Abstract
Characterization of strain in two-dimensional (2D) crystals is important for understanding their properties and performance. Using first-principles calculations, we study the effects of uniaxial strain on the Raman-active modes in monolayer . We show that the in-plane mode at 384 and the out-of-plane mode at 403 can serve as fingerprints for the uniaxial strain in this 2D material. Specifically, under a uniaxial strain, the doubly degenerate mode splits into two nondegenerate modes: one is the mode in which atoms vibrate in parallel to the strain direction, and the other is the mode in which atoms vibrate perpendicular to the strain direction. The frequency of the mode blueshifts for a compressive strain, but redshifts for a tensile strain. In addition, due to the strain-induced anisotropy in the lattice, the polarized Raman spectra of the and modes exhibit distinct angular dependence for specific laser polarization setups, allowing for a precise determination of the direction of the uniaxial strain with respect to the crystallographic orientation. Furthermore, we find that the polarized Raman intensity of the mode also shows evident dependence on the applied strain, providing additional effective clues for determining the direction of the strain even without knowledge of the crystallographic orientation. Thus, polarized Raman spectroscopy offers an efficient nondestructive way to characterize the uniaxial strains in monolayer .
2 More- Received 4 November 2015
- Revised 8 January 2016
DOI:https://doi.org/10.1103/PhysRevB.93.075401
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