Single and Few-Layer MoS 2 : CVD Synthesis, Transference, and Photodetection Application
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Single and Few-Layer MoS2: CVD Synthesis, Transference, and Photodetection Application Gustavo A. Saenz, Carlos de Anda Orea, Anupama B. Kaul* Electrical and Computer Engineering Department, University of Texas, El Paso, TX 79968, U.S.A * E-mail: [email protected] ABSTRACT Two-dimensional layered materials, materials with weak out-of-plane van der Waals bonding and strong in-plane covalent bonding, have attracted special attention in recent years since the isolation and characterization of monolayer graphite, the graphene. The electrical bandgap in Transition Metal Di-Chalcogenides (TMDCs), non-existent in graphene, make them a good alternative family of materials for novel electronic and optoelectronic applications. 2HMoS2, one of the most stable TMDCs, has been extensively studied, including the synthesis methods, and its potential applications in photodetection. The chemical vapor deposition (CVD) synthesis method has increased its potential over the years. The advantages of this method are scalability compared to micromechanical exfoliation, common process used in research laboratories, and the maintenance of the quality and intrinsic properties of the material compared to the liquid exfoliation methods. In this work, we synthesized high quality pristine 2H-MoS2 via atmospheric pressure chemical vapor deposition (APCVD) by vapor phase reaction of MoO 3 and S powder precursors. The samples were characterized via Raman and photoluminescence (PL) spectroscopy and compared to mechanically exfoliated MoS2 crystal by measuring the full-width half maxima (FWHM) of monolayer and few-layer mesoscopic flakes. In addition, the CVD synthesized single and few-layered MoS2 domains were transferred to different substrates using a high yield process, including a flexible substrate, preserving the quality of the material. Finally, and mechanically exfoliated MoS2 two-terminal photodetector was designed, fabricated, and measured. Demonstrating thus the capability of heterostructure fabrication and the quality of our synthesis and device fabrication process.
INTRODUCTION Two-dimensional layered materials have attracted special attention in the last decade due to their outstanding properties for potential new applications [1]. They consists in weak out-ofplane van der Waals bonding and strong in-plane covalent bonding, allowing synthesis methods such as liquid and mechanical exfoliation, the latter only feasible for research laboratories. One family of 2D layered materials are the Transition Metal Di-Chalcogenides (TMDCs), which were the breakthrough for layered materials beyond graphene, especially the MoS2, one of the most stable TMDCs [2]. 2H-MoS2 consists in triangular prismatic arrangement of Mo plane interceding between two S atomic planes. In addition to the liquid and mechanical exfoliation, various vapor based synthesis approaches have been studied due to the scalability potential and the defect free synthesis process, allowing a single layer growth. The high quality synthesis approaches include the vapor phase reaction by C
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