研究目的
To develop a modified transfer technique for integrating atomically thin materials into MEMS to study strain physics and create strain-based devices, specifically achieving strain in monolayer MoS2.
研究成果
The study successfully strained monolayer MoS2 to 1.3% using MEMS, demonstrating a novel transfer technique. This advancement enables future strain-based devices and exploration of strain effects in 2D materials, with potential for improvements in anchoring and strain control.
研究不足
The method has a yield of about 75% for MEMS transfer, with failures due to poor contact. The polymer coating may affect sample properties, and viscoelastic drift complicates measurements. Strain inhomogeneity and Poisson's ratio assumptions introduce uncertainties.
1：Experimental Design and Method Selection:
The study uses a modified transfer technique involving a polymer (PPC) to anchor 2D materials to MEMS devices. Chevron actuators are employed for straining, and Raman and photoluminescence spectroscopy are used to measure strain effects.
2：Sample Selection and Data Sources:
Monolayer MoS2 crystals grown via Chemical Vapor Deposition (CVD) on doped silicon substrates with oxide layers are used.
3：List of Experimental Equipment and Materials:
Equipment includes MEMS devices fabricated using PolyMUMPS process, micromanipulators, Renishaw spectrometer, Argon ion laser, thermal electric cooler, and materials like Poly(propylene carbonate) (PPC).
4：Experimental Procedures and Operational Workflow:
Steps include transfer preparation with strain relief cuts, microstructure suspension using Direct Laser Writing, MEMS transfer with heating, and strain application via Joule heating. Measurements involve Raman and PL spectra collection under varying strains.
5：Data Analysis Methods:
Data is analyzed using Lorentzian fits for peak positions, inverse variance weighted mean for strain calculation, and comparison with literature values for Grüneisen parameters and shear deformation potentials.
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Renishaw spectrometer
1800 line per mm grating
Renishaw
Used for Raman and photoluminescence spectroscopy measurements to analyze strain effects in MoS2.
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Argon ion laser
Used to excite MoS2 films for Raman and PL measurements.
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Thermal electric cooler
Used to cool the copper plate mounting the MEMS dies to manage heat from actuators.
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Micromanipulator
Used for precise positioning during transfer steps, including making strain relief cuts.
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GGB Industries probe tip
T-4-60
GGB Industries
Used to make precise cuts in the transfer polymer (PPC) for strain relief.
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Direct Laser Writing system
Used for high-resolution 3D printing of microstructures for sample suspension.
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MEMS device
Fabricated using PolyMUMPS process
MEMSCAP
Used to apply strain to MoS2 flakes via chevron actuators.
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Poly(propylene carbonate)
PPC
Used as transfer polymer to anchor MoS2 flakes to MEMS, providing mechanical coupling.
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