevin Yao, Dave Banerjee, John D. Femi-Oyetoro, Evan Hathaway, Yan Jiang, Brian Squires, Daniel C. Jones, Arup Neogi, Jingbiao Cui, Usha Philipose, Aryan Agarwal, Ernest Lu, Steven Yao, Mihir Khare, Ibikunle A. Ojo, Gage Marshall, and Jose Perez Department of Physics, University of North Texas, Denton, TX 76203, United States
Monolayer (ML) molybdenum disulfide (MoS ₂) is a novel 2-dimensional (2D) semiconductor whose properties have many applications in devices. Despite its potential, ML MoS₂ is limited in its use due to its degradation under exposure to ambient air. Therefore, studies of possible degradation prevention methods are important. It is well established that air humidity plays a major role in the degradation. In this paper, we investigate the effects of substrate hydrophobicity on the degradation of chemical vapor deposition (CVD) grown ML MoS2. We use optical microscopy, atomic force microscopy (AFM), and Raman mapping to investigate the degradation of ML MoS 2 grown on SiO2 and Si3N4 that are hydrophilic and hydrophobic substrates, respectively. Our results show that the degradation of ML MoS₂ on Si3N4 is significantly less than the degradation on SiO2. These results show that using hydrophobic substrates to grow 2D transition metal dichalcogenide ML materials may diminish ambient degradation and enable improved protocols for device manufacturing.
INTRODUCTION: In recent years, 2-dimensional transition metal dichalcogenides (2D TMDs) have been studied extensively for applications in next-generation electronics and optoelectronics [1]. Specifically, monolayer (ML) MoS2, a 2D TMD, is of special interest due to its direct band gap and large spin-orbit coupling [1]. However, there have been 1
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numerous studies that show that these materials degrade after about a year of ambient air exposure at room temperature (RT) [2-7], which may be a large impediment to their realization in practical applications. Ambient air degradation affects most 2D materials [8], so it is of interest to determine feasible methods of degradation prevention. In the case of MoS2, reports have shown that sulfur vacancies in the films and water vapor in the air play important roles in the degradation [2-7]. In addition, it has been reported that the degradation of MoS2 is a photo-induced effect, since degradation is not observed in samples that are kept in the dark [4]. Photoinduced degradation in the presence of water vapor and oxygen has also been reported for black phosphorus (BP) [9]. For MoS 2 and BP, the role of humidity in the degradation is believed to involve the liquefication of oxides that leav
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