Phonon and exciton temperature-dependent properties of twisted MoS_2
arxiv(2024)
摘要
In the present work, Raman and photoluminescence spectroscopies were used to
study the dynamics of phonons and different excitons of MoS_2 bilayer under a
rotation of 29^∘ dependent of the temperature. The twisted bilayer
(T-2L) of MoS_2 was obtained through mechanical exfoliation, and subsequently
rotated using a dimethyl polysiloxane (PDMS) substrate and deterministic
transferred to a SiO_2 substrate. The Raman spectrum of the twisted bilayer
presents three peaks E' (386 cm^-1), A'_1 (405 cm^-1) and an
FA' peak at approximately 409 cm^-1 linked to the A'_1 mode, which is
attributed to a Moiré pattern phonon. Both modes (A'_1 and FA') are
dependent of light polarization in a way that demonstrates an effective
coupling between the layers. It was also verified through the Grüneisen
parameter, an increase in the anharmonicity of the mode in the E' plane and a
decrease the same for A'_1. In the PL measurements, the appearance of an
exciton in T-2L was verified, which generated a second shoulder measured at
≈1.58 eV attributed to an indirect transition of an I trion. The
interaction between the rotated monolayers of MoS_2 proved to be an
important parameter for possible fine-tuning of the properties of bilayer
samples.
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