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Published on: August 28, 2018
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Strain relaxation in monolayer MoS2 over flexible substrate.
Nilanjan Basu1,2, Ravindra Kumar1,2, D Manikandan1,2,3
1Department of Physics, Indian Institute of Technology Madras Chennai 600 036 India pramoda.iitm@gmail.com praveen.bhallamudi@iitm.ac.in.
RSC Advances
|June 2, 2023
Summary
Monolayer molybdenum disulfide (MoS2) relaxes under strain by forming cracks. This study reveals how these cracks form and propagate in MoS2 flakes under uniaxial strain.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Monolayer molybdenum disulfide (MoS2) is a key 2D material with promising electronic and optical properties.
- Understanding its mechanical behavior, including strain relaxation, is crucial for device applications.
- Previous studies have explored MoS2 properties but detailed strain relaxation mechanisms remain an active area of research.
Purpose of the Study:
- To investigate the mechanism of uniaxial strain relaxation in monolayer MoS2 flakes.
- To characterize the formation and evolution of cracks under varying strain levels.
- To provide insights into the mechanical limits and failure modes of 2D materials.
Main Methods:
- Chemical vapor deposition (CVD) growth of monolayer MoS2.
- Transfer of MoS2 flakes onto flexible PET and PDMS substrates.
- Application of controlled uniaxial strain (1-6%).
- In situ optical microscopy and ex situ atomic force microscopy (AFM) for crack imaging.
- Raman and photoluminescence (PL) spectroscopy for strain analysis.
- Finite element simulations for strain distribution analysis.
Main Results:
- Monolayer MoS2 exhibits strain relaxation primarily through crack formation under uniaxial strain.
- Large, micron-scale cracks form along the strain axis at higher strain levels (4-6%).
- Smaller, lateral cracks also develop as a consequence of strain relaxation.
- Raman and PL spectroscopy confirm strain relaxation in the 4-6% strain regime.
- Finite element simulations provide quantitative estimates of strain efficiency and distribution.
Conclusions:
- Uniaxial strain in monolayer MoS2 is effectively relaxed via crack propagation.
- The study elucidates the crack formation dynamics contributing to strain dissipation.
- Findings are essential for designing robust MoS2-based electronic and optoelectronic devices.
- This work lays the foundation for studying strain relaxation in other transition metal dichalcogenides (TMDCs) and their heterostructures.
