Tungsten ditelluride (WTe2) is a layered material with the Td structure which has a distorted orthorhombic phase. It has attracted interest owing to large, non-saturating magnetoresistance which can be applied for information storage [1, 2]. The large...
Tungsten ditelluride (WTe2) is a layered material with the Td structure which has a distorted orthorhombic phase. It has attracted interest owing to large, non-saturating magnetoresistance which can be applied for information storage [1, 2]. The large magnetoresistance is related with its Td structure. Therefore, understanding the lattice dynamics is an important key to the study of WTe2 [3]. Raman scattering measurements on WTe2 have been reported, but the incident polarization dependence and the low frequency part of the Raman spectrum have not been studied yet.
We measured the Raman spectra of few-layer WTe2 in the low frequency region in vacuum because WTe2 could be degraded in the air. The Raman spectrum of WTe2 with the Td structure shows strong dependence on the incident laser polarization. We also assigned the phonon mode of each peak by comparing both the incident and the analyzer polarization dependence of the Raman spectrum. We discovered new peaks which have not been observed before. Polarized Raman spectroscopy can also be used to determine the crystallographic orientation of WTe2. We also measured the thickness dependence of the Raman spectra of few-layer WTe2. The number of layers of WTe2 can be determined by the Raman peak position difference between the ~80 cm̶1 and ~110 cm̶1 peaks.