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Ultralow-Frequency Tip-Enhanced Raman Scattering Discovers Nanoscale Radial Breathing Mode on Strained 2D
Mao-Feng Cao1, Xiao-Hui Peng1, Xiao-Jiao Zhao1
1State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.
Advanced Materials (Deerfield Beach, Fla.)
|July 15, 2024
Summary
Researchers discovered a new ultralow-frequency vibration, the radial breathing mode (RBM), in strained van der Waals materials. This finding enables nanoscale strain mapping in 2D semiconductors using tip-enhanced Raman spectroscopy.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Nanotechnology
Background:
- Collective excitations like plasmons and magnons are key in van der Waals materials.
- Nanoscale strain significantly alters material properties and can create quantum emitters.
- The impact of nanoscale strain on collective excitations in these materials is not well understood.
Purpose of the Study:
- To investigate how nanoscale strain affects collective excitations in 2D semiconductors.
- To develop a method for probing localized collective excitations with high spatial resolution.
- To establish a correlation between nanoscale strain and vibrational modes in van der Waals materials.
Main Methods:
- Development of ultralow-frequency tip-enhanced Raman spectroscopy (TERS) with sub-10 nm resolution.
- Simultaneous nanoindentation and TERS measurements on monolayer MoSe2.
- Characterization of localized vibrational modes in curved 2D materials.
Main Results:
- Discovery of a new vibrational mode, the radial breathing mode (RBM), at ~12 cm-1 (0.36 THz) in monolayer MoSe2 nanobubbles.
- Established a direct correlation between RBM frequency and applied nanoscale strain.
- Demonstrated the presence of RBM in curved monolayer WSe2 and bilayer MoSe2.
- Successfully mapped nanoscale strain in monolayer MoSe2 using RBM frequency.
Conclusions:
- Ultralow-frequency RBM in curved van der Waals materials offers a novel approach to study nanoscale strain.
- This technique provides a new pathway for discovering localized collective excitations at the nanoscale.
- The findings advance the understanding of strain effects in 2D materials and their potential applications.
