Substrate-tuned dielectric screening effect on optical properties of monolayer MoSe2

Grasping the intricate mechanisms for the influences of dielectric screening from diverse substrates on the optical properties of ultra-thin two-dimensional materials is crucial for related device design. This study investigates the substrate impacts on the optical properties of monolayer MoSe2 by combining the spectroscopic ellipsometry (SE) and first-principle calculations. Featured absorption peaks of monolayer MoSe2 on substrates of quartz, silicon, and sapphire are meticulously analyzed via critical point (CP) analysis on the dielectric functions determined by SE. Results indicate that variation in substrates induces notable shifts in energy positions of the absorption peaks due to different dielectric screening effects. The study further uncovers electron transfer from silicon substrate to monolayer MoSe2, leading to alterations in the band structure. By integrating CP analysis with first-principle calculations, we gain a comprehensive understanding of the optical transitions corresponding to CPs in the monolayer MoSe2 on various substrates. This establishes that the energy shifts of CPs regulated by substrateinduced dielectric screening are highly correlated with the positions of their corresponding optical transitions in momentum space. These findings underscore the pivotal role of substrate selection in customizing the optical properties of two-dimensional materials, providing valuable insights for the design and optimization of MoSe2based photonic devices.