Tuning of Optical Behavior in Monolayer and Bilayer Molybdenum Disulfide Using Hydrostatic Pressure
C. B. Li, Yaoyao Liu, Yaoyao Liu, Qishuo Yang, Qunfei Zheng, Zhipeng Yan, Jun Han, Junhao Lin, Shanmin Wang, J. Qi, Ying Liu, Ying Liu, Jinlong Zhu
Abstract
Researchers have shown great interest in two-dimensional crystals recently, because of their thickness-dependent electronic and optical properties. We have investigated the Raman and photoluminescence spectra of free-standing monolayer and bilayer MoS2, as a function of pressure. As the enforcement of layer interaction, an electronic and a crystal phase transition were revealed at ∼6 GPa and ∼16 GPa, respectively, in bilayer MoS2, while no phase transition in the monolayer is observed. The electronic phase transition at ∼6 GPa is supposed to be a direct interband changing to an indirect Λ-K interband transition, and the new structure shown at ∼16 GPa is not metallized and supposed to be a transformation from stacking faults due to layer sliding like 2Hc to 2Ha. The different pressure-induced features of monolayer MoS2, compared with bilayer MoS2, can help to get a better understanding about the importance of interlayer interaction on modifying the optical properties of MoS2 and other fundamental understanding of 2D materials.