The encapsulation of few-layer transition metal dichalcogenides (TMDs) in hexagonal boron nitride (h-BN) is known to improve significantly their optical and electronic properties. However, it may be expected that the h-BN encapsulation may affect also vibration properties of TMDs due to an atomically flat surface of h-BN layers. In order to study its effect on interlayer interactions in few-layer TMDs, we investigate low-energy Raman scattering spectra of bi- and trilayer MoTe2. Surprisingly, three breathing modes are observed in the Raman spectra of the structures deposited on or encapsulated in h-BN as compared to a single breathing mode for the flakes deposited on a SiO2/Si substrate. The shear mode is not affected by changing the MoTe2 environment. The emerged structure of breathing modes is ascribed to the apparent interaction between the MoTe2 layer and the bottom h-BN flake. The structure becomes visible due to a high-quality surface of the former flake. Consequently, the observed triple structure of breathing modes originates from the combination modes due to interlayer and layer-substrate interactions. Our results confirm that the h-BN encapsulation affects substantially vibration properties of layered materials.
@article{arxiv.1908.10225,
title = {Breathing modes in few-layer MoTe$_2$ activated by h-BN encapsulation},
author = {M. Grzeszczyk and M. R. Molas and M. Bartoš and K. Nogajewski and M. Potemski and A. Babiński},
journal= {arXiv preprint arXiv:1908.10225},
year = {2020}
}