Photonics Research, 2019, 7 (12): 12001416, Published Online: Nov. 14, 2019
Direct observation of interlayer coherent acoustic phonon dynamics in bilayer and few-layer PtSe2 Download: 801次
Abstract
This work reports the real-time observation of the interlayer lattice vibrations in bilayer and few-layer by means of the coherent phonon method. The layer-breathing mode and standing wave mode of the interlayer vibrations are found to coexist in such a kind of group-10 transition metal dichalcogenides (TMDCs). The interlayer breathing force constant standing for perpendicular coupling (per effective atom) is derived as 7.5 N/m, 2.5 times larger than that of graphene. The interlayer shearing force constant is comparable to the interlayer breathing force constant, which indicates that has nearly isotropic interlayer coupling. The low-frequency Raman spectroscopy elucidates the polarization behavior of the layer-breathing mode that is assigned to have symmetry. The standing wave mode shows redshift with the increasing number of layers, which successfully determines the out-of-plane sound velocity of experimentally. Our results manifest that the coherent phonon method is a good tool to uncover the interlayer lattice vibrations, beyond the conventional Raman spectroscopy limit. The strong interlayer interaction in group-10 TMDCs reveals their promising potential in high-frequency ( ) micro-mechanical resonators.
Xin Chen, Saifeng Zhang, Lei Wang, Yi-Fan Huang, Huiyan Liu, Jiawei Huang, Ningning Dong, Weimin Liu, Ivan M. Kislyakov, Jean Michel Nunzi, Long Zhang, Jun Wang. Direct observation of interlayer coherent acoustic phonon dynamics in bilayer and few-layer PtSe2[J]. Photonics Research, 2019, 7(12): 12001416.