Katarzyna Gołasa, Magda Grzeszczyk, Maciej R. Molas, Małgorzata Zinkiewicz, Łukasz Bala, Karol Nogajewski, Marek Potemski, Andrzej Wysmołek, Adam Babiński
January 20, 2017
Temperature-dependent (5 K–300 K) Raman scattering study of A 1g /A′ 1 phonon modes in mono-layer (1L), bilayer (2L), trilayer (3L), and tetralayer (4L) MoTe 2 is reported. The temperature evolution of the modes’ intensity critically depends on the flake thickness. In particular with λ =632.8-nm light excitation, a strongly non-monotonic dependence of the A 1g mode intensity is observed in 2L MoTe 2 . The intensity decreases with decreasing temperature down to 220 K, and the A 1g mode almost completely vanishes from the Stokes scattering spectrum in the temperature range between 160 K and 220 K. The peak recovers at lower temperatures, and at T= 5 K, it becomes three times more intense that at room temperature. Similar non-monotonic intensity evolution is observed for the out-of-plane mode in 3L MoTe 2 in which tellurium atoms in all three layers vibrate in-phase. The intensity of the other out-of-plane Raman-active mode (with vibrations of tellurium atoms in the central layer shifted by 180° with respect to the vibrations in outer layers) only weakly depends on temperature. The observed quenching of the Raman scattering in 2L and 3L MoTe 2 is attributed to a destructive interference between the resonant and non-resonant contributions to the Raman scattering amplitude. The observed “antiresonance” is related to the electronic excitation at the M point of the Brillouin zone in few-layer MoTe 2 .