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Structural Phase Transformation in Strained Monolayer MoWSe2 Alloy
Amey Apte1, Vidya Kochat1, Pankaj Rajak2
1Department of Materials Science and Nano Engineering , Rice University , Houston , Texas 77005 , United States.
ACS Nano
|February 27, 2018
Summary
This study reveals that 2D molybdenum tungsten diselenide (MoWSe2) alloys exhibit enhanced toughness. Crack propagation in these materials shows unique branching and healing behaviors, improving mechanical resistance compared to unalloyed counterparts.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Two-dimensional (2D) materials possess distinct mechanical properties compared to their bulk forms due to their atomic thinness.
- Understanding the mechanical behavior of alloyed 2D materials is crucial for their application in advanced technologies.
Purpose of the Study:
- To investigate the mechanical properties and crack propagation behavior of 2D molybdenum tungsten diselenide (MoWSe2) precipitation alloys.
- To elucidate the role of nanoscopic MoSe2 and WSe2 regions in the alloy's mechanical response under strain.
Main Methods:
- Chemical vapor deposition (CVD) for growing 2D MoWSe2 alloys.
- In situ local Raman spectroscopy to analyze mechanical strain effects.
- Molecular dynamics (MD) simulations to model crack propagation.
- High-angle annular dark-field (HAADF) imaging for structural analysis.
Main Results:
- Bending strain induced blue-shifts in Raman modes, with stress concentrating near precipitate interfaces, particularly affecting WSe2 modes.
- Crack propagation primarily occurred in MoSe2-rich regions, with MD simulations confirming experimental Raman spectra.
- Simulations showed stress-induced phase transformation (2H to 1T) at crack tips in both MoSe2 and WSe2 regions.
- Observed crack branching and healing in WSe2 indicated increased toughness of the alloyed material.
Conclusions:
- Alloyed 2D MoWSe2 demonstrates enhanced mechanical toughness and crack propagation resistance compared to unalloyed materials.
- The unique interplay between MoSe2 and WSe2 regions governs the material's fracture behavior.
- Phase transformation plays a significant role in the crack tip mechanics of these alloyed 2D materials.
Keywords:
Raman spectroscopymechanical strainingmolecular dynamics simulationstransition-metal dichalcogenidetwo-dimensional materialsMore Related Videos
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