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Title: Anomalous vibrational modes in few layer WTe 2 revealed by polarized Raman scattering and first-principles calculations

When layered transition-metal dichalcogenides (TMDs) are scaled down from a three- to a two-dimensional geometry, electronic and structural transitions occur, leading to the emergence of properties not usually found in the bulk. Here, we report a systematic Raman study of exfoliated semi-metallic WTe 2 flakes with thickness ranging from few layers down to a single layer. A dramatic change in the Raman spectra occurs between the monolayer and few-layer WTe 2 as a vibrational mode centered at ~86.9 cm -1 in the monolayer splits into two active modes at 82.9 and 89.6 cm -1 in the bilayer. Davydov splitting of these two modes is found in the bilayer, as further evidenced by polarized Raman measurements. Strong angular dependence of Raman modes on the WTe 2 film thickness reflects that the existence of directional interlayer interaction, rather than isotropic van der Waals (vdw) coupling, is playing an essential role affecting the phonon modes, especially in anisotropic 2D WTe 2 material. Therefore, the strong evolution of Raman modes with thickness and polarization direction, can not only be a reliable fingerprint for the determination of the thickness and the crystallographic orientation, but can also be an ideal probe for such strong and directionalmore » interlayer interaction.« less
Authors:
 [1] ;  [2] ; ORCiD logo [3] ;  [1] ;  [1] ; ORCiD logo [2] ;  [1]
  1. Huazhong Univ. of Science and Technology, Wuhan (China)
  2. Rensselaer Polytechnic Inst., Troy, NY (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
2D Materials
Additional Journal Information:
Journal Volume: 4; Journal Issue: 3; Journal ID: ISSN 2053-1583
Publisher:
IOP Publishing
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE
OSTI Identifier:
1376514

Cao, Yan, Sheremetyeva, Natalya, Liang, Liangbo, Yuan, Hui, Zhong, Tingting, Meunier, Vincent, and Pan, Minghu. Anomalous vibrational modes in few layer WTe2 revealed by polarized Raman scattering and first-principles calculations. United States: N. p., Web. doi:10.1088/2053-1583/aa7f5a.
Cao, Yan, Sheremetyeva, Natalya, Liang, Liangbo, Yuan, Hui, Zhong, Tingting, Meunier, Vincent, & Pan, Minghu. Anomalous vibrational modes in few layer WTe2 revealed by polarized Raman scattering and first-principles calculations. United States. doi:10.1088/2053-1583/aa7f5a.
Cao, Yan, Sheremetyeva, Natalya, Liang, Liangbo, Yuan, Hui, Zhong, Tingting, Meunier, Vincent, and Pan, Minghu. 2017. "Anomalous vibrational modes in few layer WTe2 revealed by polarized Raman scattering and first-principles calculations". United States. doi:10.1088/2053-1583/aa7f5a. https://www.osti.gov/servlets/purl/1376514.
@article{osti_1376514,
title = {Anomalous vibrational modes in few layer WTe2 revealed by polarized Raman scattering and first-principles calculations},
author = {Cao, Yan and Sheremetyeva, Natalya and Liang, Liangbo and Yuan, Hui and Zhong, Tingting and Meunier, Vincent and Pan, Minghu},
abstractNote = {When layered transition-metal dichalcogenides (TMDs) are scaled down from a three- to a two-dimensional geometry, electronic and structural transitions occur, leading to the emergence of properties not usually found in the bulk. Here, we report a systematic Raman study of exfoliated semi-metallic WTe2 flakes with thickness ranging from few layers down to a single layer. A dramatic change in the Raman spectra occurs between the monolayer and few-layer WTe2 as a vibrational mode centered at ~86.9 cm-1 in the monolayer splits into two active modes at 82.9 and 89.6 cm-1 in the bilayer. Davydov splitting of these two modes is found in the bilayer, as further evidenced by polarized Raman measurements. Strong angular dependence of Raman modes on the WTe2 film thickness reflects that the existence of directional interlayer interaction, rather than isotropic van der Waals (vdw) coupling, is playing an essential role affecting the phonon modes, especially in anisotropic 2D WTe2 material. Therefore, the strong evolution of Raman modes with thickness and polarization direction, can not only be a reliable fingerprint for the determination of the thickness and the crystallographic orientation, but can also be an ideal probe for such strong and directional interlayer interaction.},
doi = {10.1088/2053-1583/aa7f5a},
journal = {2D Materials},
number = 3,
volume = 4,
place = {United States},
year = {2017},
month = {8}
}