Abstract
Vacancy engineering of 2H-transition metal dichalcogenides (2H-TMDs) has recently attracted great attention due to its potential to fine-tune the phonon and opto-electric properties of these materials. From a mechanical perspective, this symmetry-breaking process typically reduces the overall crack resistance of the material and adversely affects its reliability. However, vacancies can trigger the formation of heterogeneous phases that synergistically improve fracture properties. In this study, using MoSe2 as an example, we characterize the types and density of vacancies that can emerge under electron irradiation and quantify their effect on fracture. Molecular dynamic (MD) simulations, employing a re-parameterized Tersoff potential capable of accurately capturing bond dissociation and structural phase changes, reveal that isolated transition metal monovacancies or chalcogenide divacancies tend to arrest the crack tip and hence enhance the monolayer toughness. In contrast, isolated chalcogenide monovacancies do not significantly affect toughness. The investigation further reveals that selenium vacancy lines, formed by high electron dose rates, alter the crack propagating direction and lead to multiple crack kinking. Using atomic displacements and virial stresses together with a continuum mapping, displacement, strain, and stress fields are computed to extract mechanistic information, e.g., conditions for crack kinking and size effects in fracture events. The study also reveals the potential of specific defect patterns, “vacancy engineering,” to improve the toughness of 2H-TMDs materials.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 17-32 |
| Number of pages | 16 |
| Journal | Materials Today |
| Volume | 70 |
| DOIs | |
| State | Published - Nov 2023 |
Funding
The authors acknowledge the support of the National Science Foundation, through award CMMI 1953806, Office of Naval Research grant N000142212133, and computational resources provided by the Center of Nanoscale Materials at Argonne National Laboratory, as well as the Quest High Performance Computing Cluster at Northwestern University. Work performed at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility, was supported by the U.S. DOE, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The authors also acknowledge input and extensive discussions with Jeffrey Paci, University of Victoria, Canada. The authors acknowledge the support of the National Science Foundation, through award CMMI 1953806, Office of Naval Research grant N000142212133, and computational resources provided by the Center of Nanoscale Materials at Argonne National Laboratory, as well as the Quest High Performance Computing Cluster at Northwestern University. Work performed at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility, was supported by the U.S. DOE, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The authors also acknowledge input and extensive discussions with Jeffrey Paci, University of Victoria, Canada.
Keywords
- Atomistic-to-continuum mapping
- Crack kinking
- Fracture energy
- Phase transition
- Size effect
- Transition metal dichalcogenide
- Vacancy engineering
ASJC Scopus subject areas
- General Materials Science
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering