Effects of lower symmetry and dimensionality on Raman spectra in two-dimensional WSe2
We report the observation and interpretation of new Raman peaks in few-layer tungsten diselenide (WSe2), induced by the reduction of symmetry going from three-dimensional (3D) to two-dimensional (2D). In general, Raman frequencies in 2D materials follow quite closely the frequencies of corresponding...
| Main Authors: | , , , , , , |
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| Format: | Journal Article |
| Language: | English |
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2014
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| Online Access: | https://hdl.handle.net/10356/101719 http://hdl.handle.net/10220/18728 |
| _version_ | 1811683226851213312 |
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| author | Luo, Xin Zhao, Yanyuan Zhang, Jun Toh, Minglin Xiong, Qihua Quek, Su Ying Kloc, Christian |
| author2 | School of Electrical and Electronic Engineering |
| author_facet | School of Electrical and Electronic Engineering Luo, Xin Zhao, Yanyuan Zhang, Jun Toh, Minglin Xiong, Qihua Quek, Su Ying Kloc, Christian |
| author_sort | Luo, Xin |
| collection | NTU |
| description | We report the observation and interpretation of new Raman peaks in few-layer tungsten diselenide (WSe2), induced by the reduction of symmetry going from three-dimensional (3D) to two-dimensional (2D). In general, Raman frequencies in 2D materials follow quite closely the frequencies of corresponding eigenmodes in the bulk. However, while the modes that are Raman active in the bulk are also Raman active in the thin films, the reverse is not always true due to the reduced symmetry in thin films. Here, we predict from group theory and density functional calculations that two intralayer vibrational modes, which are Raman inactive in bulk WSe2 in our experimental configuration become Raman active in thin film WSe2, due to reduced symmetry in thin films. This phenomenon explains the Raman peaks we observe experimentally at ∼310 and 176 cm−1 in thin film WSe2. Interestingly, the bulk B12g mode at ∼310 cm−1 that is Raman inactive can, in fact, be detected in Raman measurements under specific wavelengths of irradiation, suggesting that in this case, crystal symmetry selection rules may be broken due to resonant scattering. Both theory and experiment indicate that the E12g and B12g modes blueshift with decreasing thickness, which we attribute to surface effects. Our results shed light on a general understanding of the Raman/infrared activities of the phonon modes in layered transition metal dichalcogenide materials and their evolution behavior from 3D to 2D. |
| first_indexed | 2024-10-01T04:09:22Z |
| format | Journal Article |
| id | ntu-10356/101719 |
| institution | Nanyang Technological University |
| language | English |
| last_indexed | 2024-10-01T04:09:22Z |
| publishDate | 2014 |
| record_format | dspace |
| spelling | ntu-10356/1017192023-02-28T19:42:15Z Effects of lower symmetry and dimensionality on Raman spectra in two-dimensional WSe2 Luo, Xin Zhao, Yanyuan Zhang, Jun Toh, Minglin Xiong, Qihua Quek, Su Ying Kloc, Christian School of Electrical and Electronic Engineering School of Materials Science & Engineering School of Physical and Mathematical Sciences DRNTU::Science::Physics We report the observation and interpretation of new Raman peaks in few-layer tungsten diselenide (WSe2), induced by the reduction of symmetry going from three-dimensional (3D) to two-dimensional (2D). In general, Raman frequencies in 2D materials follow quite closely the frequencies of corresponding eigenmodes in the bulk. However, while the modes that are Raman active in the bulk are also Raman active in the thin films, the reverse is not always true due to the reduced symmetry in thin films. Here, we predict from group theory and density functional calculations that two intralayer vibrational modes, which are Raman inactive in bulk WSe2 in our experimental configuration become Raman active in thin film WSe2, due to reduced symmetry in thin films. This phenomenon explains the Raman peaks we observe experimentally at ∼310 and 176 cm−1 in thin film WSe2. Interestingly, the bulk B12g mode at ∼310 cm−1 that is Raman inactive can, in fact, be detected in Raman measurements under specific wavelengths of irradiation, suggesting that in this case, crystal symmetry selection rules may be broken due to resonant scattering. Both theory and experiment indicate that the E12g and B12g modes blueshift with decreasing thickness, which we attribute to surface effects. Our results shed light on a general understanding of the Raman/infrared activities of the phonon modes in layered transition metal dichalcogenide materials and their evolution behavior from 3D to 2D. NRF (Natl Research Foundation, S’pore) ASTAR (Agency for Sci., Tech. and Research, S’pore) MOE (Min. of Education, S’pore) Published version 2014-01-28T04:48:09Z 2019-12-06T20:43:16Z 2014-01-28T04:48:09Z 2019-12-06T20:43:16Z 2013 2013 Journal Article Luo, X., Zhao, Y., Zhang, J., Toh, M., Kloc, C., Xiong, Q., et al. (2013). Effects of lower symmetry and dimensionality on Raman spectra in two-dimensional WSe2. Physical review B - condensed matter and materials physics, 88(19), 195313-. https://hdl.handle.net/10356/101719 http://hdl.handle.net/10220/18728 10.1103/PhysRevB.88.195313 en Physical review B - condensed matter and materials physics © 2013 American Physical Society. This paper was published in Physical Review B - Condensed Matter and Materials Physics and is made available as an electronic reprint (preprint) with permission of American Physical Society. The paper can be found at the following official DOI: [http://dx.doi.org/10.1103/PhysRevB.88.195313]. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law. application/pdf |
| spellingShingle | DRNTU::Science::Physics Luo, Xin Zhao, Yanyuan Zhang, Jun Toh, Minglin Xiong, Qihua Quek, Su Ying Kloc, Christian Effects of lower symmetry and dimensionality on Raman spectra in two-dimensional WSe2 |
| title | Effects of lower symmetry and dimensionality on Raman spectra in two-dimensional WSe2 |
| title_full | Effects of lower symmetry and dimensionality on Raman spectra in two-dimensional WSe2 |
| title_fullStr | Effects of lower symmetry and dimensionality on Raman spectra in two-dimensional WSe2 |
| title_full_unstemmed | Effects of lower symmetry and dimensionality on Raman spectra in two-dimensional WSe2 |
| title_short | Effects of lower symmetry and dimensionality on Raman spectra in two-dimensional WSe2 |
| title_sort | effects of lower symmetry and dimensionality on raman spectra in two dimensional wse2 |
| topic | DRNTU::Science::Physics |
| url | https://hdl.handle.net/10356/101719 http://hdl.handle.net/10220/18728 |
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