title: Atomically Sharp Crack Tips in Monolayer MoS2and Their Enhanced Toughness by Vacancy Defects.
abstract: We combine in situ transmission electron microscopy and large-scale molecular dynamics simulations to investigate brittle fracture in 2D monolayer MoS2, revealing that cracks propagate with a tip of atomic sharpness through the preferential direction with least energy release. We find that sparse vacancy defects cause crack deflections, while increasing defect density shifts the fracture mechanism from brittle to ductile by the migration of vacancies in the strain fields into networks. The fracture toughness of defective MoS2is found to exceed that of graphene due to interactions between the atomically sharp crack tips and vacancy clusters during propagation. These results show that monolayer 2D materials are ideal for revealing fundamental aspects of fracture mechanics not previously possible with thicker materials, similar to studies of dislocation behavior in 2D materials.
authors.affiliation: Department of Materials, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom.
authors.forename: Shanshan
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Civil and Environmental Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Zhao
authors.initials: Z
authors.lastname: Qin
authors.affiliation: Department of Civil and Environmental Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Gang Seob
authors.initials: GS
authors.lastname: Jung
authors.affiliation: Department of Civil and Environmental Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Martin-Martinez
authors.affiliation: Department of Civil and Environmental Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Kristine
authors.initials: K
authors.lastname: Zhang
authors.affiliation: Department of Civil and Environmental Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Markus J
authors.initials: MJ
authors.lastname: Buehler
authors.affiliation: Department of Materials, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom.
authors.forename: Jamie H
authors.initials: JH
authors.lastname: Warner
keywords: 2D materials; MoS2; crack tips; fracture