title: Shape-Dependent Defect Structures of Monolayer MoS2Crystals Grown by Chemical Vapor Deposition.
abstract: Monolayer MoS2crystals with tailored morphologies have been shown to exhibit shape-dependent properties and thus have potential applications in building nanodevices. However, a deep understanding of the relationship between the shape and defect structures in monolayer MoS2is yet elusive. Monolayer MoS2crystals in polygonal shapes, including triangle, tetragon, pentagon, and hexagon, are grown using the chemical vapor deposition technique. Compared with other shapes, the hexagon MoS2crystal contains more electron-donor defects that are mainly due to sulfur vacancies. In the triangular shapes, the defects are mainly distributed at the vertices of the shapes while they are located at the center of hexagonal shapes. On the basis of the Coulomb interaction of exciton and trion, quantitative calculations demonstrate a high electron density (∼1012/cm2) and high Fermi level (EC- EF= 15 meV) for hexagonal shape at room temperature, compared to triangular shapes (∼1011/cm2, EC- EF≈ 30 meV). These findings verify that a much higher number of donor-like sulfur vacancies are formed in hexagonal MoS2shapes. This property allows more electrons or trions to localize in such sites through the physical/chemical adsorption of O2/H2O, which results in a strong enhancement of the light emission efficiency in the hexagonal crystal. The findings provide a better understanding of the formation of shape-dependent defect structures of monolayer MoS2crystals and are inspiring for applications in fabricating nanoelectronic and optoelectronic devices through defect engineering.
authors.affiliation: Department of Materials Science and Engineering, and Shenzhen Key Laboratory of Nanoimprint Technology, South University of Science and Technology , Shenzhen 518055, P. R. China.
authors.forename: Guozhu
authors.initials: G
authors.lastname: Zhang
authors.affiliation: Department of Materials Science and Engineering, and Shenzhen Key Laboratory of Nanoimprint Technology, South University of Science and Technology , Shenzhen 518055, P. R. China.
authors.forename: Jingwei
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Physics and Center for 1D/2D Quantum Materials, The Hong Kong University of Science and Technology , Clear Water Bay, Kowloon, Hong Kong, P. R. China.
authors.forename: Zefei
authors.initials: Z
authors.lastname: Wu
authors.affiliation: Department of Materials Science and Engineering, and Shenzhen Key Laboratory of Nanoimprint Technology, South University of Science and Technology , Shenzhen 518055, P. R. China.
authors.forename: Run
authors.initials: R
authors.lastname: Shi
authors.affiliation: Department of Materials Science and Engineering, and Shenzhen Key Laboratory of Nanoimprint Technology, South University of Science and Technology , Shenzhen 518055, P. R. China.
authors.forename: Wenkai
authors.initials: W
authors.lastname: Ouyang
authors.affiliation: Center for Infrastructure Engineering, Western Sydney University , Kingswood, NSW 2751, Australia.
authors.forename: Abbas
authors.initials: A
authors.lastname: Amini
authors.affiliation: Department of Materials Science and Engineering, and Shenzhen Key Laboratory of Nanoimprint Technology, South University of Science and Technology , Shenzhen 518055, P. R. China.
authors.forename: Bananakere Nanjegowda
authors.initials: BN
authors.lastname: Chandrashekar
authors.affiliation: Department of Physics and Center for 1D/2D Quantum Materials, The Hong Kong University of Science and Technology , Clear Water Bay, Kowloon, Hong Kong, P. R. China.
authors.forename: Ning
authors.identifier: http://orcid.org/0000-0002-4902-5589
authors.initials: N
authors.lastname: Wang
authors.affiliation: Department of Materials Science and Engineering, and Shenzhen Key Laboratory of Nanoimprint Technology, South University of Science and Technology , Shenzhen 518055, P. R. China.
authors.forename: Chun
authors.identifier: http://orcid.org/0000-0001-5976-3457
authors.initials: C
authors.lastname: Cheng
keywords: chemical vapor deposition; defect structures; excitons; monolayer MoS2; shape; transition-metal chalcogenides; trions