Determination of Crystal Axes in Semimetallic T′‐MoTe2 by Polarized Raman Spectroscopy

• Published in: Advanced functional materials Vol. 27; no. 14
• Main Authors: Wang, Junyong, Luo, Xin, Li, Shisheng, Verzhbitskiy, Ivan, Zhao, Weijie, Wang, Shunfeng, Quek, Su Ying, Eda, Goki
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 11.04.2017
• Subjects: anisotropy; Chains; Charge transport; Crystal structure; Density functional theory; Distortion; Electron diffraction; Flakes; Incident light; Materials science; metal–metal chains; Nondestructive testing; Orientation; Polarization; Raman spectroscopy; Spectroscopy; Spectrum analysis; Topology; Transport properties; T′‐MoTe2
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201604799

Distorted octahedral T′ phase of MoTe2 has recently attracted significant interest due to its predicted topological states and novel charge transport properties. Here, we report a nondestructive method for determining the crystal orientation of few‐layer T′‐MoTe2 flakes by polarized Raman spectroscopy. The experimentally observed Raman modes are assigned to eigenmodes of vibrations predicted by density functional theory calculations. Polarized Raman measurements reveal four distinct types of angle‐dependent intensity variations. From group theory, it can be deduced that the intensity of the Bg mode reaches a maximum in the x¯(yz)x configuration when the polarization vector of the incident light is either parallel or orthogonal to the metal–metal zigzag chain direction. The intensity variation of the Bg mode cannot be used to unambiguously determine the crystal orientation. Using electron diffraction analysis, it is demonstrated that the intensity of the Ag mode at around 162 cm−1 reaches a maximum when the polarization vector of the incident light is parallel to the metal–metal chain direction in the x¯(yy)x configuration. Furthermore, a simple method is proposed for identifying crystal orientation in nonpolarized Raman spectroscopy. In‐plane anisotropy of thin‐layer semimetallic T′‐MoTe2 is investigated by angle‐resolved Raman spectroscopy. Density functional theory calculations and group theory analysis reveal four types of distinct angular dependence for Ag and Bg modes. In conjunction with electron diffraction analysis, a simple method for determining the crystal orientation is developed.