title: Unravelling orientation distribution and merging behavior of monolayer MoS2 domains on sapphire.
abstract: Monolayer MoS2 prepared by chemical vapor deposition (CVD) has a highly polycrystalline nature largely because of the coalescence of misoriented domains, which severely hinders its future applications. Identifying and even controlling the orientations of individual domains and understanding their merging behavior therefore hold fundamental significance. In this work, by using single-crystalline sapphire (0001) substrates, we designed the CVD growth of monolayer MoS2 triangles and their polycrystalline aggregates for such purposes. The obtained triangular MoS2 domains on sapphire were found to distributively align in two directions, which, as supported by density functional theory calculations, should be attributed to the relatively small fluctuations of the interface binding energy around the two primary orientations. Using dark-field transmission electron microscopy, we further imaged the grain boundaries of the aggregating domains and determined their prevalent armchair crystallographic orientations with respect to the adjacent MoS2 lattice. The coalescence of individual triangular flakes governed by unique kinetic processes is proposed for the polycrystal formation. These findings are expected to shed light on the controlled MoS2 growth toward predefined domain orientation and large domain size, thus enabling its versatile applications in next-generation nanoelectronics and optoelectronics.
authors.affiliation: Center for Nanochemistry (CNC), Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Academy for Advanced Interdisciplinary Studies, ‡Department of Materials Science and Engineering, College of Engineering, §Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, and ∥Center for Applied Physics and Technology, Peking University , Beijing 100871, People's Republic of China.
authors.forename: Qingqing
authors.initials: Q
authors.lastname: Ji
authors.forename: Min
authors.initials: M
authors.lastname: Kan
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yao
authors.initials: Y
authors.lastname: Guo
authors.forename: Donglin
authors.initials: D
authors.lastname: Ma
authors.forename: Jianping
authors.initials: J
authors.lastname: Shi
authors.forename: Qiang
authors.initials: Q
authors.lastname: Sun
authors.forename: Qing
authors.initials: Q
authors.lastname: Chen
authors.forename: Yanfeng
authors.initials: Y
authors.lastname: Zhang
authors.forename: Zhongfan
authors.initials: Z
authors.lastname: Liu
keywords: Molybdenum disulfide; chemical vapor deposition; controllable synthesis; grain boundary; polycrystallinity