Please use this identifier to cite or link to this item: https://hdl.handle.net/10356/101642
Title: Anomalous frequency trends in MoS2 thin films attributed to surface effects
Authors: Luo, Xin
Zhao, Yanyuan
Zhang, Jun
Xiong, Qihua
Quek, Su Ying
Keywords: DRNTU::Science::Physics
Issue Date: 2013
Source: Luo, X., Zhao, Y., Zhang, J., Xiong, Q., & Quek, S. Y. (2013). Anomalous frequency trends in MoS2 thin films attributed to surface effects. Physical review B, 88(7), 075320-.
Series/Report no.: Physical review B
Abstract: The layered dichalcogenide MoS2 has many unique physical properties in low dimensions. Recent experimental Raman spectroscopies report an anomalous blue shift of the in-plane E12g mode with decreasing thickness, a trend that is not understood. Here, we combine experimental Raman scattering and theoretical studies to clarify and explain this trend. Special attention is given to understanding the surface effect on Raman frequencies by using a force constants model based on first-principles calculations. Surface effects refer to the larger Mo-S force constants at the surface of thin film MoS2, which results from a loss of neighbours in adjacent MoS2 layers. Without surface effects, the frequencies of both out-of-plane A1g and in-plane E12g modes decrease with decreasing thickness. However, the E12g mode blue shifts while the A1g mode red shifts once the surface effect is included, in agreement with the experiment. Our results show that competition between the thickness effect and the surface effect determines the mechanical properties of two-dimensional MoS2, which we believe applies to other layered materials.
URI: https://hdl.handle.net/10356/101642
http://hdl.handle.net/10220/18747
DOI: http://dx.doi.org/10.1103/PhysRevB.88.075320
Rights: © 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.88.075320].  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.
metadata.item.grantfulltext: open
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