A Reactive Molecular Dynamics Study of Atomistic Mechanisms During Synthesis of MoS 2 Layers by Chemical Vapor Depositio
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.67
A Reactive Molecular Dynamics Study of Atomistic Mechanisms During Synthesis of MoS2 Layers by Chemical Vapor Deposition Sungwook Hong, Aravind Krishnamoorthy, Chunyang Sheng, Rajiv K. Kalia, Aiichiro Nakano, Priya Vashishta Collaboratory for Advanced Computing and Simulations, Department of Physics & Astronomy, Department of Computer Science, Department of Chemical Engineering & Materials Science, and Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-0242, USA
ABSTRACT
Transition metal dichalcogenide (TMDC) monolayers like MoS 2 are promising materials for future electronic applications. Large-area monolayer MoS2 samples for these applications are typically synthesized by chemical vapor deposition (CVD) using MoO3 reactants and gasphase sulfur precursors. Recent experimental studies have greatly improved our understanding of reaction pathways in the CVD growth process. However, atomic mechanisms of sulfidation process remain to be fully elucidated. In this work, we present quantum-mechanically informed and validated reactive molecular dynamics (RMD) simulations for CVD synthesis of MoS2 layers using S2 precursors. Our RMD simulations clarify atomic-level reaction pathways for the sulfidation of MoO3 surfaces by S2, which is a critical reaction step for CVD synthesis of MoS2 layers. These results provide a better understanding of the sulfidation process for the scalable synthesis of defect-free MoS2 and other TMDC materials.
INTRODUCTION Layered transition metal dichalcogenide (TMDC) materials have unique physical and chemical properties, compared to their bulk phases [1]. This is mainly due to the quantum confinement and lack of interlayer interaction [2]. Among possible layered TMDC materials available in nature, mono-layered MoS2 has been widely studied for next-generation electronic devices, primarily due to larger bandgaps and higher mobility, when compared with conventional Si-based systems [3, 4]. Monolayered MoS2 is effectively and efficiently synthesized on a target substrate by means of chemical vapor deposition (CVD) [5]. Many efforts have been made to investigate CVD synthesis of high-quality MoS2 layers by MoO3 reactants and sulfur precursors. On the basis of previous studies, a qualitative reaction process for CVD synthesis has been generally understood; sulfidation of MoO3 reactants is a critical reaction step for CVD synthesis of MoS2 layers, and the replacement of O atoms in MoO3 reactants with S atoms in sulfur precursor is the key to synthesizing MoS2 layers [6–10]. However, detailed information on reaction mechanisms for interactions between MoO3 and sulfur precursors has remained to be fully elucidated. These
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