Dynamical observations on the crack tip zone and stress corrosion of two-dimensional MoS<sub>2</sub>.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 28098140.
- Also identified by DOI 10.1038/ncomms14116 and PMC identifier 5253633.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Whether and how fracture mechanics needs to be modified for small length scales and in systems of reduced dimensionality remains an open debate. Here, employing in situ transmission electron microscopy, atomic structures and dislocation dynamics in the crack tip zone of a propagating crack in two-dimensional (2D) monolayer MoS<sub>2</sub> membrane are observed, and atom-to-atom displacement mapping is obtained. The electron beam is used to initiate the crack; during in situ observation of crack propagation the electron beam effect is minimized. The observed high-frequency emission of dislocations is beyond previous understanding of the fracture of brittle MoS<sub>2</sub>. Strain analysis reveals dislocation emission to be closely associated with the crack propagation path in nanoscale. The critical crack tip plastic zone size of nearly perfect 2D MoS<sub>2</sub> is between 2 and 5 nm, although it can grow to 10 nm under corrosive conditions such as ultraviolet light exposure, showing enhanced dislocation activity via defect generation.